xray safety manual

8/21/2019 Xray Safety Manual

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Self-Study

X-Ray Safetyfor Analytical and Industrial Settings

LEAD

LosN A T I O N A L L A B O R A T O R Y

Alamos

X-RAY COMPLIANCE LABEL

PN:___________________________

Resurvey Due:_________________ ______________ Month Year

_____________________________ ______________

X-Ray Device Control Office Rep. Date

This machine has been surveyed and found tomeet applicable radiation safety standards

and operational safety requirements.


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LA-UR-99-5083

This training course is presented with the understanding that the information and materialsprovided were developed based on specific circumstances present at the Los Alamos NationalLaboratory at the time of publication. Those circumstances may or may not be similar toconditions present at other locations represented by participants in this course. Thecourse materials and information will need to be adapted accordingly. The University of

California/Los Alamos National Laboratory will not be liable for direct or indirect damagesresulting from use of this material.

Course CoordinatorRebecca Hollis

Instructional DesignersAnn Anthony

Mike McNaughtonJ. Margo Clark

Technical AdvisorDavid LeeEditors

Susan Basquin

IllustratorsJim Mahan and Tamara TuckerCover Designer

Rosalie Ott

Course Number:12326July 2000

Document Number: ESH13-396-sb-7/00


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Contents

X-Ray Safety for Analytical and Industrial Settings i

Introduction ............................................................................... 1

Course Purpose ....................................................................... 1

Course Objectives.................................................................... 1

Regulations and Guidance....................................................... 2

ANSI Objectives ....................................................................... 3

About this Self-Study Guide...................................................... 3

Unit 1: Radiation Protection Principles................................... 4

Unit Objectives ......................................................................... 4Atoms and Ions ........................................................................ 4

Radiation.................................................................................. 5

Units of Measure ...................................................................... 6

Background Radiation.............................................................. 6

Dose Limits and Control Levels................................................ 8

Causes of Accidental Exposures.............................................. 9

ALARA ..................................................................................... 9

Self-Assessment ...................................................................... 12

Answers ................................................................................... 14

Unit 2: Production of X-Rays ................................................... 14

Unit Objectives ......................................................................... 15

Electromagnetic Radiation ....................................................... 16

X-Ray Production ..................................................................... 17

Photon Energy and Total Power .............................................. 20

Interaction with Matter .............................................................. 21

Implications of Photon Energy and Total Power....................... 22

Self-Assessment ...................................................................... 23Answers ................................................................................... 26


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Contents

X-Ray Safety for Analytical and Industrial Settings iii

Unit 3: Biological Effects.......................................................... 26

Unit Objectives ......................................................................... 27

Early History of X-Rays ............................................................ 28

Biological Effects of Radiation.................................................. 30

Factors that Determine Biological Effects................................. 31Somatic Effects ........................................................................ 33

Heritable Effects....................................................................... 37

Self-Assessment ...................................................................... 38

Answers ................................................................................... 40

Unit 4: Radiation Detection ...................................................... 40

Unit Objectives ......................................................................... 41

Radiation Surveys .................................................................... 42

Radiation Monitoring Instruments............................................. 42

Personnel Monitoring Devices.................................................. 44

Self-Assessment ...................................................................... 46

Answers ................................................................................... 48

Unit 5: Protective Measures ..................................................... 48

Unit Objectives ......................................................................... 49

Radiological Postings............................................................... 50

Labels....................................................................................... 53

Warning Devices...................................................................... 53

Shielding .................................................................................. 54Work Documents...................................................................... 56

Self-Assessment ...................................................................... 58

Answers ................................................................................... 60

Unit 6: XGDs .............................................................................. 60

Unit Objectives ......................................................................... 61

Intentional and Incidental Devices............................................ 62

Incidental XGDs ....................................................................... 63

Intentional Analytical XGDs...................................................... 63

Intentional Industrial XGDs....................................................... 65

Summary of XGDs ................................................................... 68

Self-Assessment ...................................................................... 69

Answers ................................................................................... 71


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Contents

X-Ray Safety for Analytical and Industrial Settings iii

Unit 7: Responsibilities for X-Ray Safety................................ 71

Unit Objectives ......................................................................... 72

Responsibilities ........................................................................ 73

Self-Assessment ...................................................................... 76

Answers ................................................................................... 78Lessons Learned....................................................................... 78

Scenario................................................................................... 79

Lessons Learned...................................................................... 80

References............................................................................... 81

Acronyms and Abbreviations .................................................. 82

Glossary..................................................................................... 84

References................................................................................. 96


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Introduction

X-Ray Safety for Analytical and Industrial Settings 1

Course Purpose

The purpose of this course is to increase your knowledge to enableyou to perform your job safely by adhering to proper radiationprotection practices while working with or around x-ray-generatingdevices (XGDs). This course will inform you about the policies andprocedures you should follow to reduce the risk of exposure to theionizing radiation produced by XGDs.

Other hazards associated with the use of some x-ray machinessuch as electrical, mechanical, laser light, and explosives are notaddressed in this course because they are specific to particularmachines and procedures. Neither does this course addressoperating procedures for specific installations. You will receivetraining on the specific operating procedures at your work site.

Course Objectives

Upon completion of this course, you will be able to understand

what x-rays are and how they are generated;

the biological effects of x-rays;

how x-rays are detected;

the measures that protect you from x-rays;

the regulations and requirements governing XGDs; and

the responsibilities of the XGD Control Office, operating groups,x-ray-device custodians, and x-ray-device operators.


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Introduction


Regulations and Guidance

The prime compliance document for occupational radiationprotection at Department of Energy (DOE) sites is Title 10 of the

Code of Federal Regulations, 10 CFR 835. The documentedRadiation Protection Program provides detailed guidance on thebest practices currently available in the area of radiological control.

At Los Alamos National Laboratory (LANL), 10 CFR 835 drives theRadiation Protection Program (RPP).

The American National Standards Institute (ANSI) details radiationsafety recommendations for XGDs in two standards, one onanalytical (x-ray diffraction and fluorescence) x-ray equipment andanother industrial (nonmedical) x-ray installations. Radiation safetyguidance/instructions for radiographers may also be found in 10CFR 19.12 and 10 CFR 34, Subpart B.

At LANL, the protection program for individuals working with oraround XGDs is implemented through the LaboratoryImplementation Requirement (LIR) 402-721-01,X-Ray-GeneratingDevice/Facilities, which incorporates the relevant requirementsfrom the following ANSI standards:

ANSI N43.2 (R1989), Radiation Safety for X-Ray Diffraction andFluorescence Analysis Equipment;and

ANSI N43.3 (1993),American National Standard for GeneralRadiation SafetyInstallations Using Non-Medical X-Ray andSealed Gamma-Ray Sources, Energies up to 10 MeV.

Thus, the information presented in this course is based on theradiation safety guidelines for XGDs/facilities contained in ANSIN43.2 and N43.3 and in LIR402-721-01.0.


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Introduction


ANSI Objectives

The main objectives of ANSI N43.2 and ANSI N43.3 are to keepworker exposure to ionizing radiation at levels that are as low as

reasonably achievable(ALARA) and to ensure that no workerreceives greater than the maximum permissible dose equivalent.These objectives may be achieved through the following methods:

using firm management controls,

using hazard control plans (HCPs) and radiological work permits(RWPs),

maintaining equipment appropriately,

employing a comprehensive maintenance and surveillanceprogram,

using adequate shielding,

maximizing distance from the source, and

minimizing the time duration of x-ray production.

About this Self-Study Guide

In this Guide

This self-study guide contains seven learning modules, followed bylessons learned, a list of acronyms and abbreviations, a glossary,and references. The learning modules contain self-assessments to

review the material covered.

At the end of this study guide is a link to a final quiz. A score of80% on the quiz is required for course credit.


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Unit 1: Radiation Protection Principles


Unit Objectives

Major Objective

Upon completion of this unit, you will understand basic radiationprotection principles essential to the safe operation of XGDs.

Enabling Objectives (EOs)

Using the self-assessment, you will be able to identify

EO1 the structure of atoms and ions,

EO2 the definition of ionizing radiation,

EO3 sources of natural and manmade background radiation,

EO4 DOE and LANL dose limits,

EO5 the ALARA policy, and

EO6 three basic methods for reducing external exposure.

Atoms and Ions

The atom, the basic unit of matter, is made up of three primaryparticles: protons, neutrons, and electrons. Protons and neutronsare found in the nucleus of the atom; electrons are found orbitingthe nucleus. Protons have a positive charge; neutrons are neutral;electrons have a negative charge. Electrons determine how theatom chemically interacts with other atoms to form molecules.

An atom usually has a number of electrons equal to the numberof protons in its nucleus so that the atom is electrically neutral.

A charged atom, called an ion,can have a positive or negativecharge, depending on the number of protons and electrons. An ionis formed when an incoming electromagnetic wave or an incomingparticle interacts with an orbiting electron and causes it to beejected from its orbit, a process called ionization.


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Radiation

For radiation protection purposes, ionization is important because itaffects chemical and biological processes and allows the detectionof radiation.

Radiation is the transfer of energy in the form of particles or wavesthrough open space. Radiation with enough energy to causeionization is referred to as ionizing radiation.Radiation that lacksthe energy to cause ionization is referred to as nonionizingradiation.

Ionizing radiation takes the form of alpha, beta, or neutron particlesor gamma or x-ray photons.

AlphaParticle

NeutronParticle

BetaParticle

GammaRay

X-Ray

Figure 1. Ionizing Radiation

X-rays are a form of electromagnetic radiation and are very similarto gamma rays. They differ in their point of origin. Gamma raysoriginate from within the atomic nucleus, whereas x-rays originateoutside the nucleus. From a radiation safety standpoint, however,both gamma rays and x-rays produce the same biological effects;hence gamma rays and x-rays are commonly grouped together asone type of radiation.


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Units of Measure

Ionizing radiation is measured in the following units:

roentgen (R), the measure of exposureto radiation, defined by

the ionization caused by x-rays in air; rad, the radiation absorbed doseor energy absorbed per unit

mass of a specified absorber; and

rem, the roentgen equivalent manor dose equivalent.

In that 1 R of exposure delivers approximately 0.95 rads ofabsorbed dose to muscle tissue, for radiation safety purposes theapproximation is often made that 1 R = 1 rad = 1 rem.

Note:For a more detailed discussion of R, rad, and rem, refer toUnit 4 inAccelerator Safety (Self-Study)and in Sealed Source

Safety (Self-Study).

Background Radiation

Background radiation, to which everyone is exposed, comes fromboth natural and manmade sources. The most common sources ofnatural background radiation are cosmic, terrestrial, internal, andradon. The most common sources of manmade backgroundradiation are medical procedures and consumer products.

The average background dose to the general population from both

natural and manmade sources is about 360 mrem per year. InLos Alamos, background dose averages about 400 mrem per yearbecause of higher altitude.

Natural Sources

Manmade Sources

Radon 200 mrem

Cosmic 28 mrem

Terrestrial 28 mrem

Internal 40 mrem

Medical X-Rays39 mrem

Nuclear Medicine14 mrem

Consumer Products10 mrem

Other2 mrem

Figure 2. Average Annual Background Dose


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Background Radiationcontinued

Naturally occurring sources include an average of about 200 mremper year from radon and its decay products, about 40 mrem peryear from internal emitters such as potassium-40, about 28 mremper year from cosmic rays, and about 28 mrem per year fromterrestrial sources such as naturally occurring uranium and thorium.

Manmade sources of ionizing radiation exposure include anaverage of about 10 mrem per year from consumer products suchas building materials and about 53 mrem per year from medicalprocedures such as diagnostic x-ray and nuclear machineprocedures. Note that the dose from a chest x-ray procedure (twoviews) is approximately 20-26 mrem. The average dose from amammographic procedure (two views per breast) is 1.4 mrem,which totals 2.8 mrem for both breasts. The average dose for a

dental x-ray (one bitewing) is 1.5 mrem per bitewing. However, afull-mouth dental x-ray exam may include 21 views, which totalsapproximately 32 mrem for the full mouth exam. Because thesedoses are only to portions of the body, the effective dose equivalentto the whole body is a fraction of these values.


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Dose Limits and Control Levels

Limits on occupational doses are based on data on the biologicaleffects of exposure to ionizing radiation and guidance from theInternational Commission on Radiological Protection, the NationalCouncil on Radiation Protection, and the Environmental Protection

Agency. The limits are well below the doses at which anysymptoms of biological effects appear.

The following table lists DOE dose limits for occupational doses.

DOE Dose Limits

Part of the Body Dose Limits (in rem)

whole body 5 rem/year

extremity 50 rem/year

skin 50 rem/year

internal organ 50 rem/year

lens of the eye 15 rem/year

embryo/fetus 0.5 rem/term of pregnancy

minors and the public 0.1 rem/year

DOE facilities are designed and operated to reduce workers dose

equivalents as far below the occupational limits as reasonable. AtLANL, your lifetime dose limit in rem must not exceed your age inyears. For example, a 40-year-old worker is limited to a total doseof 40 rem. The average exposure for x-ray workers is typicallybetween 0 and 100 mrem per year above natural backgroundexposure.


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Causes of Accidental Exposures

Although most x-ray workers do not receive any measurableradiation above background, accidents related to XGDs haveoccurred when proper work procedures have not been followed.Failure to follow proper procedures has been the result of

rushing to complete a job,

fatigue,

illness,

personal problems,

lack of communication, or

complacency.

Every year about one x-ray incident per hundred x-ray units occurs

nationwide. Approximately one-third of these incidents result ininjury to a person. The accident rate at DOE laboratories is lowerthan the national average.

ALARA

Because the effects of chronic exposure to low levels of ionizingradiation are not precisely known, there is an assumed long-termrisk of developing some forms of cancer associated with anyradiation dose. ALARA policy is to keep radiation dose as low asreasonably achievable,considering economic and social

constraints.

The goal of the ALARA program is to keep radiation dose ALARA,that is, as far below the occupational dose limits and administrativecontrol levels as is reasonably achievable so that there is noradiation exposure without commensurate benefit based on soundeconomic principles. The success of the ALARA program is directlylinked to a clear understanding and following of the policies andprocedures for the protection of workers. Keeping radiation doseequivalent ALARA is the responsibility of each worker.


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ALARAcontinued

Linear Nonthreshold (LNT) Dose-Effect Hypothesis

The ALARA policy is based philosophically on the linear,nonthreshold (LNT) dose-effect hypothesis, which predicts the riskof developing cancer associated with long-term radiation exposurein the workplace. The LNT hypothesis assumes that the high dosesof ionizing radiation associated with observed injurious effects inhumans may be used to predict the effects of low doses.

According to the LNT hypothesis, any dose of ionizing radiation, nomatter how small, has some sort of injurious effect. Furthermore, itregards each increment of dose as having the same biologicaldamage-producing potential regardless of dose rate, and it regardsevery increment of dose as irreversible, permanent, andcumulative.

However, there is some controversy associated with the LNThypothesis. Many safety professionals maintain that no injuriouseffects of low-dose and low-dose rate ionizing radiation have everbeen documented to occur in human populations, which is counterto the hypothesis.

Furthermore, they maintain that scientific evidence confirms thatthere are probably no injurious effects from low-dose and low-doserate ionizing radiation at even many times the dose and dose rates

of natural background radiation. They suggest that the doses anddose rates from natural background radiation are comparable to thedoses and dose rates experienced by most radiological workers inthe workplace and by members of the public.

Despite the controversy in the safety professional community, theDOE has endorsed the LNT hypothesis as a prudent andconservative approach for the protection of workers and the public.The ALARA policy is mandated by law and requires that exposurebe kept as low as possible.


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ALARAcontinued

Reducing External Exposure

Three basic ways to reduce external exposure to radiation are to minimize time,

maximize distance, and

use shielding.

3

MinimizeTime

MaximizeDistance

UseShielding

12

6

9 3

12

6

9 3

In Out

Figure 3. Methods for Reducing External Exposure

Minimize time near a source of radiation by planning ahead.Maximize distance by moving away from the source of radiationwhenever possible. Exposure from x-ray sources is inverselyproportional to the square of the distance (inverse-square law),that is, when the distance is doubled, the exposure is reducedby one-fourth. Use shielding appropriate for the type of radiation.Lead, concrete, and steel are effective in shielding against x-raysand gamma ray sources.


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Self-Assessment

1. Ionizing radiation can remove electrons from a neutral atom toform (EO1)

a. neutrons

b. protons

c. electrons

d. ions

2. Radiation is (EO2)

a. radioactive decay of electrons

b. neutral atoms in a material

c. energy transferred through space

d. neutral ions in an unwanted place3. All but one of the following are examples of ionizing radiation,

except(EO2)

a. alpha

b. beta

c. atom

d. x-ray

4. Radiation to which everyone is exposed is called (EO3)

a. alphab. background

c. cathode ray

d. occupational

5. Background radiation averages about (EO3)

a. 360 mrem per hour

b. 360 mrem per year

c. 360 rem per hour

d. 360 rem per year

6. The DOE dose limit for the whole body is (EO4)

a. 5 mrem per hour

b. 5 rem per hour

c. 5 mrem per year

d. 5 rem per year


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Self-Assessmentcontinued

7. At LANL a 50-year-old worker is limited to an accumulatedlifetime dose of (EO4)

a. 5 remb. 20 rem

c. 40 rem

d. 50 rem

8. The dose limit for an embryo or fetus is (EO4)

a. the same as for the whole body of an adult

b. more than for the whole body of an adult

c. less than for the whole body of an adult

d. not specified

9. The policy of keeping radiation dose ALARA is followedbecause the effects of low levels of radiation are (EO5)

a. not precisely known

b. nonexistent

c. unacceptably hazardous

d. as large as regulations allow

10. One of the methods of reducing exposure to radiation is to

minimize (EO6)a. distance

b. time

c. shielding

d. speed

11. If you move away from a point source of x-rays until you arefour times as far away, your exposure will be (EO6)

a. the same

b. one-half

c. one-fourth

d. one-sixteenth


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Answers

1. d

2. c

3. c4. b

5. b

6. d

7. d

8. c

9. a

10. b

11. d


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Unit 2: Production of X-Rays


Unit Objectives

Major Objective

Upon completion of this unit, you will understand what x-rays areand how they are produced so that you will be able to work aroundthem safely.



EO1 the types of electromagnetic radiation;

EO2 the difference between x-rays and gamma rays;

EO3 how x-rays are produced;

EO4 bremsstrahlung and characteristic x-rays;

EO5 the difference between photon energy and total power;

EO6 the effects of voltage, current, and filtration on x-rays;

EO7 how x-rays interact with matter; and

EO8 how energy relates to radiation dose.


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Electromagnetic Radiation

X-rays are a type of electromagnetic radiation. Other types ofelectromagnetic radiation are radio waves, microwaves, infrared,light, ultraviolet, and gamma rays. The types of radiation aredistinguished by the amount of energy carried by the individualphotons.

All electromagnetic radiation consists of photons, which areindividual packets of energy. One is not usually aware of theseindividual packets because they are so numerous. For example,a household light bulb emits about 1021photons per second.

The energy carried by individual photons, which is measured inelectron volts (eV), is related to the frequency of the radiation.Different types of electromagnetic radiation and their typical photon

energy are listed in the following table.

Electromagnetic Radiation

Type of Radiation Typical Photon Energy

radio wave 1 eV

microwave 1 meV

infrared 1 eV

red light 2 eV

violet light 3 eV

ultraviolet 4 eV

x-ray 100 keV

gamma ray 1 MeV


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Electromagnetic Radiationcontinued

X-Rays and Gamma Rays

X-rays are similar to gamma rays in their ability to ionize atoms.Other types of electromagnetic radiation are nonionizing. It takes5 eV of photon energy to ionize a carbon atom, so one x-ray photon(typically 100 keV) can ionize thousands of atoms.

As discussed in Unit 1, the distinction between x-rays and gammarays is their origin and method of production. Gamma rays originatefrom within the nucleus; x-rays originate outside the nucleus.

In addition, gamma photons often have more energy than x-rayphotons. For example, diagnostic x-rays are about 40 keV, whereasgammas from cobalt-60 are about 1 MeV. However, there are manyexceptions. At LANL, for example, gammas from plutonium areless than 60 keV, whereas x-rays from the pulsed high-energyradiographic machine emitting x-rays (PHERMEX) are about10 MeV.

X-Ray Production

X-rays are produced when charged particles, usually electrons,are accelerated by an electrical voltage (potential difference).Whenever a high voltage, a vacuum, and a source of electrons are

present in any scientific device, x-rays can be produced. This iswhy many devices that use high voltages produce incidentalx-rays,i.e., x-rays produced during normal operation of the device that arean unwanted byproduct of the devices normal function.Televisions, computer monitors, scanning electron microscopes,and many other devices at LANL produce incidental x-rays.


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X-Ray Productioncontinued

Most XGDs emit electrons from a cathode, accelerate them with avoltage within a vacuum, and allow them to hit an anode, whichemits x-ray photons.

+

CopperAnode

TungstenTarget

Electrons

HeatedTungstenFilament

EvacuatedEnvelope

Figure 4. X-Ray Tube

While x-rays are extremely useful in areas ranging from basicresearch to trace element analysis to radiography, the actualproduction of x-rays is rather difficult and very inefficient. More than99% of the kinetic energy of electrons bombarding a particulartarget material results only in the production of heat. Indeed, heatbuildup in the x-ray production target is the key limiting factor in the

design of intentional x-ray producing devices.

Bremsstrahlung

When high-speed electrons from a cathode bombard an anodetarget material, some of the negatively charged electrons are ableto get through the target atoms otherwise repelling electron clouddue to their high velocity and close enough to the positivelycharged nucleus. This proximity causes the electrons to undergo achange in momentum due to the strongly attractive force of thetarget nuclei. The electrons that are able to penetrate near thetarget material nuclei are braked, or decelerated, to varyingdegrees depending on how closely they approach the target nuclei.The Coulomb force field of the target nuclei causes up to 100% ofthe kinetic energy of the bombarding electrons to be converted to x-ray photon energy. X-ray photons are thus produced by manyindividual energies over a wide energy spectrum depending uponthe degree of braking that the original bombarding electrons


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X-Ray Productioncontinued

experienced in the Coulomb force field of the target nuclei. Theprocess of producing x-rays in this manner is calledBremsstrahlung x-ray production after the German word forbraking radiation. Bremsstrahlung production in a given targetmaterial varies directly as the square of the target materials atomicnumber (Z) and inversely as its atomic weight (A). Thus,

Bremsstrahlung Z

2

A

Bremsstrahlung is most effectively produced when small chargedparticles bombard atoms of high Z number such as tungsten. In

theory, however, bremsstrahlung can be produced by bombardingtargets of low Z number, e.g., hydrogen with high-velocity electrons.For example, small amounts of bremsstrahlung have beenproduced by bombarding hydrogen atoms with high-velocityelectrons.

Characteristic X-Rays

High-speed electrons traveling a vacuum may impinge upon atarget material such that the negatively charged high-velocityelectrons liberate electrons from the target atom. The target atomelectron vacancy thus created is filled by other electrons within theatom moving to fill the vacancy. The transition of electrons betweenenergy states results in the emission of x-rays that arecharacteristic of the target atom identity and whose energycorresponds to the difference between the initial and final electronenergy state. For example, when bombarded by high-velocityelectrons in a vacuum, copper emits characteristic x-rays of 9.04keV. In contrast, tungsten emits characteristic x-rays of 58.87 keV;molybdenum, 17.44 keV; cobalt, 6.93 keV; iron, 6.40 keV; andchromium, 5.41 keV.

Summary

X-rays can be produced by either radiative interaction as thebombarding electrons are braked by the Coulomb force field of thetarget nuclei (bremsstrahlung x-ray production) or by collisioninteractions with atomic electrons of the target material(characteristic x-ray emission).


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Photon Energy and Total Power

For radiation protection purposes, it is important to distinguishbetween the energy of individual photons in an x-ray beam and thetotal energy of all the photons in the beam. It is also important todistinguish between average power and peak power in a pulsedXGD.

Typically, the individual photon energy is given in electron volts(eV), whereas the total power of a beam is given in watts (W).Consider an analogous example from visible light: a 100-W red lightemits more total power than a 10-W blue light; however, blue lightphotons have more energy than red light photons.

The photon energy may be varied either by changing the voltage orby using filters that are analogous to the colored filters used in

photography. Changing the current may vary the number ofphotons emitted.

Voltage

The photon energy produced by an XGD depends on the voltage,which is measured in volts (V). A voltage of 10 kV will produce upto 10-keV x-ray photons. Most of the x-ray photons produced by agiven maximum electron acceleration potential will beapproximately one-third of the maximum electron accelerationpotential. For example, a 120-kV-peak (kVp) diagnostic XGD

produces x-ray photons most of which will have energies around 40keV. Many XGDs have meters to measure voltage. Whenever thevoltage is on, a device can produce x-rays, even if the current is toolow to read.

Current

The total number of photons produced by an XGD depends on thecurrent, which is measured in amperes, or amps (A). The current iscontrolled by increasing or decreasing the number of electronsemitted from the cathode. The higher the electron current, the morex-ray photons are emitted from the anode. Many XGDs havemeters to measure the x-ray current produced. The x-ray currentfrom many intentional x-ray producing devices is on the order ofmilliamps (mA).


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Photon Energy and Total Powercontinued

Determining Total Power

Total power equals voltage multiplied by current (W = V x A). Forexample, a 10-kV device with a current of 1 mA produces 10 W ofpower.

Interaction with Matter

Scattering

When x-rays pass through any material, some will be transmitted,some will be absorbed, and some will scatter. The proportionsdepend on the photon energy and the type of material.

X-rays can scatter off a target to the surrounding area, off a walland into an adjacent room, and over and around shielding. Acommon mistake is to install thick shielding walls around an x-raysource but ignore the need for a roof, based on the assumptionthat x-rays travel in a straight line. The x-rays that scatter over andaround shielding walls are known as skyshine.

Source Shield

X

X

X

Air Scatter (Skyshine)

Figure 5. Skyshine

Shielding

High-energy x-ray photons are more penetrating than low-energyphotons. This makes high-energy photons more difficult to shield.Thicker shielding may be required, or if the shielding thickness isfixed, high-energy photons will penetrate more often than low-energy photons. Varying thicknesses of lead, concrete, and steelare most effective in shielding against x-rays.


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Interaction with Mattercontinued

Filtration

High- and low-energy photons are sometimes referred to as hardand softx-rays, respectively. Because hard x-rays are morepenetrating, they are more desirable for radiography (producing aphotograph of the interior of the body or a piece of apparatus). Softx-rays are less useful for radiography because they are absorbednear the surface. Filters typically of aluminum, copper, or lead areused to harden the x-ray beams from low, medium, and high-energy x-ray machines, respectively.

Implications of Photon Energy and Total Power

High-energy photons penetrate deeply into and through the body,resulting in the deposition of dose to internal organs. Low-energyphotons are absorbed in the top layers of tissue, resulting in thedeposition of dose mostly to the skin.

The greater the number of photons, and therefore the greater thetotal energy, the more damage is caused to whatever part of thebody in which the photons deposit energy. This is measured inunits of rador rem, defined as the result of 0.01 W for 1 second in 1kilogram of human tissue (0.01 W-sec/kg = 1 rad = 1 rem, for x-rays). Note that a concentrated beam of x-rays could deposit all of

its energy in much less than 1 kilogram of tissue. For example, 0.01W for 1 second in1 gram would result in 1,000 rem of damage.

A 100-keV photon is more hazardous than a 10-keV photon, and10 W are more hazardous than 1 W, but the precise hazardsdepend on what part of the body is exposed, how far the x-rayphoton penetrates, and other factors discussed in Unit 3.


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Self-Assessment

1. X-rays are similar to other types of electromagnetic radiationbecause all consist of (EO1)

a. electronsb. photons

c. protons

d. neutrons

2. Which of the following types of radiation is the most similar tox-rays? (EO2)

a. microwaves

b. infrared

c. ultraviolet

d. gamma rays

3. In an XGD, x-rays are emitted from the (EO3)

a. anode

b. vacuum

c. cathode

d. diode

4. Production of x-rays by bremsstrahlung is generally increased

when charged particles with _____ mass hit an anode with_____ atomic weight. (EO4)

a. small, low

b. large, low

c. small, high

d. large, high


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5. In an XGD, photon energy depends on _____ and the numberof photons produced depends on _____. (EO5)

a. current, voltageb. current, filtration

c. voltage, current

d. voltage, filtration

6. Which of the following best describes the safety situation whenthe voltage meter on an XGD is on and the current meter readszero, assuming the meter has not malfunctioned? (EO6)

a. there are no x-rays

b. there may be a small current, too small to read, producing

some x-rays

c. the x-ray hazard is unaffected by the current or voltage

d. the x-ray energy increases as the current and voltagedecrease

7. When filtration is used in an XGD to hardenthe beam, theremaining photons are (EO6)

a. low-energy, more penetrating

b. low-energy, less penetrating

c. high-energy, more penetrating

d. high-energy, less penetrating

8. When x-rays interact with matter, will they be absorbed,transmitted, or scattered? (EO7)

a. absorbed

b. transmitted

c. scattered

d. some of each

9. Scattering of x-rays by air may result in increased (EO7)a. skyshine

b. power

c. current

d. voltage


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10. When comparing 10-keV with 100-keV x-rays, the shieldingrequired is likely to be (EO7)

a. greater for 10 keVb. greater for 100 keV

c. the same for each

d. impossible for 10 keV and easy for 100 keV

11. The dose received from x-rays is a measure of (EO8)

a. the energy absorbed per unit mass of absorber

b. the power absorbed per unit photon

c. the photons transmitted per unit weight

d. the electron volts scattered per unit watt


31/107



Answers

1. b

2. d

3. a4. c

5. c

6. b

7. c

8. d

9. a

10. b

11. a


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Unit 3: Biological Effects


Unit Objectives

Major Objective

Upon completion of this unit, you will understand the biologicaleffects of x-rays and the importance of protective measures forworking with or around x-rays.



EO1 the early history of x-rays and the consequences of workingwith or around x-rays without protective measures,

EO2 factors that determine the biological effects of x-ray exposure,

EO3 the differences between thermal and x-ray burns,

EO4 the signs and symptoms of an acute exposure to x-rays,

EO5 the effects of chronic exposure to x-rays, and

EO6 the difference between somatic and heritable effects.


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Early History of X-Rays

Discovery of X-Rays

X-rays were discovered by German scientist Wilhelm Roentgen.In early November 1895, Roentgen was investigating high-voltageelectricity and noticed that a nearby phosphor glowed in the darkwhenever he switched on his apparatus. He quickly demonstratedthat these unknown x rays, as he called them, traveled in straightlines, penetrated some materials, and were stopped by densermaterials. He continued experiments with these x rays andeventually produced an x-ray picture of his wifes hand showingthe bones and her wedding ring. In early January 1896, Roentgenmailed copies of this picture along with his report to fellowscientists.

By February 1896, the first diagnostic x-ray in the United Stateswas taken, followed quickly by the first x-ray picture of a fetus inutero. By March, the first dental x-rays were taken. In that samemonth, French scientist Henri Becquerel was looking forfluorescence effects from the sun, using uranium on a photographicplate. The weather turned cloudy so he put the uranium and thephotographic plate into a drawer. When he developed the plates afew weeks later, the plates had been clouded by their proximity touranium. He realized he had made a new discovery. His student,Marie Curie, named it radioactivity.

Figure 6. Roentgens First X-Ray


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Early History of X-Rayscontinued

Discovery Of Harmful Effects

Because virtually no protective measures were used in those earlydays, people soon learned about the harmful effects of x-rays.X-ray workers were exposed to very large doses of radiation, andskin damage from that exposure was observed and documentedearly in 1896. In March of that year, Thomas Edison reported eyeinjuries from working with x-rays. By June, experimenters werebeing cautioned not to get too close to x-ray tubes. By the end ofthat year, reports were being circulated about cases of hair loss,reddened skin, skin sloughing off, and lesions. Some x-ray workerslost fingers, and some eventually contracted cancer. By the early1900s, the potential carcinogenic effect of x-ray exposure in

humans had been reported.

Since that time, more than a billion dollars have been spent in thiscountry alone on radiation effects research. The biological effectsof exposures to radiation have been investigated. National andinternational agencies have formed to aid in the standardization ofx-ray use to ensure safer practices.


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Biological Effects of Radiation

X-rays can penetrate deeply into the human body, strip electronsfrom orbit, and thereby break or modify chemical bonds withincritical biological molecules that make up the cells. This processcan cause cell injury and even cell death, depending on the doseand dose rate of the exposure.

In some cases, altered cells are able to repair the damage. In othercases, the effects are passed to daughter cells through cell divisionand after several divisions can result in a group of cells with alteredcharacteristics. The division of these cells may be the first step intumor or cancer development.If enough cells in a body organ areinjured or altered, the functioning of the organ can be impaired.

Cell Nucleus

Cell

Chromosome

Radiation

Figure 7. Effects of Radiation on a Cell


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Factors that Determine Biological Effects

Several factors contribute to the biological effects of x-rayexposure, including

dose rate, total dose received,

energy of the radiation,

area of the body exposed,

individual sensitivity, and

cell sensitivity.

Dose Rate

Depending on the period of time over which it is received, a doseis commonly categorized as acute or chronic. An acutedose isreceived in a short period (seconds to days); a chronic dose isreceived over a long period (months to years).

For the same total dose, an acute dose is more damaging than achronic dose because the cell does not have adequate time torepair all the damage between hits. With an acute dose, a cellmay receive multiple hits, not all of which may be repaired, thusresulting in residual enduring cell damage.

Total Dose Received

The higher the total amount of radiation received, the greater theeffects observed. The effects of an acute dose of more than 100rem are easily observed. However, the signs and symptoms of anacute dose of amounts less than 10 to 25 rem are not easilyobserved. Currently effects below 10 rem exposure cannot bereliably quantified.

The effects of a chronic dose are also difficult to observe. Althoughchronic effects have not been observed directly, it is assumedunder the ALARA philosophy that the higher the total dose, the

greater the risk of contracting cancer or other long-term effects.


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Factors that Determine Biological Effectscontinued

Energy of the Radiation

The energy of x-rays can range from less than 1 keV up to morethan 10 MeV, but are typically 40 to 100 keV. The higher the energyof the x-ray, the greater the penetration into body tissue (deepdose) and the higher the probability of damage to internal organs,bone, or bone marrow, the site of blood-forming tissue. Lowerenergy x-rays are absorbed in the first few millimeters of tissue(shallow dose) and can cause damage to the skin but less damageto the internal organs of the body.

Area of the Body Exposed

Just as a burn to the majority of the body is more damaging than aburn confined to a small area, similarly a radiation dose to thewhole body, which contains the vital organs and blood-formingtissue, is much more damaging than a dose delivered only to ahand. In addition, the larger the area exposed, the more difficult it isfor the body to repair the damage.

Individual Sensitivity

Some individuals are more sensitive to radiation than others. Age,gender, lifestyle, and overall health can have an effect on how the

body responds to radiation dose.

Cell Sensitivity

Some cells are more sensitive to radiation than others. Cells thatare more sensitive to radiation are radiosensitive;cells that areless sensitive to radiation areradioresistant.

Cells that are nonspecialized, such as sperm and ovum cells, orcells that are actively dividing, such as hair follicle andgastrointestinal cells, are the most radiosensitive. Cells that are

specialized (mature) or cells that are less-actively dividing, such asbone, muscle, or brain cells, are more radioresistant.


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Somatic Effects

Somatic effects are biological effects that occur in the individualexposed to radiation. Somatic effects may result from acute orchronic doses of radiation.

Early Effects

The most common injury associated with the operation ofanalytical x-ray equipment occurs when a part of the body, usuallya hand or finger, is exposed to the primary x-ray beam. Both x-raydiffraction and fluorescence analysis equipment generate high-intensity x-rays that can cause severe and permanent injury if anypart of the body is exposed to the primary beam.

The most common injury associated with the operation of industrialx-ray equipment occurs when an operator is exposed to the intenseprimary x-ray beam for even a short time. LANL has someintentional x-ray devices that produce more than 1000 rem/minuteone meter away from the x-ray production target. Thus, strictengineered access controls must be emplaced to prevent theoperator from ever placing himself/herself in the primary x-raybeam area when the machine is energized.

These types of injuries are sometimes referred to asradiationburns.

X-Ray Burns versus Thermal Burns

Most nerve endings are near the surface of the skin, so they giveimmediate warning of a surface burn such as you might receivefrom touching a high-temperature object. In contrast, high-energyx-rays readily penetrate the outer layer of skin that contains most ofthe nerve endings, so you may not feel an x-ray burn until thedamage has been done.

X-ray burns do not harm the outer, mature, nondividing skin layers.Rather, the x-rays penetrate to the deeper, basal skin layer,

damaging or killing the rapidly dividing germinal cells that weredestined to replace the outer layers that slough off. Following thisdamage, the outer cells that are naturally sloughed off are notreplaced. Lack of a fully viable basal layer of cells means that x-rayburns are slow to heal, and in some cases, may never heal.Frequently, such burns require skin grafts. In some cases, severex-ray burns have resulted in gangrene and amputation of a finger.


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Somatic Effectscontinued

The important variable is the energy of the radiation. Heat radiationis infrared, typically 1 eV; sunburn is caused by ultraviolet radiation,typically 4 eV; x-rays are typically 10 to 100 keV.

Signs and Symptoms of Exposure to X-Rays

~500 rem.An acute dose of about 500 rem to a part of the bodycauses a radiation burn equivalent to a first-degree thermal burn ormild sunburn. Typically, there is no immediate pain, but a sensationof warmth or itching occurs within about a day after exposure. Areddening or inflammation of the affected area usually appearswithin a day and fades after a few more days. The reddening mayreappear as late as two to three weeks after the exposure. A dryscaling or peeling of the irradiated portion of the skin is likely tofollow.

If you have been working with or around an XGD and you notice anunexplained reddening of your skin, notify your supervisor and theOccupational Medicine Group (ESH-2). Aside from avoiding furtherinjury and guarding against infection, further medical treatment willprobably not be required and recovery should be fairly complete.

An acute dose of about 600-900 rem to the lens of the eye causesa cataract to begin to form.

>1,000 rem.An acute dose of greater than 1,000 rem to a part ofthe body causes serious tissue damage similar to a second-degreethermal burn. First reddening and inflammation occurs, followed byswelling and tenderness. Blisters will form within one to threeweeks and will break open leaving raw, painful wounds that canbecome infected. Hands exposed to such a dose become stiff andfinger motion is often painful. If you develop symptoms such asthese, seek immediate medical attention to avoid infection andrelieve pain.

An even larger acute dose causes severe tissue damage similar to

a scalding or chemical burn. Intense pain and swelling occurs,sometimes within hours. For this type of radiation burn, seekimmediate medical treatment to reduce pain. The injury may notheal without surgical removal of exposed tissue and skin grafting tocover the wound. Damage to blood vessels also occurs, which canlead to gangrene and amputation.


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A typical XGD can produce such a dose in about 3 seconds. Forexample, the dose rate from an XGD with a tungsten anode and aberyllium window operating at 50 keV and 20 mA produces about900 rem per second at 7.5 cm. The dose rate can be estimatedfrom the formula

50 V I

rem/sec = ,

R2

where V is the potential in volts, I is the current in amperes, andR is the distance in centimeters.

Latent Effects

The probability of a latent effect appearing several years after anacute exposure to radiation depends on the amount of the dose.The higher the dose, the greater the risk of developing a long-termeffect. When an individual receives a large accidental dose, andthe prompt effects of that exposure have been dealt with, there stillremains a concern about latent effects years after the exposure.

Although there is no unique disease associated with exposure toradiation, the concern usually centers around the possibility of

developing cancer. If the exposure is directly to the lens of the eye,the development of cataracts is the expected latent effect.

Chronic Effects

Chronic somatic effects may not appear until several years afterexposure to radiation. Chronic effects result from doses of radiationreceived over a long period. The higher the cumulative dose, thegreater the risk of developing a chronic effect. One chronic effect iscataracts. Chronic dose to the lens of the eye can result incataracts and other optical problems if the total dose exceeds about

600 rem.


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Risk of Developing Cancer from Chronic Exposure

The risk of cancer from chronic low doses of radiation cannotbe estimated precisely because the risk is so low that it cannot bedistinguished from natural causes. Thus, estimates of the risk fromlow doses must be inferred from those developed for the effectsobserved at acute high doses.

The Fifth Committee on the Biological Effects of Ionizing Radiation(BEIR V) estimates the risk to be 0.8% for an acute dose of 10 rem.This risk estimate for high doses was developed through studies ofJapanese atomic bomb survivors, uranium miners, radium watch-dial painters, and radiotherapy patients.

Below 10 rem, the effects of chronic, low doses have not beenobserved. Therefore, using the ALARA philosophy, risk estimatesfor low doses have been inferred from high-dose data to provideprobably ultraconservative protection guidelines for worker/publicradiation exposure.

Effects of Prenatal Exposure (Teratogenic Effects)

The embryo/fetus is most sensitive to the effects of ionizingradiation during the first trimester of pregnancy when cells are

rapidly dividing and the major organs are forming. If you areplanning a pregnancy, you should seek advice from the fetalprotection specialist in Radiation Protection Services (ESH-12) andkeep your radiation dose ALARA.

If you become pregnant, you are strongly encouraged to declareyour pregnancy in writing to your supervisor, ESH-2, and ESH-12.The dose limit for a declared pregnant worker is 500 mrem duringthe term of pregnancy, with no more than 0.05 rem per month.


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Heritable Effects

Somatic Effects

Heritable Effects

Appear inexposed person

Appear in futuregenerations ofexposed person

Figure 8. Somatic vs. Heritable Effects

Heritable effects are biological effects that are inherited by childrenfrom their parents at conception. Irradiation of the reproductiveorgans can damage and alter cells that are involved in conceptionand can potentially alter heritable information passed on tooffspring.

Heritable effects have been observed in large-scale experimentswith fruit flies and mice irradiated with large doses of radiation.However, heritable effects from radiation exposure have not beenobserved in humans. The probability of heritable effects in humans

is prudently inferred from the animal data, under the ALARAphilosophy, but no heritable radiation effects have ever beenobserved in human populations.

The heritable effects of ionizing radiation do not result in biologicalconditions in the offspring that are uniquely different from theeffects that occur naturally. Extensive observations of the childrenof Japanese atomic bomb survivors have not revealed anystatistically significant heritable effects.

Note:Teratogenic (congenital) effects are not heritable effects.Teratogenic effects are not inherited; they are caused by the action

of agents such as drugs, alcohol, radiation, or infection to anunborn child in utero. Teratogenic effects occurred in children whowere irradiated in utero by the atomic bombs at Hiroshima orNagasaki.


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Self-Assessment

1. X-rays were discovered by Wilhelm Roentgen in 1895 while hewas (EO1)

a. x-raying his wifes handb. investigating fluorescence of uranium

c. experimenting with high-voltage vacuum tubes

d. visiting Thomas Edison

2. If the total accumulated dose from x-rays to human tissueremains the same, how does the dose rate affect the biologicaldamage? (EO2)

a. acute doses are generally more serious

b. chronic doses are generally more serious

c. the dose rate must exceed 5 mrem per hour to have aneffect

d. the dose rate makes no difference

3. Which of the following types of cells is most radiosensitive?(EO2)

a. skin

b. bone

c. muscle

d. gastrointestinal

4. Which of the following types of cells is most radioresistant?(EO2)

a. gastrointestinal

b. brain

c. sperm

d. ovum

5. One of the first signs of an x-ray burn to the extremities is

(EO3)a. loss of hair

b. cancer

c. nausea

d. reddening of the skin


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6. When comparing an x-ray burn with a thermal burn, an x-rayburn is likely to be _____ painful immediately, and _____painful later. (EO4)

a. less, less

b. less, more

c. more, less

d. more, more

7. Acute effects occur in a _____ period; chronic effects occurover a _____ period. (EO5)

a. long, longer

b. long, short

c. short, long

d. short, shorter

8. Chronic exposure of the eye to x-rays can result in (EO5)

a. acute effects

b. burns

c. cataracts

d. puncture

9. Somatic effects occur in the ______, heritable effects occur inthe ______ (EO6)

a. children, exposed person

b. children, body

c. exposed person, children

d. skin, hair


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Answers

1. c

2. a

3. d4. b

5. d

6. b

7. c

8. c

9. c


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Unit 4: Radiation Detection


Unit Objectives

Major Objective

Upon completion of this unit, you will understand which radiationmonitoring instruments and which personnel monitoring devices areappropriate for detecting x-rays.



EO1 the requirements for surveying XGDs,

EO2 the instruments used for x-ray detection and measurement,and

EO3 the devices used for personnel monitoring.


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Radiation Surveys

Radiation protection surveys are conducted on all new or newlyinstalled intentional XGDs by the XGD Control Office andresurveyed annually and as specified in LIR402-721-01.0. A LANLx-ray compliance label certifies that the device has been surveyedand that safe operating requirements have been met.

WARNINGDO NOT USE THIS MACHINE

It does not meet applicableradiation safety standards

and operational safety requirements

X-Ray Device ControlOffice Representative

Phone

Date PN

X-RAY COMPLIANCE LABEL

PN: ___________________________

Resurvey Due: ________________ ______________

Month Year

_____________________________ ______________

X-Ray Device Control Office Rep. Date

This machine has been surveyed and found tomeet applicable radiation safety standards

and operational safety requirements.

Figure 9. Compliance and Warning Labels

When significant safety hazards are identified, a LANL warninglabel is attached to the XGD, indicating that it must not be used.

After any necessary repairs or modifications are completed, thedevice must be resurveyed by the XGD Control Office.

Radiation Monitoring Instruments

External exposure controls used to minimize the dose equivalentto workers are based on the data taken with portable radiationmonitoring instruments during a radiation survey. An understandingof these instruments is important to ensure that the data obtainedare accurate and appropriate for the source of radiation.

Many factors can affect how well the survey measurement reflectsthe actual conditions, including

selection of the appropriate instrument based on the type and

energy of radiation and the radiation intensity; correct operation of the instrument based on the instrument

operating characteristics and limitations; and

calibration of the instrument to a known radiation field similar intype, energy, and intensity to the radiation field to be measured.


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Radiation Monitoring Instrumentscontinued

Instruments Used for X-Ray Detection and Measurement

Eb

erlin

e

CAUTION

XXXXXXXXXXXXXXXXXX

XXXXXXXXXXXXXXXXXX

XXXXXXXXXXXXXXXXXX

XXXXXXXXXXXXXXXXXX

XXXXXXXXXX

XXXX

X

XX

XX

XX

ESPEberlineSmartPortable

GM Counter Ion Chamber

Eberline

2 3 4

5

IONCHAMBER

MODELRO-3CSERIAL724

eberlin

e

OFF

5

50

ZERO

BAT3

BAT2

mR/h

Figure 10. Detection and Measurement Instruments

XGD operators often use a radiation monitoring instrument for thedetectionof x-rays, for example, to verify that the deviceis off before entry into the area. The measurementof x-rays isnormally the job of a qualified radiological control technician (RCT).

Instruments such as Geiger-Mueller (GM) counters, which countindividual photons in counts per minute (cpm), are sensitive tox-rays. However, because a low-energy and a high-energy photon

are both assigned one count, the GM counters tend to overrespondto the low-energy photons.

Measurement of radiation dose rates and surveys of record requirean instrument that reads in roentgen or rem (R/hour, mR/hour,rem/hour, mrem/hour). Ion chambers, which detect current insteadof counting pulses, have the flattest energy response.


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Personnel Monitoring Devices

Whole-Body Dosimeters

Operators of intentional XGDs wear whole-body dosimeters suchas thermoluminescent dosimeters (TLDs). TLDs can accuratelymeasure radiation doses as low as 10 mrem and are used toassess the legal dose of record. The records are available to theworkers from ESH-12 at any time. Hazardous situations orpractices that otherwise may go unnoticed can be spotted byhigher-than-usual dosimeter readings.

Whole-body dosimeters should be worn so that they represent thedose to the trunk of the body. Standard practice is to wear adosimeter between the neck and the waist, but in specific situationssuch as nonuniform radiation fields, special considerations may

apply. Some dosimeters have a required orientation with a specificside facing out. TLD badges must be worn with the LANL labelfacing outward.

PocketDosimeter

Whole-BodyDosimeter

Figure 11. Personnel Monitoring Devices

Pocket Dosimeters

Pocket ionization chambers such as pencil dosimeters or electronicdosimeters may be used as supplemental dosimetry for work inHigh Radiation Areas. Pencil dosimeters are manufactured withscales in several different ranges; the 0500 mR range, marked inincrements of 20 mR, is most often used. Pocket dosimeters, whichgive an immediate readout of the radiation dose, are supplementaland used primarily as ALARA tools.


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Personnel Monitoring Devicescontinued

Alarming Dosimeters

An alarming dosimeter may be used to provide an audible warningof radiation. This contributes to keeping doses ALARA byincreasing a workers awareness of the radiation.

Special Considerations

Specific applications may require special considerations. Forexample, low-energy x-rays will not penetrate the walls of somedosimeters, and flash XGDs produce a very short pulse that is notcorrectly measured by most dosimeters.

If you think you may need special dosimeters or instruments,contact an RCT or the ESH-12 XGD Control Office,7-8080.


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Self-Assessment

1. An XGD must be surveyed (EO1)

a. annually

b. semiannuallyc. quarterly

d. weekly

2. The sensitive instrument of choice to detectx-rays, in cpm,is a (an) (EO2)

a. personnel contamination monitor

b. thin layer of ZnS scintillator

c. thin-windowed GM counter

d. ion chamber

3. The best instrument to measure the dose rate for x-rays,in mR/hour, is a (an) (EO2)

a. personnel contamination monitor

b. thin layer of ZnS scintillator

c. thin-windowed GM counter

d. ion chamber

4. A TLD can measure doses as low as (EO3)

a. 0.5 mR per hour

b. 10 mrem

c. 10 rem

d. 5 R per hour


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5. When working with an intense source of x-rays, a pocketchamber is used to (EO3)

a. shield the user from radiation

b. provide an official record of the dose

c. provide an immediate estimate of the dose

d. measure the dose to the fingers

6. An alarming dosimeter provides (EO3)

a. a very accurate measurement of the total dose

b. an official record of the dose

c. an audible warning of the dose or dose rate

d. a reading of the dose to the fingers


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Answers

1. a

2. c

3. d4. b

5. c

6. c


54/107

Unit 5: Protective Measures


Unit Objectives

Major Objective

Upon completion of this unit, you will understand about protectivemeasures that restrict or control access to x-ray areas and devicesor warn of x-ray hazards, and about work documents that providespecific procedures to ensure safe operation of XGDs.



EO1 the purpose of posting,

EO2 the defining conditions and entry requirements for areascontrolled for radiological purposes,

EO3 the requirements for labels and warning signals,

EO4 the requirements for fail-safe interlocks,

EO5 the criteria for determining appropriate shielding, and

EO6 the purpose of an HCP and RWP and when each is used.


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Radiological Posting

Purpose of Posting

The two primary reasons for radiological posting are to inform workers of the area radiological conditions and

to inform workers of the entry requirements for the area.

In order to maintain exposure to radiation ALARA, access to areasor devices in which one can receive more than 100 mrem per yearis restricted.

CONTROLLED AREAAccess Controlled for Radiological Purposes

Contamination and External Radiation Hazards

May Exist within this Area

ENTRY REQUIREMENTS

(FACILITY-SPECIFIC REQUIREMENTS)

NOTICE

GRAVE DANGER

LOCATION

VERY HIGHRADIATION AREA

Max. Dose Rate

DATE RCT

Dose Rate Exceeds 500 rad/hr

rad/hr

SPECIAL CONTROLS REQUIRED FOR ENTRY

CONTACT FOR REQUIREMENTS

RADIOLOGICAL BUFFER AREA

Elevated Contamination, Airborne Radioactivity, and

External Radiation Hazards May Exist within this Area

CAUTION

ENTRY REQUIREMENTS

(FACILITY-SPECIFIC REQUIREMENTS)

RADIATION AREADose Equivalent Rate Exceeds 5 mrem/hr

CONTACT HEALTH PHYSICS

RAD WORKER 1 TRAINING

OTHER

TLD BADGE

LOCATION

Max. Dose Equivalent Rate

DATE RCT

mrem/hr

SUPPLEMENTAL DOSIMETER

RWP

CAUTION

ENTRY REQUIREMENTS

DANGER

LOCATION

HIGH RADIATION AREA

Max. Dose Equivalent Rate

DATE RCT

Dose Equivalent Rate Exceeds 100 mrem/hr

mrem/hr

ENTRY REQUIREMENTS

CONTACT HEALTH PHYSICS

RAD WORKER 2 TRAINING SUPPLEMENTAL DOSIMETER

TLD BADGE RWP

OTHER

Figure 12. Radiological Postings


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Radiological Postingcontinued

Posting Requirements

Areas controlled for radiological purposes must be posted witha black or magenta standard three-bladed radiological warningsymbol or trefoil on a yellow background. At LANL, black on yellowis used for most postings. Additionally, yellow and magenta ropes,tapes, chains, or other barriers can be used to mark the boundariesof radiological areas.

Postings and barriers must be clearly visible from all accessibledirections. Postings on doors should remain visible when doors areopen or closed. Postings should state the radiation dose rate andthe entry requirements. If more than one radiological hazard existsin an area, the posting should identify each hazard. Postings thatindicate an intermittent radiological condition should include astatement specifying when the condition exists such as; forexample, when a red light is on.

The same posting requirements apply for x-ray or gamma radiationas for any other type of radiation. Areas controlled for radiologicalpurposes are posted as shown in the following table. Most of thesearea definitions are standard throughout the United States.


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Radiological Postingcontinued

Posting Requirements

Area Posting Defining Condition Entry Requirements

Controlled Area >100 mrem/year

possible

General Employee

Radiological Training

Radiological

Buffer Area

n/a facility-specific

Radiation Area >5 mrem, but 100

mrem in any 1 hourat 30 cm from the

source or from anysurface that the

radiation penetrates

Radiological Worker I

Training

TLD

RWP (as required)

HighRadiation Area

>100 mrem in any 1hour, but 500 rad at

30 cm from the

source or from anysurface that theradiation penetrates,

but less than 500

rads in 1 hour at 1meter from aradiation source or

from any surface thatthe radiation

penetrates

Radiological Worker ITraining

TLD

supplemental dosimetry

RWP

Very High

Radiation Area

>500 rads in 1 hourat 1 meter from a

radiation source orfrom any surface that

the radiation

penetrates

special requirements


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Labels

The control panel of an intentional XGD must be labeled with thewords CAUTIONTHIS EQUIPMENT PRODUCESX-RAYS WHEN ENERGIZED.

An XGD that has been surveyed by the XGD Control Office andmeets safe operating requirements displays a LANL x-raycompliance label. A device that fails to meet all appropriate safetyrequirements displays a warning label indicating that the devicemust not be used.

An XGD must also display a label stating that the XGD ControlOffice must be notified (667-8080) if the machine is moved,transferred, or altered.

Warning Devices

CAUTIONRADIATION

This Equipment ProducesX-RADIATION When Energized

SHUTTEROPEN

X-RAYS ON

X-RAYS ON

FAIL SAFE

Figure 13. Labels and Indicator Lights

Warning signals are used to alert workers to the status of the x-raytube. Visible indicators that are activated automatically when poweris available for x-ray production include

a current meter on the XGD control panel,

a warning light labeled X-RAYS ON near or on the XGDcontrol panel,

a warning light or rotating beacon near the XGD or thex-ray room door, and

a SHUTTER OPEN indicator on or near the XGD.


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Warning Devicescontinued

For x-ray systems with an open beam in a shielded room, audibleand visible evacuation warning signals must be activated at least20 seconds before x-ray production can be started. Any personwho is inside the exposure room when warning signals come onshould immediately leave the room or activate the scram switch inthe room. The scram switch is an emergency off switch designedto shut down the x-ray system immediately.

Interlocks

Fail-safe interlocks are provided on doors and access panels ofx-ray facilities so that x-ray production is not possible when theyare open. A fail-safe interlock is designed so that any failure thatcan reasonably be anticipated will result in a condition in whichpersonnel are safe.

Interlocks must be tested by the x-ray-device custodian at leastevery six months for proper operation. The interlock test proceduremay be locally specified, but typically is as follows:

1. Energize the x-ray tube.

2. Open each door or access panel, one at a time.

3. Observe the x-ray warning light or the meter the measurescurrent at the control panel.

4. Record the results in a log book.

Shielding

Analytical Systems

For analytical x-ray machines such as x-ray fluorescence anddiffraction systems the manufacturer provides shielding inaccordance with ANSI N43.2. However, prudent practice requiresthat any device or source that involves radiation should be

surveyed to determine the adequacy of the shielding.


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Shieldingcontinued

Enclosed-beam systems have sufficient shielding so that the doserate does not exceed 0.25 mrem per hour under normal operatingconditions. The dose rate may be difficult to evaluate. Accordingto ANSI N43.2, this requirement is met if the shielding is equal tothe thickness of lead specified in the table below for the maximumrated anode current and voltage.

Shielding Requirements

Anode Current Millimeters of Lead

(mA) 50 kVp 70 kVp 100 kVp

20 1.5 5.6 7.7

40 1.6 5.8 7.9

80 1.6 5.9

160 1.7

Industrial Systems

Some industrial x-ray systems such as the cabinet x-ray systemsused for airport security are completely enclosed in an interlockedand shielded cabinet. Larger systems such as industrial x-ray unitsare enclosed in a shielded room to which access is restricted.Shielding for x-ray rooms is designed to handle the most severeoperating conditions of the x-ray machine. RCTs periodically verifythat the shielding integrity has not deteriorated or has not beencompromised.

XGD Control Office personnel develop recommendations forshielding based on the following information:

type of source,

voltage or energy,

amperage or current,

contemplated use,

expected workload,

structural details of the building, and

type of occupancy for all affected areas.


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Work Documents

Hazard Control Plans

Per LIR402-721-01, x-ray device custodians must compile a hazardcontrol plan (HCP) for each intentional x-ray device/facility inaccordance with LIR300-00-02, Documentation of Safe WorkPractices. In addition to defining the work, the HCPmust identify the hazards and describe the controls. Existingdocumentation provided by the manufacturer is normally sufficientto identify the hazards and describe the controls, if the apparatushas not been modified and will be used as designed.

Radiological Work Permits

In general RWPs are used to establish radiological controls for theconduct of radiological operations not covered under an approvedHCP. For example, radiological operations conducted in an areawhere the radiological conditions widely change or radiologicalactivities that are nonroutine are typically authorized and controlledunder an RWP. They serve to

inform workers of area radiological conditions,

inform workers of entry requirements for the areas, and

provide a means to relate radiation doses to specific workactivities.

RWPs are used in conjunction with XGDs when any of the followingsituations exist:

a compliance label for a newly acquired intentional XGD cannotbe issued because the HCP for that device has not yet beenwritten and approved,

a portable XGD for a one-time operation not described in the x-ray devices existing HCP, or

a nonroutine event requires that an operator must enter theradiation exposure room when the x-ray beam is on and x-raysare being produced so that either a High or Very High Radiation

Area exists.


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Work Documentscontinued

Integrated Safety Management and RWPs

Integrated Safety Management (ISM) is the framework that

supports LANL's commitment to Safety First. ISM involves fivesteps that are to be incorporated into all work activities. The RWPfollows these five steps, as follows:

1. Define the work. The work to be performed is defined in the firstsection, General Information.

2. Identify the hazards. The radiation hazards are identified in thesecond section, Pre-Job Radiological Conditions.

3. Implement Controls. The work controls are specified in the thirdsection, Radiological Protection Requirements.

4. Do the work safely. The fourth section specifies hold points,which are checks to ensure that dose levels are as expected.

5. Provide feedback. The final two sections, Post-Job RadiologicalConditions and Review, ensure that lessons learned arecommunicated to workers performing similar jobs in the future.


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Self-Assessment

1. A primary purpose of posting radiological areas is to (EO1)

a. prevent workers from entering radiological areas

b. inform workers of the radiological conditionsc. allow RCTs to measure the dose

d. eliminate all occupational doses at LANL

2. The types of posting used for Radiation and High RadiationAreas at LANL (EO2)

a. have a different meaning at each facility

b. have a different meaning at each DOE site

c. are standard throughout the United States

d. are sometimes in Spanish at LANL

3. Radiological Worker Training is required for all individuals who(EO2)

a. work at LANL

b. do not wear TLDs

c. enter Controlled Areas

d. enter Radiation Areas

4. In a Radiation Area the dose rate is (EO2)

a. 5 to 100 mrem per yearb. 5 to 100 rem per hour

c. 5 to 100 mrem per hour

d. 100 to 500 mrem per hour

5. Whenever x-rays are on, which of the following is required?(EO3)

a. a bell must ring continuously

b. a warning light must read X-RAYS ON

c. a line manager must be in the roomd. a scram switch must be pressed


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6. All of the following are true for x-ray interlocks, except(EO4)

a. they must be fail-safe

b. they must be tested every six monthsc. tests must be documented

d. they must be computer controlled

7. According to ANSI 43.2, approximately how much leadshielding is required for 70-kVp x-rays? (EO5)

a. 2 mm

b. 6 mm

c. 8 mm

d. 12 mm

8. An RWP is generally used instead of an HCP for (EO6)

a. routine work

b. nonroutine work

c. all work with x-rays

d. all work with radiation


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Answers

1. b

2. c

3. d4. c

5. b

6. d

7. b

8. b


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Unit 6: X-Ray-Generating Devices


Unit Objectives

Major Objective

Upon completion of this unit, you will understand the categories ofXGDs and the risks associated with each.



EO1 the difference between incidental and intentional XGDs;

EO2 the types of analytical and industrial XGDs;

EO3 the safety features essential for operation of analyticalenclosed- and open-beam systems; and

EO4 the safety features essential for operation of industrialcabinet, exempt shielded, shielded, unattended, and openinstallations.


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Intentional and Incidental Devices

X-ray systems are divided into two broad categories: intentionaland incidental.

An incidentalXGD produces x-rays that are not wanted or used asa part of the designed purpose of the machine. Examples ofincidental systems are computer monitors, televisions, electronmicroscopes, high-voltage electron guns, electron-beam weldingmachines, and electrostatic separators.

An intentionalXGD is designed to generate an x-ray beam for aparticular use. Intentional XGDs are typically housed within a fixed,interlocked and/or shielded enclosure or room. Examples include x-ray diffraction and fluorescence analysis systems, flash x-raysystems, medical x-ray machines, and industrial cabinet and

noncabinet x-ray installations.

X-ray generating devices/facilities may also be divided into twosubcategories: analytical and industrial, based upon increasingoperator radiation safety hazard. See LIR402-721-01.0 for thedefinitions/descriptions of Class I, Class II, and Class III x-raygenerating facilities.


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Incidental XGD