Download - Radiation Protection in Laboratory work
Radiation Protection in Laboratory work
Mats Isaksson, prof.Department of radiation physics, GU
Fundamental principles (ICRP)
Justification
Optimisation
Application of dose limits
Fundamental principles (ICRP)
Justification“Any decision that alters the radiation exposure
situation should do more good than harm.”
Fundamental principles (ICRP)
Optimisation“The likelihood of incurring exposure,
the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factors.”
(The ALARA-principle)
Fundamental principles (ICRP)
Application of dose limits“The total dose to any individual from regulated
sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits specified by the Commission.”
N.B. ”… other than medical exposure of patients…”
ICRP-report 103 identifies three exposure situations: planned, emergency and existing
Radiation doses 1
Absorbed dose (unit 1 Gy = 1 J kg-1)
Used in e.g. radiation therapy to specify the dose to the tumor
Different radiation qualities (a, b, g, n) can cause different degree of harm – weighting necessary
Radiation doses 2
Equivalent dose (unit 1 Sv = 1 J kg-1)
Used to calculate the dose to a tissue or organ
Weighting factors for different radiation qualities given by ICRP
Can be estimated by measurable quantities e.g.personal dose equivalent
Radiation doses 3
Effective dose (unit 1 Sv = 1 J kg-1)
Used to calculate the whole body dose that gives the same detriment as the actual partial body dose
Enables a comparison of risk from different exposure distributions
Radiation doses 3´
Illustration to effective dose
Radiation doses 4
Effective dose (unit 1 Sv = 1 J kg-1)
Weighting factors for different organs and tissues are given by ICRP
Can be estimated by measurable quantities e.g.ambient dose equivalent
”The bottom line”Medical diagnostics
Cosmic radiation
Caesium-137
Naturally occurring radionuclides in food
Radon in indoor air
K in the body
Soil and building materials
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X-ray and nuclear medicine
From ”Nuklearmedicin” by Sten Carlsson and Sven-Eric Svensson (available at http://www.sfnm.se/)
Radiation sources
Radioactive sources
Unsealed – liquid, gas, powder
Sealed
Technical equipmentX-ray machinesAccelerators
Ionizing radiation from radioactive elements
Generation of x-rays X-ray spectrum
X-ray equipment
Radiation safety in the lab
• External irradiation• Short range radiation, e.g. a, mostly
harmless when the source is outside the body
• b-emitters may cause severe skin damage if they are in contact with naked skin
Radiation safety in the lab
• Internal irradiation• Radioactive substances in non-sealed
sources (gas, liquid, powder) cause special concern
• Can enter the body through ingestion, inhalation, wounds or through the skin
Radiation safety in the lab
• External irradiation: Factors to be considered
• Time – more time spent in the radiation field gives a larger radiation dose
• Distance – inverse square law (for point source)
• Shielding – shielding material depends on the source (a, b, g)
Radiation safety in the labExternal irradiation: Inverse square
law
Radiation safety in the labExternal irradiation: Inverse square
law
Practical ALARA
• Practice before working with the real source
• Education before work• Separate office and lab work• Wear protective clothing and
gloves• All labs should be marked with
signs• Eat, drink etc outside the lab
Radiation safety in the labExternal irradiation: Shielding: b-
range in mmElectron energy / keV Al Fe Pb Plexi50 0.02 0.008 0.009 0.04100 0.07 0.03 0.03 0.1500 0.8 0.3 0.3 1.51 000 2.1 0.8 0.7 3.8
H-3: 19 keV; C-14: 156 keV; S-35: 167 keV; P-32: 1711 keV
Radiation safety in the labExternal irradiation: Shielding: g
HVL in mmPhoton energy / keV Al Cu Pb50 14 0.5 0.09100 16 2 0.12500 30 10 4.21 000 42 14 9
I-125: 35 keV; Tc-99m: 140 keV; I-131: 365 keV; Y-88: 1836 keV
Radiation safety in the lab
• Internal irradiation: Factors to be considered
• Activity – the larger the activity the larger the radiation dose (for a given radionuclide)
• Radionuclide – amount of energy per disintegration; type of radiation
• Metabolism – element and chemical form determine the residence time in the body and concentration in organs
Radiation safety in the labInternal irradiation: Effective half-life
Radionuclide T1/2,phys T1/2,biol T1/2,eff
H-3 12 y 10 d 10 dC-11 20 m 10-40 d 20 mC-14 5 700 y 10-40 d 10-40 dI-125 60 d 140 d 40 d
Radiation safety in the lab
• Classification of radionuclides• Class A: very high radiotoxicity (ex. a-
emitters: Pb-210, Pu-238, Cf-252,…)
• Class B: high radiotoxicity (Na-22, Ca-45, Co-56, Co-60, Sr-89, In-114m, I-125, I-131, Cs-137,…)
• Class C: moderate radiotoxicity (C-14, Na-24, P-32, S-35, Ca-47, Cr-51, Fe-55, Fe-59, Co-57, Co-58, Zn-65, Y-90, I-123, Tl-201…)
• Class D: low radiotoxicity (H-3, C-11, Tc-99m,…)
Deterministic effects – approximate threshold values
>0,1 Gy Effects on embryo and fetus
0,5 Gy Temporary sterility, men
2 Gy Cataract
4 Gy Temporary hair loss
5 Gy Skin erythema
6 Gy Permanent sterlility, men
8 Gy Pneumonia
2-12 Gy Permanent sterility, women
Deterministic effects – whole body irradiation
Lethal dose (50 % of exposed individuals survive): 3-4 Gy
Acute radiation syndrome – blood forming organs, gastro-intestinal tract & central nervous system
Stochastic effects – no threshold
Cancer and hereditary effects
Increasing risk with increasing dose
Risk factor only applicable on a population level
LNT-hypothesis
Laws and regulations
Strålskyddslagen SFS 1988:220• Employers obligations
• Workers obligations
• Licence demands
• Waste handling demands
• Medical examination
• Young people
Strålskyddsförordningen SFS 1988:293
Relevant regulations (SSM)SSMFS 2010:2 Radioactive waste
SSMFS 2011:2 Clearance of materials, premises, buildings och grounds
SSMFS 2008:25 Radiography
SSMFS 2008:51 Protection of workers and the public
SSMFS 2008:28 Laboratory work with unsealed radioactive sources
License from SSM for work with ionizing radiation
Licensee: University of GothenburgContact person Annhild LarssonRadiation protection
expert (GU) Annhild LarssonRadiation protection
expert (Rad. Phys.) Mats IsakssonLicense valid to 2016-02-07
SSMFS 2010:2 Radioactive waste
Revised limits
Documentation kept for 5 years
Yearly report to SSM concerning releases to sewage
*) Will probably be revised to 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv
Worker Student 16-18 a PublicYearly effective dose 50 6 1
Effective dose / consecutive 5-year period
100
Yearly equivalent dose to lens of the eye *)
150 50 15
Yearly equivalent dose to skin, hands and feet
500 150 50
SSMFS 2008:51: Dose limits (mSv)
SSMFS 2008:51: Protection of pregnant or breast feeding women
Women in fertile ages should be informed of the risks for the fetus
Pregnant women have the right to be relocated (if not, the effective dose to the fetus should not exceed 1 mSv during the rest of the pregnancy
Breast feeding women should not be exposed to a risk of being contaminated in the work
Protected area (”Skyddat område”)Category B worker• local rules (could be given verbally)• signs with the text ”skyddat område” and type of source
Category B (max activity per work activity)• Gamma emitting radioniclides: < 100
MBq• Beta emitters:
• < 10 MBq for beta energy > 0,3 MeV
• < 100 MBq for beta energy 0,1-0,3 MeV
• No work with open radiography
SSMFS 2008:51 Categorization
Nuclide Radio-toxicity class
Activity/work activityArb I(MBq)
Arb II(MBq)
Arb III(MBq)
H-3 D 100 1000 10000P-32 C 10 100 1000Cr-51 C 10 100 1000I-125 B 1 10 100
N.B. Local restrictions concerning max activity at departments
SSMFS 2008:28 Restrictions on activity in laboratory work
Arb I: Risk of inhalationArb II: Risk of external and internal exposure; small risk of inhalation
SSMFS 2008:28 Documentation/reporting
Data which should be documented, signed and kept available for concerned personnel:
• Received and stored radioactive substances, and their activities
• Possession of calibration sources• Results from ventilations and contamination
monitoring• Results from personnel dose monitoring and
estimations of internal doses
www.arbetsmiljo.adm.gu.se
www.studentlitteratur.se/#7403-02 (in Swedish)
www.stralsakerhetsmyndigheten.se
Thank you for your patience