2007. 09. 12 hee geun kim nuclear power laboratory

Implementation Program of Two-dosimeter Implementation Program of Two-dosimeter Algorithm for Better Estimation of Effective Algorithm for Better Estimation of Effective Dose during Maintenance Periods at KNPPsDose during Maintenance Periods at KNPPs

Implementation Program of Two-dosimeter Implementation Program of Two-dosimeter Algorithm for Better Estimation of Effective Algorithm for Better Estimation of Effective Dose during Maintenance Periods at KNPPsDose during Maintenance Periods at KNPPs

2007. 09. 12

Hee Geun Kim

Nuclear Power LaboratoryKorea Electric Power Research Institute

KEPRINUCLEAR POWER LABNUCLEAR ENGINEERING GROUP

2007.9.12~13 2/34

Effective Dose

Primary protection dose quantity. - HE: ICRP-26 (1977), E: ICRP-60 (1991).

- Provide “risk-based” radiation protection system.

Not directly measurable.

Measure radiation dose outside the body and convert it to E.

I. IntroductionI. IntroductionI. IntroductionI. Introduction

E w HT TT


2007.9.12~13 3/34

Effective Dose

A single dosimeter on the chest: - Hp(10) → E.

- acceptable only for frontal incident radiations.

If photon beam comes from the back or high? - severe underestimation (7-10 times).

- ICRP-75 (1997) “dosimeter should be worn at an appropriate position on the body”

How do we solve this problem? Two-dosimeter approach.

I. IntroductionI. IntroductionI. IntroductionI. Introduction


2007.9.12~13 4/34

Topics for PresentationsTopics for PresentationsTopics for PresentationsTopics for Presentations

I. Introduction

II. Two-dosimeter Approach

III. Application Test

IV. Test Results

V. Implementation Program


2007.9.12~13 5/34

Two-dosimeter Approach

Several investigators suggested using “two dosimeters”. - Chest + Back or Chest + Head

- at least one dosimeter always directly exposed.

NCRP-122 (1995) recommended using two dosimeters

“for scenarios where the irradiation geometry or photon

energy is unknown or difficult to characterize.”

How do we combine these dosimeter readings for the best estimation of E? Chest and back position.

II. Two-dosimeter ApproachII. Two-dosimeter ApproachII. Two-dosimeter ApproachII. Two-dosimeter Approach


2007.9.12~13 6/34

Results of Two-dosimeter Approach

The best combination of dosimeter weighting factors are the various values for the chest and back dosimeters or the chest and head dosimeters.

Underestimation problem for posterior incident radiation was completely avoided by using two dosimeters and the developed algorithm.

Overestimation problem does exist for typical beam directions, but significantly decreases in real situations.

II. Two-dosimeter ApproachII. Two-dosimeter Approach II. Two-dosimeter ApproachII. Two-dosimeter Approach


2007.9.12~13 7/34

Relocate the Whole Body TLD Dosimetry (INPO 91-014)

Known work area dose-rate gradients make it likely that total dose to a portion of the whole body will exceed the chest dose by more than 50 % (e.g., dosimeter worn on the head when most of the dose rate in the work area is from overhead piping); and

Dose rates in the general work area exceed 100 mrem/hr(1mSv/hr).

II. Two-dosimeter approachII. Two-dosimeter approachII. Two-dosimeter approachII. Two-dosimeter approach


2007.9.12~13 8/34

Issue the Multi Whole Body TLD Dosimetry (INPO 91-014)

Measured or anticipated work area dose-rate gradients make it possible for dose to one or more portions of the whole-body to exceed that of the chest by more than 50 percent; or

Dose rates in the work area exceed 100 mrem/hr and dose gradients are unknown or varying; and

Whole-body dose in excess of 300 mrem(3mSv) is expected during the job.

II. Two-dosimeter approachII. Two-dosimeter approachII. Two-dosimeter approachII. Two-dosimeter approach


2007.9.12~13 9/34

Current Two Dosimetry Practices in Korea Protection guideline and procedure for multi-TLD - Upper level program of dosimetry or health physics

- Procedure of External dosimetry or dose assessment

Maintenance of Steam Generator (SG), Reactor Coolant Pump(RCP) and Reactor Head Internal(RHI)

Applying the two-dosimeter (chest and head)

Hp(10)maximum → E (No applying the two-dosimeter algorithm)

The issued conditions of two-dosimeter are based on the INPO Guideline (INPO 91-014; 1995)

II. Two-dosimeter ApproachII. Two-dosimeter ApproachII. Two-dosimeter ApproachII. Two-dosimeter Approach


2007.9.12~13 10/34

According to previous study results:

Single-dosimeter approach significantly underestimates

HE (E) in some exposure situations.

Two-dosimeter approach does not underestimate HE (E)

by more than 5%.

7 two-dosimeter algorithms have specific techical bases

- Two dosimeters readout: Chest/head or chest/back

- Specific weighting factor

- Solid and specific technical background

- Application high radiation field (ex, SG chamber)

II. Two-Dosimeter ApproachII. Two-Dosimeter ApproachII. Two-Dosimeter ApproachII. Two-Dosimeter Approach


2007.9.12~13 11/34


Two-Dosimeter Algorithms ☞ Considered the 7 algorithms based on previous investigation results.

1. Canadian Utility (OPG) Algorithm

2. ANSI N13.41 (1997) Algorithm

3. NCRP(70/30) Algorithm (NCRP-122; 1995)


5. EPRI Algorithm (NRC RIS 2004-1)

6. Lakshmanan Algorithm (1991)

7. Kim(58/42) Algorithm (1999)

1. Canadian Utility (OPG) Algorithm

2. ANSI N13.41 (1997) Algorithm



5. EPRI Algorithm (NRC RIS 2004-1)

6. Lakshmanan Algorithm (1991)

7. Kim(58/42) Algorithm (1999)


2007.9.12~13 12/34

II. Two-Dosimeter ApproachII. Two-Dosimeter ApproachII. Two-Dosimeter ApproachII. Two-Dosimeter Approach Canadian OPG Algorithm;

ANSI N13.41 (1997) Algorithm;

NCRP(70/30) Algorithm (1995);

NCRP(55/50) Algorithm (1995);

E = 0.11 Hp(10)head + 0.89 Hp(10)torso E = 0.11 Hp(10)head + 0.89 Hp(10)torso

HE = WcHp,c(10) = 0.10 Hp,head and neck(10) + 0.90 Hp,rest(10)HE = WcHp,c(10) = 0.10 Hp,head and neck(10) + 0.90 Hp,rest(10)

HE(estimate) = 0.7 Hp(10)front + 0.3 Hp(10)back HE(estimate) = 0.7 Hp(10)front + 0.3 Hp(10)back

HE(estimate) = 0.55 Hp(10)front + 0.50 Hp(10)back HE(estimate) = 0.55 Hp(10)front + 0.50 Hp(10)back


2007.9.12~13 13/34


EPRI Algorithm; USNRC, RIS 2004-01;

Lakshmanan Algorithm (1991);

Kim Algorithm (1998);

Hp(10)max. of front or back + Hp(10)avg. of front and back

HE(estimate) = ───────────────────── 2

Hp(10)max. of front or back + Hp(10)avg. of front and back

HE(estimate) = ───────────────────── 2

Hp(10)front + Hp(10)back

HE(estimate) = ─────────── 1.5

Hp(10)front + Hp(10)back

HE(estimate) = ─────────── 1.5

HE(estimate) = h(HE) [0.58 HP(10)front + 0.42 HP(10)back]

0.9 HE(AP) where h(HE) = ───────────── 1.02

0.58 Hf(AP) + 0.42 Hb(AP)

HE(estimate) = h(HE) [0.58 HP(10)front + 0.42 HP(10)back]

0.9 HE(AP) where h(HE) = ───────────── 1.02

0.58 Hf(AP) + 0.42 Hb(AP)


2007.9.12~13 14/34


Effective WT for Exposure of Head/Neck & Chest of OPG ProgramCompartment

Name

CompartmentName WT from

ICRP 60

WT fromICRP 60

Fraction of WT Assigned to Compartment

Fraction of WT Assigned to Compartment

WeightingFactor for

Compartment

WeightingFactor for

CompartmentAssociated Organs & TissuesAssociated Organs & Tissues

Head/NeckHead/Neck

0.120.050.050.010.01

0.120.050.050.010.01

0.180.601.000.400.33

0.180.601.000.400.33

0.0220.0300.0500.0040.0030.11

0.0220.0300.0500.0040.0030.11

Bone Marrow (red)EsophagusThyroidSkinBone SurfaceTotal for Compartment (Rounded)

Bone Marrow (red)EsophagusThyroidSkinBone SurfaceTotal for Compartment (Rounded)

ThoraxThorax

0.120.120.120.050.050.050.010.01

0.120.120.120.050.050.050.010.01

0.411.000.401.000.400.400.300.33

0.411.000.401.000.400.400.300.33

0.0490.1200.0480.0500.0200.0200.0030.0030.31

0.0490.1200.0480.0500.0200.0200.0030.0030.31

Bone Marrow (red)LungStomachBreastLiverEsophagusSkinBone SurfaceTotal for Compartment (Rounded)

Bone Marrow (red)LungStomachBreastLiverEsophagusSkinBone SurfaceTotal for Compartment (Rounded)

AbdomenAbdomen

0.200.120.120.120.050.050.010.010.05

0.200.120.120.120.050.050.010.010.05

1.000.411.000.601.000.600.300.331.00

1.000.411.000.601.000.600.300.331.00

0.2000.0480.1200.0720.0500.0300.0030.0030.0500.58

0.2000.0480.1200.0720.0500.0300.0030.0030.0500.58

GonadsBone Marrow (red)ColonStomachBladderLiverSkinBone SurfaceRemainderTotal for Compartment (Rounded)

GonadsBone Marrow (red)ColonStomachBladderLiverSkinBone SurfaceRemainderTotal for Compartment (Rounded)


2007.9.12~13 15/34

Compartment Factor of ANSI N13.41 (1997)

☞ Almost similar to Canadian OPG Algorithm


Area of the BodyArea of the Body

Head and neck

Thorax, above the diaphragm

Abdomen, including the pelvis

Upper right arm

Upper left arm

Right thigh

Left thigh

Head and neck

Thorax, above the diaphragm

Abdomen, including the pelvis

Upper right arm

Upper left arm

Right thigh

Left thigh

Compartment Factor, WcCompartment Factor, Wc

0.10

0.38

0.50

0.005

0.005

0.005

0.005

0.10

0.38

0.50

0.005

0.005

0.005

0.005


2007.9.12~13 16/34

III. Application TestIII. Application TestIII. Application TestIII. Application Test

Steam Generator Geometry

195 cm

200 cm

120 cm

70 cm

(0,0,0)

AS BS

photon field from U-tubes

200 cm

200 cm

(0,0,0)

TOP VIEWSIDE VIEW

tubesheet

divider plate

interior wall

phantom


2007.9.12~13 17/34


Steam Generator General

Combustion Engineering type S/G

Radiation field in a S/G channel head depends on many factors.

However, dominated by 60Co and 58Co (~95%)

Source term and photon field from upper U tubes

Dose rate is non-uniform and gradient from high to low

Dose rate exceeds few mSv/hr and gradient of the chest by more than 50%


2007.9.12~13 18/34


Application Test during Maintenance Periods

Algorithm considered : 7 algorithms

Pilot plant: Yonggwang unit 4 and Ulchin unit 4

Target work: very high radiation dose or gradient (ex, Steam Generator, Pressurizer and Reactor Head Penetration Test…)

Fully explain to workers before test

Issue 6 dosimeters (3 TLDs and 3 ADRs)

Readout the TLD and calculated the effective dose


2007.9.12~13 19/34


Application Test during Maintenance Periods

- 3 TLDs and 3 ADRs provided to radiation workers wearing at head, chest and back simultaneously.

- The effective dose(E) are calculated based on deep dose of 2 TLD readouts for the purpose of the adoption of two- dosimeter algorithm for KNPPs among several algorithms.

- E is analyzed and sorted for searching of algorithm trend analysis from high effective dose to low E.

- Technical approach and work convenience (interview)

- Consult and comment (independent review) from the experts of Monte Carlo Simulation and specialists


2007.9.12~13 20/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results Deep Dose at Yonggwang Unit 4

TLD Readout ADR ReadoutWork

PersonalName Head Chest Back Head Chest Back

A 4.25 2.96 3.68 4.47 3.36 4.03B 2.60 2.09 2.71 2.85 2.25 2.99C 2.41 1.9 2.13 2.65 1.97 2.57D 2.29 1.57 2.07 2.68 1.93 2.37E 3.57 2.73 3.69 4.02 2.94 4.16F 2.73 1.80 2.25 2.87 1.99 2.75G 3.51 2.62 3.02 4.03 2.68 3.65H 2.00 1.75 2.00 2.23 1.79 2.18I 2.19 1.81 2.09 2.53 1.90 2.42J 1.93 1.71 2.04 2.26 1.87 2.30K 2.34 1.71 2.24 2.56 1.77 2.42L 1.82 1.52 1.86 2.06 1.61 2.17

S/GNozzle

Dam Ins.(#4-7th)

M 2.02 1.50 1.97 2.28 1.73 2.21

(Unit: mSv)


2007.9.12~13 21/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results Effective Dose at Yonggwang Unit 4 (Unit: mSv)

Effective DoseWork

PersonalName Max.

ValueCanada

(ICRP-60)ANSI

NCRP(70/30)

NCRP(55/50)

EPRI(Xu)

Laksh-manan

Kim

A 4.25 3.10 3.09 3.18 3.47 3.50 4.43 3.43B 2.71 2.15 2.14 2.28 2.50 2.56 3.20 2.47C 2.41 1.96 1.95 1.97 2.11 2.07 2.69 2.10D 2.29 1.65 1.64 1.72 1.90 1.95 2.43 1.87E 3.69 2.82 2.81 3.02 3.35 3.45 4.28 3.29F 2.73 1.90 1.89 1.94 2.12 2.14 2.70 2.09G 3.51 2.72 2.71 2.74 2.95 2.92 3.76 2.93H 2.00 1.78 1.78 1.83 1.96 1.94 2.50 1.95I 2.19 1.85 1.85 1.89 2.04 2.02 2.60 2.02J 2.04 1.73 1.73 1.81 1.96 1.96 2.50 1.94K 2.34 1.78 1.77 1.87 2.06 2.11 2.63 2.03L 1.86 1.55 1.55 1.62 1.77 1.78 2.25 1.75

S/GNozzle

Dam Ins.(#4-7th)

M 2.02 1.56 1.55 1.64 1.81 1.85 2.31 1.78


2007.9.12~13 22/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results The Comparison of Two-Dosimeter Algorithm at YG

0

1

2

3

4

5

6

TLD Number

Eff

ective

do

se

, H E (m

Sv)

Canada (ICRP-60) ANSINCRP (70/30) NCRP (55/50)EPRI (Xu) LakshmananKim

Yonggwang Unit 4,S/G Nozzle Dam Installation (#4-7th)

A B C D E F G H I J K L M

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 23/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results The Comparison of Two-Dosimeter Algorithm at YG ☞ The TLD Number is sorted by effective dose(E) from high E to low E

0

1

2

3

4

5

6

TLD Number

Eff

ective

do

se

, H E (m

Sv)

Canada (ICRP-60) ANSINCRP (70/30) NCRP (55/50)EPRI (Xu) LakshmananKim

Yonggwang Unit 4,S/G Nozzle Dam Installation (#4-7th)

A E G B C F I K H J D M L

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 24/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results The Comparison of Two-Dosimeter Algorithm at YG ☞ The TLD Number is sorted by effective dose(E) from high E to low E

0

1

2

3

4

5

6

0 5 10 15 20 25 30TLD Number

Eff

ective d

ose,

HE (

mSv)

Canada(ICRP- 60) ANSI

NCRP(70/30) NCRP(55/50)

EPRI(Xu) Lakshmanan

Kim

S/G Nozzle Dam Installation(#4-7th)

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 25/34


0

1

2

3

4

5

6

0 5 10 15 20

TLD Number

Eff

ective

dose e

quiv

ale

nt,

HE (

mSv)

Canada(ICRP-60) ANSI

NCRP(70/30) NCRP(55/50)

EPRI(Xu) Lakshmanan

Kim

Yonggwang Unit 4,S/G Nozzle Dam Removal (#4-7th)

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 26/34


0

1

2

3

4

5

6

0 2 4 6 8 10 12 14

TLD Number

Eff

ective

dose e

quiv

ale

nt,

HE (

mSv)

Canada(ICRP-60) ANSINCRP(70/30) NCRP(55/50)

EPRI(Xu) LakshmananKim

Yonggwang Unit 4,Rx Head Penetration Test (#4-7th)

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 27/34


0

1

2

3

4

5

6

0 1 2 3 4 5 6

TLD Number

Eff

ective

dose e

quiv

ale

nt,

HE (

mSv)


NCRP(70/30) NCRP(55/50)

EPRI(Xu) Lakshmanan

Kim

Yonggwang Unit 4,PZR Heater Replacement (#4-7th)

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 28/34

Deep Dose at Ulchin Unit 4 (Unit: mSv)

TLD Readout ADR ReadoutWork

PersonalName Head Chest Back Head Chest Back

A 0.75 0.62 0.78 0.84 0.66 0.91

B 0.86 0.59 0.77 0.93 0.62 0.88

C 0.55 0.39 0.61 0.65 0.43 0.68

D 1.33 0.98 1.35 1.45 1.05 1.51

E 0.93 0.6 0.82 0.91 0.64 0.80

F 0.73 0.47 0.66 0.7 0.42 0.65

G 0.45 0.30 - 0.57 0.35 -

H 0.06 0.08 - 0.07 0.11 -

I 0.04 0.09 - 0.05 0.05 -

J 0.15 0.16 - 0.17 0.18 -

K 0.01 0.03 - 0.02 0.05 -

S/GNozzle

Dam Ins.

L 0.11 0.12 - 0.13 0.13 -

IV. Test resultsIV. Test resultsIV. Test resultsIV. Test results


2007.9.12~13 29/34

Effective Dose at Ulchin Unit 4 (Unit: mSv)

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results

Effective DoseWork

PersonalName

Max.

Value

Canada

(ICRP-60)ANSI

NCRP

(70/30)

NCRP

(55/50)

EPRI

(Xu)

Laksh-

mananKim

A 0.78 0.63 0.63 0.67 0.73 0.74 0.93 0.72

B 0.86 0.62 0.62 0.64 0.71 0.73 0.91 0.70

C 0.61 0.41 0.41 0.46 0.52 0.56 0.67 0.51

D 1.35 1.02 1.02 1.09 1.21 1.26 1.55 1.19

E 0.93 0.64 0.63 0.67 0.74 0.77 0.95 0.73

F 0.73 0.50 0.50 0.53 0.59 0.61 0.75 0.58

G 0.45 0.32 0.32 - - 0.30 - -

H 0.08 0.08 0.08 - - 0.08 - -

I 0.09 0.08 0.09 - - 0.09 - -

J 0.16 0.16 0.16 - - 0.16 - -

K 0.03 0.03 0.03 - - 0.03 - -

S/GNozzleDamIns.

(Unit 4)

L 0.12 0.12 0.12 - - 0.12 - -


2007.9.12~13 30/34

The Comparison of Two-Dosimeter Algorithm at UC

0

1

2

3

4

5

6

0 2 4 6 8 10 12 14

TLD Number

Effect

ive d

ose

equi

vale

nt,

HE (m

Sv)

Canada(ICRP-60) ANSINCRP(70/30) NCRP(55/50)EPRI(Xu) LakshmananKim

Unchin Unit 4,S/G Nozzle Dam Installation

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 31/34

IV. Test ResultsIV. Test ResultsIV. Test ResultsIV. Test Results The Comparison of Two-Dosimeter Algorithm at UC

0

1

2

3

4

5

6

0 2 4 6 8 10

TLD Number

Eff

ective

dose e

quiv

ale

nt,

HE (

mSv)


NCRP(70/30) NCRP(55/50)

EPRI(Xu) Lakshmanan

Kim

Ulchin Unit 4,S/G Nozzle Dam Removal

Eff

ecti

ve D

ose

(mS

v)

TLD Numbers


2007.9.12~13 32/34

We investigated the application practice and considered the seven two-dosimeter algorithms for implementing test.

3 TLDs provided to workers wearing the head, chest and back simultaneously based on algorithm characteristics during maintenance periods at KNPPs

• The best combination of two-dosimeter algorithms is the chest & back or chest & head dosimeters ? chest & back

The trend of effective dose is almost same (any algorithm is OK) except Laksmanan algorithm.

Finally NCRP(55/50) algorithm was adopted because its

work convenience, reliability & technical aspects for implementing to KNPPs.

V. Implementation ProgramV. Implementation ProgramV. Implementation ProgramV. Implementation Program


2007.9.12~13 33/34

TLD Issue condition: INPO 91-014 Guideline

≥ 2 mSv for single job

Target work: S/G, PZR & RCP etc

Number of TLD issued: Two

TLD position issued: Chest and Back

Algorithm adopted: NCRP(55/50)

Application schedule: From January 2006

(already reviewed by Korean regulator and implemented to NPPs)

V. Implementation ProgramV. Implementation ProgramV. Implementation ProgramV. Implementation Program


2007.9.12~13 34/34

Thank youThank youfor attention!!for attention!!

2007. 09. 12 hee geun kim nuclear power laboratory

Documents

chest dose

dose gradients

dosimeter algorithm

dosimeter readings

single dosimeter

total dose

measure radiation dose

varying andwholebody