Implementation Program of Two-dosimeter
Algorithm for Better Estimation of Effective
Dose during Maintenance Periods at KNPPs
2007. 09. 12
Hee Geun Kim
Nuclear Power Laboratory
Korea Electric Power Research Institute
I. Introduction
 Effective Dose
 Primary protection dose quantity.
- HE: ICRP-26 (1977), E: ICRP-60 (1991).
- Provide “risk-based” radiation protection system.
 Not directly measurable.
E   wT HT
T
 Measure radiation dose outside the body and
convert it to E.
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I. Introduction
 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.
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Topics for Presentations
I.
Introduction
II.
Two-dosimeter Approach
III. Application Test
IV. Test Results
V. Implementation Program
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II. Two-dosimeter Approach
 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.
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II. Two-dosimeter Approach
 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.
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II. Two-dosimeter approach
 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).
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II. Two-dosimeter approach
 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.
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II. Two-dosimeter Approach
 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)
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II. Two-Dosimeter Approach
 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)
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II. Two-Dosimeter Approach
 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)
4. NCRP(55/50) Algorithm (NCRP-122; 1995)
5. EPRI Algorithm (NRC RIS 2004-1)
6. Lakshmanan Algorithm (1991)
7. Kim(58/42) Algorithm (1999)
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II. Two-Dosimeter Approach
 Canadian OPG Algorithm;
E = 0.11 Hp(10)head + 0.89 Hp(10)torso
 ANSI N13.41 (1997) Algorithm;
HE =  WcHp,c(10) = 0.10 Hp,head and neck(10) + 0.90 Hp,rest(10)
 NCRP(70/30) Algorithm (1995);
HE(estimate) = 0.7 Hp(10)front + 0.3 Hp(10)back
 NCRP(55/50) Algorithm (1995);
HE(estimate) = 0.55 Hp(10)front + 0.50 Hp(10)back
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II. Two-Dosimeter Approach
 EPRI Algorithm; USNRC, RIS 2004-01;
Hp(10)max. of front or back + Hp(10)avg. of front and back
HE(estimate) = ─────────────────────
2
 Lakshmanan Algorithm (1991);
Hp(10)front + Hp(10)back
HE(estimate) = ───────────
1.5
 Kim Algorithm (1998);
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)
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II. Two-Dosimeter Approach
Compartment
 Name
Effective
Head/Neck
Thorax
Abdomen
Fraction of WT
Weighting
WT from
Organs & Tissues
Factor for
WAssociated
of Head/Neck
& Chest Assigned
of OPGto Program
T for Exposure
ICRP 60
Compartment
Compartment
Bone Marrow (red)
Esophagus
Thyroid
Skin
Bone Surface
Total for Compartment (Rounded)
0.12
0.05
0.05
0.01
0.01
0.18
0.60
1.00
0.40
0.33
0.022
0.030
0.050
0.004
0.003
0.11
Bone Marrow (red)
Lung
Stomach
Breast
Liver
Esophagus
Skin
Bone Surface
Total for Compartment (Rounded)
Gonads
Bone Marrow (red)
Colon
Stomach
Bladder
Liver
Skin
Bone Surface
Remainder
Total for Compartment (Rounded)
0.12
0.12
0.12
0.05
0.05
0.05
0.01
0.01
0.41
1.00
0.40
1.00
0.40
0.40
0.30
0.33
0.20
0.12
0.12
0.12
0.05
0.05
0.01
0.01
0.05
1.00
0.41
1.00
0.60
1.00
0.60
0.30
0.33
1.00
0.049
0.120
0.048
0.050
0.020
0.020
0.003
0.003
0.31
0.200
0.048
0.120
0.072
0.050
0.030
0.003
0.003
0.050
0.58
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II. Two-Dosimeter Approach
 Compartment Factor of ANSI N13.41 (1997)
Area of the Body
Compartment Factor, Wc
Head and neck
Thorax, above the diaphragm
Abdomen, including the pelvis
Upper right arm
Upper left arm
Right thigh
Left thigh
0.10
0.38
0.50
0.005
0.005
0.005
0.005
☞ Almost similar to Canadian OPG Algorithm
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III. Application Test
 Steam Generator Geometry
SIDE VIEW
TOP VIEW
photon field from U-tubes
phantom
AS
BS
(0,0,0)
tubesheet
120 cm
195 cm
200 cm
(0,0,0)
interior wall
divider plate
70 cm
200 cm
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200 cm
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III. Application Test
 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%
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III. Application Test
 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
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III. Application Test
 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 twodosimeter 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
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IV. Test Results
 Deep Dose at Yonggwang Unit 4
Work
S/G
Nozzle
Dam Ins.
(#4-7th)
KEPRI
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Personal
Name
A
B
C
D
E
F
G
H
I
J
K
L
M
TLD Readout
Head Chest Back
4.25
2.96
3.68
2.60
2.09
2.71
2.41
1.9
2.13
2.29
1.57
2.07
3.57
2.73
3.69
2.73
1.80
2.25
3.51
2.62
3.02
2.00
1.75
2.00
2.19
1.81
2.09
1.93
1.71
2.04
2.34
1.71
2.24
1.82
1.52
1.86
2.02
1.50
1.97
(Unit: mSv)
ADR Readout
Head Chest Back
4.47
3.36
4.03
2.85
2.25
2.99
2.65
1.97
2.57
2.68
1.93
2.37
4.02
2.94
4.16
2.87
1.99
2.75
4.03
2.68
3.65
2.23
1.79
2.18
2.53
1.90
2.42
2.26
1.87
2.30
2.56
1.77
2.42
2.06
1.61
2.17
2.28
1.73
2.21
 2007.9.12~13
20/34
IV. Test Results
 Effective Dose at Yonggwang Unit 4
Work
Personal
Name
S/G
Nozzle
Dam Ins.
(#4-7th)
A
B
C
D
E
F
G
H
I
J
K
L
M
KEPRI
NUCLEAR POWER LAB
NUCLEAR ENGINEERING GROUP
(Unit: mSv)
Effective Dose
Max. Canada
NCRP NCRP EPRI LakshANSI
Kim
Value (ICRP-60)
(70/30) (55/50) (Xu) manan
4.25
2.71
2.41
2.29
3.69
2.73
3.51
2.00
2.19
2.04
2.34
1.86
2.02
3.10
2.15
1.96
1.65
2.82
1.90
2.72
1.78
1.85
1.73
1.78
1.55
1.56
3.09
2.14
1.95
1.64
2.81
1.89
2.71
1.78
1.85
1.73
1.77
1.55
1.55
3.18
2.28
1.97
1.72
3.02
1.94
2.74
1.83
1.89
1.81
1.87
1.62
1.64
3.47
2.50
2.11
1.90
3.35
2.12
2.95
1.96
2.04
1.96
2.06
1.77
1.81
3.50
2.56
2.07
1.95
3.45
2.14
2.92
1.94
2.02
1.96
2.11
1.78
1.85
4.43
3.20
2.69
2.43
4.28
2.70
3.76
2.50
2.60
2.50
2.63
2.25
2.31
 2007.9.12~13
3.43
2.47
2.10
1.87
3.29
2.09
2.93
1.95
2.02
1.94
2.03
1.75
1.78
21/34
IV. Test Results
 The Comparison of Two-Dosimeter Algorithm at YG
Dose (mSv)
Effectivedose,
Effective
HE (mSv)
6
Canada (ICRP-60)
NCRP (70/30)
EPRI (Xu)
Kim
5
ANSI
NCRP (55/50)
Lakshmanan
Yonggwang Unit 4,
S/G Nozzle Dam Installation (#4-7th)
4
3
2
1
0
A
B
C
D
E
F
G
H
I
J
K
L
M
TLD
Numbers
TLD
Number
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IV. 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
DoseH(mSv)
Effectivedose,
Effective
E (mSv)
6
Canada (ICRP-60)
NCRP (70/30)
EPRI (Xu)
Kim
5
ANSI
NCRP (55/50)
Lakshmanan
Yonggwang Unit 4,
S/G Nozzle Dam Installation (#4-7th)
4
3
2
1
0
A
E
G
B
C
F
I
K
H
J
D
M
L
TLD
TLDNumbers
Number
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IV. 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
6
(mSv)
Dose
Effective
Effective
dose,
HE (mSv)
5
Canada(ICRP-60)
ANSI
NCRP(70/30)
NCRP(55/50)
EPRI(Xu)
Lakshmanan
Kim
4
S/G Nozzle Dam Installation(#4-7th)
3
2
1
0
0
5
10
15
20
25
30
Number
TLDTLD
Numbers
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IV. Test Results
(mSv)E (mSv)
Effective
Effective
doseDose
equivalent,
H
 The Comparison of Two-Dosimeter Algorithm at YG
6
5
Canada(ICRP-60)
ANSI
NCRP(70/30)
NCRP(55/50)
EPRI(Xu)
Lakshmanan
Kim
4
Yonggwang Unit 4,
S/G Nozzle Dam Removal (# 4-7th)
3
2
1
0
0
5
10
15
20
 2007.9.12~13
25/34
TLDNumbers
Number
TLD
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IV. Test Results
(mSv) E (mSv)
Effective
Effective
doseDose
equivalent,
H
 The Comparison of Two-Dosimeter Algorithm at YG
6
Canada(ICRP-60)
NCRP(70/30)
EPRI(Xu)
Kim
5
4
ANSI
NCRP(55/50)
Lakshmanan
Yonggwang Unit 4,
Rx Head Penetration Test (# 4-7th)
3
2
1
0
0
2
4
6
8
10
12
14
TLD Num
ber
TLD
Numbers
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IV. Test Results
(mSv)E (mSv)
Effective
Effective
doseDose
equivalent,
H
 The Comparison of Two-Dosimeter Algorithm at YG
6
5
Canada(ICRP-60)
ANSI
NCRP(70/30)
NCRP(55/50)
EPRI(Xu)
Lakshmanan
Kim
4
Yonggwang Unit 4,
PZR Heater Replacement (# 4-7th)
3
2
1
0
0
1
2
3
4
5
6
TLD Numbers
Number
TLD
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IV. Test results
 Deep Dose at Ulchin Unit 4
Work
S/G
Nozzle
Dam Ins.
KEPRI
NUCLEAR POWER LAB
NUCLEAR ENGINEERING GROUP
Personal
Name
(Unit: mSv)
TLD Readout
ADR Readout
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
-
L
0.11
0.12
-
0.13
0.13
-
 2007.9.12~13
28/34
IV. Test Results
 Effective Dose at Ulchin Unit 4
Work
Effective Dose
Personal
Max.
Name
S/G
Nozzle
Dam
Ins.
(Unit 4)
KEPRI
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(Unit: mSv)
Canada
NCRP NCRP EPRI LakshANSI
Value (ICRP-60)
(70/30) (55/50) (Xu) manan
Kim
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
-
-
L
0.12
0.12
0.12
-
-
0.12
-
-
 2007.9.12~13
29/34
IV. Test Results
Effective
(mSv)
doseDose
equivalent,
(mSv)E H
Effective
 The Comparison of Two-Dosimeter Algorithm at UC
6
Canada(ICRP-60)
NCRP(70/30)
EPRI(Xu)
Kim
5
4
ANSI
NCRP(55/50)
Lakshmanan
Unchin Unit 4,
S/G Nozzle Dam Installation
3
2
1
0
0
2
4
6
8
10
12
14
TLD
Number
TLD Numbers
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IV. Test Results
(mSv) E (mSv)
Dose
Effective
Effective
dose
equivalent,
H
 The Comparison of Two-Dosimeter Algorithm at UC
6
5
Canada(ICRP-60)
ANSI
NCRP(70/30)
NCRP(55/50)
EPRI(Xu)
Lakshmanan
Kim
4
Ulchin Unit 4,
S/G Nozzle Dam Removal
3
2
1
0
0
2
4
6
8
10
TLD Num
ber
TLD
Numbers
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 2007.9.12~13
31/34
V. Implementation Program
 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.
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32/34
V. Implementation Program
 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)
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NUCLEAR POWER LAB
NUCLEAR ENGINEERING GROUP
 2007.9.12~13
33/34
Thank you
for attention!!
KEPRI
NUCLEAR POWER LAB
NUCLEAR ENGINEERING GROUP
 2007.9.12~13
34/34