Carbon-14 Monitoring Programs at

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2002 RETS-REMP Workshop
Carbon-14 Monitoring Programs at Korean Nuclear
Power Plants
24-26 June 2002
Hee Geun Kim
Korea Electric Power Research Institute
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Topics for Presentation
1. Activity of Korean Nuclear Power Plants 2.
C-14 Monitoring Program at PHWRs 3. C-14
Measurement Pilot Study at PWRs 4. Conclusions
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1. Activity of Korean Nuclear Power Plants
? Commissioning of Kori NPP unit No. 1 in 1978. ?
By the end of 2001, Korea was operating 17
nuclear power generating units and 3 units
under construction.
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1. Activity of Korean Nuclear Power Plants
? Nuclear power plants and occupational radiation
exposure
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1. Activity of Korean Nuclear Power Plants
? Average dose per unit
man-rem/unit
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1. Activity of Korean Nuclear Power Plants
? Radioactive waste per unit
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2. C-14 Monitoring Program at PHWRs
? History/Background
- The Canadian Standards Association(CSA)
summarized C-14 releases assumptions in
CAN/CSA-N288.1-M87, Guidelines for Calculating
Derived Release Limits for Radioactive Material
in Airborne and Liquid Effluents for Normal
Operation of Nuclear Facilities(1987). - In
1995, the Advisory Committee on Radiological
Protection(ACRP), a scientific committee
charged with advising the CNSC(Canadian Nuclear
Safety Commission, formerly AECB), published a
report entitled The Management of C-14 in
Canadian Nuclear Facilities. - The ACRP
recommendation was subsequently adopted as an
assignment of a regulatory commitment (C-14
management plan) to report the licensees
estimated C-14 inventory and update annually.
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2. C-14 Monitoring Program at PHWRs
- According to regulatory commitment in Canada
and C-14 measurement pilot study at Korean
PHWRs(Wolsong NPPs), C-14 assumed to take form
of carbon dioxide with almost 100 released
through stack.
C-14 measurement pilot study
? Title The development of monitoring
techniques of radiocarbon from Korean heavy
water reactor ? Target unit Wolsong NPP unit
1 ? Period July 1995 December 1997 ?
Purpose - Production, removal and release
of C-14 from PHWRs - C-14 monitoring
techniques at stack and environment - Dose
assessment to the public due to C-14 release
? performed by independent Korean laboratory and
university
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2. C-14 Monitoring Program at PHWRs
? Results of C-14 pilot study at PHWRs
- Setup the C-14 monitoring program at plant and
environment - Development of the optimal
sampling and measuring techniques - Estimated
C-14 release through stack 16.2 Ci/unityr -
Estimated dose about 2mrem/yr - Effective
removal method at moderator by ion exchange
column
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2. C-14 Monitoring Program at PHWRs
? C-14 production-emissions breakdown
FUEL 3.37
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2. C-14 Monitoring Program at PHWRs
? Main C-14 production at PHWRs
(From Wolsong unit 2 FSAR)
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2. C-14 Monitoring Program at PHWRs
? Schematic diagram of C-14 measurement at main
stack
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2. C-14 Monitoring Program at PHWRs
? C-14 sampling and measuring flowcharts
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2. C-14 Monitoring Program at PHWRs
? C-14 release rate from 1999 to 2000
14C Activity inAir (measured by KINS, KHNP)
14C release rate to environment
0.8
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NW 22.3km, KHNP
N 1.0km, KINS
NNE 2.0km, KINS
SSW 2.0km, KINS
0.6
SSW 2.0km, KHNP
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C Realse rate (TBq)
C concentration in Air (Bq/g-C)
0.4
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14
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1999y
2000y
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KINS Korea Institute of Nuclear Safety KHNP
Korea Hydro and Nuclear Power
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999y 2000y
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2. C-14 Monitoring Program at PHWRs
? High natural background levels of C-14
14C Activity in pine needles(KINS)
14C Activity in Milk
Quarterly monthly
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2. C-14 Monitoring Program at PHWRs
? C-14 concentration effects from reactor
14C Concentration from reactor
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3. C-14 Measurement Pilot Study at PWRs
? Background
- Existing regulations in the United States do
not require monitoring of C-14 in liquid or
gaseous effluents, nor the assessment of dose
impacts from such effluents(From 2001 RETS/REMP
workshop). - However, the PWR/BWR-Gale code
estimates a nominal annual release of
approximately 10Ci/yr from a typical plant and
Regulatory Guide 1.109 allow for assessment of
dose impact. The estimated dose impact from
such releases is about 23 mrem/yr. - From 1998
based on ER of Wolsong 2, 3, 4 units, current
regulations in Korea require monitoring and
assessment of C-14 impacts at PHWRs. - From 2000
based on ER of Yonggwang 5, 6 units, C-14
measurement at PWR was issued by Korean
regulatory body.
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3. C-14 Measurement Pilot Study at PWRs
? Different C-14 chemical form of PWRs/PHWRs(EPRI
TR-105715, Characterization of generated
by the nuclear power industry/C. Kunz, C-14
discharge at three LWRs Health physics society
Vol. 49 No1). ? Different chemical form and
release pathway at PWR, BWR and PHWRs(C.
Kunz/EPRI TR-105715/pilot study at Wolsong NPP).
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3. C-14 Measurement Pilot Study at PWRs
? Korean approach on C-14 measurement and dose
assessment
- Although existing regulations in the USA do not
require monitoring of C-14 in gaseous and
liquid effluents and dose assessment to the
public, C-14 is important radionuclide to the
public dose. - Many of the reactor sites in
Korea have four to six operating units, so the
total collective dose impact from such a
multi-unit site is estimated at 12-20 mrem/yr
from carbon-14 releases.
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3. C-14 Measurement Pilot Study at PWRs
- Although it was calculated value, this fact
explains the heightened interest in C-14
methodologies in Korea. - We are now planning to
consider the C-14 measurement pilot study at
operating Korean PWRs and environment.
Target unit Yonggwang unit-3 (PWR,
1,000MWe, CE type) Measuring point Stack
and Radwaste building venting system
Measuring chemical form 14CO2 and 14CH4
Environmental sampling and dose assessment
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4. Conclusions
? C-14 measurement and dose assessment was
initiated at PHWR at first stage, but it was
transferred to PWRs. ? In Korea, C-14
measurement and dose assessment was the
major issue at the area of RP design and
operational HP. ? Based on the operational
experience at PHWRs, we are planning to
consider the C-14 measurement pilot study at
Korean PWRs (Yonggwang unit-3) next 2 or 3
year. ? After pilot measurement, we will
finally decide the C-14 measurement and
dose assessment at all Korean PWRs.
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C-14 concentration around Wolsong NPPs
Table. Specific activity of C-14 in environmental
samples around the Wolsong Nuclear Power
Plants(From Health physics Vol. 78, No. 6
Environmental Distribution and Behavior of H-3
and C-14 around Wolsong NPPs)
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Distribution of H2CO3, HCO3-, and CO32- at 25? as
a function of the pH of water
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C-14 production and release
? C-14 production in the PHWRs system
? C-14 releases to environment increase from Jun.
to Sept., 1999
- Air inflow to the system during refueling
period in 1999 (About 80 of N-14 natural
abundance in air) -
? Longer replacement period of resin due to
operational inexperience
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C-14 production and release
Stack
C-14 (CO2 Dominant)
Annulus gas
C-14 (HCO3- Dominant)
Moderator
Oxygen(O-17)
Heavy water(D2O)
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C-14 concentration around NPP and control area
Rice
Milk
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C-14 concentration around NPP and control area
Chinese cabbage
Persimmon
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C-14 concentration around NPP and control area
Egg
? Ulsan/Kyungju Control area
(about 30 km from NPP) Others around
NPP (about 2-5 km from NPP)