Transcript SFP Boron Increases with ISFSI

TRITIUM MANAGEMENT
Causes of Tritium Effluent
Releases and Strategies for
Reducing Releases
Clay R. Madden
Columbia Generating Station
Chemistry Department
Presentation Outline
• How Does CGS Compare With the BWR Fleet
With Respect to Effluents
• Perspective of CGS and Effluent Limits
• Tritium and Boron Sampling
• Tritium and Boron Sources
– Activation, Fuel, CRB, SLC, CJW, ISFSI, HWC,
Recycle
• Tritium Releases
– Liquids, Evaporation of SFP, Steam Leaks, etc
• Considerations to Reducing Releases
Columbia vs. BWR Fleet Trends
Liquid Effluents
Gallons per Month
3.5E+05
3.0E+05
2.5E+05
2.0E+05
1.5E+05
1.0E+05
5.0E+04
WORST QUARTILE
YEAR
COLUMBIA
BEST QUARTILE
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0.0E+00
1992
GALLONS PER MONTH PER REACTOR
LIQUID VOLUME IN GALLONS PER MONTH PER REACTOR
MEDIAN
Columbia vs. BWR Fleet Trends
Liquid Effluents
Fission and Activation Products
LIQUID EFFLUENTS COMPARISON BY YEAR PER BWR REACTOR MIXED FISSION AND
ACTIVATION PRODUCTS (CURIES)
0.45
0.35
0.30
0.25
0.20
0.15
0.10
0.05
COLUMBIA
BEST QUARTILEYEAR
WORST QUARTILE
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
0.00
1986
CURIES PER BWR REACTOR
0.40
MEDIAN
Columbia vs. BWR Fleet Trends
Liquid Effluents - Tritium
LIQUID EFFLUENTS COMPARISONS BY YEAR PER BWR REACTORS TRITIUM (CURIES)
40
30
25
20
15
10
5
WORST QUARTILE
YEAR
MEDIAN
BEST QUARTILE
COLUMBIA
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
0
1970
CURIES PER BWR REACTOR
35
Columbia vs. BWR Fleet Trends
Gaseous Effluents
I-131 and Particulates
AIRBORNE EFFLUENTS COMPARISON BY YEAR PER BWR REACTOR
I-131 and Particulates (Curies)(Half-Life Equal to or Greater Than 8 Days)
1.E+00
1.E-01
1.E-02
1.E-03
COLUMBIA
YEAR
LOWEST QUARTILE
MEDIAN
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1.E-04
1970
CURIES PER BWR REACTOR
1.E+01
HIGHEST QUARTILE
Columbia vs. BWR Fleet Trends
Gaseous Effluents - Noble Gases
AIRBORNE EFFLUENTS COMPARISON BY YEAR PER BWR REACTOR
FISSION AND ACTIVATION GASES (TOTAL CURIES)
CURIES PER BWR REACTOR
1.E+06
1.E+05
1.E+04
1.E+03
1.E+02
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1.E+00
1970
1.E+01
YEAR
COLUMBIA
WORST QUARTILE
MEDIAN
BEST QUARTILE
Columbia vs. BWR Fleet Trends
Gaseous Effluents - Tritium
BWR AIRBORNE TRITIUM
100
80
60
40
20
COLUMBIA
LOWEST QUARTILE
MEDIAN
2003
2002
2001
2000
1999
0
1998
CURIES PER BWR REACTOR
120
HIGHEST QUARTILE
Perspective on ODCM Limits
131I, 133I, 3H,
& Particulates (>8d T½)
• 10CFR50 Appendix I Design Objective
– Organ Dose Limit:
– Actual Release in 2003:
– % of Guide:
15 mrem during year
0.01 mrem
0.067%
• 10CFR20-Based Limit:
– Organ Dose Limit:
– % of organ dose limit:
1500 mrem/year
0.00067%
50-Mile Offsite Dose
• 50-Mile population organ dose = .251 p-rem
– Maximum organ = lung
– 44% is from inhalation pathway
• 98.3% of this is from H-3
– 36% is from vegetable pathway
• 100% of this is from H-3
– In total, 99% of this dose is from H-3
• Average individual dose = 0.0007 millirem
2003 Columbia Releases
131I, 133I, 3H,
& Particulates (>8d T½)
Nuclide
Iodine-131
Iodine-133
Curies
0.0000299
0.000126
Strontium-89
Strontium-90
Cobalt-58
Cobalt-60
0.0000387
0.000000986
0.000135
0.000114
Manganese-54
Zinc-65
Hydrogen-3
0.0000498
0.000227
103
CGS Tritium Gaseous Effluent 1998-2004
Reactor
Turbine
Radwaste
18
16
14
12
10
8
6
4
2
0
Year
Curies
Released
1998
13
1999
10
2000
55
2001
51
2002
110
2003
103
Ja
n98
Ju
l-9
Ja 8
n99
Ju
l-9
Ja 9
n00
Ju
l-0
Ja 0
n01
Ju
l-0
Ja 1
n02
Ju
l-0
Ja 2
n03
Ju
l-0
Ja 3
n04
Curies Released
Turbine
Bldg
Tritium
Releases
20
Ja
n98
Ju
l-9
8
Ja
n99
Ju
l-9
9
Ja
n00
Ju
l-0
0
Ja
n01
Ju
l-0
1
Ja
n02
Ju
l-0
2
Ja
n03
Ju
l-0
3
Ja
n04
Microcuries/ml
Reactor Water Tritium
0.016
Reactor Water Tritium
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
Tritium Sampling
• Routine Tritium Grab Sampling
– Monthly from Turbine and Radwaste Buildings
– Weekly from Reactor Building
• Non Routine Sampling and Considerations
– Sampling building intakes
– Weekly from Turbine Building to test variance
– Exploring inline humidity monitors
Boron Sampling
• Historic Boron Sampling
– Semiannual from Demineralized Water Storage
Tank (DWST) and Condensate Storage Tanks
(CST)
• Changes to Boron Sampling
– Monthly from CST
– Weekly from SFP
– Weekly from Reactor Water
Tritium Production
• In a Boiling Water Reactor (BWR), tritium is
produced by three principal methods:
– Activation of naturally occurring deuterium in the
primary coolant,
– Ternary fission of UO2 fuel, and
– Neutron reactions with boron in control rods
• 10B(n,2 )3H – 0.008 - 0.0012 barns
• 10B(n,)7Li – 3838 barns; 7Li(n,n)3H – 0.086 barns
• FSAR production rate = 1.7E-4 Ci/sec/MWt
= 18.7 Curies/yr
Tritium Production
• Sources of Deuterium
– Water (Coolant) and Hydrogen Water Chemistry (minor)
• Sources of Boron-10
–
–
–
–
–
Leaking Control Rod Blades
Standby Liquid Control
Air Compressor Jacket Water (borated corrosion inhibitor)
Diesel Generator Cooling Jacket Water
Independent Spent Fuel Storage Installation (ISFSI) MPCs
• Sources of Tritium
– Leaking Fuel Rods and Control Rod Blades
– Heating, Ventilation, and Air Conditioning (HVAC) Intake from
Building Wake Effects
Leaking Control Rod Blades
• Three types of GE Control Rod Blades
(CRB) at Columbia
– Original Equipment - GE SIL 157 (1981)
– Duralife 215 - GE SIL 654 (2004)
– Marathon
• CRB Locations:
– Reactor Vessel
– Spent Fuel Pool (SFP)
Tritium and Boron Changes
Leaking Control Rod Blades
Reactor Power
Reactor Power (%)
Coolant Boron
Coolant Tritium
Coolant Boron (ppb)
Coolant Tritium (Ci/ml)
Standby Liquid Control
 At Columbia, loss of boron from Standby Liquid Control (SLC) was
ruled out based on the isolation valve type, limited testing of the
system, and precautions taken to keep it out of radwaste.
• Operations performs a surveillance on the SLC system periodically
which produces barrels of water that has been in contact with the SLC
system. Years ago, after the barrels were sampled by chemistry
personnel, the water was dumped down the storm drain piping. It was
found that the vent piping for the storm drain piping in the reactor
building was cross connected to the Reactor bldg. sump vent exhaust
system.
• This allowed (due to air flow and condensation) boric acid to be
present in the reactor building sumps. The boric acid in the sumps was
not removed by resins when the water was reprocessed and it
subsequently ended up the the reactor.
SLC Boron Level Changes
Compressor Jacket Water
• Borated corrosion inhibitor leaked from the CJW
surge tank to the floor drain following corrective
maintenance.
• Loss of the borated corrosion inhibitor (Nalco
2100) to the Floor Drain System means it will end
up in Radwaste for processing.
• Radwaste water treatment is not very effective at
removing boron and some of the boron can make
it to the reactor.
ISFSI MPCs
Increases in Boron not seen in
other metals or nuclides.
ISFSI MPCs
• 30-47 Grams of Boron released to SFP
per ISFSI cask loaded
– Based on ~35 ppb increase in the pool for
each cask and a pool volume of 356,700
gallons
• Hydrostatic pressure on lowering into
SFP
ISFSI MPCs
What is Boral?
Boral
Stainless Steel
Alloy Aluminum
Boral: B4C and Al
Alloy Aluminum
Alloy Steel Basket Wall
ISFSI MPCs
• Boron Migration/Dilution/Concentration
– Letdown of SFP to CST is 5,000 gallons/cask
– Makeup from Evaporation is 1,000 gallons/day
– Boron in the spent fuel pool can make its way
into radwaste when the filter/demineralizers are
backwashed and ultimately end up in the CSTs.
– Water in the vessel, Suppression Pool, SFP, and
CST commingles during refueling operations.
Refueling Commingle
Gallons
Vessel, Feedwater, and Condensate
458,000
Boron
(ppb)
140
Spent Fuel Pool
356,700
250
Suppression Pool
932,500
70
Condensate Storage Tanks
658,400
10
2,405,600
94
Commingle Result
Tritium Release
• Essentially all tritium in the primary
coolant is eventually released to the
environment
– Liquid Effluents
• Columbia’s last release was September 1998
– Offgas contains HT and HTO.
• Evaporation of Spent Fuel Pool, Sumps, Tanks
• Turbine Building Steam Leaks
– Solids
• Dewatered Spent Resin
Evaporation of Spent Fuel Pool
• Total curies released from Reactor building
– 1.6 curies per month (2003)
– 1.2 curie per month (2004).
• Evaporation rate based on curies released
– 44,000 gallons per month (2003)
– 30,000 gallons per month (2004).
Turbine Building Steam Leaks
• Developed a calculation to estimate steam leak
rate using the increase in tritium concentration in
the outlet air.
• Ran test cases from 1998 to 2003 to estimate leak
rate.
• Spot checked results against water balance data
for selected periods
• Results agreed surprisingly well.
• Indications are that the average leak rate has not
changed over several years
Turbine Building Steam Leaks
• A quantitative analysis of the extent of steam leaks was
attempted for 1998 (low tritium effluents) and for 2003 for
comparison and calculation validation.
1998
2003
The average non-outage Turbine building leak rate
(gallons/min)
5.5
6
The total Turbine building H-3 released (Curies)
12
81
The average condensate H-3 concentration
(microcuries/ml)
1.88E-03 9.60E-03
• The leak rate has been fairly constant. However, both the curies
released and the condensate tritium concentration have increased by a
factor of 6.8 and 5.1 respectively.
Station Dose to Reduce Steam
Leaks
Year
Person-Rem
2002
2003
2004*
1.107
3.367
2.226
* to
date – 6/2004
Actions to Reduce Releases
• Reduce the primary system tritium
concentration: Release water to the river.
• Pro
– May be able to decrease Primary system concentration sooner.
• Con
– This again will require about 2 million gallons of release and
would require about 6 months to complete. During this time the
liquid effluent release indicators would degrade to third or forth
quartile. Erodes public confidence and trust.
Actions to Reduce Releases
• Reduce the primary system tritium concentration:
Allow make-up for steam leaks and SFP
evaporation to slowly dilute the tritium to the
baseline value.
• Pro
– Little or no work is involved. We will gradually move to improved
quartiles as this occurs. Relies on limited boron introduction.
• Con
– This will require a loss of about 2 million gallons of water and 8 –
10 months at our current leak rate
Actions to Reduce Releases
• Reduce the primary system tritium and
boron concentration: Quickly reposition
leaking CRBs out of the active core.
• Pro
– Boron and tritium begin to decline.
• Con
– This reactive approach doesn’t prevent the initial
tritium and boron intrusion and reduction is slow.
Actions to Reduce Releases
• Reduce tritium gaseous effluent release rate:
Repair steam leaks in TG bldg.
• Pro
– The leak rate reduction will provide a directly proportional reduction in
the release rate. The reactor bldg. release from the fuel pool is around 1
Ci/month at the current tritium concentration. That means that the TG
bldg. leaks would need to be near zero to achieve first quartile.
• Con
– This will “bottle up” the existing tritium and extend the time we are
susceptible to high releases with any new leaks.
– Repair of leaks is high dose work even at reduced power compared to
offsite dose from tritium release.
Actions to Reduce Releases
• Remove potential sources of tritium and boron in
the plant: Replace Control Rod Blades prior to end
of life.
• Pro
– This proactive position will reduce the likelihood of future boron
and tritium intrusions.
• Con
– The CRBs cost $85,000 each. The total cost of the 27 blades that
will reach end of life next cycle is $2.3M. The disposal cost could
reach $13M.
Conclusions for Columbia
• Quickly identify leaking CRBs and reposition or
move them out of the active core.
• Reduce Turbine Building steam leaks to prevent
equipment degradation, not for effluent control.
• Proactively prevent/mitigate boron intrusion into
radwaste systems from borated corrosion
inhibitors.
• Consider methods to reduce ISFSI MPC boron
impurity levels.
For Consideration
• Is the BWR fleet comparing apples to apples?
– Sampling and analysis similar?
– LLD low enough?
– Dilution air interference?
• If your coolant tritium concentration is stable or
trending down, you ARE releasing.
– Is your monitoring program detecting it?
– Does your effluent report reflect it?
LLD and Curies H-3
LLD
1E-061
1E-07
1E-08
1E-09
1E-10
2E-112
1 Columbia
Curies H-3
0
0
98.42
103.08
103.29
103.29
ODCM required LLD
2 Current Columbia LLD for H-3