Presentation on theme: "Clay R. Madden Columbia Generating Station Chemistry Department"— Presentation transcript:
1 Clay R. Madden Columbia Generating Station Chemistry Department TRITIUM MANAGEMENTCauses of Tritium Effluent Releases and Strategies for Reducing ReleasesClay R. MaddenColumbia Generating StationChemistry Department
2 Presentation OutlineHow Does CGS Compare With the BWR Fleet With Respect to EffluentsPerspective of CGS and Effluent LimitsTritium and Boron SamplingTritium and Boron SourcesActivation, Fuel, CRB, SLC, CJW, ISFSI, HWC, RecycleTritium ReleasesLiquids, Evaporation of SFP, Steam Leaks, etcConsiderations to Reducing Releases
3 Columbia vs. BWR Fleet Trends Liquid Effluents Gallons per Month
4 Columbia vs. BWR Fleet Trends Liquid Effluents Fission and Activation Products
5 Columbia vs. BWR Fleet Trends Liquid Effluents - Tritium
6 Columbia vs. BWR Fleet Trends Gaseous EffluentsI-131 and Particulates
7 Columbia vs. BWR Fleet Trends Gaseous Effluents - Noble Gases
8 Columbia vs. BWR Fleet Trends Gaseous Effluents - Tritium
9 Perspective on ODCM Limits 131I, 133I, 3H, & Particulates (>8d T½)10CFR50 Appendix I Design ObjectiveOrgan Dose Limit: 15 mrem during yearActual Release in 2003: 0.01 mrem% of Guide: % 10CFR20-Based Limit:Organ Dose Limit: mrem/year% of organ dose limit: %
10 50-Mile Offsite Dose 50-Mile population organ dose = .251 p-rem Maximum organ = lung44% is from inhalation pathway98.3% of this is from H-336% is from vegetable pathway100% of this is from H-3In total, 99% of this dose is from H-3Average individual dose = millirem
14 Tritium Sampling Routine Tritium Grab Sampling Monthly from Turbine and Radwaste BuildingsWeekly from Reactor BuildingNon Routine Sampling and ConsiderationsSampling building intakesWeekly from Turbine Building to test varianceExploring inline humidity monitors
15 Boron Sampling Historic Boron Sampling Changes to Boron Sampling Semiannual from Demineralized Water Storage Tank (DWST) and Condensate Storage Tanks (CST)Changes to Boron SamplingMonthly from CSTWeekly from SFPWeekly from Reactor Water
16 Tritium ProductionIn 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, andNeutron reactions with boron in control rods10B(n,2 )3H – barns10B(n,)7Li – 3838 barns; 7Li(n,n)3H – barnsFSAR production rate = 1.7E-4 Ci/sec/MWt = 18.7 Curies/yr
17 Tritium Production Sources of Deuterium Sources of Boron-10 Water (Coolant) and Hydrogen Water Chemistry (minor)Sources of Boron-10Leaking Control Rod BladesStandby Liquid ControlAir Compressor Jacket Water (borated corrosion inhibitor)Diesel Generator Cooling Jacket WaterIndependent Spent Fuel Storage Installation (ISFSI) MPCsSources of TritiumLeaking Fuel Rods and Control Rod BladesHeating, Ventilation, and Air Conditioning (HVAC) Intake from Building Wake Effects
18 Leaking Control Rod Blades Three types of GE Control Rod Blades (CRB) at ColumbiaOriginal Equipment - GE SIL 157 (1981)Duralife GE SIL 654 (2004)MarathonCRB Locations:Reactor VesselSpent Fuel Pool (SFP)
20 Leaking Control Rod Blades Reactor PowerReactor Power (%)Coolant Boron (ppb)Coolant Tritium (Ci/ml)Coolant BoronCoolant Tritium
21 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.
23 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.
25 Increases in Boron not seen in other metals or nuclides.
26 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 gallonsHydrostatic pressure on lowering into SFP
27 Alloy Steel Basket Wall ISFSI MPCsWhat is Boral?Alloy AluminumBoral: B4C and AlAlloy Steel Basket WallStainless SteelBoral
28 ISFSI MPCs Boron Migration/Dilution/Concentration Letdown of SFP to CST is 5,000 gallons/caskMakeup from Evaporation is 1,000 gallons/dayBoron 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.
30 Tritium ReleaseEssentially all tritium in the primary coolant is eventually released to the environmentLiquid EffluentsColumbia’s last release was September 1998Offgas contains HT and HTO.Evaporation of Spent Fuel Pool, Sumps, TanksTurbine Building Steam LeaksSolidsDewatered Spent Resin
31 Evaporation of Spent Fuel Pool Total curies released from Reactor building1.6 curies per month (2003)1.2 curie per month (2004).Evaporation rate based on curies released44,000 gallons per month (2003)30,000 gallons per month (2004).
32 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 periodsResults agreed surprisingly well.Indications are that the average leak rate has not changed over several years
33 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.19982003The average non-outage Turbine building leak rate (gallons/min)5.56The total Turbine building H-3 released (Curies)1281The average condensate H-3 concentration (microcuries/ml)1.88E-039.60E-03The 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.
34 Station Dose to Reduce Steam Leaks YearPerson-Rem20021.10720033.3672004*2.226* to date – 6/2004
35 Actions to Reduce Releases Reduce the primary system tritium concentration: Release water to the river.ProMay be able to decrease Primary system concentration sooner.ConThis 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.
36 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.ProLittle or no work is involved. We will gradually move to improved quartiles as this occurs. Relies on limited boron introduction.ConThis will require a loss of about 2 million gallons of water and 8 – 10 months at our current leak rate
37 Actions to Reduce Releases Reduce the primary system tritium and boron concentration: Quickly reposition leaking CRBs out of the active core.ProBoron and tritium begin to decline.ConThis reactive approach doesn’t prevent the initial tritium and boron intrusion and reduction is slow.
38 Actions to Reduce Releases Reduce tritium gaseous effluent release rate:Repair steam leaks in TG bldg.ProThe 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.ConThis 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.
39 Actions to Reduce Releases Remove potential sources of tritium and boron in the plant: Replace Control Rod Blades prior to end of life.ProThis proactive position will reduce the likelihood of future boron and tritium intrusions.ConThe 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.
40 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.
41 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?
42 LLD and Curies H-3 LLD Curies H-3 1E-061 1E-07 1E-08 98.42 1E-09 1E-071E-0898.421E-09103.081E-10103.292E-1121 Columbia ODCM required LLD2 Current Columbia LLD for H-3