ML18038B665
| ML18038B665 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 02/05/1996 |
| From: | Leaver D, Metcalf J POLESTAR APPLIED TECHNOLOGY, INC. |
| To: | |
| Shared Package | |
| ML18038B664 | List: |
| References | |
| PSAT-04000U.04, PSAT-04000U.04-R01, PSAT-4000U.4, PSAT-4000U.4-R1, NUDOCS 9604180251 | |
| Download: ML18038B665 (18) | |
Text
PSAT 04000U.04 Polestar NON-PROP RlETARY Page 1 of 11 Revision:
1 CALCULATIONPACKAGE FOR APPLICATIONOF THE REVISED DBA SOURCE TERM TO THE BROWNS FERRY NUCLEARPOWER PLANT prepared by:
POLESTAR APPLIED TECHNOLOGY, INC.
for the ELECTRIC POWER RESEARCH INSTITUTE Revision Reason Project Manager Reviewer InitialIssue Revison 1 ofAttachment 3 James etcalf.
Dave Leaver C La
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ames Metcal Dave Leaver
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9604180251 960412 PDR ADQCK 05000259 PDR
ENCLOSURE 2
TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2, AND 3 TECHNICAL SPECIFICATION (TS)
- 356, INCREASE IN ALLOWABLE MAIN STEAM ISOLATION VALVE (MSIV) LEAKAGE RATE CONTROL ROOM OPERATOR AND OFFSITE DOSE CALCULATIONS (NON-PROPRIETERY VERSIONS)
(SEE ATTACHED)
PSAT 04000U.04 Table of Contents Page2of ll Revision:
1 Purpose Methodology Key Assumptions/Conservatisms References Summary ofCalculations Results Conclusions 10 Enhhn ABB-CE Calculation 1066-SRT95-C-002, "Calculation of Containment Leakage Doses for Browns Ferry", September 29, 1995 which includes a letter dated September 20, 1995 from James Metcalf(Project Manager, PSAT) to Raymond Schneider (ABB-CE Technical Contact) modifying the original contract workscope PSAT Project Data Base 04000U.03, September 22, 1995 PSAT Calculation 04011H.01, "VolumetricFlowrate as a Function ofTime &omDrywellto Torus (and Return)", December 6, 1995 PSAT Calculation 04001H.02, "Aerosol Decay Rates (Lambda) in Drywell", September 1, 1995 PSAT Calculation 04011H.03, "Maximum Elemental Iodine Decontamination Factors", September 1, 1995 PSAT Calculation 04011H.04, "Suppression Pool Scrubbing EfBciency (Including Pool Bypass)", September 1, 1995 PSAT Calculation 04011H.05, "AdditionalRadionuclide Data",
September 19, 1995
PSAT 04000U.04 Page 3 of 11 Revision:
1 PSAT Calculation 04011H.06, "Source Term for Use FerryApplicationofNUREG-r
-1465", September 28, 1995 PSAT Calculation 04011H.07, "D ell L P
rywell Leakage Rate Direct to g
lyByp ofSGTS" S
t b
10 PSAT Calculation 04002H.08, "Aerosol Decoontami nation Factor in ines, September 19, 1995 PSAT Calculation 04002H.09, "ElementalIod'y earn mes", September 28, 1995 12 N/A Fax dated September 1, 1995 from Don McCamy TVATechnical Contact) to James Metcalf(PSAT Project Mana er r
referenceforItem328 f h P
o t e rojectDataBase 13 N/A Notes ofTelecon dated September 13 1995 b Metcalf~SAT P etween James Prospect Manager) and Don McCam TVA Technical Contact~
rovi '
) providing concurrence for time-shift of migation X/Qs (Item 5.1 ofProject Data Base)
Purpose The purpose ofthis calculation package is to corn ile a set of together constitute the application ofthe revised D r
a ion or the purpose ofdemonstrating compliance'with 1 d thr t 'fSGTSooperating and Case 2 which includes two trains ofSGTS operating.
Methodology The approach makes use oftwo computer models and man n,,
p
- p ttac ent 2 is not a calculatio thr lo to (th t oPol t
A 1'edT use o control and coordinate the re gy ces in Los Altos, CA and Portsmo th,,
s ar pp i Technolo oQi us ion ngineering of6ce a subcon u
o tractor to Polestar, in%indso CT)
- rowns Ferry review ofplant-specific input.
The two computer models include STARNAUA, s co e (Reference 2), an aerosol physics code
PSAT 04000U.04 Page 4 of 11 Revision:
1 proprietary to Polestar, and TVADOSE (Reference 3), a slightly modified version ofthe proprietary LDOSE dose calculation code belonging to ABB-CE.
The overall approach has been to treat the containment as a two-control volume model (drywell and torus airspace) up until the time that the core debris from the recovered core damage accident (see Key Assumption 1 and Attachment 3) has been quenched.
Beyond that time, a high mixing rate is used between the two control volumes to eBectively create a single-control volume containment similar to current practice. Prior to the debris quench, vent flow and suppression pool bypass from the drywell to the torus is considered.
The source term (the activity release from the reactor to the drywell) is based on Reference 1 (see Attachment 8).
Release paths that are included are as follows (see Attachment 1):
Drywell leak Equal to two percent ofthe drywell volume per day - leak is to the reactor building Torus airspace leak Equal to two percent ofthe torus airspace volume per day-leak is to the reactor building MSIVleak Equal to 250 scfli from the drywell (total for four steamlines) - leak is to the main condenser via the drain line pathway CAD operation Equal to 8340 cflifrom the torus airspace intermittently over 30 days (containment is well-mixed by the time of CAD operation so a drywell source would be equivalent)-
all ofthe flowis through the SGTS liters, 99.97% ofthe flowis to the stack, 0.03% to the stack room (i.e., stack bypass)
Torus vent leak SGTS operation Equal to 10 cfh from the torus airspace - leak is to the stack Equal to 1.32E6 cflifor Case 1 and 0.9E6 cflifor Case 2-flow is from the reactor building to the stack (except for 300 cfliwhich goes to the stack room as bypass) through the SGTS filters SGTS bypass Equal to 3.1E-3 cflidirectly from drywell for Case 2 only (leakrate is two percent per day with reduction factor of approximately 40000 to account for reactor building hold-
PSAT 04000U.04 Page 5 of 11 Revision:
1 up) - leak is to the environment Leak from stack room Equal to 300 cfh (assumed to be same as inleakage, see "SGTS operation", above) - leak is to the environment Leak from main condenser Equal to 250 cfh (assumed to be same as leakage out of drywell as scfh, see "MSIVleak", above) - leak is to the environment (leak is actually to turbine building but turbine building hold-up is neglected)
The TVADOSE code integrates the release through the various pathways; and, using Reference 4-based dose conversion factors, calculates doses at the EAB (integrated over the first two hours ofthe accident) and at the LPZ and in the control room (integrated over 30 days). TVADOSE also includes the following:
~
Deposition in the drywell and, after core debris quench, in the torus airspace
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Suppression pool scrubbing
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Deposition in the main steamlines up to the drain line connection
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Active filtrationby the SGTS and CREVS, but without credit for charcoal adsorbers These efFects are included in TVADOSEvia filtration efFiciencies and removal "lambdas" provided by Polestar.
These matters are discussed further under Summary ofCalculations.
Key Assumptions/Conservatisms Key Assumption 1:
The core damage which leads to the DBAsource term ofReference 1 is arrested by the restoration ofcore cooling at about two hours after the start ofthe accident. Qi2;uzjlgz, This is an extension to operating plants ofa position presented in Reference 5 for advanced LWRs and is discussed fullyin Attachment 3.
Key Assumption 2 The source terms ofReference 1 can be applied to Browns Ferry without regard for fuel burn-up limitations. ~~gg. This issue derives &om a caveat in Section 3.6 ofReference 1 and is being pursued separately by NEI with NRC. Since the Reference 1 source term is specified in terms of fractions ofcore inventory and since core inventories are calculated for this application to Browns Ferry using an appropriate burn-up, the caveat is not related to core inventory. As noted in Reference 1, the focus ofthe caveat
i
PSAT 04000U.04 Page 6 of ll Revision:
1 is the gap activity release; and because ofthe nature ofthis application to Browns Ferry, the results would not be greatly sensitive to the exact gap release timing or magnitude in any case.
Key Assumption 3 The MSIVleakage release is entirely through the drainline and main condenser; there is no release considered via the high pressure turbine.
J~~jgg. From Reference 6 it is observed that the flow split between the drainline/main condenser flowpath and the high pressure turbine flowpath is about 200:1.
Since deposition in the steamlines applies to either flowpath and since deposition in the steamlines is the only deposition considered for MSIVleakage (see Attachments 1, 10, and 11}, the only mechanism that could create a difference in the calculated relative dose between the two pathways is delay in the main condenser.
This eEect is estimated to be of the order ofa factor oftwo to three in dose reduction; therefore, the importance ofincluding the high pressure turbine release would be to increase the dose by one percent to one-and-a-half percent.
This is considered negligible.
Key Assumption 4 ApH value ofat least 6.0 willbe maintained in the containment water (in particular, the suppression pool) for at least 30 days (3.7 half-lives ofI-131} after the start ofthe accident. Dimming.'
non-Safety Related scoping study was conducted as part ofthis project to support this assumption.
This non-Safety Related study is being followed-up with a Safety-Related calculation being performed under a separate contract.
Key Assumption 5:
The results ofthese analysis are sufBciently conservative to constitute a basis for demonstrating compliance with the requirements of 10CFR100 and with 10CFR50, Appendix A, GDC-19. Qiggg,gjgg. The source terms ofReference 1 are comparable in conservatism to the DBAsource terms previously used on Browns Ferry as based on 10CFR100 (and Reference 7) and subsequent regulatory guidance.
The noble gas and iodine release fractions (which are the main determinants ofthe whole body and thyroid dose evaluations specified in 10CFR100) are about the same.
The Reference 1 timing and chemical form, while diQerent from the previous source terms, are nonetheless conservative compared to what is expected under actual accident conditions (e.g., the 1979 accident at Three Mile Island} and provide a more physically correct representation ofactivity release to the containment.
Moreover, in terms of activity transport within and through the containment system and release to the environment, there are many other conservatisms included in the calculations ofAttachments 3 through 11. These are as follows:
PSAT 04000U.04 Page 7 of 11 Revision:
1
~
Conservatism 1:
Only gamma energy is considered in calculating the core power used to determine vent flowfrom the drywell to the torus during core degradation and the associated debris quench.
Core debris sensible heat during the core degradation (and the formation ofa debris bed that would enhance heat transfer to the overlaying water), metal-water reactions, and beta heating are neglected.
See.
~
Conservatism 2:
Aconservatively small sedimentation area has been specified for the drywell. Moreover, the sedimentation removal lambdas calculated for the drywell are applied to the torus airspace after the debris quench.
(No sedimentation is credited in the torus airspace prior to the debris quench).
Due to the eFects ofpool bypass (see Conservatism 5) the mass airborne in the torus airspace at the end ofthe quench is greater than that airborne in the drywell, and the torus airspace has a smaller volume and a greater sedimentation area.
Therefore, to apply drywell lambdas in the torus after debris quench is a significant conservatism.
See Attachment 4.
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Conservatism 3:
Hygroscopicity is neglected in the determination ofsedimentation lambdas.
See Attachment 4.
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Conservatism 4:
The maximum iodine DF is based on the maximum pool temperature and does not consider the long-term iodate reaction which willtend to suppress iodine re-evolution. Both ofthese sects willtend to limitthe long-term potential for iodine re-evolution even ifthe containment pH falls below the value of6.0 assumed in the analysis.
See Attachment 5.
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Conservatism 5:
The pool bypass low area used to assess the impact ofpool bypass on pool scrubbing efBciency is ten times the value used as the basis for the surveillance test acceptance limit. Moreover, a review of surveillance test data indicates that the actual measured value is, on average, substantially below the test acceptance value.
See.
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Conservatism 6:
Te-132 is treated as elemental I-132 except for half-lifewhich corresponds to Te-132. This is to account for the fact that Te-132 (which may have been removed as particulate and subsequently held up on filters and/or in main steam piping) may re-evolve as elemental I-132. By treating the Te-132 as elemental I-132 from the beginning (with the Te-132 half-life), the same amount ofI-132
Page 8 of 11 Revision:
1 activity is released as would be the case in a mechanistic model of the process described, but the release occurs much more rapidly.
This means that more adverse X/Q values, breathing rates, and control room occupancy factors are used in calculating the thyroid dose contribution ofTe-132 than would be the case with a mechanistic model.
See Attachment 7.
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Conservatism 7:
In general, the PWR gap release is expected to occur much more rapidly than the BWR gap release (refer to discussion in Reference 1). However, this application has used a gap release start time of 30 seconds (appropriate for a PWR) to represent the Browns Ferry BWR. See Attachment 8.
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Conservatism &:
The impact ofnon-noble gas and non-radioiodine components of the release on the 10CFR100 and GDC-19 dose calculations has been assessed in two ways: (1) the important isotopes of radiocesium and Te-132 have been included explicitly, and (2) the "other" radionuclides have been approximated using a one percent release to the containment atmosphere as described in Reference 7 (with the exception that these radionuclides are subsequently treated as aerosol and released to the environment accordingly). By doing so, the impact ofthe "Other" has been overstated by about a factor often as compared to rigorous application ofReference l.
See Attachments 7 and 8.
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Conservatism 9:
The steamline Qowrate used to assess aerosol deposition in the steamline is based on 100 scfh per line. However, the overall dose assessment is based on the assumption that the total flowrate for four steamlines is 250 scfh. Therefore, overall deposition has been understated.
See Attachment 10.
Conservatism 10:
The conversion ofdeposited elemental iodine to re-evolved organic iodine is assumed to be instantaneous as opposed to requiring several days.
See Attachment 11.
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Conservatism 11:
Deposition in the drain lines and in the main condenser is neglected.
See Attachments 10 and 11.
References
PSAT 04000U.04 Page 9 of 11 Revision:
1 NUI&G-1465, February 1995 Reference 2:
"STARNAUA,A Code for Evaluating Severe Accident Aerosol Behavior in Nuclear Power Plant Containments: Code Description and Validation and Verification Report", PSAT C101.02, Revision 0, May 1995 Reference 3:
ABB-Combustion Engineering Calculation "TVADOSE: AComputer Program for the Calculation ofBrowns Ferry Advanced Source Term (ABB-Combustion Engineering Proprietary)", 1066-S &T95-C-001, September 1995 Reference 4:
International Commission on Radiological Protection, "Limitsfor Intake of Radionuclides by Workers", ICRP Publication 30, 1979 Reference 5:
Taylor, J., "Proposed Issuance ofFinal NUREG-1465, 'Accident Source Terms for Light-Water Nuclear Power Plants'", SECY-94-300, December 15, 1994 Reference 6:
General Electric Nuclear Energy, "Browns Ferry Nuclear Plant, Calculation of LOCADoses to the Control Room from MSIVLeakage", DRF A00-04146, Section C, Attached to Letter ALJ92049 from A.L. Jenkins (GE Nuclear Energy) to J.L. Kamphouse (TVA)dated August 28, 1992 Reference 7:
DiNunno, J. J., et al., "Calculation ofDistance Factors for Power and Test Reactor Sites", TID-14844, March 1962 Summary ofCalculations Polestar calculations provide the following:
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PSAT 04011H.01 (Attachment 3):
This calculation establishes the overall thermal-hydraulic behavior ofthe containment and calculates the exchange rate between the drywell and the torus airspace (Items 3.10 and 3.11 ofAttachment 2).
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PSAT 04001H.02 (Attachment 4):
This calculation establishes the removal rate ofaerosol and elemental iodine from the containment atmosphere (Items 4.3 and 4.4 ofAttachment 2) and the volumetric leakrate for MSIVleakage (Item 3.23 ofAttachment 2).
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PSAT 04011H.03 (Attachment 5):
P SAT 04000U.04 Page 10 of 11 Revision:
1 This calculation establishes the maximum iodine decontamination factor (ratio oftotal iodine in containment to that airborne)(Items 4.5 and 4.6 ofAttachment 2).
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P SAT 04011H.04 (Attachment 6):
This calculation establishes the scrubbing efficiency ofthe suppression pool (Item 4.2 of ).
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PSAT 04011H.05 (Attachment 7):
This calculation provides radionuclide data not available in the TACTS User's Manual (N.EEG/CR-5106) forItem 1 ofAttachment 2.
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PSAT 04011H.06 (Attachment 8):
This calculation defines the source term forBrowns Ferry based on Reference 1 (Items 2.1 through 2.3 ofAttachment 2).
t
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PSAT 04011H.07 (Attachment 9):
This calculation provides the leakrate directly from the drywell to the environment for the early part ofthe Case 2 dose assessment (when the reactor building internal pressure is not sub-atmospheric)(Item 3.20 ofAttachment 2).
~
PSAT 04002H.08 (Attachment 10):
This calculation provides the removal efficiency for aerosol in the main steamline (Item 4.7 ofAttachment 2).
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PSAT 04002H.09 (Attachment 11):
This calculation provides the removal efBcency for elemental iodine and tellurium in the main steamline (Item 4.7 ofAttachment 2).
I In addition to the above Polestar calculations, the ABB-CE dose calculation 1066-S8cT95-C-002 provides the EAB, LPZ, and control room thyroid, whole body, and (for the control room) skin doses.
This calculation is Attachment 1.
Results
PSAT 04000U.04 Page ll of ll Revision:
1 produces the highest doses and is, therefore, the limitingcase.
Dose Magnitude - rem C'ml Cam2 Control Room - 30 day Thyroid Whole Body Skin 17.9 17.4 0.046 0.045 1.79'.78 EAB-2 hour LPZ -30 day Thyroid Whole Body Thyroid Whole Body 3.16 0.075 5.79 0.282 2.74 0.059 5.55 0.269 Limitingcase contributions are as follows:
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I-131 to control room thyroid dose = 16.64 rem I-133 to control room thyroid dose = 1.13 rem Te-132 to control room thyroid dose = 0.06 rem Other contributors = 0.07 rem
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Ofthe 16.64 rem I-131 thyroid dose in control room:
12.51 rem organic
'.21 rem elemental 0.92 rem particulate
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Non-noble gas, radioiodine, radiocesium, Te-132 (i.e., the "Other") whole body dose is 0.7% ofthe 2-hour EAB total and 0.12% ofthe 30-day LPZ total and is, therefore, confirmed to be negligible.
Conclusions These doses, which have been conservatively calculated, are well within the limitsof 10CFR100 and 10CFR50, Appendix A, GDC-19.