ML11228A228

State-of-the-Art Reactor Consequence Analyses (Soarca); Semi-Annual Briefing for Commission Technical Assistants

ML11228A228
Person / Time
Site:	Peach Bottom, Surry
Issue date:	09/10/2008
From:	NRC/OCM
To:
References
FOIA/PA-2011-0083
Download: ML11228A228 (18)

Text

FFIC US L PRED ION IN MA. N State-of-the-Art Reactor Consequence Analyses (SOARCA)

Semi-Annual Briefing for Commission Technical Assistants September 10, 2008 1

F IA SE NLýY- CIýSIONý FO ATýIONý ý

U I.

LY- P" CIýSI AL IýN AýTI -

Agenda

• Project Status

• Results

• Updates Insights 2

Project Status

• Plan to have the results of Peach Bottom

& Surry in Dec. 2008

• Peer-Review to follow in Jan. 2009 if approved

° Sequoyah analysis in progress F1 ALUSE Y-P ECISI N INFýoOON. 3

Project Status (cont)

SRM-SECY-08-0029

- Approval for dose and spatial truncation methodology (option 6)

- Approval for the external peer review

• Plan completed Revised Statement of Work

- Proposed external peer review

- Uncertainty Analysis

• Parameters have been identified, start date TBD

- Risk Communication ACRS comments

- Staff has taken steps or developed approach to address ACRS comments

" Full scope level 3 PRA

• Seismic impact on EP

• Reporting health effects with LNT and a 5 Rem truncation value

- Plan to provide ACRS written documentation of SOARCA approach, methods, and results for Peach Bottom and Surry (details in next slides)

F1 US NLY EDEI ýNAI OMAT 4

ACRS Comments Full Scope level 3 PRA recommendation

- Staff's view that SOARCA approach is appropriate

" Consistent with objectives

" Proper focus on detailed realistic modeling

-Additional examination of SOARCA sequences

• Comparison with NUREG-1150

. Analysis of sequences with even lower frequency than 10-6 and 10.7 criteria

- Peach Bottom Short-Term Station Blackout Staff conclusions regarding lower frequency sequence demonstrated, by analysis, to be valid F ýA L 0 ýY - REE ECIS ýLI NF ýM ýTI 5

ACRS Comments (cont)

Seismic impact on EP

- Primary influence is on evacuation time estimate (ETE)

- Planned approach is to address by sensitivity analysis Potential LERF impact However, not expected for Peach Bottom and Surry

- Magnitude of release

- NA to Surry ISLOCA 6

Results

• Peach Bottom and Surry base cases (with B.5.b.

measures implemented)

- no early fatalities or latent cancer fatality risk (DBA-like release for Surry Short Term Station Blackout)

• Peach Bottom and Surry sensitivity cases (without B.5.b.

measures)

- no early fatalities; 10-4to 103 conditional individual latent cancer fatality risk 10-10 to 10-9 individual latent cancer fatality risk per sequence

° Staff believes this metriccould be used :for risk communication when the base case results in an environmental release

• Frames consequences in the context of a background risk and safety goals The 10 mrem dose truncation value has no significant impact on the average individual risk (option 6); reconsider ACRS' recommendation of LNT and 5 Rem truncation value F ýLýSEL PýýESIýN ýIýO ý 7

Peach Bottom - STSBO

• Frequency: 1 - 5x 10-7 R-Y

• New case - below SOARCA screening threshold; added to address potential LERF concerns below screening criteria

• Base case with B.5.b. measures implemented -

fission product release was prevented

• Sensitivity Case without B.5.b.measures (no Reactor Core Isolation Coolant System)

- Release begins at -8 hours,

- Radiological Release- 11% iodine, 2% cesium (t=48 hours)

- Not a LERF contributor C LUS N Y-PRONAF 8

Peach Bottom'- STSBO cont.

- no early fatalities Distance Interval Conditional Average Individual likelihood of a LCF (mi) LNT 10 mrem truncation 0-10 9.7x10- 4 0-50 1.6 x 10-4 1.5 x 10-4 1.0 x 0-&4 0-100 8.9 x 105 Reconsider LNT and 5 Rem truncation value?

\Oic ýL ONL -PRýEcISI ýAL ýINF MýA ON - 9

Peach Bottom Consequences CDF Early Conditional LNT - Individual Scenario per R-Y Fatalities Individual LCF risk per LCF risk sequence*

(0 -10 miles) (0 -10 miles)

Long Term Station ito 5 x 10-6 0 3 x 10-4 8 x 10-10 Blackout (LTSBO)

Short Term Station Blackout 1 to 5 x 10-7 0 1 x 10-3 3 x 10-10 Blackout (STSBO)

U.S. average individual risk of a cancer fatality: 2 x 10-3 /year 10

Surry Consequences Conditional LNT- Individual Scenario CDF Early Individual LOF risk per per R-Y Fatalities LCF risk sequence (0 -10 miles) (0 -10 miles)*

LTSBO 1 to 2 x 10-5 0 1 X 10-4 2 x 10-9 STSBO 1 to 2 x 10-6 0 6 x 10-4 8 x 10 -10 STSBO/3 to 5 x 10-7 0 9 x 10-4 4 x 10-10 TISGTR ISLOCAspar 3 x 10-8 0 2 X10- 3 6 x 10-11 ISLOCApra 7 x 10-7 0 2X10-3 1.x 10-9 U.S. average individual risk of a cancer fatality: 2 x 10-3 / year.

ISLOCA - Inter-systems loss of coolant accident 11 TISGTR - Thermally induced steam generator tube rupture

Surry ISLOCA

• Internally initiated event

- Sequence frequency

- Licensee's PRA- 7x10-7 /year

- SPAR - 3x1 0-8 / year (does not meet SOARCA screening criteria of lxl 07/ year)

• Base case Effectively mitigated - operators have sufficient time to switch to unaffected unit's refueling water storage tank (RWST) to prevent core damage

• Sensitivity

- Assumes operators fail to switch to unaffected unit's RWST

- Results in core damage and fission product release via the Safeguards Building QFIk LUS ýN-LYýP DE' 0 LI RýATIO0 12

Sensitivity Analysis

• Break elevation is uncertain

- NUREG-1 150 concluded that the probability of break being uncovered is 0.15 Sequence frequency

- Based on licensee's PRA - 6x10-7 /year (covered),

1x10-7 /year (uncovered)

- Based on SPAR - 3x1 0-8 / year (covered), 5x10-9 / year (uncovered)

• Preliminary results for sequence with break covered

- Release begins at-- 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />

- Radiological Release - 9% iodine, 9% cesium Analysis ongoing for sequence with break uncovered L13

Release Magnitude (%)

12-10-6-

4 LII Iodine 2- I Cesium Sandia Siting Study (SSTI source term)

Iodine - 45%

Cesium - 67%

0FiI E 0O ýR ED SI N1ýAL Iý ORT1 TION 14

Updates / Insights

• Propose truncating fission product releases to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after start of release

- Generally consistent with NUREG-1 150

- Consistent with realistic consideration of anticipated EP measures and capabilities

• Airlift capability if access limited FCILU OLY- ED ISIO FO AON 15

SOARCA Insights

° Because fission product releases are delayed and substantially. smaller, offsite consequences are smaller than previously predicted o No early fatalities; No LERF Contributors

• Average individual latent cancer fatality risks are very low

- Most of the individual latent cancer risk is due to.

doses within the EPA Protective Action Guides and the assumed low dose healtheffects of the LNT dose response model OFFICIAL USE ONLY - PREDECISIONAL INFORMATION 16 1!1

i " , ,

WFF IýU S ý- RE I ýON A ýN OR ýTI SOARCA Insights (cont.)

e Risk to the public from long term exposure is extraordinarily small e Within the Emergency Planning Zone (EPZ)

For the BWR event (LTSBO) freq -3 x 10-6 / year Individual risk of a latent cancer fatality -3 x 10-4 conditional to occurrence of event (LNT assumption)

Absolute LCF risk to individual is -8 x 10-10 / year

- Risk is thousands of times smaller than the NRC safety goal

- Risk is millions of times smaller than all other cancer risks (2 x 10-3 / year)

• Risk outside the EPZ is smaller yet FICI SEQ PRED IS NALI ATI 17

/-

• Questions?

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