ML13196A497

NRC Staff Answer to Motion for Summary Disposition of Contention 4D, Attachment 4D-B

ML13196A497
Person / Time
Site:	Seabrook
Issue date:	07/15/2013
From:	NRC/OGC
To:	Atomic Safety and Licensing Board Panel
SECY RAS
References
ASLBP 10-906-02-LR-BD01, RAS 24824, 50-443-LR
Download: ML13196A497 (39)

Text

NextEra Energy Seabrook, LLC (Seabrook Station, Unit 1)

License Renewal Application NRC Staff Answer to Motion for Summary Disposition of Contention 4D ATTACHMENT 4D-B

NEXTera March 19, 2012 SBK-L-12053 Docket No. 50-443 U.S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 Seabrook Station Supplement 2 to Severe Accident Mitigation Alternatives Analysis NextEra Energy Seabrook License Renewal Application

References:

1. NextEra Energy Seabrook, LLC letter SBK-L-10077, "Seabrook Station Application for Renewed Operating License," May 25, 2010. (Accession Number ML101590099)

2. NextEra Energy Seabrook, LLC letter SBK-L-11001, "Seabrook Station Response to Request for Additional Information, NextEra Energy Seabrook License Renewal Application," January 13, 2011. (Accession Number ML110140810)

3. NextEra Energy Seabrook, LLC letter SBK-L-1 1067, "Seabrook Station Response to Request for Additional Information, NextEra Energy Seabrook License Renewal Application," April 18, 2011. (Accession Number ML1 122A075)

4. NextEra Energy Seabrook, LLC letter SBK-L- 11125, "Supplement to Response to Request for Additional Information - April 18, 2011, " June 10, 2011. (Accession Number MLI 1166A255)

In Reference 1, NextEra Energy Seabrook, LLC (NextEra) submitted an application for a renewed facility operating license for Seabrook Station Unit 1 in accordance with the Code of Federal Regulations, Title 10, Parts 50, 51, and 54. In Reference 2, 3 and 4, NextEra submitted responses to the NRC staffs RAIs.

NextEra Energy Seabrook, LLC, P.O. Box 300, Lafayette Road, Seabrook, NH 03874

United States Nuclear Regulatory Commission SBK-L-12053/ Page 2 The original SAMA was submitted in May 2010 (Reference 1) and was based on Seabrook's base case PRA model of record SSPSS-2006 (model SB2006). In NextEra Letter SBK-L-11001 (Reference 2), the next periodic update to the PRA model was discussed. NextEra has completed the PRA update (SSPSS-201 1) and is providing, in this letter, a supplemental SAMA analysis based on this PRA update.

The License Renewal Application, Appendix E, page F-6 contains a list of acronyms used in this supplement. If there are any questions or additional information is needed, please contact Mr.

Richard R. Cliche, License Renewal Project Manager, at (603) 773-7003.

If you have any questions regarding this correspondence, please contact Mr. Michael O'Keefe, Licensing Manager, at (603) 773-7745.

Sincerely Next ergy Seabrook, LLC.

Paul (YTFreeman Site Vice President Enclosure cc:

W.M. Dean, NRC Region I Administrator J. G. Lamb, NRC Project Manager, Project Directorate 1-2 W. J. Raymond, NRC Resident Inspector A.D. Cunanan, NRC Project Manager, License Renewal M. Wentzel, NRC Project Manager, License Renewal Mr. Christopher M. Pope Director Homeland. Security and Emergency Management New Hampshire Department of Safety Division of Homeland Security and Emergency Management Bureau of Emergency Management 33 Hazen Drive Concord, NH 03305 John Giarrusso, Jr., Nuclear Preparedness Manager The Commonwealth of Massachusetts Emergency Management Agency 400 Worcester Road Framingham, MA 01702-539

United States Nuclear Regulatory Commission SBK-L-12053/ Page 3 NEXTera ENERGY,.A SEABROK I, Thomas A. Vehec , Plant General Manager of NextEra Energy Seabrook, LLC hereby affirm that the information and statements contained within are based on facts and circumstances which are true and accurate to the best of my knowledge and belief.

Sworn and Subscribed Before me this Jq day of March, 2012 Thomas A. Vehec Plant General Manager Notary Pu ic

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis Enclosure to SBK-L-12053 NextEra Energy Seabrook, LLC Supplement 2 to Severe Accident Mitigation Alternatives Analysis

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis 4.2 SUPPLEMENTAL SAMA RESULTS PRA Level ] and 2 QuantitativeResults The core damage frequency (CDF) has decreased from the 2006 results to the 2011 results by approximately 14.5%, from 1.44E-05/yr (SB2006) to 1.23E-5/yr (SB201 1). The large early release frequency (LERF) has decreased by approximately 20%, from 1.1 5E-07/yr (SB2006) to 9.2E-08/yr (SB201 1).

Maximum Averted Benefit The consequences of a severe accident have increased as a result of the revised Level 2 release source term modeling. This has resulted in an increase to the offsite dose/cost risk and offsite property/cost risk despite the reduction in annual core damage and large early release frequencies.

The nominal maximum attainable benefit (MAB) is $3,050,815 (SB201 1). This represents a factor increase of 3.7 over the previous MAB of $818,721 (SB2006). This increase in MAB is primarily the result of higher release category source terms. The original SAMA analysis was based on previous, historical source terms, which were developed from industry source term information and early versions of MAAP for various accident release fractions and accident timing. The new source term assessment provides a state of the art and consistent approach to analyzing accident source terms.

SAMA Sensitivity Assessments Annual Met Data Set The meteorological data sets used in the updated SAMA evaluation are the same as in the original SAMA evaluation and included years 2004 through 2008. Each data set was evaluated to ensure that the data year that provides the maximum dose risk and cost risk is used. Based on the assessment, the met data associated with year 2005 provides the maximum dose risk and cost risk (same as in original assessment) and was chosen as the baseline data set for the updated SAMA.

Meteorology Specification in last SpatialSegment Consistent with the original SAMA evaluation, the updated baseline SAMA evaluation assumes continuous rainfall imposed from 40 to 50 miles from release to force conservative population exposure for base case. The sensitivity case allows the 40-50 mile segment meteorology to follow the onsite meteorology. Elimination of the continuous rainfall assumption reduces the population dose risk to approximately 86% of the baseline and the cost risk to approximately 85% of the baseline. These results are consistent with the sensitivity results observed in the original SAMA study.

Sea-breeze Sensitivity The sea-breeze effect on population dose risk and economic cost risk was re-evaluated similar to the previous analysis described in NextEra Energy's response to RAI #4g ( Reference 2) to account for the new release category source terms. The results of the latest evaluation indicate that the population dose and offsite economic cost risks increase by 0.4% and 0.6% when applying a conservative sensitivity to account for sea breeze effects. The sensitivity of the thermal internal boundary layer (TIBL) lid height was also investigated by specifying a 110 meter height; a decrease 33 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis of 10 meters (from 110 to 100 meters) was found to change the dose and offsite cost risks by 0.8%

and 0.5%. Based on this evaluation and when considering other conservative SAMA assumptions (e.g., perpetual rainfall in the outer ring) the sea-breeze effects do not change the conclusions of the SAMA analysis.

Note - The previous sea-breeze assessment in RAI #4 (Reference 2) estimated sea-breeze effects could result in an increase to the population dose risk by 4%

and economic cost risk by 7%. These previous results were calculated in MACCS2 using the Monte Carlo random bin sampling technique. The revised evaluation summarized above used the MACCS2 sequential hour analysis technique, which provides a more accurate result compared to the Monte Carlo bin sampling technique. Thus, the latest results are shown to be less than previous results despite of the increase in release category source terms.

Release Category LE4 Sensitivity to No Evacuation As summarized in Section 3.1, Release Category LE4 is used to represent extreme seismic events where it is assumed that evacuation could be delayed beyond 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> and therefore, the release is assigned to LERF. The Level 3 base case population dose and economic cost consequences of LE4 are determined assuming normal evacuation occurring at the General Emergency declaration beginning at core uncovery. If no evacuation is assumed, the LE4 dose consequence increase is less than 1% (from a total base case dose of 1.11 E+07 person-rem to 1.12E+07 person-rem). The overall economic cost consequence does not change.

The LE4-specific dose consequence during the early phase of the release (exposure to the passing plume) for the no-evacuation scenario is 9% greater than the base case (with evacuation). However, the early phase dose is only 16% of the total LE4 dose consequence. The remaining 84% of the dose consequence occurs during the late phase and is a result of long-term exposure to the plume, independent of evacuation. Compounding the relatively small consequence of no-evacuation, with the relatively small portion of the total dose that can be affected by the action to evacuate results in a negligible affect (<1%) on the total LE4 dose consequence.

Sensitivity to Variation in Other Level 3 Parameters The sensitivity of the updated SAMA results to variations in other Level 3 parameters is expected to be consistent with previous sensitivity results. The previous Level 3 sensitivity cases included variations in release height, release heat, building wake effects, and evacuation speed, preparation, warning time and population fraction. Although the radionuclides released in the updated SAMA were different amounts compared to the original evaluation, the physical surroundings such as meteorology, population distribution and economy are unchanged. Therefore, the conclusions drawn from the original Level 3 sensitivity evaluation are representative of the updated SAMA evaluation.

Sensitivity to Variation in Discount Rate The nominal (baseline) cost-benefit assessment considers a "nominal" discount rate of 7%. Cost-benefit sensitivity to the discount rate is considered at 3% (conservative discount rate) and 8.5%

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis (best estimate discount rate). The nominal 7% rate and the conservative 3% rate are consistent with the NEI 05-01 industry guidance. The best estimate rate of 8.5% is specific to Seabrook Station and is consistent with the original Seabrook SAMA evaluation. The 3% conservative discount rate results in an increase the cost-benefit above the nominal, whereas the best estimate rate of 8.5%

provides a cost-benefit slightly lower than the nominal rate. No new potentially cost-beneficial SAMAs where identified as a result of the 3% and 8.5% sensitivity calculations. The cost-benefit worth of all SAMA candidates at the 3% conservative discount rate is shown to be less than the SAMA cost-benefit worth when considering the uncertainty (upper bound) benefit.

Sensitivit to Extended Period The nominal cost-benefit assessment considers a nominal benefit period of 20 years. The SAMA cost-benefit sensitivity to an extended period was explored to account for possible near term approval of the renewed license. Consistent with the original SAMA evaluation, an extended period of 41 years is used to represent the total period of the extended/renewed operating license. Based on this sensitivity study, the cost-benefit worth (MAB) during the extended period is a factor of -1.3 greater than the nominal MAB, but significantly less than the upper bound (95th percentile) MAB.

The cost-benefit worth of all SAMA candidates assuming the 41 year extended period is shown to be less than the SAMA cost-benefit worth when considering the uncertainty (upper bound) benefit.

Sensitivity to Upper Bound Accident Costs The nominal cost-benefit assessment considers the mean (best estimate) core damage/accident release frequencies derived from the Seabrook SB20 11 PRA. To account for upper bound uncertainty in the PRA model results, the best estimate accident costs are multiplied by an uncertainty factor of 2.35 to represent the cost-benefit associated with the 95th percentile (upper bound) accident release impacts. The increase factor of 2.35 is based on the ratio of the best estimate CDF mean value of 1.23E-05/yr to the CDF upper bound (95th percentile) value of 2.86E-05/yr.

This approach is consistent with the NEI 05-01 industry guidance. The upper bound cost-benefit of each SAMA candidate is considered whenjudging the candidate as being potentially cost-beneficial.

Although this approach is consistent with NRC expectation for identification of potentially cost-beneficial SAMAs, it is noted that final determination of cost and benefit would include a more realistic assessment of both the cost of a specific modification and its associated value in risk reduction.

Sensitivity to IncreasedSeismic Risk The nominal and upper-bound cost-benefit values of each SAMA candidate are increased by a factor of 2.1 to account for possible higher seismic risk. The basis for the 2.1 multiplier is discussed in Section 4.1 of this report. This sensitivity approach is consistent with NRC expectations for identification of potentially cost-beneficial SAMAs.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis PotentialCost Beneficial SAMAs The four SAMA candidates that were identified as potentially cost-beneficial in the previous analysis remain as potentially cost-beneficial in the supplemental analysis. Three new potential cost-beneficial SAMAs are identified for further consideration within Seabrook's Long Range Plan (LRP) system. The potentially cost-beneficial severe accident mitigative alternatives identified do not involve aging management of passive, long-lived systems, structures, or components during the period of extended operation. All previous (p) and new (n) potentially cost beneficial SAMAs are identified in the following table.

Seabrook Station - Potential Cost-Benefit SAMAs SAMA # Description fPotential Benefit 157 Independent AC power source for battery Reduce the risk of core damage from long-(p) chargers (e.g., portable generator to facilitate term SBO sequences by extending battery timely charging of station batteries), life to allow more time to recover offsite/onsite power.

164 Method to refill the Condensate Storage Tank Reduce the risk of long term core damage (n) (CST) from alternate water sources (e.g., modify sequences that rely on long term SG makeup 10" condensate filter flange connection to via feedwater and CST suction source.

facilitate timely CST makeup from other sources such as firewater or alternate pump via hose connection).

165 Method to refill Reactor Water Storage Tank Reduce the risk of containment failure and (p) (RWST) from firewater during containment release during long term containment injection (e.g., modify 6" RWST flush flange injection sequences that would benefit from connection to facilitate timely firewater makeup additional makeup.

capability).

172 Replace existing RCP seal design with improved Reduce risk of core damage from transients (n) low leakage seal (e.g., evaluate installation of sequences with seal cooling hardware a "shutdown seal" developed by Westinghouse). failures, which result in RCP seal LOCA events.

192 Install flow limiting device in the fire protection Reduce the risk of core damage from internal piping located in the Control Building to limit flood sequences resulting from a postulated flood consequence of major pipe break (e.g., pipe break in Control Building fire protection install flow orifice), piping.

193 Replace outboard containment isolation valve Reduce the risk of release during SBO /

CS-V- 167 with a valve design that is independent seismic sequences that lead to core melt; of AC power (e.g., replace existing MOV with an improve reliability of containment isolation AOV). of RCP seal water return line.

195 Hardware changes to improve PCCW Reduce risk of core damage and release due (n) temperature control reliability - update of existing to sequences involving loss of PCCW equipment or provide additional redundancy in cooling function.

instrumentation / controls 36 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis 4.3 SUPPLEMENTAL SAMA EVALUATION RESULTS TABLES The cost-benefit assessment of each previous Phase II SAMA candidate is provided in Table 1. The cost-benefit assessment of each of the top 15 dominant BE-related SAMA candidates and IE-related SAMA candidates is provided in Table 2. The expected SAMA cost and bases are provided in Tables 1 and 2. SAMA candidates that were previously identified as "intent met" in the initial submittal or in subsequent RAI responses are not reviewed further in this supplement.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB & PHASE 2 SAMA REVIEW SBIK  % Risk Total Benefit () Expecte Potential PR ae Reduction Baseline (with 2.1 d SAMA

.SAMVA Ipoe nt Description PR aemultiplier) ~ cost Evaluation Number Iirvmn

- -- CDF Pop Internal With

_______ ", .:"":.':i::  : .  :,. Dose External Uncert. ________-_"_"_.______________"_*_: ________-_" ____

Not cost beneficial. The original PRA case NOSBO and recent PRA case NOSBO1 both conservatively assume elimination of all station blackout events by assuming Replace lead- Extended DC 224K 525K guaranteed success of both EDGs for all events and independent of all support systems 2acid batteries power capability NOSBO1 22 (470K) (11.M 1 .75M (control power, cooling, etc.)

with fuel cells during an SBO

Cost of physical plant modifications and analysis judged comparable in scope and I____Icomplexity to 'providing additional DC battery capacity" (Davis Besse AC/DC-01).

Not cost beneficial. The original and recent PRA case NOLOSP conservatively Install an Reduced assumed elimination of all LOSP events.

13 additional, buried probability of NOLOSP 18 17 531K 1.24M >3M Cost of physical plant modifications and analysis judged comparable in scope and off-site power loss of off-site (1.2M) (2.7M) complexity to "Burying off-site power lines" (Callaway 24). Cost of installing buried, source power alternate power source expected to significantly exceed benefit. Reduction in seismic risk would not be significant unless offsite power source is seismically rugged.

Not cost beneficial. The original PRA case NOSBO and recent PRA case NOSBO1 both conservatively assume elimination of all station blackout events by assuming Increased guaranteed success of both EDGs for all events and independent of all support systerr Install a gas availability of on- NOSBOs 22 224K 525K * (control power, cooling, etc.) Reduction in seismic risk would not be significant unless turbine generator siteaity AC power of on- (470K) (1.1 M) 2M gas turbine is seismically rugged.

Cost of physical plant modifications and analysis judged comparable to other plants that presently do not have these features (Davis Besse AC/DC-1 4). Some of the potential benefit of this SAMA would be realized with SAMA #172, RCP shutdown seal.

Not cost beneficial. The original PRA case NOSBO and recent PRA case NOSBO1 both conservatively assume elimination of all station blackout events by assuming Increased guaranteed success of both EDGs for all events and independent of all support systems Improve availability of 224K 525K (control power, cooling, etc.)

16 uninterruptible power supplies NOSBO1 22 6 (470K) (1.1 M) >2M Cost of engineering and implementing this upgrade is based on Seabrook engineering power supplies supporting front- estimate.

line equipment It is noted that due to the importance of improving reliability of uninterruptable power supplies, an action item has been entered into the Long Range Plan to assess future upgrade to the ELGAR inverters.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABRo6K - MAB & PHASE 2 SAMA REVIEW

%Tis otal Benefit($ Expecte SAMA Potential R1ucio iiaelinel(with 2.1 d sAMA Eauto NumbeA mrvmn Description PRA Case .multiplier) Costaio

-Number - ..-....

.- CD- PPop. internal n**Dose 'External& Uncert.

With ".

Not cost beneficial. The original PRA case NOSBO conservatively assumed eliminatior of all station blackout events by assuming guaranteed success of both DGs for all events and independent of all support systems (control power, cooling, etc.). The updated PRA case DGSW assumes success of SW components (valves) that are associated with DG cooling and alignment of the SW system (ocean and cooling Add a new Increased diesel tower). Guaranteed success of these components and the resulting increase in SW 20 backup source of generator DGSW <1 1 25K 53K 2M reliability is representative of the DG cooling water reliability gained from installing a diesel cooling availability (59K) (124K) backup source of cooling water. Insights from this analysis are that the existing arrangement of SW cooling to the DGs is of a reliable design; and making the DGs less dependent on SW does not provide a significant risk reduction because other train-specific components, such as ECCS pumps, also depend on SW cooling.

Cost of physical plant modifications and analysis judged comparable to other plants thai presently do not have these features (Grand Gulf 10).

Not cost beneficial. The original and recent PRA case NOLOSP conservatively Bury off-site Improved off-site power reliability NOOP1 7 531K 1.24M assumes elimination of all loss of offsite power events. Burying offsite power lines to 24 linesNOLOSP power 18 17 ( 1.2 4M >3M the station is judged not practical and cost is expected to significantly exceed benefit.

power lines during severe (1.2M) (2.7M) weather Cost of physical plant modifications and analysis judged comparable in scope and complexity to "Burying off-site power lines" (Callaway 24).

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE. 1 - SEABROOK - MAB:& PHASE12 SAMA REVIEW

... . Risk Total Benefit () Expecte SBK impKePe-ehto.:Baseline (wWh .2.1 dSAMA SAMA Iproteentia Description PRA Case Rdcin multiplier)" Cost Eauto Number Inera & it CDF Pp nenl Wt Dose External Uncert. *"

Not cost beneficial. The original PRA case LOCA02 conservatively assumed guaranteed success of all high head and intermediate head injection pumps (charging and SI pumps.) Therefore, the benefit of installing a single, independent, backup injection system was judged conservatively high. A more realistic PRA Case CSBX assumes that CS division B of high pressure injection (CSB) is independent and does not rely on support systems (independent of AC / DC power, cooling, etc.). This case is used to represent a "parallel" pump with same suction as CS-B. Installation of an independent, active or passive injection system is judged not practical and cost is expected to significantly exceed the conservative benefit. Given the seismic ruggedness of the existing injection system(s), any new/additional system would need Install an Improved to be equally rugged to significantly reduce plant risk. Including seismic ruggedness in independent prevention of 1.1M 2.5M the design would further increase cost.

25 active or passive high pressure core melt (2.3M) (5.3M) 8.8M Cost of physical plant modifications and analysis judged comparable to other plants thai injection system sequences presently do not have these features (Grand Gulf 20). This improvement was i spreviously estimated at greater than $2 million dollars in the Pilgrim License Renewal application. In the Duane Arnold License Renewal application, the Pilgrim estimate waE judged to be low and used a $20 million estimate based on similar modification experience. In addition, Grand Gulf SAMA #20 estimated the cost of a similar plant change at >$8.8M. Given these industry estimates and based on the Seabrook plant design, the cost for SAMA implementation would be expected to be in the range of $6 tc

$1OM or more. These estimates significantly exceed the upper bound sensitivity benefil and a more refined estimate is not warranted.

It is noted that some of the potential benefits of this SAMA would be realized with SAM

1. 172, RCP shutdown seal.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB & PHASE 2 SAMA REVIEW Total Benefit (~Expecte SBK ,.% Risk Baseline (with 2.1 dSM SAMA._ I..mPotential provem ent .  :: -. .. :

Description  :: ..PRA Case: Reduction :m ultiplier) ° mutipier) SAMAt: :., .

"Cost..  :=° * : " ..  :-  !" va at n Evaluation = : .

Number ImprovementC Internal & With naCDF-Pop. C 7 Dose External Uncert.

Not cost beneficial. The original PRA case LOCA02 conservatively assumed guaranteed success of all high head and intermediate head injection pumps (charging and SI pumps.) Therefore, the benefit of installing a single, independent, backup injection system was judged conservatively high. A more realistic PRA Case CSBX assumes that CS division B of high pressure injection (CSB) is independent and does not rely on support systems (independent of AC / DC power, cooling, etc.). This case is used to represent a "parallel" pump with same suction as CS-B. Installation of an additional injection system is judged not practical and cost is expected to significantly exceed the conservative benefit. Given the seismic ruggedness of the existing injection Provide an system, any new/additional system would need to be equally rugged to significantly Providehanh Reduced reduce plant risk. Including seismic ruggedness in the design would further increase additional high frequency of cost.

26 pressure core melt from CSX22 3 i11M 2.5M 8.8M 26 injection pump small LOCA and CSBX 22 34 (2.3M) (5.3M) 8.8m Cost of physical plant modifications and analysis judged comparable in scope and with independent SBO sequences complexity to other plants that presently do not have these features (Grand Gulf 20).

diesel This modification was assumed to be the equivalent of adding one new high pressure injection pump powered by a diesel rather than an electric motor with a suitable injection path and suction source. In the Duane Arnold License Renewal application, the cost of this was one half the cost of replacing pumps discussed in SAMA 25 above, the cost would be $10 million. In addition, Grand Gulf SAMA #61 estimated the cost of a similar plant change at >$6.4M and >8.8M for Grand Gulf SAMA #20. Given these industry estimates and based on the Seabrook plant design, the cost for SAMA implementation would be expected to be in the range of $6M to $1 OM or more.

It is noted that some of the potential benefits of this SAMA would be realized with SAWA

1. 172, RCP shutdown seal.

Not cost beneficial. The original PRA case LOCA03 conservatively assumed elimination all low pressure injection failures including injection pump trains, suction, accumulators and low pressure recirculation. A more realistic yet conservative PRA case for LOCA03 was performed to better address this SAMA, which is focused on Add diverse low adding diversity in for injection. The revised PRA case assumes guaranteed success o1 28 pressure Improve injection 68K 160K >11M the low head "injection" function provided by the pump trains when support systems are 2nepre system- capability LOCA03 2 2 (143K) (336K) available. Accumulators and containment recirculation are assumed to be subject to injection srandom failures.

Cost to engineer and Install an additional low pressure injection system is based on Seabrook previously reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TAL.1 ABLE -SEABROO KEA

- MA13MAREVIEW:

MABI&PHASE2 P SAM EViEW" i  :* ~. . .. i .

SBKRsk Total Benefit Cs) Ex~pects A Potential Reduction n Baseline (with2.l<dSAMA "PRA Case SAMADescription multiplier) C . Evaluation Number Improvement "PCost NumCDF Pop. internal & With

__________.... "Dose External Uncert.

Not cost beneficial. The original and recent PRA case LOCA04 conservatively assume guaranteed success of the RWST volume as a continuous source of water for ECCS.

Therefore, the benefit of throttling low pressure injection to extend the time to RWST Throttle low depletion for medium or large break LOCA events is conservatively high. The current pressure system valves and controls do not allow throttling.

injection pumps earlier in medium Extended reactor 312K 731 K Cost to engineer and install is based on two trains, replacing manual valves with new 8" 35 or large-break water storage LOCA04 13 10 (655K) (1.53) >3M MOVs including control system design and associated hardware and cabling. Design LOCAs to tank capacity change to include a revised LOCA and Containment analysis. Additional analysis maintain reactor would be required to verify ECCS flow balance and NPSH for low, intermediate and water storage high head SI pumps. The implementing modification would need to address design anc tank inventory licensing basis changes as well as post mod testing to validate required flow balance is achieved.

Not cost beneficial. The original PRA case LOCA02 conservatively assume guaranteed success of all high head and intermediate head injection pumps (charging and Sl pumps.) Therefore, the benefit of replacing two electric motor pumps with diesel-driven Reduced pumps was conservatively high. Of the four SI pump trains, the intermediate head common cause pumps contribute slightly more to the CDF than the high head SI/charging pumps. A failure of the more realistic PRA Case DSIPP case assumes that the existing intermediate head SI Replace two of safety injection pump trains do not rely on AC power, but continue to rely on DC control power and the four electric system. The room cooling. This is judged representative of replacing the SI pump motors with diesel safety injection intent of this <1K <1K engines. The high head SI/charging pumps are assumed to remain dependent on AC 39 pumps with SAMA is to DSIPP <1 0 (<1 K) (<2K) >5M power. Installation of diesel-driven pumps in place of the existing motor-driven pumps diesel-powered provide diversity is judged not practical and cost is expected to significantly exceed the conservative pumps within the high- benefit. Given the seismic ruggedness of the existing injection system, any and low-pressure new/additional equipment would need to be equally rugged so as to not impact the safety systems injections current seismic design basis. Including seismic ruggedness in the design would further increase cost.

Cost to engineer and Install diverse pump drivers is based on Seabrook previously reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOK - MAB & PHASE 2 SAMA REVIEW.

SK .Potential Description .dCase

% Risk. Total Benefit () Expecte

. Reduction: Baselie(t2 d SAMA Numbe Improe nt Decito PRACas multiplier) Cost Evaluation CDF Pop.- Internal With Dose :External Uncert.

• __________.. _______._..-_.________________"___"_______..

Allows low pressure emergency core Not cost beneficial. The original and recent PRA cases LOCA01 conservatively Create a reactor cooling system 27K 64K assume elimination small LOCA events.

41 coolant depress injection in the LOCA01 2 1 >1M system event of small (57K) (134K) Cost to engineer and install an RCS depressurization system is based on Seabrook LOCA and high- previously reported estimate.

pressure safety injection failure Add redundant Not cost beneficial. The original and recent PRA cases SWO1 conservatively assume DC control Increased 11K 26K that the SW pumps are not dependent on DC power.

power for SW availability of SW (24K) (55K) Cost to engineer and install an independent DC power system for the SW pumps is pumps based on Seabrook previously reported estimate.

Not cost beneficial. The existing ECCS pump "motors" are air cooled motors, which relý on ventilation cooling for long term ambient room cooling. Ventilation cooling is provided by the Emergency Air Handling System (EAH) which cooled by CCW. The ECCS pump components also rely on CCW cooling (for example lube oil cooling, stuffing box cooling, etc.) The original and recent PRA case CCW01 conservatively assume guaranteed success of the component cooling water (CCW) systems to assess ReplaceElimination of the possible benefit of eliminating the ECCS pump dependence on CCW (room cooling pump motors ECCS 919K 2.15M and pump cooling). However, because CCW contributes is an important system that 44 with air-cooled dependency on CCW01 14 31 (1.93M) (4.6M) >6M contributes to the decay heat removal function, the benefit calculated with case CCW01 motorscomponent motorscooling system is highly conservative.

Cost to engineer and implement design modifications to replace the ECCS pumps with a design that does not depend on CCW (if even practical) is estimated greater than

$6M. This estimate is based on plant modifications judged to be of comparable yet less scope and complexity to SAMA #39, replacing ECCS pumps ($5M). It is also likely that modifications to room ventilation systems would still be needed at a cost of $1 M (similar to SAMA #80) to achieve full benefit.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB &-PHASE 2 SAMVA REVIEW B% %Risk >Total Benefit(S Expecte SAA mb Potential Improvemoent Decito D R aeemultiplier)Reduction Baeie(ih21 d Cost SAMA Evaluation NuDFe Pop. Internal & With Dose External Uncert.._"_________________-________-_..... .__________________________:_________

Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha CS division B of high pressure injection (CSB) is independent and does not rely on Install an Reduced support systems (independent of AC / DC power, cooling, etc.). This case is used to independent indepndent frequency core damageof represent a "parallel" pump with same suction as CS-B.

reactor coolant1.04M 2.45M >6.4M Cost to engineer and implement plant modifications and analysis judged comparable in 55 pump sealsystem, injection compont comont(2M) CSBX 28 34 5.) scope and complexity to "installing a backup water supply and pumping capability" injetio sytem coponet (.2M (52M)(Grand Gulf #61). Grand Gulf SAMA #61 estimated the cost of a similar plant change a with dedicated withdediated service cooling water, or >$6.4M. In addition, the Duane Arnold License Renewal application, the cost of this diesel service wat was one half the cost of replacing pumps discussed in SAMA 25 above, the cost would station blackoutbe$0mlin be $10 million.

It is noted that some of the potential benefits of this SAMA would be realized with SAMP

1. 172, RCP shutdown seal.

Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha Reduced CS division B of high pressure injection (CSB) is independent and does not rely on Install an frequency of support systems (independent of AC / DC power, cooling, etc.). This case is used to independent core damage represent a "parallel" pump with same suction as CS-B.

reactor coolant from loss of 1.04M 2.45M >6.4M Cost to engineer and implement plant modifications judged comparable in scope and 56 pump seal component CSBX 28 34 (2.2M) (5.2M) complexity to "installing a backup water supply and pumping capability" (Grand Gulf without service water, #61). Grand Gulf SAMA #61 estimated the cost of a similar plant change at >$6.4M.

dedicated diesel but not a station The cost of installing an independent seal injection system with or without a dedicated blackout diesel is expected to significantly exceed benefit. Refer above to SAMA #55.

It is noted that some of the potential benefits of this SAMA would be realized with SAMA

1. 172, RCP shutdown seal.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK:-.MAB &,PHASE 2zSAMA REVIEW

% Risk Total Benefit ($) Expecte S_.- Potential - - l Cs Reduction Baseline(t. 2.1 dS .".A Evaluation AnA .Im.provement  : Description PRA""uaseý " multiplier) Cost Number CF Pop., internal & With Dose External Uncert.

Not cost beneficial. The original PRA case CCW01 conservatively assumed guaranteed success of the component cooling water (CCW) systems to provide heat removal. Thus, the benefit of installing an additional CCW pump was conservatively high. A more realistic PRA Case CCABCD assumes that all of the CCW pumps are Reduced guaranteed success when their AC and DC power support systems are available. This Install an likelihood of loss case is used to represent the benefit of an additional "parallel" CCW pump connected additional of component 335K 785K to the system. Seabrook has four CCW pumps. Adding an additional pump will not 59 component cooling water PCCABCD 4 11 >6.1M significantly reduce plant risk due to common-cause failure considerations and cooling water leading to a (704K) (1.7M) limitations in divisional power.

pump reactor coolant Cost to engineer and implement modifications for additional pump judged comparable in scope and complexity to "adding a service water pump" at other plants that presently do not have these features (Columbia SAMA CW-07 )

It is noted that some of the potential benefits of this SAMA would be realized with SAMW

1. 172, RCP shutdown seal.

Reduced chance Install a digital of loss of main 3.05M 7.15M Not cost beneficial based on inspection of the MAB.

65 feed water feed water MAB (6.41M) (15.0M) 30M Cost to engineer and implement installation of the digital feedwater control upgrade is upgrade following a plant based on Seabrook previously reported estimate.

trip Provide a passive, Reduced Not cost beneficial based on inspection of the MAB. A passive heat removal system secondary-side potential for core 3.05M 7.15M using air as the ultimate heat sink would be extremely large.

77 heat-rejection damage due to MAB (6.41M) (15.OM) 15M loop consisting loss-of-feedwater Cost to engineer and implement installation of large passive air cooling system is far in of a condenser events excess of the attainable benefit.

and heat sink Not cost beneficial. The original PRA case FW01 conservatively assumed elimination Replace existing of all loss of feedwater initiating events including all reactor trip events, whether or not pilot-operated the trip events were the result of a loss of feedwater. A more realistic PRA case PORV relief valves with Increased assumes guaranteed success of the PORVs. This case is used to represent a change larger ones, such probability of 1.7K 4.1K in PORV success criteria to reflect larger capacity valves. The cost of replacing the 79 that only one is successful feed PORV <1 0 (4K) (9K) >2.7M PORVs to increase capacity and improve feed and bleed performance is expected to required for and bleed significantly exceed benefit.

successful feed Cost to engineer and implement hardware design changes and replacement of PORVs and bleed judged comparable to other plants that presently do not have these features (Calvert Cliffs SAMA #77).

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SBK-L-12053 NextEra Energy Seabrook, LLC .

Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEAB.ROOK -" MAB &,PHASE 2 SAMAREVIEW ik Total Benefit () Expecte SK Potential Reduction Baseline (with21 dSM SAMVA - ,cindSM mpro. ement  : Description PRA Case ultiplier)

M.. Cost Evauaton Number Pop. Internal With 7 Dose External Uncert. _____________"_______________'__________...________"____________*

Increased Not cost beneficial. The original and updated PRA case HVAC2 conservatively assume Provide availability of no HVAC dependency for CS, SI, RHR and CBS pumps.

redundant train avaiabilty7o 80 or means of components HVAC2 3 5 (320K) (750K) >1M Cost to engineer and implement redundant ventilation design modification judged ventilation dependent on comparable to other plants that presently do not have these features (Callaway SAMA room cooling #80).

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOK - MAB &PHASE2 SAMA REVIEW

% Risk Total Benefit () Expecte SIBIK dcto Baseline (with 2A1 dSM SAMA Ptnil Description> PRA Case rnlipir Cos Evlato Improvement Cos PoP. Internal With Number

_____Dose External Uncert.

Create ability to switch emergency Continued fan Not cost beneficial. The original and updated PRA case OEFWVS and OEFWV 84 fa oe room feedwater upy operationa in a OEFWVS <1 0 <1K

2) <$2K (4) >250K conservatively assume no HVAC dependency for EFW pumps.

fan power supply station blackout (2K) (4K) Cost to engineer and implement HVAC system design changes to allow for DC power to station supply is based on Seabrook previously reported estimate.

batteries in a station blackout Not cost beneficial. The original PRA case CONT01 conservatively assumed the containment does not fail due to overpressure. A revised PRA Case CONTX1 assumeE that one division of Containment Building Spray CBS (including spray injection, containment recirculation, and heat removal) does not depend on AC/DC power or Install a passive Improved 1.2M 2.7M PCCW support systems except for initiation signal. This case more realistically spra sytement rcntabiinmnty C(2.5M) (5.7M) 10M represents the potential risk reduction benefit that might be provided by installation of spray system spray capability an independent division of containment spray.

Cost to engineer and implement passive containment heat removal system judged comparable in scope and complexity to plants that presently do not have these features (Callaway SAMA #91).

Not cost beneficial. The original PRA case CONT01 conservatively assumed the containment does not fail due to overpressure. It is noted that the Seabrook Station design includes the Containment On-line Purge (COP) and Combustible Gas Control Increased decay (CGC) systems, which can function to vent containment during an accident after all heat removal other means of containment decay heat removal have failed. Use of these systems to Install an capability for depressurize containment to the environment is included as a severe accident strategy 93 unfiltered, non-ATWS XOVNTS 39K 92K >$3M in the Seabrook Severe Accident Management Guideline SCG-2. Containment venting hardened events, without (82K) (193K) using the COP system is currently credited in the Level 2 PRA as a means of preventin, containment vent scrubbing over-pressure containment failure when support systems are available. The COP and released fission CGC systems discharge pathways are to the plant stack (located at the top of products containment) via a combination of pipe and rugged ductwork and fan/filter enclosures.

Cost to engineer and implement vent to allow decay heat removal capacity is based on Seabrook previously reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK -MAB & PHASE 2 SAMA REVIEW

% Risk Total Benefit () Expecte BK Potential Reduction Baeie(ih~ d SAMA Eauto NumbeA Number mrvmn Description PRA Case. u multiplier),-' Cost.Evlato PpI nternal& With

_____ __________ __________Dose 'External. -Uncert..

Not cost beneficial. The original conservative PRA case CONT01 assumed elimination of containment failure events due to overpressure. The context of this SAMA is to eliminate containment overpressure failure events by removing decay heat from Install a filtered Increased decay containment via a filtered vent which would retain fission products. A more realistic containment vent heat removal PRA Case CONTXl assumes that one division of Containment Building Spray CBS to remove decay capability for (including spray injection, containment recirculation, and heat removal) does not 94 heat. Option 1: non-ATWS CONTX0 40 1.2M 2.7M >7.8M depend on AC/DC power or PCCW support systems except for initiation signal. This Gravel Bed events, with (2.5M) (5.7M) case is used to represent the potential risk reduction benefit that might be provided by Filter; Option 2: scrubbing of installation of a filtered vent to prevent containment overpressure failure while retaining Multiple Venturi released fission some of the fission products.

Scrubber products Cost to engineer and implement decay heat capacity filtered vent judged comparable to other plants that presently do not have these features (Calvert Cliffs SAMA 12 provided an estimate of $5.7M in 1998, escalated to $7.8M in 2012).

Provide post- Reduced Not cost beneficial. The original and updated PRA case H2BURN conservatively accident likelihood of 18K 43K assume that hydrogen burns and detonations do not occur.

96 containment hydrogen and H2BURN 0 1 >100K inerting carbon monoxide (39K) (90K) Cost to engineer and implement a containment inerting system is based on Seabrook capability gas combustion previously reported estimate.

Not cost beneficial. The context of this SAMA is to eliminate or reduce containment overpressure failure events by adding reinforcement to containment. The original PRA case CONT01 conservatively assumed the containment does not fail due to overpressure. A more realistic, yet still conservative PRA Case CONTX1 is used to Strengthen estimate the risk benefit associated with strengthening containment. The new PRA primary/secondar Reduced case CONTX1 assumes one division of Containment Building Spray CBS (including y containment probability of 1.2M 2.7M spray injection, containment recirculation, and heat removal) does not depend on (e.g., add ribbing containment CONTX1 0 40 (2.5M) (5.7M) 11.5M AC/DC power or PCCW support systems except for initiation signal. This case more to containment over- realistically represents a reduction in the containment pressure challenge that might be shell) pressurization realized by further strengthening of the containment shell itself. It is noted that the installation of structural support members sufficient enough to gain further design pressure margin to the containment building is judged not practical at Seabrook Station.

Cost to engineer and implement installation of reinforcing steel to strengthen containment is estimated at >$11.5M for design, materials and installation.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1; - SEABROOK -~MAB & PHASE. 2 SAMA-REVIEW S"  :" R isk Total Benefit ($) Expecte.

SAA 'Potential Reduction BaselineB(with 2.1.d.SAMA SAVADescription PRA Case m.rultiphier)- Cs Evaluation Number Improvement Wt CDoopsttral Dose External Uncert.

Not cost beneficial. The context of this SAMA is to eliminate or reduce containment release events by adding a system to maintain evacuation (negative pressure) in the containment. It is noted that Seabrook Station already has an enclosure building around the primary containment building, which is maintained in a negative pressure condition. The original PRA case CONT01 conservatively assumed the containment Construct a does not fail due to overpressure. A more realistic PRA Case CONTX1 is used to building to be Reduced estimate the risk benefit associated with improvements to the enclosure building to connected to probability of 1.2M 27M make it more robust relative to severe accident challenges, such as adding an 102 primary/sec. containment CONTX1 0 40 56.7M additional building with filtration system. The new PRA case CONTX1 assumes one containment and over- (2.5M) (5.7M) division of Containment Building Spray CBS (including spray injection, containment maintained at a pressurization recirculation, and heat removal) does not depend on AC/DC power or PCCW support vacuum systems except for initiation signal. This case more realistically represents the postulated reduction in the release challenge that might be realized by an evacuation building to capture releases.

Cost to engineer and construct a new building adjacent to containment with ventilation systems capable of maintaining a negative pressure is estimated at greater than $56M for design, materials and installation.

Not cost beneficial. The original and updated PRA Case OLPRS and OLPR Delay conservatively assume guaranteed success of the operator action to complete/ensure containment Extended reactor the RHRPLHSI transfer to long term recirculation during large LOCA events. The results 105 spray actuation water storage OLPR 3 0 11.7K 27.4K >100K of this case study show that the operator action does not contribute significantly to core after a large tank availability (25K) (58K) damage frequency.

LOCA Cost to engineer and implement control circuitry to delay containment spray actuation for large LOCA is based on Seabrook previously reported estimate.

Not cost beneficial. The original and updated PRA case LOCA04 conservatively assume guaranteed success of the RWST volume as a continuous source of water for ECCS. Therefore, the benefit of throttling containment spray flow to extend the time to Extended time RWST depletion is conservatively high. The cost of engineering analysis, installation of over which water the proper valves, control systems, etc. to accomplish this SAMA is expected to Install automatic remains in the significantly exceed the conservative benefit.

containment reactor water 106 spray pump storage tank, LOCA04 13 10 312K 731K >3M Cost to engineer and implement automatic flow throttling control system is estimated at header throttle when full (656K) (1.54M) greater than $3M. This assumes that both LOCA and Containment Mass Energy valves containment calculations need to be performed. Additional analysis would be required to verify spray flow is not ECCS flow balance and NPSH for low, intermediate and high head SI pumps. The needed implementing modification would address design and licensing basis changes as well as post mod testing to validate required flow balance is achieved. Pending review of the throttling capability of existing system valves, hardware changes may be necessary to achieve the desired results.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1.- SEABROOK - MAB & PHASE 2 SAMA REVIEW SBK SBK Potential

_ . .u..i ~~~%

Risk Ttlenft()

,:Baseline (With 2.1 Expecte d SAMA SAMA .mrvmn Description PRA Case Reduction mutiler) Cost Evaluation.

Not cost beneficial. The context of this SAMA is to eliminate containment overpressure failure events by adding a redundant containment spray system. The original conservative PRA case CONTX1 assumed that a division of containment building spray (CBS) was guaranteed successful. A more realistic PRA Case CONTX1 assumes that one division of Containment Building Spray CBS (including spray injection, containment Install a Increased recirculation, and heat removal) does not depend on AC/DC power or PCCW support 107 redundant containment heat CON-Xl 40 1.2M 2.7M >10M systems except for initiation signal. This case is used to represent the potential risk ccontainment removal ability (2.5M) (5.7M) reduction benefit that might be provided by installation of an additional redundant spray spray system system.

Cost to engineer and implement redundant spray system is estimated at greater than

$10M. This is based on the cost of physical plant modifications and analysis judged comparable in scope and complexity to "installing a passive containment spray system" at plants that presently do not have these features (Callaway SAMA #91).

Install an independent power supply to the hydrogen control system using either new batteries, a non- Not cost beneficial. The original and updated PRA case H2BURN conservatively safety grade Reduced assume that hydrogen burns and detonations do not occur.

108 portable hydrogeno2BURN 18.3K 43K >100K Cost to install an independent power supply to the H2 control system is based on generator, detonation (39K) (90K) Seabrook previous reported estimate.

existing station potential It is noted that SAMA #108 would benefit from SAMA #157, portable AC generator, batteries, or which was shown to be potentially cost beneficial.

existing AC/DC independent power supplies, such as the security system diesel Reduced Not cost beneficial. The original and updated PRA case H2BURN conservatively Install a passive hydrogen 18.3K 43K assume that hydrogen burns and detonations do not occur.

system detonationen0c1nt3oK)H(90K) detonation >100K (39K) (90K) Cost to install a passive hydrogen control system is based on Seabrook previous potential I IIIreported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1- SEABROOK - MAB &:PHASE 2 SAMA REVIEW SB.K  % Risk Total Benefit () Ex pecte.

Baseline (with 2.1 dSAMA SAA Potential Reduction Evaluatio

-. ^ . nt -poe Description PRA Case multiplier) Cost Evaluation Number Imrvmn

- CDF Pop. Internal & With

___________Dose- External Uncert. -

Erect a barrier that would provide Not cost beneficial. The original cost benefit was assessed based on MAB. The enhanced updated cost benefit assessment is based on PRA case HPMVE which assumes that protection of the Reduced high pressure melt ejection occurrences are completely eliminated. It is noted that high containment probability of <1K 1K pressure melt ejection phenomenon dose not represent a significant challenge to 110 walls (shell) from containment HPMVE 0 0 (<1 K) (2K) >10OM containment because of the current robust pressure design of the Seabrook ejected core failure containment.

debris following Cost to engineer and implement barrier modifications judged comparable in scope and a core melt complexity to plnsthat pentydo not have these features (Claa AMAA #110) scenario at high pat rsnl Claa )

pressure Not cost beneficial. The original and updated PRA case CONT02 conservatively assume guaranteed be success of all containment isolation valves. At Seabrook, containment isolation valves are already equipped with limit switches. The limit switch function is primarily for valve position indication/verification and judged not to contribute Add redundant Reduced significantly to the overall reliability of the containment isolation valves themselves.

and diverse limit frequency of Adding an additional limit switch would not provide significant improvement inthe 112 switches to each containment CONT02 0 6 115K 270K >1M reliability of the isolation function. For SAMA purposes, the limit switches are containment isolation failure (242K) (566K) conservatively assumed to contribute 50% to the containment isolation function. Thus, isolation valve and ISLOCAs the PRA case upper bound benefit is less than $566K

• 0.5 = $283K and is judged not cost beneficial.

Cost to engineer and implement diverse Cl valve limit switches judged comparable in scope and complexity to plants that presently do not have these features (Callaway SAMA #112).

Not cost beneficial. The original and updated PRA case LOCA06 conservatively assume complete elimination of all ISLOCA risk contribution. Performing increased testing of PIVs would not significantly reduce the ISLOCA event frequency. Nor is it practical to perform more frequent tests. This is because PIV testing cannot be safely performed during power operation and would require a plant shutdown. Plant transition to shutdown introduces risk and additional costs due to lost generation. For SAMA Increase leak Reduced 48K 114K purposes, increased PIV testing is conservatively assumed to reduce the ISLOCA 113 testing of valves ISLOCA LOCA06 <1 (11) (4K >1M frequency by 50%. Thus, the PRA case upper bound benefit is less than $240K *0.5=

in ISLOCA paths frequency 0 1Ks(4K 120K.

Cost to engineer and implement leak test system modifications judged comparable to other plants that presently do not have these features (Callaway 113). As stated, testing cannot be performed during power operation. The cost of lost generation as a result of even one plant shutdown and cooldown for several days needed to perform thE

____________________________________________________ ____________testing is expected to significantly exceed the benefit.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I -. SEABROOK -MAB & PHASE 2 SAMAREVIEW

"  % Risk Total Benefit(S) Expecte SAMvIA Ptnil SBKBaseline Description PRA Case Redutn (with 2.1 multiplier) d Cost SAMVA Evaluation Number Improvement CDh Pop. Internal ,With Dose External Uncert. .. .. *"

Not cost beneficial. The original and updated PRA case CONT02 conservatively assume guaranteed success of all containment isolation valves. At Seabrook, isolation of containment penetrations is typically performed using motor operated valves (MOV),

air operated valves (AOV) and check valves (CV), and combinations of these valves, depending on the operational function and isolation requirements of the specific penetration. Check valves are considered to be self-actuated valves. MOVs and AOVs Install self- automatically close upon receipt of Engineered Safety Actuation Signals. Containment actuatingReduced 115K 270K penetrations are either closed (isolated) or if open, automatically close upon receipt of 114 containment frequencyiof CONT02 0 6 (242K) (566K) >2M reliable Engineered Safety Actuation Signals. Self-actuated valves are judged to not isolation valves failure significantly improve the reliability of the containment isolation function. For SAMA purposes, the benefit of a self-actuating valve(s) is assumed to contribute 50% to the containment isolation function. Thus, the PRA case upper bound benefit is less than

$566K

• 0.5 = $283K.

Cost to install self-actuating valves based assuming two trains of Cl valves requiring replacement of exiting containment valves with self actuating valves (assume AOVs).

Piping and support changes, controls and wiring also needed to support modifications.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB& PHASE 2 SAMA.REVIEW ..

Total Benei Expecte SB Risk eft()

.Baseline Potential Reductin (with 2.1 d SAMA SAMA Potential Description PRA Case - Reduction-...m..ltplir) Cost Evaluation Number mpoentCF Pop. Internal & With Dose External Uncert. ________________________________

Locate residual Reduced Not cost beneficial. The original and updated PRA case LOCA06 conservatively 115 heat removal frequency of LOCA06 <1 48K 114K >1M assume that ISLOCA events do not occur.

(RHR) inside ISLOCA outside (101 K) (240K) Cost to relocate the RHR system function to inside containment is based on Seabrook containment containment previous reported estimate.

Institute a maintenance practice to Not cost beneficial. The original and updated PRA case NOSGTR conservatively perform a 100% Reduced assume that SGTR events do not occur.

119 inspection of steam generator NOSGTR 5 2 (141K) (329K) >500K Cost to perform 100% inspection each refueling outage is based on previous Seabrook team generator s te rator reported estimate. Costs for this item were estimated to be >$3M in Kewaunee, Beaver tubes during tube ruptures Valley and Calvert Cliffs License Renewal submittals.

each refueling outage Increase the pressure Eliminates capacity of the release pathway Not cost beneficial. The original and updated PRA case NOSGTR conservatively secondary side to the 67K 157K assume that SGTR events do not occur.

121 so that a steam environment NOSGTR 5 2 >500K generator tube following a (141 K) (329K) Cost to engineer and analyze design to increase the SG secondary side pressure is rupture would steam generator based on Seabrook previously reported estimate.

not cause the tube rupture relief valves to lift Route the discharge from the main steam Not cost beneficial. The original and updated PRA case NOSGTR conservatively safety valves Reduced assume that SGTR events do not occur. It is noted that Severe Accident Management through a consequences of Guideline SAG-5, Reduce Fission Product Release, includes guidance and procedure 125 structure where a a steam NOSGTR 5 2 67K 157K >500K steps for use of external spraying sources for fission product plume reduction including water spray generator tube (141 K) (329K) possible reduction of SG releases.

would condense rute wouldsteamnde rupture Cost to install main steam safety valve spray system to reduce fission product release the steam and remove most of during SGTR is based on Seabrook previously reported estimate.

the fission products 53 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB & PHASE 2 SAMA REVIEW SBK  % Risk Total Benefit ($) Expecte SAA Potential PR ae Reduction Baeie(ih21 d SAMA Eauto

. AMA S Im .-. r.veme

.. Description

• Rl Case multiplier) Cost Evauaton NumberDF . Pop. Internal With ,s)

.___________"_ 1Dose External Uncert.

Install a highly reliable (closed loop) steam Not cost beneficial. The original and updated PRA case NOSGTR conservatively generator shell- Reduced assume that SGTR events do not occur.

side heat consequences of 67K 157K 126 removal system a steam NOSGTR 5 2 -15M Cost to install a passive, closed loop SG heat removal system is greater than $15M.

that relies on generator tube (141 K) (329K) This is based on the water cooled isolation condenser being extremely large and natural rupture expensive to install for a fully constructed plant. Conceptually this installation would be circulation and similar to SAMA 77.

stored water sources Reduced Not cost beneficial. The original and updated PRA case NOSGTR conservatively 129 Vent safetymain steam valves in consequences a steam of NOSGTR 5 assume that SGTR events do not occur.

2 67K 157K 12 sfeyale a tue ( ) (>500K Cost to engineer and analyze design to locate main steam safety valves in containment containment generator tubeor route existing Safety valve discharge to containment is based on Seabrook rupture previously reported estimate.

Add an Improved Not cost beneficial. The original and updated PRA case NOATWS conservatively 130 independent availability of NOATWS 2 60K 139K >500K assume that ATWS events do not occur.

boron injection boron injection (126K) (292K) Cost to install independent boron injection system is based on Seabrook previously system during ATWS reported estimate.

Add a system of relief valves to Improved Not cost beneficial. The original and updated PRA case NOATWNS conservatively prevent equipment 60K 139K assume that ATWS events do not occur.

damage from availability after (126K) (292K) Cost to install additional relief capacity is based on Seabrook previously reported dmgfrm an A1VVS estimate.

pressure spikes during an ATWS Install an ATWS Increased ability Not cost beneficial. The original and updated PRA case NOATWS conservatively sized filtered to remove 60K 139K assume that ATWS events do not occur.

133 containment vent ratrhtfom NOATWS 4 2>500K torme dea reactor heat from (126K) (292K) Cost to install filtered vent with capacity for ATWS heat removal is based on Seabrook to remove decay ATWS events heat previously reported estimate.

Install digital Reduced Not cost beneficial. The original and updated PRA case LOCA05 conservatively break slarge probability of a 77K 181K assume that LOCA events, as a result of pipe failures, do not occur.

LOCA protection 17LCprtcin LOCA (a leak large break LOCA05 9 2 (6K (162K) (30)Cost (380K) >500K to install a digital break detectionsystem is based on Seabrook previously system before break) reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB.& PHASE 2 SAMA REVIEW ""

SBK  % Risk Total Benefit($) Expecte SAM P Reduction Baseline (with 2.1 d SAMA Evaluati.n NuSAMA IProvmentil Description PRA Case 1. ... o multiplier) Cost vauaton

.- CF Pop. Internal & With Dose External Uncert ________.__________._-_______.___..____________-___.________-__.___

Prevents secondary side depressurization should a steam line break occur upstream of the Insallseondry main steam side gu ard isolation valves. Not cost beneficial. The original and updated PRA case NOSLB conservatively assumE side guard pipes Also guards NOSLB <1 0 5K 11K that steam line break events do not occur.

steam isolation against or (01K) (24K) Cost to install secondary side pipe guards is based on Seabrook previously reported valves prevents estimate.

consequential multiple steam generator tube ruptures following a main steam line break event Modify SEPS Improve Not cost beneficial. The original PRA case OSEPALL and the updated PRA case design to reliability of OSEPS conservatively assume guaranteed success of all manual actions to align and accommodate onsite power; load the SEPS diesel generators. The current design requires the operator to manually automatic bus reduce SBO align SEPS to the desired bus and to manually load SEPS to ensure power is available 154 loading and CDF OSEPS 8 2 64K 151K >750K ainSP otedsrdbsadt aulyla ESt nuepwri vial automatic bus cDFtriEuSi8n2 (135K (318K) to needed components. The proposed SAMA is to install a control system to perform contribution; s these actions automatically.

alignment remove (Plant dependence on Cost to install automatic control system is based on Seabrook previously reported Personnel) operator action estimate.

Install alternate offsite power Improve offsite source that power reliability bypasses the and switchyard. For independence of Not cost beneficial. The original and updated PRA case NOLOSP conservatively 156 example, use switchyard and NOLOSP 18 17 531K 1.24M >7M assume elimination of all LOSP events.

campus power SF6 bus duct; (1.2M) (2.7M) Cost to install alternate offsite power source that bypasses the current switchyard powei source to allow restoration source is based on Seabrook previously reported estimate.

energize Bus E5 of offsite power or E6 within a few (IPE) hours I I I I IIII 55 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I1- SEABROOK - MAB & PHASE 2 SAMA REVIEW K  : Potent ia -0 R-- Cas Reduction Total Benefit($) Expecte SBKtent.... Redutis Baseline (with 2.1 :d SAMA SAMA Improvement Description PRACase multiplier) Cost Evaluation CDFbe Pop.~ Internal& With Numer..Dose External Uncert.

Provide independent AC power source for Reduce CDF of Potential cost beneficial SAMA. SAMA #157 was shown to be potentially cost battery chargers. long term SBO beneficial in the previous study. The previous and updated PRA case INDEPAC For example, sequences; 34K 80K conservatively assume that station batteries have AC power available for battery 157 provide portable extend battery INDEPAC <2 1 (72K) 8K 30K charging guaranteed success of AC power recovery to represent the benefit of generator to life to allow extended battery life.

charge station additional time Cost to implement portable battery chargers is expected to be less than the potential battery for recovery benefit.

(IPE)

Reduce CDF of long term SBO Not cost beneficial. The previous and updated PRA case INDEPAC conservatively Install additional sequences; assume that station batteries have AC power available for battery charging by assuminc 159 batteries extend battery INDEPAC <2 1 34K 80K >1M guaranteed success of AC power recovery to represent the benefit of extended battery (IPE) life to allow (72K) (168K) life.

additional time Cost to install additional batteries is based on Seabrook previously reported estimate.

for recovery Alternate cooling Not cost beneficial. The original PRA case NOSBO conservatively assumed eliminatior Modify EDG to both EDGs of all station blackout events by assuming guaranteed success of both DGs for all jacket heat would reduce events and independent of all support systems (control power, cooling, etc.). The exchanger CDF long term updated PRA case DGSW assumes success of SW components (valves) that are service water sequences associated with DG cooling and alignment of the SW system (ocean and cooling supply and return involving LOOP tower). Guaranteed success of these components and the resulting increase in SW to allow timely and loss of SW 25K 53K reliability is representative of the DG cooling water reliability gained from installing a 161 alignment of /cooling tower. A DGSW <1 1 (59K) (124K) 2M backup source of cooling water. Insights from this analysis are that the existing alternate cooling loss of service arrangement of SW cooling to the DGs is of a reliable design; and making the DGs less water source water / cooling dependent on SW does not provide a significant risk reduction because other train-(supply & drain) tower with a specific components, such as ECCS pumps, also depend on SW cooling.

from firewater, LOOP could RMW, DW, etc. result in EDG Cost of physical plant modifications and analysis judged comparable to other plants thai (Expert Panel) failure and non- presently do not have these features (Grand Gulf 10). Backup diesel cooling water recovery system is also addressed in SAMA #20.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1- SEABROOK- MAB & PHASE 2 SAMA REVIEW SBK Potential  % Risk Total Be~nef it.($ Expecte Reduction Baseline (with 2.1 d SANMtA SAA Improvement .DecitoPRCaemultiplier) Cost Evaluation Nube CF Pop. Internal & With C -.F. Dose :External Uncert. __________________.._._._.--_______..._._-__________. __._

Extend long term Not cost beneficial. The original and updated PRA case CST01 conservatively assume operation of a continuous, successful CST suction source for EFW.

EFW without operator action for CST makeup Cost of expanding capacity of the CST is based on project scope of Installing a new Increase the for sequences (larger) safety grade condensate storage tank, which is judged necessary to achieve ful capacity margin that do not go to 35K 81K benefit. Cost of physical plant modifications and analysis are comparable to other 162 of the CST cold shutdown. CST01 <2 1 (73K) (171K) >2.5M plants that presently do not have this feature (Callaway SAMA #71).

(Plant Enhance CST Personnel) margin for design-basis seismic event with cooldown via SG and transition to RHR Reduce CDF of SBO sequences by improving overall reliability of EFW system independent of Not cost beneficial. The original PRA case TDAFW conservatively assume guaranteed AC power. An success of the turbine-driven EFW pump. For simplification, the updated PRA case Install third EFW additional pump assumes guaranteed success of the motor-driven pump, i.e., the EFW pump function is pump (steam- might also have 356K 835K success and independent of AC power. Thus, the benefit of installing an additional 163 driven) a Level 2 benefit TDAFW 5 12 (748K) (1.8M) >2M turbine-driven pump is conservatively high.

by maintaining (Expert Panel) coverage of SG Cost of installing an additional steam-driven EFW pump is based on Seabrook tubes thus previously reported estimate.

reducing the release potential for induced SGTR given high pressure core melt sequence 57 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I - SEABROOK - MAB & PHASE 2 SAMA REVIEW Total Benefit ($)

SB %Risk Ep~ecte NSMbASAA Potential Improvement -:.> Description Reduction Baeie(ih21 mliPRArCase d cSAMA Eauto Evaluation CDF Pop. Internal & With Dose External Uncert.

Modify 10" Condensate Possible Filter Flange to enhancement of Potential cost beneficial SAMA. The original and updated PRA case CST01 have a 2hos-inch long term core 35K 81K conservatively assume a continuous, successful CST suction source for EFW.

164 female fire hose damage CST01 <2 1 71) >40K adapter with sequences that (73K) (171 K) Cost of modifying the condensate flange is expected to be less than the potential isolation valve credit CST benefit.

(Plant makeup Personnel)

RWST fill from firewater during containment Could enhance injection - Modify long term Potential cost beneficial SAMA. SAMA #165 was shown to be potentially cost 6" RWST Flush containment beneficial in the previous study. The previous and updated PRA case NORMW 165 Flange to have a injection NORMW 5 2 57K 134K 50K conservatively assume guaranteed success of RWST makeup.

2%/-inch female sequences that (121 K) (283K) Cost of modifying the RWST flange is expected to be less than the potential benefit.

fire hose adapter would benefit with isolation from RWST valve makeup (Plant Personnel) 58 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I.- SEABROOK - MAB &'PHASE 2 SAMA REVIEW

% Risk Total Benefit () Expecte SK Potential Reduction Baeie(ih21 d SAMA SAMA Improv

°e:ment Description PRA Case multiplier) Cost Evaluation Numer- CF Pop. Internal & With Dose External. Uncert.

Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha CS division B of high pressure injection (CSB) is independent and does not rely on support systems (independent of AC / DC power, cooling, etc.). This case is used to represent a "parallel" pump with same suction as CS-B, credited for seal injection. The Install new PRA case is judged conservative in that it benefits not only seal injection but also independent seal Reduce CDF high pressure injection.

injection pump contribution from 167 (low volume RCP seal LOCA CSBX 22 34 1.1M 2.5M 6.4M Cost of this modification is estimated at greater than $6.4M. This modification was pump) with events driven by (2.3M) (5.3M) assumed to be the equivalent of adding one new high pressure injection pump powered automatic start seal cooling by a diesel rather than an electric motor with a suitable injection path and suction hardware failures source. In the Duane Arnold License Renewal application, the cost of this was one half (IPE) the cost of replacing pumps discussed in SAMA 25 above, the cost would be $10 million. In addition, Grand Gulf SAMA #61 estimated the cost of a similar plant change at >$6.4M.

It is noted that some of the potential benefits of this SAMA would be realized with SAMA

1. 172, RCP shutdown seal.

Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha' Install CS division B of high pressure injection (CSB) is independent and does not rely on independent seal Reduce CDF support systems (independent of AC / DC power, cooling, etc.). This case is used to 168 (low volume RCP seal LOCA 11 M 2.5M represent a "parallel" pump with same suction as CS-B, credited for seal injection. The p(llump) wh 168 e tsdreal b CSBX 22 34 (2.3M) 25.3M) 6.4M new PRA case is judged conservative in that it benefits not only seal injection but also pump) with events driven by CSX2 4 (2.3M) (5.3M) high pressure injection.

manual start seal cooling hardware failures Refer above to SAMA#167 for approximate cost estimate.

(IPE)

It is noted that some of the potential benefits of this SAMA would be realized with SAMP

1. 172, RCP shutdown seal.

Reduce CDF Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that Install contribution from RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha' independent RCP seal LOCA CS division B of high pressure injection (CSB) is independent and does not rely on charging pump events driven by support systems (independent of AC / DC power, cooling, etc.). This case is used to (high volume seal cooling 1.1M 2.5M represent a "parallel" pump with same suction as CS-B, credited for seal injection. The 169 pump) with hardware CSBX 22 34 (2.3M) (5.3M) 6.4M new PRA case is judged conservative in that it benefits not only seal injection but also failures; improve high pressure injection.

manual start decay heat Refer above to SAMA#167 for cost basis.

(IPE) removal using It is noted that some of the potential benefits of this SAMA would be realized with SAMW feed & bleed #172, RCP shutdown seal.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOK - MAB & PHASE 2 SAMAREVIEW Total Benefit ($) Expecte

% Risk.!

SBK Baseline (with 2.1 d SAMA Potential Reduction SAMA Description .PRA Case multiplier) Cost Evaluation Improvement Number Pop., IInternal 8 With CDF Dose. External Uncert. Ms I. .4-----------------------------------------.4 Replace the Not cost beneficial. The original PRA case RCPLOCA conservatively assumed that Positive RCP seal LOCA events are eliminated. A more realistic PRA Case CSBX assumes tha Displacement CS division B of high pressure injection (CSB) is independent and does not rely on Pump (PDP) with Reduce CDF support systems (independent of AC / DC power, cooling, etc.). This case is used to a 3rd centrifugal contribution from 1.1M represent a "parallel" pump with same suction as CS-B, credited for seal injection. The charging pump. RCP seal LOCA 2.5M 170 CSBX 22 34 6.4M new PRA case is judged conservative in that it benefits not only seal injection but also Consider low events driven by (2.3M) (5.3M) high pressure injection.

volume and seal cooling cooling water hardware failures Refer above to SAMA#167 for cost basis.

independence It is noted that some of the potential benefits of this SAMA would be realized with SAMP (Expert Panel) #172, RCP shutdown seal.

Potential cost beneficial SAMA. The original and updated PRA cases RCPLOCA and Evaluate Reduce CDF RCPL conservatively assume elimination of the loss of RCP seal cooling initiating event installation of contribution from (LRCPCS) and also assumes guaranteed success of seal cooling for transients, thus a "shutdown seal" transients with avoiding RCP seal LOCA events subsequent to a plant transient.

172 in the RCPs being seal cooling RCPL 34 49 1.5M 3.5M 2M Cost of installing the RCP shutdown seals is expected to be less than the potential developed by hardware failures (3.2M) (7.4M) benefit.

Westinghouse resulting in RCP seal LOCA It is noted that installation of the RCP low leakage shutdown seals will benefit SAMAs (Expert Panel) events #14, #25, #26, #55, #56, #59, #167, #168, #169, #170 (Table 1) and BE#1, and BE#2 (Table 2).

Improve reliability of reactor scram by Provide alternate providing Not cost beneficial. The original and updated PRA case NOATWS conservatively scram button to remote-manual assume elimination of all ATWS risk.

remove power capability to NOATWS 4 2 59.5K 139K >500K Cost of modifying the scram system to provide an alternate scram button is based on 174 from MG sets to remove rod drive (125K) (292K) >eabrook pously reporte estimate.

CR drives power should the Seabrook previously reported estimate.

(IPE) reactor trip breakers fail; reduce ATWS contribution 60 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOI- MAB & PHASE 2 SAMA- REVIEW, BSB  % R is k Be n e fit C Tot ali2", s) E x pe cte -" -.. . . .

SAMA Potential Decito ae Reduction Baseline (w~ith 2.1 d SAMA Eauto SAMAD Impo n - Descrption po .P PRA Case.

C multiplier) Cost Evaluation NumCrd Pop. Internal With  :

Dose External Uncert.

Not cost beneficial. The original PRA case FIRE1 conservatively assumed complete elimination of the control room fire initiating event that results in a PORV challenge. A Fire induced refined PRA Case FIRE1A assumes guaranteed success of the operator action to close LOCA response Possible the PORV block valve during the postulated control room fire event (thus the CR fire procedure from reduction in CDF <1K <1K event is assumed to occur at its current frequency). The proposed SAMA is to improve 179 Alternate if mitigating fire- FIRE1A 0 0 (<1 K) (<2K) >20K operator procedures for coping with a small LOCA due to fire and opening of a PORV.

Shutdown Panel induced LOCA The procedure change would not eliminate, but potentially reduce the significance of (IPEEE) this event. Therefore, the estimated benefit is conservative for this SAMA.

Cost of modifying the operator response procedures and controls is based on Seabrook previously reported estimate.

Not cost beneficial. The original and updated PRA case SEISMIC01 conservatively assume complete elimination of relay chatter. As stated in the ER SAMA report, there Improve relay Reduce CDF is significant uncertainty in relay fragility and this is not necessarily addressed by 181 chatter fragility contribution from SEISMIC01 12 3 87K 204K >600K component replacement and is beyond state-of-the-art.

(IPEEE) relay chatter 0Cost of modifying/replacing existing relays is based on Seabrook previously reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I- SEABROOK - MAB & PHASE 2 SAMA REVIEW

-% Risk Total Benefit () Expecte SBK Potential Reduction Baseline (With 2.1 d SAMA SAMA Improvement Description PRA Case ___multiplier) Cost Evaluation Nube OE Pop. Internall. With

-> ____ Dose External Uncert.

Improve seismic Improve capacity of EDGs component Not cost beneficial. The original and updated PRA case SEISMIC02 conservatively 182 and steam-driven EFW fragility and reduce seismic SEISMIC02 <1 0 2.4K (6K) 5.6K (12K) >500K assume no seismic failures of the EDGs and turbine-driven EFW pump occur.

182 event Cost of upgrading the EDGs or the TD-EFW pump is based on Seabrook previously contribution to reported estimate.

(IPEEE) CDF Purge path is large opening.

Control/reduce Reduce time that the exposure time of Not cost beneficial. The original PRA case PURGE and the updated PRA case COP containment open path, <1K <1K conservatively assume that the containment purge valves are continuously in the closed 184 purge valves are improve COP 0 0 (<1 K) (<2K) >20K position and are not opened periodically.

lity of Cl, reduce Cost of procedural changes is based on Seabrook previously reported estimate.

(IPE) Cl failure contribution to large release Improve Install containment containment reliability by Not cost beneficial. The original and updated PRA case CISPRE conservatively 186 leakage reducing the CISPRE 0 0 4.4K 10.4K >500K assume complete elimination of pre-existing containment leakage.

monitoring potential for pre- (12K) (27K) Cost of installing leakage monitoring system is based on Seabrook previously reported system existing estimate.

(IPE) containment leakage 62 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE I1- SEABROOK - MAB & PHASE 2 SAMA REVIEW ik

% Total Benefit () Expecte SBK Risk Baseline (with 2.1 dSAMA Potential Evaluationn SAMA Descripton PRA Case Reduction multiplier) Cottion Cost Number Improvement N.CDF" Pop. 'Internal & With

______Dose External Uncert.

Not cost beneficial. The original and updated PRA case LOCA06 conservatively assume complete elimination of all ISLOCA risk contribution. However, improved leak Install RHR detection will eliminate some but not all ISLOCA events. For SAMA purposes, installing Reduce ISLOCA a leak detection system is assumed to reduce the ISLOCA frequency by 80%. Thus, isolation valve challenge to the PRA case upper bound benefit is estimated at $238K

• 0.8 = $190K.

leakage RHR by LOCA06 <1 48K 113K >500K 187 monitoring identification of (101 K) (238K) Cost to install a leakage monitoring system at the RHR isolation valves is judged system upstream valve comparable to other plants that presently do not have these features (Callaway SAMA (IPE) failure #111). This modification will require pressure and/or temperature transmitters installed in containment between isolation valves, the use of additional containment electrical penetrations to allow remote readouts/alarms in the control room to alert the operator that lower pressure piping is being challenged by RCS leakage.

Modify or analyze SEPS Allow all capability; 1 of 2 equipment to be Not cost beneficial. The original PRA case assumed a change to the SEPS success SEPS for LOSP run following criteria in that one of two SEPS DGS was capable of handling AC loads without a SI 189 non-SI loads, 2 LOSP with EDG SEPS 63K 148K >2M (LOCA) signal present, with no change to the manual alignment scheme. For of 2 for LOSP SI failure but (133K) (311 K) simplification, the updated PRA case conservatively assumes guaranteed success of al loads successful start SEPS hardware and no change to the current scheme of manual alignment.

and load of Cost to modify SEPS is based on Seabrook engineering estimate.

(Plant SEPS Personnel)

Add Eliminate current Not cost beneficial. The original PRA case NOSBO and recent PRA case NOSBO1 synchronization requirement for both conservatively assume elimination of all station blackout events by assuming capability to dead bus 224K 525K guaranteed success of both EDGs for all events and independent of all support systems 190 SEPS Diesel transfer from NOSBO1 22 6 (470K) (1.1 M) >6.4M (control power, cooling, etc.)

(Plant SEPS to normal The cost to install synchronization capability to the SEPS diesel is based on Seabrook Personnel) power engineering estimate.

Remove the Potential for Not cost beneficial. The original and updated PRA Case PCTES assume elimination of 135F some the inadvertent failure of the redundant temperature element/logic as a failure mode of temperature trip improvement in <1K <1K the associated PCC division for both loss of PCCW (A/B) initiating events (during the 191p teliminaiity of (<1 K) (<2K) >100K year) and loss of PCCW (A/B) mitigative function (mission time).

pumps by eliminating (Plant consideration of Cost and scope of modifying the temperature trip is based on Seabrook previously Personnel) spurious trip reported estimate.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOK - MAB.& PHASE'2 SAMA REVIEW ux

% Risk Total Benefit $) Expecte

-SBK Potential Reduction* Baseline (With 2.1 d SAMA SAMA Description PRA Case multiplier)CotEauin Numer mpoveen - DF Pop. InternalA With

____________Dose External Uncert.

Potential cost beneficial SAMA. SAMA #192 was shown to be potentially cost beneficial in the previous study. The updated benefit of the SAMA was estimated from the ratios of the previous flood model MAB result to the updated model MAB. A new specific SAMA model case was not performed.

Cost to install proposed flow reducing orifice is expected to be less than the potential Install flow orifice Reduce CDF benefit.

in fire protection contribution of Based on the previously estimated benefit of $161 K (nominal) and $307K (UB), the 192 system CB flooding due NOCBFLD 24 11 470K l.M 370K proposed SAMA to install a flow reducing orifice in the Control Building fire protection (New - Plant to fire protection (987K) (2.3M) system pipe continues to be potentially cost beneficial.

Personnel) pipe break Previous Flood model MAB: $1,042,683 (nominal), $1,982,048 (upper bound)

Revised SEABRK model MAB: $3,050,815 (nominal), $7,154,678 (upper bound)

Ratio increase: 2.92 (nominal), 3.61 (upper bound)

Nominal = 2.92 * $161K = $470K ($978K)

Upper bound = 3.61 * $307K = $1.1M ($2.3M)

Eliminate CSV167 AC Reduce Potential cost beneficial SAMA. SAMA #193 was shown to be potentially cost power containment 86K 201K beneficial in the previous study. PRA case CSV167 assumes guaranteed success of 193 dependence isolation failure CSV167 0 5 80K) (423K) 300K the operator action to close containment isolation valve CS-V-167 locally.

contribution of Cost to implement a change to the design of CS-V-1 67 is expected to be less than the (New- Plant CSV167 potential benefit.

Personnel)

Purchase or Not cost beneficial. The original and updated PRA cases MSSVRS assume success of manufacture of a the MSSVs to reseat.

"gagging device" that could be Improve release Cost to implement a safety valve gagging device is based on Seabrook previously used to close a mitigation for a <1K <1K reported estimate.

194 stuck-open SGTR event MSSVRS 0 0 (<1 K) (<2K) >30K steam generator prior to core safety valve damage (New - NRC RAI) 64 of 96

SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 1 - SEABROOK - MAB & PHASE 2 SAMA REVIEW SBK Total Benefit () Expecte Potetia Risk - Baseline (with 2.1 dSM SAMA improent Description PRA Case Reduion multipier) Cost Evaluation Number - CDF Pop. Internal- With Dose External Uncert. ____________...._,_____________

Potential cost beneficial SAMA. NextEra has entered into the long range plan for a modification to improve the reliability of CC-TV-2171/2271 -1 & 2. Refer to BE #9 (Table 2)

New SAMA The SAMA concept is to install hardware changes to improve the reliability of the CCW systems and reduce the loss of CCW initiating event frequency. Based on inspection of the CCW PRA model, the component failures that contribute the most to Make PCC Train B the loss of CCW initiator are components associated with temperature 195 improvements to Temperature 144K 337K control/modulation. In the PRA, these components are modeled as temperature New PCCW Element CC-TE- CCTE1 3 (302K) (709K) 300K elements (TE) causing failure of the temperature control scheme. PRA case CCTE1 is SAMA temperature 2271 transmits used to represent the potential risk reduction benefit. This case conservatively control reliability false low assumes guaranteed success of the TE function for PCC Trains A and B that could fail PCCW during the year (as an initiator) and during the mission time (support system model). Hardware changes to improve temperature control reliability - update of existing equipment or provide additional redundancy in instrumentation / controls.

Cost to engineer and install improvements to CCW temperature control are expected to be less than the potential benefit.

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SBK-L-12053 NextEra Energy Seabrook, LLC Supplement to Severe Accident Mitigation Alternatives Analysis TABLE 2 - SEABROOK - BASIC EVENT & INITIATING EVENT SAMA REVIEW Basic (BE*) Evn or*

(BE). or...._

RC RC I

E.I(;

vent Event

• eatdSM

" SAMAWs

-and Proposed

. TReated : '.

PRA Case

% Risk

R::

Ieduction Rui Total

' Baseline . (with.($)%

• Benefit multiplier) 2.1' .. Expected

-SAMA Cost Evaluation Initiating Event (1E)

I Group Description SAMA(s)l

"___ I___ CD.

Pop.

Dose Internal &

External With Uncert. __,

($)

Basic Event (BE) Related SAMAs Not cost beneficial. The SAMA concept is to enhance the operator's ability to align alternate cooling to the standby charging pump oil cooler in time to allow the standby pump to restart and restore RCP seal cooling before heatup of RCP seals. Success of the action avoids an RCP seal LOCA event. The PRA case conservatively assumes guaranteed success of the operator action to align alternate cooling. The cost of hardware changes to automate the alignment of alternate cooling will exceed the conservative Operator Action - Related SAMA #172. benefit.

BE #1 CDF Manual Alignment Provide automatic 340K 797K > 2.4 M HH.OALT1.FL LL5 of Alternate alignment of alternate OALTO 4 11 (714K 797K C pl o SELL Cooling to cooling based on (714K) (17M) Cost of physical plant modifications and Charging Pumps applicable signals analysis judged comparable in scope and complexity to STP SAMA #17, automation needed to protect RCP seals of 2.4M.

This SAMA is related to SAMA #172 (RCP shutdown seal). The importance of this SAMA would be reduced or eliminated with the installation of the RCP shutdown seal, which has been shown to be potentially cost beneficial.

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