Text

To Severe Accident Mitigation Alternatives Analysis Response to RAI Request Dated July 16, 2012, NextEra Energy Seabrook License Renewal Application
	ML12262A513
Person / Time
Site:	Seabrook
Issue date:	09/13/2012
From:	Walsh K; NextEra Energy Seabrook
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	SBK-L-12185, TAC ME3959
	Download: ML12262A513 (41)
	v • d • e

NEXTera EN ERCY September 13, 2012 SBK-L-12185 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 3 to Severe Accident Mitigation Alternatives Analysis Response to RAI Request dated July 16, 2012 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-12053, "Supplement 2 to Severe Accident Mitigation Alternatives Analysis" March 19, 2012, (Accession Number ML12080A137)

4. NRC Letter, Request For Additional Information For The Review Of The Seabrook Station License Renewal Application Environmental Review -SAMA Review (TAC No. ME3959),

July 16, 2012, (Accession Number ML12180A355)

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

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. In Reference 3, NextEra completed the PRA update (SB20 11) and provided a supplemental SAMA analysis based on PRA update SB20 11.

In Reference 4 the staff requested additional information to support the review of this supplement. Enclosure 1 provides NextEra responses to the requested additional information.

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

United States Nuclear Regulatory Commission SBK-L-12185 / Page 2 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, NextEra *negy Seabrook, LLC.

Kevin T. Walsh Site Vice President Enclosure cc:

W.M. Dean, NRC Region I Administrator J. G. Lamb, NRC Project Manager, Project Directorate 1-2 J. Grieves, 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 01702-5399

United States Nuclear Regulatory Commission SBK-L-12185/ Page 3 NEXTera ENERG I I, Kevin T. Walsh, Site Vice President 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 Kevin T. Walsh Site Vice President Notary Public

Enclosure to SBK-L-12185 NextEra Energy Seabrook Responses to NRC Request for Additional Information Regarding Severe Accident Mitigation Alternatives Analysis, Supplement 3

United States Nuclear Regulatory Commission SBK-L-12185 /Enclosure 1 /Page 1 of 36 SAMA RAI la Please provide the following information regarding the Level 1 Probabilistic Safety Assessment (PSA) used for the Severe Accident Mitigation Alternatives (SAMA) analysis:

The Initiating Event Contribution to core damage frequency (CDF) Table in Section 3.1.1 of the SAMA Supplement, Reference (3), presents initiating event contributors down to 2.5%

of the total combined (i.e., internal and external) CDF. Please provide initiating event contributors down to 1.0% of the total CDF. If this addition includes contributors that did not previously appear, other than for the new flooding analysis, please discuss their new presence.

NextEra Energy Seabrook Response to SAMA RAI la The table below provides the initiating event contribution to CDF down to 1% of CDF. The initiating events below 2.5% include internal event initiators LPCCA, LOSPP, FCRAC, LACPB and LOC1LG, and new internal flood initiators that were not included in the SB2006 model. All of the initiating events except for the SB201 1 internal flood initiators were identified in the previous SB2006 SAMA. There is not a significant shift in the relative CDF contribution of the initiators contributing to the top 99% of CDF compared to the previous SB2006 PRA model results.

Initiating Events (IE) that Contribute 1% and greater to CDF (SB2011) ilE Previous.

IE IECDF IE Percent CDF Initiating Percent CDF EveIniti D Description.

Frequency Contribution

.. Contribution I Contribution (peryr)

(peryr)

(SB2011) j (SB2006)

Seismic 0.7g Transient 9.30E-06 9.33E-07 7.6%

6 3%/o E7T Event Seismic 1.Og Transient 1.77E-06 8.88E-07 7.2%

5 9/o ElOT Evn Event Loss of Off-Site Power 7.65E-03 6.82E-07 5.6%

10/0%"

LOSPW due to Weather Major Flood - Rupture 2.73E-04 5.89E-07 4.8%

(a)

F4TREL of HELB / impact Relay Rm Steam Generator Tube 4.09E-03 5.69E-07 4.6%

'.4.0%/o SGTR Rupture Reactor Trip -

7.38E-01 5.41E-07 4.4%

g6.4%

Condenser Available LOCIMD Medium LOCA Event 1.88E-04 5.3 1E-07 4.3%

23%

Loss of Off-Site Power 1.15E-02 4.53E-07 3.7%

6 2/"

LOSPG

-Grid-Related Events Rupture of SW 1.27E-05 4.06E-07 3.3%

(a)

FISWCY Common Return Pipe in Yard

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 2 of 37 IE IE CDF IE Percent CDF IF Previous Initiating Description Frequency Contribution Contribution.

Percent CDF (per yr)

(per yr)

(SB201) contribution (SB2006)..

Seismic I.4g Transient 6.OOE-07 3.64E-07 3.0%

Event Fire in Control Room -

4.5 IE-05 3.62E-07 3.0%

Liot ý 1.0%

FCRPL PORV LOCA FSGBE6 Fire SWGR Room B -

1.OOE-03 3.46E-07 2.8%

26/6%

Loss of Bus E6 Loss of Train A 4.40E-03 3.19E-07 2.6%

24%,

LACPA Essential AC Power (4kV Bus E5)

Fire in SWGR Room A 1.10E-03 3.05E-07 2.5%

25-o FSGAE5

- Loss of E5 Loss of Train B PCCW 9.90E-03 3.03E-07 2.5%

.1 8/%.o:-:-

LPCCB System Loss of Train A PCCW 9.98E-03 2.34E-07 1.9%

1 8%.

LPCCA System F1PSWA Major flood, rupture of 1.10E-05 2.22E-07 1.8%

-(a)

SW Train A in PAB Loss of off-site power 5.66E-03 2.07E-07 1.7%

5.6%

LOSPP due to switchyard Large flood, rupture of 2.63E-04 2.03E-07 1.7%

(a)'

F2PSWA SW Train A piping in PAB Major flood, rupture of 2.63E-04 2.OOE-07 1.6%

(a)

F2PSWB SW Train B piping in PAB Large flood, rupture of 1.10E-05 1.97E-07 1.6%

.:;,(a)

F1PSWB SW Train B piping in PAB Major flood, rupture of 8.37E-05 1.81E-07 1.5%

(a).

Fire Protection piping F4TFPB in TB impacting offsite power.

FCRAC Fire in Control Room -

9.13E-07 1.79E-07 1.5%

5.

AC Power Loss Loss of Train B 4.40E-03 1.63E-07 1.3%

4.1 '/0:

LACPB Essential AC Power (4kV Bus E6 Large flood, rupture of 5.55E-06 1.46E-07 1.2%

?

(a)

F2PSWC SW common return piping in PAB LOC1LG Large LOCA 3.14E-06 1.24E-07 1.0%

2% 3o Note (a) - Flood initiator not included in SB2006 model.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 3 of 37 SAMA RAI lb Please provide the following information regarding the Level 1 Probabilistic Safety Assessment (PSA) used for the Severe Accident Mitigation Alternatives (SAMA) analysis:

Section 3.1 states on pages 4-5 that an installation of a flow orifice in fire protection piping in control building is credited in the SB2011 probabilistic risk assessment (PRA) model update and is undergoing final acceptance testing. Please clarify when this design change will be implemented and whether it has passed final acceptance testing. In addition please verify that the as-built design change supports the PRA SAMA assumptions.

NextEra Energy Seabrook Response to SAMA RAI lb The fire protection flow orifice modification is identified as cost-beneficial SAMA # 192 in the SAMA Supplement (Reference 3). Implementation of the engineering change for the flow orifice design is complete and acceptance testing satisfactory. The orifice as-built design is consistent with the PRA SAMA assumptions.

SAMA RAI 1c Please provide the following information regarding the Level 1 Probabilistic Safety Assessment (PSA) used for the Severe Accident Mitigation Alternatives (SAMA) analysis:

The CDF for Station Blackout (SBO) and Anticipated Transient Without Scram (ATWS) is not presented, and it is not clear whether these values have changed from the original 2009 submittal. Please provide CDF values for SBO and ATWS.

NextEra Energy Seabrook Response to SAMA RAI lc The approximate CDF contributions from SBO and ATWS events are as follows:

Event SB2006 SB2011 SBO 5.24E-06/yr 3.31E-06/yr ATWS 4.55E-07/yr 4.70E-07/yr There is only a small change in the SBO and ATWS CDF contributions between the SAMA Supplement (SB201 1) and the previous SAMA (SB2006).

SAMA RAI ld Please provide the following information regarding the Level 1 Probabilistic Safety Assessment (PSA) used for the Severe Accident Mitigation Alternatives (SAMA) analysis:

Previously, the contribution from internal events and internal floods together was 1.1 E-5/yr.

This has dropped to 7.1 E-6/yr (see p. 16 of 96). The severe weather contribution, which is not insignificant at 10.0%, was not previously provided. Please explain all these differences, at least qualitatively.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 4 of 37 NextEra Energy Seabrook Response to SAMA RAI ld The previous SAMA evaluation was based on Seabrook PRA Model SB2006. This model quantified a total CDF of 1.45E-05/yr with internal events, internal flood events and weather events contributing to the CDF as follows:

Event CDF SB2006 CDF SB2011 Internal Events 7.91 E-06/yr 4.55E-06/yr Internal Flood Events 7.79E-07/yr 2.61 E-06/yr Severe Weather Events 1.45E-06/yr 6.82E-07/yr The internal events CDF in SB2011 decreased slightly as a result of model enhancements and incorporation of more recent data (plant-specific and generic data). The internal flooding CDF in SB20 11 increased as a result of the comprehensive assessment of internal flood events and upgrade to the PRA model. The internal flood study produced 27 flood initiators compared to only 3 flood initiators in the earlier study. The severe weather CDF has decreased primarily due to incorporation of more recent data.

SAMA RAI le Please provide the following information regarding the Level 1 Probabilistic Safety Assessment (PSA) used for the Severe Accident Mitigation Alternatives (SAMA) analysis:

Among the basic event contributors to CDF and large early release frequency (LERF) (see pp. 17 and 19 of 96) are several that differ from those in the Jan. 13, 2011, RAI response.

Please explain the increase in RRW values for HH.XOEFW 1.FA, HH.XIONES3.FA and HH.OTS13.FA and decrease in RRW value for FWP37A.FR for the LERF importance listing. Also, explain the basic events removed from and added to the LERF and CDF listings.

NextEra Energy Seabrook Response to SAMA RAI le Changes in RRW (LERF) values are due to a number of small changes made in the PRA model between SB2006 and SB201 1. HEP values for basic events HH.XOEFWI.FA and HH.OTSI3.FA increased from SB2006 to SB2011 due to a change in the process of calculating HEPs (from taking the maximum of time-based HEP and cause-based HEP to use of the sum of time-based and cause-based HEPs). An increase to the HEP value results in a larger RRW value.

The HEP value for basic event HH.XIONES3.FA remain the same but its RRW increased as a result of Level 2 modeling of release category LE4 and credit for gravity drain of the RWST in containment. The failure rate for the Turbine-driven EFW pump FWP37A decreased from SB2006 to SB2011 due to improved plant-specific performance. A decrease in the pump's failure rate results in a decrease in RRW value.

The basic events added to and removed from the CDF and LERF listings are consistent with the changes made to the PRA model between SB2006 and SB20 11. The modeling changes are summarized in response to RAI 1 b3 of Reference (2) and Section 3.1 of Reference (3).

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 5 of 37 In the list of basic events contributing the CDF (page 17 of 96 to Reference 3), five basic events (ZZ.SY1.FX, [DGDG 1A.FR3], [DGDG 1B.FR3], SEPSDG2B.FR3 and SEPSDG2A.FR3) were also included in the previous list. Three HEP basic events (HH.OHSB1.FA, HH.OSGL3.FL and HH.OHSB6.FL) are new to the list because these HEP events were developed in SB2009 and were not part of the SB2006 SAMA model. Also, three common-cause basic events ([CCP IIA CCP1 lB CCP I1C CCP1 ID], [EDESWG5.FX EDESWG6.FX] and [EDESWG1 1A.FX EDESWGI IB.FX]) were not in the previous list. The list of the top basic events in the SAMA Supplement included both independent and common-cause basic events to ensure that both are evaluated. In the previous SAMA evaluation, only independent failure modes were considered.

The remaining new basic events on the list (HH.OALTI.FL, HH.OTSf3.FA, HH.OSEP2Q.FA and HH.OLPR2.FA) are the result of the model changes made between SB2006 and SB201 1.

In the list of basic events contributing to LERF, (page 19 of 96 to Reference 3), five basic events (HH.XOEFW1.FA, ZZ.SY2.FX, HH.OTSI3.FA, HH.ORWMZ1.FA and FWP37A.FR) were also included in the previous top list for LERF (RAI 5b of Reference 2 and Table F.3.2.1-2 of Reference 1). There were no common-cause events in the top LERF list. The remaining basic events on page 19 of 96 are new as a result of the model changes made in SB2011.

In both the CDF and LERF top basic event lists, basic events that are removed compared to the previous lists are due to small changes in RRW that place them below the top 15.

SAMA RAI 2a Please provide the following information relative to the Level 2 analysis:

The discussion for source term group Small/Early Containment Penetration Failure to Isolate and Large/Late Containment Basemat Failure (SELL) identifies that SELL uses the source term from release category LL5a and frequency from release category SELL5a. The Table on page 6 identifies that LL5a is a contributor to source term group LL5. The discussion for LL5 identifies that MAAP Case #106f was used to provide a representative source term while the discussion for SELL identifies that MAAP Case #1 06g was used for this source group. Please clarify this apparent discrepancy.

NextEra Energy Seabrook Response to SAMA RAI 2a LL5a provided the most significant source term compared to LL3b and LL4b. As a result, LL5a was used "in the development" of the new source term SELL, of which MAAP case #106 is used to characterize the specific SELL source term. The source term for release category LL5 is based on MAAP Case #106f while release category SELL is based on MAAP Case #106g. These two MAAP cases are identical station blackout sequences leading to long term containment failure due to basemat failure - except that, for SELL (Case #106g), an additional small containment penetration failure was added. Thus, SELL is based on a similar accident sequence as LL5, but uses a distinct source term from LL5.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 6 of 37 SAMA RAI 2b Please provide the following information relative to the Level 2 analysis:

The dose risk and Off-site Economic Cost Risk (OECR) results are different for the SB2006 and SB2011 PRA model results. The reason for these differences is not clear in every case.

Using Table F.3.2.1-1 and requests for additional information (RAIs) 2g and 4a associated with the SB2006 environmental report (ER), and release category results from the SB2011 submittal, please discuss the model basis that caused the following observations:

i.

LEI - The CDF for this release category decreased from 1. 1E-7/yr to 5.2E-8/yr, and the SB201 1 release fractions for the noble gases, iodine (I) and cesium (Cs),

are significantly delayed compared to their timing in the SB2006 model.

ii.

LE2 - The CDF for this release category increased from 4.OE-9/yr to 1.8E-8/yr.

The SB201 1 noble gas release fraction is similar to the SB2006 model, but the I and Cs release fractions are reduced by half.

iii.

SE3 - The dose risk and OECR for this release category decreased by a factor of about three. The new SELL source term group appears to be a sub-part of the original small early containment isolation failure source term group (i.e., SE3).

NextEra Energy Seabrook Response to SAMA RAI 2bi Release category LE 1 is defined as a large/early containment bypass due to steam generator tube rupture without scrubbing. The frequency for release category LEI decreased from SB2006 to SB20 11 due to the improvement in component reliability, specifically for the AFW pumps, as demonstrated by plant specific data. The source term timing for LEI changed from SB2006 to SB20 11 because of a more detailed accounting for the long term containment performance. For SB2006, the source term for LEI was represented by a SGTR sequence with no containment spray, with the release stopping at 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . For SB201 1, the source term for LEI was represented by a SGTR sequence with containment spray injection, but with the release continuing for 168 hours0.00194 days 0.0467 hours 2.777778e-4 weeks 6.3924e-5 months (7 days). In this sequence, the containment fails at about 39 hours4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months due to overpressure with an additional release independent of the release through the ruptured SG tube. This sequence with successful containment spray represents a more realistic source term for LEI while the longer release time better accounts for the complete release.

NextEra Energy Seabrook Response to SAMA RAI 2bii Release category LE2 is defined as a large/early containment bypass due to an interfacing system LOCA through the RHR system, without scrubbing. The source term for LE2 in SB2006 was based on a generic analysis that relates back to WASH-1400. For SB201 1, a Seabrook-specific analysis state-of-the-art source term calculation from MAAP4 was utilized.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 7 of 37 NextEra Energy Seabrook Response to SAMA RAI 2biii Release category SE3 (small, early containment failure) from SB2006 was divided into two release categories, SE3 and SELL, in the SB201 1 update. This revision was based on more detailed modeling of the long term containment performance for sequences with a small early containment leak. Thus, in SB201 1, release category SE3 is defined as "intact containment except for small penetration unisolated," that is, those core damage sequences where a small penetration is open but containment cooling is successful and the containment remains otherwise intact for the long term. In contrast, release category SELL is defined as "small penetration unisolated with long term containment failure via overpressurization or basemat melt-through,"

that is, those core damage sequences where a small penetration is open and containment cooling is not successful for the long term. As a result, the frequency and source term for SE3 decreased from SB2006 to SB2011 since the more severe "small-early" sequences are now represented by SELL.

SAMA RAI 2c Please provide the following information relative to the Level 2 analysis:

The dose risk and OECR results for release category LL5 changed significantly between SB2006 and SB201 I (greater than a factor of 100). The text on page 33 indicates that the increase in SAMA case "MAB" is due to higher release category source terms (apparently referring to LL5). The CDF for LL5 increased from 3.2E-7/yr to 3.1E-6/yr, the SB201 1 noble gas release fraction is similar to the SB2006 model, however the I and Cs release fractions are larger, and the release timing is significantly earlier. Please discuss the model basis that caused these changes.

NextEra Energy Seabrook Response to SAMA RAI 2c The source term for release category LL5 for SB2011 is based on a Seabrook-specific MAAP run for a station blackout scenario without recovery. This results in a core damage event with long term containment failure due to basemat melt-through. The release category LL5 for SB2006 was based on a similar-plant (Zion) analysis using results from the IDCOR work from the 1980s.

Thus, the SB20 11 update provides a Seabrook-specific analysis in place of a similar-plant analysis and uses the current state-of-the-art source term calculations.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 8 of 37 SAMA RAI 2d Please provide the following information relative to the Level 2 analysis:

Please provide a general explanation of the differences in the release start times and durations from MAAP presented in the Table on page 12 from the release start times and durations presented in the Tables on pages 20-26 for MACCS. For example, for LEI, on page 12 the first puff release starts at 3.2 hr (-11,520 s) and the second puff starts at 39.3 hr

(-141,800 s). However, on page 20 the first plume starts at 9328 s (-2.6 hr) and the fourth plume starts at 172,800 s (48 hr).

NextEra Energy Seabrook Response to SAMA RAI 2d The MAAP table on page 12 of the SAMA Supplement (Reference 3) provides a summary representation of the scenario/releases from the MAAP cases used to characterize each release category. The MAAP releases assume a seven-day release duration. The release tables beginning on page 20 of the SAMA Supplement provide the MACCS2 release parameters used to characterize the release timing and radionuclide fractions provided by the MAAP cases. As noted in the SAMA Supplement, MACCS2 allows a maximum of four plumes, each with a maximum duration of 1-day. Thus, the MAAP seven-day release is divided into four plumes, each plume having an approximate start time and duration, to approximate the entire release in MACCS2. The release start time used in the summary MAAP table is set at roughly 10% of noble gas release. This was used to indicate when the major release began. The MACCS2 cases treated the release in more detail, with four plumes. The initial plume models the start of the release earlier, when the release has just begun.

SAMA RAI 3a Please provide the following with regard to the SAMA identification and screening process:

Two Tables in Section 3.1.1, Top 15 Basic Events Contributing to CDF and Top 15 Basic Events Contributing to LERF, provide the Risk Reduction Worth (RRW) for CDF and LERF down to a value of 1.02. In Section 4.1 the Top 15 Basic Events Contributing to CDF, LERF, and release category (RC) contributing to 90% of the Public Risk provides the top 15 basic events for each of the following: CDF, LERF (which includes LEI, LE2, LE3, and LE4), and RCs LL-5, SE-3, and SELL. The RRW values for basic events importance to LL-5, SE-3, and SELL are not provided. In an RAI response dated January 13, 2011, the top 15 basic events were provided along with their corresponding RRW values for the risk dominant (i.e., contributing to 90 percent of the population dose) release categories (i.e.,

SE3, LL3, LEI, SE1, and LL4). From RAI response it could be determined that the maximum benefit that might be calculated from eliminating the 15th most important basic event resulted in benefits less than a simple hardware implementation cost of (i.e., $1OOK).

Given the changes in release frequencies, such as the 10 fold increase in LL5, it is not clear whether all important basic events are identified as part of the 45 basic events presented in the Section 4.1 table. Please provide the RRWs for basic events contributing to LL-5, SE-3, and SELL down to a minimum RRW value that would ensure that the maximum possible

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure I / Page 9 of 37 benefit would exceed the cost of a simple hardware or administrative change (-$100K). If this requires addressing further basic events, please include their evaluation in Table 2 of Section 4.3.

NextEra Energy Seabrook Response to SAMA RAI 3a Tables RAI-3-1-LL5, RAI-3-1-SELL and RAI-3-1-SE3 provide the basic events and associated RRW values that contribute to LL5, SELL and SE3. Basic events are evaluated down to an RRW value sufficient to ensure that SAMA candidates having a nominal benefit in the range of

$1 00K to $200K are identified. In the case of release categories SELL and SE3, the previously evaluated basic events in each release category sufficiently capture the SAMA basic events down to a nominal benefit in the range of $1 00K to $200K and no additional basic events are evaluated.

In the case of release category LL5, 28 new SAMA basic events were evaluated for nominal benefit in the range of $1 00K to $200K. The corresponding basic event RRW value for this cost range is in the range of 1.005, which is consistent with industry guidance to distinguish risk significant SSCs and represents a reasonable threshold for this evaluation. This provides reasonable assurance that all important cost-beneficial SAMAs related to basic events have been identified. No new potentially cost beneficial SAMA candidates were identified. Table RAI-3-2 provides the Phase II evaluation of the new LL5 basic events.

SAMA RAI 3b Please provide the following with regard to the SAMA identification and screening process:

Table 2 of Section 4.3 provides the benefit of SAMAs specifically devised for reducing the risk associated with each of the top 16 initiating events contributing to CDF and the top 15 initiating contributing to LERF. The RRW values for these initiating events are not provided, and because they are not provided it is not clear if all important initiators against CDF and LERF are addressed by SAMA evaluation. Please provide RRWs values for initiating events against CDF and LERF. Provide importance analysis listing down to a minimum RRW value that would ensure that the maximum possible benefit would exceed the cost of a simple hardware or administrative change (-$1 0OK). If this requires addressing more than the 16 initiating events already considered against CDF and the 15 initiating events already considered against LERF please include their evaluation in Table 2 of Section 4.3.

NextEra Energy Seabrook Response to SAMIA RAI 3b Initiating Events Contributing to CDF:

The top initiating events contributing to CDF and their percent contribution are presented in the response to RAI I a. The top 16 CDF initiators were evaluated in the SAMA Supplement (Reference 3). The remaining initiators are evaluated in Table RAI-3-3. No new cost beneficial SAMAs are identified. Evaluation of CDF initiators down to approximately 1% indicates that

United States Nuclear Regulatory Commission SBK-L-12185 /Enclosure 1 /Page 10 of 37 the benefit is in the nominal range of $1 00K to $200K (and less) for many of these CDF initiators. Thus, evaluation of initiating events that contribute down to -1% CDF provides a reasonable threshold to ensure that all important cost-beneficial SAMAs related to CDF initiating events have been identified.

Initiating Events Contributing to LERF:

The top 15 initiating events contributing to LERF and their percent contribution are presented in the table below. Evaluation of the LERF initiators that contribute down to approximately 1%

indicates that the benefit is in the nominal range of $1 00K to $200K (and less) for many of these LERF initiating events. Thus, evaluation of initiating events that contribute down to 1% LERF provides a reasonable threshold to ensure that all important cost-beneficial SAMAs related to LERF initiating events have been identified.

Top 15 Initiating Events (iE) that Contribute to LERF (SB2011) ti-lnitinvtiin".

EFrequency IE LERF Percent of.

I Description (p erequen Contribution LERF venteryr (per yr)

Contribution Steam Generator Tube 4.09E-03 4.45E-08 48.3%

Rupture LOC1VI Interfacing Systems LOCA, 3.67E-06 1.80E-08 19.5%

RHR Injection Valves Failure E25L Seismic 2.5g Large LOCA 9.86E-08 7.29E-09 7.9%

E18L Seismic 1.8g Large LOCA 9.55E-08 4.36E-09 4.7%

E18T Seismic 1.8g Transient Event 8.55E-08 3.83E-09 4.2%

E14A Seismic 1.4g ATWS 6.OOE-07 3.21E-09 3.5%

E18A Seismic 1.8g ATWS 9.55E-08 2.83E-09 3.1%

E25A Seismic 2.5g ATWS 9.86E-08 2.65E-09 2.9%

E25T Seismic 2.5g Transient Event 9.86E-08 1.80E-09 2.0%

E1OA Seismic 1.Og ATWS 1.77E-06 1.32E-09 1.4%

Main Steam Line Break 1.OOE-02 7.14E-10 0.8%

Outside Containment Main Steam Safety Valve 1.00E-03 2.79E-10 0.3%

Stuck Open E7A Seismic 0.7g ATWS 9.30E-06 1.83E-10 0.2%

LOC1VS Interfacing Systems LOCA, 3.14E-08 1.45E-10 0.2%

RHR Suction Valves Failure ATWS - Main Feedwater 9.91E-01 9.49E-11 0.1%

Available

United States Nuclear Regulatory Commission SBK-L-12185/Enclosure 1 /Page 11 of 37 SAMA RAI 3c Please provide the following with regard to the SAMA identification and screening process:

Step (b) in the general approach to the reassessment (Section 2.0) does not list at least three criteria by which SAMA candidates were previously eliminated: (1) being combined with another similar SAMA, (2) costing more than the MAB, and (3) being related to a non-risk significant system. Please provide additional information describing how these criteria were considered in the re-assessment. (Note that this RAI also applies to step 2 in Section 4.1

[see. p. 28 of 96].)

NextEra Energy Seabrook Response to SAMA RAI 3c The Phase 1 SAMA candidates, which were qualitatively screened from further detailed assessment in the original SAMA assessment, were not reviewed further in the SAMA Supplement (Reference 3). This is because the SAMA Supplement (performed to include minor PRA model changes and revised release category source terms) does not change the conclusions of the previous qualitative screening of Phase 1 SAMA candidates, except for those SAMA candidates screened on MAB. The SAMA candidates that were previously screened on MAB were re-assessed in the SAMA Supplement. All other previously screened Phase 1 SAMA candidates continue to meet the qualitative screening criteria of: (a) "not applicable", (b) "already implemented or intent is met", or (c) "combined with another SAMA candidate". Criterion (d)

"excessive implementation cost" and criterion (e) "very low benefit" were not used in the original Phase 1 screening so that their SAMA costs and benefits could be judged as part of the Phase 2 quantitative assessment. All Phase 2 SAMA candidates are re-assessed in the SAMA Supplement as are all SAMAs previously screened on MAB.

SAMA RAI 4a Please provide the following with regard to the Phase II cost-benefit evaluations:

In Section 4.2, on p. 34 of 96, it is stated that "[t]he sensitivity of the SAMA Supplement results to variations in other Level 3 parameters is expected to be consistent with previous sensitivity results." Please provide discussion comparing the updated results to the previous results confirming this expectation.

NextEra Energy Seabrook Response to SAMA RAI 4a Except for the difference in source term release, the SAMA Supplement (Reference 3) evaluation did not change the Level 3 parameters used in the previous SAMA evaluation. As a result, the sensitivity of the updated results to variations in the Level 3 parameters is expected to be similar to the previous sensitivity results. This assertion is further supported based on inspection of the results of the sensitivity evaluations performed for the SAMA Supplement as provided below:

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 12 of 37 Sensitivity Case-,

A'.-

Assessment Meteorology The baseline SAMA Supplement conservatively assumes continuous rainfall Specification in the imposed from 40 to 50 miles from release to force conservative population last Spatial Segment exposure. The updated sensitivity case removes this conservative assumption and allows the 40-50 mile segment to follow the site meteorology. This resulted in a reduction to the dose and cost risks of approximately 85% of the baseline. This dose and cost risk reduction is consistent with the reduction calculated in the previous SAMA sensitivity evaluation. This evaluation implies that this one assumption adds 15 percent conservatism to the baseline results.

Sea-breeze Effects No Evacuation -

Release Category LE4 The sea-breeze effect on dose and cost risks was re-evaluated in the SAMA Supplement. The results of this sensitivity evaluation indicated a small increase in the dose and cost risks when conservatively accounting for sea-breeze effects. This result is consistent with risk increase calculated in the previous SAMA sensitivity evaluation of sea-breeze effects.

Release category LE4 is used to represent extreme seismic events where evacuation of the population could be delayed. A sensitivity evaluation in the SAMA Supplement assumed no evacuation for this release category and this resulted in a small increase in the total LE4 dose consequence. This result is consistent with the previous SAMA sensitivity evaluation, Fraction of Population Evacuating, which performed a similar sensitivity of no evacuation for release category SE3. In the previous SAMA, release category SE3 was used to represent extreme seismic events, similar to LE4 in the updated model.

SAMA RAI 4b Please provide the following with regard to the Phase II cost-benefit evaluations:

In Section 4.2, on p. 35 of 96, it is stated that "[n]o new potentially cost-beneficial SAMAs were [sic] identified as a result of the 3% and 8.5% sensitivity calculations." Is this relative to the original analysis (submittal plus RAI responses) or to the re-analysis provided here for cost-beneficial SAMAs?

NextEra Energy Seabrook Response to SAMA RAI 4b No new potentially cost-beneficial SAMAs were identified as a result of the 3 percent and 8.5 percent sensitivity calculations relative to the updated SB201 1 re-analysis for cost-beneficial SAMAs.

SAMA RAI 4c Please provide the following with regard to the Phase II cost-benefit evaluations:

Section 4.2 provides the new Maximum Averted Benefit (MAB) (i.e., $3.05M) using the SB2011 PRA model. Also please provide the Averted Public Exposure (APE) costs, Averted Off-site Property Damage Costs (AOC), Averted Occupational Exposure (AOE) costs, and Averted Onsite Costs (AOC).

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 13 of 37 NextEra Energy Seabrook Response to SAMA RAI 4c The SB201I1 SAMA Supplement re-analysis estimated the following nominal averted costs:

Description Cost Averted Public Exposure (APE) Cost

$815,072 Averted Off-site Property Damage Cost (AOC)

$1,950,586 Averted Occupational Exposure (AOE) Cost

$4,642 Averted Onsite Cost (AOC)

$278,210 Total (MAB)

$3,048,510 SAMA RAI 4d Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 1 of Section 4.3, neither the risk reduction values nor PRA modeling assumptions for SAMA case MAB are provided. The evaluation for SAMA 77 incorrectly states that "Cost to engineer and implement installation of large passive air cooling system is far in excess of the attainable benefit". The original SAMA evaluation submittal estimated the cost of implementing this SAMA to be >$3M. Please provide the risk reduction values and PRA modeling assumptions for SAMA case MAB. Also, please provide justification of the cost of SAMA 77 and explain why it was necessary to increase this cost estimate.

NextEra Energy Seabrook Response to SAMA RAI 4d Table 1 of the SAMA Supplement (Reference 3) identified "MAB" in the PRA Case column for SAMAs 65 and 77. MAB is used to indicate that the "maximum attainable benefit" is assumed as the basis for cost-benefit worth. A specific PRA case is not used because MAB represents the total averted cost assuming complete elimination of the total plant risk, hence the risk reduction is 100%. The MAB total benefit is $15M when considering uncertainty (95 percentile) and seismic multiplier of 2.1.

As noted in the SAMA Supplement, Section 2.0 paragraph f), the implementation cost of each SAMA was reassessed as necessary to ensure that the cost continues to be representative of the SAMA scope. The scope of SAMA #77 is to install a passive, secondary-side heat rejection loop consisting of a condenser and heat sink. This is a significant and complex design change in that the new system would operate "passively" and independent of other systems, and that it would consist of a closed "loop" to limit inventory losses eliminating the need for makeup systems and with proper height and elevation to allow operation by natural circulation and conduction. This type of system is similar to a BWR isolation condenser. The cost to engineer and implement a similar system in an existing PWR plant is estimated to significantly exceed $15M.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1/Page 14 of 37 SAMA RAI 4 e Please provide the following with regard to the Phase II cost-benefit evaluations:

Table 1 of Section 4.3 presents revised SAMA case CONTX1 which is defined to eliminate alternating current (AC) and direct current (DC) power and Primary Component Cooling Water (PCCW) support system failures for one division of Containment Building Spray (CBS). The evaluation for this SAMA case explains that this case more realistically represents the potential risk reduction benefit than the case it replaced (i.e., CONTOI -

Installation of an independent division of containment spray). It is not clear that the PRA assumption for this case (CONTX 1), which consists of eliminating support system failures, bounds the SAMAs represented by this case (i.e., #91, #94, #99, #102, and #107). In light of the potentially high cost benefit (the current cost benefit with uncertainty and the seismic multiplier is >$5.7M), please provide justification for why this case is representative of each SAMA grouped under it and clarify whether a less restrictive or different case may be more appropriate. If a less restrictive or different case may be more appropriate please provide the corresponding evaluations.

NextEra Energy Seabrook Response to SAMA RAI 4e SAMAs #91, #94, #99, # 102 and # 107 have been reevaluated using a sensitivity PRA case different from case CONTX1 to ensure that the cost-benefit of these SAMAs is adequately characterized for the given SAMA scope. Table RAI-4-1 identifies the PRA cases used in the sensitivity assessments and provides the results of each evaluation. Based on the sensitivity cases, these candidate SAMAs are not cost beneficial. A summary of the sensitivity results is provided below.

SAMA # 91 - Passive Containment Spray System: SAMA sensitivity benefit could be higher than the previous CONTX 1 evaluation. The sensitivity benefit is less than the previously reported cost estimate.

SAMA # 94 - Filtered Containment Vent System: SAMA benefit could be higher than the previous CONTX1 evaluation. The sensitivity benefit is significantly less than the revised cost estimate. The cost estimate for implementation of a filtered vent is revised to ensure a realistic estimate and is based on more recent industry cost information.

SAMA # 99 - Strengthen Containment: SAMA benefit could be significantly lower than the previous CONTX1 evaluation and is significantly less than the previously reported cost estimate.

SAMA # 102 - Construct Containment Ventilation Building: SAMA benefit could be higher than the previous CONTX1 evaluation. Sensitivity benefit is significantly less than the previously reported cost estimate.

SAMA # 107 - Redundant Containment Spray System: SAMA benefit could be significantly lower than the previous CONTX I evaluation. Sensitivity benefit is significantly less than the previously reported cost estimate.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 /Page 15 of 37 SAMA RAI 4f Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 1 of Section 4.3, the expected cost of SAMA 162 (Increase the capacity margin of the condensate storage tank (CST)) is >$2.5M. In the original submittal the expected cost of this SAMA was presented as >$ 100K. The evaluation of this SAMA in the supplement states that the "Cost of expanding capacity of the CST is based on project scope of installing a new (larger) safety grade CST, which is judged necessary to achieve full benefit." In light of the fact that the new cost benefit with uncertainty and the seismic multiplier is 171K, please explain the basis for the earlier cost estimate and why it was necessary to increase this cost estimate by a factor of 25.

NextEra Energy Seabrook Response to SAMA RAI 4f As noted in the SAMA Supplement (Reference 3), the implementation cost of each SAMA was reassessed as necessary to ensure that the costs are representative of the SAMA scope. The implementation cost estimate for SAMA # 162 was reassessed and was increased to more accurately reflect the expected cost of the SAMA. The previous cost estimate of >$ 100K for SAMA #162, was based on a conservative minimum cost estimate for a noncomplex hardware change. This minimum cost estimate was significantly greater than the previously calculated SAMA benefit therefore, it was not necessary to perform a detailed cost estimate in the previous assessment. The scope of SAMA #162 is the same as the previous SAMA assessment.

SAMA RAI 4g Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 1 of Section 4.3, the expected cost of SAMA 189 (Modify or analyze supplemental emergency power supply (SEPS) capability; 1 of 2 SEPS for loss of off-site power (LOSP) non-safety injection (SI) loads, 2 of 2 LOSP SI loads) is >$2M. In the original submittal the expected cost of this SAMA was presented as >$300K. The SAMA appears that it could primarily be an analytical task. In light of this and the fact that the new cost benefit with uncertainty and the seismic multiplier is 311 K, please explain why it was necessary to increase this cost estimate by a factor of 7.

NextEra Energy Seabrook Response to SAMA RAI 4g As noted in the SAMA Supplement (Reference 3), the implementation cost of each SAMA was reassessed as necessary to ensure that the costs are representative of the SAMA scope. The implementation cost estimate for SAMA #189 was reassessed and was increased to more accurately reflect the expected cost of the SAMA. The updated cost estimate is based on a Seabrook engineering estimate and covers the expected costs of analysis, hardware modifications

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 16 of 37 and testing. The previous cost estimate of>$300K for SAMA #189, was based on a conservative minimum cost estimate. The previous minimum cost estimate was significantly greater than the previously calculated SAMA benefit therefore, it was not necessary to perform a detailed cost estimate in the previous assessment. The scope of SAMA #189 is the same as the previous SAMA assessment.

SAMA RAI 4h Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, the cost benefit for SAMA case OHSBO (for BE #5) is presented as >1M in the "Expected SAMA cost" column, yet the discussion in the "Evaluation" column states that the cost was estimated to be $1.5M. Please clarify this apparent discrepancy.

NextEra Energy Seabrook Response to SAMA RAI 4h This was an editorial error in Table 2 of the SAMA Supplement (Reference 3). The expected cost for SAMA BE #5 is $1.5M consistent with the cost basis evaluation for SAMA BE #5 provided in Table 2 of the SAMA Supplement. Table 2, as shown on page 69, of Reference 3 is revised as follows:

BE #5 HH.OHSB1.FA CDF LL5 Operator action to maintain stable plant conditions with SG cooling during transients Hardware change to improve ability to maintain stable primary and secondary conditions with plant in hot standby.

OHSB 0

5 143K (301 K) 335K (705K)

>1 R4

> 1.5M Not cost beneficial. The SAMA concept is to incorporate hardware change to improve operator's ability to control/maintain stable hot standby conditions following transient/accident events. Operator must monitor and control primary and secondary conditions including PZR level and pressure, RCS temperature and SG levels to maintain stable hot standby conditions for extended cooling using the SG. PRA case OHSB0 assumes guaranteed success of "all" actions OHSB1 (trans), OHSB2 (SBO), OHSB3 (SLOCA/SLB) and OHSB4 (SGTR) for maintaining stable hot standby conditions. Procedures directing these actions are sufficiently detailed and evaluated in the PRA human reliability analysis. Any changes to procedures are judged not to have a significant beneficial impact on release risk.

Cost to engineer and implement plant modifications and analysis judged comparable in scope and complexity to Davis Besse SAMA CC-19 to automate controls for injection switch over is similar in magnitude and complexity was estimated at $1.5 M.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 17 of 37 SAMA RAI 4i Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, the evaluation for BE #34 states that the PRA case "conservatively assumes that elimination of Bus E5 and E6 random failures that could cause an initiating event.... and/or fail the associated power division during mission time". Please clarify whether the PRA assumptions for this modeling case (i.e., SWGE56l) include elimination of initiators, basic events or both.

NextEra Energy Seabrook Response to SAMA RAI 4i PRA case SWGE561 considers elimination of both initiating events and basic events associated with 4kV Essential Buses E5 and E6.

SAMA RAI 4j Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, the event description for BE #38 refers to operator actions after loss of coolant accident (LOCA) and steam generator tube rupture (SGTR), but the evaluation refers to actions after a small LOCA (SLOCA) and interfacing system LOCA (ISLOCA). Please clarify this apparent discrepancy.

NextEra Energy Seabrook Response to SAMA RAI 4j BE #38 considers operator action to maintain stable primary and secondary plant conditions for extended steam generator cooling after small LOCA (SLOCA), interfacing system LOCA (ISLOCA) and steam generator tube rupture (SGTR) events.

SAMA RAI 4k Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, the entries for IE #8 and #9 appear to be duplicates. Please clarify.

NextEra Energy Seabrook Response to SAMA RAI 4k Table 2, rows IE #8 LOSPG and IE #9 LOSPG provide duplicate information. Row IE #9 can be disregarded.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 18 of 37 SAMA RAI 41 Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, the cost benefit analyses provided for IE #16 is a hardware installation to improve Component Cooling Water (CCW) reliability. In the evaluation for IE #16 on page 93 the associated SAMA case (i.e., CCTEI) is not identified as a cost beneficial SAMA. Yet, CCTE1 is identified as cost beneficial in Table I on page 65.

Please clarify this apparent discrepancy.

NextEra Energy Seabrook Response to SAMA RAI 41 PRA case CCTE1 provides the benefit basis for SAMA BE #9 (and BE #9A) and IE #16. These SAMAs are correctly shown to be potentially cost beneficial and are combined as new SAMA

195 in Table I on page 65. Table 2, SAMA IE #16 incorrectly refers to SAMA #59 and SAMA BE #2 as being related SAMAs. Table 2 as shown on page 65 of Reference 3 is revised as follows:

IE#16 LPCCB CDF Loss of PCCW Train B Related SAMA

59, BE #2 anzd BE #9.

Install hardware to improve the reliability of the CCW, thus reduce potential for loss of CCW initiators.

CCTE1 3 15 144K I(302K) 337K (709K) 300K This IE SAMA is related to SAMA #59, SAMVA, BE #2 and SAMIA BE #9. SAMA

59 and SAIVA BE #2 are -net coest beneficmal. Refer to SAMA BE #9 for evaluation of potential cost beneficial SAMA.

i ______

C L ________________

.i _________

I ___ +/- ____

C _______

U ________

+/-

SAMA RAI 4m Please provide the following with regard to the Phase II cost-benefit evaluations:

In Table 2 of Section 4.3, cost benefit analyses are provided for IE #23, #24, #25, #26, and

27, which are seismic initiators of different levels, (0.7g, 1.0g, 1.4g, 1.8g, and 2.5g) that lead to ATWS events (SAMA case NOATWS). No description of the associated SAMA is provided nor is the basis for the presented cost estimate (i.e., >500K). Table 2 shows that IE

28, which is an ATWS event with loss of Main Feedwater, is also grouped into this SAMA case. It is not clear why this initiating event (i.e., IE#28) can be grouped as part of a seismic upgrade related SAMA case. Please provide the SAMA description and basis for the cost estimate for these six initiator cases.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 19 of 37 NextEra Energy Seabrook Response to SAMA RAI 4m PRA case NOATWS conservatively considers the risk reduction assuming all ATWS initiating events (non-seismic and seismic) are eliminated. For convenience, seismic ATWS initiators #23 through #27 are evaluated under IE #23. ATWS initiator IE #28 is not a seismic-induced ATWS event and is evaluated separate from the seismic ATWS initiators.

Seismic ATWS initiating events IE #23 - 27 (0.7g, 1.0g, 1.4g, 1.8g, and 2.5g) lead to ATWS primarily due to support buckling of the reactor internals causing the control rods to jam and fail to insert for reactor shutdown. Potential modifications to reduce the seismic ATWS risk would include structural upgrades to the reactor internals to increase the seismic capacity. Modifying reactor internals would include detailed and complex analysis, procurement and installation. The cost of implementing structural modifications to the reactor internals is expected to be significantly greater than $500K based on comparison to other less complex hardware changes performed at Seabrook.

ATWS initiator IE #28 (AMFW) is an ATWS event with main feedwater initially available. The description in Table 2 of Reference 3 for AMFW incorrectly identified this event as ATWS with loss of main feedwater. The AMFW event is dominated by failure of the control rod assemblies to insert and failure to initiate emergency boration of the RCS. Possible hardware modifications to reduce the risk of this ATWS event would also include changes to reactor internals and emergency boration system with a cost to implement expected to be significantly greater than

$500K. It is noted that PRA case NOATWS is used to estimate the benefit of elimination of initiating event AMFW. Assuming that only ATWS event AMFW is completely eliminated, the maximum benefit would be approximately $20K. Table 2 as shown on page 95 of Reference 3 is revised as follows:

Not cost beneficial. Related SAMAs are #130, #131, #132, #174. PRA ATWS with case NOATWS conservatively assume that ATWS events do not occur IE #28 LEoss-ef Main Related SAMA 60K 139K

>500K (including seismically initiated ATWS).

IE#8 LERF Feedwater

130, #131, NOA-FWS 4

2 (126)0(92K AMFW Initially

132, #174 0126K)

(292K)

Available Cost of installing upgrades to significantly reduce the risk of ATWS is based on related SAMA costs.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 20 of 37 TABLE RAI-3-1-LL5 Seabrook SAMA', - BasicEvent RRW,.for Release:Category LL5 Basic Event (BE)*

'BE Descriptioni RRW Disposition / Evaluation HH.OALT1.FL Operator Action - Manual Alignment of Alternate Cooling to Charging Pumps before RCP seal LOCA 1.154 Evaluated in Reference 3 Table 2, BE #1 CCPI IA/B/C/D PCCW Pumps A, B, C, D Common Mode Failure to Start 1.139 Evaluated in Reference 3 Table 2, BE #2 EDESWGI IAB DC Power Panels A, B Common Mode Failure 1.121 Evaluated in Reference 3 Table 2, BE #3 HH.XOINEI.FA Operator fails to start containment injection early to prevent RPV failure 1.060 Evaluated in Reference 3 Table 2, BE #4 HH.OHSB1.FA Operator action to maintain stable plant conditions with SG cooling during transients 1.043 Evaluated in Reference 3 Table 2, BE #5 HH.XOINE3.FA Operator Fails to start containment injection early without AC power (gravity drain of RWST) 1.038 Evaluated in Reference 3 Table 2, BE #6 ZZ.SY1.FX Loss of offsite power subsequent to plant trip initiator 1.038 Evaluated in Reference 3 Table 2, BE #7 CCTE2171.FZ PCC Train A Temperature Element CC-TE-2171 transmits false low 1.029 Evaluated in Reference 3 Table 2, BE #9 CCTE2271.FZ PCC Train B Temperature Element CC-TE-2171 transmits false low 1.027 Evaluated in Reference 3 Table 2, BE #9A CCE I 7A.RT PCC Ht Ex 17A rupture/excessive leakage during operation 1.024 Evaluated in Reference 3 Table 2, BE #10 HH.ORHPI2.FA Operator action to restore charging/HPI/RCS for long term makeup after recovery of support 1.023 Evaluated in Reference 3 Table 2, BE #11 systems during various trans/accidents CCEI7B.RT PCC Ht Ex 17B rupture/excessive leakage during operation 1.022 Evaluated in Reference 3 Table 2, BE # 12 SWAFN64.FS CT SWGR Train A FAN SWA-FN-64 fails to start on demand 1.018 Evaluated in Reference 3 Table 2, BE # 13 SWFN51A.FS SW Cooling Tower FAN SW-FN-5 IA fails to start on demand 1.015 Evaluated in Reference 3 Table 2, BE # 14 SWAFN63.FS CT SWGR Train B FAN SWA-FN-63 fails to start on demand 1.015 Evaluated in Reference 3 Table 2, BE # 15 SWAFN71.FS CT Pump Area Train A Fan FWA-FN-71 fails to start on demand New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE # 15 1.014 (SWAFN63.FS), PRA Case SWAFN. The SWAFN71 SAMA scope, cost estimate and risk reduction are comparable to BE #15.

HH.ORHPII.FA Operator restores normal changing given recovery w/o SI NewLL5 BE SAMA. Not cost beneficial. This BE 1.014 previously evaluated in Reference 3 Table 2, SAMA BE#1 I (HH.ORHPII.FA), PRA Case ORHPIO.

FWP37A.FR Turbine Driven Pump FW-P-37A fails to run 1.014 New LL5 BE SAMA. Not cost beneficial. This BE

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 21 of 37 TABLE RAI-3-1-LL5."

Seabrook SAMA

- Basic Event RRW for Release Category LL5 Basic Event (BE)..

.B.EB Description RRW Disposition Evaluation previously evaluated in Reference 3 Table 2, SAMA BE #27 (FWP37A.FR), PRA Case TDAFW.

HH.OCSTMI.FL Operator established makeup to CST for long term SG cooling 1.012 New LL5 BE SAMA. Not cost beneficial. Refer to Table RAI-3-2 for evaluation.

SWAFN70.FS CT Pump Area Train B Fan FWA-FN-70 fails to start on demand New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE # 15 1.012 (SWAFN63.FS), PRA Case SWAFN. The SWAFN70 SAMA scope, cost estimate and risk reduction are comparable to BE # 15.

EDESWG6.FX 4kV Bus E6 fault New LL5 BE SAMA. Not cost beneficial. This BE 1.011 previously evaluated in Reference 3 Table 2, SAMA BE #34 (EDESWG56.FX), PRA Case SWGE561.

HH.SWOCCT.FA Operator fails to transfer SW from Ocean to CT 1.011 New LL5 BE SAMA. Not cost beneficial. Refer to Table RAI-3-2 for evaluation.

HH.OHSB3.FL Operator action to maintain stable plant conditions with SG cooling during SLOCA/SLB New LL5 BE SAMA. Not cost beneficial. This BE 1.011 previously evaluated in Reference 3 Table 2, SAMA BE #5 (HH.OHSBI.FA), PRA Case OHSBO.

SWADP66.FTO CT SWGR room relief damper SWA-DP-66 fails to open 1.011 New LL5 BE SAMA. Not cost beneficial. Refer to Table RAI-3-2 for evaluation.

HH.OFCRI.FL Operator fails to restore PCC from RSS before RCP seal failure (CR fire) 1.010 New LL5 BE SAMA. Not cost beneficial. Refer to Table RAI-3-2 for evaluation.

DGDGIB.FR3 DG-IB fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months New LL5 BE SAMA. Not cost beneficial. This BE 1.010 previously evaluated in Reference 3 Table 2, SAMA BE # 19 ([DDGG B.FR3), PRA Case NOSBOL.

SWV64.TONO SW Intake Return MOV SW-V-64 transfers open 1.010 New LL5 BE SAMA. Not cost beneficial. Refer to Table RAI-3-2 for evaluation.

SWADP65.FTO CT SWGR room relief damper SWA-DP-65 fails to open 1.009 New LL5 BE SAMA. Not cost beneficial. Refer to 1.009 Table RAI-3-2 for evaluation.

HH.OSGLC3.FL Operator fails to control SG level locally, with EFW thru EFW Discharge 1.008 New LL5 BE SAMA. Evaluated in Reference 3 1 Table 2, BE #33.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 22 of 37 TABLE RAI-3-1-LL5 Seabrook SAMA Basic-Event RRW for Release Category LL5 Basic Event (BE):.

BE Description RRW Disposition

.:Evaluation FWP37A.FSI Turbine Driven Pump TURBINE FW-P-37A fails to start on demand New LL5 BE SAMA. Evaluated in Reference 3 1.008 Table 2, BE #27A (FWP37A.FS I), PRA Case TDAFW.

[SWAFN70.FS CT Pump Area Fans FWA-FN-70 & 71 common mode failure to start on demand New LL5 BE SAMA. Not cost beneficial. Refer to SWAFN71.FS]

1.008 Table RAI-3-2 for evaluation.

[SWAFN63.FS CT SWGR Area Fans FWA-FN-63 & 64 common mode failure to start on demand New LL5 BE SAMA. Not cost beneficial. Refer to SWAFN64.FS]

1.008 Table RAI-3-2 for evaluation.

[EAHFN 180A.FS EAH Fans FN-I 80A & 180B common mode failure to start New LL5 BE SAMA. Not cost beneficial. Refer to EAHFN180B.FS]

1.007 Table RAI-3-2 for evaluation.

2SWFN51B.FRNO SW CT Fan 2SW-FN-5 I B fails to run New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE #14 1.007 (SWFN51A.FS), PRA Case SWFN. The 2SWFN5 lB SAMA scope, cost estimate and risk reduction are comparable to BE 4 14.

SWFN5 1 B.FRNO SW CT Fan SW-FN-5 I B fails to run New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE #14 1.007 (SWFN51A.FS), PRA Case SWFN. The SWFN51B SAMA scope, cost estimate and risk reduction are comparable to BE #14.

2SWFN51B.FS SW CT Fan 2SW-FN-51B fails to start on demand New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE #14 1.007 (SWFN5 IA.FS), PRA Case SWFN. The 2SWFN51B SAMA scope, cost estimate and risk reduction are comparable to BE # 14.

SWFN51B.FS SW CT Fan SW-FN-51B fails to start on demand New LL5 BE SAMA. Not cost beneficial. Similar to Reference 3 Table 2, SAMA BE #14 1.007 (SWFN5 IA.FS), PRA Case SWFN. The SWFN5IB SAMA scope, cost estimate and risk reduction are comparable to BE #14.

SWFN5IA.FRNO SW CT Fan SW-FN-5 IA fails to run 1.007 New LL5 BE SAMA. Not cost beneficial. This BE previously evaluated in Reference 3 Table 2, SAMA

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 23 of 37 TABLE RAI-3-1-LL5 Seabrook SAMA -Basic Event RRW for Release Category LL5:

Basic Event (BE)

BEDe1scription RRW Disposition / Evaluation BE #14 (SWFN5IA.FS), PRA Case SWFN.

DGDGIA.FR3 DG-IA fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months New LL5 BE SAMA. Not cost beneficial. This BE 1.007 previously evaluated in Reference 3 Table 2, SAMA BE #18 (DGDG1A.FR3), PRA Case NOSBOI.

EDESWG5.FX 4KV BUS E5 fault New LL5 BE SAMA. Not cost beneficial. This BE 1.007 previously evaluated in Reference 3 Table 2, SAMA BE #34 (EDESWG56.FX), PRA Case SWGE561.

HH.OHSB7.FL Operator fails long term control of RCS inventory & SG cooling New LL5 BE SAMA. Not cost beneficial. This BE 1.006 previously evaluated in Reference 3 Table 2, SAMA BE #32 (HH.OHSB6.FL), PRA Case OHSB670.

2SWFN51B.FS SW CT Fans 2SW-FN-5 lB, SW-FN-5IB and SW-FN-51A common mode failure to start New LL5 BE SAMA. Not cost beneficial. Refer to SWFN51IA.FS 1.006 SWFN51B.FS Table RAI-3-2 for evaluation.

HH.OSEPI.FA Operator fails to close SEPS breaker from MCB New LL5 BE SAMA. Not cost beneficial. This BE 1.005 previously evaluated in Reference 3 Table 2, SAMA BE #20 (HH.OSEP2Q.FA), PRA Case OSEPS.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure I / Page 24 of 37 TABLE RAI-3 SELL Seabrook SAMA - Basic Event RRW for Release.Category SELL Basic Event (BE)

BEDescription RRW Disposition Evaluation HH.XOINE3.FA Operator Fails to start containment injection early without AC power (gravity drain of RWST) 2.458 Evaluated in Reference 3 Table 2, BE #6 HH.XOSMPI.FA Operator aligns containment recirculation after core melt 1.230 Evaluated in Reference 3 Table 2, BE # 16 ZZ.CIS.PRE.EXIST Small pre-existing unidentified containment leakage 1.136 Evaluated in Reference 3 Table 2, BE # 17 ZZ.SYI.FX Loss of offsite power subsequent to plant trip initiator 1.072 Evaluated in Reference 3 Table 2, BE #7 DGDGIA.FR3 DG-IA fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.018 Evaluated in Reference 3 Table 2, BE #18 DGDG IB.FR3 DG-I B fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.018 Evaluated in Reference 3 Table 2, BE # 19 HH.OALTI.FL Operator Action - Manual Alignment of Alternate Cooling to Charging Pumps before RCP seal 1.018 Evaluated in Reference 3 Table 2, BE #1 LOCA HH.OSEP2Q.FA Operator fails to close SEPS breaker from MCB, given seismic event with SI signal 1.016 Evaluated in Reference 3 Table 2, BE #20 CCPI IA/B/C/D PCCW Pumps A, B, C, D Common Mode Failure to Start 1.015 Evaluated in Reference 3 Table 2, BE #2 EDESWGI lAB DC Power Panels A, B Common Mode Failure 1.014 Evaluated in Reference 3 Table 2, BE #3 SEPSDG2A.FR3 1-SEPS-DG-2-A fails to run within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.011 Evaluated in Reference 3 Table 2, BE #21 SEPSDG2B.FR3 I-SEPS-DG-2-B fails to run within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.011 Evaluated in Reference 3 Table 2, BE #22 DGDG1A/1B.FR3 DGIA and DG1B common mode failure to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.008 Evaluated in Reference 3 Table 2, BE #23 HH.OSEPIQ.FA Operator fails to close SEPS breaker from MCB, given seismic event 1.007 Evaluated in Reference 3 Table 2, BE #24 HH.XOINEI.FA Operator fails to start containment injection early to prevent RPV failure 1.006 Evaluated in Reference 3 Table 2, BE #4 HH.OCI2Q.FL Operator fails to close CSV-1 67 manually/locally 1.005 Evaluated in Reference 3 Table 2, BE #25 HH.OHSB I.FA Operator action to maintain stable plant conditions with SG cooling during transients 1.005 Evaluated in Reference 3 Table 2, BE #5 CSV167.FTC Penetration X-37 Isolation MOV CS-V-167 fails to close on demand 1.004 Evaluated in Reference 3 Table 2, BE #26 CCTE2171.FZ PCC Train A Temperature Element CC-TE-2171 transmits false low 1.004 Evaluated in Reference 3 Table 2, BE #9 FWP37S.FR Turbine Driven Pump FW-P-37A fails to run 1.004 Evaluated in Reference 3 Table 2, BE #27 CCTE2271.FZ PCC Train B Temperature Element CC-TE-2171 transmits false low 1.003 Evaluated in Reference 3 Table 2, BE #9A CE17A.RT PCC Ht Ex 17A rupture/excessive leakage during operation 1.003 Evaluated in Reference 3 Table 2, BE #10 EDESWG56.FX 4kV Emergency Buses 5 and 6 Fault (Common mode failure) 1.003 Evaluated in Reference 3 Table 2, BE #34.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 25 of 37 TABLE RAI-3-i-SE3 Seabrook SAMA -.Basic Event RRW for Release Category SE3 Basic Event (BE)

BE Description RRW Disposition i.Evaluation ZZ.SY I.FX Operator Action - Manual Alignment of Alternate Cooling to Charging Pumps before RCP seal 1.099 Evaluated in Reference 3 Table 2, BE #7 LOCA HH.OSEP2Q.FA Operator fails to close SEPS breaker from MCB, given seismic event & SI signal 1.029 Evaluated in Reference 3 Table 2, BE #20 DGDGIA.FR3 DG-1A fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.027 Evaluated in Reference 3 Table 2, BE # 18 ZZ.CIS.PRE.EXIST Small pre-existing unidentified containment leakage 1.026 Evaluated in Reference 3 Table 2, BE # 17 DGDGIB.FR3 DG-IB fails to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.026 Evaluated in Reference 3 Table 2, BE # 19 SEPSDG2A.FR3 I-SEPS-DG-2-A fails to run within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.014 Evaluated in Reference 3 Table 2, BE #21 SEPSDG2B.FR3 1-SEPS-DG-2-B fails to run within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.014 Evaluated in Reference 3 Table 2, BE #22 HH.OSEPIQ.FA Operator fails to close SEPS breaker from MCB, given seismic event 1.011 Evaluated in Reference 3 Table 2, BE #24 HH.OCI2Q.FL Operator fails to close CSV-167 manually/locally 1.011 Evaluated in Reference 3 Table 2, BE #25 DGDGIA/IB.FR3 DGIA and DGIB common mode failure to run for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 1.011 Evaluated in Reference 3 Table 2, BE #23 EDESWG56.FX 4kV Emergency Buses 5 and 6 Fault (Common mode failure) 1.004 Evaluated in Reference 3 Table 2, BE #34 CSV167.FTC Penetration X-37 Isolation MOV CS-V-167 fails to close on demand 1.004 Evaluated in Reference 3 Table 2, BE #26 FWP37A.FR Turbine Driven Pump FW-P-37A fails to run 1.003 Evaluated in Reference 3 Table 2, BE #27 SEPSDG2A.FS I-SEPS-DG-2-A fails to start on demand 1.003 Evaluated in Reference 3 Table 2, BE #28 SEPSDG2B.FS 1-SEPS-DG-2-B fails to start on demand 1.003 Evaluated in Reference 3 Table 2, BE #29

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 26 of 37 TABLE RAI-3-2 Seabrook SAMA -'Phase II Evaluation of'New LL5 Basic Event SAMA Candidates Total.Benefit(S RC Event'.-.

Related SAMA#'s

/

Re tionsk Baseline (with 2.1 Expected Basic Event (Rd u...c.,..:vent a.

Case

.l" multihlier)

SAMA Cost Evaluation Basic Event (BE)

Grou Description and Proposed Internal SAMA(sj CDF With

()

Pop.

Uncert.

Dose External Not cost beneficial. The SAMA concept is to enhance the operator's ability to reliably align and initiate makeup water to the CST during extended SBO conditions. The scope includes connection of an alternate portable, diesel-driven pump and valves to an independent water source. The PRA case Related SAMA conservatively assumes a continuous, Relatedwe a

nd successful CST suction source for EFW. The Operator

164. Hardware and cost of hardware and procedural changes to established procedural changes allow the alternate makeup capability is HH.CSTMI.FL LL5 makeup to CST to improve the CSTOI 1

I 35K 81K

>500K expecte tee the benefit. is for long term SG reliability of the CST (73K)

(171K) expected to exceed the benefit. It is noted cooling makeup for long that related SAMA #164 "Modify 10" term SG cooling Condensate Filter Flange" was shown to be potentially cost beneficial in Reference 3 Table 1. It is also noted that Seabrook is pursuing options for long term CST makeup in response to the post Fukushima FLEX requirements.

Cost to engineer and implement plant hardware and procedure modifications is based on Seabrook FLEX estimates.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1/ Page 27 of 37 TABLE RAI-3-2 Seabrook SAMA - Phase 1I Evaluation of New LL5 Basic.Event SAMA Candidates

%/ Risk Total. Benefit (S)

S- "

Related "M ts Reduction Baseline (with 2.1 Related SAMA-#s-Reduction.

2 Expected Ba i E e t B )

RC.:

E

: vent*:-

mul~itipler')*

Evauat I on

= : :

Basic Event (BEEve)t and-Proposed PRA Case mult-e

.SAMA.Cost Evaluation Group Description P.p Internal SAMA) yD With($

Dose>

Uncert.,

External_____

Not cost beneficial. The context of the operator action is to initiate a transfer of the ocean SW to the cooling tower given failure of the operating ocean pump with concurrent failure (or unavailability) of the standby Hardware and pump. The SAMA concept is to improve the SW ocean to cooling tower transfer procedural changes through implementation of enhanced Operator fails to to improve the 28K 66K automatic controls. PRA case SWOC6 HH.SWOCCT.FA LL5 transfer SW from reliability of SWOC6

<1 1

139K

>1.5M contivlyassumesse oft Ocean to CT transferring SW (59K)

(139K) conservatively assumes success of the system function from transfer. This would require a complex Ocean to CT control system to enhance the existing transfer control system.

The cost to engineer and implement new controls is estimated to exceed $1.5M based on comparison to other SAMAs having similar scope and complexity (Davis Besse SAMA CC-19).

Not cost beneficial.

The SAMA concept is to provide hardware changes to add redundant dampers within in the SWCT SWGR ventilation system. The PRA case conservatively assumes the damper is Hardware changes to guaranteed successful. This is similar to CT SWGR room reliability improvements for BE # 15 SWADP66iTO LL5 relief damper reliability of the SWA6 22K 52K

>240K (Reference 3 Table 2), but with a focus of SWA-DP-66 fails SWCT SWGR (46K) 0109K) improving damper reliability with installation to open ventilation system of redundant capability.

Cost to engineer and implement plant modifications and analysis judged comparable in scope and complexity to about half of the previously reported estimate in Reference 3 Table 2, BE #15.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 28 of 37 TABLE RAI-3-2 Seabrook SAMA - Phase II Evaluation of New LLS Basic Event SAMA Candidates Total'Beiefit (S)

% RiskBeei()

RC.,.,

Event Related"SAMARe ion

.Baseline(with 2.1 Related SAMA #'s Reduction Expected Basic Event (BE)

DREesription and Proposed PRA Case With SAMA Cost Evaluation

=

l~*)

Group Descr-iption.

.Io.

nteitr.na()"l.'

GroupASAMA(s)

CDF Pop.

W Dose Uncertp External Not cost beneficial. The SAMA concept is to provide hardware/procedure changes that would significantly improve reliability of restoring PCCW from the Remote Safe Shutdown (RSS) panel after a control room Operator fails to Hardware and fire. This would involve installing an restore PCC from procedure changes to 27K 62K automatic control system to initiate PCC.

HH.OFCRI.FL LL5 RSS before RCP improve operator OFCR0

<1 I

K

>200K thPatc con serva tiase the seal failure (CR capability to restore (56K)

(131K)

The PRA case conservatively assumes the fire)

PCC at RSS panel.

operator action is guaranteed to be successful.

Cost to engineer and implement plant modifications to improve the reliability of PCCW restoration is judged comparable to implementation of other Seabrook projects.

Not cost beneficial.

SW-V-64 is normally closed with power breaker locked open. The PRA conservatively considers a low probability that the valve is inadvertently opened causing a possible flow diversion of Hardware changes to SW discharge to the SW ocean intake. This SW Intake Return reduce the 25K 58K could lead to an eventual heat up of SW.

SWV64.TONO LL5 MOV SW-V-64 probability of SW64

<1 1

>300K The scope of the SAMA is to provide a transfers open spurious valve (52K)

(121K) remote monitoring and alarm system of the opening valve position to guard against inadvertent opening.

Cost to engineer and implement a valve monitoring and alarm system is judged comparable to implementation of other Seabrook projects.

Hardware changes to Not cost beneficial. The SAMA concept CT improve the 22K 52K and evaluation are similar to SWADP65.FTO LL5 relief damper reliability of the SWA6

<1 I

>240K SWADP66.FTO, for hardware changes to SWA-DP-65 fails SWCT SWGR (46K)

(109K) add redundant dampers within in the SWCT to open ventilation system SWGR ventilation system.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 29 of 37 TABLE RAI-3-2.

Seabrook SAMA -;Pbal*a EvaIuation of*eow*

LL5 BasicEvent SAMAý Candidates

% Risk ~

Total Benefit($->..........

RC E" en Related SAMA 4's Reduction BE..e.ine (t xpected Basic Event (BE) a

-r--

Pro vent ad

.Po p

.oed PR Case multiplier)

.ExpecNted Cost...

Group.DecrIip tion MA Internal Evaluation CA P2()-op.

Wh

.T Dose E tl Uncert.

Not cost beneficial. The SAMA concept is to provide hardware changes to add a redundant fan within in the SWCT pump Improve reliability room ventilation system. The PRA case CT Pump Area of SWCT pump conservatively assumes success of both fans SWAFN70.FS Fans FWA-FN-room ventilation8K 19KN-0adF 71wesuprsytmar SWAFN71.FS LL5 70 & 71 common fans; eliminate SW7071C 1

3 84K 196K

>480K FN-70 and FN-71 when support systems are SWAFN7I.FS mode failure to potential for (I76K)

(412K) available.

start on demand common mode Cost to engineer and implement plant failure modifications and analysis judged to exceed the scope and complexity of Reference 3 Table 2, BE # 15, and is expected to significantly exceed the benefit.

Not cost beneficial. The SAMA concept is to provide hardware changes to add a redundant fan within in the SWCT SWGR ventilation system. The PRA case SW7071C Improve reliability is representative of fans 63 and 64. The PRA CT SWGR Area of SWCT SWGR case conservatively assumes success of both Fans FWA-FN-room ventilation fans FN-63 and FN-64 when support systems SWAFN63.FS Fan 63 roo m ventilati 84K 196K are available. This SAMA evaluation is SWAFN64.FS mod m failine to 1

3 (176K)

(412K)

>480K similar to BE # 13 and BE #15 (Reference 3 mode failure to potential for Table 2) for improving SWCT SWGR start on demand common mode ventilation reliability.

Cost to engineer and implement plant modifications and analysis judged to exceed the scope and complexity of Reference 3 Table 2, BE #15, and is expected to significantly exceed the benefit.

Improve reliability Not cost beneficial. The SAMA concept is EAH Fans FN-of the EAH to provide hardware changes to add a EAFN18A.8A F 1B othlation fredundant fan within in the Emergency Air EAHFNI80A.FS LL5 180A & 180B ventilation fans; EAI80C 1

2 58K 136K

>480K Handling (EAH) system. The PRA case EAHFNf 80B.FS common mode eliminate potential (121K)

(285K) conservatively assumes that both EAH fans failure to start for common mode failure are success when support systems are I__

IIIIIII IIIavailable.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 30 of 37 TABLE RAT-3 Seabrook SAMA-Pha'se II Evaluation of-New LL5 Basic Event SAMA Candidates.

71, Total Benefit($)

0 5

Baseline (ah'2 I'

RC Event Related SAMA Ws Reduction Expected GRoup DEscriptivent and Proose PR Cas multip ier):

Basic Event (BE) nt:and:Proposed PRA Case- - -

SAMA Cost' Evaluation G*roup'

Description:

p o*

Internal:

SAMA(s)`

CDF Po.,

Unert Doe External Cost to engineer and implement plant modifications and analysis judged to exceed the scope and complexity of Reference 3 Table 2, BE #15, and is expected to significantly exceed the benefit.

Not cost beneficial. The SAMA concept is SW CT Fans Improve reliability to provide hardware changes to improve the 2SW-FN-51B, of the cooling tow'er reliability of the three SW Cooling Tower 2SWFN5 IB.FS SW-FN-5 IB and fans, eliminate 87K 205K fans. This SAMA scope is to install an SWFN51A.FS LL5 SW51C 1

3

>1M additional fan, similar to the evaluation for SWN BSSW-FN-5 IA potential for (184K)

(430K)BE#4(ernc3Tal2)

SWFN51B.FS cmomoe c

mnmdeBE

14 (Reference 3 Table 2).

common mode common mode failure to start failure The cost to engineer and implement this change is similar to that reported previously in Reference 3 Table 2, BE #14.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 31 of 37 TABLE RAI'-3-3, Seabrook SAMA " Phase lIEvaluation of New. CDF Initiating Event SAMA Candidates

~3ýTotal Befiefi t($)

-~~

Risk Related SAMA 4's Reduction Baseline (with 2.1 Expected

.nitiating Event Event Description and Proposed PRA Case I-,

multiplier*.,

SAMA Cost Evaluation (LE)

SAAS)-Internal Wt 3

~~CDF Po.-

3

~Dose-%

Uncert.-3 External Related SAMA IE IE SAMA LPCCA is the same as IE#16

16 (LPCCB).

(LPCCB) in Reference 3 Table 2, except that it is for PCCW Train A. The proposed Install hardware to SAMA is a modification to improve the LPCCA Loss of PCCW improve the CCTEI 144K 337K 300K reliability of CC-TV-2171/2271-1 & 2 Train A reliability of the (302K)

(709K)

(PCCW-A and PCCW-B). The SAMA is CCW, thus reduce described in SAMA BE #9 and as a new potential for loss of potentially cost beneficial SAMA # 195 in CCW initiators.

the SAMA Supplement, Reference 3.

Not cost beneficial. The SAMA concept is to improve the reliability of SW pipe break isolation for flood events occurring in the PAB via installation of control and initiation instrumentation logic. PRA case SWPI assumes a failure probability of E-02 to reflect improved isolation of SW flood initiators FIPSWA, F1PSWB, F2PSWA, Improve reliability of F2PSWB andF2PSWC (all located in the SW isolation in the PAB).

Major flood due to event of a large pipe 339K 795K It is noted that installation ofa SW FIPSWA rupture of SW Train break - install SWPI 4

11 339K 7M5

>2.5M isolation system would be complex and A in PAB automatic isolation (would introduce negative affects on SW initiation and control reliability, e.g., potential for inadvertent logic isolation causing a plant trip and potential for a complicated recovery due to loss of plant cooling. This negative risk impact is not considered in the PRA case.

The cost to engineer and implement a complex isolation system is estimated to exceed $2.5M based on comparison to other SAMAs having similar scope and

_complexity. Estimate assumes a control

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 32 of 37 TABLE RAI-3-3 Seabrook SAMA - Phase II Evaluation of New CDF Initiating Event SAMA Candidates

.%Risk Total Benefit (S)

Initiating Event Related SAMA N's Reduction BaEeline i "

Expected E

Event Description and Proposed PRA Case multi r"

SAMA Cost Evaluation ItE)iSAMA(s) ernal With CDF Dose Uncert.

External system previously evaluated for BE#5 at

>1.5M plus the cost of engineering and hardware changes to the system estimated at> lOM.

Not cost beneficial. LOSPP initiating event is covered by existing SAMAs. The LOSPP case conservatively maximizes the benefit by assuming that all plant-centered (hardware) LOSP events are completely Related SAMA # 13, eliminated.

power due to

14, #16, #24, #154, Cost of physical plant modifications and LOSPP switchyard

156, #160, #190 -

LOSPP 2

2 80K 188K

>7M analysis, is judged comparable in scope rall are hardware (168K)

(395K) and complexity to SAMA #156 for maintenance changes to reduce the installation of alternate offsite power risk of LOSP.

source that bypasses the switchyard.

It is noted that Seabrook Station has recently completed a multi-phase, multi-million dollar, comprehensive project to improve the reliability of the electrical switchyard.

Large flood due to Not cost beneficial.

F2PSWA rupture of SW Train Refer to F 1PSWA SWPI A piping in PAB Evaluated under SAMA F1PSWA.

Major flood due to Not cost beneficial.

FIPSWB rupture of SW Train Refer to FIPSWA SWPI B piping in PAB Evaluated under SAMA FIPSWA.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 33 of 37 TABLE RAI-3-3 Seabrook SAMA - Phase II Evaluation of New CDF Initiating Event SAMA Candidates Total Benefit(S) nin v RelatedPvSuaMAnerSARi1PABaseline (with 2.1 E

Reduct iono mul ti ExAM cted (IE)

EetDescriptioni and Proposed PRA Case Inera Ev A

os.

aluation

~-

SAMA(s)

CF Pop.

With()

¶

~~Dose xenl Uncert.

Large flood due to Not cost beneficial.

F2PSWB rupture of SW Train Refer to F1IPSWA SWPI B piping in PAjB Evaluated under SAMA F I PSWA.

Major flood due to rupture of Fire Provide flood and 14K 33K Not cost beneficial. Cost to engineer and F4TFPB Protection piping in spray protection of F4TFPB 1

0

>100K implement hardware changes exceed TB impacting offsite non-safety bus duct (30K)

(70K) estimated benefit.

power.

Provide fire Fire in Control eliminate or reduce 15K 35K Not cost beneficial. Cost to engineer and FCRAC Room - AC Power FCRAC 1

0

>100K implement hardware changes exceed Loss the potential for (3 1K)

(73K) estimated benefit major fire on MCR Panel Related SAMA IE

14 (LACPA).

Loss of Train B Improve Bus E6 LACPB Essential AC Power reliability and LACPA 44K 103K

>3M Not cost beneficial. Same as IE #14 (4kV Bus E6 eliminate or reduce (92K)

(216K)

(LACPA) in Reference 3 Table 2.

the potential for bus faults contributing to initiating events.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 34 of 37 TABLE RAI-3-3 Seabrook SAMA - Phase I1 Evaluation of New CDF Initiating Event SAMA Candidates

% Risk ' :Total Benefit ($)

%Risk Baseline (with 2.1 Expected

I ::::

I Related.-SAM A #'s Reduction

Expected,;[:*"

i * :

an rooed PA ae eucin ut~i~E.~

SAMA Cost*: i*i EValuation Initiating Event Event Description andProposed PRA Case InternaliCo (E)

SAMA(s)

Pop.

In With

($)

CD Dose Uncert.

External Large flood due to F2PSWC rupture of SW Refer to FIPSWA SWPI Not cost beneficial.

common return Evaluated under SAMA F I PSWA.

piping in PAB Hardware changes to eliminate or reduce 4K 10K Not cost beneficial. Cost to engineer and LOCI LG Large LOCA the potential for large LOC 1LG 1

0 4K K

>100K implement hardware changes exceed e(9K)

(21K) estimated benefit.

LOCA event

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 35 of 37 TABLE RAI-4-1 Seabrook SAMA-Phase 11 Sensitivity Evaluation of SAMA Candidates #91, #94, #99, #102 and #107

%.:Risk"*:

Total Benefit(S)

Expecte SBK Pteti Sensitivity Baseline (with 2.1 d SAMA SAMA Dei Description Case-Redu.tion multiplier)

Cost Evaluation Number Improvement PRA Case CDF Pop.

Internal&

With

__-_,,_.Dose External Uncert.

($)

Not cost beneficial. Sensitivity PRA case CBSP assumes the addition of a passive containment spray and cooling system. This case assumes that all three functions: spray injection, containment recirculation and heat removal can be performed passively, independent of plant support systems consisting of initiation signals, AC & DC power, PCCW cooling and RWST suction. The PRA case also assumes that the passive system is independent of common-Improved cause-failures among similar components. The independent failure probability Install a passive containment 1.7M 4.OM of the passive system is assumed to be I E-03. This failure probability is 91 containment spray CBSP 58 (3.5M)

(8.3M)

>10M consistent with the failure probability of passive components (tank and valve) spray system capability and assumes actuation is manual or automatic requiring instrumentation and control components. Based on this case, the benefit of a passive containment spray system could be higher compared to the previous evaluation, but significantly less than the expected cost Cost to engineer and implement a passive containment heat removal system same as that reported previously in the SAMA Supplement, Reference 3.

Not cost beneficial. This SAMA is to install a filtered containment vent large enough for decay heat removal while providing filtration of fission products.

Install a filtered Increased Sensitivity PRA case FVENT is used to represent the benefit of this candidate containment decay heat SAMA. This PRA case assumes that the filtered vent is able to prevent the vent to remove removal entire release frequency of LL3 (containment vent) and 80% of the release decay heat.

capability for 2M 4.6M frequency LL5 (basemat melt-through). Thus, 100% of LL3 and 80% of LL5 94 Option 1:

non-ATWS FVENT 0

69 are assigned to containment INTACT. Based on this case, the benefit of the Gravel Bed events, with (4.1 M)

(9.7M)

>20M filtered vent could be higher compared to the previous evaluation.

Filter; Option 2:

scrubbing of Cost to engineer and implement a filtered containment vent has been re-Multiple Venturi released fission assessed in this RAI to ensure that the cost estimate of a filtered containment Scrubber products vent system is realistic. The expected cost of a filtered vent system is in the range of $20M. This is based on a cost estimate of a filtered containment venting system for a two unit international plant, estimated at $48M.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 /Page 36 of 37 TABLE RAI-4-i Seabrook SAMA-Phase II Sensitivity Evaluation of SAMA Candidates #91, #94, #99, #102 and #107 o%

Risk Ttal Benefit ($)

Expecte SBK Potential Descripti Sensitivity Reduction Baseline (with 2.1 d SAMA SA Improvement escription multiplier)

Cost Evaluation Nuromenb..'er:::*::

PRA CaseCot.

Number CD.

'Pop.

Internal &

With (S)

Dose External Uncert.

Not cost beneficial. The context of this SAMA is to reduce the probability of containment overpressure failure by strengthen containment by adding ribbing (reinforcement) to the containment shell. Adding reinforcement steel would increase the containment ultimate pressure strength thus extending the time to recover offsite power (late) and the containment cooling function before failure Strengthen occurs. This sensitivity case assumes a factor of 10 reduction in the non-primary/seconda Reduced recovery probability of offsite power as a result of additional time that could ry containment probability of be available for recovery (late) before containment pressure failure occurs.

99 (e.g.. add containment CONST 0

4 117K 273K 11.5M Based on this case, the benefit of adding ribbing to strengthen containment ribbing to over-(245K)

(574K) could be much lower compared to the previous evaluation and significantly containment pressurization less than the expected implementation cost.

shell)

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 same as that reported previously in the SAMA Supplement, Reference 3.

United States Nuclear Regulatory Commission SBK-L-12185 / Enclosure 1 / Page 37 of 37 TABLE RAI-4-1 Seabrook SAMA - Phase 11 Sensitivity Evaluation of SAMA Candidates #91, #94, #99, #102 and #107

,%'Ris k Total Benefit ($)

Expecte, S

Potential D

rSensitivity Reduction Baseline (with 2.1.

d SAMAEvaluati Numb Improvement D

PRAri.Case multiplier)

Cost Evaluation CDF pop.

Internal &

With 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. PRA case CSBP is used to represent the possible benefit of this candidate SAMA. This case is representative because the passive decay heat removal system in case CBSP Construct a would prevent containment overpressure failure. The failure probability of IE-building to be Reduced 03, assumed for the passive spray and heat removal function in case CBSP, is a connected to probability of 1.7M 4.OM conservative failure probability for an active or passive large air handling and 102 primary/sec.

containment CBSP 0

58 56.7M (3.5M)

(8.3M) evacuation system with sufficient capacity to maintain low containment containment and over-accident pressure and prevent overpressure failure. This represents the maintained at a pressurization postulated reduction in the release challenge that might be realized by vacuum constructing an evacuation building to capture releases while preventing containment overpressure failure. Based on this case, the benefit of constructing an evacuation building could be higher compared to the previous evaluation but significantly less than the expected cost.

Cost to engineer and construct a new building adjacent to containment with ventilation systems capable of maintaining a negative pressure is the same as reported previously in the SAMA Supplement, Reference 3.

Not cost beneficial. The context of this SAMA is to reduce containment overpressure. failure events by adding a redundant containment spray system.

Seabrook currently has two trains of CBS. PRA case CBSR (containment building spray - redundant) assumes that an additional CBS system is installed Install a Increased and can provide all of the CBS functions of spray injection (1), spray redundant containment 29K 69K recirculation (R) and spray heat removal (X). The support systems for the 107 containment heat removal CBSR 0

1 (62K)

(144K)

>IOM additional CBS train are the same as the existing CBS support systems. Based spray system ability on this case, the benefit of adding a redundant containment spray train could be lower compared to the previous evaluation and significantly less than the expected cost.

Cost to engineer and implement a redundant spray system is the same as reported previously in the SAMA Supplement, Reference 3.

v t e Letter Sequence Response to RAI
TAC:ME3959, (Approved, Closed)
Initiation Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request Acceptance, Acceptance, Acceptance Supplement Administration Meeting, Meeting, Meeting Questions 31 July 2012 29 October 2010 21 December 2010 16 November 2010 3 January 2011 28 February 2011 4 March 2011 7 April 2011 20 March 2012 16 July 2012 1 November 2012 8 July 2016 8 July 2016 Answers 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 23 November 2010 22 January 2014 22 January 2014 22 January 2014 23 November 2010 23 November 2010 13 January 2011 16 March 2011 18 April 2011 13 September 2012 22 January 2014 6 September 2016 Results Approval, Approval, Approval, Approval, Approval, Approval, Approval, Approval, Approval Other: ML103070056, ML103360209, ML103360212, ML11126A365, ML11343A025, ML12352A141, ML13352A511, ML13353A536, ML15107A300, ML15173A356, ML15173A359, ML15187A129, ML18127A116, SBK-L-12053, To Severe Accident Mitigation Alternatives Analysis, License Renewal Application
MONTHYEAR2010-08-25 [Table View]

SBK-L-12185, To Severe Accident Mitigation Alternatives Analysis Response to RAI Request Dated July 16, 2012, NextEra Energy Seabrook License Renewal Application

Text

References:

Description:

Navigation menu

SBK-L-12185, To Severe Accident Mitigation Alternatives Analysis Response to RAI Request Dated July 16, 2012, NextEra Energy Seabrook License Renewal Application

Text

References:

Description:

Navigation menu

Search