ML13270A116

License Renewal Environmental Site Audit Re Byron and Braidwood Stations - Severe Accident Mitigation Alternative (TAC Nos. MF1834/1835, MF1790/1791, MF1832/1833, and MF1792/1793)

ML13270A116
Person / Time
Site:	Byron, Braidwood
Issue date:	10/29/2013
From:	Tam Tran Division of License Renewal
To:	Gallagher M Exelon Generation Co
Tam Tran 301-415-3617
References
TAC MF1792, TAC MF1793, TAC MF1832, TAC MF1833, TAC MF1834, TAC MF1835
Download: ML13270A116 (15)

Text

Mr. Michael Gallagher UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 29, 2013 Vice President, License Renewal Projects Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348

SUBJECT:

LICENSE RENEWAL ENVIRONMENTAL SITE AUDIT REGARDING BYRON AND BRAIDWOOD STATIONS-SEVERE ACCIDENT MITIGATION ALTERNATIVE (TAC NOS. MF1834/1835, MF1790/1791, MF1832/1833, AND MF1792/1793)

Dear Mr. Gallagher:

By letter, dated May 29, 2013, Exelon Generation Company, LLC (Exelon), submitted an application, including environmental reports, for renewal of operating licenses NPF-37, NPF-66, NPF-72, and NPF-77 for the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2. The staff of the U.S. Nuclear Regulatory Commission (the staff) is reviewing this application.

As a part of the environmental review, the staff plans to conduct a severe accident mitigation alternative (SAMA) audit at the Exelon office during the week of November 4, 2014, in accordance with the enclosed SAMA audit plan. The audit plan was informally provided to your staff, Ms. Nancy Ranik, by e-mail on October 7, 2013.

If you have any questions, please contact me by telephone at 301-415-3617 or by e-mail at Tam.Tran@ nrc.qov.

Sincerely,

~~,4~

Tam Tran, Environmental Project Manager Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-454, 50-455, 50-456, and 50-457

Enclosure:

As stated cc w/encl: Listserv

October 29, 2013 Mr. Michael Gallagher Vice President, License Renewal Projects Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348

SUBJECT:

LICENSE RENEWAL ENVIRONMENTAL SITE AUDIT REGARDING BYRON AND BRAIDWOOD STATIONS-SEVERE ACCIDENT MITIGATION ALTERNATIVE (TAG NOS. MF1834/1835, MF1790/1791, MF1832/1833, AND MF1792/1793)

Dear Mr. Gallagher:

By letter, dated May 29, 2013, Exelon Generation Company, LLC (Exelon), submitted an application, including an environmental reports, for renewal of operating licenses NPF-37, NPF-66, NPF-72, and NPF-77 for the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2. The staff of the U.S. Nuclear Regulatory Commission (the staff) is reviewing this application.

As a part of the environmental review, the staff plans to conduct a severe accident mitigation alternative (SAMA) audit at the Exelon office during the week of November 4, 2014, in accordance with the enclosed SAMA audit plan. The audit plan was informally provided to your staff, Ms. Nancy Ranik, by e-mail on October 7, 2013.

If you have any questions, please contact me by telephone at 301-415-3617 or by e-mail at Tam.Tran@nrc.gov.

Docket Nos. 50-454, 50-455, 50-456, and 50-457

Enclosure:

As stated cc w/encl: Listserv DISTRIBUTION: See next page ADAMS Accession No* ML13270A116 OFFICE LA:RPB2:DLR PM:RPB2:DLR NAME I King TTran DATE 10/1/13 10/22/13 OFFICE BC:RPB2:DLR PM:RPB2:DLR NAME BWittick TTran DATE 10/28/13 10/29/13 Sincerely, IRA/

Tam Tran, Environmental Project Manager Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulation PM:RPB2:DLR BC:AADB:DRA LJames JDozier 10/29/13 10/22/13 OFFICIAL AGENCY RECORD

Letter to M. Gallagher from T. Tran dated October 29, 2013

SUBJECT:

LICENSE RENEWAL ENVIRONMENTAL SITE AUDIT REGARDING BRAIDWOOD STATION-SEVERE ACCIDENT MITIGATION ALTERNATIVE (TAC NOS. ME1832/1833 AND MF1792/1793)

DISTRIBUTION:

HARDCOPY:

DLR RF E-MAIL:

Public RidsNrrDir Resource RidsNrrDirRpb1 Resource RidsNrrDirRpb2 Resource RidsNrrDirRerb Resource RidsNrrDirRarb Resource RidsNrrDirRasb Resource lois.james@ nrc.gov john.daily@ nrc.gov lindsay. robinson@ nrc.qov tam.tran@nrc.gov david. wrona@ nrc.gov brian.wittick@nrc.gov mitzi.young@ nrc.gov anita.ghosh@ nrc.qov christine.england@ nrc.gov cheryl.hausman@ nrc.gov sheila.ray@nrc.gov stuart.sheldon@ nrc.gov eric.duncan@ nrc.gov scott.burnell@ nrc.gov david.mcintyre@nrc.gov ivon ne. cou ret@ nrc. gov viktoria.mitlyng@ nrc.gov prema.chandrathil@ nrc.gov allan.barker@ nrc.gov harral.logaras@ nrc.gov john.robbins@ nrc.gov james.mcghee@ nrc.gov raymond.ng@ nrc.gov travis.daun@ nrc.gov brent. boston@ nrc.gov teresa. ray@ nrc.gov billy.dickson@ nrc.gov joel. wiebe@ nrc.gov michael. mahoney@ nrc.gov Nancy. ranek@ exeloncorp.com Robert.tarr@ exeloncorp.com ogle@gouker.net dwestin@ rmu.net charlesmedrano@ qmail.com prairiestatestrategies@ gmail.com Jarid. Funderburg@ mail.house.gov edstirling@ jvlnet.com rcolson @oglecounty.org allenchristianson 13@ gmail.com todd@ byronforestpreserve.com mharn@ oglecounty.org sara. faller@ exeloncorp.com twolf@ ilchamber.org byrontownship@ yahoo.com cmillard@es-il.org

Byron/Braidwood Severe Accident Mitigation Alternatives (SAMA) Audit Subjects/Questions for Discussion

[All questions apply to both Byron Station (Byron) and Braidwood Station (Braidwood) unless otherwise indicated]

1. Relative to the Level 1 Probabilistic Risk Assessment (PRA)

a. In Table F.2-1 the comment for PRA Revision SA states "Revised the model and data to address the PRA quality issues raised by CR#00142080 (1/30/03) against Rev. 5 model." Describe these quality issues and associated corrective actions.

b. As indicated in Table F.2-1, the core damage frequency (CDF) goes from 3.6E-5 to 1.7E-5 {1.6E-5} and back to 4.2E-5 {4.3E-5} for Revisions 6C, 6E3 and BB011 a, respectively. Explain the reason for the above changes in CDF.

{Braidwood values}

c. Review of the PRA history indicates periods of time where the Byron and Braidwood results are very similar followed by periods of time where they are different. While this may be the result of a lag in one site's revisions relative to the others, the description of the changes applies to both sites. It is also noted that for some changes the impact on one site is significantly different from that at the other site, for example: Rev. 5, Rev. 6F and Rev. BB011 a. Explain the reasons for these observations.

d. Section F.2.4 states that the 27 Level A and B facts and observations (F&Os) identified during the 1999 Westinghouse Owner's Group (WOG) peer review have been "closed out." Describe what is meant by "closed out", how this was verified and if these was considered in the 2012 self-assessment and the corrections incorporated in the PRA used for the SAMA.

e. Section F.2.4 identifies a 2012 self-assessment. Please clarify if this self-assessment was performed following the self-assessment process guidance in RG 1.200, Rev. 2, and NEI 00-02, Rev. 1. If not, discuss the purpose, objectives and procedures of the 2012 self-assessment.

f.

Describe any actual or planned potentially SAMA risk significant changes to hardware or operation (including changes in fuel cycle or fuel management) that have not been incorporated in the SAMA PRA.

g. Identify the systems shared or can be cross-tied between units and describe the modeling including the treatment of unavailability during outages of the other unit.

ENCLOSURE

h. The anticipated transient without scram (ATWS) CDF is given in Figures F.2-1 and F.2-2 as less than a value that is equal to 1% of the unit total CDF. Confirm that the Byron/Braidwood PRAs model A TWS, that actual values are available and that the identification of SAMA includes consideration of the A TWS. If not justify the approach taken. Provide the actual ATWS CDF.

i.

Confirm that the contribution of internal flooding initiated station blackout (SBO) and ATWS sequences are included in the values given in Figures F.2-1 and F.2-

2.

j.

From the description of important initiators on page F-5 it is apparent that loss of essential service water (SX) can be mitigated by recovery of main feedwater.

Discuss these scenarios.

k. Describe the Loss of Auxiliary Electric Power initiating event and how it is related to a Loss of Offsite Power (LOOP). What is the CDF contribution due to a LOOP?

I.

The Unit 2 CDF and percent contribution values given in Byron Figure F.2-2 are internally inconsistent. Provide a correct Figure F.2-2. (Byron only)

m. There is a significant difference between some of the contributions to total CDF between the Byron and Braidwood sites. For example: Loss of SX, Loss of component cooling water (CCW) and Small loss of coolant accident (LOCA).

Explain the reasons for these differences.

n. Section F.2.2 includes a characterization of the risk importance by initiating event, accident sequence, systems and operator actions. Describe how these rankings were used in the SAMA analysis.

o. In comparing important accident sequences given in Table F.2-2 between Byron and Braidwood it is noted that some have significantly different contributions to total CDF.

i. The reason for SLOC-02 difference is stated to be failure of SX007 valves to be throttled for Braidwood. Explain why this doesn't occur for Byron.

ii. Explain why the contribution from SLOC-06 is different (9% vs. 20-21%).

2. Relative to the Level 2 PRA

a. Provide a brief description of any reviews (e.g., in-house review, self-assessment, peer review, etc.) of the updated large early release frequency (LERF) model included in Rev. BB011 b1 of the PRA model and/or any reviews of WCAP-16341-P, "Simplified Level 2 Modeling Guidelines." Discuss the major reasons for the factor of 2-3 decrease in LERF shown in Table F.2-1 from implementing this updated methodology.

b. It is stated that "The Level 2 model is generally consistent with the "Simplified Level2 Modeling Guidelines," WCAP-16341-P." Describe any major areas where it is not consistent with these guidelines.

c.

Describe how SBO sequences and the potential for recovery of AC power are modeled in the Level 2 analysis.

d. From the containment event tree (CET) Figure F.2-4 it is seen that containment isolation failures lead to Sequence LERF09 which is release category LERF-CI.

Table F.3-8 indicates that this has a cesium iodide (Csl) release fraction of 0.0142. This analysis must assume that isolation failure is large enough so that early containment failures due to such things as hydrogen explosion and direct containment heating are prevented. If not it would appear that the Csl release fraction for release category LERF-CFE of 0.3 is more appropriate for the fraction of isolation failures that might have an early containment failure. Discuss the impact of this on the SAMA analysis.

e. Discuss the truncation limit used in evaluating the Level 2 model and the basis for determining its adequacy.

f.

Provide a further discussion of the use and meaning of the information contained in Table F.2-5, "Correlation of PDS to Sequences."

g. Table F.2-8 indicates about a 20% difference between Units 1 and 2 for Release Category LATE-CHR-NOAFW frequency. Describe the reason for this difference.

{Byron only}

h. Describe the fission product pathway modeled for ST6 (LERF-ISGTR).

i.

For the self-assessment finding on supporting requirement (SR) SC-AS, what is the post core damage mission time used for those sequences where core damage is assumed at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and is this adequate for crediting relevant mitigating systems?

j.

In the resolution of several self-assessment findings it is stated that "SOARCA insights were used to enhance the steam generator tube rupture (SGTR) analysis." Provide further information on the insights used.

k. Section F.2.3.2 indicates that containment failure due to direct containment heating is "0.000." Please clarify if this is a zero failure probability.

I.

Table F.2-7, the Modular Accident Analysis Program (MAAP) results for several cases were run to 200, 800 and 1600 hrs. Section F.3.5 and Table F.3-8 identify that the "MAAP cases were run to achieve a plateau of the release fractions, with primary attention paid to Csl and [cesium hydroxide] CsOH release fractions."

Provide additional discussions concerning the Csl and CsOH release fraction contribution occurring for Cases 4a, Sa, 6a, 9a 1 Oa and 12b (e.g. what were the relative increase in fractions for extending the MAAP cases to such long time frames; what was the fundamental cause of the continuing release, etc.).

3. Relative to External events

a. Provide more information on the 2009 Byron {2008 Braidwood} Fire PRA including: scope, status of development, major conservatisms and non-conservatisms, and QA activities, including reviews, undertaken. Discuss qualitatively the impact on the SAMA results of the conservatisms and non-conservatisms.

b. It is noted that the sum of the fire zone CDFs given in Section F.5.1.6.1 for Unit 2 is considerably higher than that for Unit 1 (7.03E-05 versus 4.38E-05). Provide justification to support the use of the Unit 1 fire CDF value in the external event multiplier. {Byron only}

c. The results from the 2008 Braidwood fire PRA were reduced by a factor of 1.262 to account for using the lower ignition frequencies from EPRI 1016735. A comparison of the important fire zones between Braidwood and Byron indicates that there are considerable differences between the results for the two sites and the validity of using the Byron reduction factor for Braidwood. Provide further justification for the use of the Byron factor or assess the impact on the SAMA results if this factor is not used {Braidwood only}.

d. A seismic CDF (SCDF) of 1 E-06 per year was used for determining the external events multiplier. No basis is given for the use of this value instead of the value for Byron {Braidwood} from the Generic Issue 199 analysis. Assess the impact on the SAMA analysis if the Gl-199 weakest link SCDF of 7.3E-06 {5.8E-06} per year is used.

e. Provide a discussion of the current status and the applicability of the results of Exelon's responses to the Fukushima's Near Term Task Force recommendations on the identification and evaluation of SAMAs relative to external events.

4. Relative to the Level 3 Consequence Analysis

a. Section F.4.1 calls out the population dose risk as 34.45 person-rem. However, SAMA summary tables and other locations in the Environmental Report (ER) reference 35.45 person-rem (or 35.5 person-rem). Please clarify {Byron only}.

b. Section F.3.7 discusses the meteorological data used in the SAMA analysis.

Please clarify whether all of the data is from onsite stations, or whether a local station was also used. If data from a local station was used, identify the local station and its location.

c. Section F.3.2 identifies that transient and special facility population data were included within the 1 0-mile radius. Provide the year 2000 transient and special facility population used in the SAMA analysis.

d. Tables F.3-2 and 3-3 provide the year 2046 population distribution used in the MELCOR Accident Consequence Code System, Version 2 (MACCS2) analysis.

Since the SECPOP2000 code was utilized to develop initial residential population estimates for each spatial element within the 50 mile region based on year 2000 census data, provide the year 2000 population distribution.

e. For Byron, Section F.3.2 identifies the year 2046 population as 1,734,765, and Section 2.6.1 identifies a population base of 1,247,087. For Braidwood, Section F.3.2 identifies the year 2047 population as 7,554,998, and Section 2.6.1 identifies a population base of 4,968,734. Please clarify if Section 2.6.1 is the year 2010 or 2000 population base.

f.

Section F.3.2 identifies that the year 2010 population data were not incorporated.

Briefly address how the 2010 population (from Section 2.6.1) compares to an estimated year 2010 population assuming the growth rates from Table F.3-1 for both Byron and Braidwood.

g. Section F.3.3 identifies that SECPOP economic data were not utilized due to known errors. Please clarify if this included the formatting error associated with population data. If not, provide an assessment of the impact on the SAMA analysis of using corrected population data.

h. Section F.3.6 of the ER noted that the longest evacuation time presented in the study was 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> 50 minutes. Please clarify if this was for a specific event evacuation or used for all event evacuations.

i.

Provide the values and associated assumptions made about the following MACCS2 input parameters: rainfall, mixing heights, building wake effects, plume release energy, land fraction, region index, watershed index, growing season, fraction of farmland, and shielding and protection factors.

j.

Section F.3.4 discusses ingestion dose. Identify the critical input parameters used to produce these results.

k.

MAAP Users Group News Bulletin, "MAAP-FLASH #68" (August 5, 2008),

recommended that users of MAAP versions 4.0.5 through 4.0. 7 (MAAP software version 4.0.6 was used in the SAMA analysis) include plant-specific values for the mass of the relevant fission product elements instead of the isotopic activity of those elements. Please clarify whether plant specific fission product mass or isotopic activity were used in the MAAP 4.0.6 analyses.

I.

For Braidwood Section F.7.4, the base maximum averted cost-risk (MACR) and decrease in MACR for including SAMA 15 in the base case do not match Section F.6.14 ($64.7M and $63.0M versus $46.4M and $45.2M). Please clarify.

{Braidwood only}

5. Relative to the Selection and Screening of Phase I SAMA Candidates

a. Section F.5.1.1 indicates that the external events multiplier was not used in determining the risk reduction worth (RRW) corresponding to the least cost SAMAs used in identifying potential SAMAs from the Units PRA importance. The reasons given are that 1) the fire results were reviewed separately for the purposes of SAMA identification, 2) the fire model is in an interim state. Provide further justification for not extending the review down to a RRW value which would encompass failures whose mitigation would have a benefit of $100,000 as determined in the Braidwood Phase II cost-benefit analysis. {Braidwood only}

b. Section F.5.1 indicates that Phase I SAMAs were based on Byron/Braidwood PRA results and PRA Group Insights. Explain what is meant by PRA group insights. Was this a separate task or were PRA group insights used to develop SA MAs for the importance and other reviews?

c.

Describe the steps taken to identify SAMAs involving improvements in procedures, training or available cues for the important human errors.

d. In Table F.5-1 (p. F-208) for basic event OVA1 SUPP----PNMM "UNIT 1 VA SUPPLY PLENUM MAINTENANCE" the only SAMA identified is SAMA 4, Installation of the "no-leak" [reactor coolant pump] RCP seals. Consider potentially lower cost alternatives such as proving portable ventilation during maintenance activities. {Byron only}

e. In Table F.5-1 (p. F-222) basic events 1AP-142-1---TRMM and 1AP-142-2---

TRMM appear to result in the unavailability of the same equipment, the startup feedwater pump and the same 2 of 4 condensate pumps. This implies that both system auxiliary transformers (SATs) are needed. Explain this situation. Since these are maintenance unavailability's, is it possible to use a temporary alignment while this maintenance is underway? {Byron only}

f.

SAMA 15 involves resolving regulatory issues associated with the inter-unit auxiliary feedwater (AFW) cross-tie. What is the status of this? What is the effectiveness of this SAMA if both units are tripped? If this cannot be implemented, consider other alternatives such as adding another diesel driven FW pump to mitigate the events where SAMA 15 is now cited as the only potential SAMA.

g. Wolf Creek SAMA 1 consisting of an emergency diesel generator (EDG) for supplying power for a charging pump and DC for use of the turbine driven FW pump, was not considered applicable for Byron since Byron does not have a turbine driven AFW pump and Byron's diesel AFW pump requires SX cooling.

Consider other SAMAs such as an EDG to supply power to a motor driven AFW pump as well as an existing charging pump.

h. Seven potentially cost-beneficial SAMAs in the Indian Point Unit 2 SAMA were discussed in ER Section F.5.1.3.6. The NUREG-1437 Supplement 38 identifies a total of 13 potentially cost-beneficial SAMAs. Address the applicability of these additional SAMAs to Byron.

i.

According to the NRC safety evaluation report (SER) on the Byron and Braidwood Individual Plant Examination (IPE) reports, the transmittal of the modified IPE reports indicated that a potential vulnerability involving a dual loss of SX due to internal flooding had been identified and that a modification was being considered. Confirm the implementation of this modification.

j.

From the discussion in Braidwood Section F.5.1.6.1 it is not clear how the fire zone CDF results from the 2008 Braidwood fire PRA were modified to account for using the lower ignition frequencies from EPRI 1 016735. Discuss how this was done. Provide further justification for this use of the Byron results or assess the impact on the identification and evaluation of fire specific SAMAs if the 2008 Braidwood fire PRA results are not modified or if a different approach to the modification is taken {Braidwood only}.

k. The Braidwood important fire zones were reviewed for potential SAMAs down to a zone CDF of 1 E-06 per year. This corresponds to a benefit of $474K. Provide assurance that use of this lower end cutoff does not result in missing some potentially cost effective SAMAs. {Braidwood only}

I.

In section F.5.1.6.1 the "major" scenarios contributing to the fire zone risk are identified. What is meant by major?

m. The Unit 2 fire zone results given in Section F.5.1.6.1 include a fire in Unit 1 Containment. It is stated that the fire induced failures are Unit 1 equipment and the fire is modeled as requiring a Unit 2 shutdown without the availability of untraced equipment, such as the main feedwater system. Would the same modeling logic be applicable to Unit 1 for a fire in Unit 2 containment? What about fires in other areas? {Braidwood only}

n. For several fire zones (e.g. Byron U1: 5.2-1, Byron U1: 11.3-1, Byron U2: 11.4-0 and Braidwood U 1: 1-1) SA MAs involving incipient detection are not included based on the statement, "the reliability of incipient detectors to prevent fires has neither been established nor accepted in the industry." Discuss whether an incipient detection SAMA is potentially cost-beneficial if the guidance in FAQ 08-0046 is applied in these fire zones. If determined to be potentially cost beneficial, consider including it in the SAMA list for future further evaluation.

o. Fire zone U2: 11.6-2 is the largest contributor to Unit 2 fire CDF and is analyzed using a bounding scenario. Discuss if insights from the analysis of the same or similar fire zone in Unit 1 can be used to identify potential fire specific SAMAs.

{Byron only}

p. The discussions of fire zones U2: 5.2-2 and U2: 5.1-2 (and others) in Section F.5.1.6.1 state:

"One of the larger contributors to the conditional core damage probability for the scenario is the operator failure to refill the DG B fuel oil tank. Automating the refill capability would help reduce the risk from these fires (SAMA 18)."

SAMA 18 is described as automating the refill of the diesel driven AFW pump fuel oil day tank, not DG B. Please clarify.

q. The discussion of Byron Unit 2 fire zone U2: 1-2, Braidwood Unit 1 fire zone U1:

1-1 and Braidwood Unit 2 fire zone U2: 1-2 indicates that one of the contributors in the "bounding" analysis" is a loss of coolant accident (LOCA) through the reactor head vent. If this is due to spurious opening of head vent valve(s),

consider the potential for removing power from these valve(s).

r.

Describe the extent to which new or improved Byron/Braidwood fire procedures to mitigate the important fires have been considered in the SAMA analysis.

s. Fire zone U1: 11.6c-O is the auxiliary building laundry room with the fire source described as total composed of transient initiators. If these are due to the operation of laundry room equipment, consider moving the laundry to another facility.

t.

For the discussion of seismic outliers in Section F.5.1.6.2 provide further information on the disposition of: {Byron only}

i. 1 AP1 OE, etc. How were the interaction issues addressed?

ii. 1 (2)DC03E, etc. Was the proceduralized operator actions implemented?

Also, for these and 1 ROOSE, etc., is relay chatter the only adverse consequence of cabinet interactions?

iii. 1 DC04E and 1 DC06E of IPEEE Table 3.3 does not appear to be addressed in Section F.5.1.6.2. Unit 2 items are but Unit 1 items are not.

u. Section F.5.1.3.1 identifies two additional Vogtle SAMAs (6, 16) that were found not cost beneficial (to Vogtle). However, the costs of implementation were moderate to low (816K and 25K, respectively, Vogtle ER, 2007 and RAI responses dated December 20, 2007 [ML073580627]). The base case cost-risk for Byron is approximately Sx greater than Vogtle, and the dose risk more than 1 Ox greater. Please clarify whether these SAMAs would be applicable or potentially cost beneficial to Byron or Braidwood.

v. SAMA 24 provides a reactor vessel cooling system to prevent vessel melt through. Based on the Byron IPE (ComEd 1994), plant procedures were implemented to direct reactor cavity flooding in core damage scenarios to provide a means of exterior vessel cooling (Section F.5.1.4). Please clarify why vessel cooling requires an additional cooling system to perform this function.

6. With Regard to Phase II Cost Benefit Analysis and Site-Specific Cost Estimates

a. Section F.6 provides only a brief description of the cost estimating process for determining the implementation cost for the various SAMAs. Provide a more detailed description of the cost estimating process including: whom or what organization performed the estimate, what is included or not included in the costs (for example: lifetime training and/or maintenance costs, inflation) and the treatment of cost savings due to the sharing of certain costs between units at the same site (or potentially between sites). If such cost sharing is not considered provide justification for this or the impact such cost sharing would have on the results of the SAMA analysis.

b. Provide further support for the $100,000 per unit value used for the cost of a procedure change and its applicability to Byron/Braidwood.

c. There is a wide difference between the costs for SAMA 1 ($46M) and that for SAMA 26 ($2.4M). Provide further information to support the cost estimates.

d. SAMA 1 would install a diesel driven SX pump in a new dedicated building. The reference Limerick cost estimate is justified as being similar in scope. However, it is not clear if the Limerick addition for a dedicated suppression pool cooling system was for a safety related system. Callaway incorporated a non-safety AFW pump and temporary EDG modifications (Callaway ER, 201 0). Address whether a non-safety AFW pump was considered.

e. The SAMA 12 cost estimate is based on an estimate that moving the SAT maintenance from on-line to an outage would require an additional 1 week added to each outage. Provide additional details why an outage must be extended versus being able to perform the maintenance in parallel with other outage work.

Provide a similar discussion for the SAMA 20 cost estimate.

f.

The CDF uncertainty multiplier is based on the BB011 a CDF. However, the point estimate CDF and summary table CDFs in section F.7.2 do not match the CDF in Table F.2-1. Please clarify. {Byron only}

g. Section F.7.2 gives, for the Byron BB011a model, a mean of 3.95E-05 and a point estimate of 4.26E-05 (which should be 4.17E-05) and for the Braidwood BB011 a model, a mean of 4.12E-05 and a point estimate of 4.26E-05. Usually the mean is greater than the point estimate due to the correlation of uncertainties. Explain these results.

h. SAMA 14, Section F.6.11 for Byron and F.6.13 for Braidwood, identifies that for SGTR scenarios, installing an automated RWST makeup system could provide

'indefinite' cooling, but for non-SGTR scenarios this action "would extend the time available for transition to recirculation mode." However, it is also stated that "it is assumed that the actions to control injection and perform a cooldown will eventually have to be taken to reach a successful endstate." Please clarify whether this applies to both SGTR and non-SGTR scenarios.

i.

In Section F.7.3, the MACCS2 sensitivity case for economic rate of return shows a change in dose consequence. This variable is effectively an interest rate.

Please clarify why there is an impact on dose consequence in the table of sensitivity results presented in Section F.7.3.

j.

In Section F.6.14 for Byron and F.6.16 for Braidwood, in the title of SAMA 17, should AMASC be AMSAC?

k. In Section F.7.2.2., should SAMA 16 have been found to be potentially cost beneficial instead of SAMA 17. {Byron only}

7. With Regard to Alternative/ Additional SA MAs

a. A cost beneficial SAMA identified in the Diablo Canyon submittal might represent an unevaluated SAMA candidate for Byron (i.e., Diablo Canyon SAMA 24-Prevent clearing of RCS cold leg water seals). Consider if this SAMA is applicable to Byron/Braidwood.

b. Consider alternatives to SAMA 14 such as the design and fabrication of a SG PORV gagging device to be used following a SGTR with a stuck open SG PORV.

Note that this is disposed of in the Byron/Braidwood SAMA assessments by citing information from a Diablo Canyon RAI response. This response was specific to the Diablo Canyon safety valve design. It is not clear if it is applicable to the Byron/Braidwood design. Consider if this SAMA is applicable to Byron/Braidwood.

c. While the discussion of basic event %RCS-RHR-DISCHIE concludes that SAMA 19 could be used to mitigate this interfacing system LOCA (ISLOCA), it also concludes that installing pressure monitoring instrumentation in the RHR lines would not be effective. Provide further information that would support this conclusion or consider a SAMA that may have less than 100% effectiveness.

d. SAMA 4 replaces the reactor coolant pump (RCP) seal with "no leak" seals at an estimated cost of $12.3M. Vogtle SAMA 7 identified the potential for installing enhanced seals that 'reduce' RCP seal leakage at a lower cost ($1.05M). Please clarify whether this is a similar RCP seal modification, and if yes, provide addition justification for the cost difference. If not, clarify whether this RCP seal modification is applicable to Byron/Braidwood.

e. In the Phase I SAMA development, installation of flood alarm was found to be not needed as the particular event was not applicable to Byron/Braidwood (e.g.

Indian Point SAMA 054). Discuss the more generic position of whether additional flood alarms would be potentially beneficial if applied to Byron/Braidwood flooding events.

Documents Available for Review:

1.

Byron Reference Exelon 2012a Exelon (Exelon Corporation). 2012. "Seismic Walkdown Report In Response to the 50.54(f)

Information Request Regarding Fukushima Near-Term Task Force Recommendation 2.3:

Seismic for the Byron Station, Unit 1." Appendix G. Report Number 1200108.20-R-001. Rev. 1.

Correspondence No.: RS-12-161. November 13.

2.

Byron Reference Exelon 2012b Exelon (Exelon Corporation). 2012. "Seismic Walkdown Report In Response to the 50.54(f)

Information Request Regarding Fukushima Near-Term Task Force Recommendation 2.3:

Seismic for the Byron Generating Station Unit 2." Appendix G. Report Number 12001 08.20-R-002. Rev. 1. Correspondence No.: RS-12-161. November 13.

3.

Braidwood Reference Exelon 2012a Exelon (Exelon Corporation). 2012. "Seismic Walkdown Report In Response to the 50.54(f)

Information Request Regarding Fukushima Near-Term Task Force Recommendation 2.3:

Seismic for the Braidwood Station, Unit 1." Appendix G. Report Number 1200108.1 0-R-001.

Rev. 0. Correspondence No.: RS-12-159. November 16.

4.

Braidwood Reference Exelon 2012b Exelon (Exelon Corporation). 2012. "Seismic Walkdown Report In Response to the 50.54(f)

Information Request Regarding Fukushima Near-Term Task Force Recommendation 2.3:

Seismic for the Braidwood Station Unit 2." Appendix G. Report Number 1200108.1 0-R-002.

Rev. 0. Correspondence No.: RS-12-159. November 16.

5.

The 1999 WOG peer review report and documentation of the closing of the resulting F&Os.

6.

The report documenting the 2012 self-assessment described in Section F.2.4.