GO2-11-092, Response to Request for Additional Information Related to the Review of the Severe Accident Mitigation Alternative Analysis

Response to Request for Additional Information Related to the Review of the Severe Accident Mitigation Alternative Analysis

ML11129A186
Person / Time
Site:	Columbia
Issue date:	05/06/2011
From:	Swank D Energy Northwest
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GO2-11-092
Download: ML11129A186 (39)

Text

David A. Swank ENERGY Columbia Generating Station Richland, WA 99352-0968 Ph. 509.377.2309 1F. 509.377.2354 NH daswank@energy-northwest.com May 6, 2011 G02-11-092 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001

Subject:

COLUMBIA GENERATING STATION, DOCKET NO. 50-397 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS

References:

1) Letter, G02-1 0-011, dated January 19, 2010, WS Oxenford (Energy Northwest) to NRC, "License Renewal Application"

2) Letter, G02-11-032, dated January 28, 2011, SK Gambhir (Energy Northwest) to NRC, "Response to Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application"

3) Letter dated March 10, 2011, NRC to SK Gambhir (Energy Northwest),

"Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application - Severe Accident Mitigation Alternative Review," (ADAMS Accession No. ML110670379)

Dear Sir or Madam:

By Reference 1, Energy Northwest requested the renewal of the Columbia Generating Station (CGS) operating license. In Reference 2, Energy Northwest submitted responses to several Requests for Additional Information (RAIs) related to the Severe Accident Mitigation Alternative (SAMA) analysis and provided the results of a sensitivity study performed using the Integrated Probabilistic Safety Analysis (PSA) Model Revision 7.1. Via Reference 3, the Nuclear Regulatory Commission (NRC) requested additional information pertaining to the sensitivity study provided in Reference 2.

Transmitted herewith in Attachment 1 is the Energy Northwest response to the RAIs contained in Reference 3. No additional SAMA candidates have been identified for implementation. Enclosure 1 contains Amendment 34 to the License Renewal Application (LRA) that was submitted in Reference 1.

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RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 2 of 2 No new commitments are included in this response.

If you have any questions or require additional information, please contact Abbas Mostala at (509) 377-4197.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the date of this letter.

Respectfully, D. A. Swank Acting Vice President, Engineering : Response to Request for Additional Information : Revised Tables for the PSA Rev. 7.1 Sensitivity Study : Amendment 34 to the LRA cc: NRC Region IV Administrator NRC NRR Project Manager NRC Senior Resident Inspector/988C EFSEC Manager RN Sherman - BPA/1 399 WA Horin - Winston & Strawn D Doyle - NRC NRR (w/a)

BE Holian - NRC NRR RR Cowley - WDOH

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 1 of 15 NRC Request:

1. Table B-4 does not provide an analysis of SAMA CC-21, which was screened as Criterion C. If modeled similar to SAMA CP-01, SAMA CC-21 (procedure change) would be cost-beneficial. Clarify the disposition of this SAMA.

Energy Northwest Response:

Severe Accident Mitigation Alternative (SAMA) candidate CC-21 proposes to revise procedures to align condensate to the low pressure injection subsystems as an alternate source of vessel inventory control should the suppression pool become too hot to support low pressure injection due to loss of pump suction head. This candidate was originally screened as Criterion C - Considered for Further Evaluation in Table E. 10-1 of the ER (Reference A). However, this SAMA candidate was not included in the cost benefit evaluation and no further discussion was provided.

There are three existing water sources that are available as alternative sources for injection: (i) service water (SW) from the spray ponds, (ii) fire water from the circulating water basin, and (iii) condensate from the hotwell with makeup from the condensate storage tank (CST). Each method will be discussed below.

SW cross-connect to the residual heat removal (RHR) system for vessel injection is a standard BWR design and contained in emergency procedures.

ii. Fire water has two pathways for injection: (a) The main fire water system (diesel and electric pumps) can be cross-tied to a condensate booster pump connection and supplied to the reactor pressure vessel by utilizing the feedwater pump bypass line. This injection source is contained in emergency procedures. (b) A fire hose can be connected to the 6 inch lines on the low pressure coolant injection (LPCI) piping through removal of a blind flange. The connection points to the three LPCI loops are available for injection by pumper truck with fire water.

The use of the 6 inch pathways are allowed under the Columbia Generating Station (CGS) extensive damage mitigation guidelines using fire water with the pumping force provided by a pumper truck. (Note: There is a spool piece connection to this blind flange that connects LPCI to the condensate system, but this is only used for refilling and flushing the lines after maintenance). Providing procedures for connection to condensate would provide very little benefit because pumping power is required to reach these connections points.

iii. Condensate from the hotwell and CST has multiple pathways for injection.

Assuming power is available to the condensate pumps or to the condensate and condensate booster pumps, the injection pathway is discharged directly to the vessel via the feedwater pump bypass lines. This injection pathway from the condenser hotwell to the reactor vessel is currently in CGS emergency

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 2 of 15 procedures. Emergency procedures also contain the ability to inject fire water to the condenser hotwell for additional inventory.

Additionally, since CGS has a direct gravity drain from the CST to the diesel-backed motor driven high pressure core spray (HPCS) pump (which can supply injection at high and low pressure) and the steam driven reactor core isolation and cooling (RCIC) pump, the CST inventory would only be available to the low pressure pumps on loss of these systems prior to CST inventory depletion.

It is noted that CGS has an abandoned 18 inch cross-connect from condensate to the suction of LPCI loop C. This connection has a blind flange installed to address concerns associated with secondary containment liquid bypass pathways. Use of this pathway for SAMA would require either draining of LPCI loop C to remove the blind flange or a plant modification to be able to isolate LPCI loop C for removal of the blind flange. It would also require condensate system pumping power which, if available, would be used as described above to inject into the vessel. Further, this pathway would only benefit Division 2 injection systems. Thus, this potential injection pathway would provide very little additional risk mitigation. There is also a potential risk increase for any of the low pressure injection pathways from other than the suppression pool in the event of re-pressurizing due to loss of depressurization control.

Thus, the screening criterion for SAMA candidate CC-21 is being revised to Criterion B

- Already Implemented, since the capability to provide alternate injection sources through multiple pathways currently exists and is proceduralized using SW, fire water and condensate for core cooling.

NRC Request:

2. Tables A-10, A-12, and A-14 provide a large early release frequency (LERF) importance analysis for internal, fire, and seismic events, respectively, and associated SAMA assessment. Tables A-6 through A-7 show that release category M/I is generally a much more significant contributor to population dose/economic impact than the LERF (H/E) release category, with release category H/I also being a significant contributor. Clarify how releases categories M/I and H/I are considered in the LERF importance analysis.

Energy Northwest Response:

Release categories M/I and H/I are not specifically considered in the LERF importance analysis. Therefore, a review was performed of basic event importance derived from release categories H/I and M/I to determine if additional SAMA candidates should be considered based on these release categories.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 3 of 15 Most of the important basic events applicable to H/I and M/I have already been reviewed in either the Level 1 or the LERF (H/E) basic event importance reviews (Tables A-9 through A-14 in Reference F). When applying the risk reduction worth (RRW) benefit to the basic events in these tables, if the event appeared in the Tables A-10, A-12, or A-14, the maximum benefit from the Level 1 core damage frequency (CDF) was used as a bounding value to derive a LERF contribution for screening purposes.

The LERF RRW benefit was based on the maximum CGS benefit by hazard (i.e.,

Internal Events - $500,446, Fire - $863,256, Seismic - $436,020) rather than that portion of the benefit attributed to the LERF (H/E) release category (i.e., Internal Events -

$45,805, Fire - $5,452, Seismic - $234,032). This conservative treatment of LERF was utilized in lieu of applying an exhaustive treatment by individual release category (twenty-seven tables of basic events consisting of the three hazards and nine release categories).

In reviewing the basic events identified from the H/I and M/I release categories, a bounding maximum benefit by release category was derived as follows: the release category frequency was multiplied by the consequence associated with the release category to estimate the annual off-site dose and annual off-site economic impact by release category. The annual off-site dose and annual off-site economic impact for a given release category are used to estimate the averted public exposure (APE) and averted off-site property damage costs (AOC). The next step estimated the averted occupational exposure (AOE) and the averted on-site costs (AOSC) by release category. The methodology used the total frequency for a given release category in the estimate of AOE and AOSC, rather than the total CDF. By modifying these aspects of the calculation, a "maximum" benefit per release category was determined as tabulated in Table 2-1.

Table 2-1: Maximum Benefit by Release Category Release Maximum Benefit ($)

Category Internal Events Fire Seismic OK $66,500 $123,834 $19,412 H/E $45,805 $5,452 $234,032 H/I $25,223 $8,519 $65,417 M/E $15,861 $1,277 $323 M/I $315,445 $661,862 $86,643 L/E $2,205 $2,230 $470 L/I $298 $657 $56 LL/E $6,294 $33,062 $4,962 LL/I $22,819 $26,262 $24,600 Total' $500,450 $863,155 $435,915 1

The difference intotal maximum benefit between Table 2-1 and that reported in Reference F is due to round-off approximations.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 4 of 15 When deriving the RRW benefit for basic events that appear only in the Level 2 model (that is, don't appear in the Level 1 CDF model), a bounding assumption was made that the accident sequences that contribute to the releases were eliminated rather than transferring to Containment OK, and thus a higher benefit was obtained.

Table 2-2 contains an assessment of H/I and M/l basic events meeting either one of the following criteria: 1) basic events that were below the importance cutoff for Tables A-9 through A-14 from Reference F but above the cutoff for the H/I and M/l release categories, or 2) basic events whose RRW benefit associated with the H/I or M/l release categories exceeded the RRW benefit derived for the Table A-9 through A-14 resolution sufficient to cause a change in that screening resolution or basis. Basic events that are modeling flags or post-CDF phenomenological events, which are not conducive to a SAMA candidate, are not included in the table. This review identified no new SAMA candidates but did identify additional human error basic events for consideration in operator training enhancement.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 5 of 15 Table 2-2: Additions to Basic Events Importance List for Release Categories H/I and MA Point Event Label Description Hazard RRW Estimate Resolution Seismic SAMA candidate OT-07R evaluates improving procedures (S)-M/I and operator training on systems and operator actions SWS-XHE-FO- Fail to switch to alternate Internal 1.31 determined to be important from probability safety SWinjection sources outside Events 1.092 7.1E-01 assessment (PSA) results. This SAMA candidate was Reactor Building (IE)-M/I 1.043 previously found to be cost-beneficial. This operator Fire action will be included under SAMA candidate OT-07R.

(F)-M/I No additional SAMA candidates are required.

SAMA candidate FL-06R, which provides additional non-destructive examination (NDE) and inspections, detects IE-FLD- Major plant service water IE-M/I 1.049 1.39E-06 line degradation and reduces the flooding frequency. This C507TSW-M (TSW) pipe break in C507 flooding initiator was included in the modeling. This candidate was evaluated for cost-benefit. No additional SAMA candidates are required.

SAMA candidate FL-06R, which provides additional NDE IE-FLD- and inspections, detects line degradation and reduces the C508TSW-M Major TSW pipe break in C507 IE-M/l 1.049 1.39E-06 flooding frequency. This flooding initiator was included in the modeling. This candidate was evaluated for cost-benefit. No additional SAMA candidates are required.

SAMA candidate OT-07R evaluates improving procedures Operator fails to align standby and operator training on systems and operator actions DEP-CRD- control rod drive (CRD) train IE-M/I 1.04 8.10E-06 determined to be important from PSA results. This SAMA SPCST--- and suppression pool cooling candidate was previously found to be cost-beneficial. This (SPC) early operator action will be included under SAMA candidate OT-07R. No additional SAMA candidates are required.

SAMA candidate FR-1 2R evaluates the installation of early detection in this fire area. This fire initiator was FT1D Fire initiating event in fire zone F-M/l 1.018 9.88E-03 included in the modeling. This candidate was evaluated for cost-benefit. No additional SAMA candidates are required.

SAMA candidate FR-1 2R evaluates the installation of IFT1D Fixed ignition source fraction in F-M/u 1.018 9.46E-01 early detection in this fire area. This candidate was fire zone T1D evaluated for cost-benefit. No additional SAMA candidates are required.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 6 of 15 Table 2-2: Additions to Basic Events Importance List for Release Categories H/I and M/I Event Label Description Hazard RRW Point Resolution

___________ ______________________Estimate Rslto This basic event assumes an environmental condition beyond the RHR equipment's environmental qualification due to an accident. Hardening RHR equipment to meet or approach the in-containment accident environmental profile survival is not possible. Having low pressure Reactor Building L2-PHE fails residual heatenvironment removal FM/I 1.1 9.98E-01 injection they sources are not outside impacted of the reactor by environmentally building, such that the accident is RXENV-PMP IE-M/I 7.781 (RHR) pump injection available at CGS. As discussed in RAI 1 for SAMA candidate CC-21, CGS has the ability to provide injection from the service water system, the fire water system, the condensate system, and by a fire pumper truck. This SAMA candidate is already implemented. No additional SAMA candidates are required.

CGS has a portable diesel generator (DG-4) that can provide DC power during a station blackout (SBO).

However, given the beyond design basis earthquake sufficient to cause seismic-induced failure of key plant DC power not available buildings, equipment contained within them are also following seismic plant damage assumed not available. Ifequipment does survive, DG-4 SEIS-PDS-V- state V(core damage and S-H/I 1.306 6.00E-01 would be a means to provide power to the battery DCPOW containment bypass caused by chargers. Inaddition, SAMA candidates AC/DC-01, seismic induced failures of the AC/DC-02, and AC/DC-03 evaluate improving battery RPV and/or key buildings) lifetime. These candidates were evaluated for cost-benefit. SAMA candidates AC/DC-04 and AC/DC-05 evaluate increased availability of DC systems. These candidates were evaluated in Reference F Table A-1 6.

No additional SAMA candidates are required.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 7 of 15 Table 2-2: Additions to Basic Events Importance List for Release Categories H/I and M/I Event Label ____________

Description Hazard RRW

______Estimate Point Resolution Rslto This is a human failure event to recover suppression pool cooling (SPC) during Level 2 progressions. Modeling of the SPC unavailability for Level 1 does not include this late recovery basic event. Given the longer time frame for potential recovery during the Level 2 progressions, a 0.1 recovery likelihood (the complement of 0.9) is modeled.

This modeling reflects a low estimated likelihood for recovery, given the potentially high radiation levels that L2-PHE- SP2 not recovered during Level IE-M/I 1.142 9.OOE-01 may limit issues.

accident local recovery actions The plant or other response on potential severe loss of SPC HRHURHRRC 2 progression cooling (not immediately recoverable) and inability to maintain suppression pool temperature below the heat capacity temperature limit (HCTL) will be to emergency depressurize. Ifunable to maintain containment pressure below the pressure suppression pressure (PSP) limit, the containment will be vented. Thus, this SAMA candidate is already implemented. Repair and restoration of SPC would be a high priority of the emergency response team process. No further SAMA candidates are required.

L2-PHE-AC- Fail to recover AC power prior F-M/I 1.069 1.00E+00 Fire / seismic losses of AC power are assumed to not be TD-FS1 to containment failure (Fire) recoverable. Not applicable as a SAMA candidate.

L2-PHE-AC- Fail to recover AC power prior S-H/I 1.438 1.00E+00 Fire / seismic losses of AC power are assumed to not be TD-FS2 to containment failure (Seismic) recoverable. Not applicable as a SAMA candidate.

Drywell fails given NC=F and SAMA candidate CC-02, which provides additional high high pressure core spray IE-M/I pressure injection capability, increases high pressure 1.800inetoavialtySAAcddteP-1whh L2-PHE-DI6- (HPCS) fails (loss of decay heat F-M/I 1.882 5.OOE-01 injection availability. SAMA candidate oP-na,which FAIL rmvlsqec)SM Iremoval sequence) S-M/ 1.633 provides addition SPO failure probability. capability, These reduces candidates werecontainment evaluated for cost-benefit. No additional SAMA candidates are required.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 8 of 15 NRC Request:

3. The Level 1 and Level 2 seismic basic events importance lists (Tables A-1 3 and A-14) identify, in addition to the two initiating events, only a few basic events, and those identified appeared to be flag events, split fractions, or success terms.

Neither seismically-induced failures nor random failures appear to be addressed in this importance analysis. Clarify how the seismic importance lists were developed. In the response, specifically discuss how the seismic probabilistic safety assessment (PSA) model treats both seismically-induced failures and random failures. If random failures are not included in the seismic analysis, explain how this model incompleteness impacts the SAMA evaluation.

Energy Northwest Response:

Random failures are included in the Seismic PSA model, but these did not rise above the importance cutoff level (for RRW benefit) to be included in Tables A-13 and A-14.

The seismic importance list from the Integrated PSA Model Rev. 7.1 was developed using the output of the WinNUPRA software program. The software contains a module that calculates importance metrics, including RRW, for all basic events that appear in the seismic PSA cutsets. The RRW benefit value for the cost of a procedure change

($12K) was determined using the maximum benefit for seismic events for Level 1 and LERF. Those basic events with an RRW benefit value equal to or greater than the cost of a procedure change at CGS were provided in Table A-13 and A-14 of Reference F.

NRC Request:

4. Table A-1 presents a total fire core damage frequency (CDF) of 3.6E-6/yr on the Rev. 6.2 Model column header, but the contributing fire sequences under that column header sum to 3.92E-6/yr. Environmental Report Table E.3-1, on the other hand, presents a total fire CDF of 7.4E-6/yr and Table E.4-5 presents release categories that appear to support (i.e., frequencies when summed equals 7.4E-6/yr) that total. Clarify these discrepancies.

Energy Northwest Response:

The total Fire CDF reported in Reference F Table A-1 (Fire) for PSA Rev. 6.2 is incorrect. This issue has been entered into the Energy Northwest corrective action program. The correct value for total Fire CDF is 7.4E-6/yr. A corrected Table A-1 (Fire) is provided in Attachment 2.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 9 of 15 NRC Request:

5. The truncation limits for internal events, fire and seismic models used in the quantification of Revision 6.2 Level 1 and Level 2 CDFs range from 5 x 10 14 to 1 x 10-8. In response to an NRC staff RAI (Sept. 17, 2010) Energy Northwest explained that in general a four-order difference between the calculated total and truncation limit was maintained, except in a few cases where a lesser difference was appropriate. In a telephone clarification, EN further explained that the expression "appropriate" referred to cases in which the calculated CDF appeared to converge using a lower truncation limit. Clarify if the following statement is applicable for both the Revision 6.2 and 7.1 PSA models: "In general a four-order-of-magnitude difference between the calculated total and truncation limit was maintained, except in a few cases where a lower truncation limit resulted in convergence between the calculated CDF and truncation limit."

Enervgy Northwest Response:

For Revision 6.2 of the PSA, a four-order-of-magnitude difference between the calculated total and truncation limit was maintained except in a few cases where a lower truncation limit resulted in convergence between the calculated CDF and truncation limit. For Revision 7.1 of the PSA, at least four orders of magnitude difference between the calculated total and truncation limit was maintained.

NRC Request:

6. The fire events listed in Table A-1 are almost entirely different from the fire events listed in Table E.3-7 of the Environmental Report. It appears that the Table A-1 fire events are identified by initiating event category rather than fire compartment (although the Table A-1 column header uses the term "Fire Compartment"). Clarify the difference between the fire events listed in the Environmental Report and table A-1 of the RAI response.

Energy Northwest Response:

The fire compartment labels used in Reference F Table A-1 (Fire) are different from those used in in the Environmental Report (ER) Table E.3-7. A footnote is added to Table A-1 (Fire) providing a cross-reference between the fire compartment labels. The footnote is included with the table provided in Attachment 2.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 10 of 15 NRC Request:

7. Additional Comment #2 discussed in the January 19, 2011, conference call (ADAMS Accession Number ML110400510) does not appear to have been addressed. The Phase I screening for SAMAs AC/DC-05, CB-02, CB-05, CC-1 3, and FR-02 need to be re-evaluated based on the total risk reduction benefit and associated implementation cost.

Energy Northwest Response:

Columbia specific estimates for the cost of implementation for SAMA candidates AC/DC-05, CB-02, CB-05, CC-1 3, and FR-02 have been developed. The entries in Table A-16 have been revised to reflect the revised implementation costs. Corrected pages from Table A-1 6 have been provided in Attachment 2.

NRC Request:

8. Comment #2 discussed in the January 19, 2011, conference call (ADAMS Accession Number ML110400510) does not appear to have been entirely addressed. Explain the reason for the increase in fire population dose risk for SAMAs CW-02, CW-03, and CW-04 (Analysis Cases 18 and 19 in Table B-3) and the increase in internal events CDF and population dose-risk for SAMA AC/DC-30R (Analysis Case 45 in Table B-2).

Energy Northwest Response:

The increase in fire population dose risk for SAMA candidates CW-02, CW-03 and CW-04 results from a redistribution of plant damage state (PDS) frequencies computed by the event tree quantifications. When an event tree branch failure probability decreases as a result of a mitigation alternative, the corresponding success branch probability increases. These changes in the branch point probabilities increase some PDS frequencies and decrease others.

This redistribution of PDS frequencies for SAMA candidates CW-02, CW-03 and CW-04 produces net increases in the frequencies for release in the Level 2 PSA quantification, and thus increases in population dose risks.

PDS 11B0, in particular, is higher for CW-02, CW-03 and CW-04, by about 1 E-6/rx-year.

PDS 1BO involves loss of decay heat removal scenarios. For PDS 11B0, all available injection systems have been previously credited in the Level 1 analysis, and the Level 2 PSA provides minimal credit for recovery of injection systems. The net result is a net increase in the frequency for release and an increase in fire population dose risk.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 11 of 15 This phenomenon is more likely to occur when the delta-CDF is relatively small, and it is more likely for Fire PSAs. Since some event failure branch probabilities are relatively high due to fire impacts, the corresponding changes in success branch probabilities are larger when mitigation alternatives are examined.

For SAMA candidate AC/DC-30R, incorrect impact vectors were discovered to have been used. This issue has been entered into the Energy Northwest corrective action program. The Phase 2 calculation for AC/DC-30R was corrected and those portions of Tables B-i, B-2, B-3, B-4, B-5, B-7 and B-8 containing the results for AC/DC-30R are provided in Attachment 2. Based on the corrections, there were no changes to the disposition of AC/DC-30R.

NRC Request:

9. The calculated total for the internal, fire, and seismic events listed for the release categories presented in Tables A-3, A-4, and A-5 (5.61 E-06/yr, 1.02E-05/yr, and 4.31 E-06/yr respectively) are not the same as the total CDFs given for internal, fire, and seismic events in Table A-1 (7.4E-6/yr, 1.4E-6/yr, and 4.9E-6/yr respectively). Explain these differences. Also, the percentage contributions presented in Tables A-3, A-4, and A-5 total to much less than 100% for each table (e.g., totals to 75% in the case of the internal events release categories).

Ener-iv Northwest Response:

The "Containment OK" category frequencies were not correctly reported in Tables A-3, A-4, and A-5 in Reference F (they were shown with frequencies of zero.) This issue has been entered into the Energy Northwest corrective action program. The Containment OK category frequencies are computed and have been placed in revised Tables A-3, A-4, and A-5, which are provided in Attachment 2.

NRC Request:

10. Table A-1 (seismic) shows that the CDF for a couple of the seismic damage states (i.e., S2P2, S20P2) was completely eliminated in PSA Rev. 7.1. Explain.

Enerczv Northwest Response:

S2P2 and S20P2 are seismic station blackout (SBO) event trees with RCIC successful.

The RCIC system success criteria in PSA Rev. 7.1 require success of the condensate storage tank, which is failed by the modeled seismic events. Therefore all of the S2P2 and S20P2 accident sequence cutsets transfer to the seismic SBO event trees with RCIC unavailable, S2P3 and S20P3.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 12 of 15 NRC Request:

11. Section 2.2 provides a sensitivity analysis of the assumed 0.3 hot short probability (if CPTs were known to be present for the circuits; otherwise, 0.6) for three selected SAMAs that address fire events. The basis for selecting the three SAMAs is the RRW significance of the hot shorts they address and that they address numerous important functions. Clarify Energy Northwest's basis for believing that the sensitivity analysis results for these three SAMAs bound the effect for other fire SAMAs. In the response, specifically address the potential for multiple hot shorts in series and whether the factor of 2 impact determined for SAMA FR-07b is bounding for the fire SAMAs. Alternatively, specifically assess the impact of using a 0.6 hot short probability (or 0.3 if these circuits are known to be protected by CPTs) on the analysis results for fire-related SAMAs FR-08, FR-09R, FR-12R, and FR-11R.

Also, the hot short probability assumption could result in an underestimate of the estimated risk reduction for SAMAs identified principally to address internal events if the SAMA addresses cutsets that contain hot shorts. Assess the impact of using a 0.6 hot short probability (or 0.3 if these circuits are known to be protected by CPTs) on the analysis results for non-fire-related SAMAs AC/DC-15, AC/DC-23, AC/DC-27, CC-02, CP-01, CW-02, CW-07, CC-24R, FW-05R, and OT-09R, which have significant fire risk reduction contribution to the total estimated benefit.

Energy Northwest Response:

To provide additional confidence that the use of the 95th percentile uncertainty factor recommended in NEI 05-01, "Severe Accident Mitigation Alternatives (SAMA) Analysis Guidance Document," sufficiently bounds the parametric uncertainty associated with hot short probabilities, the additional SAMA candidates specified above were quantitatively evaluated using the following approach (consistent with that in Reference F):

i) For selected hot short events (nine total), a circuit evaluation was performed to verify that a control power transformer (CPT) was present. The hot short probabilities for these nine hot short events remained at 0.3 in the model, which is the highest best estimate value for circuits with a CPT per NUREG/CR-6850 "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities."

ii) For all other hot short events, a circuit evaluation was not performed, and the model was modified to revise the remaining hot shorts to a probability of 0.6, which is the highest best estimate value for circuits without a CPT per NUREG/CR-6850. This sensitivity evaluation is judged to be a bounding calculation for this model incompleteness.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 13 of 15 The sensitivity evaluation results are shown in Table RAI-1 1-1. The largest delta-CDF factor increase produced by the sensitivity evaluation was 1.38 (SAMA candidate CC-24R), which is well within the Fire uncertainty factor of 2.6. There were no changes to Internal Events and Seismic delta-CDFs as only the fire hazard component was affected. This sensitivity demonstrates that the parametric uncertainty associated with hot shorts does not alter the cost-beneficial conclusions. Therefore, no further evaluation of the SAMA cases is performed.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachnient 1 Page 14 of 15 Table RAI-11-1 Hot Short Probability Sensitivity Evaluation for Additional SAMA Candidates SAMA Description Base Fire Sensitivity Original Fire Sensitivity Fire Delta-CDF Candidate CDF Fire CDF Delta-CDF Delta-CDF Factor Increase AC/DC-1 0-1 Provide an additional diesel generator. 1.37E-05 1.43E-05 1.34E-6 1.35E-6 1.01 AC/DC-23-1 Develop procedures to repair or replace failed 4 kV 1.37E-05 1.43E-05 2.60E-7 2.60E-7 1.00 breakers Install permanent hardware changes that make it AC/DC-27-1 possible to establish 500 kV backfeed through the 1.37E-05 1.43E-05 5.23E-6 5.72E-6 1.09 main step-up transformer CC-02-1 Provide an additional high pressure injection pump 1.37E-05 1.43E-05 1.02E-5 1.08E-5 1.06 with independent diesel CP-01-1 Install an independent method of suppression pool 1.37E-05 1.43E-05 7.37E-6 7.59E-6 1.03 cooling CW-02-1 Add redundant DC control power for pumps 1.37E-05 1.43E-05 7.20E-7 6.60E-7 0.921 CW-07-1 Add a service water pump 1.37E-05 1.43E-05 1.74E-6 1.78E-6 1.02 Evaluate revising procedures to backfeed the high CC-24R-I pressure core spray (HPCS) system with SM-8 to 1.37E-05 1.43E-05 1.28E-6 1.77E-6 1.38 provide a third power source for HPCS FW-05R-I Examine potential for operators to control reactor 1.37E-05 1.43E-05 9.60E-7 9.60E-7 1.00 feedwater (RFW) and avoid trip Install early fire detection in the following reactor FR-09R-I building physical analysis units: R-1B, R-1D, R-1J, 1.37E-05 1.43E-05 2.12E-6 2.21 E-6 1.04 R-1L, R-1C, R-1K FR-08-1 Protect RHR and SW cables from fires 1.37E-05 1.43E-05 7.71 E-6 8.23E-6 1.07 OT-09R-I For the non-loss of coolant accident (LOCA) initiating 1.37E-05 1.43E-05 1.14E-6 1.14E-6 1.00 events, credit the.Z (PCs recovery) function FR-1 2R-I Install early fire detection in the following physical 1.37E-05 1.43E-05 1.70E-6 1.70E-6 1.00 analysis units: T-1A, T-12, T-1C, T-1D Install early fire detection in the following physical FR-i 1R-I analysis units: RC-02, RC-03, RC-05, RC-04, RC- 1.37E-05 1.43E-05 7.67E-6 8.11 E-6 1.06 07, RC-08, RC-11, RC-14, RC-13, RC-IA 1The CW-02 sensitivity produces a slightly reduced benefit relative to the base case. The reduced benefit results from particular fire accident sequences in which fire-related mechanisms that cause complete failure of RCIC in the base cases are removed by the mitigation alternative. Although RClC is not susceptible to outright failure for this mitigation alternative, the system is still susceptible to hot short induced mechanisms of failure for the sequences in question. Due to the higher hot short probabilities for the sensitivity, the delta CDF for the applicable accident sequences is smaller in the sensitivity quantification, and thus, the benefit is reduced.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 15 of 15 NRC Request:

12. Table 2-3 notes that the "Late" time category (i.e., greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) is not used in PSA model Rev. 7.1. Clarify that all Level 2 sequences are mapped into 1"early" or "intermediate" release categories. If not, assess the impact of this incompleteness on the results of the sensitivity study.

Energy Northwest Response:

All Level 2 sequences are mapped into "early" or "intermediate" release categories.

Table 2-3 Note (3) from Reference F is revised to provide this additional clarification.

This table is provided in Attachment 2.

References:

A. Letter, G02-1 0-011, dated January 19, 2010, WS Oxenford (Energy Northwest) to NRC, "License Renewal Application" B. Letter dated July 1, 2010, NRC to WS Oxenford (Energy Northwest), "Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application - SAMA Review," (ADAMS Accession No. ML101760421)

C. Letter, G02-10-138, dated September 17, 2010, SK Gambhir (Energy Northwest) to NRC, "Response to Request for Additional Information License Renewal Application" D. Letter dated November 10, 2010, N RC to SK Gambhir (Energy Northwest),

"Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application - SAMA Review," (ADAMS Accession No. ML102870984)

E. Letter dated December 2, 2010, NRC to SK Gambhir (Energy Northwest), "Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application - SAMA Review," (ADAMS Accession No. ML-103330246)

F. Letter, G02-11-032, dated January 28, 2011, SK Gambhir (Energy Northwest) to NRC, "Response to Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application" G. Letter dated March 10, 2011, NRC to SK Gambhir (Energy Northwest), "Request for Additional Information for the Review of the Columbia Generating Station License Renewal Application - Severe Accident Mitigation Altemative Review,"

(ADAMS Accession No. ML110670379)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 1 of 20 Energy Northwest Sensitivity Study Based Upon the Columbia Generating Station Integrated Full Power Probabilistic Safety Assessment Model Revision 7.1 dated September 2010 Revised Tables Note: Revision bars or shading are used to indicate revisions.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 2 of 20 Table 2-3 RELEASE SEVERITY AND TIMING CLASSIFICATION SCHEME(1 )

Release Severity Release Timing Time of Initial Release"'

Relative to Time for Classification Cs Iodide % in Classification General Emergency Category Release Category Declaration High (H) Greater than 10 Late (L)131 Greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Medium or Moderate 1 to 10 Intermediate (I) 3 to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (M)

Low (L) 0.1 to 1 Early (E) Less than 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />(4)

Low-low (LL) Less than 0.1 No iodine (OK) 0 RADIONUCLIDE RELEASE CATEGORIES DERIVED FOR COLUMBIA GENERATING STATION Time of Magnitude of Release Release H M L LL E H/E M/E LIE LL/E I H/I M/I L/ I LL/

L ` H/L M/L LUL LL/L (1) The combinations of severity and timing classifications results in one OK release category and 12 other release categories of varying times and magnitudes.

(2) The cue for the General Emergency declaration is taken to be the time when EALs are exceeded.

The declaration of the General Emergency begins the time for evacuation.

(3) The "Late" time category is not used for the Integrated PSA Model Rev. 7.1. All Level 2 sequences are mapped into either the "Early" or "Intermediate" release categories.

(4) Evacuation time for the Columbia EPZ is found to be less than 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 3 of 20 Table A-1 (Fire): Comparison CDF Contributions for PSA Models Rev. 6.2 and Rev. 7.12 Fire Compartment 3 Rev 6.2 Fire Rev. 7.1 Fire Fire CDF Percenta e CDF (Irx-yr) CDF (Irx-yr) Difference Increase Discussion Total 7,4E-06 1.37E-05 6.31 E-06 85%

The Rev. 7.1 FPSA modeling of long term RCIC operation differs from the Rev. 6.2 FPSA in crediting RCS makeup inthe event RCIC fails to continue to run due to containment back-W07 (Radwaste 467' pressure. The assumption that an RCS Division 2 Electrical 9,0E-08 1.7E-06 1.6E-06 21% makeup source was available was not carried Equipment) forward for Rev 7.1 FPSA. The Integrated PSA Model Rev. 7.1 was established for SAMA evaluations and this conservatism is judged appropriate for the SAMA application. This resulted in an increased importance for fire compartment W07.

Based on the revised Rev. 7.1 RFW fault tree model, RFW is now failed if a full compartment TlC (Turbine 5.2E-08 1.3E-06 1.3E-06 17% burnout occurs. Modeling of additional Generator East 441') dependencies inthe Rev 7.1 Internal Events model identified increased importance to this fire compartment.

Rev. 7.1 has a conservatism in modeling the failure of some Division 2 equipment associated with this fire compartment. The investigation into this conservatism was not completed prior W04 (Radwaste 467' to performing the sensitivity study. When this Division 1 Electrical 8.4E-07 1.7E-06 8.6E-07 12% conservatism is removed, the Rev. 7.1 W04 Equipment Room) compartment fire CDF decreases by a factor of about two. Overall fire CDF decreases by about 6%. This modeling would not adversely affect the SAMA analysis results by screening out a cost-beneficial SAMA candidate.

W08 (Radwaste 467' 3.6E-07 9.7E-07 6.1E-07 8% See discussion for compartment W07.

Switchgear Room #2) 1 1 E

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachment '2 Page 4 of 20 Table A-1 (Fire): Comparison CDF Contributions for PSA Models Rev. 6.2 and Rev. 7.12 Fire Compartment 3 Rev 6.2 Fire Rev. 7.1 Fire Fire CDF Percentaqe CDF (/rx-yr) CDF (Irx-yr) Difference Increase Discussion Total 7,4E-06 1.37E-05 6.31 E-06 85%

The Rev. 6.2 FPSA credits one train of RHR to be available and not failed for a fire in this compartment. This was not carried forward to the Rev. 7.1 integrated model. The investigation to confirm this modeling W03 (Radwaste 467'- assumption was not completed prior to 525'Cable Chase) 4.5E-07 9.4E-07 5.OE-07 7% performing the sensitivity study. When this conservatism is removed, the Rev. 7.1 W03 compartment fire CDF decreases by a factor of about two. Overall fire CDF decreases by about 3%. This modeling would not adversely affect the SAMA analysis results by screening out a cost-beneficial SAMA candidate.

The Rev. 6.2 FPSA model provided non-repair probabilities to recover fire-induced losses of W14 (Radwaste 467' 1,0E-06 1.4E-06 4.5E-07 6% offsite power. This assumption was removed Switchgear Room #1) for Rev 7.1 integrated FPSA. This resulted in an increase in risk importance in the Rev 7.1 model for this compartment.

R1 C (Southeast 2.IE-08 3.9E-07 3.7E-07 5% increased CDF in Rev. 7.1 for reasons similar Reactor Building 471') to compartment R1K.

WiA (Radwaste Building 437') 1.2E-07 4,4E-07 3.2E-07 4.3% See discussion for compartment W07.

W13 (Radwaste 525' 2.0E-07 4.9E-07 2.9E-07 3.9% See discussion for compartment W07.

Emergency Chiller)

R1 L (Reactor Building 3.3E-09 2,4E-07 2.3E-07 3.2% See discussion for compartment W07.

572')

For one fire scenario modeled for W02, RHR is W02 (Cable Spreading 2.2E-07 4.4E-07 2.2E-07 2.9% modeled as completely failed due to fire Room) impacts. This is conservative. See the discussion for compartment W03.

T1GA (Turbine 1.6E-07 2.9E-07 1.3E-07 1.7% See discussion for compartment W07.

Generator West 441' T1Generatorbinwest 471') 4.9E-08 1.6E-07 1.1 E-07 1.4% See discussion for compartment W07.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS '

Page 5 of 20 Table A-1 (Fire): Comparison CDF Contributions for PSA Models Rev. 6.2 and Rev. 7.12 Fire Compartment 3 Rev 6.2 Fire Rev. 7.1 Fire Fire CDF Percenta e CDF (Irx-yr) CDF (Irx-yr) Difference Increase Discussion Total 7,4E-06 1.37E-05 6.31 E-06 85%

T1 H (Turbine 3.5E-09 1.1 E-07 1.OE-07 1.4% See discussion for compartment W07.

Generator Center 501') ______

This was a methodology change for Rev. 7.1.

A 0.5 recovery probability was applied in Rev.

6.2 to re-close RHR-V-27A if it spuriously opens R1B (Northeast 5.8E-08 1.6E-07 1.0E-07 1.4% due to fire. RG 1.200 requires that analysis be Reactor Building 471') performed to demonstrate that RHR-V-27A would not be damaged by the hot short by bypass of torque limit switch. The 0.5 credit was removed for Rev. 7.1.

T10 (West Transformer 1.9E-09 8.6E-08 8.4E-08 1.1% See discussion for compartment T1C.

Vault)

(TurbineGenerat Ti I (Turbine Generator 3.OE-09 8.4E-08 8.1 E-08 1.1% See discussion for compartment W07.

East 501')

TieG (Turbine 9.4E-09 8.7E-08 7.7E-08 1.0% See discussion for compartment W07.

Generator West 501') ______ ____________________

A human failure event for aligning SW as an W05 (Radwaste 467' 2.5E-07 3.2E-07 6.4E-08 0.9% alternate injection source was added to the Battery Room 1) _modeling in Rev. 7.1.

A model linking problem in Rev 6.2 was corrected produced and incorporated a small increase ininto theRev 7.1. This compartment risk importance.

S01 2.6E-09 4.6E-08 4.3E-08 0.6% See discussion for compartment W07.

RME 6.5E-10 4.1E-08 4.0E-08 0.5% See discussion for compartment R1K.

1 Computed for each compartment by dividing CDF Difference for each compartment by the total Rev. 6.2 Fire CDF.

2 This table compares CDF for all fire compartments whose Rev. 7.1 CDF increased by at least 1% from the Rev. 6.2 Fire compartment CDF.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 6 of 20 Table A-1 (Fire): Comparison CDF Contributions for PSA Models Rev. 6.2 and Rev. 7.12 Footnotes (cont'd):

3 The table below cross-references the fire compartment labels listed in Table A-1 (Fire) with those in Table E.3-7 of the ER.

Table A-1 (Fire) Table E.3-7 of the ER W07 RC-07 T1C TG-1C W04 RC-04 W08 RC-08 W03 RC-3 W14 RC-14 RiC R-1C WlA RC-IA W13 RC-13 R1L Not in table W02 RC-2 TiA TG-1A T1D TG-1D T1H Not in table RIB R-1B T10 Not in table T11 Not in table T1G Not in table W05 RC-5 R1K Not in table Sol Not in table RiE Not in table

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 7 of 20 Table A-3: Internal Events Level 2 Release Categories Release Frequency Category Description (per year) Percentage OK Containment Intact 1.88E-06 25.1%

H/E High/Early (LERF-BOC) 3.66E-07 4.9%

H/I High/Intermediate 2.35E-07 3.1%

M/E Moderate/Early 2.19E-07 2.9%

M/l Moderate/Intermediate 4.07E-06 54.5%

L/E Low/Early 2.30E-08 0.3%

L/I Low/Intermediate 3.86E-09 0.1%

LL/E Low Low/Early 1.64E-07 2.2%

LL/ Low Low/Intermediate 5.33E-07 7.1%

Total 7.50E-061 100%

'This sum of the release category frequencies differs slightly from the total Internal Events CDF reported in Table A-1 (Internal Events). The value in Table A-1 (Internal Events) is lower due to cutset minimalization that is performed during the PSA quantification.

Table A-4: Fire Level 2 Release Categories Release Frequency Category Description (per year) Percentage OK Containment Intact 3.53E-06 25.7%

H/E High/Early (LERF-BOC) 4.35E-081 0.3%

H/I High/Intermediate 7.93E-08 0.6%

M/E Moderate/Early 1.77E-08 0.1%

M/I Moderate/Intermediate 8.55E-06 62.3%

L/E Low/Early 2.33E-08 0.2%

L/I Low/Intermediate 8.49E-09 0.1%

LL/E Low Low/Early 8.61 E-07 6.3%

LL/I Low Low/Intermediate 6.13E-07 4.5%

Total 1.37E-05 100%

'The H/E release decreased from 2.46 E-07 in Rev. 6.2 (LEN) to 4.35 E-08 in Rev. 7.1 for the FPSA. The decreases for the Internal Events and Seismic hazards were of approximately the same amount but a lower percentage change primarily since the Fire Level 2 H/E frequency is dominated by Loss of RPV makeup scenarios. For the Rev 7.1 Level 2 PSA, the likelihood for Loss of RPV makeup scenarios leading to the H/E end state is much smaller than compared to the Rev 6.2 model. For example, the Rev. 7.1 Level 2 MAAP runs show that Loss of RPV makeup scenarios generally result in delayed containment failure (i.e., non-early release). For the Rev 7.1 Level 2 model, the dominant contributors to the H/E end state for Loss of RPV makeup scenarios involve failures such as Containment Isolation failure, Hydrogen Deflagration, or other phenomenological events which are low probability events.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 8 of 20 Table A-5: Seismic Level 2 Release Categories Release Frequency Percentage Category Description (per year)

OK Containment Intact 5.54E-07 11.4%

H/E High/Early (LERF-BOC) 1.87E-06 38.5%

H/I High/Intermediate 6.09E-07 12.5%

M/E Moderate/Early 4.46E-09 0.1%

M/I Moderate/Intermediate 1.12E-06 23.0%

L/E Low/Early 4.90E-09 0.1%

/I Low/Intermediate 7.17E-10 0.0%

LL/E Low Low/Early 1.29E-07 2.7%

LL/I Low Low/Intermediate 5.75E-07 11.8%

Total 4.86E-06 100%

Table A-6: Base Case Sensitivity Results for Internal Events Release Whole Body Dose Economic Impact Category (50 miles, person-rem/yr) (50 miles, $1yr)

OK 1.50E-03 6.66E-02 H/E 7.36E-01 1.05E+03 H/I 3.41 E-01 6.18E+02 M/E 2.06E-01 2.09E+02 M/I 4.03E+00 5.09E+03 L/E 3.13E-02 4.42E+01 VI 3.82E-03 4.83E+00 LL/E 1.87E-02 1.57E+00 LLI 1.24E-01 5.97E+01 TOTAL 5.49E+00 7.08E+03 Table A-7: Base Case Sensitivity Results for Fire Release Whole Body Dose Economic Impact Category (50 miles, person-rem/yr) (50 miles, $1yr)

OK 2.79E-03 1.24E-01 H/E 8.74E-02 1.25E+02 H/I 1.15E-01 2.09E+02 M/E 1.67E-02 1.69E+01 M/I 8.46E+00 1.07E+04

/E 3.17E-02 4.47E+01 VI 8.40E-03 1.06E+01 LVE 9.82E-02 8.26E+00 LVI 1.42E-01 6.87E+01 TOTAL 8.96E+00 1.12E+04

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 9 of 20 Table A-16: QUALITATIVE SCREENING OF SAMA CANDIDATES (ORIGINALLY SCREENED AS CRITERION E "VERY LOW BENEFIT")

SAMA ID Modification Revised Basis for Screening/

(Potential Enhancement) Criteria Modification Enhancements 1 AC/DC-05 Provide DC bus cross-ties D With the ability to provide alternate AC power to the chargers for the DC buses from DG-3 or DG-4, this SAMA candidate provides little risk reduction. The CDF and LERF RRW values associated with making the cross-ties between divisional DC power sources always available are 1.021 and 1.0002, respectively (affects all hazards, but primarily Fire), and the estimated uncertainty benefit based on RRW is approximately $180,000. This benefit represents two cross-ties: one between Division 1 and 2 and the other between Division 1 or 2 to Division 3.

Note: Division 3 is not of sufficient size to backfeed Division 1 or 2 loads. The implementation cost estimate is $1,590,000 and includes design, license amendment, materials, installation, testing and training. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D- Excessive Implementation Cost. This SAMA candidate is not considered for further evaluation.

AC/DC-06 Provide additional DC power to the E 120/240V AC is not risk significant at CGS. The CDF and LERF RRW values 120/240V vital AC system associated with making the buses perfect are 1.002 and 1.000, respectively (affects primarily Fire). The estimated uncertainty benefit based on RRW is less than $15,000, which is below the cost for a small design change at CGS.

Therefore, this SAMA candidate is determined to have a very low benefit and is not considered for further evaluation.

AC/DC-08 Increase training on a response to E 120/240V AC is not risk significant at CGS. The estimated uncertainty benefit a loss of two 120V AC buses that based on RRW associated with AC/DC-06 provides a very small benefit when cause inadvertent actuation signals making thel 20V AC sources perfect. Abnormal procedures currently exist at CGS for loss of 120V AC, which contain detailed information on lost indication and specific restoration actions. The operators receive periodic operator training on these procedures. Improving operator response associated with the loss of a 120V AC bus would not be likely to yield a SAMA candidate with real benefit.

Therefore, this SAMA candidate is determined to have a very low benefit and will not be considered for further evaluation.

See Reference F for Note 1

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachrhent 2 Page 10 of 20 Table A-16: QUALITATIVE SCREENING OF SAMA CANDIDATES (ORIGINALLY SCREENED AS CRITERION E "VERY LOW BENEFIT")

SAMA ID Modification Revised Basis for Screening/

(Potential Enhancement) Criteria Modification Enhancements 1 AC/DC-21 Use fire water system as a backup E The DG cooling water source is SW. This SAMA candidate only addresses loss source for diesel cooling of SW to the DG and not to other equipment (since this SAMA candidate is attempting to increase DG availability.) The CDF and LERF RRW values associated with doubling the DG cooling reliability are 1.005 and 1.000, respectively (affects primarily Fire). The estimated uncertainty benefit based on RRW is less than $70,000, which is below the cost for a small design change at CGS. Therefore, this SAMA candidate is not considered for further evaluation.

AC/DC-22 Add a new backup source of diesel E This SAMA candidate is similar in intent to AC/DC-21. The RRW associated with cooling doubling the DG cooling reliability calculated for AC/DC-21 also applies to this SAMA candidate, and the estimated uncertainty benefit is below the cost for a small design change at CGS. Therefore, this SAMA candidate is not considered for further evaluation.

AT-04 Increase boron concentration in the B Achange to the CGS Technical Specifications has been submitted to the NRC SLC system for increasing the SLC boron concentration (i.e., use of boron enriched inthe isotope B-1 0). This TS change achieves the intent of this SAMA candidate.

Therefore, the screening criterion for this SAMA candidate is changed to Criterion B - Already Implemented.

CB-02 Add redundant and diverse limit D Isolation at CGS is considered quite reliable. CGS CIVs that only provide a switches on each CIV containment isolation function (V-Sequence related) are air-operated. The CDF and LERF RRW values associated with eliminating containment isolation failures (except pre-existing and flooding) and reducing ISLOCA failures by one half are 1.002 and 1.018, respectively (primarily Internal Events LERF), and the estimated uncertainty benefit based on RRW is approximately $260,000. The implementation cost estimate is $1,759,000 and includes design, materials, installation, testing and training for 21 motor-operated valves (MOVs) in containment isolation groups 5, 6 and 7 and emergency core cooling system (ECCS) and reactor core isolation and cooling (RCIC) system MOVs that close on system auto-start. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D- Excessive Implementation Cost.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachmeht 2 Page 11 of 20 Table A-16: QUALITATIVE SCREENING OF SAMA CAIJDIDATES (ORIGINALLY SCREENED AS CRITERION E "VERY LOW BENEFIT")

SAMA ID Modification Revised Basis for Screening/

(Potential Enhancement) Criteria Modification Enhancements 1 CB-05 Install self-actuating CIVs D Containment isolation at CGS is considered very reliable. CGS CIVs that are normally open and have a containment isolation function are air-operated and are self-actuating. The estimated uncertainty benefit based on RRW that was calculated for SAMA candidate CB-02 ($260,000) also applies to this SAMA candidate. The implementation cost estimate is $6,179,000 and includes design, license amendment, materials, installation, testing and training for converting 21 MOVs to fail-safe air operators in containment isolation groups 5, 6, and 7 and ECCS and RCIC MOVs that close on system auto-start. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D- Excessive Implementation Cost. Therefore, this SAMA candidate is not considered for further evaluation.

CC-08 Modify ADS components to E The ADS at CGS is very reliable and not risk significant. The CDF and LERF improve reliability RRW values associated with doubling the ADS valves' reliability are calculated to both be 1.000, indicating no risk improvement, and the estimated uncertainty benefit is well below the cost for a small design change at CGS. Therefore, this SAMA candidate is not considered for further evaluation.

CC-09 Add signals to open SRVs E For an MSIV closure event, one or more SRVs may open briefly. Opening of automatically in an MSIV closure SRVs is very reliable and not a significant contributor to risk. The CDF and LERF transient RRW values associated with making the SRV pressure relief function perfect are 1.0041 and 1.000, respectively (affects Internal Events only), and the estimated uncertainty benefit based on RRW is less than $10,000, Which is well below the cost for a small design change at CGS. Therefore, this SAMA candidate is not considered for further evaluation.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 12 of 20 Table A-16: QUALITATIVE SCREENING OF SAMA CANDIDATES (ORIGINALLY SCREENED AS CRITERION E "VERY LOW BENEFIT")

SAMA ID Modification Revised Basis for Screening/

(Potential Enhancement) Criteria Modification Enhancements 1 CC-12 Add a diverse low pressure D CGS has significant redundancy of low pressure systems; thus these systems injection system have low to moderate risk significance. The CDF and LERF RRW values associated with reducing the unavailability of the low pressure ECCS injection function by 3 orders of magnitude are 1.046 and 1.007, respectively (affects Internal Events and Fire), and the estimated uncertainty benefit based on RRW is approximately $1,000,000. The implementation cost for this SAMA was evaluated by Vermont Yankee to be greater than $3,900,000. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D- Excessive Implementation Cost. This SAMA candidate is not considered for further evaluation.

CC-13 Increase flowrate of suppression D The increase in flowrate for CGS adds little benefit. Cooling is provided by RHR pool cooling Trains A and B. Once SPC is activated, additional cooling will not provide additional mitigating benefit. Significant time currently exists for this operator action. However, a potential benefit to ATWS sequences is to provide additional operator time to place SLC in service. The CDF and LERF RRW values associated with making the operator action perfect for initiating SLC during an MSIV closure ATWS are 1.001 and 1.007, respectively. The estimated uncertainty benefit based on RRW is approximately $110,000. Modification of both RHR Trains Aand B pump impellers, increasing the horsepower of the pump motors and redesigning the distribution system would be required to achieve this benefit. The estimated implementation cost for this SAMA candidate is $3,230,000. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D- Excessive Implementation Cost. Therefore, this SAMA candidate is not considered for further evaluation.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS '

Page 13 of 20 Table A-16: QUALITATIVE SCREENING OF SAMA CANDIDATES (ORIGINALLY SCREENED AS CRITERION E "VERY LOW BENEFIT")

SAMA I Modification Revised Basis for Screening/

(Potential Enhancement) Criteria Modification Enhancements 1 FR-01 Replace mercury switches in B The original diesel fire pump controllers were designed with mercury switches. The FP system diesel fire pump controllers have been evaluated and are approved as part of the CGS obsolescence program. One diesel fire pump controller remains to be replaced as part of this existing program. Therefore, the screening criterion for this SAMA candidate is changed to Criterion B - Already Implemented. This SAMA candidate is not considered for further evaluation.

FR-02 Upgrade fire compartment D The CGS IPEEE conclusions cited no weaknesses in compartment fire barriers that barriers contributed to any significant risk. A potential SAMA candidate associated with providing fire barriers for the two oil-filled transformers in each of the critical switchgear rooms was identified. The barriers would be required to be sufficiently rugged or a suppression system sufficiently fast acting to contain the potentially explosive transformer fire. Although a portion of the 480V distribution would be lost due to the transformer failure, the protected switchgear, the other 480V oil-filled transformer, and other components in the division would still receive power. Special HVAC cooling and ducting is also required to preserve the effectiveness of the fire barrier and to provide adequate transformer cooling. This SAMA candidate was modeled by setting the accident sequences involving ignition of oil-filled transformer fires in switchgear rooms to zero. The CDF and LERF RRW values for addition of four fire barriers to separate each of the oil filed transformers from the switchgear, inverter, and other electrical panels in both the Division 1 and Division 2 electrical switchgear rooms are 1.034 and 1.0003, respectively (affects Fire only). The estimated implementation cost for this SAMA candidate is $3,300,000. With the significant difference in estimated RRW uncertainty benefit and the implementation cost, the screening criterion for this SAMA candidate is changed to D - Excessive Implementation Cost. Therefore, this SAMA candidate is not considered for further evaluation.

FW-03 Install an independent diesel E CGS has the ability to connect the diesel driven fire water pump to the suction of a for the CST makeup pumps condensate booster pump for RPV makeup. The CDF RRW associated with making the uncertainty of one CST very low (see SAMA candidate CP-08) is 1.001 (affects Internal Events, no LERF contribution). The estimated uncertainty based on the RRW value of SAMA candidate CP-08 represents the uncertainty benefit expected of this SAMA candidate and is well below the cost for a small design change at CGS.

Therefore, this SAMA candidate is not considered for further evaluation.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 14 of 20 Table B-i: Summary of PSA Cases1 SAMA Risk Reduction CDF (1/yr) Total Candidate Description Model Approach CDF Internal Fire Seismic (llyr)

AC/DC-30R SAMA candidate AC/DC-1 0 This SAMA candidate adds an additional 7.46E-06 1.16E-05 4.75E-06 2.38E-05 "provide an additional diesel diesel generator that could be aligned to generator" address DG-1 either 4.16 KV bus SM-7 or SM-8. The unavailability. Since DG-2 is diesel generator would differ in design more important to fire risk, an from DG-1 and DG-2 to minimize the additional SAMA candidate to likelihood of diesel generator CCF events.

examine risk improvement for The PSA was modified to make DG-2 DG-2 will be considered. perfectly reliable to start and run (a different case, AC/DC-10, examined risk benefit from making DG-1 perfectly reliable). To accomplish this, gate G2AC544 was set to a low value.

Additionally, any loss of DG-1 and DG-2 was transferred to the SBO event trees, as this is the definition of SBO at CGS, and produces realistic modeling for this SAMA candidate.

CC-26R Install hard pipe from diesel The existing method of providing the fire 7.48E-06 1.37E-05 4.86E-06 2.60E-05 fire pump to vessel, water injection includes hookup of hoses from the FP system to the condensate system. By eliminating human errors in the model, the hard pipe system effectiveness can be simulated. Set to zero the human failure events for alignment of diesel fire pump to vessel. To accomplish this, set the following HEPs to zero:

FP-HUMN-SBOLH3LL FP-HUMNSYS62H3LL

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 15 of 20 Table B-2: Internal Events Benefit Results for Analysis Cases Case 45 Case 46 Case 47 Case 48 Case 49 Case 09 Case (AC/DC-30R) (CC-26R) (OT-10R) (FW-04) (CB-10R) (CB-08)

Off-site Annual Dose (rem) 5.48E+00 5.48E+00 5.50E+00 3.20E+00 5.39E+00 5.35E+00 Off-site Annual Property Loss ($) $7,068 $7,062 $7,087 $4,213 $6,947 $6,881 Comparison CDF 7.50E-06 7.50E-06 7.50E-06 7.50E-06 7.50E-06 7.50E-06 Comparison Dose (rem) 5.49E+00 5.49E+00 5.49E+00 5.49E+00 5.49E+00 5.49E+00 Comparison Cost ($) $7,079 $7,079 $7,079 $7,079 $7,079 $7,079 Enhanced CDF 7.46E-06 7.48E-06 7.51 E-06 4.50E-06 7.34E-06 7.39E-06 Reduction in CDF 0.53% 0.27% 0.13% 40.00% 2.13% 1.47%

Reduction in Off-site Dose 0.18% 0.18% 0.18% 41.71% 1.82% 2.55%

Immediate Dose Savings (On-site) $3 $2 $1 $258 $14 $9 Long Term Dose Savings (On-site) $15 $8 $4 $1,126 $60 $41 Total Accident Related Occupational Exposure (AOE) $18 $9 $5 $1,385 $74 $51 Cleanup/Decontamination Savings (On-site) $563 $282 $141 $42,233 $2,252 $1,549 Replacement Power Savings (On-site) $831 $415 $208 $62,293 $3,322 $2,284 Averted Costs of On-site Property Damage (AOSC) $1,394 $697 $348 $104,526 $5,575 $3,833 Total On-site Benefit $1,412 $706 $353 $105,911 $5,649 $3,883 Averted Public Exposure (APE) $261 $261 $261 $59,769 $2,610 $3,654 Averted Off-site Damage Savings (AOC) $144 $222 $104 $37,401 $1,723 $2,584 Total Off-site Benefit $405 $483 $365 $97,170 $4,333 $6,238 Total Benefit (On-site + Off-site) $1,817 $1,189 $718 $203,081 $9,981 $10,121

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachment 2 Page 16 of 20 Table B-3: Fire Benefit Results for Analysis Cases Case 45 Case 46 Case 47 Case 48 Case 49 Case 09 Case (AC/DC-30R) (CC-26R) (OT-10R) (FW-04) (CB-10R) (CB-08)

Off-site Annual Dose (rem) 7.92E+00 8.88E+00 8.96E+00 6.64E+00 8.96E+00 8.96E+00 Off-site Annual Property Loss ($) $9,857 $11,070 $11,170 $8,262 $11,168 $11,168 Comparison CDF 1.37E-05 1.37E-05 1.37E-05 1.37E-05 1.37E-05 1.37E-05 Comparison Dose (rem) 8.96E+00 8.96E+00 8.96E+00 8.96E+00 8.96E+00 8.96E+00 Comparison Cost ($) $11,168 $11,168 $11,168. $11,168 $11,168 $11,168 Enhanced CDF 1.16E-05 1.37E-05 1.37E-05 1.03E-05 1.37E-05 1.37E-05 Reduction in CDF 15.33% 0.00% 0.00% 24.82% 0.00% 0.00%

Reduction in Off-site Dose 11.61% 0.89% 0.00% 25.89% 0.00% 0.00%

Immediate Dose Savings (On-site) $181 $0 $0 $293 $0 $0 Long Term Dose Savings (On-site) $788 $0 $0 $1,276 $0 $0 Total Accident Related Occupational Exposure (AOE) $969 $0 $0 $1,569 $0 $0 Cleanup/Decontamination Savings (On-site) $29,563 $0 $0 $47,864 $0 $0 Replacement Power Savings (On-site) $43,605 $0 $0 $70,599 $0 $0 Averted Costs of On-site Property Damage (AOSC) $73,168 $0 $0 $118,463 $0 $0 Total On-site Benefit $74,137 $0 $0 $120,032 $0 $0 Averted Public Exposure (APE) $27,144 $2,088 $0 $60,552 $0 $0 Averted Off-site Damage Savings (AOC) $17,109 $1,279 $26 $37,923 $0 $0 Total Off-site Benefit $44,253 $3,367 $26 $98,475 $0 $0 Total Benefit (On-site + Off-site) $118,390 $3,367 $26 $218,507 $0 $0

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 17 of 20 Table B-4: Seismic Benefit Results for Analysis Cases Case 45 Case 46 Case 47 Case 48 Case 49 Case 09 Case (AC/DC-30R) (CC-26R) (OT-10R) (FW-04) (CB-10R) (CB-08)

Off-site Annual Dose (rem) 5.77E+00 5.91 E+00 5.91 E+00 5.91 E+00 5.91 E+00 5.91 E+00 Off-site Annual Property Loss (S) $8,241 $8,444 $8,444 $8,444 $8,444 $8,444 Comparison CDF 4.86E-06 4.86E-06 4.86E-06 4.86E-06 4.86E-06 4.86E-06 Comparison Dose (rem) 5.91 E+00 5.91 E+00 5.91 E+00 5.91 E+00 5.91 E+00 5.91 E+00 Comparison Cost ($) $8,444 $8,444 $8,444 $8,444 $8,444 $8,444 Enhanced CDF 4.75E-06 4.86E-06 4.86E-06 4.86E-06 4.86E-06 4.86E-06 Reduction in CDF 2.26% 0.00% 0.00% 0.00% 0.00% 0.00%

Reduction in Off-site Dose 2.37% 0.00% 0.00% 0.00% 0.00% 0.00%

Immediate Dose Savings (On-site) $9 $0 $0 $0 $0 $0 Long Term Dose Savings (On-site) $41 $0 $0 $0 $0 $0 Total Accident Related Occupational Exposure (AOE) $51 $0 $0 $0 $0 $0 Cleanup/Decontamination Savings (On-site) $1,549 $0 $0 $0 $0 $0 Replacement Power Savings (On-site) $2,284 $0 $0 $0 $0 $0 Averted Costs of On-site Property Damage (AOSC) $3,833 $0 $0 $0 $0 $0 Total On-site Benefit $3,883 $0 $0 $0 $0 $0 Averted Public Exposure (APE) $3,654 $0 $0 $0 $0 $0 Averted Off-site Damage Savings (AOC) $2,649 $0 $0 $0 $0 $0 Total Off-site Benefit $6,303 $0 $0 $0 $0 $0 Total Benefit (On-site + Off-site) $10,187 $0 $0 $0 $0 $0

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Attachmient 2 Page 18 of 20 Table B-5: Total Benefit Results for Analysis Cases Case 37 Case 38 Case 39 Case 40 Case 41 Case 42 Case 43 Case 44 (FR-09R) (FR-08) (AT-15R) (OT-09R) (FR-12R) (FR-11R) (FR-10R) (FL-07R)

Internal Events $0 $0 $39,864 $21,473 $0 $0 $0 $5,403 Fire $101,294 $512,974 $0 $87,797 $105,130 $508,730 $13,742 $0 Seismic $0 $0 $0 $0 $0 $0 $0 $0 Other $0 $0 $39,864 $21,473 $0 $0 $0 $5,403 Total Benefit $101,294 $512,974 $79,728 $130,744 $105,130 $508,730 $13,742 $10,805 Case 45 Case 46 Case 47 Case 48 Case 49 Case 09 Case 09 (AC/DC-30R) (CC-26R) (OT-1OR) (FW-04) (CB-1OR) (CB-08) (CB-09)

Internal Events $1,817 $1,189 $718 $203,081 $9,981 $10,121 $10,121 Fire $118,390 $3,367 $26 $218,507 $0 $0 $0 Seismic $10,187 $0 $0 $0 $0 $0 $0 Other $1,817 $1,189 $718 $203,081 $9,981 $10,121 $10,121 Total Benefit $132,210 $5,745 $1,463 $624,669 $19,962 $20,243 $20,243

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 19 of 20 Table B-7: Final Results of the Cost-Benefit Evaluation SAMD ID Modification Analysis Estimated Cost of Conclusion Case Benefit Implementation Improve procedures and operator training to identify systems OT-07R and operator actions determined to be important from the Case 35 $197,597 $40,000 Cost Effective PSA.

FW-05R Examine the potential for operators to control RFW and Case 36 $66,860 $29,000 Cost Effective avoid a reactor trip.

FR-09R Install early fire detection in the following Reactor Building Case 37 $101,294 $680,000 Not Cost Effective analysis units: R-1 B, R-1 D, and R-1J.

AT-15R Install more likely for Case 39 $79,728 $2,825,000 Not Cost Effective ATWS.modifications to make use of HPCS OT-09R For the non-LOCA initiating events, credit the Z (PCS Case 40 $130,744 $130,000 Cost Effective recovery) function.

FR-12R Install early fire detection in the following physical analysis Case 41 $105,130 $725,000 Not Cost Effective units: T-1A, T-12, T-1C, and T-1D.

Install early fire detection in the following analysis units: RC-FR-11 R 02, RC-03, RC-04, RC-05, RC-07, RC-08, RC-1 1, RC-1 3, Case 42 $508,730 $1,035,000 Not Cost Effective RC-14, and RC-1A.

FR-1 OR Install early fire detection in the Main Control Room: RC-10. Case 43 $13,742 $535,000 Not Cost Effective FL-07R Protect the HPCS from flooding resulting from ISLOCA Case 44 $10,805 $1,050,000 Not Cost Effective events.

AC/DC-30R Provide an additional DG diverse from DG-1 and DG-2. Case 45 $132,210 $10,000,000 Not Cost Effective CC-26R Install hard pipe from diesel fire pump to vessel. Case 46 $5,745 $710,000 Not Cost Effective Increase fire pump house building integrity to withstand OT-1 OR higher winds so the fire system will be capable of Case 47 $1,463 $735,000 Not Cost Effective withstanding a severe weather event.

FW-04 Add a motor-driven feedwater pump. Case 48 $624,669 $10,000,000 Not Cost Effective CB-10R Provide additional NDE and inspections of MS pipe in Case 49 $19,962 $125,000 Not Cost Effective Turbine Building.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Page 20 of 20 Table B-8: Final Results of the Sensitivity Cases SAMA ID Sensitivity Sensitivity Estimated Conclusion Case #11 Case #2 Cost (2008/2010)

FL-04R $390,642 $615,345 $377,000 Cost Effective-Sensitivity Cases 1 & 2 FL-06R $197,662 $311,465 $13,500 Cost Effective CC-24R $244,548 $421,991 $105,000 Cost Effective CC-25R $16,457 $28,919 $13,000 Cost Effective - Sensitivity Cases 1 & 2 OT-07R $264,720 $479,509 $40,000 Cost Effective FW-05R $99,445 $181,382 $29,000 Cost Effective FR-09R $138,485 $263,365 $680,000 Not Cost Effective AT-15R $101,544 $191,348 $2,825,000 Not Cost Effective OT-09R $193,609 $331,346 $130,000 Cost Effective FR-12R $150,512 $273,337 $725,000 Not Cost Effective FR-11R $736,493 $1,322,699 $1,035,000 Cost Effective - Sensitivity Case 2 FR-10R $19,989 $35,730 $535,000 Not Cost Effective FL-07R $17,942 $25,933 $1,050,000 Not Cost Effective AC/DC-30R $187,130 $347,093 $10,000,000 Not Cost Effective CC-26R $8,973 $14,461 $710,000 Not Cost Effective OT-1OR $2,146 $3,516 $735,000 Not Cost Effective FW-04 $904,245 $1,542,907 $10,000,000 Not Cost Effective CB-1OR $28,619 $47,910 $125,000 Not Cost Effective 1 The replacement power component for Sensitivity Case 1 (3% Discount Rate) is calculated using the replacement power net present value for a 1% and 5% discount rate and interpolating for the 3%

discount rate.

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE REVIEW OF THE SEVERE ACCIDENT MITIGATION ALTERNATIVE ANALYSIS Enclosure 1 Amendment 34 to the LRA

Columbia Generating Station License Renewal Application Environmental Report Table E.10-1 Qualitative Screening of SAMA Candidates (continued)

SAMA ID Modification Screening Criterion Basis for Screening/ Source (Potential Enhancement) Modification Enhancements Revise procedure to allow use Criterion A CGS does not have a suppression pool jockey CC-18 of suppression pool jockey pump. Therefore, the intent of the SAMA is not [38, Section 6]

pump for injection. Not Applicable applicable to CGS.

Re-opening of MSIV's in non-LOCA events is CC-19 Revise procedure to re-open Criterion B addressed per procedures. Therefore, the [90], [98]

MSIVs. Already Implemented at CGS intent of the SAMA has already been implemented at CGS.

Considered for final cost-benefit evaluation.

Enhancements have already been made to the strainers. The existing strainers are as large as possible based on downcomer clearing loads and in the suppression pool. Therefore, improvements to the strainers will not be Improve ECCS suction Criterion C considered.

CC-20 strainers or replace insulation C onsidered.

in containment. Replacing the existing insulation within the containment could reduce the likelihood of strainer clogging. This will be considered for a final cost-benefit evaluation.

Model Change - ECCS suction strainer plugging was set to zero.

Cenonzderd for final coct benefit evaluation,.

Revise procedure to align followi... ng AA of..u ppr...

... pool ,o liGU9, Criterion Gv;^ ........

I-G- . .R ..........

CC-21 LPCI or core spray to CST on loss of suppression pool cooling. Considered for F'-rthcr E-al'ation ____________________

coig[Already Implemented at CGS] Mdcl ChaRngc Mdel S.uprccPion p*el

____________________ ______________________ coling to be pcrfectly rziiable.  : lII Providing alternate sources of injection through multiple/diverse pathways is addressed per procedures. Therefore, the intent of the SAMA has already been implemented at CGS.

Attachment E Page E-171 claairy 2919 JAmendiment 34