Text

Application for Renewed Operating License, Appendix F Severe Accident Mitigation Alternatives
	ML022280294
Person / Time
Site:	Summer
Issue date:	08/06/2002
From:	Byrne S; South Carolina Electric & Gas Co
To:	Rajender Auluck; Document Control Desk, Office of Nuclear Reactor Regulation
References
	RC-02-0123
	Download: ML022280294 (129)
	v • d • e

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT APPENDIX F SEVERE ACCIDENT MITIGATION ALTERNATIVES F-i

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE OF CONTENTS Section Pge ACRONYMS USED IN APPENDIX F ................................................................................................... F-iv F.0 Appendix F: Severe Accident Mitigation Alternatives (SAMA) ........................... F-1 F.1 M ethodology ................................................................................................................ F-i F.1.1. VCSNS-Specific SAMA .............................................................................................. F-2 F.1.2. VCSNS-PRA History .................................................................................................. F-4 F.2 Level 3 PRA Analysis ........................................................................................... F-10 F.2.1 Analysis ..................................................................................................................... F-10 F.2.2 Population .................................................................................................................. F-1o0 F.3 Cost-Benefit Analysis ................................................................................................ F-18 F.3.1 Offsite Exposure Cost ................................................................................................ F-18 F.3.2 Offsite Economic Cost-Risk ...................................................................................... F-18 F.3.3 Onsite Exposure Cost-Risk ........................................................................................ F-18 F.3.4 Onsite Cleanup and Decontamination Cost ............................................................... F-21 F.3.5 Replacement Power Cost ........................................................................................... F-21 F.3.6 Baseline Screening ..................................................................................................... F-22 F.4 Phase 1 SAMA Analysis: SAMA Candidates and Screening Process ..................... F-23 F.5 Phase 2 SAMA Analysis ............................................................................................ F-96 F.5.1 Phase 2 SAMA Number 2: Add Redundant DC Control Power for PSW Pumps C and D (A, B, and C Pumps for VCSNS) .................................................... F-96 F.5.2 Phase 2 SAMA Number 3: Use Existing Hydro-Test Pump for RCP Seal Injection ..................................................................................................................... F-99 F.5.3 Phase 2 SAMA Number 9: Refill CST (RWST for VCSNS) ............................ F-100 F.5.4 Phase 2 SAMA Number 10: Improve 7.2-kV Bus Cross-Tie Ability .................... F-103 F.5.5 Phase 2 SAMA Number 11: Install Relief Valves in the CC System and Number 12: Ensure all ISLOCA Releases are Scrubbed ................................... F-105 F.5.6 Phase 2 SAMA Number 13: Improved MSIV Design ....................................... F-106 F.5.7 Phase 2 SAMA Number 20: Replace Current PORVs with Larger Ones So That Only One is Required for Successful Feed and Bleed ..................................... F-107 F.5.8 Phase 2 SAMA Number 24: Create Automatic Swap-Over to Recirculation on RWST Depletion ...................................................................................................... F-108 F.5.9 Phase 2 SAMA Number 25: Improved Low Pressure System (Firepump) ...... F-110 F.5.10 Phase 2 SAMA Number 26: Replace Old Air Compressors with More R eliable O nes ........................................................................................................... F-1 12 F.5.11 Phase 2 SAMA Number 27: Install MG Set Trip Breakers in Control Room ........ F-113 F.6 Phase 2 SAMA Analysis Summary .................................................................... F-115 F.7 Sensitivities .............................................................................................................. F- 16 F.7.1 Large Early Release Frequency ............................................................................... F-116 F.7.2 Real Discount Rate and Other Parameters ......................................................... F-117 F.8 Conclusions .............................................................................................................. F-120 F.9 References ................................................................................................................ F-121 F-ii

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE OF CONTENTS (Continued)

List of Tables Table Page Table F. 1-1 Summary and Status of VCSNS Improvements .................................................................... F-6 Table F. 1-2 PRA Model Changes - IPE Submittal through 3Y Update 1/2000 ........................................ F-9 Table F.2-1 Estimated population distribution within a 10-mile radius of VCSNS, year 2042 ...... F-11 Table F.2-2 Estimated population distribution within a 50-mile radius of VCSNS, year 2042 .......... F-11 Table F.2-3 Estimated annual population growth rate within a 10-mile radius of VCSNS ................... F- 12 Table F.2-4. Estimated annual population growth rate within a 10 to 50-mile radius of VCSNS ......... F-13 Table F.2-5 Estimated VCSNS core inventory ................................................................................. F-15 Table F.2-6 MACCS2 release categories vs. VCSNS release categories ............................................... F-16 Table F.2-7 Results of VCSNS Level 3 PRA analysis ............................................................................ F-17 T able F.4-1 Phase 1 SA M A .................................................................................................................... F-24 T able F.4-2 Phase 2 SA M A .................................................................................................................... F-78 Table F.5. 1-1 Phase 2 SAMA Number 2 Model Changes ...................................................................... F-97 Table F.5.1-2 Phase 2 SAMA Number 2 Net Value ............................................................................... F-99 Table F.5.2-1 Phase 2 SAMA Number 3 Model Changes ............................................................... F-100 Table F.5.2-2 Phase 2 SAMA Number 3 Net Value ......................................................................... F-100 Table F.5.3-1 Phase 2 SAMA Number 9 Model Changes .................................................................... F-101 Table F.5.3-2 Phase 2 SAMA Number 9 Net Value ............................................................................. F-103 Table F.5.4-1 Phase 2 SAMA Number 10 Model Changes .................................................................. F-104 Table F.5.4-2 Phase 2 SAMA Number 10 Net Value ...................................................................... F-105 Table F.5.5-1 Phase 2 SAMA Numbers 11 and 12 Model Changes ................................................. F-105 Table F.5.5-2 Phase 2 SAMA Numbers 11 and 12 Net Value .............................................................. F-106 Table F.5.6-1 Phase 2 SAMA Number 13 Model Changes .................................................................. F-106 Table F.5.6-2 Phase 2 SAMA Number 13 Net Value ........................................................................... F- 107 Table F.5.7-1 Phase 2 SAMA Number 21 Model Changes .................................................................. F-108 Table F.5.7-2 Phase 2 SAMA Number 20 Net Value ........................................................................... F-108 Table F.5.8-1 Phase 2 SAMA Numbers 24 and 24a Model Changes ................................................... F-109 Table F.5.8-2 Phase 2 SAMA Number 24 Net Value ...................................................................... F-110 Table F.5.8-3 Phase 2 SAMA Number 24a Net Value ......................................................................... F-1 10 Table F.5.9-1 Phase 2 SAMA Number 24 Model Changes ............................................................. F-111 Table F.5.9-2 Phase 2 SAMA Number 25 Net Value ........................................................................... F-1 12 Table F.5.10-1 Phase 2 SAMA Number 26 Model Changes ................................................................ F-112 Table F.5.10-2 Phase 2 SAMA Number 26 Net Value .................................................................... F-113 Table F.5.1 1-1 Phase 2 SAMA Number 27 Net Value ......................................................................... F-1 14 Table F.6-1 Summary of the Detailed SAMA Analyses .................................................................. F- 115 Table F.7.2-1 Summary Of Real Discount Rate Impact .................................................................. F-118 F-iii

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT ACRONYMS USED IN APPENDIX F AMSAC ATWS Mitigating System Actuation Circuitry AOP Abnormal Operating Procedure ATWS Anticipated Transient Without Scram BWR Boiling Water Reactor CC Component Cooling CCW Component Cooling Water CDF Core Damage Frequency CHR Containment Heat Removal EDG Emergency Diesel Generator EOP Emergency Operating Procedure EPZ Emergency Planning Zone GIS Geographic Information System HEP Human Error Probability IPE Individual Plant Examination IPEEE Individual Plant Examination - External Events ISLOCA Interfacing System LOCA kV Kilovolt LERF Large Early Release Frequency LOCA Loss of Coolant Accident rn/sec Meters per second MACCS2 MELCOR Accident Consequences Code System, Version 2 MG Motor Generator MSIV Main Steam Isolation Valve MWe Megawatts-electrical MWth Megawatts-thermal NPSH Net Positive Suction Head NRC U.S. Nuclear Regulatory Commission OECR Off-site economic cost risk PORV Power-operated relief valve PRA Probabilistic Risk Analysis PSA Probabilistic Safety Assessment PWR Pressurized Water Reactor RAI Request for Additional Information RCP Reactor Coolant Pump RDR Real Discount Rate RHR Residual Heat Removal RPV Reactor Pressure Vessel RWST Refueling Water Storage Tank F-iv

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT ACRONYMS USED IN APPENDIX F SAMA Severe Accident Mitigation Alternative SGTR Steam Generator Tube Rupture VCSNS V.C. Summer Nuclear Station F-v

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.0 APPENDIX F: SEVERE ACCIDENT MITIGATION ALTERNATIVES (SAMA)

F.1 Methodology The methodology selected for this analysis involves identifying those Severe Accident Mitigation Alternative (SAMA) candidates that have the highest potential for reducing core damage frequency (CDF) and both radiological and economic risk to determine whether or not the implementation of those candidates is beneficial on a cost-risk reduction basis. This process consists of the following steps:

"* Identify potential SAMA candidates based on V.C. Summer Nuclear Station (VCSNS), NRC, and industry documents,

"* Screen out Phase 1 SAMA candidates that are not applicable to the VCSNS design or are of low benefit in Pressurized Water Reactors (PWRs),

"* Determine the maximum averted cost-risk that is possible based on the VCSNS probabilistic safety assessment (PSA) Level 3 results,

"* Screen out Phase 1 SAMA candidates whose estimated cost exceeds the maximum possible averted cost-risk, and

" Perform a more detailed analysis (Phase 2) to determine if the remaining SAMA candidates are desirable modifications or changes. This is based on a comparison of the averted cost risk associated with implementing the SAMA at the site and the cost required to perform the modification. If the averted cost-risk is greater than the cost of implementation, then the SAMA candidate is considered to be a beneficial modification. PSA insights are also used to screen SAMA candidates in this phase.

The steps outlined above are described in more detail in the subsections of this appendix.

Figure F.1-1 provides a graphical representation of the SAMA process.

F-1

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Is

implementation Does the Nos ScendScreened o nownto*b cost Screened No Screened Implementation0 AAafc e 3plicble Ye Retain for*

Screene potential implementation Nos riskr Screene Phs Anaysis e

Figure F.1-1. SAMA Screening Process F.1.1. VCSNS-Specific SAMA The initial list of SAMA candidates for VCSNS was developed from lists of SAMAs at other nuclear power plants (including References 4, 6, 8, 11, 12, and 31), NRC documents (References 1, 2, 3, 5, 7, 13, 14, and 15), and documents related to advanced power reactor designs (ABWR SAMAs) (including References 9 and 10). In addition, plant-specific analyses (including References 16 and 17) have been used to identify potential SAMAs that address VCSNS vulnerabilities. Eleven SAMA candidates were taken from these plant-specific references and are included in this document. Four of the SAMAs identified in the VCSNS sources were considered to be unique while the other seven were already identified by industry reference sources. This process is considered to adequately address the requirement of identifying significant safety improvements that could be performed at VCSNS. The initial SAMA list, Table F.4-1, includes a column that documents the reference sources for each SAMA.

All of the SAMAs identified originally in the VCSNS Individual Plant Examination (IPE)

(Reference 16) have been implemented at the plant. Two SAMAs already identified by industry sources were independently identified in plant initiated programs. These SAMAs were included in and screened in this cost-benefit analysis.

F-2

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT The VCSNS Individual Plant Examination - External Events (IPEEE) and IPEEE Request for Additional Information (RAI) (References 17 and 32, respectively) identified minor opportunities for plant improvements. As a result of the Seismic Analysis, electrical cabinets were bolted together to increase their ruggedness (subsumed by a generic SAMA directed at this type of upgrade). The Fire Analysis in the IPEEE identified the potential for changing plant response procedures, but these changes were judged to have a negligible impact on the results of the Fire Analysis and are not specifically included in this document.

Given the existing assessments of external events and internal fires at VCSNS, the cost benefit analysis uses the internal events PSA as the basis for measuring the impact of SAMA implementation. No fire or external events models are used in this analysis because the Fire and IPEEE programs are considered to have already addressed potential plant improvements related to those categories.

For the purposes of this SAMA evaluation, the current VCSNS Probabilistic Risk Analysis (PRA) model (model UP3a) is used for the required quantitative assessments.

The baseline CDF is 5.59E-5/yr (28,435 cutsets) and the baseline Large Early Release Frequency (LERF) is 6.99E-7/yr (45,837 cutsets). Cost-risk calculations are based on this model and the modifications made to it to represent implementation of the proposed SAMAs.

F-3

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.1.2. VCSNS-PRA History Since the original development of the VCSNS PRA model, several updates have been performed to reflect the changes that have been made to the plant. Modeling techniques have also improved and the PRA has been enhanced to implement some of these techniques. This section summarizes the model changes that have been made since the original EPE submittal.

Section 6.1 of the IPE Submittal (Reference 16) lists the improvements to the plant that were a result of the IPE Program. These improvements address potential vulnerabilities or deficiencies, either directly or indirectly, that improved operator response to accidents or improved system or component performance. In addition to these improvements, the Submittal also discusses the use of the new 0-rings in the reactor coolant pumps and also the use of the fire service system for emergency RCP thermal barrier cooling.

Table F.1-I provides a summary of the plant improvements discussed in the submittal and also the improvement to eliminate the dependency of the component cooling water pumps and charging pumps on the chilled water system for cooling. For each improvement, the following information is provided:

"* description of the improvement

"* date the improvement was implemented in the plant or status of evaluation

"* whether or not the improvement was credited in the IPE

"* the impact of the improvement on the core damage frequency (based on the original IPE model)

"* the basis for the improvement As noted on this table, a majority of the improvements have been credited in the IPE.

One improvement was evaluated in a sensitivity study and provided in the IPE Submittal Report (plant improvement number 1 from Table F.1-1), and one was evaluated in a study after the IPE results were submitted to the NRC (plant improvement number 11 from Table F.1-1). It is difficult to quantify the benefits of several of the improvements due to the qualitative nature of the changes. The benefits of several of the improvements are qualitatively assessed to be relatively small (plant improvement numbers 2 and 7 from Table F. 1-1).

Plant improvement number 11 from Table F.1-1 provides some information on the elimination of the chilled water dependency of the component cooling water (CCW) pumps and charging pumps. This plant modification involved changing the charging F-4

K------------L-VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT pump cooling to the CCW system and using CCW flow to also cool the CCW pump motors. This change was evaluated using the VCSNS IPE through detailed modeling changes. It can be seen that the impact of implementing this change had a significant impact on the plant risk profile. The core damage frequency was reduced to 1.22E-04/yr from the IPE submittal value of 2.04E-04/yr.

Table F. 1-2 provides a list of model update tasks which summarize the model changes from the IPE submittal through the present. The CDF and LERF are provided for each model revision, as appropriate.

F-5

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.I-1

SUMMARY

AND STATUS OF VCSNS IMPROVEMENTS Credited in Date Current Plant Implemented Credited In Impact on PRA Basis For Improvement Improvement Description In Plant IPE CDF (1) (UP3a) Improvement

1. Alternate Developed Abnormal Operating Procedure "Total 7/93 IPE credit 2.04E-04 (2) Yes IPE Charging Pump Loss of Chilled Water." Use AOP following loss of only for 1.54E-04 Vulnerability Cooling both trains of chilled water. Alternate cooling for LOSP event.

charging pumps is established, using the preferred Sensitivity Demineralized Water System or the Fire Service credit for all System, so RCP seal injection can be maintained, events.

2. Chilled A "chiller rotation" policy to reduce the time a chiller 1/93 No NA N/A IPE Water System will be down has been implemented. Data has Chilled Vulnerability Reliability indicated a correlation between chiller downtime and water failure to start probability, removed from model

3. Diesel The Fire Service System is a backup to the Service 9/92 No credit in NA, but will No IPE System Generator Water System for DG cooling, but the Fire Service IPE for reduce SBO Analysis Temperature System is not sized to maintain the DG at rated load. alternate frequency due Monitoring Steps were added to an Emergency Operating cooling of to failure of Procedure to monitor DG temperature and reduce DG service water load if temperatures increase.

4. Energizing Revised EOP "Response to Loss of Secondary Heat 8/92 Yes NA, included Yes IPE System Pressurizer Sink" to direct operators to re-energize any PZR in IPE Analysis PORV Block PORV block valves that were closed and racked out. Submittal Valves The steps were moved up in the procedure to allow report operators more time to prepare for feed and bleed results(3) before complete loss of heat sink.

5. Use of Main Use the turbine-driven Feedwater System pumps to 1/01 No NA, but will No. IPE System Feedwater supply feedwater to the SGs if the Emergency reduce the However, Analysis Pumps for a Feedwater System fails. Currently, EOPs call for CDF due to EOPs direct Loss of Heat using feedwater booster pumps which require SG transients that this action.

Sink Event depressurization to less than 350 psig (the HRA do not lead to showed the operator could not complete the required consequential steps in the available time). LOCAs Page F-6

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.1-1

SUMMARY

AND STATUS OF VCSNS IMPROVEMENTS (Cont'd)

Credited in Date Current Plant Implemented Credited In Impact on PRA Basis For Improvement Improvement Description In Plant IPE CDF (1) (UP3a) Improvement

6. Bypasses The computerized BISI System, which provides a 6/91 No NA, but will Considered IPE Related and Inoperable graphic control room indication of critical system improve in HRA Improvement Status operability, was reviewed and updated based on operator Indication insights gained during the IPE system analyses. awareness of (BISI) system problems

7. Reactor Operators are required to re-establish instrument air 12/93 No NA. but will Yes IPE System Building to the pressurizer PORVs to ensure sufficient air improve feed Analysis Instrument Air supply is available for multiple openings of the and bleed Supply PORVs during feed and bleed. Locally opening of availability the valve dominating failure to re-establish instrument air was included as an improvement.

8. Training and The IPE results have been used to identify drill 2/93 No NA, but there Considered IPE Related Emergency scenarios that can be used in training and emergency would be some in IIRA Improvement Planning Input planning. benefit to HEPs lowering CDF

9. New RCP Use of new RCP seal O-ring to provide better RCP A - Refuel No NA, but will No IPE Seal O-rings performance under loss of thermal barrier cooling 11 (Spring '99) improve Vulnerability and seal injection conditions RCP B - Refuel ability of the 12 (Fall -00) plant to with RCP C - Refuel stand SBO 10 (Fall '97)

10. Fire Water Alternate and diverse cooling source for RCP thermal Not Planned No NA, but will No IPE Risk Connection for barrier cooling to address SBO plant vulnerability reduce CDF Informed RCP Thermal due to SBO Improvement Barrier Cooling events P 7 C

(

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.1-1

SUMMARY

AND STATUS OF VCSNS IMPROVEMENTS (Cont'd)

Credited in Date Current Plant Implemented Credited In Impact on PRA Basis For Improvement Improvement Description In Plant IPE CDF (1) (UP3a) Improvement

11. Elimination Change the cooling dependency of the CCW pumps 11/94 No 1.22E-04 Yes IPE Risk of CCW and and charging pumps from the chilled water system to Informed Charging/SI the CCW system Improvement Pump Chilled Water Dependency

12. Installation Key switches have been provided, with the keys kept 11/94 No NA, but will No IPE Risk of key switches in the control room, to bypass FW isolation signals reduce CDF Informed to allow use of during a loss of heat sink accident. (4) due to loss of Improvement condensate heat sink feed during a events loss of EFW.

Notes:

1- This column provides the core damage frequency with the improvement implemented based on the original IPE model.

2- The results presented in the IPE Submittal report credit the "Loss of Chilled Water" AOP during loss of offsite power event only.

3- The IPE does include the action to re-energize and open a closed pressurizer PORV block valve if closed, in order to initiate feed and bleed cooling. However, based on PSA input, the operator action to re-energize any closed & de-energized block valve has been moved to the front of the Loss of Heat Sink EOP. This will increase the allowed operator action time beyond the original 30 minute assumption, and increase the likelihood of success.

4- The switches eliminate the need to install jumpers and remove a fuse in order to re-open the FW isolation valves after an SI has occurred. The original HRA analysis of the time available to establish condensate feed and the required actions to enable condensate feed (i.e., jumpers & fuses) led to the conclusion that the required actions could not be completed in time. Therefore, the REP for OAF (Establish Condensate Feed) was set to a value of 1.0 (i.e., assumed to fail). The use of the new switches may be included in a future PRA model update. No impact on CDF is available at this time.

Page F-8

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.1-2 PRA MODEL CHANGES - IPE SUBMITTAL THROUGH 3RD UPDATE 1/2000 MODEL REVISION CDF LERF CALC NUMBER IPE Model 2.OE-4 N/A IPE SUBMITTAL Data Update 1.8E-4 N/A DCOO300-033 VU / CCW MOD 1.2E-4 N/A DCOO300-034 EFW CK VLV MOD, Expand IA Modeling, and Other Modeling 9.6E-5 N/A DCOO300-035 &

Changes DCOO300-037 Conversion to Singletop Model and Removed Excess Conservatism to 8.4E-5 N/A DCOO300-131 Singletop Model Created Stand Alone LERF Model N/A 1.7E-6 DCOO300-132 Updated Common Cause Failure Probability 8.6E-5 1.1 E-6 DCOO300-133 Demodulized Special Initiators 8.6E-5 1.1 E-6 DCOO300-136 Human Reliability Analysis Update 1.3E-4 2.2E-6 DCOO300-134 Second Data Update (Changes Primarily Due To LOCA Freq Changes, 5.8E-5 8.9E- 7 DCOO300-135 NUREG 5750 And LOSP)

Third Data Update, Common Cause Update And Model Corrections 5.6E-5 7.OE-7 DCOO300-137 K. C

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.2 Level 3 PRA Analysis F.2.1 Analysis The MACCS2 code (Reference 34) was used to perform the level 3 PRA for VCSNS.

The input parameters given with the MACCS2 "Sample Problem A," which included the NUREG- 1150 food model (Reference 35), formed the basis for the present analysis.

These generic values were supplemented with parameters specific to VCSNS and its surrounding area. Site-specific data included population distribution, economic parameters, and agricultural production. Plant-specific release data included the time nuclide distribution of releases, release frequencies, and release locations. The behavior of the population during a release (evacuation parameters) was based on plant- and site specific set points (i.e., declaration of a General Emergency) and the emergency planning zone (EPZ) evacuation table (Reference 36). These data were used in combination with site-specific meteorology to simulate the probability distribution of impact risks (exposure and economic) to the surrounding population (within 50 miles) from the large early release accident sequences at VCSNS.

F.2.2 Population The population surrounding VCSNS was estimated for the year 2042. The distribution was given in terms of population at distances to 1, 2, 3, 4, 5, 10, 20, 30, 40 and 50 miles from the plant and in the direction of each of the 16 compass points (i.e., N, NNE, NE, NNW). The total population for the 160 sectors (10 distances x 16 directions) in the region was estimated as 2,078,740, the distribution of which is given in Tables F.2-1 and F.2-2.

Population projections within 50 miles of VCSNS were determined using a geographic information system (GIS), U.S. Nuclear Regulatory Commission (NRC) sector population data for 1990, and population growth rates based on 1990 and 2000 county level U.S. Census Bureau data. Population sectors were created for 16 sectors at an interval of 1 mile from 0 to 5 miles, the interval from 5 to 10 miles and at 10-mile intervals from 10 miles to 50 miles. The counties were combined with the sectors to determine which counties fell within each sector. The area of each county within a given sector was calculated to determine the area fraction of a county or counties that comprise each sector. The decennial growth rate for each county was converted to an equivalent annual growth rate. The annual growth rate in each sector was then calculated by the sum of the products of the annual growth rate of each county within a sector and the fraction of the area in that sector occupied by that county. This weighted-average annual growth rate for each sector is given in Tables F.2-3 and F.2-4.

Page F-10

VIRGIL C. SUMM'iER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.2-1 ESTIMATED POPULATION DISTRIBUTION WITHIN A 10-MILE RADIUS OF VCSNS, YEAR 2042 Sector 0-1 mile 1-2 miles 2-3 miles 3-4 miles 4-5 miles 5-10 miles 10-mile total N 0 0 0 16 9 267 292 NNE 0 0 0 20 364 216 600 N rE 0 0 7 0 0 207 214 E]NE 0 144 89 1 60 420 714 E 0 72 0 8 51 661 792 SE 0 0 68 0 13 597 678 SI -E 0 156 83 42 143 339 763 S SE 0 7 0 26 0 1,611 1,644 S 0 0 0 1 138 1,806 1,945 SS3W 0 0 3 11 78 2,199 2,291 SiW 0 0 33 75 23 1,153 1,284 wSW 0 0 0 16 241 1,181 1,438 w 0 15 15 25 0 465 520 w'NW 0 0 0 0 28 1,104 1,132 N'W 0 0 0 32 74 367 473 NTNW 0 0 12 51 99 323 485

)tal 0 394 310 324 1,321 12,916 15,265 TABLE F.2-2 ESTIMATED POPULATION DISTRIBUTION WITHIN A 50-MILE RADIUS OF VCSNS, YEAR 2042 Sector 0-10 miles 10-20 miles 20-30 miles 3040 miles 40-50 miles 50-mile total N 292 921 8,291 6,705 49,643 65,852 N'NE 600 410 13,351 10,229 206,009 230,599 NtE 214 1,838 4,514 15,800 65,188 87,554 E114E 714 11,201 1,029 2,934 20,973 36,851 E 792 2,969 5,432 29,636 50,040 88,869 ES3E 678 4,796 58,929 19,997 8,201 92,601 S- 763 22,327 343,898 61,527 15,997 444,512 SS 5E 1,644 104,555 275,790 49,253 19,112 450,354 S 1,945 24,968 53,003 25,550 13,195 118,661 SS 5W 2,291 15,496 34,764 21,126 11,351 85,028 SVv 1,284 4,316 6,542 15,571 39,729 67,442 SW 1,438 5,344 3,596 6,349 15,510 32,237 w

W] 520 23,881 3,062 6,881 77,271 111,615 NW 1,132 1,170 5,509 44,286 52,446 104,543 473 804 3,972 5,308 15,393 25,950 NI vW 485 482 2,237 18,414 14,454 36,072 Toatal 15,265 225,478 823,919 339,566 674,512 2,078,740 Page Page F-1l1

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.2-3 ESTIMATED ANNUAl *POPIuIATION GROWTH RATE WITHIfN A 10-MILE J

RADIUS OF VCSNS Sector 0-1 mile 1-2 miles 2-3 miles 3-4 miles 4-5 miles 5-10 miles N 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 N'NE 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 NIE 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 ENE 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 E 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 ESE 1.0051 1.0051 1.0051 1.0051 1.0051 1.0051 SE 1.0051 1.0051 1.0051 1.0051 1.0051 1.0059 S SE 1.0051 1.0051 1.0051 1.0051 1.0066 1.0107 S 1.0051 1.0051 1.0051 1.0059 1.0096 1.0171 S SW 1.0051 1.0051 1.0061 1.0085 1.0085 1.0137 SW 1.0051 1.0053 1.0079 1.0085 1.0085 1.0085 VSW 1.0051 1.0075 1.0085 1.0085 1.0085 1.0085 Vq/ 1.0051 1.0065 1.0084 1.0085 1.0085 1.0085 V*INW 1.0051 1.0051 1.0065 1.0084 1.0085 1.0085 NFW 1.0051 1.0051 1.0051 1.0057 1.0072 1.0083 NNW 1.0051 1.0051 1.0051 1.0051 1.0051 1.0052 The NRC 1990 sector population data for VCSNS provided in NUREG/CR-6525 (Reference 37), was projected to the year 2042 using the county area-weighted-average annual growth rate in each sector. The county populations in 1990 and 2000 are provided in Reference 38. It was assumed that the annual population growth rate would remain constant to that reported between 1990 and 2000. Using the sector-specific population growth rates, projections were made for the year 2042 by multiplying the 1990 sector population data by the annual growth rate raised to the power of 52 (2042-1990 = 52).

Economy MACCS2 requires the spatial distribution of certain economic data (fraction of land devoted to farming, annual farm sales, fraction of farm sales resulting from dairy production, and property value of farm and non-farm land) in the same manner as the population. This was done by specifying the data for each of the 22 South Carolina counties surrounding the plant, to a distance of 50 miles. The values used for each of the 160 sectors was then the data corresponding to that county which made up a vast majority of the land in that sector. For 22 sectors, no county encompassed more than two-thirds of the area, so conglomerate data (weighted by the fraction of each county in that sector) was defined.

Page F-12

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.2-4.

ESTIMATED ANNUAL POPULATION GROWTH RATE WITHIN A 10 TO 50-MILE RADIUS OF VCSNS Sector 0-10 miles 10-20 miles 20-30 miles 30-40 miles 40-50 miles N See Table F.2-3 1.0052 1.0057 1.0125 1.0227 NNE See Table F.2-3 1.0051 1.0057 1.0081 1.0215 NE See Table F.2-3 1.0051 1.0054 1.0085 1.0132 ENE See Table F.2-3 1.0051 1.0068 1.0155 1.0144 E See Table F.2-3 1.0051 1.0077 1.0186 1.0189 ESE See Table F.2-3 1.0092 1.0124 1.0154 1.0083 SE See Table F.2-3 1.0113 1.0122 1.0117 1.0127 SSE See Table F.2-3 1.0190 1.0256 1.0232 1.0170 S See Table F.2-3 1.0245 1.0257 1.0254 1.0169 SSW See Table F.2-3 1.0209 1.0233 1.0195 1.0173 SW See Table F.2-3 1.0089 1.0160 1.0161 1.0282 WSW See Table F.2-3 1.0085 1.0127 1.0137 1.0139 W See Table F.2-3 1.0085 1.0091 1.0153 1.0142 WNW See Table F.2-3 1.0085 1.0134 1.0181 1.0180 NW See Table F.2-3 1.0054 1.0031 1.0007 1.0095 NNW See Table F.2-3 1.0033 0.9998 0.9997 1.0094 In addition, generic economic data that are applied to the region as a whole were revised from the MACCS2 sample problem input when better information was available. These revised parameters include per diem living expenses (applied to owners of interdicted properties and relocated populations), relocation costs (for owners of interdicted properties), value of farm and non-farm wealth, and fraction of farm wealth from improvements (e.g., buildings, equipment).

Agriculture Agricultural production information was taken from the 1997 Agricultural Census (Reference 39). Production within 50 miles of VCSNS was estimated based on those counties within this radius. Production in those counties, which lie partially outside of this area, was multiplied by the fraction of the county within the area of interest. Cotton and tobacco, non-foods, were harvested from 5 percent of the croplands within 50 miles of the site. Of the food crops, stored forage (22 percent of total cropland, consisting of hay) and grain (11 percent of the total cropland, made up of corn and wheat) were harvested from the largest areas. The total food and commercial harvest consumed Page F-13

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT almost 50 percent of the croplands within 50 miles of VCSNS; pasture made up another 38 percent of this land.

The lengths of the growing seasons for grains, roots, and legumes were obtained from Reference 40. The duration of the growing seasons for the remaining crop categories (pasture, stored forage, green leafy vegetables, and other food crops) were taken to be the same as those used previously at a site in the neighboring state of Georgia (Reference 31).

Nuclide Release The core inventory at the time of the accident was based on the input supplied in the MACCS2 User's Guide (Reference 34). The core inventory corresponds to the end-of cycle values for a 3,412-MWth PWR plant. A scaling factor of 0.850 was used to provide a representative core inventory of 2,900-MWth at VCSNS. Table F.2-5 gives the estimated VCSNS core inventory. Release frequencies (1.18x10 7 , 1.78x10 7 , and 4.04x10-7 for sequences SGL16BH, ILM08BH, and TRE13NH, respectively) and nuclide release fractions (of the core inventory) were analyzed to determine the sum of the exposure (50-mile dose) and economic (50-mile economic costs) risks from large early release sequences SGL16BH, ILM08BH, and TRE13NH. VCSNS nuclide release categories were related to the MACCS2 categories, as shown in Table F.2-6.

Where appropriate, multiple release duration periods were defined that represented the duration of each category's releases. Each VCSNS category corresponded with a single release duration (either puff or continuous); MACCS2 categories Te and Ce required multiple releases.

The reactor building has a diameter of 154 feet and a height of 190 feet. All releases were modeled as occurring at ground level. The thermal content of each release was conservatively assumed as to be the same as ambient (i.e., buoyant plume rise was not modeled).

Evacuation The initiating event for each sequence was taken as time zero relative to the core containment response times. A General Emergency is declared when plant conditions degrade to the point where it is judged that there is a credible risk to the public; for example, for the SGL16BH case a General Emergency will be declared when two of the three fission product barriers have been breached and the third is in jeopardy. A General Emergency is declared at 22.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months (after initiating event) for Sequence SGL16BH, at 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months for Sequence ILM08BH, and 6.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months for Sequence TRE13NH.

Page F-14

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.2-5 ESTIMATED VCSNS CORE INVENTORY Core Inventory Core Inventory Nucide (Becquerels) Nuclide (Becquerels) 6 7 Co-58 2.740x 101 Te-13 im 3.978xl 0' Co-60 2.095x1 016 Te-132 3.959x10' 8 Kr-85 2.1 04X,016 1-131 2.725x10' 8 7

Kr-85m 9.852x10' 1-132 4.016x10' 8 Kr-87 1.800x10'8 1-133 5.762x10'8 Kr-88 2.434xl 01 1-134 6.324xl 01 Rb-86 5 1.605x10' 1-135 5.433xl 01 Sr-89 3.052xl0l' Xe-133 5.765x10l' 7

Sr-90 1.647x1001 Xe-135 1.082xl0l' 8

Sr-91 3.924x1001 Cs-134 3.675x 1017 7

Sr-92 4.083x10' 8 Cs-136 i.li9XIO' 7 7 Y-90 1.767xl 01 Cs-137 2.054xiO01 8

Y-91 3.7 18x10' 8 Ba-i 39 5.340xl 0' 8

Y-92 4.098x10' Ba-140 5.284x10' 8 Y-93 4.636x10'8 La-140 5.399xi0' 8 Zr-95 4.697x10' 8 La-141 4.952x10' 8 Zr-97 4.895x1 018 La-142 4.774x10'8 Nb-95 4.440x10l' Ce-141 4.803xi0' 8 8

Mo-99 5.1 83x10l' Ce-143 4.670xi 01 8

Tc-99m 4.474x10' 8 Ce-144 2.894xl 0' Ru-103 3.86 ixiO' Pr-143 4.586xi0' 8 Ru-lOS 2.51 lxi10" Nd-147 2.050x10' 8 7

Ru-106 8.772xl 01 Np-239 5.494xl0' 9 5

Rh-lOS 1.739xl0l' Pu-238 3.1 i4xiO01 7 4 Sb-i 27 2.369x1001 Pu-239 7.024xi101 7 4 Sb-i29 8.391IX,10 Pu-240 8.857x 101 7 7 Te-127 2.288x1001 Pu-241 1.492x 101 6 3 Te-127m 3.029x100' Am-241 9.852x100' 7 6 Te- 129 7.877x1001 Cm-242 3.77 IXI10 7 5 Te-129m 2.077x1001 Cm-244 2.207xl 01 Page F-15

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F12-6 MACCS2 RELEASE CATEGORIES VS. VCSNS RELEASE CATEGORIES MACCS2 Release Categories VCSNS Release Categories Xe/Kr 1 - noble gases I 2 - CsI Cs 2 & 6 - CsI and CsOH Te 3 & 11- TeO 2 and Te 2 Sr 4 - SrO Ru 5 - MoO 2 (Mo is in Ru MACCS2 category)

La 8 - La 203 Ce 9 - CeO2 & U0 2 Ba 7 - BaO Sb (supplemental category) 10- Sb The MACCS2 User's Guide input parameters of 95 percent of the population within 10 miles of the plant (Emergency Planning Zone) evacuating and 5 percent not evacuating were employed. These values have been used in similar studies (e.g., Hatch and Calvert Cliffs, References 31 and 15, respectively) and are conservative relative to the NUREG- 1150 study, which assumed evacuation of 99.5 percent of the population within the EPZ (Reference 35). The- evacuees are assumed to evacuate at a radial speed of 0.43 meter/second (Reference 36). This speed is taken from the minimum speed from any evacuation zone under adverse weather conditions.

Meteorolouv Annual meteorology data sets from 1996 through 2000 were investigated for use in MACCS2. The 1997 data set was found to result in the largest doses and was subsequently used to create the one-year sequential hourly data set used in MACCS2.

Wind speed and direction from the 10-meter sensor were combined with precipitation (hourly cumulative) and atmospheric stability (specified according to the vertical temperature gradient as measured between the 60-meter and 10-meter levels). Hourly stability was classified according to the scheme used by the NRC (Reference 15).

Atmospheric mixing heights were specified for AM and PM hours. These values were taken as 380 and 1,450 meters, respectively (Reference 43).

Page F-16

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT MACCS2 Results The resulting annual risks from VCSNS early release sequences SGL16BH, ILM08BH, and TRE13NH (and their sum) are provided in Table F.2-7. The largest risks are from ILM08BH, it having the largest release, especially of Cs, I, and Sr. This sequence contributes two-thirds of the risks from these large early releases.

TABLE F.2-7 RESULTS OF VCSNS LEVEL 3 PRA ANALYSIS Sum of Sequence SGL16BH ILM08BH TRE13NH annual risk Population dose risk (person-rem) 0-50 miles 0.273 0.628 0.053 0.954 Total economic cost risk ($)

0-50 miles 741 1,994 4 2,739 Quantification of the base case shows a baseline CDF of 5.59x10 5 /yr based on 28,435 cutsets (accident scenarios). The baseline LERF is 6.99x10 7/yr based on 45,837 cutsets.

MACCS2 calculated the annual baseline population dose risk within 50 miles at 0.954 person-rem. The total annual economic risk was calculated at $2,739.

Page F-17

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.3 Cost-Benefit Analysis F.3.1 Offsite Exposure Cost The baseline annual offsite exposure risk was converted to dollars using the NRC's conversion factor of $2,000 per person-rem (Reference 30, Section 5.7.1.2), and discounting to present value using NRC's standard formula (Reference 30, Section 5.7.1.3):

Wpha = C

Zpha Where:

Wph, = monetary value of public health risk after discounting C = [ 1-exp(-rtf)]/r tf = years remaining until end of facility life = 20 years r = real discount rate (as fraction) = 0.07/year Zpha = monetary value of public health (accident) risk per year before discounting

($/year)

The calculated value for C using 20 years and a 7 percent discount rate is 10.76.

Therefore, calculating the discounted monetary equivalent of accident risk involves multiplying the dose risk (0.95 person-rem per year) by $2,000 and by the C value (10.76). The calculated offsite exposure cost is $20,540.

F.3.2 Offsite Economic Cost-Risk The baseline VCSNS PSA offsite economic cost-risk (OECR) is $2,739. This cost-risk is an annual estimate based on conditions present at the end of the license renewal period.

The baseline OECR must also be discounted to present value in order to account for the entire license renewal period. This is performed in the same manner as for public health risks and uses the same C value. The resulting estimate is $29,480.

F.3.3 Onsite Exposure Cost-Risk Occupational health cost-risk was evaluated using the NRC methodology in Reference 30, Section 5.7.3, which involves separately evaluating "immediate" and long-term doses.

Page F- 18

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Immediate Dose - For the c :n which the plant is in operation, the equation that NRC recommends using (Refer, 30, Sections 5.7.3 and 5.7.3.3) is:

Equation 1:

WI° = R{(FDI°)s - (FDIO)A }* {[1.-exp(-rtf)]

Where:

Wio = monetary value of accident risk avoided due to immediate doses, after discounting R = monetary equivalent of unit dose ($/person-rem)

F = accident frequency (events/yr)

D1 o = immediate occupational dose (person-rem/event) s = subscript denoting status quo (current conditions)

A = subscript denoting after implementation of proposed action r = real discount rate tf = years remaining until end of facility life.

The values used in the VCSNS analysis are:

R = $2,000/person-rem r = 0.07 Dio = 3,300 person-rem/accident (best estimate, from Reference 30, Section 5.7.3.1) tf = 20 years (license renewal period)

F = 5.6E-5 (baseline CDF)

For the basis discount rate, assuming FA is zero, the best estimate of the immediate dose cost is:

W10 = R(FD10 *{[IeXP('f)]}

2000 * (5.6E - 5

3,300) * - exp(-0.07

20)}

= $3,978 Page F-19

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Long-Term Dose - For the case in which the plant is in operation, the NRC equation (Reference 30, Sections 5.7.3 and 5.7.3.3) is:

Equation 2:

WLTO `R{(FDLTo)s - (FDLTO)A}*{[I - exp(-rtf)]}*{[I -exp(-rm)]}

Where:

Wio = monetary value of accident risk avoided due to long-term doses, after discounting, $

m = years over which long-term doses accrue The values used in the VCSNS analysis are:

R = $2,000/person-rem r = 0.07 DLTO = 20,000 person-rem/accident (best estimate, Reference 30, Section 5.7.3.1) m = 10 years (estimate) tf = 20 years (license renewal period)

F = 5.6E-5 (baseline CDF)

For the basis discount rate, assuming FA is zero, the best estimate of the long-term dose is:

WLm =R(F'DLTO)S [1-exp(-rtf)}[1-exp(-rm)]}

= 2000* (5.6E- 5* 20,000)* [1-exp(-0.07* 20)]l. - exp(-0.07* 10)] J

= $17,338 Page F-20

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Total Occupational Exposure - Combining Equations 1 and 2 above and using the above numerical values, the total accident related on-site (occupational) exposure avoided (Wo) based on Summer Station's contribution to independent, single-unit core damage is:

Wo = Wl + WETo =($3,978 + $17,338) = $21,316 F.3.4 Onsite Cleanup and Decontamination Cost The net present value that NRC provides for cleanup and decontamination for a single event is $1.1 billion discounted over a 10-year cleanup period (Reference 30, Section 5.7.6.1). NRC uses the following equation to integrate the net present value over the average number of remaining service years:

UCD =[-* ]D[1 -exp(-rtf)]

Where:

PVcD = Net present value of a single event r = real discount rate tf = years remaining until end of facility life.

The values used in the VCSNS analysis are:

PVcD = $1.1E9 r = 0.07 tf = 20 The resulting net present value of cleanup integrated over the license renewal term,

$1.18E10 must be multiplied by the baseline CDF of 5.6E-5 to determine the expected value of cleanup and decontamination costs. The resulting monetary equivalent is

$662,995.

F.3.5 Replacement Power Cost Long-term replacement power cost was determined following NRC methodology in Reference 30, Section 5.7.6.2. The net present value of replacement power for a single event, PVRp, was determined using the following equation:

PVRP =E $1.2E8] *[1- exp(-rtf)] 2 Page F-21

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Where:

PVRP = net present value of replacement power for a single event, ($)

r = 0.07 tf = 20 years (license renewal period)

To attain a summation of the single-event costs over the entire license renewal period, the following equation is used:

UTRP [ PVRPl r ep(rt )]2 Where:

UR = net present value of replacement power over life of facility ($-year)

After applying a correction factor to account for VCSNS size relative to the "generic" reactor described in NUREG/BR-0184 (i.e., 966 MWe/910 MWe), the replacement power costs are determined to be 8.38E9 ($-year). Multiplying this value by the baseline CDF (5.6E-5) results in a replacement power cost of $469,049.

F.3.6 Baseline Screening The sum of the baseline costs for a core damage event is as follows:

Offsite exposure cost = $20,540 Offsite economic cost = $29,480 Onsite exposure cost = $21,316 Onsite cleanup cost = $662,995 Replacement power cost = $469,049 Total cost = $1,203,380 This cost estimate was used in screening out SAMAs that are not economically feasible; if the estimated cost of implementing a SAMA exceeded $1.203 million, it was discarded from further analysis. Exceeding this threshold would mean that a SAMA would not have a positive net value even if it could eliminate all severe accident costs. On the other hand, if the cost of implementation is less than this value, then a more detailed examination of the potential fractional risk benefit that can be attributed to the SAMA is performed.

Page F-22

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.4 Phase 1 SAMA Analysis: SAMA Candidates and Screening Process An initial list of 268 SAMA candidates is presented in Table F.4-1. This list was then screened to remove those candidates that were not applicable to VCSNS due to design differences or high implementation costs. In addition, SAMAs were eliminated if they were related to changes that would be made during the design phase of a plant rather than to an existing plant. These would typically screen on high cost, but they are categorized separately for reference purposes. The SAMA screening process is presented graphically in Figure F. 1-1.

A majority of the SAMAs were removed from further consideration because they did not apply to the Westinghouse 3 Loop PWR design used at VCSNS. The SAMA candidates that were found to be in place at VCSNS were also screened from further consideration.

The SAMAs related to design changes prior to construction (primarily consisting of those candidates taken from the ABWR SAMAs) were removed, as they were not applicable to an existing site. Any candidate known to have an implementation cost that far exceeds any possible risk benefit was screened from further analysis. Any SAMA candidates that were sufficiently similar to other SAMA candidates were treated in the same manner as those to which they were related to; either combined or screened from further consideration.

A preliminary cost estimate was prepared for each of the remaining candidates to focus on those that had the possibility of having a positive benefit and to eliminate those whose costs were beyond the possibility of any corresponding benefit (as determined by the VCSNS baseline screening cost). When the screening cutoff of $1,203,380 was applied, a majority of the remaining SAMA candidates were eliminated, as their implementation costs were more expensive than the maximum postulated benefit associated with the elimination of all risk associated with full power internal events. This left 32 SAMA candidates for further analysis (Table F.4-2).

Those SAMAs that required a more detailed cost-benefit analysis are evaluated in Section F.5, using the combined methods described in F.2 and F.3.

Page F-23

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA Phase 1 Source Screening Phase 2 SAMA ID Reference of Criteria SAMA ID number SAMA title SAMA Result of potential enhancement [See Notes] Disposition number Improvements Related to RCP Seal LOCAs (Loss of CC or SW) 1 Cap downstream piping of 1 SAMA would reduce the #3 - Already This modification has already been implemented at N/A normally closed component frequency of a loss of component implemented VCSNS (Reference 21).

cooling water drain and cooling event, a large portion of at VCSNS vent valves. which was derived from catastrophic failure of one of the many single isolation valves.

2 Enhance loss of component 2 SAMA would reduce the potential #3 - Already Plant abnormal operating procedures direct trip of N/A cooling procedure to for reactor coolant pump (RCP) implemented RCPs on loss of CCW or high temperature of the facilitate stopping reactor seal damage due to pump bearing at VCSNS motor bearings, seal water bearings, or seal water coolant pumps. failure. outlet.

3 Enhance loss of component 2 SAMA would reduce the potential #2 - Similar Loss of component cooling water at VCSNS does not N/A cooling procedure to for RCP seal failure. item is lead directly to a seal LOCA. While CCW provides present desirability of addressed cooling to the Charging Pumps, there are alternate cooling down reactor under other methods of cooling the Charging Pumps. Abnormal coolant system (RCS) prior proposed operating procedures provide directions to align a to seal LOCA. SAMAs diverse set of cooling sources including Chilled Water, Fire Service Water, and Demineralized Water. Use of these systems to provide cooling to the Charging Pumps such that seal injection remains available is considered to be preferable to a rapid cooldown of the plant to prevent seal failure. This is treated in SAMA

5.

F-24

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMIA title of SAMA Result of potential enhancement [See Notes] Disposition number 4 Provide additional training 2 SAMA would potentially improve the #3 - Already Loss of Component Cooling Water scenarios receive N/A on the loss of component success rate of operator actions after a implemented significant attention in the VCSNS training program.

cooling, loss of component cooling (to restore at VCSNS Further training or enhancements would impact RCP seal damage). operator action reliability however, the potential improvement would be difficult to quantify. No measurable change would result from implementing this change at V.C. Summer.

5 Provide hardware 1 SAMA would reduce effect of loss of #3 - Already The charging pumps are normally cooled by N/A connections to allow 2 component cooling by providing a implemented Component Cooling Water (CCW); however, on loss another essential raw means to maintain the centrifugal at VCSNS of normal cooling, abnormal operating procedures cooling water system to charging pump seal injection after a have been developed to direct alignment of Chilled cool charging pump seals, loss of component cooling. Water (VU) (preferred system), Deminerahzed Water (DW), or the Fire Service Water System to the charging pumps (Reference 16).

6 Procedure changes to allow 11 SAMA would allow continued #1 - Not Emergency Feedwater pumps (an approximate PWR N/A cross connection of motor operation of both RHRSW pumps on applicable to equivalent) are cooled by the process fluid (Reference cooling for RHRSW a failure of one train of PSW. the VCSNS 16).

pumps. Design 7 Proceduralize shedding 2 SAMA would increase time before #3 - Already VCSNS abnormal operating procedures direct N/A component cooling water the loss of component cooling (and implemented shedding unnecessary CCW loads.

loads to extend component reactor coolant pump seal failure) in at VCSNS cooling heatup on loss of the loss of essential raw cooling water essential raw cooling water. sequences.

8 Increase charging pump 2 SAMA would lengthen the time #6 - Retain N/A lube oil capacity. before centrifugal charging pump failure due to lube oil overheating in loss of CC sequences.

9 Eliminate the RCP thermal 2 SAMA would prevent the loss of #3 - Already Loss of Component Cooling Water does not directly N/A barrier dependence on recirculation pump seal integrity after implemented result in core damage at VCSNS. The charging component cooling such a loss of component cooling. Watts at VCSNS pumps, which provide seal injection to the RCPs, are that loss of component Bar Nuclear Plant IPE said that they normally cooled by Component Cooling Water with cooling does not result could do this with essential raw backup cooling from Chilled Water, Denineralized directly in core damage. cooling water connection to RCP Water or Fire Service Water (Reference 16).

seals.

/ , F /

K K

(

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 10 Add redundant DC control 3 SAMA would increase reliability of #6 - Retain N/A 2 power for PSW pumps C PSW and decrease core damage and D. frequency due to a loss of SW.

II Create an independent RCP SAMA would add redundancy to #5 - Cost While seal injection is an important function, the cost N/A seal injection system, with RCP seal cooling alternatives, would be estimate for installation of new seals alone exceeds a dedicated diesel. reducing CDF from loss of more than $2.5 million. A new, independent seal injection component cooling or service water risk benefit system is judged to greatly exceed this cost and the or from a station blackout event. maximum averted cost risk of $1.2 million (Reference 24).

12 Use existing hydro-test 4 SAMA would provide an independent #6 - Retain N/A 3 pump for RCP seal seal injection source, without the cost injection. of a new system.

13 Replace ECCS pump motor SAMA would eliminate ECCS #5 - Cost The cost of this enhancement is expected to greatly N/A with air-cooled motors. dependency on component cooling would be exceed the maximum averted cost risk that could be system (but not on room cooling). more than gained by its implementation. Installation of an risk benefit additional Service Water pump has been estimated at

$5.9 million; this change is considered to be similar to installing new ECCS pumps. While new piping and power supplies would not have to be installed to support the new ECCS pumps, unneeded CCW and Chilled Water piping would have to be removed and capped and the number of new ECCS pumps is five compared with only one in the reference case.

14 Install improved RCS SAMA would reduce probability of #3 - Already New RCP seals were installed over the span of refuel N/A pump seals. RCP seal LOCA by installing RCP implemented outages 10, 11, and 12.

seal 0-ring constructed of improved at VCSNS materials.

15 Install additional SAMA would reduce probability of #5 - Cost Based on engineering judgement, the cost of this N/A component cooling water loss of component cooling leading to would be enhancement is expected to greatly exceed the pump. RCP seal LOCA. more than maximum averted cost risk ($1.2 million) that could be risk benefit gained by its implementation. Installation of an additional Service Water pump has been estimated at

$5.9 million; this change is considered to be similar to installing an additional CCW pump.

F-26

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE~

APPENDIX E - ENVIRONMENTAL REPORI' ____________

TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 16 Prevent centrifugal 1 SAMA modification would reduce #6 - Retain N/A 4 charging pump flow the frequency of the loss of RCP seal diversion from the relief cooling if relief valve opening causes valves, a flow diversion large enough to prevent RCP seal injection.

17 Change procedures to 1 SAMA would reduce CDF from loss #3 - Already Letdown flow isolation is already directed in plant N/A isolate RCP seal letdown of seal cooling, implemented AOPs on loss of CCW.

flow on loss of component at VCSNS cooling, and guidance on loss of injection during seal LOCA.

18 Implement procedures to 1 SAMA would allow HPSI to be #4 - No The high pressure injection pumps at VCSNS (the N/A stagger high-pressure extended after a loss of service water, significant charging pumps) are normally cooled by CCW, which safety injection (HPSI) safety in turn is cooled by Service Water; however, the pump use after a loss of benefit. charging pumps have three alternate, diverse cooling service water. sources (Fire Service Water, Demineralized Water, and Chilled Water). Addition of another method to prevent charging pump overheating on loss of Service Water would not significantly improve charging pump reliability (Reference 16).

19 Use fire protection system I SAMA would reduce the frequency #5 - Cost Fire protection is a low head system at VCSNS and N/A pumps as a backup seal of the RCP seal LOCA and the SBO would be cannot be used as a HP injection source.

injection and high-pressure CDF. more than Modifications to convert it to a high pressure system makeup. nisk benefit would be a high cost improvement. Installation of new high pressure piping, a high head, high flow pump (as it would also have to support the fire system) and a supporting diesel generator or pump motor is similar in scope to SAMA 179. The cost is also considered to be similar ($5 million to $10 million, Reference 24) and is greater than the maximum averted cost-risk for VCSNS ($1.2 million).

(.C

(

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 20 Enhance procedural I SAMA would reduce the frequency #3 - Already VCSNS is equipped with a third "swing" pump that N/A guidance for use of cross of the loss of component cooling implemented can be aligned to either CCW loop on loss of the tied component cooling or water and service water. at VCSNS running pump. Use of this pump is proceduralized and service water pumps. is judged to meet the intent of this SAMA. The Service Water System is designed in the same way.

21 Procedure enhancements 1 SAMA would potentially improve the #2 - Similar See SAMAs 20, 27, 30,90, 95, 96, 97, and 103 N/A and operator training in 2 success rate of operator actions item is support system failure subsequent to support system failures. addressed sequences, with emphasis 16 under other on anticipating problems proposed and coping. SAMAs.

22 Improved ability to cool the SAMA would reduce the probability #6 - Retain Any CCW train can be aligned to either RHR load and 5 residual heat removal heat of a loss of decay heat removal by VCSNS is a single unit site, so there can be no inter exchangers. implementing procedure and unit cross-tie. Service water can also be cross-tied to hardware modifications to allow CCW for emergency cooling. Modification of the fire manual alignment of the fire protection system to provide cooling to the CCW heat protection system or by installing a exchangers has been estimated at $565,000 in component cooling water cross-tie. Reference 19. While this estimate appears to include only the piping modifications, purchase of new pump(s) may not increase the cost of implementation above the maximum averted cost-risk for VCSNS

($1.2 million). This SAMA will be examined in more detail in Phase 2.

23 8.a. Additional Service Advanced SAMA would conceivably reduce #5 - Cost The cost of implementing this SAMA has been N/A Water Pump Reactors common cause dependencies from would be estimated at approximately $5.9 million and is greater SAMDAs SW system and thus reduce plant risk more than than the maximum averted cost-risk ($1.2 million).

through system reliability risk benefit improvement.

F-28

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMIA title of SAMA Result of potential enhancement [See Notes] Disposition number 24 Create an independent RCP 15 This SAMA would add redundancy to #5 - Cost Calvert Cliffs Nuclear Power Plant estimated the cost N/A seal injection system, RCP seal cooling alternatives, would be of installing new seals that do not require cooling to be without dedicated diesel reducing the CDF from loss of CC or more than greater than $2.5 million (Reference 24). Based on SW, but not SBO. risk benefit this estimate and engineering judgement, the cost of installing a completely new and independent seal injection system would significantly exceed the maximum averted cost-risk ($1.2 million).

Improvements Related to Heating, Ventilation, and Air Conditioning (HVAC) 25 Provide reliable power to 2 SAMA would increase availability of #3 - Already CR HVAC is supplied by Class lE, redundant power N/A control building fans. control room ventilation on a loss of implemented (Reference 16).

power. at VCSNS 26 Provide a redundant train 1 SAMA would increase the #5 - Cost Three rooms have been identified as requiring room N/A of ventilation, availability of components dependent would be cooling at VCSNS: the ESF switchgear room, the on room cooling, more than Relay Room, and the EDG room. The Relay Room risk benefit and EDG rooms already have redundant HVAC trains.

While the switchgear rooms themselves are redundaiji, there is only one train of HVAC to each room. The cost of installing a redundant, diverse train of ItVAC for a switchgear room has been estimated at $10 million (Reference 24) and far exceeds the maximum averted cost-risk for VCSNS ($1.2 million).

27 Procedures for actions on I1 SAMA would provide for improved #3 - Already Individual losses of room cooling are addressed by the N/A loss of HVAC. credit to be taken for loss of HVAC implemented VCSNS annunciator response procedures and plant sequences (improved affected at VCSNS AOPs direct alternate cooling given loss of the Chilled electrical equipment reliability upon a Water system, which supplies the HVAC system with loss of control building HVAC). cooling water.

28 Add a diesel building 1 SAMA would improve diagnosis of a #3 - Already High temperature in the switchgear room is already N/A switchgear room high loss of switchgear room HVAC. implemented alarmed in the VCSNS Control Room.

temperature alarm. Option 1: Install high-temp alarm. at VCSNS Option 2: Redundant louver and thermostat C. C

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 29 Create ability to switch fan SAMA would allow continued #1 - Not In the IPE, room cooling has been shown to be N/A power supply to DC in an operation in an SBO event. This applicable to required only for ESF Switchgear (SG), the Relay SBO event. SAMA was created for reactor core the VCSNS Room (RR), and the EDO rooms (Reference 16).

isolation cooling system room at Design Room heat-up calcs show that RR temp remains below Fitzpatrick Nuclear Power Plant. 1200 F. for the first 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months of an SBO with loss of HVAC. No equipment operability issues are identified for these conditions and given the 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months life of the batteries, no power would be available for cooling after this time. For the SG room, the major heat loads will not be present in an SBO as high voltage AC in unavailable by definition; however, there is a room heatup analysis available that shows the equipment in the room will remain operable even when energized during loss of HVAC. The SG room reaches 132' F.

at 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months without HVAC.

The equipment in this room can operate for 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months with the temp. above 1020 F. and 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months if greater than 132' F. For the EDO rooms, the EDGs will not be running in an SBO; thus, there will not be a significant heat load. Once the EDGs are available, the batteries would not be required to provide power for HVAC. For these reasons, use of the station batteries to provide power for HVAC does not benefit VCSNS.

30 Enhance procedure to 11 SAMA increases availability of #1 -Not Room cooling is not required for operation of SI or N/A instruct operators to trip required RHR/CS pumps. Reduction applicable to EFW at VCSNS.

unneeded RHR/CS pumps in room heat load allows continued the VCSNS on loss of room ventilation. operation of required RHR/CS Design pumps, when room cooling is lost.

F-30

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT' TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 31 Stage backup fans in 15 This SAMA would provide alternate #3 - Already There is already an alternate room cooling action N/A switchgear (SGR) rooms ventilation in the event of a loss of implemented implemented at VCSNS for high switchgear room SGR room ventilation, at VCSNS temperature. This action is to open the rooms' doors to allow natural circulation. Additionally, when Chilled Water is unavailable, each ESF switchgear room air handling unit has a non-safety direct expansion coil and associated condensing unit.

Improiements Related to Ex-Vessel Accident Mitigation/Containment Phenomena 32 Delay containment spray 2 SAMA would lengthen time of #4 - No For Large LOCA initiators, use of the sump as an N/A actuation after large RWST availability, significant injection source is required regardless of any action to LOCA. safety extend RWST availability. A potential benefit of this benefit. SAMA would be an increase in the time between the cue to switch to sump suction and core damage due.

This is due to the lower decay heat level that would be present at the time swap is required. The benefit would be reflected in the evaluation of the human action to complete the suction swap-over; however, the change in the HEP would be negligible as would the impact on the CDF and LERF (Reference 16).

33 Install containment spray 4 SAMA would extend the time over #2 - Similar See SAMA 32 N/A pump header automatic 7 which water remains in the RWST, item is throttle valves, when full CS flow is not needed. addressed under other proposed SAMAs.

34 Install an independent 5 SAMA would decrease the #5 - Cost Installation of a new, independent, suppression pool N/A method of suppression pool probability of loss of containment would be cooling system is similar in scope to installing a new cooling heat removal. For PWRs, a potential more than containment spray system, which has been estimated to similar enhancement would be to risk benefit cost approximately $5.8 million (Reference 24). This install an independent cooling system exceeds the maximum averted cost-nsk for VCSNS for sump water. ($1.2 million).

( (i.

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 35 Develop an enhanced 5 SAMA would provide a redundant #6 - Retain N/A 6 drywell spray system. At source of water to the containment to VCSNS, use of the CRDM control containment pressure, when Cooling System was used in conjunction with containment suggested as an additional heat removal.

containment temperature and pressure control source.

36 Provide dedicated existing 5 SAMA would provide a source of #2 - Similar See SAMA 35 N/A drywell spray system. water to the containment to control item is containment pressure, when used in addressed conjunction with containment heat under other removal. This would use an existing proposed spray loop instead of developing a SAMAs.

new spray system.

37 Install an unfiltered 5 SAMA would provide an alternate #1 - Not Containment heat removal to preserve containment N/A hardened containment vent. decay heat removal method for non applicable to integrity is not an issue for large, dry containments.

ATWS events, with the released the VCSNS The long time periods associated with the need to vent fission products not being scrubbed. Design with this type of containment would rule out any contribution to LERF, which dominates the offsite consequences. In addition, the estimated cost of installing an unfiltered containment vent ($3.1 million)

(Reference 24) is greater than the maximum averted cost-risk for VCSNS ($1.2 million).

38 Install a filtered 5 SAMA would provide an alternate #1 - Not Containment heat removal to preserve containment N/A containment vent to decay heat removal method for non applicable to integrity is not an issue for large, dry containments.

remove decay heat. ATWS events, with the released the VCSNS The long time periods associated with the need to vent fission products being scrubbed. Design with this type of containment would rule out any Option 1: Gravel Bed Filter contribution to LERF, which dominates the offsite consequences. In addition, the estimated cost of Option 2: Multiple Venturi Scrubber installing a filtered containment vent ($5.7 million)

(Reference 24) is significantly greater than the maximum averted cost-risk for VCSNS.

F-32

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 39 Install a containment vent 5 Assuming that injection is available, #2 - Similar See SAMAs 37, 38 N/A large enough to remove this SAMA would provide alternate item is ATWS decay heat. decay heat removal in an ATWS addressed event, under other proposed SAMAs.

40 Create/enhance hydrogen 10 SAMA would reduce hydrogen #6 - Retain N/A 7 recombiners with detonation at lower cost, using independent power supply. 1) a new independent power supply

2) a non-safety-grade portable generator

3) existing station batteries

4) existing AC/DC independent power supplies.

41 Install hydrogen 10 SAMA would provide a means to #3 - Already VCSNS already has thermal hydrogen recombiners. N/A recombiners. reduce the chance of hydrogen implemented detonation, at VCSNS 42 Create a passive design 4 SAMA would reduce hydrogen #2 - Similar See SAMA 40 N/A hydrogen ignition system. denotation system without requiring item is electric power. addressed under other proposed SAMAs.

43 Create a large concrete 5 SAMA would ensure that molten core #5 - Cost Core retention devices have been investigated in N/A crucible with heat removal debris escaping from the vessel would would be previous studies. IDCOR concluded that "core potential under the basemat be contained within the crucible. The more than retention devices are not effective risk reduction to contain molten core water cooling mechanism would cool risk benefit devices for degraded core events." Other evaluations debris. the molten core, preventing a melt- have shown the worth value for a core retention device through of the basemat. to be on the order of $7,000 (averted cost-risk) compared to an estimated implementation cost of over

$1 million (per unit).

Q.

p.

Q

I VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 44 Create a water-cooled 5 SAMA would contain molten core #5 - Cost Core retention devices have been investigated in N/A rubble bed on the pedestal. debris dropping on to the pedestal and would be previous studies. IDCOR concluded that "core would allow the debris to be cooled. more than retention devices are not effective risk reduction risk benefit devices for degraded core events." Other evaluations have shown the worth value for a core retention device to be on the order of $7,000 (averted cost-risk) compared to an estimated implementation cost of over

$1 million (per unit) (Reference 33).

45 Provide modification for 5 SAMA would help mitigate accidents #1 - N/A to This is a BWR issue. PWR containment does not N/A flooding the drywell head. that result in the leakage through the VCSNS include an equivalent structure/component that this drywell head seal. Design modification could be applied to and is screened from further consideration (Reference 16).

46 Enhance fire protection 5 SAMA would improve fission #1 - N/A to Current Fire Protection and Standby Gas Treatment N/A system and/or standby gas product scrubbing in severe accidents. VCSNS Systems do not have sufficient capacity to handle the treatment system hardware Design loads from severe accidents that result in a bypass or and procedures. breach of the containment. Loads produced as a result of RPV or containment blowdown would require large filtering capacities. These filtered vented systems have been previously investigated and found not to provide sufficient cost benefit.

47 Create a reactor cavity I SAMA would enhance debris #5 - Cost The estimated cost of implementation for this SAMA N/A flooding system. 3 coolability, reduce core concrete would be is $8.75 million (Reference 24), which greatly exceeds 6 interaction, and provide fission more than the maximum averted cost-risk ($1.2 million).

7 product scrubbing. risk benefit 48 Create other options for I SAMA would enhance debris #6 - Retain N/A 8 reactor cavity flooding. coolability, reduce core concrete VCSNS identified Fire interaction, and provide fission Water as a potential system product scrubbing.

that could be used as an alternate source for containment flooding.

F-34

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 49 Enhance air return fans (ice 1 SAMA would provide an independent #1 - N/A to VCSNS is not an ice condenser plant (Reference 16). N/A condenser plants), power supply for the air return fans, VCSNS reducing containment failure in SBO Design sequences.

50 Create a core melt source 8 SAMA would provide cooling and #5 - Cost Core retention devices have been investigated in N/A reduction system. containment of molten core debris, would be previous studies. IDCOR concluded that "core Refractory material would be placed more than retention devices are not effective risk reduction underneath the reactor vessel such risk benefit devices for degraded core events." Other evaluations that a molten core failing on the have shown the worth value for a core retention device material would melt and combine to be on the order of $7,000 compared to an estimated with the material. Subsequent implementation cost of over $1 million (Reference 33).

spreading and heat removal from the vitrified compound would be facilitated, and concrete attack would not occur.

51 Provide a containment 6 SAMA would prevent combustion of #1 - N/A to Containment inerting is important in small volume N/A inerting capability. 7 hydrogen and carbon monoxide VCSNS containments where hydrogen combustion can gases. Design challenge maximum pressure limits. Overpressure from ignition of combustible gases is not an important contributor to large, dry containment failures. In addition, this SAMA is not considered viable in a large volume containment where access may be required.

52 Use the fire protection 4 SAMA would provide redundant #2 - Similar See SAMA 35 N/A system as a backup source containment spray function without item is for the containment spray the cost of installing a new system. addressed system. under other proposed SAMAs 53 Install a secondary 9 SAMA would filter fission products #2 - Simular See SAMA 38 N/A containment filtered vent. released from primary containment, item is addressed under other proposed SAMAs.

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 54 Install a passive 9 SAMA would provide redundant #2 - Similar See SAMAs 35 and 52 N/A containment spray system. containment spray method without item is high cost. addressed under other proposed SAMAs.

55 Strengthen 9 SAMA would reduce the probability #5 - Cost Vendor documents discuss the cost of increasing the N/A primary/secondary 10 of containment overpressurization to would be containment pressure capacity, which is effectively containment. failure, more than strengthening the containment. This cost is estimated risk benefit assuming the change is made during the design phase whereas for VCSNS, the changes would have to be made as a retrofit. The cost estimated for the ABWR was $12 million and it is judged that to properly retrofit an existing containment that the cost would be greater. This cost of implementation for this SAMA exceeds the maximum averted cost-risk for VCSNS

($1.2 million).

56 Increase the depth of the 10 SAMA would prevent basemat melt- #5 - Cost Core retention devices have been investigated in N/A concrete basemat or use an through. would be previous studies. IDCOR concluded that "core alternative concrete more than retention devices are not effective risk reduction material to ensure melt- risk benefit devices for degraded core events." Other evaluations through does not occur. have shown the worth value for a core retention device to be on the order of $7,000 compared to an estimated implementation cost of over $1 million/site (Reference 33).

57 Provide a reactor vessel 10 SAMA would provide the potential to #5 - Cost This has been estimated to cost $2.5 million N/A exterior cooling system. cool a molten core before it causes would be (Reference 24) and exceeds the maximum averted vessel failure, if the lower head could more than cost-risk for VCSNS ($1.2 million).

be submerged in water, risk benefit 58 Construct a building to be 10 SAMA would provide a method to #5 - Cost Based on engineering judgement, the cost of this N/A connected to depressurize containment and reduce would be enhancement is expected to greatly exceed the primary/secondary fission product release, more than maximum averted cost risk ($1.2 million).

containment that is risk benefit maintained at a vacuum.

F-36

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 59 Refill CST. 14 SAMA would reduce the risk of core #6 - Retain This is pnmarily a BWR issue; however, a sinular case 9 damage dunng events such as for a PWR may be the use of the sump as a suction extended station blackouts or LOCAs source while in recirculation mode. In this case, the that render the suppression pool water used to refill the RWST is required to be unavailable as an injection source due borated. This would require installation of equipment to heat up. that can provide borated makeup water at a high flow rate, which is not currently installed at VCSNS.

60 Maintain ECCS suction on 14 SAMA would maintain suction on the #3 - Already For a PWR, a similar change could be to delay N/A CST. CST as long as possible to avoid implemented swapping the suction source from the RWST to the pump failure as a result of high at VCSNS sump; however, it is already common practice to inject suppression pool temperature. with the RWST for as long as is safely possible prior to swapping to rccirc mode. VCSNS EOPs do not direct swap to recire until RWST level is below 18 percent, where 6 percent is considered to be "empty."

61 Modify containment Industry SAMA would avoid forcing #4 - No For smaller containments such as the BWR Mark I, N/A flooding procedure to IPEEE containment venting, significant flooding to higher containment levels can cause restrict flooding to below Insights safety unnecessary pressurization of the containment and Top of Active Fuel. benefit force venting. Adequate cooling is possible with the level at top of active fuel. This is not an issue for larger volume containments.

62 Enhance containment Industry SAMA would improve likelihood of #3 - Already These steps are addressed in the VCSNS SAMGs. N/A venting procedures with IPEEE successful venting strategies. implemented respect to timing, path Insights at VCSNS selection and technique.

63 1 a. Severe Accident Advanced SAMA would lead to improved arrest #3 - Already The SAMGs have been implemented at VCSNS. N/A EPGs/AMGs Reactors of core melt progress and prevention Implemented SAMDAs of containment failure, at VCSNS 64 1 h Simulator Training for Advanced SAMA would lead to improved arrest #3 - Already VCSNS already provides Control Room Operators and N/A Severe Accident Reactors of core melt progress and prevention Implemented Technical Support Center staff with training on using SAMDAs of containment failure. at VCSNS the SAMGs to diagnose and to implement mitigative actions. Classroom training, self-study, and procedure driven drills are used to prepare personnel for plant operation during severe accidents.

f VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATIN(; LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 65 2.g. Dedicated Suppression Advanced SAMA would decrease the #2 - Similar See SAMA 34 N/A Pool Cooling Reactors probability of loss of containment item is SAMDAs heat removal, addressed under other proposed While PWRs do not have suppression SAMAs.

pools, a similar modification may be applied to the sump. Installation of a dedicated sump cooling system would provide an alternate method of cooling injection water.

66 3.a. Larger Volume Advanced SAMA increases time before #5 - Cost VCS is already a large, dry containment. Further N/A Containment Reactors containment failure and increases would be enlargement of the containment would be similar in SAMDAs time for recovery, more than scope to the ABWR design change SAMA to risk benefit implement a larger volume containment, but would likely exceed the $8 million estimate for that change as a retrofit would be required. This is greater than the maximum averted cost-risk ($1.2 million).

67 3.b. Increased Containment Advanced SAMA minimizes likelihood of large #2 - Similar See SAMA 55 N/A Pressure Capability Reactors releases. item is (sufficient pressure to SAMDAs addressed withstand severe accidents) under other proposed SAMAs.

68 3.c. Improved Vacuum Advanced SAMA reduces the probability of a #1 - N/A to This is a BWR issue. PWR containment does not N/A Breakers (redundant valves Reactors stuck open vacuum breaker. VCSNS include an equivalent structure/component that this in each line) SAMDAs Design modification could be applied to and is screened from further consideration (Reference 16).

69 3.d. Increased Temperature Advanced This SAMA would reduce the #1 - N/A to High temperature containment seal failure is not an N/A Margin for Seals Reactors probability of seal failure given loss VCSNS issue for a large, dry containment; computed SAMDAs of containment heat removal. It Design containment temperatures are generally below the would improve containment response failure threshold (Reference 16).

and reduce the probability of a radioactive release.

F-38

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 70 3.e. Improved Leak Advanced Improved leak detection within the #3 - Already Leak rates from the primary system are already N/A Detection Reactors containment would help identify implemented monitored as part of tech spec requirements and SAMDAs primary system leaks This would at VCSNS instrumentation is available to identify leaks lead to early identification of (Reference 19). Enhancing the procedures or potential LOCAs because leaks are equipment is possible, but the reduction in the LOCA often precursors of breaks, frequency resulting from these changes is judged to be negligible (Reference 16).

71 3.f. Suppression Pool Advanced Modifications to route release paths #1 - N/A to This is a BWR issue. PWR containment does not N/A Scrubbing Reactors through the suppression pool would VCSNS include an equivalent structure/component that this SAMDAs provide a means of filtering the Design modification could be applied to and is screened from release gases in the suppression pool further consideration.

water volume. This would reduce the amount of radionuclides released to the environment from the containment.

72 3.g. Improved Bottom Advanced SAMA reduces failure likelihood of #7 - ABWR Tii's is primarily a BWR issue. The mechanisms of N/A Penetration Design Reactors RPV bottom head penetrations Design Issue, ve-ssel breach due to contact with core debris are more SAMDAs not practical. of a concern with the larger penetrations present in the BWR bottom head design. Also, this is considered to be an initial design issue rather than a mod due to the prohibitive cost. Screened from further consideration.

73 4.a. Larger Volume Advanced SAMA would increase the size of the #1 - NIA to This is a BWR issue. PWR containment does not N/A Suppression Pool (double Reactors suppression pool so that heatup rate is VCSNS include an equivalent structure/component that this effective liquid volume) SAMDAs reduced, allowing more time for Design modification could be applied to and is screened from recovery of a heat removal system. further consideration. The pressure relief tanks are not used as an injection source and an increase in their size would not provide additional time to recover heat removal (Reference 16) 74 5.a/d. Unfiltered Vent Advanced SAMA would provide an alternate #2 - Similar See SAMA 37 N/A Reactors decay heat removal method with the item is SAMDAs released fission products not being addressed scrubbed, under other proposed SAMAs.

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 75 5.b/c. Filtered Vent Advanced SAMA would provide an alternate #2 - Similar See SAMA 38 and 53 N/A Reactors decay heat removal method with the item is SAMDAs released fission products being addressed scrubbed. under other proposed SAMAs.

76 6.a. Post Accident Inerting Advanced SAMA would reduce likelihood of #2 - Similar See SAMA 51 N/A System Reactors gas combustion inside containment. item is SAMDAs addressed under other proposed SAMAs.

77 6.b. Hydrogen Control by Advanced SAMA would reduce likelihood of #3 - Already The SAMG developers have considered the possibility N/A Venting Reactors gas combustion inside containment. Implemented of venting for hydrogen control, but the actions SAMDAs at VCSNS considered most appropriate for VCSNS do not include venting for control. Hydrogen ignition and hydrogen recombination are directed to maintain low hydrogen concentrations within containment during an accident.

78 6.c. Pre-inerting Advanced SAMA would reduce likelihood of #2 - Similar See SAMAs 51 and 76 N/A Reactors gas combustion inside containment. item is SAMDAs addressed under other proposed SAMAs.

79 6.d. Ignition Systems Advanced This SAMA would burn combustible #2 - Similar See SAMA 42 N/A Reactors gases before they reach levels at item is SAMDAs which combustion would challenge addressed containment integrity. under other proposed SAMAs.

F-40

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICF,NSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 80 6.c. Fire Suppression Advanced This SAMA would help maintain a #1 - N/A to This is a BWR issue. PWR containments are large N/A System Inerting Reactors non-combustible atmosphere within VCSNS and this SAMA would require extremely costly SAMDAs containment. Design modifications to implement and would inhibit access to the containment. Screened from further consideration (Reference 16).

See SAMAs 51, 76, and 78 81 7.a. Drywell Head Advanced SAMA would provide intentional #2 - Similar See SAMA 45 N/A Flooding Reactors flooding of the upper drywell head item is SAMDAs such that if high drywell temperatures addressed occurred, the drywell head seal would under other not fail. proposed SAMAs.

82 7.b. Containment Spray Advanced This SAMA would provide additional #2 - Similar See SAMAs 32, 33, 35, 36, 52, and 54 N/A Augmentation Reactors methods of spraying the containment, item is SAMDAs addressed under other proposed SAMAs.

83 12.b. Integral Basemat Advanced This SAMA would improve #8 - ABWR This is an ABWR design issue and is not considered N/A Reactors containment and system survivability Design Issue; for retrofit due to a cost of implementation that is SAMDAs for seismic events, not practical, judged to far exceed the maximum averted cost-risk.

84 13.a. Reactor Building Advanced This SAMA provides the capability to #2 - Similar See SAMAs 32, 33, 35, 36, 52, 54, and 82 N/A Sprays Reactors use firewater sprays in the reactor item is SAMDAs building to mitigate release of fission addressed products into the Reactor Bldg. under other following an accident, proposed SAMAs.

85 14.a Flooded Rubble Bed Advanced SAMA would contain molten core #2 - Similar See SAMA 44 N/A Reactors debris dropping on to the pedestal and item is SAMDAs would allow the debris to be cooled. addressed under other proposed SAMAs.

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATIN( LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 86 14.b. Reactor Cavity Advanced SAMA would enhance debris #2 - Similar Addressed in SAMAs 47 and 57 N/A Flooder Reactors coolability, reduce core concrete item is SAMDAs interaction, and provide fission addressed product scrubbing. under other proposed SAMAs.

87 14.c. Use Basaltic Cements Advanced SAMA would minimize carbon #7 - ABWR This is a SAMA that was considered for ABWR N/A for Reactor Containment, Reactors dioxide production during core Design Issue; design. It is not practical to backfit this modification Pedestal, and Basement SAMDAs concrete interaction, not practical. into a plant that is already built and operating due to prohibitive cost.

88 Provide a core debris 15 (Intended for ice condenser plants). #1 - N/A to VCSNS is not an ice condenser plant (Reference 16). N/A control system This SAMA would prevent the direct VCSNS core debris attack of the primary Design containment steel shell by erecting a barrier between the seal table and the containment shell.

89 Add ribbing to the 15 This SAMA would reduce the risk of #2 - Similar This item is similar in nature to SAMA 55, but for N/A containment shell buckling of containment under item is protection against negative pressure. Using SAMA 55 reverse pressure loading, addressed as an upper bound and a relatively simple modification under other such as SAMA 37 as a lower bound, the cost of proposed performing structural enhancements to the reactor SAMAs. building that will significantly strengthen the containment is judged to exceed the maximum averted cost-risk for VCSNS ($1.2 million).

Improvements Related to Enhanced AC/DC Reliabfilty/Availability 90 Proceduralize alignment of 1 SAMA would reduce the SBO #1 - N/A to There is no "spare" diesel at VCSNS (Reference 16). N/A spare diesel to shutdown 3 frequency. VCSNS This SAMA requires the installation of an additional board after loss of offsite 6 Design diesel to yield credit, which is screened based on cost power and failure of the in SAMA 91.

diesel normally supplying it.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 91 Provide an additional diesel 1 SAMA would increase the reliability #5 - Cost The cost of installing an additional diesel generator has N/A generator. 3 and availability of onsite emergency would be been estimated at over $20 million in Reference 24.

6 AC power sources. more than The cost of implementation for this SAMA greatly 10 risk benefit exceeds the maximum averted cost-risk for VCSNS

($1.2 million).

92 Provide additional DC I SAMA would ensure longer battery #5 - Cost The cost of implementation for this SAMA has been N/A battery capacity. 3 capability during an SBO, reducing would be estimated to be $1.88 million in Reference 24. This 6 the frequency of long-term SBO more than exceeds the maximum averted cost-risk for VCSNS 10 sequences risk benefit ($1.2 million).

11 93 Use fuel cells instead of 10 SAMA would extend DC power #5 - Cost The cost of implementation for this SAMA has been N/A lead-acid batteries. availability in an SBO. would be estimated to be $2 million in Reference 24. This more than exceeds the maximum averted cost-risk for VCSNS risk benefit ($1.2 million).

94 Procedure to cross-tie high- I SAMA would improve core injection #2 - Similar See SAMA 95. N/A pressure core spray diesel, availability by providing a more item is reliable power supply for the high- addressed pressure core spray pumps. under other proposed SAMAs.

95 Improve 4-kV bus cross-tie 1 Enhance procedures to direct 4-kV #6 - Retain N/A 10 ability, bus cross-tie. If this procedural step already exists, investigate installation of hardware that would perform an automatic cross-tie to the opposite 4kV bus given failure of the dedicated diesel. (7.2-kV at VCSNS) 96 Incorporate an alternate I SAMA would improve DC power #3 - Already A swing battery charger is installed at VCSNS that can N/A battery charging capability 7 reliability by either cross-tying the implemented be powered by either division of Class I E AC power 8 AC busses, or installing a portable at VCSNS (Reference 16) Plant system operating procedures diesel-driven battery charger. provide the step by step instructions to align the swing charger to either DC division using power from either AC division.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement (See Notes] Disposition number 97 Increase/improve DC bus I SAMA would extend battery life in #3 - Already The DC loads that may be shed at VCSNS are limited N/A load shedding. 7 an SBO event. implemented and are provided in plant EOPs.

at VCSNS 98 Replace existing batteries 10 SAMA would improve DC power #3 - Already Reliable batteries are already installed (Reference 16). N/A with more reliable ones. reliability and thus increase available implemented In addition, the battery life was extended in an SBO to SBO recovery time. at VCSNS 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months . This upgrade replaced the C and D Type LC 15 batteries with Type L-31 cells.

99 Mod for DC Bus A SAMA would increase the reliability #1 - N/A to Loss of a single DC bus does not have a large impact N/A reliability. of AC power and injection capability. VCSNS on VCSNS (Reference 16). The DC configuration is Loss of DC Bus A causes a loss of Design different than the BWRs that this SAMA was derived main condenser, prevents transfer from.

from the main transformer to offsite power, and defeats one half of the low vessel pressure permissive for LPCI/CS injection valves.

100 Create AC power cross-tie 1 SAMA would improve AC power #1 - N/A to VCSNS is not a multi-unit site (Reference 16); N/A capability with other unit. 7 reliability. VCSNS screened from further analysis.

8 Design 101 Create a cross-tie for diesel I SAMA would increase diesel fuel oil #3 - Already The diesel fuel oil storage tanks (52,000 gallons each) N/A fuel oil. supply, and thus diesel generator implemented are already crosstied such that either tank may be used reliability. at VCSNS. as the suction source to fill either diesel's day tank (Reference 20).

102 Develop procedures to SAMA would offer a recovery path #3 - Already VCSNS operating procedures direct identification and N/A repair or replace failed 4 from a failure of the breakers that implemented correction of the causes of power failures.

kV breakers. perform transfer of 4-kV non at VCSNS. Replacement of the breaker itself is a skill of the craft emergency busses from unit station action.

service transformers, leading to loss of emergency AC power. (7.2-kV at VCSNS)

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICIE'NSE APPENDIX E - ENVIRONMENTAL REPORT__

TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 103 Emphasize steps in 1 SAMA would reduce human error #3 - Already Plant personnel are aware of the importance of N/A recovery of offsite power probability during offsite power implemented recovering offsite power in a LOOP event. In after an SBO. recovery, at VCSNS addition, EOPs direct control room operators to monitor the status of offsite power recovery actions so that the operations staff remains informed of the progress of recovery actions. Procedural enhancements related to emphasizing offsite power recovery steps in the procedure would have a negligible impact on the CDF and LERF results and are not considered further as any related changes would not be cost beneficial.

104 Develop a severe weather 1 For plants that do not already have #3 - Already Plant procedures provide instructions for severe N/A conditions procedure. 12 one, this SAMA would reduce the implemented weather.

CDF for external weather-related at VCSNS events.

105 Develop procedures for I SAMA would allow for long-term #3 - Already This function is performed automatically so that fuel N/A replenishing diesel fuel oil. diesel operation. implemented level is maintained between 300 and 450 gallons in the at VCSNS diesel day tank.

106 Install gas turbine 1 SAMA would improve onsite AC #5 - Cost The cost of installing a diverse, redundant, gas turbine N/A generator. power reliability by providing a would be generator is similar in scope to installing a new diesel redundant and diverse emergency more than generator. The cost of installing an additional diesel power system. risk benefit generator has been estimated at over $20 nullion in Reference 24. This cost of implementation for this SAMA greatly exceeds the maximum averted cost-risk for VCSNS ($1.2 million).

107 Create a backup source for 1 This SAMA would provide a #5 - Cost The VCSNS EDGs can already be cooled by the Fire N/A diesel cooling (not from redundant and diverse source of would be Service system; (Reference 16) a potential existing system). cooling for the diesel generators, more than enhancement would be to make them air cooled such which would contribute to enhanced nsk benefit that they do not rely on any service water systems for diesel reliability. cooling. The cost of implementation is estimated to be

$1.7 rmllion per diesel (Reference 24). At $3.4 million for the site, this SAMA exceeds the maximum averted cost-risk ($1.2 million).

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 108 Use fire orotection system 1 This SAMA would orovide a #3 - Already The Fire Service (FS) System is already included as an N/A as a backup source for 16 redundant and diverse source of implemented automatic backup to Service Water for DG cooling at diesel cooling. cooling for the diesel generators, at VCSNS VCSNS. The operators are directed to ensure Fire which would contribute to enhanced Service (FS) flow to the Emergency Diesel Generator diesel reliability. (EDG) and to locally monitor diesel temperatures whenever FS is supplying cooling to the EDGs (Reference 16).

109 Provide a connection to an 1 SAMA would reduce the probability #5 - Cost While the actual cost of this SAMA will vary N/A alternate source of offsite of a loss of offsite power event. would be depending on site characteristics, the cost of power. more than connecting to an alternate source of power has been risk benefit estimated at >$25 million for another U.S. PWR (Reference 24). Implementing this SAMA at VCSNS is considered to be within the same order of magnitude and exceeds the maximum averted cost-risk for the plant ($1.2 million).

110 Bury offsite power lines. I SAMA could improve offsite power #5 - Cost While the actual cost of this SAMA will vary N/A reliability, particularly during severe would be depending on site characteristics, the cost of burying weather. more than offsite power lines has been estimated at a cost risk benefit significantly greater than $25 million for another US PWR (Reference 24). Implementing this SAMA at VCSNS is considered to be within the same order of magnitude and exceeds the maximum averted cost-risk for the plant ($1.2 million).

11 Replace anchor bolts on Millstone Power Station found a high #3 - Already The VCSNS IPEEE included an assessment of the N/A diesel generator oil cooler. seismic SBO risk due to failure of the implemented plant's ability to cope with seismic events. No changes diesel oil cooler anchor bolts. For at VCSNS were identified for the EDG oil coolers, and the current plants with a similar problem, this restraints are considered to be sufficient would reduce seismic risk. Note that (Reference 17).

these were Fairbanks Morse DGs.

F-46

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 112 Change undervoltage (UV), 1 SAMA would reduce risk of 2/4 #1 - N/A to The VCSNS actuation logic is not configured in the N/A auxiliary feedwater inverter failure. VCSNS same manner as the original plant. The logic typically actuation signal (AFAS) Design trips on 2/3 or 1/2 channels and not on 2/4. Loss of block and high pressurizer two 120V AC panels, which is potentially more severe pressure actuation signals than loss of two inverters (due to multiple feeds to the to 3-out-of-4, instead of 2- panels from multiple inverters), has been included in out-of-4 logic. the PRA as an initiating event. This event has a Risk Reduction Worth and Risk Achievement Worth value of 1.000 (with respect to both CDF and LERF). These types of failures are not risk significant for VCSNS and no amount of spending to mitigate the effects of inverter failure would be cost beneficial.

113 Provide DC power to the II SAMA would increase the reliability #3 - Already The Class IE batteries already provide power to 120- N/A 120/240-volt vital AC of the 120-volt AC Bus. implemented volt AC at VCSNS (Reference 16).

system from the Class 1E at VCSNS station service battery system instead of its own battery.

114 Bypass Diesel Generator 14 SAMA would allow DGs to operate #3 - Already DG trips are automatically bypassed on emergency N/A Trips for longer, implemented start. Spurious DG trip signals are negligible at VCSNS and contributors and are not currently modeled; thus,

4 - No bypassing a spurious signal would not affect the Significant VCSNS CDF or LERF. No credit is taken for Safety Benefit bypassing legitimate trip signals.

115 2.i. 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months Station Advanced SAMA includes improved capability #2 - Similar Part of SAMA 128 N/A Blackout Injection Reactors to cope with longer SBO scenarios item is SAMDAs addressed under other proposed SAMAs.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 116 9.a. Steam-Driven Turbine Advanced This SAMA would provide a steam #5 - Cost The cost of installing a steam-driven turbine generator N/A Generator Reactors driven turbine generator that uses would be is greater in scope than installing a new DG due to the SAMDAs reactor steam and exhausts to the more than interface with the plant's steam system. The cost of suppression pool. If large enough, it risk benefit installing an additional DG has been estimated at over could provide power to additional $20 million in Reference 24. This cost of equipment. implementation for this SAMA is expected to exceed even this estimate and is considerably greater than the maximum averted cost-risk for VCSNS ($1.2 million).

117 9.b. Alternate Pump Power Advanced This SAMA would provide a small #2 - Similar VCSNS has turbine-driven feedwater pumps and N/A Source Reactors dedicated power source such as a item is replacement or addition of an independent feedwater SAMDAs dedicated diesel or gas turbine for the addressed pump would be cost-prohibitive (based on an feedwater or condensate pumps, so under other enhancement of similar scope in SAMA 179). In that they do not rely on offsite power. proposed addition, VCSNS is equipped with the Emergency SAMAs Feedwater System which consists of 2 EDG-powered and/or pumps and a turbine-driven pump (does not require

3 - Already electric power for sustained operation). None of these implemented pumps require offsite power for operation and addition at VCSNS of an independent power source for the normal Feedwater pumps will not provide significant benefit (Reference 16).

118 9.d. Additional Diesel Advanced SAMA would reduce the SBO #2 - Similar See SAMAs 90 and 91 N/A Generator Reactors frequency. item is SAMDAs addressed under other proposed SAMAs.

119 9.e. Increased Electrical Advanced SAMA would provide increased #7 - ABWR This is a SAMA that was considered for ABWR N/A Divisions Reactors reliability of AC power system Design Issue; design. It is not practical to backfit this modification SAMDAs to reduce core damage and release not practical. into a plant that is already built and operating.

frequencies.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition nqmber 120 9.f. Improved Advanced SAMA would provide increased #3 - Already VCSNS has replaced the original inverters with newly N/A Unmterruptable Power Reactors reliability of power supplies implemented designed inverters.

Supplies SAMDAs supporting front-line equipment, thus at VCSNS reducing core damage and release frequencies.

121 9 g. AC Bus Cross-Ties Advanced SAMA would provide increased #2 - Simular See SAMA 95 N/A Reactors reliability of AC power system to item is SAMDAs reduce core damage and release addressed frequencies. under other proposed SAMAs.

122 9.h. Gas Turbine Advanced SAMA would improve onsite AC #2 - Smular See SAMA 106 N/A Reactors power reliability by providing a item is SAMDAs redundant and diverse emergency addressed power system. under other proposed SAMAs.

123 9 i. Dedicated RHR Advanced SAMA would provide RHR with #5 - Cost This is estimated to cost more than $1 2 mnilion, the N/A (bunkered) Power Supply Reactors more reliable AC power. would be maximum averted cost-risk for VCSNS.

SAMDAs more than risk benefit 124 10.a. Dedicated DC Power Advanced This SAMA addresses the use of a #5 - Cost The cost of implementation for this mod is estimated at N/A Supply Reactors diverse DC power system such as an would be $3 million, which is greater than the maximum averted SAMDAs additional battery or fuel cell for the more than cost-risk for VCSNS ($1.2 million).

purpose of providing motive power to risk benefit certain components (e.g., RCIC).

125 10 b Additional Advanced This SAMA addresses the use of a #2 - Sinular Part of 124 N/A Batteries/Divisions Reactors diverse DC power system such as an item is SAMDAs additional battery or fuel cell for the addressed purpose of providing motive power to under other certain components (e.g., RCIC). proposed SAMAs.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSIE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 126 10.c. Fuel Cells Advanced SAMA would extend DC power #2 - Similar See SAMA 93 N/A Reactors availability in an SBO. item is SAMDAs addressed under other proposed SAMAs.

127 1O.d. DC Cross-ties Advanced This SAMA would improve DC #2 - Similar See SAMA 96. VCSNS is equipped with a swing DC N/A Reactors power reliability, item is charger that can be powered from either AC division.

SAMDAs addressed As the DC batteries and buses are already reliable, under other providing an AC source to the battery chargers is the proposed most beneficial way to ensure that DC power is SAMAs. available in the plant. Cross-tying DC buses for VCSNS would not significantly affect the CDF or LERF.

128 10.e. Extended Station Advanced SAMA would provide reduction in #2 - Similar See SAMAs 29, 90, 92, 93, 97, 98, 103, and 105 N/A Blackout Provisions Reactors SBO sequence frequencies. item is SAMDAs addressed under other proposed SAMAs.

129 Add an automatic bus 15 Plants are typically sensitive to the #1 - N/A to VCSNS is not a multi-unit site; screened from further N/A transfer feature to allow loss of one or more 120V vital AC VCSNS analysis (Reference 16).

automatic transfer of the buses. Manual transfers to alternate Design 120V vital AC bus from power supplies could be enhanced to the on-line unit to the transfer automatically.

standby unit Improvements in Identifying and Mitigating Containment Bypass 130 Install a redundant spray I SAMA would enhance #3 - Already VCSNS already has pressurizer spray available from 2 N/A system to depressurize the depressurization during an SGTR. implemented of 3 RCPs as well as from any of the three charging primary system during a at VCSNS pumps (Reference 16). Additional redundancy beyond steam generator tube what is present would provide minimal benefit.

rupture (SGTR).

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 131 Improve SGTR coping 1 SAMA would improve #2 - Sinular See SAMAs 133, 134, 135, 136, and 137 N/A abilities. 4 instrumentation to detect SGTR, or item is 10 additional system to scrub fission addressed product releases, under other proposed SAMAs.

132 Add other SGTR coping 4 SAMA would decrease the #2 - Similar See SAMAs 133, 134, 135, 136, and 137 N/A abilities. 9 consequences of an SGTR. item is 10 addressed under other proposed SAMAs 133 Increase secondary side 9 SAMA would elimnnate direct release #5 - Cost Based on engineering judgement, increasing the N/A pressure capacity such that 10 pathway for SGTR sequences. would be secondary side pressure capacity is not feasible as it an SGTR would not cause more than would require an entirely new secondary system. The the relief valves to lift. risk benefit cost of this modification would greatly exceed the maximum averted cost-risk for VCSNS ($1.2 million).

134 Replace steam generators 1 SAMA would lower the frequency of #3 - Already The steam generators were replaced in 1994 at N/A (SGs) with a new design. an SGTR. implemented VCSNS.

at VCSNS 135 Revise emergency 1 SAMA would reduce the #3 - Already Steam Generator Isolation is directed at VCSNS and is N/A operating procedures to consequences of an SGTR. implemented credited in the IPE (Reference 16).

direct that a faulted SG be at VCSNS isolated.

136 Direct SG flooding after a 9 SAMA would provide for improved #3 - Already Level in the steam generators is maintained above the N/A SGTR, prior to core scrubbing of SGTR releases, implemented top of the U-tubes at an indicated 30 percent damage. at VCSNS 50 percent when the containment has adverse environment.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 137 Implement a maintenance 10 SAMA would reduce the potential for #3 - Already VCSNS currently inspects 100 percent of the SG tubes N/A practice that inspects an SGTR. implemented every other outage and is committed to NET 97-06 as 100 percent of the tubes in at VCSNS part of an industry wide effort concerning steam a SG. generator maintenance. VCSNS is considering an option to extend this inspection to every third outage pending NRC approval.

138 Locate residual heat 9 SAMA would prevent intersystem #5 - Cost For an existing plant, the cost of moving an entire N/A removal (RHR) inside of LOCA (ISLOCA) out the RHR would be system is judged to greatly exceed the maximum containment. pathway. more than averted cost-risk for VCSNS ($1.2 million).

risk benefit 139 Install additional 3 SAMA would decrease ISLOCA #5 - Cost The cost of implementation for this SAMA has been N/A instrumentation for 4 frequency by installing pressure of would be estimated at $2.3 million in Reference 24. This is ISLOCAs. 6 leak monitoring instruments in more than greater than the maximum averted cost-risk for 7 between the first two pressure risk benefit VCSNS ($1.2 million).

isolation valves on low-pressure inject lines, RHR suction lines, and HPSI lines.

140 Increase frequency for I SAMA could reduce ISLOCA #3 - Already Valve testing at VCSNS is performed as directed by N/A valve leak testing. frequency. implemented Tech Spec 3.4.6.2f (Reference 19). The valves in the at VCSNS ISLOCA pathways require manual valve manipulation inside the secondary wall, which prohibits testing when the reactor is at-power. As these valves are already tested every refueling outage, further tests would require plant shutdown. This would not be cost beneficial.

141 Improve operator training SAMA would decrease ISLOCA #3 - Already The training department already performs operator N/A on ISLOCA coping. effects. implemented training on ISLOCA initiators, including specific at VCSNS flowpaths that have been identified as susceptible to ISLOCAs. Further training on mitigation of this initiating event may result in an improvement in operator response, but this would only be reflected by a minimal change in a human error probability.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING ICE,'NSE`

APPENDIX E - ENVIRONMENTAL REIPORI' ___________

TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 142 Install rehef valves in the I SAMA would relieve pressure #6 - Retain N/A 11 CC System. buildup from an RCP thermal barrier tube rupture, preventing an ISLOCA.

143 Provide leak testing of I SAMA would help reduce ISLOCA #3 - Already Leak testing of these valves is already performed at N/A valves in ISLOCA paths. frequency. At Kewaunee Nuclear implemented VCSNS (Reference 19).

Power Plant, four MOVs isolating at VCSNS RHR from the RCS were not leak tested.

144 Revise EOPs to improve 1 SAMA would ensure LOCA outside #3 - Already VCSNS EOPs direct the operators to isolate the N/A ISLOCA identification. containment could be identified as implemented significant ISLOCA paths and to evaluate the such. Salem Nuclear Power Plant had at VCSNS consequences of the isolations by monitorng RCS a scenario where an RHR ISLOCA pressure. This is considered to be an adequate could direct initial leakage back to the response to mitigate ISLOCAs.

pressurizer relief tank, giving indication that the LOCA was inside containment.

145 Ensure that all ISLOCA 1 SAMA would scrub all ISLOCA #6 - Retain N/A 12 releases are scrubbed. releases. One example is to plug drains in the break area so that the break point would be covered with water.

146 Add redundant and diverse 1 SAMA could reduce the frequency of #3 - Already The VCSNS containment isolation valves are equipped N/A limit switches to each containment isolation failure and implemented with redundant position indication through the Main containment isolation ISLOCAs through enhanced isolation at VCSNS Control Board, ESF Monitor lights, and plant valve, valve position indication, computer points. The switches supporting these indicators are also redundant. If the same limit switches were used for position indication lights and the plant computer, then a different switch was used for the ESF monitor light, or vice versa (Reference 22).

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 147 Early detection and 14 SAMA would limit the effects of #2 - Similar See SAMA 139 N/A mitigation of ISLOCA ISLOCA accidents by early detection item is and isolation. addressed under other proposed SAMAs.

148 8.e. Improved MSIV Advanced This SAMA would improve isolation #6 - Retain N/A 13 Design Reactors reliability and reduce spurious SAMDAs actuations that could be initiating events.

149 Proceduralize use of 15 Some plants may have procedures to #3 - Already Use of the pressurizer vent valves is already directed N/A pressurizer vent valves direct the use of pressurizer sprays to implemented by EOPs at VCSNS.

during steam generator reduce RCS pressure after an SGTR. at VCSNS tube rupture (SGTR) Use of the vent valves would provide sequences. a back-up method.

150 Implement a maintenance 15 This SAMA would reduce the #2 - Similar See SAMA 137 N/A practice that inspects potential for a tube rupture. item is 100 percent of the tubes in addressed an SG. under other proposed SAMAs.

151 Locate RHR inside of 15 This SAMA would prevent ISLOCA #2 - Similar See SAMA 138 N/A containment. out the RHR pathway. item is addressed under other proposed SAMAs.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 152 Install self-actuating 15 For plants that do not have these #3 - Already Only 12 reactor building penetrations have been N/A containment isolation devices, it would reduce the implemented identified which present realistic pathways for large valves frequency of isolation failure, at VCSNS releases from containment. This calculation is based on the individual penetration size as well as the availability of a pathway from the RCS or reactor building atmosphere to the outside environment (other penetrations are not considered here as releases through these pathways would have a negligible impact on the analysis). The twelve penetrations, by number, are: 101 and 402, 103 and 302, 319, 226 and 316, 227, 322, and 325, and 303 and 401.

This SAMA recommends that automatic actuating devices be installed on containment isolation valves to reduce the frequency of isolation failure. Of the twelve penetrations listed above, five already have automatic actuating devices and receive closure signals based on pertinent plant conditions.

Of the remaining seven, five are maintained closed during normal operation, and therefore have no need for isolating automatically. In fact, two of these five penetrations (226/316-loop suction isolations for RHR) previously had autoclosure capability, but the auto-close feature was removed due to several "loss of decay heat removal" events throughout the industry dunng half-pipe operations as a result of spurious closure. The remaining two penetrations (227/322 low head SI to RCS loops) are normally maintained in the open position during power operation such that injection to the RCS is automatic given an RHR pump start and decreased RCS system pressure. From a design standpoint, it is important that these valves do not close automatically on high RB pressure because they must be in the open position to mitigate a LOCA.

Based on this, VCSNS does not need to install any additional auto-closure capability in the containment isolation system.

V

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSIE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number Improvements In Reducing Internal Flooding Frequency 153 Modify swing direction of I SAMA would prevent flood #6 - Retain N/A 14 doors separating turbine propagation for a plant where internal building basement from flooding from turbine building to areas containing safeguards safeguards areas is a concern.

equipment.

154 Improve inspection of I SAMA would reduce the frequency #6 - Retain N/A 15 rubber expansion joints on of internal flooding for a plant where main condenser. internal flooding due to a failure of circulating water system expansion joints is a concern.

155 Implement internal flood I This SAMA would reduce the #6 - Retain N/A 16 prevention and mitigation consequences of internal flooding.

enhancements.

156 Implement internal I This SAMA would reduce flooding #6 - Retain N/A 17 flooding improvements risk by preventing or mitigating such as those implemented rupture in the RCP seal cooler of the at Fort Calhoun. component cooling system, ISLOCA in a shutdown cooling line, and an auxiliary feedwater (AFW) flood involving the need to remove a watertight door.

157 Shield electrical equipment Industry SAMA would decrease risk #6 - Retain N/A 18 from potential water spray. IPEEE associated with seismically induced Insights internal flooding.

158 13.c. Reduction in Reactor Advanced This SAMA reduces the Reactor #6 - Retain N/A 19 Building Flooding Reactors Building Flood Scenarios SAMDAs contribution to core damage and release.

F-56

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number Improvements Related to Feedwater/Feed and Bleed Reliability/Availability 159 Install a digital feedwater 1 This SAMA would reduce the chance #3 - Already VCSNS upgraded to digital speed control for the N/A upgrade. of a loss of main feedwater following implemented feedwater pumps in Refueling Outage 13.

a plant trip due to high pump at VCSNS discharge pressure to the SGs.

Without rapid pump speed reduction after a reactor trip, the pumps may trip on high discharge pressure.

Digital control will provide improved speed control.

160 Perform surveillances on 1 This SAMA would improve success #3 - Already Surveillance testing is already performed on the N/A manual valves used for probability for providing alternative implemented Emergency Feedwater alternate suction path isolation backup AFW pump water supply to the AFW pumps. at VCSNS valves.

suction.

161 Install manual isolation 1 This SAMA would reduce the dual #1 - N/A to VCSNS has only one turbine-driven Emergency N/A valves around AFW turbine-driven AFW pump VCSNS Feedwater Pump, the other two are motor driven turbine-driven steam maintenance unavailability. Design (Reference 16) admission valves.

162 Install accumulators for 4 This SAMA would provide control #1 - N/A to Instrument Air includes an EDG-powered compressor N/A turbine-driven AFW pump 7 air accumulators for the turbine- VCSNS that is capable of running during LOOP conditions flow control valves (CVs). driven AFW flow CVs, the motor- Design (including motor/oil cooling) (Reference 16); as driven AFW pressure CVs and SG Instrument Air supplies the FCVs for EFW at VCSNS, power-operated relief valves the benefit gained for LOOP scenarios by adding (PORVs). This would eliminate the accumulators is minimal as a reliable air source need for local manual action to align already exists. For SBO, the current accumulators last nitrogen bottles for control air during for 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , but the batteries, which are needed for a LOOP. control power, are only assumed available for 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months .

The benefit of this mod for SBO is also considered to be negligible.

163 Install separate 15 This SAMA would enhance the #1 - N/A to VCSNS is not a multi-unit site; screened from further N/A accumulators for the AFW operator's ability to operate the AFW VCSNS analysis (Reference 16).

cross-connect to the cross-connect and block valves Design opposite unit and block following loss of air support.

valves C Q Q

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 164 Install a new condensate 15 Either replace the existing tank with a #3 -Already VCSNS's Emergency Feedwater System is equipped N/A storage tank (CST) larger one, or install a back-up tank. Installed at with a connection to the Service Water System such VCSNS that the SW System can serve as the alternate pump suction source. On low CST level, an automatic swap function opens the EFW pump suction to the Service Water System and allows operation for an indefinite period of time. This capability is considered to address the intent of the SAMA.

165 Provide cooling of the 15 This SAMA would improve success #3 -Already This pump is cooled by the process fluid and does not N/A steam-driven AFW pump probability in an SBO by: (1) using Installed at require support systems for cooling (Reference 16).

in an SBO event the FP system to cool the pump, or VCSNS (2) making the pump self cooled.

166 Proceduralize local manual 15 This SAMA would lengthen AFW #3 -Already This action is directed after battery depletion, but the N/A operation of AFW when availability in an SBO. Also provides Installed at manual action is not credited in the PRA and is not control power is lost. a success path should AFW control VCSNS included in the fault tree.

power be lost in non-SBO sequences.

167 Provide portable generators 15 This SAMA would extend AFW #1 - N/A to The turbine-driven EFW pump at VCSNS is capable of N/A to be hooked into the availability in an SBO (assuming the VCSNS successful operation after battery depletion.

turbine-driven AFW, after turbine driven AFW requires DC Design battery depletion. power).

168 Add a motor train of AFW 15 For PWRs that do not have any motor #3 - Already VCSNS has I turbine-driven and two motor-driven N/A to the steam trains. trains of AFW, this would increase implemented Emergency Feedwater Pumps (Reference 16).

reliability in non-SBO sequences. at VCSNS.

169 Create ability for 15 This SAMA would be a back-up #3 - Already Service Water is connected to Emergency Feedwater N/A emergency connections of water supply for the implemented (References 16 and 25).

existing or alternate water feedwater/condensate systems. at VCSNS.

sources to feedwater/

condensate.

F-58

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 170 Use FP system as a back- 15 This SAMA would create a back-up #2 - Similar See SAMA 169 N/A up for SG inventory, to main and AFW for SG water item is supply. addressed under other proposed SAMAs.

171 Procure a portable diesel 15 This SAMA would provide a back-up #1 - N/A to VCSNS does not have an Isolation Condenser System N/A pump for isolation to the city water supply and diesel FP VCSNS (Reference 16).

condenser make-up. system pump for isolation condenser Design make-up.

172 Install an independent 15 This SAMA would allow continued #3 - Already The VCSNS CST is already capable of being re-filled N/A diesel generator for the inventory make-up to the CST during implemented using the alternate diesel fire pump. This action is CST make-up pumps an SBO. at VCSNS. directed by plant EOPs.

173 Change failure position of 15 This SAMA would allow greater #3 - Already The condenser makeup valve fails closed on loss of N/A condenser make-up valve, inventory for the AFW pumps by implemented control signal or air.

preventing CST flow diversion to the at VCSNS.

condenser if the condenser make-up valve fails open on loss of air or power.

174 Create passive secondary 15 This SAMA would reduce CDF from #5 - Cost This SAMA would require major modifications to be N/A side coolers. the loss of feedwater by providing a would be more made to the plant and the cost would far exceed the passive heat removal loop with a than risk maximum averted cost-risk for VCSNS ($1.2 million).

condenser and heat sink. benefit 175 Replace current PORVs 15 This SAMA would reduce the #6 - Retain Currently, 2 out of 3 PORVs are required with feed 20 with larger ones so only dependencies required for successful and bleed.

one is required for feed and bleed.

successful feed and bleed.

176 Install motor-dnven 1 SAMA would increase the #2 - Similar See SAMA 168 N/A feedwater pump. 11 availability of injection subsequent to item is MSIV closure, addressed under other proposed SAMAs.

C_ Q C

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 177 Use Main FW pumps for a 16 This SAMA involves a procedural #3 - Already The EOPs have been updated to direct use of the N/A Loss of Heat Sink Event change that would allow for a faster implemented turbine-driven feedwater pumps as the primary SG response to loss of the secondary heat at VCSNS. injection source.

sink. Use of only the feedwater booster pumps for injection to the SGs requires depressurization to about 350 psig; before the time this pressure is reached, conditions would be met for initiating feed and bleed.

Using the available turbine driven feedwater pumps to inject water into the SGs at a high pressure rather than using the feedwater booster alone allows injection without the time consuming depressurization.

Improvements In Core Cooling Systems 178 Provide the capability for 15 This SAMA would provide an extra #5 - Cost Based on engineering judgement and similarities to N/A diesel driven, low pressure water source in sequences in which would be more SAMA 179, the installation of a new, diesel-driven, vessel make-up. the reactor is depressurized and all than risk low pressure injection system is judged to greatly other injection is unavailable (e.g., FP benefit exceed the maximum averted cost-risk for VCSNS system). ($1.2 million).

179 Provide an additional HPSI 15 This SAMA would reduce the #5 - Cost The cost of implementation for this SAMA has been N/A pump with an independent frequency of core melt from small would be more estimated to be between $5 and $10 million diesel. LOCA and SBO sequences. than risk (Reference 24). This greatly exceeds the maximum benefit averted cost-risk for VCSNS ($1.2 million).

180 Install an independent AC 15 This SAMA would allow make-up #2 - Similar See SAMA 179 N/A HPSI system. and feed and bleed capabilities during item is an SBO. addressed under other proposed SAMAs.

181 Create the ability to 15 This SAMA would provide a back-up #6 - Retain N/A 21 manually align ECCS should automatic or remote operation recirculation. fail.

F-60

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 182 Implement an RWT make- 15 This SAMA would decrease CDF #3 - Already The annunciator response procedure for low RWST N/A up procedure. from ISLOCA scenarios, some implemented level directs the operator to refill the RWST using smaller-break LOCA scenarios, and at VCSNS. Reactor Makeup Water.

SGTR.

183 Stop low pressure safety 15 This SAMA would provide more time #1 - N/A to The sump suction valves automatically open on a low- N/A injection pumps earlier in to perform recirculation swap-over. VCSNS low level indication from the RWST such that a water medium or large LOCAs. Design supply is available. The remaining actions to isolate the RWST are manually performed by the operator, but it is judged that stopping the pumps earlier is not a beneficial method to increase the reliability of the RWST isolation actions. Additional requirements for the operator to perform pump stops and re-starts complicate the semi-automatic process that is already in place.

184 Emphasize timely swap- 15 This SAMA would reduce human #3 - Already This is extensively addressed in VCSNS operator N/A over in operator training, error probability of recirculation implemented training.

failure, at VCSNS.

185 Upgrade Chemical and 15 For a plant like the AP600 where the #3 - Already Chemical and Volume Control System already N/A Volume Control System to Chemical and Volume Control implemented includes the charging pumps which are part of the mitigate small LOCAs. System cannot mitigate a Small at VCSNS. LOCA mitigation function (Reference 16).

LOCA, an upgrade would decrease the Small LOCA CDF contribution.

186 Install an active HPSI 15 For a plant like the AP600 where an #3 - Already The charging pumps provide high pressure injection N/A system. active HPSI system does not exist, implemented for VCSNS (Reference 16).

this SAMA would add redundancy in at VCSNS.

HPSI.

187 Change "in-containment" 15 This SAMA would remove common #6 - Retain N/A 22 RWT suction from 4 check mode failure of all four injection valves to 2 check and 2 air paths.

operated valves.

C C

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 188 Renlace 2 of the 4 safety 15 This SAMA would reduce the SI #6 - Retain N/A 23 injection (SI) pumps with system common cause failure diesel-powered pumps. probability. This SAMA was intended for the System 80+, which has four trains of SI.

189 Align low pressure core 15 This SAMA would help to ensure low #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A injection or core spray to pressure ECCS can be maintained in VCSNS design (Reference 16). Screened from further analysis.

the CST on loss of loss of suppression pool cooling Design suppression pool cooling. scenarios.

190 Raise high pressure core 15 This SAMA would ensure high #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A injection/reactor core pressure core injection/reactor core VCSNS design (Reference 16). Screened from further analysis.

isolation cooling isolation cooling availability when Design backpressure trip setpoints. high suppression pool temperatures exist.

191 Improve the reliability of 15 This SAMA would reduce the #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A the automatic frequency of high pressure core VCSNS design (Reference 16). Screened from further analysis.

depressurization system. damage sequences. Design 192 Disallow automatic vessel 15 This SAMA would improve operator #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A depressurization in non control of the plant. VCSNS design (Reference 16). Screened from further analysis.

ATWS scenarios Design 193 Create automatic swap 15 This SAMA would reduce the human #6 - Retain Auto-swap to sump is already installed at VCSNS 24 over to recirculation on error contribution from recirculation (Reference 16). Additional hardware and procedure RWT depletion. failure. modifications to completely automate the swap-over (for RWST isolation) could be made.

194 Proceduralize intermittent SAMA would allow for extended #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A operation of HPCI. duration of HPCI availability. VCSNS design (Reference 16). Screened from further analysis.

Design 195 Increase available net SAMA increases the probability that #5 - Cost Requires major plant mods such as new RHR pumps, N/A positive suction head these pumps will be available to inject would be moving the RHR pumps, a new sump design, or a (NPSH) for injection coolant into the vessel by increasing more than larger RWST (only applicable for injection phase). The pumps. the available NPSH for the injection risk benefit cost of these changes would exceed the maximum pumps. averted cost-risk for VCSNS ($1.2 million).

F-62

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 196 Modify Reactor Water 1 SAMA would provide an additional #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Cleanup (RWCU) for use source of decay heat removal. VCSNS design. An "equivalent" system, the Chemical and as a decay heat removal Design Volume Control System, is already used in a heat system and proceduralize removal process at VCSNS (Reference 16).

use.

197 CRD Injection 14 SAMA would supply an additional #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A method of level restoration by using a VCSNS design (Reference 16). Screened from further analysis.

non-safety system. Design 198 Condensate Pumps for 14 SAMA to provide an additional #3 - Already VCSNS allows injection to the SGs with FW booster N/A Injection option for coolant injection when implemented pumps in combination with the condensate pumps other systems are unavailable or at VCSNS (Reference 16).

inadequate 199 Align EDG to CRD for 14 SAMA to provide power to an #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Injection additional injection source dunng loss VCSNS design (Reference 16). Screened from further analysis.

of power events Design 200 Re-open MSIVs 14 SAMA to regain the main condenser #3 - Already The VCSNS EOPs already provide for regaining the N/A as a heat sink by re-opening the implemented main condenser as a heat sink when the condenser is MSIVs. at VCSNS. available. This is accomplished by resetting the main steam isolation signals (both trains) and opening main steam isolation bypass valves (PVM-2869A/B/C).

201 Bypass RCIC Turbine 14 SAMA would allow RCIC to operate #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Exhaust Pressure Trip longer. VCSNS design (Reference 16). Screened from further analysis.

Design 202 2.a. Passive High Pressure Advanced SAMA will improve prevention of #5 - Cost The cost of this enhancement has been estimated to be N/A System Reactors core melt sequences by providing would be $1.7 million. This is greater than the maximum SAMDAs additional high pressure capability to more than averted cost-risk for VCSNS ($1.2 lmllion).

remove decay heat through an risk benefit isolation condenser type system C_ C

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 203 2.c. Suporession Pool Advanced SAMA will improve prevention of #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Jockey Pump Reactors core melt sequences by providing a VCSNS design (Reference 16). Screened from further analysis.

SAMDAs small makeup pump to provide low Design pressure decay heat removal from the RPV using the suppression pool as a source of water.

204 2.d. Improved High Advanced SAMA will improve prevention of #2 - Similar See SAMAs 179, 180, 186, 202, and 205 N/A Pressure Systems Reactors core melt sequences by improving item is SAMDAs reliability of high pressure capability addressed to remove decay heat. under other proposed SAMAs.

205 2.e. Additional Active High Advanced SAMA will improve reliability of #2 - Similar See SAMAs 179, 180, 186, and 202 N/A Pressure System Reactors high pressure decay heat removal by item is SAMDAs adding an additional system. addressed under other proposed SAMAs.

206 2.f. Improved Low Advanced SAMA would provide fire protection #6 - Retain N/A 25 Pressure System Reactors system pump(s) for use in low (Firepump) SAMDAs pressure scenarios.

207 4.b. CUW Decay Heat Advanced This SAMA provides a means for #2 - Similar See SAMA 196. The CUW system in an ABWR is N/A Removal Reactors Alternate Decay Heat Removal. item is equivalent to the RWCU system.

SAMDAs addressed under other proposed SAMAs 208 4.c. High Flow Suppression Advanced SAMA would improve suppression #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Pool Cooling Reactors pool cooling. VCSNS design (Reference 16). Screened from further analysis.

SAMDAs Design F-64

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT' TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 209 8.c. Diverse Injection Advanced SAMA will improve prevention of #2 - Similar See SAMAs 178, 179, 180, 186, 202, 205, and 206 N/A System Reactors core melt sequences by providing item is SAMDAs additional injection capabilities, addressed under other proposed SAMAs 210 Alternate Charging Pump 16 This SAMA will improve the high #3 - Already An AOP has been implemented at VCSNS to direct N/A Cooling pressure core flooding capabilities by implemented alignment of alternate cooling to the S1 pumps on loss providing the SI pumps with alternate at VCSNS of the normal supply.

gear and oil cooling sources. Given a total loss of CCW, AOPs would direct alignment of chilled water, Dermnerahzed Water, or the Fire System to the CCW System to provide cooling to the SI pumps' gear and oil box (and the other normal loads).

211 Chiller Operation Rotation 16 This SAMA will improve the high #3 - Already The operation schedule has been updated at VCSNS to N/A pressure core flooding capabilities by implemented alternate the normally running chiller trains, Also, providing the SI pumps with a more at VCSNS. chilled water provides only backup cooling for the SI reliable source of Chilled Water to the pumps. The normal cooling supply for these pumps is gear and oil coolers in the event that Component Coohng Water, which is nuclear safety CCW is lost. The VCSNS operations related.

group identified a detriment in the Chiller pumps' start probability related to prolonged "standby times."

Standby times would be reduced by rotating the operating chiller tran.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number Instrument Air/Gas Improvements 212 Modify EOPs for ability to 15 For plants that do not have diesel #1 - N/A to Two of the three IA compressors are already powered N/A align diesel power to more power to all normal and back-up air VCSNS by the ESF buses while the third is powered by BOP air compressors. compressors, this change would Design power. The compressor powered by the BOP bus and increase the reliability of IA after a one of the EDG backed compressors rely on BOP LOOP. power for supporting the air aftercoolers and for oil cooling. Only the third compressor is truly independent of BOP power (Reference 16). Supplying the compressor that is currently powered from the BOP bus with ESF power will not increase its availability due to the cooling dependencies.

213 Replace old air 15 This SAMA would improve #6 - Retain N/A 26 compressors with more reliability and increase availability of reliable ones. the IA compressors.

214 Install nitrogen bottles as a 15 This SAMA would extend operation #1 - N/A to This is primarily a BWR issue. A potential functional N/A back-up gas supply for of safety relief valves during an SBO VCSNS equivalent would be use of the PORVs in an SBO.

safety relief valves, and loss of air events (BWRs). Design The VCSNS pressurizer PORVs already have an air tank supply for operation after loss of air (Reference 16). The SG PORVs can be manually operated given an SBO (Reference 42). This is considered to address the SAMA's intent of providing the capability to operate in an SBO.

215 Allow cross connection of 11 SAMA would increase the ability to #1 - N/A to VCSNS is not a multi-unit site; screened from further N/A uninterruptable compressed 12 vent containment using the hardened VCSNS analysis (Reference 16).

air supply to opposite unit. vent. Design F-66

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 216 Allow local, manual 16 This SAMA will allow re- #3 - Already Procedures have been revised to direct this action and N/A operation of Instrument Air establishment of Instrument Air flow implemented a hand wheel has been added to the Instrument Air isolation valves, to the Pressurizer PORVs and at VCSNS isolation valve to allow manual operation of the valve subsequent alignment of feed and when remote operation has failed.

bleed for sequences in which the accumulators have been depleted and the IA isolation valves'air operators fail to cycle on an "open" signal (assuming Instrument Air is available).

ATWS Mitigation 217 Install MG set trip breakers 15 Thus SAMA would provide trip #6 - Retain N/A 27 in control room. breakers for the MG sets in the control room. In some plants, MG set breaker trip requires action to be taken outside of the control room.

Adding control capability to the control room would reduce the trip failure probability in sequences where immediate action is required (e.g.,

ATWS).

218 Add capability to remove 15 This SAMA would decrease the time #2 - Similar See SAMA 217 N/A power from the bus to insert the control rods if the reactor item is powering the control rods. trip breakers fail (during a loss of FW addressed ATWS which has a rapid pressure under other excursion). proposed SAMAs 219 Create cross-connect ability 15 This SAMA would improve #1 - N/A to This is a BWR issue; PWRs have diverse means of N/A for standby liquid control reliability for boron injection during VCSNS injecting borated water into the RCS during an ATWS trains, an ATWS event. Design including RWST water from RHR and/or the charging pumps, the ECCS accumulators, and the boric acid tank with the boric acid transfer pumps and charging pumps (Reference 16).

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase I Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 220 Create an alternate boron 15 This SAMA would improve #1 - N/A to This is a BWR issue; PWRs have diverse means of N/A injection capability (back reliability for boron injection during VCSNS injecting borated water into the RCS during an ATWS up to standby liquid an ATWS event. Design including RWST water from RHR and/or the charging control). pumps, the ECCS accumulators, and the boric acid tank with the boric acid transfer pumps and charging pumps (Reference 16).

221 Remove or allow override 15 On failure on high pressure core #1 - N/A to This is a BWR issue. PWRs do not implement the N/A of low pressure core injection and condensate, some plants VCSNS same logic for governing low pressure injection that is injection during an ATWS. direct reactor depressurization Design used in BWRs (Reference 16).

followed by 5 minutes of low pressure core injection. This SAMA would allow control of low pressure core injection immediately.

222 Install a system of relief 15 This SAMA would improve #3 - Already VCSNS meets the requirements of 10 CFR 50.62 by N/A valves that prevents any equipment availability after an implemented use of AMSAC (ATWS Mitigation System Actuation equipment damage from a ATWS. at VCSNS. Circuitry) as described in FSAR Section 7.8 pressure spike during an (Reference 23). This is considered to address the ATWS. potential for overpressurization by providing a diverse, automatic system to shut down the reactor and initiate Emergency Feedwater Flow to the SGs given ATWS conditions.

223 Create a boron injection 15 This SAMA would provide a #3 - Already VCSNS already has injection from the RWST and the N/A system to back up the redundant means to shut down the implemented boric acid tanks (Reference 16).

mechanical control rods. reactor. at VCSNS.

224 Provide an additional 15 This SAMA would improve #3 - Already VCSNS meets the requirements of 10 CFR 50.62 by N/A instrument system for instrument and control redundancy implemented use of AMSAC (ATWS Mitigation System Actuation ATWS mitigation (e.g., and reduce the ATWS frequency. at VCSNS. Circuitry) as described in FSAR Section 7.8 ATWS mitigation scram (Reference 23).

actuation circuitry).

225 Increase the safety relief SAMA addresses the risk associated #1 - N/A to This is a BWR issue related to boron dilution and is N/A valve (SRV) reseat with dilution of boron caused by the VCSNS not applicable to the VCSNS design (Reference 16).

reliability. failure of the SRVs to reseat after Design Screened from further analysis.

standby liquid control (SLC) injection.

F-68

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 226 Use control rod drive 1 SAMA provides an additional system #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A (CRD) for alternate boron to address ATWS with SLC failure or VCSNS design (Reference 16). Screened from further analysis.

injection. unavailability. Design 227 Bypass MSIV isolation in Industry SAMA will afford operators more #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A Turbine Trip ATWS IPEEE time to perform actions. The VCSNS design (Reference 16). Screened from further analysis.

scenarios Insights discharge of a substantial fraction of Design steam to the main condenser (i.e., as opposed to into the primary containment) affords the operator more time to perform actions (e.g.,

SLC injection, lower water level, depressurize RPV) than if the main condenser was unavailable, resulting in lower human error probabilities.

228 Enhance operator actions Industry SAMA will reduce human error #3 - Already ATWS training is already performed at VCSNS. N/A during ATWS IPEEE probabilities during ATWS. implemented Further training or enhancements could impact Insights at VCSNS. operator action reliability; however, the potential improvement would be difficult to quantify. No measurable change would result from implementing this change at VCSNS.

229 Guard against SLC dilution 14 SAMA to control vessel injection to #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A prevent boron loss or dilution VCSNS design (Reference 16). Screened from further analysis.

following SLC injection. Design 230 1l.a. ATWS Sized Vent Advanced This SAMA would provide the ability #2 - Similar See SAMA 39 N/A Reactors to remove reactor heat from ATWS item is SAMDAs events, addressed under other proposed SAMAs.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 231 1i.b. Improved ATWS Advanced This SAMA includes items which #2 - Similar Addressed by SAMAs 222, 223, and 224 N/A Capability Reactors reduce the contribution of ATWS to item is SAMDAs core damage and release frequencies. addressed under other proposed SAMAs.

Other Improvements 232 Provide capability for 15 Manual operation of these valves is #1 - N/A to Local operation of the PORVs is possible with a hand N/A remote operation of required in an SBO scenario. High VCSNS wheel and the system is designed for operation under secondary side relief valves area temperatures may be Design conditions such as an SBO (Reference 16).

in an SBO. encountered in this case (no Environmental conditions have been shown to be ventilation to main steam areas), and acceptable in the valve operation area at V.C. Summer remote operation could improve for SEQ scenarios (Reference 42).

success probability.

233 Create/enhance RCS 15 With either a new depressurization #5 - Cost Reference 24 estimates the cost of this SAMA at N/A depressurization ability system, or with existing PORVs, head would be between $500,000 and $4.6 million. For VCSNS, vents, and secondary side valve, RCS more than more effective depressurization capabilities would depressurization would allow earlier risk benefit require significant hardware changes and/or additions low pressure ECCS injection. Even if on top of the analysis that would be required to core damage occurs, low RCS implement the change. The cost estimate for the pressure would alleviate some modification is considered to be on the high end of the concerns about high pressure melt range provided in Reference 24. The cost of ejection. implementation for this SAMA is judged to greatly exceed the maximum averted cost-risk for VCSNS

($1.2 million).

234 Make procedural changes 15 This SAMA would reduce RCS #3 - Already RCS depressurization has been enhanced at VCSNS N/A only for the RCS pressure without the cost of a new implemented through the implementation of procedural revisions depressurization option system. at VCSNS. that move critical depressurization steps so they are performed earlier in the accident. These steps direct the operators to re-energize any pressurizer PORV block valves that were closed and racked-out to isolate a leaking PORV. This change allows the operators more time to prepare for feed and bleed before total loss of the secondary heat sink.

F-70

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 235 Defeat 100 percent load 15 This SAMA would eliminate the #4 - No The PORVs were included on the pressurizer, in part, N/A rejection capability, possibility of a stuck-open PORV significant to prevent overpressurization (Reference 16). It is after a LOOP, since PORV opening safety benefit judged that defeating this function would be more would not be needed. detrimental than beneficial. In addition, the Risk Reduction Worth of a PORV failing to re-close is 1.001 with respect to both CDF and LERF (e.g., for WARVXVC8010AFC); thus, implementing this SAMA would not result in a significant averted cost risk for VCSNS and no amount of spending would be cost beneficial for this SAMA.

236 Change control rod drive 15 Change failure position to the "fall- #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A flow CV failure position safest" position. VCSNS design (Reference 16). Screened from further analysis.

Design 237 Install secondary side 15 This SAMA would prevent secondary #6 - Retain N/A 28 guard pipes up to the side depressurization should a steam MSIVs line break occur upstream of the main steam isolation valves. This SAMA would also guard against or prevent consequential multiple SGTR following a Main Steam Line Break event.

238 Install digital large break 15 Upgrade plant instrumentation and #6 - Retain N/A 29 LOCA protection logic to improve the capability to identify symptoms/precursors of a large break LOCA (leak before break).

239 Increase seismic capacity 15 Th'is SAMA would reduce seismically #5 - Cost Seismic issues were examined in the VCSNS IPEEE N/A of the plant to a high -induced CDF. would be and the cost-effective means of reducing plant risk confidence, low probability more than were implemented as part of the program (Reference failure of twice the Safe risk benefit 17) This SAMA was considered in the System 80+

Shutdown Earthquake. original design submittal and is not applicable to an existing plant due to high cost.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 240 Enhance the reliability of 15 Inventory loss due to normal leakage #3 - Already VCSNS is equipped with a Service Water connection N/A the demineralized water can result in the failure of the CC and implemented to CC for makeup in the event that DW makeup fails.

(DW) make-up system the SRW systems. Loss of CC could at VCSNS. The Service Water System is supplied by EDG through the addition of challenge the RCP seals. Loss of powered buses and is considered to be a reliable means diesel-backed power to one SRW results in the loss of three of providing water to the CC system (Reference 16).

or both of the DW make-up EDGs and the containment air coolers pumps. (CACs).

241 Increase the reliability of 11 SAMA reduces the probability of a #6 - Retain N/A 30 safety relief valves by certain type of medium break LOCA.

adding signals to open Hatch evaluated medium LOCA them automatically. initiated by an MSIV closure transient with a failure of SRVs to open.

Reducing the likelihood of the failure for SRVs to open, subsequently reduces the occurrence of this medium LOCA.

242 Reduce DC dependency SAMA would ensure containment #1 - N/A to This is a BWR issue not applicable to the VCSNS N/A between high-pressure depressurization and high-pressure VCSNS design (Reference 16). Screened from further analysis.

injection system and ADS. injection upon a DC failure. Design 243 Increase seismic 10 SAMA would increase the #3 - Already Seismic issues were examined in the VCSNS IPEEE N/A ruggedness of plant 12 availability of necessary plant implemented and the cost-effective means of reducing plant risk components. equipment during and after seismic at VCSNS. were implemented as part of the program (Reference 17 events. 17). The cost of increasing the seismic ruggedness of all the components identified as required for safe shutdown in the IPEEE would far exceed the maximum averted cost-risk for VCSNS.

244 Enhance RPV 13 SAMA would decrease the likelihood #2 - Similar See SAMA 233 N/A depressurization capability of core damage in loss of high item is pressure coolant injection scenarios. addressed under other proposed SAMAs.

F-72

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 245 Enhance RPV 13 SAMA would decrease the likelihood #2 - Similar See SAMA 234 N/A depressurization of core damage in loss of high item is procedures pressure coolant injection scenarios, addressed under other proposed SAMAs.

246 Replace mercury switches Industry SAMA would decrease probability of #1 - N/A to Seismic issues were examined in the VCSNS IPEEE N/A on fire protection systems IPEEE spurious fire suppression system VCSNS and the cost-effective means of reducing plant risk Insights actuation given a seismic event. Design were implemented as part of the program. No mercury switches were identified in the plant walkdown (Reference 17).

247 Provide additional Industry SAMA would increase availability of #3 - Already Seismic issues were examined in the VCSNS IPEEE N/A restraints for CO 2 tanks IPEEE fire protection, given a seismic event, implemented and the cost-effective means of reducing plant nsk Insights at VCSNS. were implemented as part of the program. The compressed gas tanks identified in the plant walkdown were analyzed and screened as having sufficient anchorage (Reference 17).

248 Enhance control of Industry SAMA would minimize risk #3 - Already The IPEEE included an analysis of fire events and N/A transient combustibles IPEEE associated with important fire areas. implemented evaluated cost effective methods to reduce fire risk as Insights at VCSNS. part of the study (Reference 17). Control of transient combustibles is in place at VCSNS and no enhancements to the controls were suggested as a result of this study. This SAMA is considered to have been addressed by the IPEEE.

249 Enhance fire brigade Industry SAMA would minimize risk #3 - Already The IPEEE included an analysis of fire events and N/A awareness IPEEE associated with important fire areas. implemented evaluated cost effective methods to reduce fire risk as Insights at VCSNS. part of the study (Reference 17) Fire brigade member training has been enhanced as a result of this study.

This SAMA is considered to have been addressed by the IPEEE.

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA II) number SAMA title of SAMA Result of potential enhancement (See Notes] Disposition number 250 Upgrade fire compartment Industry SAMA would minimize risk #3 - Already The IPEEE included an analysis of fire events and N/A barriers IPEEE associated with important fire areas. implemented evaluated cost-effective methods to reduce fire risk as Insights at VCSNS. part of the study (Reference 17). No fire barrier upgrades were suggested as a result of this study. This SAMA is considered to have been addressed by the IPEEE.

251 Enhance procedures to Industry SAMA would minimize risk #3 - Already The IPEEE included an analysis of fire events and N/A allow specific operator IPEEE associated with important fire areas. implemented evaluated cost-effective methods to reduce fire risk as actions Insights at VCSNS. part of the study (Reference 17). Several procedure enhancements and training improvements were suggested as a result of the fire analysis; however, these changes were judged to have little or no impact on the HRA quantifications for the corresponding operator actions. This SAMA is considered to have been addressed by the IPEEE.

252 Develop procedures for Industry SAMA would minimize risk #4 - No Transportation and nearby facility accidents were N/A transportation and nearby IPEEE associated with transportation and significant analyzed as part of the IPEEE and it was determined facility accidents Insights nearby facility accidents. safety benefit. that these accidents did not pose a significant safety threat to VCSNS (Reference 17). The contribution from these events is considered to be low and not risk significant.

253 Enhance procedures to Industry SAMA would minimize risk #2 - Similar See SAMA 238 N/A mitigate Large LOCA IPEEE associated with Large LOCA. item is Insights addressed under other proposed SAMAs.

254 1.b. Computer Aided 16 SAMA will improve prevention of #3 - Already The Bypassed and Inoperable Status Indication (BISI) N/A Instrumentation core melt sequences by making implemented System provides graphic control room indication of operator actions more reliable. at VCSNS. critical system operability based on a variety of digital and analog inputs (Reference 16). This system was updated based on insights from the VCSNS IPE.

F-74

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 255 1.c/d. Improved Advanced SAMA will improve prevention of #3 - Already The maintenance rule has been implemented in the N/A Maintenance Reactors core melt sequences by increasing implemented industry to balance reliability and availability and in Procedures/Manuals SAMDAs reliability of important equipment. at VCSNS. doing so attempts to optimize the maintenance process.

Root cause analysis is required as part of this program and will result in procedure enhancements where they are necessary and where they will be effective in reducing maintenance errors.

256 i.e. Improved Accident Advanced SAMA will improve prevention of #2 - Similar See SAMA 254 N/A Management Reactors core melt sequences by making item is Instrumentation SAMDAs operator actions more reliable, addressed under other proposed SAMAs.

257 l.f. Remote Shutdown Advanced #3 - Already VCSNS has a Control Room Evacuation Panel that can N/A Station Reactors implemented be used to operate critical shutdown functions in the SAMDAs at VCSNS. event the Main Control Room must be evacuated.

258 l.g. Security System 16 Improvements in the site's secunty #3 - Already At the request of the VCSNS Security Department, the N/A system would decrease the potential implemented PSA group conducted a vulnerability assessment of the for successful sabotage. at VCSNS. site based on insights gained from the IPEEE to identify potential target sites. The results were provided to the Security Department for consideration 259 2.b. Improved Advanced SAMA will improve depressurization #2 - Similar Addressed in SAMAs 237, 240, and 241 N/A Depressunzation Reactors system to allow more reliable access item is SAMDAs to low pressure systems. addressed under other proposed SAMAs.

260 2 h. Safety Related Advanced SAMA will improve availability of #2 - Similar See SAMA 164 N/A Condensate Storage Tank Reactors CST following a Seismic event, item is SAMDAs addressed under other proposed SAMAs K Q C

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VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAMA title of SAMA Result of potential enhancement [See Notes] Disposition number 261 4.d. Passive Overpressure Advanced This SAMA would prevent vessel #3 - Already Safety valves are installed. N/A Relief Reactors overpressurization. implemented SAMDAs at VCSNS.

262 8.b. Improved Operating Advanced Improved operator reliability would #3 - Already The industry has improved over the last 20 years and N/A Response Reactors improve accident mitigation and implemented the development of enhanced procedures combined SAMDAs prevention, at VCSNS. with simulator training at VCSNS is judged to address this issue.

263 8.d. Operation Experience Advanced This SAMA would identify areas #3 - Already The Maintenance Rule has enforced the industry trend N/A Feedback Reactors requiring increased attention in plant implemented of tracking component performance. This issue is SAMDAs operation through review of at VCSNS. judged to be addressed by the Maintenance Rule.

equipment performance.

264 8.e. Improved SRV Design Advanced This SAMA would improve SRV #2 - Similar See SAMAs 221 and 237 N/A Reactors reliability, thus increasing the item is SAMDAs likelihood that sequences could be addressed mitigated using low pressure heat under other removal, proposed SAMAs.

265 12.a. Increased Seismic Advanced This SAMA would reduce the risk of #2 - Similar See SAMAs 111 and 239 N/A Margins Reactors core damage and release during item is SAMDAs seismic events, addressed under other proposed SAMAs.

266 13.b. System Simplification Advanced This SAMA is intended to address #2 - Similar Addressed by SAMAs 13, 107, 113, 146, 194, 237, N/A Reactors system simplification by the item is and 238 SAMDAs elimination of unnecessary interlocks, addressed automatic initiation of manual actions under other or redundancy as a means to reduce proposed overall plant risk. SAMAs.

267 Train operations crew for 15 This SAMA would improve chances #6 - Retain N/A 31 response to inadvertent of a successful response to the loss of actuation signals two 120V AC buses, which may cause inadvertent signal generation.

F-76

VIRGIL C. SUMMER STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-1 PHASE 1 SAMA (Cont'd)

Phase 1 Source Screening Phase 2 SAMA ID Reference Criteria SAMA ID number SAAIA title of SA1NIA Result of potential enhancement [See Notes] Disposition number 268 Install tornado protection 15 This SAMA would improve onsite #6 - Retain N/A 32 on gas turbine generators AC power reliability.

1 Not applicable to the VCSNS Design

2 Similar item is addressed under other proposed SAMAs.

3 Already implemented.

4 No significant safety benefit associated with the systems/items associated with this SAMA.

5 The cost of implementation is greater than the cost-risk averted for the plant change or modification.

6 Retain

7 ABWR Design Issue; not practical.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 8 Increase charging 2 SAMA would lengthen Not estimated. The charging pumps are normally cooled Screened out.

pump lube oil the time before by CCW; however, on loss of normal The cost of capacity. centrifugal charging cooling, abnormal operating procedures implementation pump failure due to lube have been developed to direct alignment would be greater oil overheating in loss of chilled water, the Demnineralized than the averted of CC sequences. Water System or the Fire Service System cost-risk to the charging pumps. This SAMA associated with would only allow for increased credit to implementing be taken for CCW recovery based on the this SAMA.

delay in charging pump failure due to oil heatup. Compared with the availability of these two alternate cooling methods, this credit is not significant. As a point of reference, the Risk Reduction Worth of common cause failure of the CCW system (event "LCC-CCF') is only 1.001 with respect to both CDF and LERF. In addition, 1) the current model does not even credit CCW recovery for charging pump cooling as the effect is negligible and 2) this SAMA does not place the plant in a stable state; without recovery of a cooling system, the charging pumps will eventually be lost.

Page F-78

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 2 10 Add redundant DC 3 SAMA would increase Not estimated. DC control power to the Service Water Screened out.

control power for reliability of PSW and Pumps is already relatively reliable at The cost of PSW pumps C and decrease core damage VCSNS. Modifications to allow implementation D. frequency due to a loss alignment of the opposite division of would be greater of SW. 125V DC to the Service Water Pumps than the averted result in minimal benefit to the plant. cost-risk The averted cost-risk associated with associated with this SAMA is $1,249. This is well implementing below the cost of implementing the this SAMA.

hardware and procedural changes Refer to required for this SAMA. Section F.5.1 for additional information.

3 12 Use existing hydro 4 SAMA would provide Between Enhancements to systems which provide Screened out.

test pump for RCP an independent seal $150,000 and cooling to RCP seals are typically high The cost of seal injection. injection source, $175,000 impact changes. The use of the existing implementation without the cost of a hydrostatic test pump for alternate seal would be greater new system. injection is estimated to yield an averted than the averted cost-risk of $103,093. The cost of cost-risk implementation for this SAMA is associated with estimated to be between $150,000 and implementing

$175,000, which exceeds the averted this SAMA.

cost-risk by greater than 45 percent. Refer to Section F.5.2 for additional information.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 4 16 Prevent centrifugal I SAMA modification Not estimated. While the flow diversion through a relief Screened out.

charging pump flow would reduce the valve failure mode is not directly Implementation diversion from the frequency of the loss of modeled in the VCSNS PRA, it is of this SAMA relief valves. RCP seal cooling if considered to be subsumed by the event would not result relief valve opening for common cause failure of charging in a significant causes a flow diversion pump seal injection (SINJ 1-CCF). The averted cost-risk large enough to prevent charging pump seal injection function for VCSNS.

RCP seal injection. (SINJ 1-CCF) has a Risk Reduction Worth of 1.000 with respect to both CDF and LERF. Thus, the averted cost-risk associated with implementing this SAMA is negligible and no amount of spending to reduce the flow diversion failure mode would be cost-beneficial.

5 22 Improved ability to SAMA would reduce Not estimated. While the Fire Service System is a Screened out.

cool the residual heat the probability of a loss potential independent system that could Implementation removal heat of decay heat removal be used to cool the RHR heat of this SAMA exchangers. by implementing exchangers, the operator action to align would not result procedure and hardware CCW to the heat exchangers and the in a significant modifications to allow action to align the Fire Service System averted cost-risk manual alignment of the to the RHR heat exchangers is for VCSNS.

fire protection system or considered to be completely dependent.

by installing a The failure to supply cooling to the RHR component cooling heat exchangers is dominated by the water cross-tie. operator action for CCW alignment, thus, an additional water source that relies on the same operator action provides no measurable benefit. The averted cost-risk for this SAMA is approximately $0.00.

Page F-8O

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 6 35 Develop an enhanced 5 SAMA would provide a Not estimated. Reference 18 indicates that the VCSNS Screened out.

drywell spray redundant source of containment would not fail due to Implementation system. water to the overpressure in postulated scenarios of this SAMA containment to control even with the loss of both Containment would not result containment pressure, Spray and Containment Cooling. In in a significant when used in addition, the Risk Reduction Worth of averted cost-risk conjunction with Containment Spray common cause for VCSNS.

containment heat failure is 1.000 with respect to CDF and removal. LERF. Thus, improving Containment Spray reliability would result in a negligible averted cost-risk.

7 40 Create/enhance 10 SAMA would reduce Not estimated. Reference 18 indicates that VCSNS Screened out.

hydrogen hydrogen detonation at containment would not fail due to Implementation recombiners with lower cost, using overpressure in any postulated scenario of this SAMA independent power 1) a new independent (including H2 detonation) even with loss would not result supply. 1anew iupply of Containment Spray and Containment in a significant Cooling. From a quantitative averted cost-risk

2) a non-safety-grade perspective, the VCSNS cost-risk for VCSNS.

portable generator associated with plant operation is driven

3) existing station by the core damage frequency; therefore, batteries reducing the LERF contribution from

4) existing AC/DC hydrogen detonation would have a independent power negligible impact on the results. In suppenesn addition, the LERF model for VCSNS does not include containment failure sequences. These sequences are judged to be small contributors to plant risk compared with ISLOCA, Steam Generator Tube Rupture, and Containment Isolation failures.

Implementation of this SAMA would not be cost beneficial.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 8 48 Create other options 1 SAMA would enhance Not estimated. The intent of this SAMA is to reduce the Screened out.

for reactor cavity debris coolability, consequences of a core melt once it has Implementation flooding. For reduce core concrete occurred. VCSNS's cost-risk is of this SAMA example, Fire Water interaction, and provide dominated by the CDF rather than the would not result could be used as an fission product LERF; thus, the impact of installing a in a significant alternate source for scrubbing. device or making a change that does not averted cost-risk containment reduce the CDF will be small. In for VCSNS.

flooding. addition, reducing the core-concrete interaction by flooding the cavity will not have a significant impact on LERF.

The timing related to containment failure due to contact with the core is generally long, categorized as a late containment failure mode, and does not significantly impact the LERF. The effects of scrubbing due to a flooded cavity are not currently credited.

9 59 Refill CST 14 SAMA would reduce Not estimated. The cost of installing a system that could Screened out.

the risk of core damage provide borated make-up water to the Implementation during events such as RWST at a flowrate sufficient to of this SAMA extended station mitigate a LOCA is judged to greatly would not result blackouts or LOCAs exceed the averted cost-risk calculated in a significant which render the for this SAMA ($23,818). Note that for averted cost-risk suppression pool PWRs this SAMA is functionally linked for VCSNS.

unavailable as an to the RWST/sump rather than the CST. Refer to injection source due to The CST already has refill capability at Section F.5.3 for heat up. VCSNS. additional information.

Page F-82

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase I Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 10 95 Improve 4-kV bus 1 Enhance procedures to $25,000 to The averted cost-risk associated with Screened out.

cross-tie ability, direct 4-kV bus cross- $50,000 implementing this SAMA is estimated to The cost of tie. If this procedural be $20,630. Development of implementation step already exists, EMERGENCY 7.2-kV AC cross-tie would be greater investigate installation procedures is not identified as a cost than the averted of hardware that would beneficial change. cost-risk perform an automatic associated with cross-tie to the opposite implementing 4-kV bus given fijilure this SAMA.

of the dedicated diesel. Refer to (7.2-kV at VCSNS) Section F.5.4 for additional information.

11 142 Install relief valves I SAMA would relieve Not estimated. The estimated averted cost-risk for Screened out.

in the CC System. pressure buildup from averting all ISLOCA contributions is The cost of an RCP thermal barrier $39,725. The cost of performing the implementation tube rupture, preventing hardware modifications to install relief would be greater an ISLOCA. valves in the CC system is judged to than the averted greatly exceed this estimate (engineering cost-risk judgement). associated with implementing this SAMA.

Refer to Section F.5.5 for additional information.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 12 145 Ensure that all SAMA would scrub all >> $39,725 The estimated averted cost-risk for Screened out.

ISLOCA releases are ISLOCA releases. One averting all ISLOCA contributions is The cost of scrubbed. example is to plug $39,725. The cost of performing the implementation drains in the break area analysis to identify all ISLOCA would be greater so that the break point pathways and to ensure that any physical than the averted would be covered with modifications implemented to mitigate cost-risk water. ISLOCAs are not detrimental to the associated with plant (e.g., cause flooding hazards) implementing combined with the cost of installation is this SAMA.

judged to greatly exceed this estimate Refer to (engineering judgement). The suggested Section F.5.5 for enhancement of plugging drain lines additional would not guarantee a release would be information.

scrubbed as the release may occur prior to the submergence of the break. Room flooding equipment and waterproofing of mitigative components would be required to make this SAMA potentially effective. Such changes would be extremely costly.

13 148 8.e. Improved MSIV Advanced This SAMA would Not estimated. The estimated averted cost-risk Screened out.

Design Reactor improve isolation associated with implementing this The cost of SAMDAs reliability and reduce SAMA is $5,788. The cost of replacing implementation spurious actuations that the MSIVs is judged to greatly exceed would be greater could be initiating this value. than the averted events. cost-risk associated with implementing this SAMA.

Refer to Section F.5.6 for additional information.

Page F-84

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 14 153 Modify swing I SAMA would prevent Not estimated. The flooding initiating events all have Screened out.

direction of doors flood propagation, for a Risk Reduction Worth values of 1.000 Implementation separating turbine plant at which internal (with respect to both CDF and LERF); of this SAMA building basement flooding from turbine thus, elimination of all flood risk would not result from areas building to safeguards included in the internal events PRA in a significant containing areas is a concern, would result in an insignificant change averted cost-risk safeguards in LERF. No amount of spending to for VCSNS.

equipment. mitigate flood events would result in a cost-beneficial solution based on the current PRA model.

15 154 Improve inspection 1 SAMA would reduce Not estimated. The flooding initiating events all have Screened out.

of rubber expansion the frequency of Risk Reduction Worth values of 1.000 Implementation joints on main internal flooding, for a (with respect to both CDF and LERF); of this SAMA condenser, plant at which internal thus, elimination of all flood risk would not result flooding (due to a included in the internal events PRA in a significant failure of circulating would result in an insignificant change averted cost-nsk water system expansion 'in LERF. No amount of spending to for VCSNS.

joints) is a concern, nutigate flood events would result in a cost-beneficial solution based on the current PRA model.

16 155 Implement internal I This SAMA would Not estimated. The flooding initiating events all have Screened out.

flood prevention and reduce the Risk Reduction Worth values of 1.000 Implementation mitigation consequences of (with respect to both CDF and LERF); of this SAMA enhancements, internal flooding, thus, elimination of all flood risk would not result included in the internal events PRA in a significant would result in an insignificant change averted cost-risk in LERF. No amount of spending to for VCSNS.

nutigate flood events would result in a cost-beneficial solution based on the current PRA model.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 17 156 Implement internal This SAMA would Not estimated. The flooding initiating events all have Screened out.

flooding reduce flooding risk by Risk Reduction Worth values of 1.000 Implementation improvements such preventing or mitigating (with respect to both CDF and LERF); of this SAMA as those implemented rupture in the RCP seal thus, elimination of all flood risk would not result at Fort Calhoun. cooler of the component included in the internal events PRA in a significant cooling system, would result in an insignificant change averted cost-risk ISLOCA in a shutdown in LERF. No amount of spending to for VCSNS.

cooling line, and an mitigate flood events would result in a auxiliary feedwater cost-beneficial solution based on the (AFW) flood involving current PRA model.

the need to remove a watertight door.

18 157 Shield electrical Industry IPEEE SAMA would decrease Not estimated. The flooding initiating events all have Screened out.

equipment from Insights risk associated with Risk Reduction Worth values of 1.000 Implementation potential water spray. seismically induced (with respect to both CDF and LERF); of this SAMA internal flooding thus, elimination of all flood risk would not result included in the internal events PRA in a significant would result in an insignificant change averted cost-risk in LERF. No amount of spending to for VCSNS.

mitigate flood events would result in a cost-beneficial solution based on the current PRA model.

19 158 13.c. Reduction in Advanced This SAMA reduces the Not estimated. The flooding initiating events all have Screened out.

Reactor Building Reactor Reactor Building Flood Risk Reduction Worth values of 1.000 Implementation Flooding SAMDAs Scenarios contribution (with respect to both CDF and LERF); of this SAMA to core damage and thus, elimination of all flood risk would not result release. included in the internal events PRA in a significant would result in an insignificant change averted cost-risk in LERF. No amount of spending to for VCSNS.

mitigate flood events would result in a cost-beneficial solution, based on the current PRA model.

Page F-86

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 20 175 Replace current 15 This SAMA would Not estimated. Installation of new pressurizer PORVs Screened out.

PORVs with larger reduce the dependencies that each have the capacity to pass the The cost of ones so only one is required for successful required feed and bleed flow alone implementation required for feed and bleed. increases the reliability of the feed and would be greater successful feed and bleed function. For VCSNS, this change than the averted bleed. is estimated to yield an averted cost-risk cost-risk of $17,766. The cost of purchasing and associated with installing new PORVs is judged to implementing greatly exceed the averted cost-risk for this SAMA.

this SAMA. Refer to Section F.5.7 for additional information.

C 7

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 21 181 Create the ability to 15 This SAMA would Not estimated VCSNS has the capability of allowing Screened out.

manually align provide a back-up for manual alignment of ECCS Implementation ECCS recirculation should automatic or recirculation with the exception of 4 of this SAMA remote operation fail. valves (1 for SI and one for CS per would not result train). Valves XVG088 1IA(B)-SI and in a significant XVG03004A(B)-SP are located within averted cost-risk the containment boundary and are not for VCSNS accessible to operators without extensive work (and unacceptable dose levels during a LOCA). Allowing access to this valve would require re-defining the containment boundary and performing physical changes to the boundary.

Currently, the VCSNS model does not credit local, manual action to operate failed power operated valve; thus, this SAMA would have no measurable impact. In addition, recirculation failure is dominated by human error (OAR 1, 2, 4, 5, C) and recovery of a failed power operated valve would not be significant relative to the HEPs for recirculation alignment. This SAMA yields a negligible averted cost-risk.

Page F-88

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 22 187 Change "in- 15 This SAMA would Not estimated The RWST suction valves impact high Screened out.

containment" RWT remove common mode and low head injection at V.C. Summer. Implementation suction from 4 check failure of all four These functions are not dominant of this SAMA valves to 2 check and injection paths. contributors to plant risk. High pressure would not result 2 air operated valves, injection is represented by the common in a significant cause failure of all high head injection averted cost-risk (HPI-CCF-ALL) and has a risk for VCSNS reduction worth of 1.002 based on CDF (which drives V.C. Summer's cost beneficial analysis). Low pressure injection is represented by two common cause failure events, one for Large and Medium LOCAs (RHR-CCF-LH IA),

and one for Small LOCAs (RHR-CCF LH8). The Risk Reduction Worth of RHR-CCF-LHIA is 1.000. RHR-CCF LH4 was not in any cutsets above the truncation limut and no importance was calculated for the event. Alteration of the RWST suction check valves would have a minimal impact on plant risk and the cost of replacing the suction valves would greatly exceed the associated averted cost-risk.

Pa( 99 C

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 23 188 Replace 2 of the 4 15 This SAMA would Not estimated High pressure SI injection is represented Screened out.

safety injection (SI) reduce the SI system by the common cause failure of all high Implementation pumps with diesel common cause failure head injection (HPI-CCF-ALL) and of this SAMA powered pumps. probability. This High Head Recirc (HPR-CCF-ALL), would not result SAMA was intended for both of which have a risk reduction in a significant the System 80+, which worth of 1.002 based on CDF (which averted cost-risk has four trains of SI. drives V.C. Summer's cost benefit for VCSNS analysis). Low pressure SI is represented by common cause of low pressure recirc and Low pressure injection. Low pressure SI injection is represented by two common cause failure events, one for Large and Medium LOCAs (RHR-CCF-LH 1A),

and one for Small LOCAs (RHR-CCF LH8). The Risk Reduction Worth of RHR-CCF-LHIA is 1.000. RHR-CCF LH4 was not in any cutsets above the truncation limit and no importance was calculated for the event. Low pressure recirc is represented by the common cause failure of the function for LLOCAs/MLOCAs (RHR-CCF-LH2) and SGTRdSLOCA scenarios (RHR CCF-LH5). The risk reduction worths of these events are 1.000 and 1.001, respectively. Alteration of the SI pumps would have a minimal impact on plant risk and the cost of replacing the SI pumps would greatly exceed the associated averted cost-risk.

Page F-90

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 24 193 Create automatic 15 This SAMA would $1,225,000 Installation of equipment that would Screened out.

swap-over to reduce the human error fully automate 1) charging pump suction The cost of recirculation on contribution from swap to the RHR Hx discharge, and 2) implementation RWT depletion recirculation failure, the RHR suction swap to the sump from would be greater the RWST given RWST depletion than the averted increases the probability of successful cost-risk recirculation initiation. The averted associated with cost-risk associated with this SAMA is implementing

$377,828. this SAMA.

Refer to Section F.5 8 for additional information.

25 206 2.f. Improved Low Advanced SAMA would provide $565,000 Installation of an additional, diesel Screened out.

Pressure System Reactor fire protection system driven fire system pump that would be The cost of (Firepump) SAMDAs pump(s) for use in low capable of providing low pressure implementation pressure scenarios, injection to the RPV from the RWST would be greater through existing RHR piping is than the averted estimated to yield an averted cost-risk of cost-risk

$117,510. Enhancement of the fire associated with protection system to provide flow to the implementing containment spray system has been this SAMA.

estimated to cost about $565,000 Refer to (Reference 24). The systems considered Section F.5.9 for in this enhancement are similar to those additional relevant to this SAMA and the scope of information.

the change is approximately the same; thus, $565,000 is judged to be an appropriate estimate for the cost of implementation for this SAMA. The averted cost-risk resulting from this enhancement is less than the cost of implementation and yields a negative net value. This SAMA is not cost beneficial.

PaQ - 91

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 26 213 Replace old air 15 This SAMA would Not estimated. The new air compressors were assumed Screened out.

compressors with improve reliability and to be more reliable by a factor of 10, The cost of more reliable ones increase availability of which is considered to be an exaggerated implementation the IA compressors. estimate of the increase in compressor would be greater reliability. However, the averted cost than the averted risk associated with this change is only cost-risk

$13,147 and is far less than the cost of associated with installing new air compressors at implementing VCSNS. this SAMA.

Refer to Section F.5. 10 for additional information.

27 217 Install MG set trip 15 This SAMA would Not estimated. For the purposes of calculating an Screened out.

breakers in control provide trip breakers for averted cost risk for this SAMA, it was The cost of room the MG sets in the conservatively assumed that installation implementation control room. In some of MG set trip breakers would remove would be greater plants, MG set breaker all ATWS contribution to CDF and than the averted trip requires action to be LERF. ATWS is a low contributor to cost-risk taken outside of the both CDF and LERF at VCSNS and this associated with control room. Adding change resulted in an averted cost-risk of implementing control capability to the $18,556. The hardware change required this SAMA.

control room would to complete this SAMA is considered to Refer to reduce the trip failure cost significantly more than the Section F.5. I1 probability in sequences associated averted cost-risk and is for additional where immediate action screened from further analysis information.

is required (e.g., (engineering judgement).

ATWS).

Page F-92

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 28 237 Install secondary side 15 This SAMA would Not estimated The Risk Reduction Worth for a Screened out.

guard pipes up to the prevent secondary side Secondary Side Break inside The cost of MSIVs depressunzation should containment is 1.032 with respect to implementation a steam line break occur CDF and 1.019 with respect to LERF. would be greater upstream of the main Assuming the larger of the two RRWs is than the averted steam isolation valves, applicable to the entire maximum cost-risk This SAMA would also averted cost risk of $1.2 million, associated with guard against or prevent elinunating ALL secondary side break implementing consequential multiple initiating events (not just those between this SAMA.

SGTR following a Main the RPV and the MSIVs) would result in Steam Line Break. an averted cost risk of $38,508. Based on engineering judgement, the cost of implementing this SAMA would far exceed this averted cost-risk; therefore, this is not a cost beneficial SAMA.

29 238 Install digital large- 15 Upgrade plant Not estimated. The Risk Reduction Worth of the Large Screened out.

break LOCA instrumentation and LOCA initiator is 1.000 (with respect to Implementation protection logic to improve the both CDF and LERF); thus, even if this of this SAMA capability to identify SAMA could prevent ALL Large would not result symptoms/precursors of LOCAs from occurring, the reduction in in a significant a large-break LOCA LERF would be insignificant. No averted cost-nsk (leak before break). amount of spending will be cost for VCSNS.

beneficial for this SAMA.

Q Pa( 93 i..

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 30 241 Increase the 1 SAMA reduces the Not estimated. The Risk Reduction Worth of the Screened out.

reliability of safety probability of a certain Medium LOCA initiator is 1.003 with Implementation relief valves by type of medium break respect to CDF and 1.002 with respect to of this SAMA adding signals to LOCA. Hatch LERF. Elimination of all Medium would not result open them evaluated medium LOCA risk corresponds to a maximum in a significant automatically. LOCA initiated by an of approximately $3,600 in averted cost averted cost-risk MSIV closure transient risk; thus, even if this SAMA could for VCSNS.

with a failure of SRVs prevent ALL Medium LOCAs from to open. Reducing the occurring (not only those caused by SRV likelihood of the failure failures), the benefit would be minimal.

for SRVs to open, The hardware addition required to subsequently reduces automatically operate the Safety Relief the occurrence of this Valves will cost more than the $3,600 medium LOCA. averted cost-risk associated with this SAMA and is therefore not cost beneficial.

31 267 Train operations 15 This SAMA would Not estimated. Inadvertent actuation signals have been Screened out.

crew for response to improve chances of a considered for VCSNS. Loss of two Implementation inadvertent actuation successful response to 120V AC panels, which would generate of this SAMA signals the loss of two 120V inadvertent actuation signals, has been would not result AC buses, which may included in the PRA as an initiating in a significant cause inadvertent signal event. This event has a Risk Reduction averted cost-risk generation. Worth and Risk Achievement Worth for VCSNS.

value of 1.000 (with respect to both CDF and LERF). These types of failures are not risk significant for VCSNS and no amount of spending to mitigate the effects of inverter failure would be cost beneficial.

Page F-94

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.4-2 (Cont'd)

PHASE 2 SAMA Phase 2 Phase 1 Source SAMA ID SAMA ID Reference of Result of potential Estimated Phase 2 number number SAMA title SAMA enhancement cost Comment disposition 32 268 Install tornado 15 This SAMA would Not estimated. While VCSNS does not have gas turbine Screened out.

protection on gas improve onsite AC generators, tornado strikes at the site Implementation turbine generators power reliability, were examined in the IPEEE (Reference of this SAMA 17). This analysis indicates that the would not result plant critical structures were designed to in a significant withstand winds of up to 360 mph. The averted cost-risk frequency that an event would occur on for VCSNS.

an individual structure with winds greater than this speed is estimated to be less than 1E-7/yr (<IE-6 for the entire site). The low initiating event frequency identifies this as a non-significant contributor to nsk at VCSNS and no amount of spending to protect against tornado strikes would be cost beneficial.

( Pa ( )5 C

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.5 Phase 2 SAMA Analysis It was possible to screen some of the remaining SAMA candidates from further analysis based on plant-specific insights regarding the risk significance of the systems that would be affected by the proposed SAMAs. The SAMAs related to non-risk-significant systems were screened from a detailed cost-benefit analysis because any change in the reliability of these systems is known to have a negligible impact on the PSA evaluation. In these cases, the estimated cost for the SAMA is listed as "Not estimated" in Table F.4-2, as any realistic monetary expenditure for the SAMA would be greater than the benefit that the SAMA would provide (essentially $0).

For each of the remaining SAMA candidates that could not be eliminated based on screening cost or PSA/application insights, a more detailed conceptual design was prepared along with a more detailed estimated cost. This information was then used to evaluate the effect of the candidates' changes upon the plant safety model.

The final cost-risk-based screening method used to determine the desirability of implementing a given SAMA is defined by the following equation:

Net Value = (baseline cost-risk of plant operation - cost-risk of plant operation with SAMA implemented) - cost of implementation For the SAMAs which yield a non-zero averted cost-risk that is obviously less than any realistic cost of implementation, no specific cost estimate is provided. The estimated cost is listed as "Not estimated" in Table F.4-2 and the SAMA is screened from further analysis. Otherwise, if the net value of the SAMA is negative, the cost of implementation is larger than the benefit associated with the SAMA and the SAMA is not considered beneficial. The baseline cost-risk of plant operation was derived using the methodology presented in Section F.3. The cost-risk of plant operation with the SAMA implemented is determined in the same manner with the exception that the PSA results reflect the application of the SAMA to the plant (the baseline input is replaced by the results of a PSA sensitivity with the SAMA change in effect).

Subsections F.5.1 - F.5.11 describe the detailed cost-benefit analysis that was used to determine how the remaining candidates were ultimately treated.

F.5.1 Phase 2 SAMA Number 2: Add Redundant DC Control Power for PSW Pumps C and D (A, B, and C Pumps for VCSNS)

Description:

This SAMA is intended to reduce the CDF by lowering the failure probability of the Service Water System. This would be accomplished by providing alternate DC control power to the pumps. A redundant power supply would allow operation of a given division of Service Water pumps when the normal supply has failed.

Such capability is beneficial when control power is not available to the "A" division and the "B" division pumps have failed for non-control power reasons. The benefit is shown Page F-96

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT in a reduction of the Loss of Service Water initiating event frequency and an improved system reliability.

Table F.5.1-1 summarizes the model changes that were made to the PSA to represent the implementation of this SAMA at VCSNS:

TABLE F.5.1-1 PHASE 2 SAMA NUMBER 2 MODEL CHANGES Gate ID and

Description:

Description of Change:

DCP-DPNIHA3: LOSS OF POWER FROM Changed DCP-DPN1HA3 to an "AND" gate.

125 VDC Added gates:

DCP-DPN1-HA3-A DCP-DPN- 1HB 3-A Deleted gates:

DCP-DPNIHA RACB-DPN1HA3C9 RACB-DPN1HA30P DCP-DPN1HA3-SBO: LOSS OF POWER Changed DCP-DPN1HA3-SBO to an "AND" gate.

FROM 125 VDC PANEL - SBO Added gates:

DCP-DPNI HA3SB O-A DCP-DPN1HB3SBO-A Deleted gates:

DCP-DPN1HA-SBO RACB-DPN1HA3CO RADP-DPN1HA3OP DCP-DPN1HA3-DR: LOSS OF POWER Changed DCP-DPN1HA3-DR to an "AND" gate.

FROM 125 VDC (DG RUN SUPPORT)

Added gates:

DCP-DPN1HA3-DR-A DCP-DPN1HB3-DR-A Deleted gates:

DCP-DPNI HA-DR RACB-DPN1HA3CO RADP-DPN1HA3OP LSW-024: NO DC ELECTRIC POWER TO Changed LSW-024 to an "AND" gate.

COMPONENT FED BY 125 VDC Added gates:

G063 G064 Deleted gates:

RACB--DPNIHACO RACB-DPN1HA3CO RADP-DPN1 HA30P Page F-97

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.1-1 (Cont'd)

PHASE 2 SAMA NUMBER 2 MODEL CHANGES Gate ID and

Description:

Description of Change:

DCP-DPN1HA3-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPNIHA3 DCP-DPN 1HA RACB-DPN1HA3CO RADP-DPN1HA3OP DCP-DPN1HB3-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPN1HB3 DCP-DPN1HB RBCB-DPN1HB3CO RBDP-DPN1HB3OP DCP-DPN1HA3SBO-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPN1HA3 - SBO DCP-DPN 1HA-SBO RACB-DPN 1HA3CO RADP-DPN1HA3OP DCP-DPN1HB3SBO-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPN1HB3 - SBO DCP-DPN1HB-SBO RBCB-DPN1HB3CO RBDP-DPNIHB3OP DCP-DPN1HA3-DR-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPN 1 HA3 (DG DCP-DPNIHA-DR RUN SUPPORT) RACB-DPN1 HA3CO RADP-DPN1HA30P DCP-DPNIHB3-DR-A: LOSS OF POWER New "OR" gate with:

FROM 125 VDC PANEL DPN1HB3 (DG DCP-DPN1 HB-DR RUN SUPPORT) RBCB-DPN1HB3CO RBDP-DPNlHB3OP G063: NO DC ELECTRIC POWER TO New "OR" gate with:

COMPONENT FED BY 125 VDC PANEL RACB-DPN1 HACO DPN1HA3 RACB-DPNIHA3CO RADP-DPN1 HA3OP G064: NO DC ELECTRIC POWER TO New "OR" gate with:

COMPONENT FED BY 125 VDC PANEL RBCB-DPNIHBCO DPNIHB3 RBCB-DPN1HB3CO RBDP-DPN1HB3OP Similar changes were made for DCP-DPN1HB3, DCP-DPN1HB3-DR, and DCP-DPN1HB3-SBO.

Page F-98

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT PSA Model Results (Phase 2 SAMA Number 2) K>

The results from this case indicate about a 0.2 percent reduction in CDF (CDFn, =5.59E 5/yr) and a 0.1 percent reduction in LERF (LERFnew=6.99E-7/yr). The results of the cost benefit analysis are shown in Table F.5.1-2.

TABLE F.5.1-2 PHASE 2 SAMA NUMBER 2 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Cost of VCSNS VCSNS Averted Cost-Risk Implementation Net Value S1,203,380 $1,202,131 $1,249 Not estimated Large Negative Value As the averted cost-risk is minimal for this SAMA, no detailed cost of implementation was derived as the cost of the hardware changes would clearly be larger than the averted cost-risk.

F.5.2 Phase 2 SAMA Number 3: Use Existing Hydro-Test Pump for RCP Seal Injection

Description:

In this sensitivity, it was assumed that the existing hydrostatic test pump ".j was modified such that it could be used for RCP seal injection. In the event that the plant's other sources of RCP seal injection and thermal barrier cooling have failed, the hydro-test pump could be used to prevent RCP seal failure and the consequential seal, LOCA.

To implement this change, a "super-event" was added to the model to represent the seal injection function of the hydro-test pump. A failure probability of 1E-3 was assigned to the event. While it may be argued that a 1E-3 failure probability overestimates the capability of this system, a lower failure probability will result in a greater benefit for the SAMA, which is conservative.

Table F.5.2-1 summarizes the changes made to the VCSNS PSA model to simulate the capability of using the station's hydro-test pump for RCP seal injection.

Page F-99

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.2-1 PHASE 2 SAMA NUMBER 3 MODEL CHANGES System: Basic Events Added Under Gate(s): Value HYDROPUMP: ALTERNATE SEAL INJECTION FROM RCPCOOL 1E-3 HYDRO PUMP PSA Model Results (Phase 2 SAMA Number 3)

The results from this case indicate about a 9 percent reduction in CDF (CDFnew=5.1 0E 5/yr) and a 5.3 percent reduction in LERF (LERFn,=6.63E-7/yr). The results of the cost benefit analysis are shown in Table F.5.2-2.

TABLE F.5.2-2 PHASE 2 SAMA NUMBER 3 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Cost of VCSNS VCSNS Averted Cost-Risk Implementation Net Value

$1,203,380 $1,100,287 $103,093 $150,000 to $175,000 -$46,907 to -$71,907 The negative net value of this SAMA candidate indicates that its implementation is not beneficial.

F.5.3 Phase 2 SAMA Number 9: Refill CST (RWST for VCSNS)

Description:

While this SAMA was developed for a BWR, the function of this enhancement is to provide a cool injection source to the RPV given that heat removal to the re-circulated volume has failed. Without a cool suction source for RHR, the pumps will fail due to seal damage or loss of NPSH. Use of the relatively cool RWST water for injection allows the RHR pumps to operate without pump cooling and without the use of the RHR heat exchangers.

For PWRs, the injection water is required to be borated. In order for RWST make-up to be viable for use in medium or large LOCA scenarios, the make-up rate to the RWST must be equivalent to the flowrate through the break. This requires an unlimited, high capacity water source, a supply of boration material to last the 24-hour mission time, and a high-speed mixer to ensure that the injection water is appropriately borated.

Page F-100

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Representing this change in the model required extensive revisions to the fault tree structure. The changes made to Loop "B" are documented in Table F.5.3-1 for demonstration purposes; the changes to Loop "A" are similar.

The RWST refill system is represented by a single lumped event, RWST-REFILL. This is considered to quantitatively account for all RWST-REFILL system failures as well as support system dependencies that are not explicitly included in the fault tree. A failure probability of 1E-2 is assigned to the RWST-REFILL event for this evaluation.

TABLE F.5.3-1 PHASE 2 SAMA NUMBER 9 MODEL CHANGES Gate ID and

Description:

Description of Change:

RHR-LPR-014: INSUFFICIENT FLOW TO Change RHR-LPR-014 to an "AND" gate.

SUCTION OF RHR PUMP B Add:

RWST-REFILL Delete:

RHR-LPR-30 RHR-LPR-014-SBO: INSUFFICIENT FLOW TO Change RHR-LPR-014-SBO to an "AND" gate.

SUCTION OF RHR PUMP B Add:

RWST-REFILL Delete:

RHR-LPR-30-SB O RHR-SUMP-B: INSUFFICIENT FLOW FROM Change RHR-SUMP-B to an "AND" gate.

CONTAINMENT SUMPS (TRAIN B) Add:

RWST-REFILL Delete:

RHR-SUMP-B-002 RHR-SUMP-B-SBO: INSUFFICIENT FLOW Change RHR-SUMP-B-SBO to an "AND" gate.

FROM CONTAINMENT SUMPS (TRAIN B) Add:

RWST-REFILL Delete:

RHR-SUMP-B-002SB RHR-LPR-005: INSUFFICIENT COOLING Add:

FLOW FROM HCV-603B "AND" gate with RWST-REFILL and IBHEXHE0005BRP (moved from under RHR-LPR 005)

RHR-REC-COOL-B: FAILURE TO COOL Add:

WATER FROM TRAIN B SUMP RWST-REFILL Page F-101

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.3-1 (Cont'd)

PHASE 2 SAMA NUMBER 9 MODEL CHANGES Gate ID and

Description:

Description of Change:

RHR-LPR-005-SBO: INSUFFICIENT Add:

COOLING FLOW FROM HCV-603B "AND" gate with RWST-REFILL and 1BHEXHE0005BRP (moved from under RHR-LPR 005-SBO)

RHR-REC-COOL-BSB: FAILURE TO COOL Add:

WATER FROM TRAIN B SUMP RWST-REFILL RHR-RECIRC-B: INSUFFICIENT FLOW Add:

FROM RHR HEAT EXCHANGER XHE-5B "AND" gate with RWST-REFILL and (RECIRC TRAIN B) 1BHEXHE0005BRP (moved from under RHR RECIRC-B)

RHR-PUMP-B-REC: B RHR PUMP XPP-31B Add:

FAILS DURING RECIRC "AND" gate with RWST-REFILL and CCWHDRB (moved from under RHR-PUMP-B-REC)

RHR-RECIRC-B-SBO: INSUFFICIENT FLOW Add:

FROM RHR HEAT EXCHANGER XHE-5B "AND" gate with RWST-REFILL and (RECIRC TRAIN B) 1BHEXHE0005BRP (moved from under RHR RECIRC-B-SBO)

RHR-PUMP-B-RECSB: B RHR PUMP XPP-31B Add:

FAILS DURING RECIRC "AND" gate with RWST-REFILL and CCWHDRB SBO (moved from under RHR-PUMP-B-RECSB)

RHR-LPR-006: B RHR PUMP FAILS XPP-31B Add:

"AND" gate with RWST-REFILL and CCWHDRB (moved from under RHR-LPR-006)

RHR-LPR-006-SBO: B RHR PUMP FAILS XPP Add:

31B "AND" gate with RWST-REFILL and CCWHDRB SBO (moved from under RHR-LPR-006-SBO)

PSA Model Results (Phase 2 SAMA Number 9)

The results from this case indicate about a 2.0 percent reduction in CDF (CDFrw=5.48E 5/yr) and a 1.7 percent reduction in LERF (LERFne=6.88E-7/yr). The results of the cost benefit analysis are shown in Table F.5.3-2.

Page F-102

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.3-2 PHASE 2 SAMA NUMBER 9 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Cost of VCSNS VCSNS Averted Cost-Risk Implementation Net Value

$1,203,380 $1,179,562 $23,818 Not Estimated Large Negative The averted cost-risk is relatively small for this SAMA with respect to the resources required for a significant plant hardware modification. No detailed cost of implementation was derived, as the cost of the hardware changes would clearly be larger than the averted cost-risk.

F.5.4 Phase 2 SAMA Number 10: Improve 7.2-kV Bus Cross-Tie Ability

Description:

Many plants have the ability to cross-tie their emergency AC buses. This is important in a loss of offsite power scenario with 1 failed EDG in combination with failure of required equipment on the remaining powered emergency bus. For example, if the Alpha diesel fails to run and the Bravo RHR system fails to operate, it would be possible to run the Alpha RHR pumps with the Bravo diesel given a successful power cross-tie. Typically, a cross-tie does not require cutting wires or other semi-permanent changes for success. The cross-tie usually requires operation of breakers from the main control room and no ex-control room action. It is difficult to credit operator actions that are not procedurally directed even if an action is physically capable of being performed.

A potential improvement would be the development of emergency procedures that contained step-by-step instructions for performing the cross-tie (given that it could be performed in a reasonable time, perhaps 30 to 45 minutes). Hardware changes that prevented the requirement to cut wires to perform the cross-tie would be a desirable enhancement to the base requirement.

Representing this change in the model required extensive revisions to the fault tree structure. The changes made to Loop "A" are documented in Table F.5.4-1 for demonstration purposes; the changes to Loop "B" are similar.

Page F-103

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.4-1 PHASE 2 SAMA NUMBER 10 MODEL CHANGES Gate or Event ID and

Description:

Description of Change:

ACP-001: LOSS OF POWER TO 7.2 KV BUS XSW1DA Delete GATE ACP-003 Add NEW GATE ACP-003-X ACP-003-X: LOSS OF ON-SITE EMERGENCY POWER TO Add 7.2 KV BUS XSW1DA BE ACP-CCF-ONSITE NEW GATE ACP-003-XTIE ACP-003-XTIE: NO POWER FROM DG A OR CROSS-TIE Add:

GATE ACP-0 11 NEW GATE BTOAXTIE ACP-003-SDX: LOSS OF ON-SITE EMERGENCY POWER Add:

TO 7.2 KV BUS XSW1DA NEW GATE ACP-003-SDX-XTIE Delete:

GATE ACP-0 11-SDX ACP-003-SDX-XTIE: NO POWER FROM DG A OR X-TIE Add:

GATE ACP-0 11 -SDX NEW GATE BTOAXTIE ATOBXTIE: NO POWER FROM DG A THROUGH X-TIE Add:

(NEW GATE)

BE OP-X-TIE (1E-2)

GATE X-TIE-BREAK GATE XTIEDGA X-TIE-BREAK: X-TIE BREAKERS FAIL Add:

NEW BE AACB----- DGTIEA (3E-3)

NEW BE AACB----- DGTIEB (3E-3)

XTIEDGA: DG A FAILS Add:

BE ACP-CCF-ONSITE GATE X-ACP-01 1-SDX GATES X-ACP-01 1-SDX AND X-ACP-027 These gates are equivalent to ACP-01 1-SDX and ACP-027 except for the replacement of the service water dependencies with undeveloped diamond events (1E-2). This was done to prevent the introduction of circular logic through the cross-tie.

Page F-104

A---------

--A-VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT PSA Model Results (Phase 2 SAMA Number 10) <Ij The results from this case indicate about a 1 percent reduction in CDF (CDF*:w=5.50E 5/yr) and a 0.9 percent reduction in LERF (LERFnew=6.93E-7/yr). The results of the cost benefit analysis are shown in Table F.5.4-2.

The negative net value for this SAMA indicates that the proposed change would not be cost beneficial.

TABLE F.5.4-2 PHASE 2 SAMA NUMBER 10 NET VALUE Base Case: Cost- Cost-Risk for Averted Cost- Cost of Risk for VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,182,349 $20,630 $25,000 to $50,000 -$4,370 to -$29,370 F.5.5 Phase 2 SAMA Number 11: Install Relief Valves in the CC System and Number 12:

Ensure all ISLOCA Releases are Scrubbed

Description:

These two SAMAs are documented together as they are both related to the reduction of risk related to ISLOCA.

The purpose of Phase 2 SAMA 11 is to decrease the ISLOCA frequency by providing overpressure protection for the CC system.

The purpose of Phase 2 SAMA 12 is to reduce the radionuclide release to the environment given that an ISLOCA has occurred.

The impact of each of these SAMAs can be bounded assuming that all ISLOCA risk is eliminated through the implementation of the SAMAs. If the averted cost-risk can be shown to be less than the cost of implementation for the bounding case, then detailed modeling techniques are not required to develop a more realistic representation of the SAMAs.

The bounding case is developed by setting the ISLOCA frequency to 0.0, as shown in Table F.5.5-1.

TABLE F.5.5-1 PHASE 2 SAMA NUMBERS 11 AND 12 MODEL CHANGES Gate or Event ID and

Description:

Description of Change:

%ISL: INTERFACING SYSTEMS LOCA Probability changed from 1.54E-6 to 0.0 INITIATING EVENT Page F- 105

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT PSA Model Results (Phase 2 SAMA Numbers 11 and 12 )

The results from this case indicate about a 0.2 percent reduction in CDF (CDFnw=5.58E 5/yr) and a 25.6 percent reduction in LERF (LERF,,=5.22E-7/yr). The results of the cost-benefit analysis are shown in Table F.5.5-2.

TABLE F.5.5-2 PHASE 2 SAMA NUMBERS 11 AND 12 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost- Cost of VCSNS VCSNS Risk Implementation Net Value S1,203,380 $1,163,655 $39,725 Not Estimated Large Negative The cost of implementation for both SAMAs 11 and 12 is considered to be much larger than the averted cost-risk. This calculation assumes that all ISLOCA risk is eliminated by implementation of these SAMAs. The actual impact of implementation would only be a fraction of what is estimated here. These SAMAs would not be cost beneficial for VCSNS given the major hardware changes required to make them viable.

F.5.6 Phase 2 SAMA Number 13: Improved MSIV Design

Description:

A better MSIV design is suggested to improve reliability of valve operation.

This is considered to impact isolation capability in accident response scenarios as well as for spurious closures that could be classified as initiating events (e.g., loss of condenser).

To capture the impact of this SAMA's implementation, the "failure to close" probability of the MSIVs is reduced by a factor of 10 as is the loss of condenser initiating event. The model changes representing these modifications are summarized in Table F.5.6- 1.

TABLE F.5.6-1 PHASE 2 SAMA NUMBER 13 MODEL CHANGES Gate or Event ID and

Description:

Description of Change:

EAAVXVM2801AFC: FAILURE TO ISOL MS Probability changed from 4.49E-3 to 4.49E-4 FLOW FROM SG A, XVM-2801A FAILS TO CLOSE EBAVXVM2801BFC: FAILURE TO ISOL MS Probability changed from 4.49E-3 to 4.49E-4 FLOW FROM SG B, XVM-2801B FAILS TO CLOSE ECAVXVM2801CFC: FAILURE TO ISOL MS Probability changed from 4.49E-3 to 4.49E-4 FLOW FROM SG C, XVM-2801C FAILS TO CLOSE Page F-106

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.6-1 PHASE 2 SAMA NUMBER 13 MODEL CHANGES (Cont'd)

Gate or Event ID and

Description:

Description of Change:

%LOC: LOSS OF CONDENSER INITIATING Probability changed from 1.03E-1 to 1.03E-2 EVENT PSA Model Results (Phase 2 SAMA Number 13)

The results from this case indicate about a 0.4 percent reduction in CDF (CDFnew=5.57E 5Iyr) and a 0.2 percent reduction in LERF (LERFjw=6.98E-7/yr). The results of the cost benefit analysis are shown in Table F.5.6-2.

TABLE F.5.6-2 PHASE 2 SAMA NUMBER 13 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost Cost of VCSNS VCSNS Risk Implementation Net Value Net Value

$1,203,380 $1,197,191 $5,788 Not Estimated Large Negative The cost of implementation for SAMA 13 is considered to be much larger than the averted cost-risk. This SAMA would not be cost beneficial for VCSNS.

F.5.7 Phase 2 SAMA Number 20: Replace Current PORVs with Larger Ones So That Only One is Required for Successful Feed and Bleed

Description:

The purpose of this SAMA is to improve feed and bleed reliability by replacing the pressurizer PORVs with new valves that are each capable of passing the required flow for feed and bleed. The size of the current PORVs limits flow so that at least two of the three are required for successful heat removal.

Table F.5.7-1 summarizes the changes made to the VCSNS PSA model to simulate the change in success criteria for feed and bleed from two of three PORVs to one of three PORVs.

<2 Page F-107

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.7-1 PHASE 2 SAMA NUMBER 21 MODEL CHANGES Gate or Event ID and

Description:

Description of Change:

PZR-002: FAILURE OF PZR PRESSURE RELIEF 2 OF 3 Changed gate from a "2/3" gate to an "AND" gate.

PORVS FAIL TO OPEN (RANDOM FAILURES)

PSA Model Results (Phase 2 SAMA Number 20)

The results from this case indicate about a 1.6 percent reduction in CDF (CDFw=5.5 1E 5/yr) and a 0.9 percent reduction in LERF (LERF,,w=6.94E-7/yr). The results of the cost benefit analysis are shown in Table F.5.7-2.

TABLE F.5.7-2 PHASE 2 SAMA NUMBER 20 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost- Cost of VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,185,614 $17,766 Not Estimated Large Negative The averted cost-risk is relatively small for this SAMA with respect to the resources required for a significant plant hardware modification. No detailed cost of implementation was derived as the cost of the hardware changes would clearly be larger than the averted cost-risk.

F.5.8 Phase 2 SAMA Number 24: Create Automatic Swap-Over to Recirculation on RWST Depletion

Description:

The purpose of this SAMA is to improve the reliability of the transition to re-circulation mode after depletion of the RWST. VCSNS has a semi-automatic swap to re-circulation mode that could be improved by automating RWST isolation (to prevent air entrainment in the RHR and charging pumps). While the sump suction valves automatically open on RWST low level (18 percent), no logic currently exists to isolate the RWST suction path or to align the charging pumps to the RHR heat exchanger discharge for high pressure recirculation. Addition of new logic to control the RWST and charging pump suction valves could be performed to address this SAMA.

Table F.5.8-1 summarizes changes made to the VCSNS PSA model to simulate full automatic swap over to re-circulation mode. The changes are characterized by reducing Page F-108

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT the operator actions for aligning re-circulation to very low values. OAR1 and OAR2 are changed to 1E-6 to represent auto closure of the RHR system's RWST suction valves KýJ (considered to represent recirculation alignment). OAR4 and OARS are also set to 1E-6 to represent auto alignment of charging pump suction to the RHR heat exchanger discharge for high pressure recirculation mode. OARC is assigned a failure probability of 1E-6. This event was used to account for the dependence between failing to align the initially running CCW train to the RHR heat exchangers given failure of the initially standby CCW train and the alignment of cold log recirculation mode. As the recirculation alignment function is automated by this SAMA, no dependence exists between the two events and the low failure probability is judged to be appropriate for this event. This SAMA assumes that CCW is auto-aligned given failure of the standby train or that all trains are aligned and started on swap. While this may overestimate the capability of the hardware responsible for performing the automatic swap, the change will conservatively show increased benefit for the SAMA. A sensitivity case (24a) has been performed assuming that OARC always fails. Due to model limitations, this implies that failure to manually align CCW to RHR fails recire mode even if there was no failure of the original RHR cooling function. This greatly overestimates the impact of the manual action to align CCW to RHR on failure of the preferred train.

TABLE F.5.8-1 PHASE 2 SAMA NUMBERS 24 AND 24A MODEL CHANGES System: Basic Events Original Value Revised Value OARh: OPERATOR FAILS TO ALIGN FOR LOW PRESSURE 1.5E-3 1E-6 CL RECIRC (RHR PUMP RUNNING)

OAR2: OPERATOR FAILS TO ALIGN FOR LOW PRESSURE 3.7E-4 IE-6 CL RECIRC (RHR PUMPS STOPPED)

OAR4: OPERATOR FAILS TO ALIGN HIGH PRESSURE CL 3.2E-2 1E-6 RECIRC (RHR PUMP STOPPED)

OARS: OPERATOR FAILS TO ALIGN HP CL RECIRC (RHR 4.7E-2 1E-6 PUMPS STOPPED, ISLOCA)

OARC: OPERATOR FAILS TO ALIGN & ESTABLISH CL 1.5E-1 IE-6 RECIRC (CONDITIONAL) (BASE CASE)

OARC: OPERATOR FAILS TO ALIGN & ESTABLISH CL 1.5E-1 1.0 RECIRC (CONDITIONAL) (SENSITIVITY CASE 23a)

PSA Model Results (Phase 2 SAMA Number 24)

The results from this case indicate about a 31 percent reduction in CDF (CDFnew=3.84E 5/yr) and a 29 percent reduction in LERF (LERFw=4.96E-7/yr). The results of the cost benefit analysis are shown in Table F.5.8-2.

K>..Y Page F-109

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.8-2 PHASE 2 SAMA NUMBER 24 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost- Cost of VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $825,552 $377,828 $1,225,000 -$847,172 PSA Model Results (Phase 2 SAMA Number 24a)

The results from this case indicate about a 9 percent reduction in CDF (CDFnew=5. 0E 5/yr) and a 16 percent reduction in LERF (LERFw=5.88E-7/yr). The results of the cost benefit analysis are shown in Table F.5.8-3.

TABLE F.5.8-3 PHASE 2 SAMA NUMBER 24a NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost- Cost of VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,085,622 $117,758 $1,225,000 -$1,107,242 The negative net values for both SAMA 24 and 24a indicate that the proposed change would not be cost beneficial.

F.5.9 Phase 2 SAMA Number 25: Improved Low Pressure System (Firepump)

Description:

Use of the Fire Service System pumps for low pressure injection in a PWR requires use of the RWST and sump as potential suction sources. Creation of an entirely new piping path is judged to be too costly for consideration; this SAMA assumes that the current RHR piping is used as the injection path for the fire pumps. The additional valves in the fire pump's path from the RWST to the RHR system are lumped into a single event (BEID = FIREPUMP, failure probability = 1E-2) representing the hardware and operator actions associated with alignment of the fire pump for injection.

Due to known limitations in the VCSNS Fire Service System's capacity, a new diesel driven pump is assumed to be required to support this modification. The cost of implementation for this SAMA is considered to be similar in scope to enhancing the fire protection system to provide flow to the containment spray system. The cost for this SAMA was estimated at $565,000 (Reference 24) and is considered to be a comparable Page F- 110

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT estimate for using the fire pump as a low pressure injection source. Table F.5.9-1 summarizes the changes made to the VCSNS PSA model to simulate modification of the 1\2 Fire Service System to support low pressure injection.

TABLE F.5.9-1 PHASE 2 SAMA NUMBER 24 MODEL CHANGES Gate or Event ID and

Description:

Description of Change:

RHR-LPI-l01 1: INSUFFICIENT FLOW THROUGH Changed RHR-LPI-011 to an "AND" gate.

RHR PUMP A AND FIREPUMP Added:

New BE FIREPUMP New "OR" gate RHR-LPI-0 11-A Deleted:

Gate GAPMXPP003 LAPS Gate RHR-PUMP-POWER-A Gate RHR-PMP-ACT-A Gate HAPMXPP0031ATM Gate CCWHDRA RHR-LPI-01 1-A: Added:

Gate GAPMXPP003 lAPS Gate RHR-PUMP-POWER-A Gate RHR-PMP-ACT-A Gate HAPMXPP0031ATM Gate CCWHDRA Similar changes made to gates:

RHR-LPI-011-SBO RHR-LPR-038 RHR-LPR-038-SBO RHR-PUMP-A-REC RHR-PUMP-A-RECSB RHR-LPI-054 RHR-LPI-054-SBO RHR-LPR-006 RHR-LPR-006-SBO RHR-PUMP-B-REC RHR-PUMP-B-RECSB PSA Model Results (Phase 2 SAMA Number 25)

The results from this case indicate about a 9.3 percent reduction in CDF (CDFnw=5.08E 5/yr) and a 13.5 percent reduction in LERF (LERFnew=6.06E-7/yr). The results of the cost-benefit analysis are shown in Table F.5.9-2.

Page F-1Il

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT TABLE F.5.9-2 PHASE 2 SAMA NUMBER 25 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost Cost of VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,085,870 $117,510 $565,000 -$447,490 The negative net value for this SAMA indicates that it would not be cost beneficial for VCSNS.

F.5.10 Phase 2 SAMA Number 26: Replace Old Air Compressors with More Reliable Ones

Description:

The purpose of this SAMA is to increase the reliability of the Instrument Air system by replacing the old air compressors with new compressors. This would affect the initiating event frequency for Loss of Instrument Air and the failure to start and run probabilities of the air compressors. For the purposes of this analysis, the new compressors are assumed to improve reliability by a factor of 10.

Table F.5.10-1 summarizes the changes made to the VCSNS PSA model to simulate the implementation of this SAMA.

TABLE F.5.10-1 PHASE 2 SAMA NUMBER 26 MODEL CHANGES System: Basic Events Original Value Revised Value

%LIAl: LOSS INSTRUMENT AIR INITIATING EVENT (DOES 1/yr 1E-1/yr NOT INCLUDE DSL SULLAIR)

XACM---XAC3AFR: COMPRESSOR XAC-3A FAILS TO RUN 4.8E-3 4.8E-4 XACMII-XAC3AFR: COMPRESSOR XAC-3A FAILS TO RUN 8.76E-1 8.76E-2 XACMI2-XAC3AFR: COMPRESSOR XAC-3A FAILS TO RUN 8.76E-1 8.76E-2 XBCM---XAC3BFR: COMPRESSOR XAC-3B FAILS TO RUN 4.8E-3 4.8E-3 XBCM---XAC3BFS: COMPRESSOR XAC-3B FAILS TO START 8E-2 8E-3 XCCM---XAC12FR: COMPRESSOR XAC-12 FAILS TO RUN 4.8E-3 4.8E-4 XCCM---XAC 12FS: COMPRESSOR XAC- 12 FAILS TO START 8E-2 8E-3 XDCM--DIESELFS: DIESEL COMPRESSOR FAILS TO START 5.7E-3 5.7E-4 XDCM--DIESELFR: DIESEL COMPRESSOR FAILS TO RUN 9.1E-4 9.1E-5 Page F- 112

VIRGIL C. SUMMIER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT PSA Model Results (Phase 2 SAMA Number 26) KU The results from this case indicate about a 1.1 percent reduction in CDF (CDFnew=5.54E 5/yr) and a 0.8 percent reduction in LERF (LERFnew=6.94E-7/yr). The results of the cost benefit analysis are shown in Table F.5.10-2.

TABLE F.5.10-2 PHASE 2 SAMA NUMBER 26 NET VALUE Base Case:

Cost-Risk for Cost-Risk for Averted Cost- Cost of VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,189,832 $13,147 Not estimated Large negative The averted cost-risk is relatively small for this SAMA with respect to the resources required for a significant plant hardware modification. No detailed cost of implementation was derived because the cost of the hardware changes would clearly be larger than the averted cost-risk.

F.5.11 Phase 2 SAMA Number 27: Install MG Set Trip Breakers in Control Room

Description:

The purpose of this SAMA is to increase the reliability of manual RCP trip in an Anticipated Transient Without SCRAM (ATWS). In the event that ATWS Mitigating System Activation Circuitry (AMSAC) logic fails to produce an RCP trip during an ATWS, the MG set breakers can be manually tripped from outside the control room. In the event of an ATWS, the time available to perform this action is typically judged to be too short to perform this ex-control room action. If the control room was equipped with the hardware to perform this action locally, it would increase the likelihood that this action could successfully be performed.

Because the ATWS contribution to the VCSNS CDF and LERF is small, this evaluation assumes that the modifications proposed by this SAMA would eliminate all ATWS risk as a bounding estimate.

Due to the nature of the PSA model, the cost-benefit analysis is performed by quantifying the ATWS sequences and then subtracting those results from the base case to represent plant operation with no ATWS contribution. This result is then used to calculate the averted cost-risk.

The ATWS contributions to CDF and LERF are 9.33E-7/yr (1.6 percent) and 6.57E-9/yr (0.94 percent), respectively. Removing the ATWS contribution from the base case yields a CDF of 5.5 1E-5/yr and a LERF of 6.93E-7/yr.

Page F-1 13

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT Table F.5.11 -1 summarizes cost benefit results for this SAMA.

TABLE F.5.11-1 PHASE 2 SAMA NUMBER 27 NET VALUE Base Case: Cost Cost-Risk for Averted Cost Cost of Risk for VCSNS VCSNS Risk Implementation Net Value

$1,203,380 $1,184,824 $18,556 Not estimated Large negative The averted cost-risk is relatively small for this SAMA with respect to the resources required for a significant plant hardware modification. No detailed cost of implementation was derived, as the cost of the hardware changes would clearly be larger than the averted cost-risk.

Page F-1 14

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.6 Phase 2 SAMA Analysis Summary The SAMA candidates that could not be eliminated from consideration by the baseline screening process or other PSA insights required the performance of a detailed analysis of the averted cost risk and SAMA implementation costs. SAMA candidates are only judged to be justified modifications if the averted cost-risk resulting from the modification is greater than the cost of implementing the SAMA. Table F.6-1 summarizes the results of the detailed analyses that were performed for the SAMA candidates requiring a detailed assessment. Two of the SAMAs analyzed were found to be cost-beneficial as defined by the methodology used in this study.

However, this evaluation should not necessarily be considered a definitive guide in determining the disposition of a plant modification that has been analyzed using other engineering methods.

These results are intended to provide information about the relative estimated risk benefit associated with a plant change or modification compared with its cost of implementation, and should be used as an aid in the decision-making process.

TABLE F.6-1

SUMMARY

OF THE DETAILED SAMA ANALYSES Averted Cost of Cost Phase 2 SAMA ID Cost-Risk Implementation Net Value Beneficial?

2 $1,249 Not Estimated Large Negative No 3 $103,093 $150,000 to $170,000 -$46,907 to -$71,907 No 9 $23,818 Not Estimated Large Negative No 10 $20,630 $25,000 to $50,000 -$4,370 to -$29,370 No 11/12 $39,725 Not Estimated Large Negative No 13 $5,788 Not Estimated Large Negative No 20 $17,766 Not Estimated Large Negative No 24 $377,828 $1,225,000 -$847,172 No 24a $117,758 $1,225,000 -$1,107,242 No 25 $117,510 $565,000 -$447,490 No 26 $13,147 Not Estimated Large Negative No 27 $18,556 Not Estimated Large Negative No Page F-1 15

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.7 Sensitivities As part of the SAMA analysis, several variables were examined to help define the influence they have on the results of the cost-benefit evaluation. These variables include the use of LERF as the sole contributor to source terms, the value chosen as the real discount rate, and other potentially influential parameters. These cases are summarized below.

F.7.1 Large Early Release Frequency This uncertainty analysis involves an investigation into the accident sequences selected for the SAMA evaluation. LERF is used as one of the measures to estimate the cost benefit of implementing potential plant modifications. The VCSNS SAMA evaluation has focused only on the accident sequences that contribute to the LERF. The current VCSNS PRA is limited to an evaluation of the LERF probability and does not provide details on the non-LERF sequences. For VCSNS, the LERF represents approximately 1.2 percent of the total CDF. The remaining sequences involve accidents that do not contribute to LERF and would be made up of a significant fraction of sequences that do not result in containment failure. For example, based on the VCSNS IPE (Reference 16),

about 19 percent of the non-LERF cases involve a potential late release of radionuclides due to containment failure. One major difference between these sequences and the LERF events is that natural removal of airborne fission products could occur over the period from vessel breach to containment failure. In fact, it has been calculated that for many PWR containments, late containment failure could occur on the order of 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months after accident initiation. This extended time would provide for removal and decay of radionuclides prior to release from containment.

To provide an assessment of the non-LERF events, two sensitivity cases were developed.

Case 1 assumes that the non-LERF releases are represented by the containment isolation failure source term from the LERF evaluation with a release time at 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months (late) and a frequency of CDF-LERF (5.59E-5/yr - 6.99E-7/yr = 4.42E-5/yr). This is considered to be a bounding estimate because it takes no credit for natural removal mechanisms in containment. Case 2 assumes the non-LERF source term is represented by the VCSNS IPE's non-LERF release source term (long term loss of containment heat removal). This release occurs at approximately 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months with a frequency of about 20 percent of the CDF (1. 12E-5/yr). This is considered to be a "more realistic" case.

Assuming that all of the non-LERF cases resulted in a Large Release at 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months greatly overestimates the impact on the SAMA evaluation. The maximum averted cost-risk was recalculated including the non-LERF accidents and found to increase by less than 10 percent. The resulting total averted cost-risk was $1.31 million. This is a modest increase and would not be expected to substantially impact the screening process. In Page F-116

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT addition, the conclusions reached in the SAMA analysis would not be changed due to this \.J uncertainty.

The second case, which is judged to better represent actual conditions, has an even smaller impact. This source term is based on long-term loss of containment heat removal and subsequent containment failure. The source term implemented in this sensitivity was chosen because it was the only case identified in the VCSNS IPE that resulted in a release that was not categorized as a LERF. The other non-LERF accidents did not result in a significant release of radionuclides to the environment. If this release is combined with the LERF releases, the maximum averted cost-risk increases by only 0.1 percent

($1,204,226). This is a negligible increase and would clearly not impact the results of the SAMA analysis.

For VCSNS, the LERF model provides results that are not substantially different from those that might be derived from a full Level 2 PRA. This is primarily due to the sparse "population and limited land development around the VCSNS site. The dominant contributors to the plant's cost-risk are driven by the CDF and are not influenced by the Level 2 or Level 3 results.

F.7.2 Real Discount Rate and Other Parameters A sensitivity study has been performed in order to identify how the conclusions of the <*.

SAMA analysis might change based on the value assigned to the real discount rate (RDR). The original RDR of 7 percent has been changed to 3 percent and the maximum averted cost-risk was re-calculated using the methodology outlined in Section F.3. The Phase 1 screening against the maximum averted cost-risk was re-examined using the revised base case to identify any SAMA candidates that could no longer be screened based on the premise that their costs of implementation exceeded all possible benefit. In addition, the Phase 2 analysis was re-performed using the 3 percent real discount rate.

Implementation of the 3 percent RDR increased the maximum averted cost-risk by 13 percent compared with the case where a 7 percent RDR was used. This relates to a maximum averted cost-risk increase from $1.20M to $1.36M. The results of the Phase 1 screening process were not affected by this small change in maximum averted cost-risk.

The costs of implementation for the SAMAs screened in Phase 1 were all greater than

$1.36 million.

The Phase 2 SAMAs are dispositioned based on PSA insights or detailed analysis. All of the PSA insights used to screen the SAMAs are still applicable given the use of the 3 percent real discount rate. The SAMA candidates screened based on these insights are considered to be addressed and are not investigated further.

Page F-1 17

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT The remaining Phase 2 SAMAs were dispositioned based on the results of a SAMA specific cost-benefit analysis. This step has been re-performed using the 3 percent real discount rate to calculate the net values for the SAMAs.

As shown in Table F.7.2-1, the determination of cost-effectiveness did not change for any of the Phase 2 SAMAs when the 3 percent real discount rate was used in lieu of 7 percent.

TABLE F.7.2-1

SUMMARY

OF REAL DISCOUNT RATE IMPACT Averted Net Value Averted Net Value Phase 2 Cost Risk (using Cost Risk (using SAMA Cost of Site (7 percent 7 percent (3 percent 3 percent Change in Cost ID Implementation RDR) RDR) RDR) RDR) Effectiveness?

Base N/A $1,203,380 N/A $1,359,468 N/A N/A 2 Not Estimated $1249 Large $1400 Large No Negative Negative 3 $150,000 to $103,093 -$46,907 to $115,300 -$34,700 to No

$170,000 $71,907 -$54,700 9 Not Estimated $23,818 Large $26,841 Large No Negative Negative 10 $25,000 to $20,630 -$4,370 to $23,076 -$1924 to No

$50,000 $29,370 $26,924 11/12 Not Estimated $39,725 Large $54,187 Large No Negative Negative 13 Not Estimated $5788 Large $6478 Large No Negative Negative 20 Not Estimated $17,766 Large $19,879 Large No Negative Negative 24 $1,225,000 $377,828 -$847,172 $426,735 -$798,265 No 24a $1,225,000 $117,758 -$1,107,242 $135,793 -$1,089,207 No 25 $565,000 $117,510 -$447,490 $134,295 -$430,705 No 26 Not Estimated $13,147 Large $14,730 Large No Negative Negative 27 Not Estimated $18,556 Large $20,752 Large No Negative Negative While the potential exists for the choice of the RDR to change the net value of borderline cases from positive to negative or from negative to positive, the impact of these types of changes on the decision making process should be small. Borderline cases require other engineering analyses as the primary decision-making tools. In conclusion, the choice of the RDR has a negligible impact on the VCSNS SAMA analysis.

Page F-1 18

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE SAPPENDIX E - ENVIRONMENTAL REPORT There are other variables in the SAMA analysis that could realistically assume a range of ,.J values. These variables include items such as evacuation timing assumptions, population and meteorology data, property values, costs of implementation, and the effectiveness of proposed SAMA modifications. These factors either have a small impact on the results or are accounted for in the method of the analysis.

For example, while the effectiveness of evacuating the relevant population during an accident is difficult to assess, there is little variance in the results based on the values assigned to the evacuation parameters. This is also true for reasonable assumptions related to the meteorology, population data, and economic worth of the surrounding area.

This sensitivity was identified as part of the evaluation performed in Section F.7.1. The Level 1 results are the dominant influence in the cost-benefit analysis for VCSNS.

The estimated costs of implementation are typically below the actual costs of implementation due to additional analysis and labor that were not considered in the conceptual stages of planning. Lower costs of implementation reduce the likelihood that SAMA candidates will be screened because they are "not cost beneficial." Thus, in the SAMA analysis, low estimates for cost of implementation are conservative as they retain SAMAs for more detailed analysis when those candidates could be screened given a more realistic estimate for the cost of implementation. The impact of the values derived for the costs of implementation is judged to be low.

Another variable is the assumed effectiveness of the SAMA enhancement. The method chosen for representing SAMA enhancements in the PSA model is to overestimate the impact of the change. For instance, if a SAMA is being considered that would improve the Containment Heat Removal capability of the plant, the enhancement is modeled as 100 percent effective such that all loss of CHR sequences are mitigated. This results in a greater cost benefit for the SAMA and a greater likelihood that the candidate will be retained. In cases where the results of this coarse method of evaluation do not provide a clear indication of the SAMA's worth, more realistic estimates are taken from similar systems already modeled in the VCSNS PSA or from other industry PSAs.

While variations in these types of parameters will produce small changes in the SAMA analysis, they do not influence the conclusions of the analysis.

Page F-1 19

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.8 Conclusions The benefits of revising the operational strategies in place at VCSNS and/or implementing hardware modifications can be evaluated without insight from a risk-based analysis. The SAMA analysis has, however, provided an enhanced understanding of the effects of the proposed changes relative to the cost of implementation and projected impact on a much larger future population. The results of the SAMA analysis indicate that none of the potential plant improvements identified are cost beneficial based on the methodology defined in this document.

No SAMAs are suggested for implementation on a cost-benefit basis.

Page F- 120

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT F.9 References

1. NUREG-1560, "Individual Plant Examination Program: Perspectives on Reactor Safety and Plant Performance," Volume 2, NRC, December 1997.

2. Letter from Mr. M. 0. Medford (Tennessee Valley Authority) to NRC Document Control Desk, dated September 1, 1992, "Watts Bar Nuclear Plant Units 1 and 2 - Generic Letter (GL) - Individual Plant Examination (IPE) for Severe Accident Vulnerabilities - Response."

3. NUREG-1437, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants,"

Volume 1, Table 5.36 Listing of SAMDAs considered for the Comanche Peak Steam Electric Station, NRC, May 1996.

4. Letter from Mr. D. E. Nunn (Tennessee Valley Authority) to NRC Document Control Desk, dated October 7, 1994, "Watts Bar Nuclear Plant (WBN) Units 1 and 2 - Severe Accident Mitigation Design Alternatives (SAMDA) - Response to Request for Additional Information (RAI)."

5. NUREG-1437, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants,"

Volume 1, Table 5.35, Listing of SAMDAs considered for the Limerick Generating Station, NRC, May 1996.

6. Letter from Mr. W. J. Museler (Tennessee Valley Authority) to NRC Document Control Desk, dated October 7, 1994, "Watts Bar Nuclear Plant (WBN) Units 1 and 2 - Severe Accident Mitigation Design Alternatives (SAMDA)."

7. NUREG-0498, "Final Environmental Statement related to the operation of Watts Bar Nuclear Plant, Units 1 and 2," Supplement No. 1, NRC, April 1995.

8. Letter from Mr. D. E. Nunn (Tennessee Valley Authority) to NRC Document Control Desk, dated June 30, 1994. "Watts Bar Nuclear Plant (WBN) Unit 1 and 2 - Severe Accident Mitigation Design Alternatives (SAMDAs) Evaluation from Updated Individual Plant Evaluation (IPE)."

9. Letter from N. J. Liparulo (Westinghouse Electric Corporation) to NRC Document Control Desk, dated December 15, 1992, "Submittal of Material Pertinent to the AP600 Design Certification Review."

10. NUREG-1462, "Final Safety Evaluation Report Related to the Certification of the System 80+

Design," NRC, August 1994.

11. Letter from Georgia Power Company to U.S. Nuclear Regulatory Commission.

Subject:

Plant Hatch

- Units 1 and 2, Individual Plant Examination Submittal, December 11, 1992.

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VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT

12. Letter from Georgia Power Company to U.S. Nuclear Regulatory Commission.

Subject:

Edwin I.

Hatch Nuclear Plant, Response to Generic Letter 88-20, Supplement 4. Submitting the Edwin I Hatch Individual Plant Examination for External Events (IPEEE). January 26, 1996.

13. Generic Letter 88-20, Supplement 1. Initiation of the Individual Plant Examination for Severe Accident Vulnerabilities - 10CFR50.54(f), United States Nuclear Regulatory Commission, August 29, 1989.

14. Generic Letter 88-20, Supplement 2. Accident Management Strategies for Consideration in the Individual Plant Examination Process - 10CFR50.54(f), United States Nuclear Regulatory Commission, April 4, 1990.

15. NUREG-1437, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants,"

Supplement 1, Calvert Cliffs Nuclear Power Plant. U.S. Nuclear Regulatory Commission, Washington, D.C., February 1999.

16. Letter from John L. Skolds (SCE&G) to NRC Document Control Desk, dated June 18, 1993. "Virgil C. Summer Nuclear Station (VCSNS) Docket No. 50-395 Operating License No. NPF-12 Transmittal of IPE Report; Generic Letter 88-20 (LTR 880020)."

17. Letter from Gary J. Taylor (SCE&G) to NRC Document Control Desk, dated June 30, 1995. "Virgil C. Summer Nuclear Station Docket No. 50-395 Operating License No. NPF-12 Transmittal of IPEEE Report; Generic Letter 88-20, Supplement 4 (LTR 880020-4)".

18. VCSNS Source Term Notebook for Individual Plant Examination, Revision 1, June 1993.

19. VCSNS Technical Specifications, Sections 3.4.6.2, "Reactor Coolant System Operational Leakage,"

Amendment 151, Dated 7/30/01.

20. VCSNS Drawing D-302-35 1, "Diesel Generator Fuel Oil," Rev. 10, 12/18/00.

21. VCSNS Drawings D-302-611 "Component Cooling Water," (Rev. 32), 612 "Component Cooling System Inside Reactor Building," (Rev. 23), 613 (Rev. 19) "Component Cooling System Non Essential Equipment Cooling," and 614 "Component Cooling System to NSSS Pumps" (Rev. 13).

22. South Carolina Electric & Gas Company Vigil C. Summer Nuclear Station, Design Basis Document, Equipment Qualification/Regulatory Guide 1.97 (EQ/RG1.97) Equipment (EQ) Revision 5.

23. VCSNS Final Safety Analysis Report, Amendment 97-01, Section 7.8, ATWS Mitigation System Actuation Circuitry, August 1997.

24. Calvert Cliffs Nuclear Power Plant License Renewal Application, Applicant's Environmental Report (Volume 3), Appendix F, "Severe Accident Mitigation Alternatives Analysis," April 1998.

Page F-122

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT

25. VCSNS Drawing D-302-222, "Service Water Cooling," Rev. 44.

26. VCSNS Drawing D-302-61 1, "Component Cooling," Rev. 32.

27. Not used.

28. C. Payne, R. J. Breeding, H-N Jow, J. C. Helton, L. N. Smith, A. W. Shiver, "Evaluation of Severe Accident Risks: Peach Bottom, Unit 2," NUREG/CR-4551, SAND86-1309, Volume 4, Parts 1 and 2, Sandia National Laboratories, December 1990.

29. Not used.

30. U.S. Nuclear Regulatory Commission, "Regulatory Analysis Technical Evaluation Handbook,"

NUREG/BR-0184, 1997.

31. Southern Nuclear Operating Company, Edwin I. Hatch Nuclear Plant Application for License Renewal, Applicant's Environmental Report, Appendix D, Attachment F, "Severe Accident Mitigation Alternatives," February 2000.

32. Letter from Gary J. Taylor (SCE&G) to NRC Document Control Desk, dated January 28, 1999, "Virgil C. Summer Nuclear Station Docket No. 50-395 Operating License No. NPF-12 Request For Additional Information Regarding Generic Letter 88-20 TAC No. MB3680".

33. NUREG-1437, "Generic Environmental Impact Statement for License Renewal of Nuclear Plants, Oconee Nuclear Station," Supplement 2, U.S. Nuclear Regulatory Commission, Washington, D.C.,

December 1999.

34. Chanin, D. and Young, M., Code Manual for MACCS2: Volume 1, User's Guide, SAND 97-0594, 1997.

35. NUREG-1150, "Severe Accident Risks: An Assessment for Five U.S. Nuclear Power Plants," U.S.

Nuclear Regulatory Commission, Washington, D.C., June 1989.

36. VCSNS Emergency Preparedness Plan Revision 45 March 28, 2002.

37. NUREG/CR-6525, "SECPOP90: Sector Population, Land Fraction, and Economic Estimation Program," U.S. Nuclear Regulatory Commission, Washington, D.C., September 1997.

38. U.S. Census Bureau, Census 2000 Redistricting Data (P.L.94-171) Summary File and 1990 Census.

Table 1 - Counties in Alphabetic Sort within State, 1990 and 2000 Population, Numeric and Percent Change: 1990 to 2000. Internet Release date: April 2, 2001. Available online at:

http://www.census.gov/population/cen2000/phc-t4/tabo1.xls Page F-123

VIRGIL C. SUMMER NUCLEAR STATION APPLICATION FOR RENEWED OPERATING LICENSE APPENDIX E - ENVIRONMENTAL REPORT

39. U.S. Department of Agriculture, "1997 Census of Agriculture," National Agricultural Statistics Service, 1998.

40. U.S. Department of Agriculture, "Usual Planting and Harvesting Dates for Crops in South Carolina,"

National Agricultural Statistics Service, http://www.nass.usda.gov/sc/pltdnum.htm

41. Not used.

42. U.S. Nuclear Regulatory Commission Letter to John L. Skolds (SCE&GC), "Supplemental Safety Evaluation Regarding Station Blackout, Virgil C. Summer Nuclear Station, Unit No. 1," Docket No.

50-395, June 1, 1992.

43. John E. Till and H. Robert Meyer, Radiological Assessment, A Textbook on Environmental Dose Analysis, NUREG/CR-3332, ORNL-5968, p.2-23, September 1983, prepared for USNRC, Washington, D.C.

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