ML11285A481
| ML11285A481 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/19/2011 |
| From: | - No Known Affiliation |
| To: | Division of Operating Reactor Licensing |
| References | |
| Download: ML11285A481 (142) | |
Text
1 WBN2Public Resource From:
Boyd, Desiree L [dlboyd@tva.gov]
Sent:
Monday, September 19, 2011 8:27 AM To:
Epperson, Dan; Poole, Justin; Raghavan, Rags; Milano, Patrick; Campbell, Stephen Cc:
Arent, Gordon; Hamill, Carol L; Boyd, Desiree L; Crouch, William D
Subject:
TVA letter to NRC_09-16-11_Revided SAMDA Response Attachments:
09-16-11_Revided SAMDA Response_Final.pdf Please see attached TVA letter that was sent to the NRC.
Thank You,
~*~*~*~*~*~*~*~*~*~*~*~
Désireé L. Boyd WBN 2 Licensing Support Sun Technical Services dlboyd@tva.gov 423-365-8764
Hearing Identifier:
Watts_Bar_2_Operating_LA_Public Email Number:
526 Mail Envelope Properties (7AB41F650F76BD44B5BCAB7C0CCABFAF232E99A4)
Subject:
TVA letter to NRC_09-16-11_Revided SAMDA Response Sent Date:
9/19/2011 8:27:27 AM Received Date:
9/19/2011 8:27:38 AM From:
Boyd, Desiree L Created By:
dlboyd@tva.gov Recipients:
"Arent, Gordon" <garent@tva.gov>
Tracking Status: None "Hamill, Carol L" <clhamill@tva.gov>
Tracking Status: None "Boyd, Desiree L" <dlboyd@tva.gov>
Tracking Status: None "Crouch, William D" <wdcrouch@tva.gov>
Tracking Status: None "Epperson, Dan" <Dan.Epperson@nrc.gov>
Tracking Status: None "Poole, Justin" <Justin.Poole@nrc.gov>
Tracking Status: None "Raghavan, Rags" <Rags.Raghavan@nrc.gov>
Tracking Status: None "Milano, Patrick" <Patrick.Milano@nrc.gov>
Tracking Status: None "Campbell, Stephen" <Stephen.Campbell@nrc.gov>
Tracking Status: None Post Office:
TVANUCXVS2.main.tva.gov Files Size Date & Time MESSAGE 285 9/19/2011 8:27:38 AM 09-16-11_Revided SAMDA Response_Final.pdf 729539 Options Priority:
Standard Return Notification:
No Reply Requested:
No Sensitivity:
Normal Expiration Date:
Recipients Received:
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 September 16, 2011 10 CFR 50.4 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Docket No. 50-391
Subject:
WATTS BAR NUCLEAR PLANT (WBN) - UNIT 2 - REVISED SEVERE ACCIDENT MANAGEMENT DESIGN ALTERNATIVE REVIEW (SAMDA) RESPONSE (TAC NO. MD8203)
References:
- 1. TVA to NRC letter dated June 17, 2011, Watts Bar Nuclear Plant, Unit 2 - Response To Request For Additional Information Regarding Severe Accident Management Design Alternative Review (SAMDA) (TAC NO. MD8203)
- 2. TVA to NRC letter dated May 25, 2011, Watts Bar Nuclear Plant (WBN) - Unit 2 - Response to Request for Additional Information Regarding Severe Accident Management Design Alternative Review (TAC No. MD8203)
- 3. TVA to NRC letter dated January 31, 2011, Watts Bar Nuclear Plant (WBN) - Unit 2 - Response to Request for Additional Information Regarding Severe Accident Management Alternative Review (TAC NO. MD8203)
- 4. TVA to NRC letter dated November 1, 2010, Watts Bar Nuclear Plant (WBN) Unit 2 - Severe Accident Management Alternatives Using Latest Computer Aided Fault Tree Analysis Model -
Additional Information (TAC MD8203)
The purpose of this letter is to provide revisions to data results and conclusions contained within References 1, 2, 3, and 4 regarding the Severe Accident Management Design Alternatives (SAMDA) analysis. These revisions stem from a misinterpretation of the consequence model output for total person-rem for each of several assessed release categories and from two less significant source term errors.
The Enclosure summarizes the changes, the impacts on SAMA evaluations, and the responses to RAIs. Specifically, the following tables are revised:
U.S. Nuclear Regulatory Commission Page 3 September 16, 2011 bcc (Enclosure):
Stephen Campbell U.S. Nuclear Regulatory Commission MS 08H4A One White Flint North 11555 Rockville Pike Rockville, MA 20852-2738 Charles Casto, Deputy Regional Administrator for Construction U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., N.E., Suite 1200 Atlanta, GA 30303-1257
Revised Results/Conclusion to Previous Watts Bar Unit 2 SAMDA Responses
1 ENCLOSURE 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION Following the response to RAIs up to and including the TVA submittal of June 27, 2011, an error was discovered by NRC and confirmed by ABS in the interpretation of the MACCs output for total person-rem for each of the assessed release categories. This error underestimated the total person-rem computed, thereby requiring a reanalysis of the identified SAMAs with the corrected person-rem values. The total person-rem exposures are one type of input to the total consequences evaluated in units of dollars for each release category. Direct economic costs are another type of input and this other type constitutes the greatest contribution to total consequence costs. Further independent checking resulted in a change to the computed source terms for release category case, Early 1B and an insignificant reduction in the source terms for release category case, Early 2A. All of these changes have been corrected and the resulting SAMA cost-benefit analysis reevaluated. The changes in results are documented in the form of a succinct statement of changes to the SAMA analysis submittals; i.e. the original SAMA report submitted in October, 2011 and all subsequent responses to RAIs.
The following summarizes the changes, the impacts on SAMA evaluations, and the responses to RAIs. In some cases, tables presented in one submittal were reviewed in later responses to RAIs.
In the summary below, only changes to the last submitted table are provided. When these revised tables were presented in earlier submittals, a cross-reference is provided to the final tables documented herein. The changes are presented in chronological order by submittal date of the past SAMAs reports, beginning with the submittal of October 2010.
Submittal of October 4, 2010 The findings of a review of the October 4, 2010 submittal of the Watts Bar Unit 2 Severe Accident Mitigation Alternatives report to account for correcting the total person-rem computed for each release category are provided below. A number of tables which initially appeared in the October 4, 2010 submittal must be updated to reflect these changes. Some of these tables have already been updated previously in response to subsequent RAIs on the October 4, 2010 submittal. The following cross-reference table directs the reader to the updated table numbers and the associated submittal date under which heading below, the final, updated table may be found.
October 4, 2010 Table Number Revised Table Number in RAI Responses Date of Submittal when Table last changed 8
2.a.iv-4a June 17, 2011 10a 2.a.iv-6 June 17, 2011 16 15-1 May 25, 2011 17 2.a.iv-8 January 31, 2011 18 2.a.iv-9 January 31, 2011 19 2.a.iv-10 January 31, 2011 20 2.a.iv-11 January 31, 2011
2 Two additional tables appearing in the October 4, 2010 are also changed to correct the total person-rem computed for each release category. These are Tables 10b and 21 below.
Table10b.Annual80Kilometer(50mile)PopulationDoseandEconomicCostRisk
Release Category Population Dose Risk (person-rem/year)
Economic Cost Risk (dollars/year)
I - LERF 3.73 7.99 x 103 II - BYPASS 0.84 1.86 x 103 III - LATE 14.14 4.14 x 104 IV-ISERF 1.24 2.25 x 103
3 Table21.EvacuationSpeedSensitivitySAMACaseResults
SAMA No.
SAMA Title Benefit/
Cost Ratio 2.2 mph Benefit/
Cost Ratio 3.4 mph Benefit/
Cost Ratio 1.6 mph Change in Conclusion 4
Improve DC bus load shedding.
1.26 1.26 1.27 NO 8
Increase training on response to loss of two 120V AC buses which causes inadvertent actuation signals.
0.47 0.47 0.47 NO 26 Provide an additional high pressure injection pump with independent diesel.
0.02 0.02 0.02 NO 32 Add the ability to automatically align emergency core cooling system to recirculation mode upon refueling water storage tank depletion.
0.19 0.19 0.20 NO 45 Enhance procedural guidance for use of cross-tied component cooling or service water pumps.
0.16 0.16 0.16 NO 46 Add a service water pump.
0.14 0.14 0.14 NO 56 Install an independent reactor coolant pump seal injection system, without dedicated diesel.
0.15 0.15 0.15 NO 70 Install accumulators for turbine-driven auxiliary feedwater pump flow control valves.
0.39 0.39 0.40 NO 71 Install a new condensate storage tank (auxiliary feedwater storage tank).
0.00 0.00 0.00 NO 87 Replace service and instrument air compressors with more reliable compressors which have self-contained air cooling by shaft driven fans.
0.00 0.00 0.00 NO 93 Install an unfiltered, hardened containment vent.
0.40 0.40 0.40 NO 101 Provide a reactor vessel exterior cooling system.
0.08 0.08 0.09 NO 103 Institute simulator training for severe accident scenarios.
0.18 0.17 0.18 NO 109 Install a passive hydrogen control system.
0.08 0.08 0.08 NO 110 Erect a barrier that would provide enhanced protection of the containment walls (shell) from ejected core debris following a core melt scenario at high pressure.
0.09 0.09 0.09 NO 112 Add redundant and diverse limit switches to each containment isolation valve.
0.00 0.00 0.00 NO 136 Install motor generator set trip breakers in control room.
0.06 0.05 0.06 NO 156 Eliminate RCP thermal barrier dependence on CCW, such that loss of CCW does not result directly in core damage.
24.70 24.67 24.77 NO. Proposed procedure change ineffective.
See Sec. 10 176 Provide a connection to alternate offsite power source.
0.09 0.09 0.09 NO 191 Provide self-cooled ECCS seals.
0.00 0.00 0.00 NO 215 Provide a means to ensure RCP seal cooling so that RCP seal LOCAs are precluded for SBO events.
0.88 0.88 0.88 NO
4 Table 21. Evacuation Speed Sensitivity SAMA Case Results (Continued)
SAMA No.
SAMA Title Benefit/
Cost Ratio 2.2 mph Benefit/
Cost Ratio 3.4 mph Benefit/
Cost Ratio 1.6 mph Change in Conclusion 226 Permanent, self-powered pump to backup normal charging pump.
0.49 0.49 0.49 NO 255 Permanent, Dedicated Generator for the NCP, one Motor Driven AFW Pump, and a Battery Charger.
0.26 0.26 0.26 NO 256 Install Fire Barriers Around Cables or Reroute the Cables Away from Fire Sources.
56.11 55.95 56.45 NO 276 Provide an auto start signal for AFW on loss of Standby Feedwater pump.
0.04 0.04 0.04 NO 279 Provide a permanent tie-in to the construction air compressor.
0.08 0.08 0.08 NO 280 Add new Unit 2 air compressor similar to the Unit 1 D compressor.
0.09 0.09 0.09 NO 282 Provide cross-tie to Unit 1 RWST.
0.00 0.00 0.00 NO 285 Improve training to establish feed and bleed cooling given no CCPs are running or a vital instrument board fails 3.85 3.85 3.86 NO 292 Improve training to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs 14.78 14.55 15.18 NO 295 Increase frequency of containment leak rate testing 0.06 0.06 0.06 NO 299 Initiate frequent awareness training for plant operators/ maintenance/ testing staff on key human actions for plant risk 10.66 10.65 10.69 NO 300 Revise procedure FR-H.1 to eliminate or simplify complex (and/or) decision logic for establishing feed and bleed cooling and to improve operator recovery from initial mistakes 0.57 0.57 0.57 NO 303 Move indication/ operator interface for starting hydrogen igniters to front MCR panel 0.03 0.03 0.03 NO 304 Add annunciator or alarm signaling parameters to initiate hydrogen igniters to front panel on MCR 0.03 0.03 0.03 NO 305 Revise procedure E-1 to include recovery steps for failure to initiate hydrogen igniters Not Estimated Not Estimated Not Estimated NO 306 Improve operator performance by enhancing likelihood of recovery from execution errors Not Estimated Not Estimated Not Estimated NO 307 Make provisions for connecting ERCW to CCP 2B-B 0.00 0.00 0.00 NO The list of conclusions in Section 10 of the October 4, 2010 submittal is unchanged, with one exception. SAMA 215 is now only to be considered if SAMA 58, which addresses the same RCP seal LOCA sequences, is not implemented. See the updated commitment in enclosure 2 of the submittal of May 25, 2011.
RAI Response Submittal of January 31, 2011
5 The findings of a review of the January 31, 2011 submittal in response to RAIs to account for correcting the total person-rem computed for each release category are provided below.
TVAs responses to items 1 through 2 of this submittal have been reviewed and concluded to be unchanged by correcting the total person-rem computed for each release category.
For item 3, a number of Tables which initially appeared in the January 31, 2011 submittal must be updated to reflect these changes. Some of these tables have subsequently been updated in response to later RAIs. These include Tables 2.a.iv-4 and 2.a.iv-6, which were last updated in the RAI response submittal of June 17, 2011; i.e. see the updated tables under that heading below.
Additionally, Tables 2.a.iv-7 through 2.a.iv-11, Table 4.d-2 and 5.c-1 are changed as a result of correcting the total person-rem computed for each release category. These updated tables are presented below.
Item 4a of this submittal concerns the identification and screening of candidate SAMAs. TVA used the basic event RRW values to CDF and to LERF to identify the key basic events for purposes of identification of candidate SAMAs. RRW cutoffs for identification were justified on the basis of the maximum averted cost risk (MACR) at that time and minimum costs applicable for training ($26,773) and for hardware fixes ($100,000). The cutoffs selected previously are modified here to reflect the changed MACR values after correcting the total person-rem computed for each release category.
Submittal date CDF LERF Training/ HRA Hardware Training/ HRA Hardware
$26,773
$100,000
$26,773
$100,000 1/31/2011 1.007 1.026 1.0293 1.117 September 2011 1.006 1.0227 1.0437 1.1817 A revision to Table 4.a.i-1, presenting the basic events with RRW greater than 1.006 is provided below. For CDF, four additional basic events are identified as having RRWs between 1.026 and 1.022; i.e. DGGFD2GEN_0822B-B, MTM_2GEN_0822B-B, U0_ERCW_PMP_FR_CCF_IE_ALL, and HAERCW3. All of these events were already evaluated for potential SAMAs in Table 4ai-1 of the January 31, 2011 submittal. No additional SAMAs are therefore identified for hardware fixes contributing to CDF at the revised RRW screening value.
For operator training and HRA related basic events contributing to CDF, two new HRA related basic events of lower importance now just exceed the lower RRW threshold of 1.006. These events are dependent HRA combinations named HRADEP-POST-293 and HRADEP-POST-193.
Three of the human actions which are included in these two dependent action groups have already been evaluated for potential improvements; i.e. for actions HARR1, HAFR1 and AFWOP3. The remaining human action event, used in both of these two dependent action combinations was not previously evaluated for potential SAMAs; i.e. HAMU2B - Makeup to
6 RWST using containment spray test recirculation from the containment sump during a small LOCA. This action outside the control room has an HEP value of 5E-3. The contributors to this human error probability are both from cognitive errors (3.1E-03) and from execution errors (1.9E-03). The cues and indications for this action are good and procedure ECA-1.1, Appendix C is clear in its direction of the action. A new SAMA, number 340, is defined here to improve the error rate for action HAMU2B by additional training.
As a Phase 1 screening analysis, we note that this new SAMA is at best marginal because even if the entire benefits of eliminating this error rate were obtained, the cost-benefit would be just
$26,773 considering the 2.28 multiplier and the 2.7 uncertainty on the CDF frequency. More likely the training should address both operations staff (to reduce the cognitive error rate) and those performing the action locally (execution errors). Further, the same procedure (ECA-1.1, step 10b) directs the operators to notify the TSC to evaluate transferring water to the RWST from other sources. These backup actions are not yet credited in the PRA model. Therefore, accounting for these other water sources as a means to lowering the 5E-3 error rate would further reduce the perceived benefit. New SAMA 340 is therefore considered screened on very low benefit.
For the LERF metric, the above RRW cutoff comparison table shows that the minimum RRW factors have increased from the previous evaluation. This is because the offsite exposure and offsite economic data from the October 4, 2011 used in the previous evaluation of these factors has changed. While the offsite economic costs for the early release category have gone up since the October 4, 2011 submittal, the offsite economic costs for the bypass release category have gone down by a greater amount. The latest consequence values for release categories were used in computing the revised RRW cutoffs. As a result, it now takes a greater change in LERF frequency to obtain the same benefit. Since the basic events with the lower LERF RRWs were evaluated for potential SAMAs in the January 31, 2011 submittal, no further potential SAMAs to reduce LERF need be postulated here. Table 4.a.ii-1 is unchanged and, therefore, not repeated here.
The RAI responses to item 4b (WBN1 IPE insights), item 4c (IPEEE seismic review screening),
item 4d (FIVE related SAMAs), item 4e (Phase I screening justifications), item 4f (internal flood prevention), item 4g (SAMA 242 screening), and item 4h (SAMA 296 screening) are all confirmed after correcting the total person-rem computed for each release category. The Phase I screening documented in Table 16 of the October 4, 2010 submittal is accurate as is and need not be updated.
For item 5, the conclusions of the Phase II cost-benefit calculations are unchanged. Tables summarizing the numerical changes caused by correcting the total person-rem computed for each release category are provided below. Table 2.a.iv-10 shows that the cost-benefit ratio for SAMA 93 went up from 0.95 to 1.08 and for SAMA 70 from 0.93 to 1.06. for the 95% CDF sensitivity case. However, these two SAMAs are already being addressed. The benefits of SAMA 70 will be reduced by TVAs commitment to implement SAMA 339. SAMA 93 will be evaluated further should SAMA 58 not prove reliable.
For item 6, the conclusions regarding the Phase I screening when considering the 95% results for
7 both CDF and LERF are unchanged after correcting for the total person-rem computed for each release category.
For item 7, the response is affirmed.
The list of 10 commitments in Enclosure 2 to this submittal is again affirmed. One exception is that for item 1, addressing SAMA 58. This commitment is restated as a revised commitment in enclosure 2 to the RAI response submittal of May 25, 2011. This restatement of the commitment is unrelated to correcting the total person-rem computed for each release category.
8 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description RCPSEAL182 2.07E-01 1.337 Reduce probability of large seal leak given loss of all RCP seal cooling Upgrade seals or enhance procedures to cooldown RCS before leakage 50, 58, 61, 155, 242, 260 RCP SEAL 182 GPM
%0LOSP-GR 1.01E-02 1.227 Loss of Offsite Power (Grid Related)
In training, emphasize steps in recovery of off-site power after an SBO.
Reduced human error probability during off-site power recovery.
22 Bury off-site power lines.
Improved off-site power reliability during severe weather.
24 Provide a connection to alternate offsite power source.
Increases offsite power redundancy.
176
9 Table 4ai Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Onsite AC power additionally fails Provide an additional diesel generator.
Increased availability of on-site emergency AC power.
9 Revise procedure to allow bypass of diesel generator trips.
Extended diesel generator operation.
10 Improve 4.16-kV bus cross-tie capability.
Increased availability of on-site AC power.
11
10 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Onsite AC power additionally fails (Continued)
Cross-tie diesel generators within or to the other unit's Increased availability of on-site AC power.
12, 229, 244 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans 160, 246
11 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description 182 gpm RCP seal LOCA results from SBO Implement enhanced RCP seal design.
Unit 2 has the upgraded high temperature o-rings in the Reactor Coolant Pumps. A new seal insert design has been proposed by Westinghouse which could eliminate seal LOCA sequences.
Pending topical report approval, this alternate seal design may prove cost effective, however costs are unknown at this time.
58, 232 Long term AFW fails during Station Blackout Create ability for emergency connection of existing or new water sources to feedwater and condensate systems.
Increased availability of feedwater.
66, 67, 75 PAF 9.03E-01 1.226 N/A Plant availability factor PLANT AVAILABILITY FACTOR
12 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description
%0LOSP-PC 8.12E-03 1.19 see %0LOSP-GR Loss of Offsite Power (Plant Centered)
PTSF12PMP_003001AS 2.43E-02 1.136 Improve reliability of TD AFW pump Upgrade unit 2 TD-AFW pump 223 PUMP FAILS TO START AND RUN FOR 1 HOUR WBN-1-3-1AS
%2CCS 1.00E+00 1.105 Total Loss of Component Cooling System Unit 2 Common cause failure of all CCS pumps Incorporate diverse positive displacement pump for CCS Improves reliability of CCS system.
274 Operators fail (HCCSR4) to align ERCW to train A charging pump Improve training to align and initiate alternate cooling to 2A-A or 2B-B CCPs when failed Procedure (AOI-15) already provided for loss of CCS.
Enhance training to improve chances of success.
51260, 299
13 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description 182 gpm seal LOCA develops Implement enhanced RCP seal design.
Unit 2 has the upgraded high temperature o-rings in the Reactor Coolant Pumps. A new seal insert design has been proposed by Westinghouse which could eliminate seal LOCA sequences.
Pending topical report approval, this alternate seal design may prove cost effective, however costs are unknown at this time.
58, 232 U0-CCS-PCO-FR-CCF-IE-ALL 2.75E-04 1.105 Reduce probability of core damage from seal LOCAs resulting from a loss of CCS system can improve procedures to cope with loss of CCS (cool-down RCS or cross-tie to ERCW),
add a diverse CCS pump 45, 49, 50, 53, 56, 59, 61, 64, 156, 157, 158 CCF of CCS PUMPS FAIL TO RUN, CCS HX PLUGGS, & CCS HX EXCESSIVE LEAKAGE/RUPTURE
14 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAFR1 3.70E-03 1.088 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73,299 Restore AFW control following initiator and loss of air SUMMER 2.00E-01 1.082 N/A Fraction of year SUMMER SEASON
%0LOSP-WI 2.03E-03 1.067 see %0LOSP-GR Loss of Offsite Power (Weather Induced)
%0FLRCW772A8 1.06E-06 1.066 Raw water pipe break in 5th vital battery room propagates to 480v shutdown boards causing station blackout Eliminate flood propagation path from battery room to 480v shutdown board rooms 293 Flood event induced by rupture of RCW line in room 772.0-A8
%0FLRCW772A9 1.06E-06 1.066 Raw water pipe break in HEPA filter room propagates to 480v shutdown boards causing station blackout Eliminate flood propagation path from HEPA filter room to 480v shutdown board rooms 294 Flood event induced by rupture of RCW line in room 772.0-A9
15 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FL-BATDEP 1.00E+00 1.065 N/A Flag event Battery Depleted FLAG HCCSR2 1.60E-02 1.06 Improve training to align and initiate alternate cooling from ERCW to 2A-A or 2B-B CCPs when CCS failed Procedure (AOI-15) already provided for loss of CCS.
Enhance training to improve chances of success.
51,260 ALIGN AND INITIATE ALTERNATE COOLING TO CCP 2A-A
%0TLERCW 1.00E+00 1.059 299,307 Total Loss of ERCW Common cause failure of all ERCW pumps or strainers Refurbish the ERCW pumps
& upgrade the capacity of the current pumps.
Improves the reliability of the ERCW pumps.
271
16 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Dependence of CVCS and SI Injection on ERCW Implement procedure to open the CVCS cross-tie valve to the opposite unit early in the accident response, or installation of a new, independently powered pump The initiation of charging flow from the opposite unit should provide sufficient RCP seal cooling to prevent RCP seal damage.
Another option is the installation of a new, independently powered pump, 154, 215 Create a reactor coolant depressurizati on system.
Allows low pressure emergency core cooling system injection in the event of small LOCA and high-pressure safety injection failure.
41
17 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description 182 gpm pump seal LOCA Implement enhanced RCP seal design.
Unit 2 has the upgraded high temperature o-rings in the Reactor Coolant Pumps. A new seal insert design has been proposed by Westinghouse which could eliminate seal LOCA sequences.
Pending topical report approval, this alternate seal design may prove cost effective, however costs are unknown at this time.
58, 232
18 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Dependence of AFW LCVs on compressed air Provide a permanent tie-in to the construction air compressor, or add new Unit 2 air compressor similar to the Unit 1 D compressor, or replace the ACAS compressors and dryers.
Improve availability of air system.
279, 280, 281 Short term AFW fails (e.g.
operators fail to locally control LCVs for TD AFWP (compressed air is lost),
HAFR1 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73
19 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Long-term AFW fails due to partial dependence on ERCW Create ability for emergency connection of existing or new water sources to feedwater and condensate systems.
Increased availability of feedwater.
66, 67, 75 DGGFR2GEN_0822A-A 1.46E-02 1.048 DIESEL GENERATOR FAILS TO RUN AFTER FIRST HOUR Provide a 2 MW blackout diesel generator to power Charging
9 Revise procedure to allow bypass of diesel generator trips extend diesel generator operation 10
20 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Improve 4.16-kv bus crosstie capability Increased availability of on-site AC power.
11 Cross-tie diesel generators within or to the other unit's Increased availability of on-site AC power.
12, 229, 244 XSBO14 4.59E-02 1.042 See %0LOSP-GR Recovery Sequence 7 (Common Cause of DG to Start) GR MTM_2GEN_0822A-A 1.51E-02 1.042 See DGGFR2GEN_0822 A-A DIESEL 2A-A MAINTENANCE DGGFR2GEN_0822B-B 1.46E-02 1.042 See DGGFR2GEN_0822 A-A DG 2B-B FAILS FAILS TO RUN (WBN-2-GEN -
082-0002B -B)
XSBO13 5.60E-02 1.042 See %0LOSP-GR Recovery Sequence 7 (Common Cause of DG to Start) PC
%2SLOCAL 2.88E-03 1.039 Small LOCA Stuck Open Safety Relief Valve
21 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Failure of high pressure recirculation from the sump, HARR1 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works Failure to cooldown and depressurize, AFWOP3 Failure to cooldown and depressurize, AFWOP3 Improve operator performance by enhancing likelihood of recovery from execution errors Procedure ECA-1.1, loss of RHR sump recirculation, governs this action 307 Failure to refill the RWST using containment spray pumps, HACH1 Failure to refill the RWST using containment spray pumps, HACH1 Improve operator performance by enhancing likelihood of recovery from execution errors Procedure ES-1.3 transfer to containment sump governs this action 33, 249,282, 306
22 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description XSBO11 6.62E-01 1.039 See %0LOSP-GR Recovery Sequence 4 (DG A And B Fail to Start And TDAFW Fails to Start) GR HAFR1_FL 1.00E+00 1.038 N/A Flag event Restore AFW control following HELB scenario induced by MSS supply to AFW line break. Unit 2, 1.0 FL-ATWS 1.00E+00 1.038 N/A Flag event ATWS FNSFD2FAN_030460 9.13E-03 1.035 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans 160, 246 BOARD ROOM EXHAUST FAN FAILS TO START OR RUN FIRST HOUR XSBO17 6.62E-01 1.035 See %0LOSP-GR Recovery Sequence 8 (Common Cause of DG to Start AND TDAWF Fails to Start) GR XSBO10 7.06E-01 1.033 See %0LOSP-GR Recovery Sequence 4 (DG A And B Fail to Start And TDAFW Fails to Start) PC
23 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FNSFD2FAN_030462 9.13E-03 1.032 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans 160, 246 BOARD ROOM EXHAUST FAN FAILS TO START OR RUN FIRST HOUR MTM_2PMP003001AS 8.52E-03 1.031 Improve reliability of TD AFW pump Upgrade unit 2 TD-AFW pump 223 PUMP WBN-2-3-1AS IN MAINTENANCE XSBO16 7.06E-01 1.03 See %0LOSP-GR Recovery Sequence 8 (Common Cause of DG to Start AND TDAWF Fails to Start) PC HRADEP-POST-221 8.60E-04 1.028 HAOB2 1.60E-02 Goal is to reduce error rate for operator action to initiate feed and bleed cooling Enhanced procedures already implemented, additional training could reduce error rate 79, 283,285, 300 Establish RCS Bleed and Feed cooling given no CCPS running
24 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAFR1 3.70E-03 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73, 299 Restore AFW control following initiator and loss of air, low dependence on HAOB2 HAERCW3 Improve training to align and initiate cooling from fire protection system to 2A-A or 2B-B CCPs when ERCW (and CCS) fails Procedure (AOI-13) already available for loss of ERCW.
Enhance training to improve chances of success.
45, 46,53, 54,56, 62,64, 155, 156 XSBO15 1.37E-01 1.027 See %0LOSP-GR Recovery Sequence 7 (Common Cause of DG to Start) WI U2_0BLOCK 7.50E-01 1.027 N/A See probability that 1 or more are blocked Probability that 0 PORVs are blocked DGGFR1GEN_0821B-B 1.46E-02 1.027 See DGGFR2GEN_0822 A-A DG 1B-B FAILS TO RUN DGGFD2GEN_0822A-A 6.88E-03 1.026 See DGGFR2GEN_0822 A-A DIESEL GENERATOR 2A-A FAILS TO START AND RUN FIRST HOUR
25 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description DGGFD2GEN_0822B-B 6.88E-03 1.024 See DGGFR2GEN_0822 A-A DIESEL GENERATOR FAILS TO START AND RUN FIRST HOUR (WBN-2-GEN -082-0002B -B)
MTM_2GEN_0822B-B 1.07E-02 1.024 See DGGFR2GEN_0822 A-A DIESEL 2B-B MAINTENANCE U0_ERCW_PMP_FR_CCF
_IE_ALL 6.32E-05 1.022 Improve reliability of ERCW pumps or limit the potential for seal LOCAs given the ERCW system is lost Pump improvements already implemented.
SAMAs identified to limit dependence on ERCW 46, 53, 56, 62, 155, 158, 271 CCF OF ALL ERCW PUMPS FAILS TO RUN IE HAERCW3 5.00E-02 1.022 Improve training to align and initiate cooling from fire protection system to 2A-A or 2B-B CCPs when ERCW (and CCS) fails Procedure (AOI-13) already available for loss of ERCW.
Enhance training to improve chances of success.
45, 46,53, 54,56, 62,64, 155, 156 OPERATOR FAILS TO ALIGN EXISTING FIRE PROTECTION PUMP TO CCP 2A-A 1.022 For multiplier of 2.28
26 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description U2_RPS_RT__RTB_FO_C CF_1_2 3.33E-06 1.021 Reduce probability of reactor trip failure Reduce challenges to plant trip or provide alternate means to trip reactor 136, 137, 218 CCF of two components:
RTBFO2RTB_0990000 A &
RTBFO2RTB_0990000 B
HAOSBF 2.00E-01 1.021 Improve training for manual steam generator level control Provide procedure for local control when control power is lost for station blackout and non station blackout sequences 73, 299 Blind Feed DGs Recovery U1_250BATTDEP 1.00E+00 1.021 Flag event HRADEP-POST-128 9.90E-05 1.02 HACH1 Improve operator performance by enhancing likelihood of recovery from execution errors Goal is to reduce error rate to transfer containment spray pumps to sump, (HACH1) given successful RHR swap over to the sump 35, 91, 92,105, 106,107,306
27 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HARR1 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 AFWOP3 Improve operator performance by enhancing likelihood of recovery from execution errors Sequence involves need to depressurize and cooldown the RCS for LPI following a small LOCA with failure of high pressure recirculation.
Numerous critical steps with limited recovery of slips or omissions 299
28 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description CMPSR0COMP03200060 6.29E-02 1.02 Improve availability of air system.
Provide a permanent tie-in to the construction air compressor, or add new Unit 2 air compressor similar to the Unit 1 D compressor, or replace the ACAS compressors and dryers.
86, 188,279, 280, 281 COMPRESSOR A-A FAILS TO RUN WBN 32-60 FLAB4F 1.30E-01 1.019 Improve reliability of high stress action to isolate the HPFP break in the auxiliary building.
Improve recovery from failure of execution step (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> available after alarm 167-D) which dominates error rate.
330 Isolate break in HPFP line (supplied by RCW -
HPFP diesel pump does not start
%0FLHPFPABF 5.49E-04 1.019 See FLAB4F 330 Flood event induced by HPFP in the common areas of the Auxiliary Building CMPSR0COMP03200086 6.29E-02 1.019 see CMPSR0COMP032 00060 COMPRESSOR B-B FAILS TO RUN WBN 32-86 HRADEP-POST-180 9.70E-05 1.019
29 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAAEIE 1.80E-03 Reduce execution error of failure to start standby ERCW pump Add recovery step for execution error in starting ERCW pump (HAAEIE=1.8E-3) in response to 2 ERCW pumps failing to run 331 Start standby ERCW pump - operating pump fails - normal ops HAFR1 3.70E-03 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73, 299 Restore AFW control following initiator and loss of air, (when ERCW failed), low dependence with HAAEIE
%2TTIE 2.32E-01 1.018 Reduce frequency of turbine trip Improve reliability of power supplies.
218 Turbine Trip MTM_1GEN_0821B-B 1.22E-02 1.018 See DGGFR2GEN_0822 A-A DIESEL 1B-B MAINTENANCE FNSFD1FAN_030461 9.13E-03 1.017 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans 160, 246 BOARD ROOM EXHAUST FAN FAILS TO START OR RUN FIRST HOUR, on DG 1B-B
30 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description SSIOP 6.70E-03 1.017 Improve training and annunciating to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs Training already conducted on inadvertent Safety Injection (SI),
8,292, 299, 306 Terminate Safety Injection to prevent PORV water challenge
31 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HRADEP-POST-309 2.50E-05 1.016 SSIOP 6.70E-03 Improve training and annunciating to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs Training already conducted on inadvertent Safety Injection (SI),
8,292, 299, 306 Terminate Safety Injection to prevent PORV water challenge HARR1 3.80E-03 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works, medium dependence on SSIOP
32 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FL_SPARE_250_CHGR_N OT_A 1.00E+00 1.016 Flag event SPARE CHARGER NOT ALIGNED FOR A TRAIN MTM_2PMP_0620108A 3.78E-03 1.015 Reduce fraction of time charging pump in maintenance while plant is at power Reschedule CCP maintenance to shutdown conditions 328 WBN-2-PMP-062-0108-A CCP 1A-A IN MAINTENANCE
%2SSBO-1 2.50E-03 1.014 SECONDARY BREAK OUTSIDE CONTAINMENT SG 1 Failure to terminate SI Improve training and annunciating to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs Training already conducted on inadvertent Safety Injection (SI),
8, 292,299
33 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Failure to align for high pressure recirculation from the sump, HARR1 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299
%2SSBO-4 2.50E-03 1.014 see %2SSBO-1 SECONDARY BREAK OUTSIDE CONTAINMENT SG 4
%2SSBO-2 2.50E-03 1.014 see %2SSBO-1 SECONDARY BREAK OUTSIDE CONTAINMENT SG 2
%2SSBO-3 2.50E-03 1.014 see %2SSBO-1 SECONDARY BREAK OUTSIDE CONTAINMENT SG 3 U2-AFW-TOT-PMA-FD-CCF_1_2 4.04E-04 1.014 Reduce CCF failure probability of MD AFW pump CCF pump failure probability not measurably affected by procedures, training, nor indications None CCF of two components:
PMAF12PMP_0030011 8 &
PMAF12PMP_0030012 8
34 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description DGGFR1GEN_0821A-A 1.46E-02 1.014 See DGGFR2GEN_0822 A-A DG 1A-A FAILS TO RUN PTSFR2PMP_003001AS 1.76E-03 1.013 Random pump failure not measurably affected by procedures, training, nor indications None PUMP FAILS AFTER 1 HOUR WBN-2-3-1AS
%0FLTBMF 8.58E-03 1.013 Reduce operator action error to recover from turbine building flood with independent failure of ACAS.
Recovery actions addresses with action group HRADEP-POST-221 None Major flood in the Turbine Building DGGFD1GEN_0821B-B 6.88E-03 1.013 See DGGFR2GEN_0822 A-A DG 1B-B FAILS TO START AND RUN FIRST HOUR
35 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FNSFD2FAN_03000214 9.13E-03 1.012 Reduce frequency of losing all AFW caused when all room cooling is lost to TD AFW pump.
Operator action to open room containing AFW pump should suffice.
Action is called for in procedures and PRA model already considers action to restore AFW under Station blackout conditions (HAAF1) when local manual control is required.
However, only credit for offsite power recovery is conservatively modeled when this fan also fails.
Already implemented DC EMERG EXHAUST FAN FAILS TO START AND RUN FOR 1ST HOUR WBN-2-30-214, for TD AFW pump room PRAI2 1.70E-01 1.012 Reduce time fraction that pressure relief requires 3 SVs and 2 PORVs during an ATWS Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None Interval 2 for PRA (pres relief requires 3 SVs & 2 PORVs)
SEQFD2A-A 3.33E-03 1.012 See DGGFR2GEN_0822 A-A SEQUENCER 2A-A FAILS (Unknown UNID)
%2RTIE 2.85E-01 1.012 Reduce frequency of reactor trip Improve reliability of power supplies.
218 Reactor Trip
36 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAOB2 1.60E-02 1.012 Improve training or revise procedure to establish feed and bleed cooling given no CCPs are running Enhanced procedures already implemented, additional training could reduce error rate 283, 285, 299, 300 Establish RCS Bleed and Feed cooling given no CCPS running U0_ERCW_TS_PL_CCF_I E_ALL 6.73E-04 1.011 Refurbish the ERCW pumps
& upgrade the capacity of the current pumps.
Improves the reliability of the ERCW pumps.
271 CCF of all components in group
'U0_ERCW_TS_PL_CC F_IE', 2 MD AFW pumps
%2LVBB4 1.00E+00 1.011 Loss of Battery Board 4 Loss of AFW given battery board fails Improve training for MD AFW pump trains A and B and for TD AFW pump isolation tests Additional training may reduce isolation error rate 284,286 Feed and bleed cooling fails given battery board fails Improve training to establish feed and bleed cooling given battery board lost Enhanced procedures already implemented, additional training could reduce error rate 285, 283
37 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description Failure of high pressure recirculation during feed and bleed with battery board lost Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32,34,36, 187,238,247 SEQFD2B-B 3.33E-03 1.011 See DGGFR2GEN_0822 A-A SEQUENCER 2B-B FAILS (Unknown UNID)
%2PLMFW 1.46E-01 1.011 Random pump and valve failures not measurably affected by procedures, training, nor indications None Partial Loss of Main Feedwater
38 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description U0_EPS_VDG_FAN_FD2_
CCF_ALL 1.62E-04 1.011 See DGGFR2GEN_0822 A-A, opening room doors is not sufficient to adequately cool the DG room None CCF of all components in group
'U0_EPS_VDG_FAN_F D2_CCF' FNSFR2FAN_03000183 2.66E-03 1.011 Add procedures and perform analysis to justify that CCP room may be adequately cooled by just opening doors when room cooling is lost.
PRA assumes room cooler is required (cooled by ERCW) for pump operation.
Opening door to CCP room is not included in the PRA nor yet verified to be effective at keeping temperatures acceptable 337 CCP A ROOM COOLER FAN FAILS DURING OPERATION MTM_0CAD03204900 3.30E-02 1.011 Reduce fraction of time CAS compressor D in maintenance while plant is at power Reschedule CAS compressor D maintenance to shutdown conditions 329 CAS COMPRESSOR D IN MAINTENANCE WBN-0-32-COMP-4900 XSBO12 9.31E-01 1.011 See %0LOSP-GR Recovery Sequence 4 (DG A And B Fail to Start And TDAFW Fails to Start) WI
39 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description
%0FLRCWABMF 3.94E-05 1.01 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty. Current PRA model gives no credit for action to cope with loss of air, but procedures apply equally well to flood induced losses.
70, 73,299 Major flood event induced by RCW in the common areas of the Auxiliary Building (
POEFR0PMP_06700028IE 2.97E-02 1.01 Secondary contributor to loss of ERCW initiating event; see responses for
%0TLERCW, HAAEIE, and HAERCW3 ERCW PUMP A-A FAILS TO RUNINITIATING EVENT WBN-0-67-28 POEFR0PMP_06700036IE 2.97E-02 1.01 Secondary contributor to loss of ERCW initiating event; see responses for
%0TLERCW, HAAEIE, and HAERCW3 ERCW PUMP C-A FAILS TO RUN INITIATING EVENT WBN-0-67-36
40 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description POEFR0PMP_06700047IE 2.97E-02 1.01 Secondary contributor to loss of ERCW initiating event; see responses for
%0TLERCW, HAAEIE, and HAERCW3 ERCW PUMP E-B FAILS TO RUN CC 1/4 INITIATING EVENT WBN-0-67-E-B POEFR0PMP_06700055IE 2.97E-02 1.01 Secondary contributor to loss of ERCW initiating event; see responses for
%0TLERCW, HAAEIE, and HAERCW3 ERCW PUMP G-B FAILS TO RUNINITIATING EVENT WBN-0-67-55 FNSFD2FAN_030448 9.13E-03 1.01 See DGGFR2GEN_0822 A-A, opening room doors is not sufficient to adequately cool the DG room None EXHAUST FAN FAILS TO START OR RUN FIRST HOUR FNSFD2FAN_030452 9.13E-03 1.01 See DGGFR2GEN_0822 A-A, opening room doors is not sufficient to adequately cool the DG room None EXHAUST FAN FAILS TO START OR RUN FIRST HOUR
41 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description XSBO18 9.31E-01 1.01 See %0LOSP-GR Recovery Sequence 8 (Common Cause of DG to Start AND TDAWF Fails to Start) WI PRAI3 1.50E-01 1.01 Reduce time fraction that pressure relief requires 3 SVs and 1 PORV during an ATWS Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None Interval 3 for PRA (pres relief requires 3 SVs & 1 PORV)
CBKFO2BKR_2111816/16
-A 2.55E-03 1.009 Improve reliability of 6.9kv circuit breaker to SD BD to open on demand Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None 6.9kV SDBD BREAKER 1816 FAILS TO OPEN, required for power from EDG RLVFO2RFV_0620636 2.47E-03 1.009 Reduce potential for failing to open on demand the common relief valve on seal return Basic plant design cannot be changed by revising procedures, additional training, nor additional indications. Local action to open breaker would be too late to achieve success.
None WBN-1-RFV-062-0636-S RELIEF VALVE FAILS TO OPEN on common seal injection return line HRADEP-POST-289 1.10E-02 1.009
42 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description AFWOP1 2.10E-02 Improve operator performance by improving procedures and training for completing RCS depressurizati on during a medium LOCA to allow low pressure injection Action error rate dominated by execution steps which are already well documented in ES-1.2, though high stress is postulated for the medium LOCA. High dependence assumed between execution steps and occurrence of feedback to operators for recovery.
338 Depressurize/cooldown to low pressure injection following MLOCA
43 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HARR1 3.80E-03 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works; high dependence on AFWOP1 U2_ESF_SGD_CF_517_C CF_1_2 9.32E-05 1.009 Reduce CCF probability of multiple safeguard driver cards resulting in loss of actuation signals Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None CCF of two components:
SGDCF2SGD_099A517 A &
SGDCF2SGD_099A517 B
MTM_1GEN_0821A-A 1.10E-02 1.009 See DGGFR2GEN_0822 A-A DIESEL 1A-A MAINTENANCE
44 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FNSFD1FAN_030459 9.13E-03 1.009 FNSFD1FAN_03046 1
BOARD ROOM EXHAUST FAN FAILS TO START OR RUN FIRST HOUR, DG 1A-A BUSFR0BD__2364G_IE 3.80E-03 1.009 Improve reliability of DC bus to operate Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None 125V DC VITAL BATTERY BOARD IV FAILS DURING OPERATION
%2CCS2A 1.00E+00 See %2CCS Loss of Component Cooling System Train 2A HRADEP-POST-220 2.40E-03 1.009 HACD1 Improve manual actions to re-establish secondary heat removal or initiate bleed and feed cooling when automatic actuation of AFW fails Can provide alternate means to establish secondary heat removal or improve training and procedures to respond to loss of actuation signal 66,68, 276, 296, 299 Perform cooldown with main feedwater, following AFW failure HAOS3 Start AFW (Reactor trip, no SI), medium dependence on HACD1
45 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAOB2 Goal is to reduce error rate for operator action to initiate feed and bleed cooling Enhanced procedures already implemented, additional training could reduce error rate 79, 283,285, 300 Establish RCS Bleed and Feed cooling given no CCPS running, high dependence on HAOS3 HRADEP-POST-218 5.40E-03 1.009 HACD1 3.24E-02 Improve manual actions to re-establish secondary heat removal or initiate bleed and feed cooling when automatic actuation of AFW fails Can provide alternate means to establish secondary heat removal or improve training and procedures to respond to loss of actuation signal 66,68, 276, 296, 299 Perform cooldown with main feedwater, following AFW failure HAOB2 1.60E-02 Goal is to reduce error rate for operator action to initiate feed and bleed cooling Enhanced procedures already implemented, additional training could reduce error rate 79, 283,285, 300 Establish RCS Bleed and Feed cooling given no CCPS running, medium dependence on HACD1
46 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HARR1 3.80E-03 1.009 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works CBKFO2BKR_2111828/16
-B 2.55E-03 1.009 Improve reliability of 6.9kv circuit breaker to SD BD to open on demand Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None 6.9kV SDBD BREAKER 1828 FAILS TO OPEN, required for power from EDG
47 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description
%0FLHPFPAB757A2 1.44E-07 1.008 Flood event induced by break of HPFP line in room 757.0-A2 propagates to all 4 6.9kv shutdown boards causing station blackout Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None Flood event induced by break of HPFP line in room 757.0-A2 HRADEP-POST-305 1.30E-05 1.008 HCRL1 3.80E-03 Reduce likelihood that operators reset SI signal failing sump auto-swap over by including execution recovery step in procedures Sequence involves
%SSBO-1,2,3,4 with failure to terminate SI prior to PZR PORV water challenge; Modify procedures to ensure that operators confirm that no RCS leakage occurs once PORV is challenged to minimize chance of inadvertently resetting SI signal.
333 Inadvertently Reset SI Signal, Failure of Auto Sump Swap over
48 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description SSIOP 6.60E-03 Improve training and annunciating to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs Training already conducted on inadvertent Safety Injection (SI),
8,292, 299, 306 Terminate Safety Injection to prevent PORV water challenge, high dependence on HCRL1 HARL1 2.30E-03 Improve procedures to include recovery from execution errors Human error rate conservatively evaluated assuming timing for a large LOCA. Much greater time available for secondary side breaks with stuck open PZR PORV 334 Recover from auto swap over failure, medium dependence on SSIOP U0_EPS_GA_GEN_FR_C CF_2_3 3.59E-04 1.008 See DGGFR2GEN_0822 A-A CCF of two components:
DGGFR1GEN_0821B-B DGGFR2GEN_0822A-A
49 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FNSFD2FAN_030450 9.13E-03 1.008 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans; already implemented at Watts Bar 160, 246 EXHAUST FAN FAILS TO START OR RUN FIRST HOUR FNSFD2FAN_030454 9.13E-03 1.008 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans; already implemented at Watts Bar 160, 246 EXHAUST FAN FAILS TO START OR RUN FIRST HOUR
%0TLPCA 9.81E-03 1.008 See HAFR1 Total Loss of Plant Compressed Air HRADEP-POST-171 2.10E-04 1.008 DHAERCWS 3.80E-03 Reduce execution error rate by adding recovery step to procedures Action is to start selected pump to allow traveling screen to rotate at least one full revolution, for 20 minutes or until no longer needed 332 Operators fail to clear ERCW screens before plant trip
50 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAFR1 3.70E-03 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73,299 Restore AFW control following initiator and loss of air, low dependence on DHAERCWS FNSFR2FAN_030460 2.66E-03 1.008 Provide for improved credit to be taken for loss of HVAC sequences, especially for the DG electric board rooms open doors or use adjacent room's exhaust fans; already implemented at Watts Bar 160, 246 EXHAUST FAN 2-FAN-30-460 FAILS TO RUN MTM_2FAN_03000183 2.00E-03 1.008 Add procedures and perform analysis to justify that CCP room may be adequately cooled by just opening doors when room cooling is lost.
PRA assumes room cooler is required (cooled by ERCW) for pump operation.
Opening door to CCP room is not included in the PRA nor yet verified to be effective at keeping temperatures acceptable 337 CCP A ROOM COOLER FAN IN MAINTENANCE
51 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description TTM_2FAN_03000183 2.00E-03 1.008 Add procedures and perform analysis to justify that CCP room may be adequately cooled by just opening doors when room cooling is lost.
PRA assumes room cooler is required (cooled by ERCW) for pump operation.
Opening door to CCP room is not included in the PRA nor yet verified to be effective at keeping temperatures acceptable 337 CCP A ROOM COOLER FAN IN TEST CMPSR0COMP03200025 6.29E-02 1.008 See CMPSR0COMP032 00060 and HAFR1 CAS COMPRESSOR A FAILS TO RUN WBN 32-25 CMPSR0COMP03200026 6.29E-02 1.008 See CMPSR0COMP032 00060 and HAFR1 COMPRESSOR B FAILS TO RUN WBN 32-26 HART1 1.40E-03 1.008 Reduce probability of reactor trip failure Reduce challenges to plant trip or provide alternate means to trip reactor 136, 137,218 Manually trip reactor, given SSPS fails
52 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description
%0FLRCW757A17 1.27E-07 1.007 Flood event induced by rupture of RCW line in room 757.0-A17 propagates to all 4, 6.9kv shutdown boards causing station blackout Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None Flood event induced by rupture of RCW line in room 757.0-A17
%0FLRCW757A9 1.27E-07 1.007 Flood event induced by rupture of RCW line in room 757.0-A9 propagates to all 4, 6.9kv shutdown boards causing station blackout Basic plant design cannot be changed by revising procedures, additional training, nor additional indications.
None Flood event induced by rupture of RCW line in room 757.0-A9 XSBO25 5.00E-01 1.007 See %0LOSP-GR ALIGN PORTABLE DIESEL GENERATOR TO SHUTDOWN BOARD 2B-B
53 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description U0_ERCW_PMP_FR_CCF
_ALL 3.88E-06 1.007 See %0TLERCW CCF of all components in group
'U0_ERCW_PMP_FR_
CCF' FNSFD2FAN_03000182 9.13E-03 1.007 See FNSFR2FAN_03000 183 CCP 1B-B ROOM COOLING FAN FAILS TO START AND RUN FOR FIRST HOUR DHARR3 1.00E-03 1.007 Reduce error rate for operators failing to restart an Residual Heat Removal (RHR) pump for HP recirculation from the sump after previously securing SI.
Revise procedures and training to address this human action (DHARR3 =
1E-3).
336 OPERATOR FAILS TO RESTART RHR PUMP FOR HP RECIRCULATION U0_032_ACAS_CMP_FR_
CCF_1_2 3.25E-03 1.007 See CMPSR0COMP032 00060 CCF of two components:
CMPSR0COMP032000 60 &
CMPSR0COMP032000 86 FNSFR2FAN_030462 2.66E-03 1.007 See FNSFR2FAN_03046 0
EXHAUST FAN 2-FAN-30-462 FAILS TO RUN
54 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description SMPPL2STN_SUMP1 1.00E-03 1.007 Reduce probability of sump strainers plugging precluding recirculation from the sump Biggest contributors from steam line breaks leading to stuck open PZR PORVs' i.e., smaller LOCAs. Basic plant design cannot be changed by revising procedures, additional training, nor additional indications. Local action to open breaker would be too late to achieve success.
None SUMP SUCTION STRAINERS PLUGGED (LLOCA OR MLOCA)
DGGFD1GEN_0821A-A 6.88E-03 1.007 See DGGFR2GEN_0822 A-A DG 1A-A FAILS TO START AND RUN FIRST HOUR HXRPL2HTX_07000185IE T
5.65E-03 1.007 Sequence leads to loss of CCS with seal LOCA and fails recirculation from sump due to multiple operator actions (HRADEP-POST-A1). Consider improvements to associated human actions below Hardware fixes not cost effective WBN-2-HTX-070-0185 CCS HEAT EXCHANGER A PLUGGING
55 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HCCSR2 1.60E-02 See HCCSR2 ALIGN AND INITIATE ALTERNATE COOLING TO CCP 2A-A HACH1 1.10E-02 See %2SLOCAL Transfer Containment Spray to Sump (RHR Swap Successful)
AFWOP3 1.10E-02 See %2SLOCAL Depressurize/cooldown to low pressure injection following small LOCA with failure HRADEP-POST-B7 7.61E-03 1.007 HAERCW2 7.80E-02 Improve training and procedures to cross-connect fire protection pump flow to ERCW in the event ERCW pumps all fail as initiating event with power from shutdown boards available Procedure MA-1, Rev 3, Appendix C details the steps to follow.
335 OPERATOR FAILS TO ALIGN FIRE PROTECTION PUMP TO ERCW HEADER
56 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAERCW3 5.00E-02 Improve training to align and initiate cooling from fire protection system to 2A-A or 2B-B CCPs when ERCW (and CCS) fails Procedure (AOI-13) already available for loss of ERCW.
Enhance training to improve chances of success.
45, 46,53, 54,56, 62,64, 155, 156 OPERATOR FAILS TO ALIGN EXISTING FIRE PROTECTION PUMP TO CCP 2A-A, low dependence on HAERCW2 performed within minutes AOCFC0PCV_03300004 7.39E-04 1.006 N/A Not Training or HRA related AOV FAILS TO CLOSE ON DEMAND WBN-0-33-4 CRI 1.20E-06 1.006 N/A Not Training or HRA related CONTROL RODS FAIL TO INSERT FNSFR2FAN_03000214 2.66E-03 1.006 N/A Not Training or HRA related DC EMERGENCY EXHAUST FAN FAILS TO RUN AFTER 1ST HOUR WBN-2-30-214
%0FLHPFPAB757A24 1.07E-07 1.006 N/A Not Training or HRA related Flood event induced by break of HPFP line in room 757.0-A24
57 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HRADEP-POST-293 2.10E-04 1.006 Failure of high pressure recirculation from the sump, HARR1 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in license operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works HAFR1 3.70E-03 Improve training for loss of air after plant trip Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty 70, 73, 299 Restore AFW control following initiator and loss of air, low dependence on HAOB2
58 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HRADEP-POST-193 3.1E-05 1.006 Failure of high pressure recirculation from the sump, HARR1 Improve operator performance and minimize need for manual action to complete high pressure recirculation alignment Existing EOPs provide directions for monitoring and conserving water in the containment recirculation sump.
These procedures are already used extensively in licensed operator initial training and license operator continuing training programs, and are practiced in the plant simulator.
31,32, 34,36, 187,238, 247,299 Align high pressure recirculation, given auto swap over works AFWOP3 1.10E-02 See %2SLOCAL Depressurize/cooldown to low pressure injection following small LOCA with failure
59 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description HAMU2B 5E-03 Improve operator performance via training Cognitive contribution is 3.1E-03, Execution is 1.9E-03. Procedure ECA-1.1 governs 340 (New)
Makeup to RWST using containment spray test recirculation from the containment sump during a small LOCA XPORV1 5.29E-02 1.006 N/A Not Training or HRA related BLOCK VALVE CLOSED TO ISOLATE LEAKING PORV U0_EPS_GA_GEN_FD_CCF
_ALL 9.01E-05 1.006 N/A Not Training or HRA related CCF of all components in group
'U0_EPS_GA_GEN_FD_C CF' SRVSR2SRV_06800563 7.95E-04 1.006 N/A Not Training or HRA related SAFETY VALVE FAILS TO RESEAT AFTER STEAM RELIEF WBN 68-563 SRVSR2SRV_06800564 7.95E-04 1.006 N/A Not Training or HRA related SAFETY VALVE FAILS TO RESEAT AFTER STEAM RELIEF WBN 68-564 SRVSR2SRV_06800565 7.95E-04 1.006 N/A Not Training or HRA related SAFETY VALVE FAILS TO RESEAT AFTER STEAM RELIEF WBN 68-565
60 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description FLTB1C 1.00E-02 1.006 N/A Not Training or HRA related Isolate CCW following major break in Turbine Building
%2TLMFW 7.01E-02 1.006 N/A Not Training or HRA related Total Loss of Main Feedwater SEQFD1B-B 3.33E-03 1.006 N/A Not Training or HRA related SEQUENCER 1B-B FAILS (Unknown UNID)
%2EX 1.00E-07 1.006 N/A Not Training or HRA related EXCESSIVE LOCA (VESSEL RUPTURE)
CMPSR0COMP03200027 6.29E-02 1.006 N/A Not Training or HRA related COMPRESSOR C FAILS TO RUN WBN-0-32-27
%2LOCV 6.53E-02 1.006 N/A Not Training or HRA related Loss of Condenser Vacuum
61 Table 4ai-1 Review of Basic Events with RRW Greater than 1.006 to CDF for Potential New RAI SAMAs (Continued)
Event Name Probability Red W
SAMA Title SAMA Discussion SAMA #
Description MTM_2PMP00300128 4.22E-03 1.006 N/A Not Training or HRA related PUMP WBN-2-3-128-B IN MAINTENANCE PMAF12PMP_00300118 2.89E-03 1.006 N/A Not Training or HRA related PUMP FAILS TO START AND RUN FOR 1 HOUR WBN-2-3-118-A MTM_2PMP00300118 3.84E-03 1.006 N/A Not Training or HRA related PUMP WBN-2-3-118-A IN MAINTENANCE 1.006 for Multiplier of 2.28
62 Table 2.a.iv-7.
RAI Revised Base Cost Comparison October 2010, SAMA Report Revised (RAI) Sept 2011 SAMA Results
% Change Base Cost with External Event Muliplier 2.0
$3,309,176
$3,860,606
+ 17%
Base Cost with External Event Multiplier 2.28
$3,772,461
$4,401,090
+ 17%
63 Table 2.a.iv RAI Revised SAMA Phase II Analysis Results Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.0)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion 4
Improve DC bus load shedding.
$35,111
$31,675 1.11 Already committed to do, see Jan.,2009t SAMA submittal
$40,026
$31,675 1.26 Already committed to do, see January, 2009SAMA submittal 8
Increase training on response to loss of two 120V AC buses which causes inadvertent actuation signals.
$10,949
$26,773 0.41 Already committed to do, see January, 2009 SAMA submittal
$12,482
$26,773 0.47 Already committed to do, see January, 2009 SAMA submittal 26 Provide an additional high pressure injection pump with independent diesel.
$57,181
$3,571,000 0.02 Not cost beneficial
$65,186
$3,571,000 0.02 Not cost beneficial 32 Add the ability to automatically align emergency core cooling system to recirculation mode upon refueling water storage tank depletion.
$351,587
$2,100,000 0.17 Not cost beneficial
$400,809
$2,100,000 0.19 Not cost beneficial 45 Enhance procedural guidance for use of cross-tied component cooling or service water pumps.
$4,562
$31,675 0.14 Not cost beneficial
$5,201
$31,675 0.16 Not cost beneficial 46 Add a service water pump.
$129,763
$1,042,511 0.12 Not cost beneficial
$147,930
$1,042,511 0.14 Not cost beneficial 56 Install an independent reactor coolant pump seal injection system, without dedicated diesel.
$1,080,157
$8,233,000 0.13 Not cost beneficial
$1,231,379
$8,233,000 0.15 Not cost beneficial 70 Install accumulators for turbine-driven auxiliary feedwater pump flow control valves.
$88,566
$256,204 0.35 Not cost beneficial
$100,966
$256,204 0.39 Not cost beneficial 71 Install a new condensate storage tank (auxiliary feedwater storage tank).
$0
$1,706,586 0.00 Not cost beneficial
$0
$1,706,586 0.00 Not cost beneficial
64 Table 2.a.iv RAI Revised SAMA Phase II Analysis Results (Continued)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.0)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion 87 Replace service and instrument air compressors with more reliable compressors which have self-contained air cooling by shaft driven fans.
$1,908
$886,205 0.00 Not cost beneficial
$2,175
$886,205 0.00 Not cost beneficial 93(See Note 1)
Install an unfiltered, hardened containment vent.
$1,089,701
$3,100,000 0.35 Not cost beneficial
$1,242,259
$3,100,000 0.40 Not cost beneficial 101 Provide a reactor vessel exterior cooling system.
$182,392
$2,500,000 0.07 Not cost beneficial
$207,927
$2,500,000 0.08 Not cost beneficial 103 Institute simulator training for severe accident scenarios.
$1,229,070
$8,000,000 0.15 Not cost beneficial, Cost includes new software and hardware upgrade
$1,401,139
$8,000,000 0.18 Not cost beneficial, Cost includes new software and hardware upgrade 109 Install a passive hydrogen control system.
$265,139
$3,736,000 0.07 Not cost beneficial
$302,259
$3,736,000 0.08 Not cost beneficial 110 Erect a barrier that would provide enhanced protection of the containment walls (shell) from ejected core debris following a core melt scenario at high pressure.
$90,783
$1,151,000 0.08 Not cost beneficial
$103,493
$1,151,000 0.09 Not cost beneficial 112 Add redundant and diverse limit switches to each containment isolation valve.
$2,815
$691,524 0.00 Not cost beneficial
$3,210
$691,524 0.00 Not cost beneficial 136 Install motor generator set trip breakers in control room.
$11,679
$241,795 0.05 Not cost beneficial
$13,315
$241,795 0.06 Not cost beneficial 156 Eliminate RCP thermal barrier dependence on CCW, such that loss of CCW does not result directly in core damage.
$686,176
$31,675 21.66 Proposed procedure change ineffective. See Section 10 of Oct., 2010 SAMA report
$782,241
$31,675 24.70 Proposed procedure change ineffective.
See Section 10 of Oct., 2010 SAMA report
65 Table 2.a.iv RAI Revised SAMA Phase II Analysis Results (Continued)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.0)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion 176 Provide a connection to alternate offsite power source.
$686,153
$9,126,460 0.08 Not cost beneficial
$782,214
$9,126,460 0.09 Not cost beneficial 191 Provide self-cooled ECCS seals.
$0
$1,000,000 0.00 Not cost beneficial
$0
$1,000,000 0.00 Not cost beneficial 215 Provide a means to ensure RCP seal cooling so that RCP seal LOCAs are precluded for SBO events.
$1,153,970
$1,500,000 0.77 Not cost beneficial; first of a kind installation; downside impacts on risk impact not assessed
$1,315,525
$1,500,000 0.88 Not cost beneficial; first of a kind installation; downside impacts on risk impact not assessed 226 Permanent, self-powered pump to backup normal charging pump.
$1,153,970
$2,700,000 0.43 Not cost beneficial
$1,315,525
$2,700,000 0.49 Not cost beneficial 255 Permanent, Dedicated Generator for the NCP, one Motor Driven AFW Pump, and a Battery Charger.
$737,229
$3,225,000 0.23 Not cost beneficial
$840,441
$3,225,000 0.26 Not cost beneficial 256 Install Fire Barriers Around Cables or Reroute the Cables Away from Fire Sources.
$965,083
$19,608 49.22 Already committed to do, see January, 2009 SAMA submittal
$1,100,195
$19,608 56.11 Already committed to do, see January, 2009 SAMA submittal 276 Provide an auto start signal for AFW on loss of Standby Feedwater pump.
$22,114
$615,605 0.04 Not cost beneficial
$25,210
$615,605 0.04 Not cost beneficial 279 Provide a permanent tie-in to the construction air
$63,064
$909,893 0.07 Not cost beneficial
$71,893
$909,893 0.08 Not cost beneficial
66 Table 2.a.iv RAI Revised SAMA Phase II Analysis Results (Continued)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.0)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion compressor.
280 Add new Unit 2 air compressor similar to the Unit 1 D compressor.
$63,064
$814,546 0.08 Not cost beneficial
$71,893
$814,546 0.09 Not cost beneficial 282 Provide cross-tie to Unit 1 RWST.
$18,319
$10,215,000 0.00 Not cost beneficial
$20,883
$10,215,000 0.00 Not cost beneficial 285 Improve training to establish feed and bleed cooling given no CCPs are running or a vital instrument board fails
$90,528
$26,773 3.38 Potentially cost beneficial
$103,202
$26,773 3.85 Potentially cost beneficial 292 Improve training to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs
$347,048
$26,773 12.96 Potentially cost beneficial
$395,634
$26,773 14.78 Potentially cost beneficial 295 Increase frequency of containment leak rate testing
$126,291
$2,500,000 0.05 Not cost beneficial
$143,972
$2,500,000 0.06 Not cost beneficial 299 Initiate frequent awareness training for plant operators/
maintenance/ testing staff on key human actions for plant risk
$250,281
$26,773 9.35 Potentially cost beneficial
$285,320
$26,773 10.66 Potentially cost beneficial 300(Se e Note 1)(See Note 1)
Revise procedure FR-H.1 to eliminate or simplify complex (and/or) decision logic for establishing feed and bleed cooling and to improve operator recovery from initial mistakes
$50,156
$100,000 0.50 Not cost beneficial; Requires PWROG approval
$57,178
$100,000 0.57 Not cost beneficial; Requires PWROG approval
67 Table 2.a.iv RAI Revised SAMA Phase II Analysis Results (Continued)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.0)
Revised September, 2011 SAMA RAI Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion Estimated Benefit Estimated Cost Benefit/
Cost Ratio Change in Conclusion 303 Move indication/ operator interface for starting hydrogen igniters to front MCR panel
$1,515
$50,000 0.03 Not cost beneficial
$1,727
$50,000 0.03 Not cost beneficial 304 Add annunciator or alarm signaling parameters to initiate hydrogen igniters to front panel on MCR
$1,515
$50,000 0.03 Not cost beneficial; HRA analysis considered procedure E-1 but not SAG-6, already implemented
$1,727
$50,000 0.03 Not cost beneficial; HRA analysis considered procedure E-1 but not SAG-6, already implemented 305 Revise procedure E-1 to include recovery steps for failure to initiate hydrogen igniters
$133,980 Not Estimated NA HRA analysis considered procedure E-1 but not SAG-6, already implemented
$152,737 Not Estimated NA HRA analysis considered procedure E-1 but not SAG-6, already implemented 306 Improve operator performance by enhancing likelihood of recovery from execution errors
$149,539 Not Estimated NA HRA analysis considered procedures ES-1.3 and FR-Z.1 but not SAG-6, already implemented
$170,474 Not Estimated NA HRA analysis considered procedures ES-1.3 and FR-Z.1 but not SAG-6, already implemented 307 Make provisions for connecting ERCW to CCP 2B-B
$531
$98,600 0.01 Not cost beneficial
$605
$98,600 0.01 Not cost beneficial Note 1 - SAMA 93 was revised (see RAI Response to Question 5.f). SAMA 300 was revised (see RAI Response to Question 5.i).
68 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 4
Improve DC bus load shedding.
1.11 1.96 Already committed to do, see
Increase training on response to loss of two 120V AC buses which causes inadvertent actuation signals.
0.41 0.74 Already committed to do, see
- January, 2009 SAMA submittal 0.47 0.85 Already committed to do, see January, 2009 SAMA submittal 26 Provide an additional high pressure injection pump with independent diesel.
0.02 0.03 NO 0.02 0.03 NO
69 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28) 32 Add the ability to automatically align emergency core cooling system to recirculation mode upon refueling water storage tank depletion.
0.17 0.29 NO 0.19 0.34 NO 45 Enhance procedural guidance for use of cross-tied component cooling or service water pumps.
0.14 0.26 NO 0.16 0.30 NO 46 Add a service water pump.
0.12 0.22 NO 0.14 0.25 NO 56 Install an independent reactor coolant pump seal injection system, without dedicated diesel.
0.13 0.23 NO 0.15 0.26 NO 70 Install accumulators for turbine-driven auxiliary feedwater pump flow control valves.
0.35 0.61 NO 0.39 0.70 NO
70 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 71 Install a new condensate storage tank (auxiliary feedwater storage tank).
0.00 0.00 NO 0.00 0.00 NO 87 Replace service and instrument air compressors with more reliable compressors which have self-contained air cooling by shaft driven fans.
0.00 0.00 NO 0.00 0.00 NO 93 Install an unfiltered, hardened containment vent.
0.35 0.61 NO 0.40 0.70 NO 101 Provide a reactor vessel exterior cooling system.
0.07 0.13 NO 0.08 0.14 NO 103 Institute simulator training for severe accident scenarios.
0.15 0.27 NO 0.18 0.31 NO
71 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 109 Install a passive hydrogen control system.
0.07 0.12 NO 0.08 0.14 NO 110 Erect a barrier that would provide enhanced protection of the containment walls (shell) from ejected core debris following a core melt scenario at high pressure.
0.08 0.14 NO 0.09 0.16 NO 112 Add redundant and diverse limit switches to each containment isolation valve.
0.00 0.01 NO 0.00 0.01 NO 136 Install motor generator set trip breakers in control room.
0.05 0.09 NO 0.06 0.10 NO
72 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 156 Eliminate RCP thermal barrier dependence on CCW, such that loss of CCW does not result directly in core damage.
21.66 38.10 NO.
Proposed procedure change ineffective.
See Section 10 of Oct.,
2010 SAMA report 24.70 43.44 NO.
Proposed procedure change ineffective.
See Section 10 of Oct.,
2010 SAMA report 176 Provide a connection to alternate offsite power source.
0.08 0.13 NO 0.09 0.15 NO 191 Provide self-cooled ECCS seals.
0.00 0.00 NO 0.00 0.00 NO 215 Provide a means to ensure RCP seal cooling so that RCP seal LOCAs are precluded for SBO events.
0.77 1.36 YES; first of a kind installation; downside impacts on risk impact not assessed 0.88 1.55 YES; first of a kind installation; downside impacts on risk impact not assessed 226 Permanent, self-powered pump to backup normal charging pump.
0.43 0.75 NO 0.49 0.86 NO
73 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 255 Permanent, Dedicated Generator for the NCP, one Motor Driven AFW Pump, and a Battery Charger.
0.23 0.40 NO 0.26 0.46 NO 256 Install Fire Barriers Around Cables or Reroute the Cables Away from Fire Sources.
49.22 87.01 Already committed to do, see
- January, 2009 SAMA submittal 56.11 99.19 Already committed to do, see
- January, 2009 SAMA submittal 276 Provide an auto start signal for AFW on loss of Standby Feedwater pump.
0.04 0.06 NO 0.04 0.07 NO 279 Provide a permanent tie-in to the construction air compressor.
0.07
.12 NO 0.08 0.14 NO 280 Add new Unit 2 air compressor similar to the Unit 1 D compressor.
0.08 0.14 NO 0.09 0.16 NO 282 Provide cross-tie to Unit 1 RWST.
0.00 0.00 NO 0.00 0.00 NO
74 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 285 Improve training to establish feed and bleed cooling given no CCPs are running or a vital instrument board fails 3.38 6.16 No (Remains Potentially cost beneficial) 3.85 7.02 No (Remains Potentially cost beneficial) 292 Improve training to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs 12.96 22.69 No (Remains Potentially cost beneficial) 14.78 25.87 No (Remains Potentially cost beneficial) 295 Increase frequency of containment leak rate testing 0.05 0.09 NO 0.06 0.10 NO 299 Initiate frequent awareness training for plant operators/
maintenance/
testing staff on key human actions for plant risk 9.35 16.51 No (Remains Potentially cost beneficial) 10.66 18.82 No (Remains Potentially cost beneficial)
75 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 300 Revise procedure FR-H.1 to eliminate or simplify complex (and/or) decision logic for establishing feed and bleed cooling and to improve operator recovery from initial mistake 0.50 0.91 YES; Requires PWROG approval 0.57 1.04 YES; Requires PWROG approval 303 Move indication/
operator interface for starting hydrogen igniters to front MCR panel 0.03 0.05 NO 0.03 0.06 NO 304 Add annunciator or alarm signaling parameters to initiate hydrogen igniters to front panel on MCR 0.03 0.05 NO 0.03 0.06 NO
76 Table 2.a.iv SAMA RAI 3% RDR Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion Benefit/
Cost Ratio 7% RDR Benefit/
Cost Ratio 3% RDR Change in Conclusion 305 Revise procedure E-1 to include recovery steps for failure to initiate hydrogen igniters Not Estimated NA NO Not Estimated NA NO 306 Improve operator performance by enhancing likelihood of recovery from execution errors Not Estimated NA NO Not Estimated NA NO 307 Make provisions for connecting ERCW to CCP 2B-B 0.01 0.01 NO 0.01 0.01 NO
77 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 4
Improve DC bus load shedding.
1.11 2.99 Already committed to do, see
- January, 2009 SAMA submittal 1.26 3.41 Already committed to do, see
- January, 2009 SAMA submittal 8
Increase training on response to loss of two 120V AC buses which causes inadvertent actuation signals.
0.41 1.10 Already committed to do, see
- January, 2009 SAMA submittal 0.47 1.26 Already committed to do, see
- January, 2009 SAMA submittal 26 Provide an additional high pressure injection pump with independent diesel.
0.02 0.04 NO 0.02 0.05 NO
78 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28) 32 Add the ability to automatically align emergency core cooling system to recirculation mode upon refueling water storage tank depletion.
0.17 0.45 NO 0.19 0.52 NO 45 Enhance procedural guidance for use of cross-tied component cooling or service water pumps.
0.14 0.39 NO 0.16 0.44 NO 46 Add a service water pump.
0.12 0.34 NO 0.14 0.38 NO 56 Install an independent reactor coolant pump seal injection system, without dedicated diesel.
0.13 0.35 NO 0.15 0.40 NO 70 Install accumulators for turbine-driven auxiliary feedwater pump flow control valves.
0.35 0.93 NO 0.39 1.06 NO 71 Install a new condensate storage tank (auxiliary feedwater storage tank).
0.00 0.00 NO 0.00 0.00 NO
79 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 87 Replace service and instrument air compressors with more reliable compressors which have self-contained air cooling by shaft driven fans.
0.00 0.01 NO 0.00 0.01 NO 93 Install an unfiltered, hardened containment vent.
0.35 0.95 NO 0.40 1.08 NO 101 Provide a reactor vessel exterior cooling system.
0.07 0.20 NO 0.08 0.22 NO 103 Institute simulator training for severe accident scenarios.
0.15 0.41 NO 0.18 0.47 NO 109 Install a passive hydrogen control system.
0.07 0.19 NO 0.08 0.22 NO
80 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 110 Erect a barrier that would provide enhanced protection of the containment walls (shell) from ejected core debris following a core melt scenario at high pressure.
0.08 0.21 NO 0.09 0.24 NO 112 Add redundant and diverse limit switches to each containment isolation valve.
0.00 0.01 NO 0.00 0.01 NO 136 Install motor generator set trip breakers in control room.
0.05 0.13 NO 0.06 0.15 NO 156 Eliminate RCP thermal barrier dependence on CCW, such that loss of CCW does not result directly in core damage.
21.66 58.49 NO.
Proposed procedure change ineffective.
See Section 10 of Oct.,
2010 SAMA 24.70 66.68 NO.
Proposed procedure change ineffective.
See Section 10 of Oct.,
2010 SAMA
81 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion report report 176 Provide a connection to alternate offsite power source.
0.08 0.20 NO 0.09 0.23 NO 191 Provide self-cooled ECCS seals.
0.00 0.00 NO 0.00 0.00 NO 215 Provide a means to ensure RCP seal cooling so that RCP seal LOCAs are precluded for SBO events.
0.77 2.08 YES; first of a kind installation; downside impacts on risk impact not assessed 0.88 2.37 YES; first of a kind installation; downside impacts on risk impact not assessed 226 Permanent, self-powered pump to backup normal charging pump.
0.43 1.15 Yes Potentially cost beneficial 0.49 1.32 Yes Potentially cost beneficial
82 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 255 Permanent, Dedicated Generator for the NCP, one Motor Driven AFW Pump, and a Battery Charger.
0.23 0.62 NO 0.26 0.70 NO 256 Install Fire Barriers Around Cables or Reroute the Cables Away from Fire Sources.
49.22 132.89 Already committed to do, see
- January, 2009 SAMA submittal 56.11 151.50 Already committed to do, see
- January, 2009 SAMA submittal 276 Provide an auto start signal for AFW on loss of Standby Feedwater pump.
0.04 0.10 NO 0.04 0.11 NO 279 Provide a permanent tie-in to the construction air compressor.
0.07 0.19 NO 0.08 0.21 NO 280 Add new Unit 2 air compressor similar to the Unit 1 D compressor.
0.08 0.21 NO 0.09 0.24 NO 282 Provide cross-tie to Unit 1 RWST.
0.00 0.00 NO 0.00 0.01 NO
83 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 285 Improve training to establish feed and bleed cooling given no CCPs are running or a vital instrument board fails 3.38 9.13 No (Remains Potentially cost beneficial) 3.85 10.41 No (Remains Potentially cost beneficial) 292 Improve training to reduce failure probability to terminate inadvertent safety injections prior to water challenge to PORVs 12.96 35.00 No (Remains Potentially cost beneficial) 14.78 39.90 No (Remains Potentially cost beneficial) 295 Increase frequency of containment leak rate testing 0.05 0.14 NO 0.06 0.16 NO 299 Initiate frequent awareness training for plant operators/
maintenance/ testing staff on key human actions for plant risk 9.35 25.24 No (Remains Potentially cost beneficial) 10.66 28.77 No (Remains Potentially cost beneficial)
84 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 300 Revise procedure FR-H.1 to eliminate or simplify complex (and/or) decision logic for establishing feed and bleed cooling and to improve operator recovery from initial mistakes 0.50 1.35 YES; Requires PWROG approval 0.57 1.54 YES; Requires PWROG approval 303 Move indication/ operator interface for starting hydrogen igniters to front MCR panel 0.03 0.08 NO 0.03 0.09 NO 304 Add annunciator or alarm signaling parameters to initiate hydrogen igniters to front panel on MCR 0.03 0.08 NO 0.03 0.09 NO 305 Revise procedure E-1 to include recovery steps for failure to initiate hydrogen igniters Not Estimated NA NO Not Estimat ed NA NO
85 Table 2.a.iv SAMA RAI 95% CDF Sensitivity Results (Continued)
SAMA Revised September 2011 Results (External Events Multiplier = 2.0)
SAMA Revised September 2011 Results (External Events Multiplier = 2.28)
SAMA No.
SAMA Title Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion Benefit/
Cost Ratio Mean CDF (Base Case)
Benefit/
Cost Ratio 95th%CDF Change in Conclusion 306 Improve operator performance by enhancing likelihood of recovery from execution errors Not Estimated NA NO Not Estimat ed NA NO 307 Make provisions for connecting ERCW to CCP 2B-B 0.01 0.01 NO 0.01 0.02 NO
86 Table 2.a.iv RAI Revised Evacuation Speed Sensitivity Results Base Case (2.2m/s)
Faster Evacuation (3.4m/s)
Slower Evacuation (1.6m/s)
Case Total Person-Rem Economic Cost ($)
Total Person-Rem Economic Cost ($)
Total Person-Rem Economic Cost ($)
I. Early 2.96E+06 6.34E+09 2.83E+06 6.34E+09 3.19E+06 6.34E+09 II. Bypass 2.39E+06 5.31E+09 2.35E+06 5.31E+09 2.46E+06 5.31E+09 III. Late 1.09E+06 3.19E+09 1.09E+06 3.19E+09 1.09E+06 3.19E+09 IV. SERF 3.22E+05 5.85E+08 3.16E+05 5.85E+08 3.34E+05 5.85E+08
87 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 308 Install automatic fire suppression in AB 757-A13 (refueling room)
Reduces frequency of fire scenarios in this room with or without manual suppression success FIVE contributors Maximum reduction in CDF is 7.46E-7 corresponding to about $84,000 benefit.
Excessive Implementation Cost 309 Install automatic fire suppression in AB 757-A22 ( 125v vital battery board room)
Reduces frequency of fire scenarios in this room with or without manual suppression success FIVE contributors Maximum reduction in CDF is 8.35E-7 corresponding to about $94,000 benefit.
Excessive Implementation Cost 310 Install automatic fire suppression in AB 786-AR (auxiliary building roof)
Reduces frequency of fire scenarios in this room with or without manual suppression success FIVE contributors Maximum reduction in CDF is 3.1E-7 corresponding to about $35,000 benefit.
Excessive Implementation Cost 311 Install automatic fire suppression for the main panels of the main control room CB 755-C12 Reduces frequency of fire scenarios in this room with or without manual suppression success FIVE contributors Maximum reduction in CDF is 9.65E-7 corresponding to about $108,000 benefit.
Excessive Implementation Cost
88 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 312 Install automatic fire suppression in areas of small ignition sources in the turbine building Reduces frequency of fire scenarios in this room with or without manual suppression success FIVE contributors Maximum reduction in CDF is 2.20E-7 corresponding to about $25,000 benefit.
Excessive Implementation Cost 313 Enhance fire department training and carry out drills for the 9 key rooms contributing the most to the sum of the FIVE CDF screening frequencies.
Reduces frequency of fire scenarios with or without manual suppression success FIVE contributors Maximum reduction in CDF is the sum of all sequence 4 contributions or 4.59E-6 corresponding to about
$516,000 benefit. See note (1)
Already Implemented 314 Enhance training for local control of AFW given station blackout, loss of control air, or fires affecting AFW LCVs.
Reduce probability of losing all secondary heat removal during station blackout.
FIVE contributors Per Table 15f, SAMAs previously identified are:
70, 73, 79, 282, 285, 299, and 300. SAMAs 285 and 299 previously committed to. Maximum reduction in CDF is the sum of all sequence 4 contributions or 3.89E-6 corresponding to about $437,000 benefit.
Already Implemented
89 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 315 Upgrade seals or enhance procedures to cooldown RCS before leakage Reduce probability of significant RCP seal leakage in event of losing all seal cooling and seal injection.
FIVE contributors Per Table 15e, applicable SAMAs previously identified are: 50, 58, 61, 155, 242, and 260. SAMAs 61 and 155 are already implemented. Maximum reduction in CDF is the sum of all sequence 4 contributions or 2.28E-6 corresponding to about
$256,000 benefit.
Already Implemented 316 Reroute offsite power cables away from fire area 737-A1A Reduce demands on onsite AC power system FIVE contributors 8kv power cables are expensive and difficult to locate. Maximum reduction in CDF is the sum of all sequence 4 contributions or 4.24e-7 corresponding to about $48,000 benefit.
Excessive Implementation Cost 317 Reroute offsite power cables away from fire area 737-A1B Reduce demands on onsite AC power system FIVE contributors 8kv power cables are expensive and difficult to locate. Maximum reduction in CDF is the sum of all sequence 4 contributions or 5.05e-7 corresponding to about $57,000 benefit.
Excessive Implementation Cost
90 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 318 Reroute offsite power cables away from fire area 737-A1C Reduce demands on onsite AC power system FIVE contributors 8kv power cables are expensive and difficult to locate. Maximum reduction in CDF is the sum of all sequence 4 contributions or 2.89e-7 corresponding to about $33,000 benefit.
Excessive Implementation Cost 319 Reroute onsite power cables to either SD BD 2A-A or 2B-B away from fire area 737-A1B Limit fire impact to just one train of SD BDs when also fail offsite power.
FIVE contributors 2PL6510A & 2PL6512A are the only 6-9kv SDBD 2A-A cables in 737-A1B and they are to be protected with fire wrap for Appendix R.
Maximum reduction in CDF is the sum of all sequence 4 contributions or 5.05e-7 corresponding to about
$57,000 benefit.
TVA implementation in process 320 Providing nitrogen bottles as accumulators for selected valves would reduce action difficulty. Enhance procedures already implemented, additional training could reduce error rate Reduce joint human error probability between recovery of AFW given loss of control air (HAFR1) and action to initiate feed and bleed cooling (HAOB2)
FIVE contributors Per Table 15f, SAMAs previously identified are:
70, 73, 79, 282, 285, 299, and 300. SAMAs 285 and 299 previously committed to. Maximum reduction in CDF is the sum of all sequence 4 contributions or 8.75e-7 corresponding to about $98,000 benefit.
Already Implemented
91 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 321 Reroute cables in fire area Aux Bldg 757-A22 to preclude failure of both trains of SD BDs (6.9kv SD BD 2B-B and 480v SD BDs on A train)
Limit fire impact to just one train of SD BDs FIVE contributors Maximum reduction in CDF is 8.35E-7 corresponding to about $94,000 benefit.
Excessive Implementation Cost 322 Reroute offsite power cables away from Aux Bldg 786-AR - auxiliary building roof Reduce demands on onsite AC power system FIVE contributors 8kv power cables are expensive and difficult to locate. Maximum reduction in CDF is 3.1E-7 corresponding to about
$35,000 benefit.
Excessive Implementation Cost 323 Enhance procedures for control room fire evacuation and associated procedures to achieve safe shutdown from shutdown panel Limit potential for operator error following evacuation FIVE contributors Plant abnormal operating instructions exits for fires in each room. AOI-30.2C.69 applies to these rooms.
Maximum reduction in CDF is 1.23E-6 corresponding to about $138,000 benefit.
Already Implemented 324 Reroute offsite power cables away from turbine building Reduce demands on onsite AC power system FIVE contributors 8kv power cables are expensive and difficult to locate. Maximum reduction in CDF is 5.92E-7 corresponding to about
$67,000 benefit.
Excessive Implementation Cost
92 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 325
- Provide an additional diesel generator - 2 MW blackout diesel generators to power charging pumps, igniters, Inverters, etc. SAMA 9
- Improve 6.9 kV bus crosstie capability.
SAMA 11,229,244
- Cross-tie diesel generators within or to the other units.
Improved reliability of onsite AC power sources.
Procedures already modified to add manual cross-tie capabilities FIVE contributors Per Table 15e, previously identified SAMAs are: 9, 10, 11, 12, 229, and 244. WBN is purchasing a 2MW blackout diesel generator for Unit 2. SAMAs 10, 11, and 12 are already implemented. Procedures for cross-tying 6.9 kV buses are available but conservatively not credited in the FIVE analyses. It is credited in the SAMA model for internal events.
Maximum reduction in CDF is 3.82E-7 corresponding to about $43,000 benefit.
Already Implemented
93 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 326
- Modify procedure to provide ability to align diesel power to more air compressors.
SAMA 86
- Provide a permanent tie-in to the construction air compressor. SAMA 279
- Add a new Unit 2 air compressor similar to Unit 1 D compressor. SAMA 280
- Replace the ACAS dryers and compressors.
SAMA 281 Improve availability of air system FIVE contributors Per Table 15e, SAMAs previously identified include 86, 188, 279, 280, and 281.
SAMAs 86, 188, 279 and 280 are not cost effective.
Maximum reduction in CDF is 7.22E-7 corresponding to about $81,000 benefit.
Already Implemented. A study has been initiated to see if it is practical to improve ACAS availability (SAMA 281).
94 Table 4.d-2 RAI SAMAs Identified for 18 Key Fire Scenarios from the FIVE Screening Analysis (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 327 Improve reliability of ERCW system failure in response to plant trip or limit the potential for seal leak given loss of all RCP seal cooling.
Pump improvements already implemented.
SAMAs identified to limit dependence on ERCW FIVE contributors Per Table 15a, SAMAs previously identified are:
46, 53, 56, 62, 155, 158, and 271. SAMAs 46 and 53 are not cost effective.
SAMAs 62,155, 158 and 278 are already implemented. Action HAERCW2 has been added to the SAMA model to allow for crosstie of the fire protection water to a failed ERCW system. The action can be accomplished within the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> available for most seal leakage rates.
For 480 gpm leak rates no credit is taken for the crosstie. The analysis to extend the time to CCS failure and to implement and refine the analysis is not cost effective.
Maximum reduction in CDF is 6.39E-8 corresponding to about $7,000 benefit.
Already Implemented Note (1)
95 The fire department at Watts Bar is a dedicated organization that responds to fires on site and maintains the majority of the fire protection equipment. The fire response organization is staffed and equipped for firefighting activities. The fire brigade is comprised of a fire brigade leader and four fire brigade members (minimum). The fire brigade shall not include the Shift Manager or the other members of the minimum shift crew necessary for safe shutdown of the unit, nor any personnel required for other essential functions during a fire emergency. Additional support is available when needed through an agreement with a local fire department (s). The fire brigade composition may be less than the minimum requirements for a period of time not to exceed two hours, in order to accommodate unexpected absence, provided immediate action is taken to fill the required positions.
The fire department already schedules quarterly fire drills for each rotating shift crew in specific fire areas. Each drill includes a formal critique to evaluate the effectiveness of the fire brigade in responding to a simulated fire emergency. The drills conducted have already included 8 of the 9 areas with relatively high screening values in the final FIVE screening analysis. The one area for which no drills have been conducted is AB 786 RA, which has minimal combustibles; i.e., less than 5 minute fire. Both announced and unannounced drills are conduced to fulfill NRC, OSHA, and NEIL training requirements. Abnormal operating instruction series AOI-30.2 is to direct the actions to be carried out for all Appendix R cooldowns. The steps required are listed as a function of the room in which the fire occurs. Further, fire pre-plans are developed for each fire area to facilitate fire fighting. These pre-plans contain the following types of information laid out on an easy to read room diagram; primary and secondary access routes, stairs and fire related barriers, safe shutdown equipment locations, hose stations, installed fire suppression systems, and locked access locations.
96 Table 5.c-1. October 2010, SAMA Model Release Categories, Frequencies, Doses, and Economic Costs SAM A
Release Category 1 - LERF Release Category 2 - BYPASS Release Category 3 - LATE Release Category 5 - SERF Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Base 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,614 3.84E-06 1.23E+0 0
$2,243 4
1.25E-06 3.70E+0 0
$7,929 3.45E-07 8.25E-01
$1,832 1.29E-05 1.40E+0 1
$41,231 3.81E-06 1.23E+0 0
$2,231 8
1.25E-06 3.71E+0 0
$7,963 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,608 3.82E-06 1.23E+0 0
$2,235 26 1.23E-06 3.65E+0 0
$7,827 3.50E-07 8.37E-01
$1,859 1.28E-05 1.40E+0 1
$40,944 3.81E-06 1.23E+0 0
$2,228 32 6.51E-07 1.93E+0 0
$4,134 3.50E-07 8.37E-01
$1,859 1.30E-05 1.41E+0 1
$41,506 2.36E-06 7.60E-01
$1,380 45 1.26E-06 3.72E+0 0
$7,970 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,586 3.83E-06 1.23E+0 0
$2,241 46 1.25E-06 3.70E+0 0
$7,924 3.49E-07 8.35E-01
$1,855 8.11E-06 1.36E+0 1
$39,797 3.77E-06 1.21E+0 0
$2,203 56 1.18E-06 3.48E+0 0
$7,459 3.50E-07 8.37E-01
$1,859 1.27E-05 8.82E+0 0
$25,891 3.21E-06 1.03E+0 0
$1,880 70 1.25E-06 3.70E+0 0
$7,936 3.48E-07 8.33E-01
$1,850 1.30E-05 1.38E+0 1
$40,449 3.79E-06 1.22E+0 0
$2,214 71 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,614 3.84E-06 1.23E+0 0
$2,243 87 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,592 3.83E-06 1.23E+0 0
$2,242 93 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,614 3.84E-06 1.23E+0 0
$2,243 101 6.14E-07 1.82E+0 0
$3,896 3.50E-07 8.37E-01
$1,859 1.32E-05 1.44E+0 1
$42,256 3.84E-06 1.23E+0 0
$2,243
97 Table 5.c-1. October 2010, SAMA Model Release Categories, Frequencies, Doses, and Economic Costs (Continued)
SAM A
Release Category 1 - LERF Release Category 2 - BYPASS Release Category 3 - LATE Release Category 5 - SERF Freq (per yr)
Dose Risk (man -
rem/yr)
Econom ic Risk
($/yr)
Freq (per yr)
Dose Risk (man
- rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Econo mic Risk
($/yr) 10 3
5.20E-07 1.54E+00
$3,299 3.42E-07 8.17E-01
$1,816 9.85E-06 1.07E+01
$31,464 1.49E-06 4.79E-01
$871 10 9
6.43E-07 1.90E+00
$4,078 3.50E-07 8.37E-01
$1,859 1.26E-05 1.37E+01
$40,212 3.84E-06 1.23E+00
$2,243 11 0
9.51E-07 2.82E+00
$6,037 3.50E-07 8.37E-01
$1,859 1.31E-05 1.43E+01
$41,825 3.84E-06 1.23E+00
$2,243 11 2
1.26E-06 3.72E+00
$7,971 3.42E-07 8.18E-01
$1,816 1.30E-05 1.42E+01
$41,614 3.84E-06 1.23E+00
$2,243 13 6
1.25E-06 3.71E+00
$7,954 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+01
$41,611 3.82E-06 1.23E+00
$2,234 15 6
1.19E-06 3.53E+00
$7,568 3.50E-07 8.37E-01
$1,859 9.70E-06 1.06E+01
$30,988 3.44E-06 1.11E+00
$2,011 17 6
1.14E-06 3.37E+00
$7,227 2.72E-07 6.50E-01
$1,445 1.05E-05 1.14E+01
$33,523 3.46E-06 1.11E+00
$2,025
98 Table 5.c-1. October 2010, SAMA Model Release Categories, Frequencies, Doses, and Economic Costs (Continued)
SAM A
Release Category 1 - LERF Release Category 2 - BYPASS Release Category 3 - LATE Release Category 5 - SERF Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr) 191 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,614 3.84E-06 1.23E+0 0
$2,243 215 1.16E-06 3.44E+0 0
$7,369 3.50E-07 8.37E-01
$1,859 7.78E-06 8.47E+0 0
$24,856 3.18E-06 1.02E+0 0
$1,860 226 1.16E-06 3.44E+0 0
$7,369 3.50E-07 8.37E-01
$1,859 7.78E-06 8.47E+0 0
$24,856 3.18E-06 1.02E+0 0
$1,860 255 1.05E-06 3.10E+0 0
$6,651 1.88E-07 4.50E-01
$1,001 1.05E-05 1.14E+0 1
$33,373 3.47E-06 1.12E+0 0
$2,026 256 9.42E-07 2.79E+0 0
$5,978 2.63E-07 6.28E-01
$1,396 9.77E-06 1.06E+0 1
$31,211 2.88E-06 9.26E-01
$1,682 276 1.25E-06 3.70E+0 0
$7,926 3.48E-07 8.32E-01
$1,849 1.30E-05 1.41E+0 1
$41,368 3.81E-06 1.23E+0 0
$2,231 279 1.25E-06 3.71E+0 0
$7,954 3.50E-07 8.35E-01
$1,856 1.28E-05 1.39E+0 1
$40,768 3.80E-06 1.22E+0 0
$2,223 280 1.25E-06 3.71E+0 0
$7,954 3.50E-07 8.35E-01
$1,856 1.28E-05 1.39E+0 1
$40,768 3.80E-06 1.22E+0 0
$2,223 282 1.25E-06 3.71E+0 0
$7,965 3.42E-07 8.18E-01
$1,816 1.30E-05 1.42E+0 1
$41,614 3.83E-06 1.23E+0 0
$2,238 285 1.25E-06 3.70E+0 0
$7,936 3.49E-07 8.34E-01
$1,852 1.30E-05 1.42E+0 1
$41,605 3.74E-06 1.20E+0 0
$2,186 292 5.97E-07 1.77E+0 0
$3,788 3.50E-07 8.37E-01
$1,859 1.29E-05 1.41E+0 1
$41,266 2.03E-06 6.54E-01
$1,189 295 1.26E-06 3.72E+0 0
$7,971 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,614 3.89E-09 1.25E-03
$2 299 1.23E-06 3.64E+0 0
$7,803 3.50E-07 8.37E-01
$1,859 1.19E-05 1.30E+0 1
$38,156 3.71E-06 1.19E+0 0
$2,169 300 1.25E-06 3.70E+0 0
$7,936 3.49E-07 8.34E-01
$1,852 1.30E-05 1.42E+0 1
$41,604 3.78E-06 1.22E+0 0
$2,209 303 1.25E-3.71E+0
$7,964 3.50E-8.37E-
$1,859 1.30E-1.42E+0
$41,589 3.84E-1.23E+0
$2,243
99 Table 5.c-1. October 2010, SAMA Model Release Categories, Frequencies, Doses, and Economic Costs (Continued)
SAM A
Release Category 1 - LERF Release Category 2 - BYPASS Release Category 3 - LATE Release Category 5 - SERF Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr)
Freq (per yr)
Dose Risk (man -
rem/yr)
Economi c Risk
($/yr) 06 0
07 01 05 1
06 0
304 1.25E-06 3.71E+0 0
$7,964 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,589 3.84E-06 1.23E+0 0
$2,243 305 9.06E-07 2.68E+0 0
$5,749 3.50E-07 8.37E-01
$1,859 1.29E-05 1.40E+0 1
$41,199 3.84E-06 1.23E+0 0
$2,243 306 9.07E-07 2.68E+0 0
$5,755 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,563 3.79E-06 1.22E+0 0
$2,218 307 1.26E-06 3.72E+0 0
$7,969 3.50E-07 8.37E-01
$1,859 1.30E-05 1.42E+0 1
$41,605 3.84E-06 1.23E+0 0
$2,243
0 RAI Response Submittal of May 13, 2011 TVAs responses to items 1 through 16 have been reviewed and concluded to be unchanged by correcting the total person-rem computed for each release category. With regard to item 12 (RAI 5.e), the previous response recognized that SAMA 70 would exceed a cost-benefit ratio of 1.0 if an uncertainty multiplier of 2.78 were assumed. This exceedance is now slightly greater because of the change correcting the total person-rem computed for each release category. This SAMA 70 has, however, been superseded by TVAs commitment to implement SAMA 339.
The list of commitments in enclosure 2 is also unchanged.
1 RAI Response Submittal of May 25, 2011 TVAs responses to items 2 through 3 have been reviewed and concluded to be unchanged by correcting the total person-rem computed for each release category.
The TVA response to item 5 has been reviewed and some discussion is offered to the response for part b. Correcting the total person-rem computed for each release category required a change to the maximum averted cost risk (MACR). The changes offered caused the SAMA 93 cost benefit ratio to go from just below 1.0 to slightly greater than 1.0 for the CDF 95th percentile sensitivity case. However, the potential benefits of implementing SAMA 93 are also addressed by SAMA 58. Hence, the existing commitment in enclosure 2 to the May 25, 2011 submittal adequately addresses this potentially cost beneficial SAMA.
Furthermore, the next highest benefit-cost ratio SAMA in the revised Table 2.a.iv-10, is SAMA 255 with a 95th percentile ratio of 0.70. If the 2.78 95th percentile multiplier is used instead of the 2.7, then SAMA 255 would have a benefit-cost ratio of 0.72.
Therefore, all remaining SAMAs are well below the 1.0 benefit-cost ratio using the 2.78 95th percentile multiplier and no other SAMA conclusions would change.
Part f of item 5 gives a breakdown of contributions to the MACR. This table is updated and presented below as Table 2.a.iv.f.
The response to item 15 (RAI 6) also involves changes to Tables 15-1 and 15-2. The updated tables are presented below. Table 15-3 summarizes a Phase 1 rescreening of the SAMAs which were screened because of Excessive Cost of Very Low Benefit. Table 15-3 has been reviewed in light of correcting the total person-rem computed for each release category and the conclusions found to be unchanged.
The list of commitments in enclosure 2 is also unchanged.
2 Table 2.a.iv-f from May 25, 2011 Submittal Cost Category October 2010, SAMA Report Revised September, 2011 (RAI) SAMA Results Off-Site Exposure Cost $
$514,379
$535,803 Off-Site Economic Cost $
$466,032
$720,324 On-Site Exposure Cost $
$8,153
$8,153 On-Site Economic Cost $
$666,023
$666,023 Total Base Cost $
$1,654,587
$1,930,303 Base Cost with External Event Multiplier 2.0
$3,309,174
$3,860,606 Base Cost with External Event Multiplier 2.28
$3,772,461
$4,401,090 Table 15 Revised RAI SAMA Maximum Averted Cost of Risk (MACR) Results Cost Description Revised September, 2011 (RAI) SAMA Results Total MACR MACR Onsite Costs (Function of Core Damage without Release Costs)
MACR Offsite Costs (Function of Core Damage and Release Costs)
Base Cost with External Event Multiplier 2.0
$ 3,860,606
$1,347,351 34.9%
$2,513,254 65.1%
Base Cost with External Event Multiplier 2.28
$4,401,090
$1,535,981 34.9%
$2,865,110 65.1%
95% Cost with External Multiplier 2.0 (95%
Multiplier 2.70)
$10,423,635
$3,637,849 34.9%
$6,785,786 65.1%
95% Cost with External Multiplier 2.28 (95%
Multiplier 2.70)
$11,882,944
$4,147,147 34.9%
$7,735,796 65.1%
3 Table 15-2. 95% MACR Risk Reduction Case Types SAMA Case CDF LERF (Early Bypass)
LATE SERF Contribution to MACR Potential Change in MACR 1
Changed Linear Linear Linear 100.0%
$11,882,944 2
Fixed Changed Fixed Fixed 13.2%
$1,564,242 3
Fixed Fixed Changed Fixed 48.6%
$5,779,353 4
Fixed Fixed Fixed Changed 3.3%
$389,118 5
Changed Changed Fixed Fixed 16.4%
$1,952,178 6
Changed Fixed Changed Fixed 75.1%
$8,927,170 7
Changed Fixed Fixed Changed 11.1%
$1,315,493
4 Table 15-3. Phase I SAMA Candidates SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 2 Replace lead-acid batteries with fuel cells.
Extended DC power availability during an SBO.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the cost of implementation caused by replacing all batteries with fuel cells, including structural, electrical, and HVAC changes required, including a fuel supply which does not currently exist on site, would exceed $2M and the bounding benefit would be less than 13% reduction in CDF. More complex technology with alternate fuel source requirements.
Combine with SAMA 174.
Excessive Implementation Cost. (Table 15-2 Case 1) 9 Provide an additional diesel generator.
Increased availability of on-site emergency AC power.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the cost of implementation ($8,500,000 to
$22,800,000, representative of similar nuclear power plants, WBN specific cost estimate $5,000,000) and benefit would be less than 28% reduction in CDF. WBN in process of updating cost estimate for non-SAMA reasons but expected to not be SAMA cost beneficial. Combine with SAMA 233.
Excessive Implementation Cost. (Table 15-2 Case 1)
5 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 13 Install an additional, buried off-site power source.
Reduced probability of loss of off-site power.
NEI 05-01 (Rev A)
Basis for Screening: There are two existing 161 kV connections to a nearby dam switchyard above ground. The estimated cost of burying them would exceed $5M and the benefit would be much less than 28% reduction in CDF. Pricing of above ground 161 kV line from hydro to construction yard was excessive. Buried would be even more.
Excessive Implementation Cost. (Table 15-2 Case 1) 14 Install a gas turbine generator.
Increased availability of on-site AC power.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($3,350,000 to $30,000,000, representative of similar nuclear power plants) would be much less than 28% reduction in CDF.
Based on cost of completion of 5th Diesel Generator, addition of turbine/gen with extra fuel source and building would be even more expensive.
Excessive Implementation Cost. (Table 15-2 Case 1) 15 Install tornado protection on gas turbine generator.
Increased availability of on-site AC power.
NEI 05-01 (Rev A)
Basis for Screening: A gas turbine generator is not available at the Watts Bar site. Based on cost of completion of 5th Diesel Generator, addition of turbine/gen with extra fuel source and building would be even more expensive.
Excessive Implementation Cost. (Table 15-2 Case 1) 24 Bury off-site power lines.
Improved off-site power reliability during severe weather.
NEI 05-01 (Rev A)
Basis for Screening: The distance that would be necessary to bury offsite power lines would be significant since severe weather to which transmission lines are susceptible typically affects a broad area.
Excessive Implementation Cost. (Table 15-2 Case 1)
6 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition For a plant with significant construction already completed, the estimated cost of implementation would exceed the potential benefit. Similar to #13 except two lines buried. Approx 2 miles underground duct bank and 161 underground cable. Benefit would be much less than 40% of CDF.
25 Install an independent active or passive high pressure injection system.
Improved prevention of core melt sequences.
NEI 05-01 (Rev A)
Basis for Screening: The previous passive UHI system was removed from the WBN design. For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit. Design basis safety reanalysis would be around $3M.
Engineering, construction, hardware, and testing costs would be in addition to that.
Total costs would greatly exceed $3M and bounding risk reduction benefit would be less than 25% reduction in CDF.
Excessive Implementation Cost. (Table 15-2 Case 1) 34 Provide an in-containment reactor water storage tank.
Continuous source of water to the safety injection pumps during a LOCA event, since water released from a breach of the primary system collects in the in-containment reactor water storage tank, and thereby eliminates the need to realign the safety injection pumps for long-NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit. There is limited room in containment to install an in-containment RWST. Complex engineering problem. Ice condenser currently acts as in-containment water source approx equal to the RWST after melt. Additional tank would reduce containment available volume for pressure Not Feasible to implement inside containment due to limited space available.
Will also screen on Excessive Cost. (Table 15-2 Case 1)
7 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition term post-LOCA recirculation.
suppression and raise post accident water level with additional post accident water level flooding issues.
37 Upgrade the chemical and volume control system to mitigate small LOCAs.
For a plant like the Westinghouse AP600, where the chemical and volume control system cannot mitigate a small LOCA, an upgrade would decrease the frequency of core damage.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation to increase CVCS flow capacity would exceed the bounding benefit. WBN currently has 2 trains of high head charging pumps. Additional charging pump would require additional power source and water supply. Recirculation from the sump would still be required.
Cost would exceed $2M and benefit would be much less than 10% reduction in CDF.
Excessive Implementation Cost. (Table 15-2 Case 1) 39 Replace two of the four electric safety injection pumps with diesel-powered pumps.
Reduced common cause failure of the safety injection system. This SAMA was originally intended for the Westinghouse-CE System 80+, which has four trains of safety injection.
However, the intent of this SAMA is to provide diversity within the high-and low-pressure safety injection systems.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation to replace the SI pumps would exceed the bounding benefit. Current SI pumps are Diesel backed. Diesel driven pumps would require a separate building along with appropriate protection (tornado, seismic, etc., and ASME piping into containment).
Excessive Implementation Cost. (Table 15-2 Case 1) 41 Create a reactor coolant Allows low pressure emergency core cooling NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, Excessive Implementation
8 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition depressurization system.
system injection in the event of small LOCA and high-pressure safety injection failure.
the estimated cost of implementation to install larger PORVs would exceed the bounding benefit. Would require ASME connections to the RCS and appropriately qualified valves and control circuits.
Safety analysis update including seismic RCS loop reanalysis would be required.
Cost would exceed $2M and benefit would be much less than 10% reduction in CDF.
Cost. (Table 15-2 Case 1) 55 Install an independent reactor coolant pump seal injection system, with dedicated diesel.
Reduced frequency of core damage from loss of component cooling water, service water, or station blackout.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Hardware, building, facilities support would be high cost. ASME, safety grade interface to CVCS. SAMA 56 (reactor coolant pump seal injection system without dedicated diesel) was screened out in Phase II evaluation. Would be considered with other Seal LOCA SAMAs.
Excessive Implementation Cost. (Table 15-2 Case 1) 77 Provide a passive, secondary-side heat-rejection loop consisting of a condenser and heat sink.
Reduced potential for core damage due to loss-of-feedwater events.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Potential change is less than 50% of CDF.
A passive heat removal system using air as the ultimate heat sink would be extremely large and expensive to install.
Excessive Implementation Cost. (Table 15-2 Case 1) 78 Modify the startup feedwater pump so Increased reliability of decay heat removal.
NEI 05-01 (Rev A)
Basis for Screening: Implementation of this SAMA requires a flow path around the Excessive Implementation
9 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition that it can be used as a backup to the emergency feedwater system, including during a station blackout scenario.
isolation valves. Also for use during a station blackout the Standby Feedwater pump would have to be powered from a diesel generator. For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Would require flowpath from condenser through hotwell pumps, through condensate system and around safety grade isolation valves (or alternate power source to reopen valves and power pumps).
Potential change is less than 50% of CDF.
Cost. (Table 15-2 Case 1) 90 Create a reactor cavity flooding system.
Enhanced debris cool ability, reduced core concrete interaction, and increased fission product scrubbing.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($8,750,000, representative of similar nuclear power plants) would yield a benefit of much less than 20% reduction in LERF.
Excessive Implementation Cost. (Table 15-2 Case 2 )
91 Install a passive containment spray system.
Improved containment spray capability.
NEI 05-01 (Rev A)
Basis for Screening: The source of this SAMA is the AP600 Design Certification Review submittal. For a plant with significant construction already completed, the cost of implementation ($20,000,000, representative of similar nuclear power plants) would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3) 94 Install a filtered containment vent to remove decay heat. Option 1:
Increased decay heat removal capability for non-ATWS events, with scrubbing of released NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($5,700,000, representative of similar Excessive Implementation Cost. (Table 15-2 Case 3)
10 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition Gravel Bed Filter Option 2: Multiple Venturi Scrubber fission products.
nuclear power plants) would not reduce all of the LATE consequences and would result in a benefit of less than 50%
reduction in LATE.
95 Enhance fire protection system and standby gas treatment system hardware and procedures.
Improved fission product scrubbing in severe accidents.
NEI 05-01 (Rev A)
Basis for Screening: Enhancements to the EGTS and ABGTS filters to provide scrubbing for ISLOCA source terms would exceed the bounding benefit. This system is not currently credited in the PSA and has limited capability for beyond design basis events due to filter loading concerns.
Upgrading the system for severe accidents would require a redesign with more capable equipment. EPSIL already contains instructions for spraying release points with fire water, which would provide fission product scrubbing. Costs would exceed expected benefit.
Excessive Implementation Cost. (Table 15-2 Case 2) 97 Create a large concrete crucible with heat removal potential to contain molten core debris.
Increased cooling and containment of molten core debris. Molten core debris escaping from the vessel is contained within the crucible and a water cooling mechanism cools the molten core in the crucible, preventing melt-through of the base mat.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($90,000,000 to $108,000,000, representative of similar nuclear power plants) would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3) 98 Create a core melt source reduction Increased cooling and containment of molten core NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, Excessive Implementation
11 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition system.
debris. Refractory material would be placed underneath the reactor vessel such that a molten core falling on the material would melt and combine with the material.
Subsequent spreading and heat removal from the vitrified compound would be facilitated, and concrete attack would not occur.
the estimated cost of implementation
($90,000,000, representative of similar nuclear power plants) would exceed the bounding benefit.
Cost. (Table 15-2 Cases 2 and 3) 99 Strengthen primary/secondary containment (e.g.,
add ribbing to containment shell).
Reduced probability of containment over-pressurization.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the cost of implementation would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3) 100 Increase depth of the concrete base mat or use an alternate concrete material to ensure melt-through does not occur.
Reduced probability of base mat melt-through.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the cost of implementation caused by reconstruction of the containment building would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and
- 3) 102 Construct a building to be connected to primary/secondary containment and maintained at a Reduced probability of containment over-pressurization.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the cost of implementation ($10,000,000 and up, representative of similar nuclear power plants) would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3)
12 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition vacuum.
105 Delay containment spray actuation after a large LOCA.
Extended reactor water storage tank availability.
NEI 05-01 (Rev A)
Basis for Screening: Delay of containment spray actuation would require reanalysis of safety analysis. Current safety analysis does not allow actuation delay. Cost of re-analysis and implementation would exceed the maximum benefit (<.0008 CDF)
Excessive Implementation Cost. Would require development and NRC approval of new gothic containment model and revised mass/energy release model.
Costs are excessive unless done through an Owners Group cost share with other ice condenser plants. (Table 15-2 Case 1) 106 Install automatic containment spray pump header throttle valves.
Extended time over which water remains in the reactor water storage tank, when full containment spray flow is not needed.
NEI 05-01 (Rev A)
Basis for Screening: The estimated cost of implementing a design change including reanalysis of the safety analysis is considered excessive cost compared to the risk benefit. Would require development and NRC approval of new gothic containment model and revised Excessive Implementation Cost. (Table 15-2 Case 1)
13 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition mass/energy release model. Benefit is less than 1% of CDF. Costs are excessive unless done through an Owners Group cost share with other ice condenser plants.
(proposal in progress) 115 Locate residual heat removal (RHR) inside containment.
Reduced frequency of ISLOCA outside containment.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($28,000,000, representative of similar nuclear power plants) would exceed the bounding benefit. Combine with SAMA 178.
Excessive Implementation Cost. (Table 15-2 Case 5) 119 Institute a maintenance practice to perform a 100% inspection of steam generator tubes during each refueling outage.
Reduced frequency of steam generator tube ruptures.
NEI 05-01 (Rev A)
Basis for Screening: The current cost of steam generator eddy current inspection is approximately $1million per steam generator. The cost of performing 100%
inspection including the cost of the added outage time would exceed the bounding benefit. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 120 Replace steam generators with a new design.
Reduced frequency of steam generator tube ruptures.
NEI 05-01 (Rev A)
Basis for Screening: The cost of replacing the steam generators at Watts Bar Unit 1 was $221,760,000. This exceeds the bounding benefit. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 121 Increase the pressure capacity of the secondary side so that a steam generator tube Eliminates release pathway to the environment following a steam generator tube rupture.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5)
14 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition rupture would not cause the relief valves to lift.
122 Install a redundant spray system to depressurize the primary system during a steam generator tube rupture.
Enhanced depressurization capabilities during steam generator tube rupture.
NEI 05-01 (Rev A)
Basis for Screening: Normal and auxiliary pressurizer spray capability is available in the current design. The estimated cost of implementation of a new pressurizer spray system would exceed the potential benefit.
SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. ASME safety grade connections to RCS and civil/DBA reanalysis would drive costs high.
(Table 15-2 Case 5) 125 Route the discharge from the main steam safety valves through a structure where a water spray would condense the steam and remove most of the fission products.
Reduced consequences of a steam generator tube rupture.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation of a new structure would exceed the bounding benefit. Installation of another structure, additional SRV tailpipe, and new SRVs, larger Steam Gen connections to accommodate additional piping pressure drops and remain inside the current safety analysis would be costly. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 126 Install a highly reliable (closed loop) steam generator shell-side Increased reliability of decay heat removal.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation of a water cooled isolation condenser would Excessive Implementation Cost. (Table 15-2 Case 5)
15 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition heat removal system that relies on natural circulation and stored water sources exceed the bounding benefit. Potential change is less than 50% of CDF. A passive heat removal system using water as the ultimate heat sink would be extremely large and expensive to install.
129 Vent main steam safety valves in containment.
Reduced consequences of a steam generator tube rupture.
NEI 05-01 (Rev A)
Basis for Screening: The estimated cost of design reanalysis and implementation of hardware changes would exceed bounding benefit. Implementation would also have negative consequences since the increase in containment pressure would result in containment isolation phase B which would empty the RWST. This would convert the event into a LOCA with consequential challenges. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 133 Install an ATWS sized filtered containment vent to remove decay heat.
Increased ability to remove reactor heat from ATWS events.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the potential benefit; i.e.
<.04 of CDF.
Excessive Implementation Cost. (Table 15-2 Case 1) 143 Upgrade fire compartment barriers.
Decreased consequences of a fire.
NEI 05-01 (Rev A)
Basis for Screening: Two and three hour regulatory required fire protection barriers are installed and maintained. Non regulatory required two hour fire barriers are also credited in IPEEE. For a plant with significant construction already completed, the estimated cost of upgrading to 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> fire barriers would exceed the Excessive Implementation Cost. (Table 15-2 Case 1)
16 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition potential benefit. Potential SAMAs for FIVE contributors were described in the response to RAI 4d.
166 Create a water-cooled rubble bed on the pedestal.
This rubble bed would contain a molten core dropping onto the pedestal, and would allow the debris to be cooled.
Cook Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation
($18,000,000, representative of similar nuclear power plants) would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3) 172 Increase containment design pressure.
Reduces chance of containment overpressure failures.
Cook Basis for Screening: For a plant with significant construction already completed, the cost of implementation caused by reconstruction of the containment building would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Cases 2 and 3) 211 Replace reactor vessel with stronger vessel.
Reduces core damage contribution due to vessel failure.
Cook Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Case 1) 214 Reinforce the seismic capacity of the steel structure supporting the auxiliary building.
Seismic failure of the steel structure supporting the auxiliary building would lead to collapse of the building. Reinforcing the building potentially precludes or lessens this failure mode.
Cook Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation to reinforce the auxiliary building to withstand beyond-design-basis earthquake levels would exceed the potential benefit.
Excessive Implementation Cost. (Table 15-2 Case 1) 233 Implement alternate AC power source.
The implementation of an alternate AC power source would most likely take the form of an additional EDG.
Vogtle Basis for Screening: The cost of installing an additional EDG has been estimated to be greater than $20 million in the Calvert Cliffs Application for License Renewal. It Excessive Implementation Cost. (Table 15-2 Case 1)
17 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition This SAMA would help mitigate LOSP events and would reduce the risk during time frames of on-line EDG maintenance.
The benefit would be increased if the additional DG could 1) be substituted for any current diesel that is in maintenance, and 2) if the diesel was of a diverse design such that CCF dependence was minimized.
was similarly estimated to be about
$26.09M for both units at Vogtle. As the per unit cost of approximately $10M to
$13M is greater than the Watts Bar maximum benefit, it has been screened from further analysis.
242 Permanent, Dedicated Generator for the NCP with Local Operation of TD AFW after 125V Battery Depletion.
This SAMA provides a means of limiting the size of a seal LOCA and providing primary side makeup through the installation of a diesel generator that can be rapidly aligned to the NCP from the MCR. Long term secondary side cooling can be provided through the operation of the turbine driven AFW pump using existing Wolf Creek procedures. This arrangement would make it Wolf Creek Basis for Screening: Local operation of the TDAFWP is currently proceduralized.
This requires a dedicated DG with auto start capability and auto transfer to meet the 13 minute criteria to prevent seal LOCA. Additionally the DG and Charging Pump lube oil cooling and seal cooling would require CCS and ERCW. The estimated cost of implementation of a dedicated DG would exceed the potential benefit. This SAMA will be considered with other Seal LOCA SAMAs under consideration if SAMA 58 is shown unreliable. See also SAMA 226.
Excessive Implementation Cost. (Table 15-2 Case 1)
18 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition possible to provide adequate core cooling in extended SBO evolutions.
253 Install SG Isolation Valves on the Primary Loop Side.
Installation of primary side isolation valves provides an additional means of isolating and controlling an SGTR event. These valves would also eliminate the need for local action to complete a steam generator isolation after a tube rupture has occurred.
Wolf Creek Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Would require ASME safety related piping and valves in additional to verification by analysis and testing of the increased flow resistance. Also seismic reanalysis of the RCS system. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 261 Guidance to align the C-S diesel generator.
In the event of a loss of offsite power followed by the failure of both shutdown boards on one unit, the procedures would be enhanced by adding the guidance to align the C-S diesel generator (i.e., the fifth diesel generator) to one of the shutdown buses not powered in the accident sequence due to the loss of a normally aligned diesel generator. This alignment could be accommodated by including a reference to the spare diesel generator in IPE Basis for Screening: The cost to refurbish, complete and license the spare 5th DG was estimated at ~2 to 3 million in 1996.
Currently the cost is estimated at $7 million plus labor. The potential benefit is much less than 20% reduction in CDF.
Procedures to align the portable DG have already been implemented.
Excessive Implementation Cost. See #9.
(Table 15-2 Case 1)
19 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition AOI 35, "Loss of Offsite Power."
270 Delay containment spray operation relative to phase B conditions.
From a severe accident point of view, one potential change, for consideration, would be the delaying of spray operations relative to the Phase B condition.
Currently, containment sprays actuate immediately in response to a Phase B condition, and air return fans (ARF) actuate after a 10 minute delay. This is currently a requirement of the design basis LOCA where switchover to containment spray recirculation occurs prior to ice melt; thereby limiting pressure increases below containment design pressure. Modular Accident Analysis Program analyses of representative core damage sequences indicate that actuation of the containment sprays while ice remains in the ice condenser has little impact IPE Basis for Screening: The current Watts Bar design basis calculations require sprays to initiate at containment phase B conditions.
This SAMA would require reanalysis of Safety analysis; and the benefit is less than 1% of CDF. Therefore it is considered cost prohibitive.
Excessive Implementation Cost. See #105.
(Table 15-2 Case 1)
20 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition on severe accident containment performance and may be detrimental in that operation of the sprays rapidly depletes the inventory of the RWST, making its contents unavailable for vessel injection. Since many scenarios have successful injection but failure at recirculation, the rapid depletion of the RWST due to spray operation accelerates the time to core damage. Therefore, an evaluation balancing the severe accident versus design basis requirements could be made.
274 Replace CCS pumps with positive displacement pumps.
Improves reliability of CCS system.
RRW Review Basis for Screening: PD pump removed from CVCS due to problems during initial testing on U1. WBN preference to avoid PD pumps on other systems. For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Case 1) 287 Increase 0.232 probability of hot Probability taken from analysis of Sequoyah in CAFTA IPE Basis for Screening: For a plant with significant construction already completed, Excessive Implementation
21 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition leg failure prior to Vessel breach given no temperature induced SGTR NUREG/CR-4551 the estimated cost of implementation would exceed the bounding benefit. A fundamental change in RCS piping design would be needed to materially change this probability, plus new safety analysis including civil analysis would be required.
Since this change would not reduce the core damage frequency, the expected benefit is limited.
Cost. (Table 15-2 Case 5) 288 Reduce 5.14E-2 probability of temperature induced SGTRs for SBO sequences with no secondary heat sink Probabilities taken from NUREG-1570 CAFTA IPE Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit. A fundamental change in RCS/SGTTR piping design would be needed to materially change this probability, likely including new steam generators. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 289 Reduce 3.81E-2 probability of temperature induced SGTRs for non-SBO sequences with no secondary heat sink Probabilities taken from NUREG-1570 CAFTA IPE Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit. A fundamental change in RCS/SGTTR piping design would be needed to materially change this probability, likely including new steam generators. SGTR IE reduction in CDF is very small.
Excessive Implementation Cost. (Table 15-2 Case 5) 290 Reduce probability of rocket mode and ex-vessel steam Probabilities taken from NUREG/CR-6427 CAFTA IPE Basis for Screening: For a plant with significant construction already completed, the estimated cost of implementation Excessive Implementation Cost. (Table
22 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition explosions causing early containment failure would exceed the bounding benefit. A fundamental change in Reactor vessel cavity design would be needed to materially change this probability.
15-2 Case 2) 5 Provide DC bus cross-ties.
Improved availability of DC power system.
NEI 05-01 (Rev A)
Basis for Screening: Since cross-ties are available at the 480V supplies, and the #5 spare battery can be aligned to and supply any of the 4 buses, this SAMA has very little risk benefit (<2% CDF) Combine with SAMA 258.
Very Low Benefit. (Table 15-2 Case 1) 16 Improve uninterruptible power supplies.
Increased availability of power supplies supporting front-line equipment.
NEI 05-01 (Rev A)
Basis for Screening: Four new inverters have been incorporated and a spare is already available. PRA modeling changes to realistically reduce the loss of 120V AC initiating event frequencies has greatly reduced the importance of these supplies.
Benefit is less than 0.1% of CDF.
Very Low Benefit. (Table 15-2 Case 1) 28 Add a diverse low pressure injection system.
Improved injection capability.
NEI 05-01 (Rev A)
Basis for Screening: See response to item 10, RAI 4.e.ii regarding the feasibility of a similar diverse low pressure injection system. For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Very Low Benefit. (Table 15-2 Case 1) 29 Provide capability for alternate injection via diesel-driven fire pump.
Improved injection capability.
NEI 05-01 (Rev A)
Basis for Screening: See response to item 10, RAI 4.e.ii regarding the feasibility of a similar diverse low pressure injection system. There is a minimal benefit from this SAMA since it does not provide a recirculation path. Therefore it is not Very Low Benefit. (Table 15-2 Case 1)
23 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition considered further. This SAMA is considered cost prohibitive relative to the potential benefit.
47 Enhance the screen wash system.
Reduced potential for loss of SW due to clogging of screens.
NEI 05-01 (Rev A)
Basis for Screening: The location of the intake on the river is protected from debris therefore there is minimal benefit of this SAMA (i.e. <1.6% CDF). Combine with SAMA 202 Very Low Benefit. (Table 15-2 Case 1) 50 Enhance loss of component cooling water procedure to underscore the desirability of cooling down the reactor coolant system prior to seal LOCA.
Reduced probability of reactor coolant pump seal failure.
NEI 05-01 (Rev A)
Basis for Screening: Upon receipt of any RCP seal no. 1 outlet temperature high alarm, AOI-15 & 24 require an RCS cooldown after isolation of the CCS path to the RCP thermal barrier and isolation of RCP seal injection. This order of actions is deemed appropriate for overall plant stabilization following a loss of CCS.
Enhanced procedure will not affect the risk because of the rapid progression of the seal leak. Therefore, the intent of this SAMA is minimal benefit. This SAMA may be considered with other Seal LOCA SAMAs in Phase II.
Very Low Benefit. (Table 15-2 Case 1) 53 On loss of essential raw cooling water, proceduralize shedding component cooling water loads to extend the component cooling Increased time before loss of component cooling water (and reactor coolant pump seal failure) during loss of essential raw cooling water sequences.
NEI 05-01 (Rev A)
Basis for Screening: AOI-13 for ERCW system loss or rupture does not provide directions to quickly implement loss of CCS procedure AOI-15 if ERCW cannot be restored. AOI-13, however, does provide directions to trip all of the RCPs, isolate thermal barrier cooling, cooldown the plant and cross-tie ERCW if available.
Very Low Benefit. (Table 15-2 Case 1)
24 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition water heat-up time.
There is minimal risk reduction for CCS load shedding since this is a timing issue for recovery of ERCW. The PRA model credits manual alignment of fire protection water to ERCW as a backup... Therefore this SAMA has very low risk improvement benefit.
79 Replace existing pilot-operated relief valves with larger ones, such that only one is required for successful feed and bleed.
Increased probability of successful feed and bleed.
NEI 05-01 (Rev A)
Basis for Screening: The Watts Bar success criteria for bleed and feed is two PORVs only if charging is not available.
Otherwise one PORV is sufficient. Larger valves would require piping changes, block valve changes, and analysis changes.
There is a larger probability of leakage with larger valves. Based on this, this SAMA provides little benefit for the estimated cost.
Very Low Benefit. (Table 15-2 Case 1) 80 Provide a redundant train or means of ventilation.
Increased availability of components dependent on room cooling.
NEI 05-01 (Rev A)
Basis for Screening: Provisions for compensatory ventilation is in place for the 480V electric board rooms and margin to room heatup limits exists in the 480V transformer room. Plant chillers are being upgraded based on Freon considerations.
TVA has committed to purchasing new temporary ventilation equipment. See the response to item 11, RAI 4.e.v. This SAMA is considered not cost beneficial due to low risk benefit.
Very Low Benefit. (Table 15-2 Case 1) 81 Add a diesel building high Improved diagnosis of a loss of diesel building NEI 05-01 (Rev A)
Basis for Screening: The diesel generator building is manned during DG starts, and Very Low Benefit. (Table
25 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition temperature alarm or redundant louver and thermostat.
HVAC.
shiftly operator rounds take temperature measurements per SI-2. Therefore this SAMA is considered very low benefit.
15-2 Case 1) 92 Use the fire water system as a backup source for the containment spray system.
Improved containment spray capability.
NEI 05-01 (Rev A)
Basis for Screening: Although there are two 2-inch test connections (72-545 &
544) that could be used to connect fire water to containment spray, this lineup bypasses the containment spray heat exchangers and would not remove containment heat. It also cannot recirculate water from the containment sump. The low flow rate would be ineffective for fission product removal.
Therefore this SAMA is considered very low benefit. Combine with SAMA 170.
Very Low Benefit. (Table 15-2 Case 1) 116 Ensure ISLOCA releases are scrubbed. One method is to plug drains in potential break areas so that break point will be covered with water.
Scrubbed ISLOCA releases.
NEI 05-01 (Rev A)
Basis for Screening: The cost of implementation of this SAMA has not been estimated in detail. A minimum value of $100K for a hardware change is assumed for screening purposes. Auxiliary building releases are scrubbed by the Aux Building Gas Treatment System (ABGTS);
however the ABGTS may not be sized for ISLOCA releases. RHR suction and discharge lines are in the overhead and therefore would not be submerged.
Contributes <0.1 % to LERF). Therefore this SAMA is considered very low benefit.
Combine with SAMA 237.
Very Low Benefit. (Table 15-2 Case 2) 124 Provide improved Improved mitigation of NEI 05-01 Basis for Screening: In the latest model, Very Low
26 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition instrumentation to detect steam generator tube ruptures, such as Nitrogen-16 monitors.
steam generator tube ruptures.
(Rev A) the contribution of steam generator tube ruptures to the core damage frequency is only.0001. For a plant with significant construction already completed, the estimated cost of implementation of rad monitors for each steam generator would exceed the bounding benefit.
Benefit. (Table 15-2 Case 5) 131 Add a system of relief valves to prevent equipment damage from pressure spikes during an ATWS.
Improved equipment availability after an ATWS.
NEI 05-01 (Rev A)
Basis for Screening: For a plant with significant construction already completed, the estimated cost of installing a relief valve system (likely well over $1million) is judged to be excessive relative to the risk benefit since ATWS accounts for only 3.8 % of the total internal event CDF.
Very Low Benefit. (Table 15-2 Case 1) 137 Provide capability to remove power from the bus powering the control rods.
Decreased time required to insert control rods if the reactor trip breakers fail (during a loss of feedwater ATWS which has rapid pressure excursion).
NEI 05-01 (Rev A)
Basis for Screening: Implementation of this SAMA would require reevaluation of the loss of the loads on the unit boards.
Training and procedure changes is estimated to cost more than the potential benefit. The contribution of ATWS to CDF is 3.8%. Of this fraction roughly 95% is attributable to RCS overpressurization events resulting from inadequate pressure relief within the first couple of minutes. The ability to remove holding power from the control rods would have to be under a time constraint of 1-2 minutes in order to affect the resulting peak pressures. This response time is not feasible and later response times would Very Low Benefit. (Table 15-2 Case 1)
27 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition have minimal benefit; i.e. about 0.2% of CDF. Therefore this SAMA is considered very low benefit.
147 Install digital large break LOCA protection system.
Reduced probability of a large break LOCA (a leak before break).
NEI 05-01 (Rev A)
Basis for Screening: The FVI of large break LOCAs to the core damage frequency is less than.0008. For a plant with significant construction already completed, the estimated cost of implementation would exceed the bounding benefit.
Very Low Benefit. (Table 15-2 Case 1) 152 Develop procedures for transportation and nearby facility accidents.
Reduced consequences of transportation and nearby facility accidents.
NEI 05-01 (Rev A)
Basis for Screening: An anti barge boom is installed at the intake structure to reduce transportation accidents. There are no identified hazardous barge shipments near the Watts Bar site. Therefore this SAMA is considered very low benefit.
Very Low Benefit. (Table 15-2 Case 1) 153 Install secondary side guard pipes up to the main steam isolation valves.
Prevents secondary side depressurization should a steam line break occur upstream of the main steam isolation valves. Also guards against or prevents consequential multiple steam generator tube ruptures following a main steam line break event.
NEI 05-01 (Rev A)
Basis for Screening: The FVI of all secondary side breaks, both inside and outside containment, in the current model is just.06. For a plant with significant construction already completed, the estimated cost of implementation (i.e.
much greater than $700k) would exceed the bounding benefit.
Excessive Implementation Cost. (Table 15-2 Case 1) 167 Enhance air return fans (ice condenser containment).
Provide an independent power supply for the air return fans, potentially reducing containment Cook Basis for Screening: 10 CFR 50.44 analysis shows these fans are a negligible contribution to the containment's ability to handle a hydrogen burn. Therefore this Very Low Benefit. (Table 15-2 Cases 2 and 3)
28 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition failure probability during SBO sequences.
SAMA is considered very low benefit.
183 Implement internal flood prevention and mitigation enhancements.
Options considered include
- 1) use of submersible MOV operators, and 2) back flow prevention in drain lines.
Cook Basis for Screening: The current modeling of flooding concerns in the WBN PRA does not indicate a vulnerability to this item. Therefore this SAMA is considered very low benefit.
Very Low Benefit. (Table 15-2 Case 1) 184 Implement internal flooding improvements identified at Fort Calhoun Station.
Implement improvements to prevent or mitigate 1) a rupture in the RCP seal cooler of the CCW system,
- 2) an ISLOCA in a shutdown cooling line, and
- 3) an AFW flood involving the need to possibly remove a watertight door.
For a plant where any of these apply, potentially reduces flooding risk.
Cook Basis for Screening: The current modeling of flooding concerns in the WBN PRA does not indicate a vulnerability to this item. Therefore this SAMA is considered very low benefit.
Very Low Benefit. (Table 15-2 Case 1) 199 Provide auxiliary building vent/seal structure.
Enhances ventilation in auxiliary building.
Cook Basis for Screening: Normal auxiliary building ventilation is not risk significant at Watts Bar unit 2. Therefore this SAMA is considered very low benefit.
Very Low Benefit. (Table 15-2 Case 1) 222 Establish a preventive maintenance program for expansion joints, bellows, and boots.
Potentially reduces flooding initiating event frequency and the failure probability of plant components.
Cook Basis for Screening: There is a limited use of expansion joints at Watts Bar and no indication of a vulnerability. Therefore this SAMA is considered very low benefit.
Very Low Benefit. (Table 15-2 Case 1) 225 Upgrade main Potentially reduces turbine Cook Basis for Screening: Since the turbine trip Very Low
29 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition turbine controls.
trip frequency.
initiator contributes less than 2% CDF and most turbine trips are not related to control problems, the estimated cost of implementation would exceed the minimal risk benefit from this SAMA. Therefore this SAMA is considered very low benefit.
Benefit. (Table 15-2 Case 1) 234 Implement automatic initiation of HPI on low RCS level (after AC power recovery).
The implementation of an automatic HPI initiation system would reduce the potential for core damage from occurring following events where ac power is recovered, but where a seal LOCA has already occurred. In these cases, RCS level must be restored to avoid core damage from occurring.
Vogtle Basis for Screening: The WBN design initiates HPSI on low RCS pressure which would result from an RCP seal LOCA.
The PRA model does not explicitly include operator actions to restore the pumps after AC power recovery since this sequence is dominated by non-recovery of AC power sources. Manual start of the pumps after AC power recovery is already proceduralized. Including this operator action would result in limited risk benefit and therefore is not analyzed further.
Very Low Benefit. (Table 15-2 Case 1) 254 Alternate Fuel Oil Tank with Gravity Feed Capability.
EDG failures related to failure of the fuel oil transfer pumps are currently considered to be unrecoverable in the PSA model. The installation of a large volume tank at an elevation greater than the EDG fuel oil day tanks would allow for emergency refill of the day tanks in the event of fuel oil transfer Wolf Creek Basis for Screening: Failure of the fuel oil transfer pumps contributes less than 1%
the internal event CDF based on RRW review. Improvements in the fuel oil transfer system are judged to be a minimal risk benefit. The cost of this enhancement has been previously estimated to be
$150,000 by Wolf Creek.
Very Low Benefit. (Table 15-2 Case 1)
30 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition pump failure.
262 Provide connections for centrifugal charging pumps to the ERCW system.
A potential improvement that could be evaluated is a plant change to provide connections for both centrifugal charging pumps, on both units, to the ERCW system for lube oil cooling in the event of a loss of CCS cooling to the associated pump.
Currently, this capability is only available for centrifugal charging pump A on Unit 1.
IPE Basis for Screening: The potential improvement was evaluated and there is low benefit to aligning a second charging pump to ERCW.
Very Low Benefit. (Table 15-2 Case 1) 273 Provide a redundant path for ECCS suction from the RWST around check valve 62-504.
Eliminates single failure potential of RWST check valve failure to open.
RRW Review Check valve 62-504 is a single failure point for ECCS injection but it contributes
<.00001 to CDF in the SAMA model. The cost of a design change, new hardware and analysis greatly exceeds the potential risk reduction benefit.
Very Low Benefit. (Table 15-2 Case 1) 277 Replace shutdown board chillers.
Improved reliability of shutdown board HVAC.
RRW Review Basis for Screening: The potential improvement was evaluated by reviewing the risk reduction worth (RRW) of the 6.9 kV board room ventilation and ventilation recovery. There is low benefit to these ventilation systems. However, these chillers are being upgraded and replaced for other reasons.
Very Low Benefit. (Table 15-2 Case 1) 284 Improve training Additional training may CAFTA MD and TD AFW pump isolation test Very Low
31 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition for MD AFW pump train A or B isolation tests reduce assigned error rate IPE restoration errors (WHEMDA_1, WHEDA_2, and WHEAFW) can impact AFW system reliability, especially under conditions of loss of a vital instrument bus or vital battery board. Human failure rate was re-evaluated substantially lower after initial identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator.
Revised contribution is much less than 0.1% of CDF. Estimated cost is $26,773 for enhanced training.
Benefit. (Table 15-2 Case 1) 286 Improve training to avoid a TD AFW isolation test error Additional training may reduce assigned error rate CAFTA IPE Human failure rate was re-evaluated substantially lower after initial identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator. Revised contribution is much less than 0.1% of CDF. Estimated cost is $26,773 for enhanced training.
Very Low Benefit. (Table 15-2 Case 1) 296 Improve training and procedures to respond to loss of both trains of AFW actuation signal Needed to address failure combinations of DC buses, vital instrument buses, and failures of SSPS.
CAFTA IPE Leading cutset involves common cause failure of safeguards actuation signal in a sequences where there is a plant trip without an SI condition (action HAOS3).
Event importance markedly reduced to less than 1% now that initiating event frequencies for loss of inverters and battery boards have been lowered.
Very Low Benefit. (Table 15-2 Case 1)
32 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition 297 Improve remote valve position indication in the MCR for MD AFW pump isolation valves Valve indication in MCR allows operators to check realignment CAFTA IPE Difficulty to inspect valves are more likely to be checked if indicated in MCR.
Human failure rate was re-evaluated substantially lower after initial identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator. Revised contribution is much less than 0.1% of CDF Very Low Benefit. (Table 15-2 Case 1) 298 Require added supervisory check to MD AFW pump train isolation valve test procedure Check is to be performed separately from (not concurrent to) the initial checks CAFTA IPE Human failure rate was re-evaluated substantially lower after initial identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator. Revised contribution is much less than 0.1% of CDF Very Low Benefit. (Table 15-2 Case 1) 301 Require added supervisory check to TD AFW pump train isolation valve test procedure Check is to be performed separately from (not concurrent to) the initial checks CAFTA IPE Human failure rate was re-evaluated substantially lower after initial identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator. Revised contribution is much less than 0.1% of CDF Very Low Benefit. (Table 15-2 Case 1) 302 Improve remote valve position indication in the MCR for TD AFW Valve indication in MCR allows operators to check realignment CAFTA IPE Difficult to inspect valves are more likely to be checked if indicated in MCR.
Human failure rate was re-evaluated substantially lower after initial Very Low Benefit. (Table 15-2 Case 1)
33 Table 15-3. Phase I SAMA Candidates (Continued)
SAMA Number SAMA Title SAMA Discussion Source Phase I Comments Disposition pump isolation valves identification of this SAMA to recognize that the error must occur on at least two steam generators rather than just the flow path to just 1 steam generator. Revised contribution is much less than 0.1% of CDF
34 RAI Response Submittal of June 17, 2011 TVAs responses in this submittal to items 1,2, 3 and 5 have been reviewed and concluded to be unchanged by correcting the total person-rem computed for each release category.
The response to item 4 is updated below in the form of revised tables to account for correcting the total person-rem computed for each release category. The methodology confirmed in the response is again confirmed here. However, the changed total person-rem computed for each release category does affect the tables provided in this response. Changes to Tables 2.a.iv-4, 2.a.iv-6 and 2.a.iv-4a are provided below. The updated tables account for the corrected person-rem values, a correction to the source term consequences for case Early 1B and a very minor change to the consequence results for Early case 1A.
35 Table 2.a.iv RAI Revised Source Terms for Eleven Release Category Cases Case Noble I
Cs Te Ba Sr Ru La Ce Frequency Early 1A 8.5E-01 2.2E-02 1.5E-02 1.7E-02 9.1E-03 1.4E-02 9.5E-03 8.4E-03 9.2E-03 35.0%
Early 1B 8.5E-01 1.0E-02 9.0E-03 1.3E-02 8.1E-03 1.4E-02 9.3E-03 8.1E-03 8.1E-03 30.0%
Early 2A 8.5E-01 1.3E-01 7.1E-02 5.5E-02 1.8E-02 1.6E-02 1.0E-02 1.1E-02 1.9E-02 20.0%
Early 2B 8.5E-01 3.2E-01 1.7E-01 1.3E-01 3.4E-02 1.9E-02 1.1E-02 1.6E-02 3.7E-02 15.0%
Bypass 8.5E-01 9.0E-02 4.9E-02 3.6E-02 1.1E-02 1.1E-02 7.2E-03 7.5E-03 1.2E-02 100.0%
Late 1A 8.5E-01 1.1E-02 6.7E-03 7.1E-03 2.7E-03 4.6E-03 2.5E-03 2.3E-03 2.8E-03 6.6%
Late 1B 8.5E-01 5.3E-03 3.7E-03 5.5E-03 2.6E-03 4.7E-03 2.5E-03 2.3E-03 2.6E-03 30.0%
Late 2A 8.5E-01 7.4E-03 4.8E-03 6.0E-03 2.5E-03 4.6E-03 2.5E-03 2.2E-03 2.6E-03 3.4%
Late 2B 8.5E-01 1.7E-02 9.2E-03 9.3E-03 3.3E-03 4.8E-03 2.5E-03 2.5E-03 3.4E-03 60.0%
SERF 1 8.5E-03 2.4E-04 2.6E-04 2.9E-04 3.0E-04 3.4E-04 3.2E-04 3.1E-04 3.0E-04 80.0%
SERF 2 8.5E-03 2.7E-03 2.1E-03 1.8E-03 1.6E-03 1.5E-03 1.5E-03 1.5E-03 1.6E-03 20.0%
36 Table 2.a.iv RAI Revised Doses and Economic Consequences for Eleven Release Category Cases Case Total Person-Rem Economic Cost, $
Early 1A 2.20E+06 4.66E+09 Early 1B 1.96E+06 4.23E+09 Early 2A 3.74E+06 7.97E+09 Early 2B 5.68E+06 1.23E+10 Bypass 2.39E+06 5.31E+09 Late 1A 1.09E+06 2.97E+09 Late 1B 8.99E+05 2.77E+09 Late 2A 9.52E+05 2.83E+09 Late 2B 1.19E+06 3.45E+09 SERF 1 2.47E+05 2.96E+08 SERF 2 6.21E+05 1.74E+09 Table 2.a.iv-4a - RAI Revised Weighted Source Terms for Four Release Category Cases Case Noble I
Cs Te Ba Sr Ru La Ce Early 8.5E-01 8.4E-02 4.7E-02 4.0E-02 1.4E-02 1.5E-02 9.9E-03 1.0E-02 1.5E-02 Bypass 8.5E-01 9.0E-02 4.9E-02 3.6E-02 1.1E-02 1.1E-02 7.2E-03 7.5E-03 1.2E-02 Late 8.5E-01 1.3E-02 7.2E-03 7.9E-03 3.0E-03 4.7E-03 2.5E-03 2.4E-03 3.1E-03 SERF 8.5E-03 7.3E-04 6.3E-04 6.0E-04 5.6E-04 5.8E-04 5.5E-04 5.5E-04 5.6E-04 RAI Response Submittal of June 27, 2011 The answer provided in this submittal is unchanged by correcting the total person-rem computed for each release category.