ML080780020
| ML080780020 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 03/18/2008 |
| From: | Kalyanam N NRC/NRR/ADRO/DORL/LPLIV |
| To: | Entergy Operations |
| Kalyanam N, NRR/DORL/LPL4, 415-1480 | |
| References | |
| TAC MD7061 | |
| Download: ML080780020 (5) | |
Text
March 18, 2008 Vice President, Operations Entergy Operations, Inc.
Waterford Steam Electric Station, Unit 3 17265 River Road Killona, LA 70057-3093
SUBJECT:
WATERFORD STEAM ELECTRIC STATION, UNIT 3 - REQUEST FOR ADDITIONAL INFORMATION ON THE REQUEST FOR ALTERNATIVE W3-ISI-005, REQUEST TO USE ASME CODE CASE N-716 (TAC NO. MD7061)
Dear Sir/Madam:
By letter dated October 18, 2007, as supplemented by letters dated November 30 and December 12, 2007, and February 14, 2008, Entergy Operations, Inc. (Entergy), submitted an application requesting the U.S. Nuclear Regulatory Commission (NRC) review an approval to implement a risk-informed inservice inspection (ISI) program based on American Society of Mechanical Engineers (ASME) Code Case N-716 at Waterford Steam Electric Station, Unit 3 (Waterford 3).
The NRC staff has reviewed your submittal and has determined that the additional information contained in the enclosure is needed to complete the review:
NRC discussed the need for additional information with your staff by telephone and they agreed to provide a response by March 26, 2007.
If you have any questions, please contact me at (301) 415-1480.
Sincerely,
/RA/
N. Kalyanam, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-382
Enclosure:
As stated cc w/encl: See next page
(*) No major change from Staff provided RAI OFFICE NRR/LPL4/PM NRR/LPL4/PM NRR/DRA/APLA NRR/LPL4/PM NAME NKalyanam JBurkhardt MRubin (*)
THiltz DATE 3/18/08 3/18/08 3/11/08 3/18/08
Waterford Steam Electric Station, Unit 3 (2/25/08) cc:
Senior Vice President Entergy Nuclear Operations P.O. Box 31995 Jackson, MS 39286-1995 Vice President, Oversight Entergy Nuclear Operations P.O. Box 31995 Jackson, MS 39286-1995 Senior Manager, Nuclear Safety
& Licensing Entergy Nuclear Operations P.O. Box 31995 Jackson, MS 39286-1995 Senior Vice President
& Chief Operating Officer Entergy Operations, Inc.
P.O. Box 31995 Jackson, MS 39286-1995 Associate General Counsel Entergy Nuclear Operations P.O. Box 31995 Jackson, MS 39286-1995 Manager, Licensing Entergy Operations, Inc.
Waterford Steam Electric Station, Unit 3 17265 River Road Killona, LA 70057-3093 Mr. Timothy Pflieger Environmental Scientist - Supervisor REP&R-CAP-SPOC Louisiana Department of Environmental Quality P.O. Box 4312 Baton Rouge, LA 70821-4312 Parish President Council St. Charles Parish P.O. Box 302 Hahnville, LA 70057 Chairman Louisiana Public Services Commission P.O. Box 91154 Baton Rouge, LA 70825-1697 Mr. Richard Penrod, Senior Environmental Scientist/State Liaison Officer Office of Environmental Services Northwestern State University Russell Hall, Room 201 Natchitoches, LA 71497 Resident Inspector Waterford NPS P.O. Box 822 Killona, LA 70057-0751 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011
REQUEST FOR ADDITIONAL INFORMATION WATERFORD STEAM ELECTRIC STATION, UNIT 3 REQUEST FOR ALTERNATIVE W3-ISI-005 USE OF ASME CODE CASE N-716 On March 6, 2008, Stephen Dinsmore from U.S. Nuclear Regulatory Commission (NRC) audited your recently completed flooding analysis. The flooding analysis was done to support the Waterford Steam Electric Station, Unit 3 (Waterford 3) February 14, 2008, request to implement a risk-informed inservice inspection (RI-ISI) program.
The audit compared your flooding analysis with the supporting requirements (SRs) identified in the American Society of Mechanical Engineers probabilistic risk assessment (ASME PRA)
Standard RA-Sb-2005. In general, consistency with the standard would satisfy the PRA quality requirements for supporting development of a RI-ISI program. However, since the PRA quality needs to be sufficient to support the proposed changes, if the appropriate capability category of the standard was not met, an evaluation was made as to whether the analysis was sufficient to support the proposed submittal. All SRs (except the documentation SRs) were evaluated during the audit. The NRC staff identified the following issues for resolution before it can reach a finding that the quality of the flooding analysis is sufficient to support the proposed application, i.e., that there is confidence that scenarios that exceed the quantitative guidelines are identified.
For clarity, the issues are listed according to the SR requirements.
- 1.
IF-C3 identifies the failure mechanisms that shall be evaluated to determine the susceptibility of each safety-related structure, system, and component (SSC) in a flood area to flood-induced failures. Capability category II identifies failure by submergence and spray as requiring detailed analysis. Capability category III includes jet impingement, pipe whip, and humidity, condensation, and temperature concerns.
Waterford 3 reported that it relied on its high-energy line break (HELB) design analysis to conclude that jet impingement, pipe whip, and humidity, condensation, and temperature concerns would not cause the failure of SSCs in a flood area. RI-ISI requires that all SSC failures induced by a pipe break be considered. Please demonstrate that all SSC failures that are induced by a pipe break are adequately addressed in your analysis.
- 2.
IF-C5 permits screening out of flood areas where flooding of the area does not cause an initiating event or a need for immediate plant shutdown and no mitigating equipment modeled in the PRA is failed. Waterford 3 reported that it screened out flood areas where flooding of the area did not cause an initiating event or did not require an immediate shutdown and only one train of mitigating equipment had failed. That is, if the flooding of an area failed only one train of mitigating equipment and also did not cause an initiating event or a need for immediate shutdown, the area was screened out and not further evaluated. As illustrated by the requirement across all capability categories for this SR in the Standard, even if the plant does not trip, a serious flooding event that fails important equipment is not acceptable. Please re-evaluate areas that were screened out because less than two trains of mitigating equipment had failed.
- 3.
IF-C6 permits screening out of flood areas based on, in part, the success of human actions to isolate and terminate the flood. Waterford 3 chose 20 or 30 minutes as the time when, if isolation was feasible, an operator would terminate the flood. Equipment damage was premised on the amount of water released during this time. This is a capability category I analysis. Crediting human actions is an integral but complex step in PRA. The endorsed RI-ISI methods require determination of the flood scenario with and without human intervention which corresponds to the capability category III, i.e.,
scenarios are not screened out based on human actions. Therefore, a capability category III analysis would be acceptable and is preferable. Capability category II permits screening based on high reliability of the required actions. If capability category II is used, the human error probabilities should be quantified using methods consistent with the IF-E5 in the standard. Please re-evaluate the credit given to human actions to provide confidence that scenarios that might exceed the quantitative guideline are identified.
- 4.
IF-C8 permits screening out flood sources based, in part, on human actions analogous to IF-C6 above which dealt with flood areas. The comment provided for IF-C6 also applies to IF-C8.
- 5.
IF-D5a addresses the development of flood initiating (pipe rupture) frequencies for use during the scenario development. Capability category I permits the use of generic operating experience. The combined capability category II and III requires collection and incorporation of plant-specific experience. Waterford 3 reported that they collected plant-specific pipe failure experience, but this emphasized actual, and unlikely, failures.
Pipes tend to fail where degradation mechanisms exist and RI-ISI is premised on inspecting locations with the highest risk, driven mostly by failure frequency. The plant-specific information collected and used should include experience related to degradation mechanisms that could indicate increased likelihood of pipe failure at particular locations. Waterford should re-assess its plant-specific operating experience to identify experience related to degradation mechanism and incorporate any relevant experience in the development of pipe failure frequencies.
- 6.
IF-E5a addresses human actions developed in the internal PRA that are carried over into the flooding analysis by using the internal events sequences to quantify the flooding sequences. Waterford 3 stated that it had not reviewed these human actions from the internal event PRA to ensure that they are still feasible given the flooding event that caused the flooding sequence. Please re-evaluate the credit given to these human actions to provide confidence that scenarios that might exceed the quantitative guideline are identified.
- 7.
IF-E7 requires a review of the large early release frequency (LERF) sequences used in the internal event PRA to ensure that they remain applicable when carried over into the analysis of the flooding sequences. Waterford stated that it did not perform a LERF analysis. The RI-ISI guidelines for identifying high-safety significant sequences used by Waterford require that LERF be considered and any piping that contributes to LERF sequences greater than 1E-7/year be placed in the high-safety significant category.
Please re-evaluate your results to identify as high-safety significant any sequences that result in an estimated LERF greater than 1E-7/year.