ML17229B002
| ML17229B002 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 12/15/1998 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| Shared Package | |
| ML17229A999 | List: |
| References | |
| NUDOCS 9902040124 | |
| Download: ML17229B002 (15) | |
Text
ATTACHMENT STAFF EVALUATIONREPORT INDIVIDUALPLANT EXAMINATIONOF EXTERNALEVENTS (IPEEE} SUBMITTAL ON ST. LUCIE NUCLEAR POWER STATION UNITS 1 AND 2 qiOa040<Z4 9eataS*
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STAFF EVALUATIONREPORT OF INDIVIDUALPLANT EXAMINATIONOF EXTERNALEVENTS (IPEEE) SUBMITTAL ON ST. LUCIE NUCLEAR POWER STATION UNITS 1 AND 2 I.
INTRODUCTION On June 28, 1991, the NRC issued Generic Letter 88-20, Supplement 4 (with NUREG-1407, Procedural and Submittal Guidance) requesting all licensees to perform individual plant examinations of external events (IPEEE) to identify plant-specific vulnerabilities to severe accidents and to report the results to the Commission together with any licensee-determined improvements and corrective actions.
On September 8, 1992, the licensee, Florida Power and Light Company (FPL), submitted a seismic analysis for St. Lucie Unit 1 by Stevenson and Associates to resolve Unsolved Safety Issue (USI) A-46 (Generic Letter (GL) 87-02, "Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors" ). This analysis was also used to address the seismic aspects of the IPEEE.
In a letter dated December 15, 1994, the licensee submitted the rest of its IPEEE to the NRC.
The staff contracted with Energy Research, Inc. (ERI) to conduct a Step 1 review of the licensee's IPEEE submittal and its associated documentation in March 1995 and sent a request for additional information (RAI) to the licensee on September 13, 1995. The licensee responded to the RAI on January 9, 1996.
Based on the results of the review, the staff concluded that the aspects of seismic; fire; and high winds, floods, transportation, and other external events were adequately addressed.
The review findings are summarized in the evaluation section below. Details of the contractor's findings are presented in the technical evaluation report attached to this staff evaluation report.
In accordance with Supplement 4 to GL 88-20, the licensee has provided information on Fire Risk Scoping Study (FRSS) issues, generic safety issue (GSI)-57, "Effects of Fire Protection System Actuation of Safety-Related Equipment," GSI-103, "Design for Probable Maximum Precipitation (PMP)," and USI A<5, "Shutdown Decay Heat Removal Requirements" which.were explicitly requested in Supplement 4 to GL 88-20 and its associated guidance in NUREG-1407. The licensee did not propose to resolve any additional USls or GSls as part of the St. Lucie IPEEE.
II.
EVALUATION The St. Lucie Nuclear Plant is a two-unit, Combustion Engineering 2-loop pressurized-water reactor (PWR) located about 12 miles southeast of Ft. Pierce, Florida. St. Lucie Unit 1 was designed to a seismic acceleration level of 0.1g peak ground acceleration (PGA) anchored to a Housner spectral shape. St. Lucie Unit 2 was designed to a seismic acceleration level of 0.1g PGA anchored to a Regulatory Guide 1.60 spectral shape.
With respect to the seismic IPEEE, St. Lucie is assigned to the reduced-scope seismic review category in NUREG-1407.
However, the licensee used a site-specific seismic program associated with USI A<6 (GL 87-02, "Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors" ) to address the seismic aspects of the IPEEE. For fire events, the licensee has used the Electric Power Research Institute's (EPRI) fire-induced vulnerability evaluation (FIVE) methodology and performed an extensive walkdown of the plant.
For the analyses of other external events, the licensee used the progressive screening procedure as described in NUREG-1407.
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CoreDama eFre uenc CDF Estimate The licensee did not provide a CDF estimate related to seismic events.
Instead, the licensee used a walkdown that focused on component anchorage capability and the potential for adverse seismic-induced spatial interactions.
Regarding the fire analysis, the licensee estimated that the total fire CDF is about 1.9x10"/reactor-year (RY) for Unit 1, and about 1.2<10"/RY for Unit 2. The CDF for control room fires is about 7.5x10'/RY for Unit 1, and about 5.9<10'/RY for Unit 2. For the cable spreading rooms, the CQFs were determined to be 7x10'/RY and 5.6<10'/RY for Units 1 and 2, respectively. The CDF for a fire in the "B"switchgear room was concluded to be 4.3<10'/RY and 4.5~10~/RY for Units 1 and 2, respectively.
The licensee also estimated that the contributions to CDF from high wind, flood, and other external (HFO) events are insignificant at St. Lucie. The CDF due to internal events is about 2.3x10'/RY for Unit 1 and 2.6<10'/RY for Unit 2, including internal flooding.
Dominant Contributors Based on the plant-speciTic seismic adequacy evaluation for St. Lucie, the licensee identified several components as seismic outliers which were mostly related to anchorage/support concerns.
The licensee has proposed or implemented relevant plant improvements or resolution procedures to address the identified outliers.
In addition, the seismic review team documented some cases of poor seismic "housekeeping" during seismic walkdowns.
The staff notes that there are several minor weaknesses in the licensee's seismic submittal. The licensee selected only one success path, namely, the loss of offsite power scenario, whereas NUREG-1407 recommends two success paths (one pertaining to a small break loss-of-coolant accident (LOCA)) for a reduced-scope plant.
In addition, the licensee did not mention non-seismic failures and human actions that might compromise the integrity of the chosen success path. The staff believes that the impact of these weaknesses appears to be minimal because the seismic risk at St. Lucie is perceived to be low.
An extensive walkdown of the plant was conducted using EPRI's FIVE methodology to support the analysis.
Based on the screening results, the licensee screened out all the fire areas with the exception of three areas, which include the control rooms, cable spreading rooms, and "B" train switchgear rooms. This screeniiig was based on either: (a) a lack of safe shutdown, equipment in a given area; or (b) an estimated fire-induced CDF of less than 10~/RY for a given area.
The licensee identified the most significant human action is to use the cross-tie breaker to provide power from one unit to the other unit.
'The licensee concluded that potential core damage scenarios due to HFO events have an extremely low frequency in comparison to CDF from other initiators. However, the licensee enhanced administrative procedure Number 0005753, "Severe Weather Preparations," based on the lessons learned from, Hurricane Andrew, that passed directly over Turkey Point.
Containment Performance The licensee has not conducted an IPEEE containment performance seismic walkdown for St. Lucie.
Since St. Lucie is a reduced-scope plant, and its containment is designed for the safe shutdown earthquake (SSE), it is unlikely that a seismic event would have a significant impact on the containment performance at St. Lucie. The staff concludes that not conducting a seismic walkdown on containment performance is a weakness in the licensee's IPEEE; however, the staff does not believe that the licensee missed any significant containment seismic vulnerabilities.
The licensee examined the potential for containment bypass for fire-initiated events and concluded that fire initiators do not alter the containment bypass scenarios analyzed in the IPE.
In addition, the licensee examined containment isolation scenarios and conluded that the failure to isolate the containment due to loss of actuation signal or spurious opening of the isolation valves does not affect the containment performance analysis as modeled in the IPE. The licensee's containment performance analyses for internal fire events appeared to have considered important severe phenomena and are consistent with the intent of Supplement 4 to Generic Letter 88-20.
Generic Safet Issues As a part of the IPEEE, a set of generic and unresolved safety issues (USI A<5, GSI-57, GSI-103, GSI-131, and the Sandia Fire Risk Scoping Study (FRSS) issues) were specifically identified during the initial planning of the IPEEE program and explicitly discussed in Supplement 4 to GL 88-20 and its associated guidance in NUREG-1407 as needing to be addressed in the IPEEE. The staffs evaluation of these issues is provided below.
1.
USI A<5, "Shutdown Decay Heat Removal (DHR) Requirements" The licensee selected a success path needed to accomplish one method of decay heat removal following a fire or a seismic event.
The staff finds that the licensee's USI A<5 evaluation is consistent with the guidance provided in Section 6.3.3.1 of NUREG-1407, and therefore the staff considers. this issue resolved.
2.
GSI-57, "Effects of Fire Protection System Actuation on Safety-Related Equipment" The licensee noted that for fire protection systems protecting safety-related equipment, seismic consideration and requirements were addressed in the plant change/modification packages associated with fire suppression system installation. Essentially, the II/I criteria (namely, falling objects due to failure of Class II (non-safety) sytems in a seismic event impacting the Class I
(safety) systems) were applied to fire protection systems whose failure could affect the operation of safety-related systems.
However, the staff finds a weakness in the licensee's GSI-57 evaluation.
The staff notes that the effects of seismic-induced actuation of fire protection system on safety-related equipment were not addressed.
The licensee stated that seismic-fire interactions were not included in the walkdowns.
Because of the apparent weakness in the=
submittal, the staff can not conclude that GSI-57 is fullyresolved.
3.
GI-103, "Design for Probable Maximum Precipitation" The licensee has assessed GSI-103 and concluded that the new Probable Maximum Precipitation (PMP) criteria will not have any impact on St. Lucie. The staff finds that the licensee's, GI-103 evaluation is consistent with the guidance provided in Section 6.2.2.3 of NUREG-1407, and therefore the staff considers this issue resolved.
4.
GSI-131, "Potential Seismic Interaction Involving the Movable In-Core Flux Mapping System Used in Westinghouse Plants" P
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St. Lucie is a Combustion Engineering design; therefore GSI-131 does not apply-to St. Lucie.
5.
Fire Risk Scoping Study Issues The licensee's IPEEE submittal and other associated documentation were reviewed for information directly addressing the following external events-related FRSS issues: fire-induced alternate shutdown/control room panel interaction (Section 4.8 Item 6 of IPEEE); and adequacy of fire barriers (Section 4.8 Item 3 of IPEEE).
Based on the results of the IPEEE submittal review, the staff considers that the licensee's process is capable of identifying potential vulnerabilities associated with these FRSS issues.
However, the staff identified weaknesses in the licensee's submittal regarding the following three FRSS issues:
(i)
Regarding the seismic-fire interactions, the licensee stated that seismic-fire interactions were not included in the walkdowns.
This issue is closely related to GSI-57 discussed above.
(ii)
Regarding the effects of fire protection system actuation on safety-related equipment, the licensee did not provide any discussion of potential adverse effects on plant equipment by spurious suppression system actuation.
This issue is closely related to GSI-57 discussed.
above.
(iii)
Regarding the issue of smoke control and manual fire-fighting effectiveness, the staff noted that manual fire fighting was not credited in the analysis.
Therefore, manual fire-fighting effectiveness is not addressed in the submittal. This issue is the same as GSI-148 discussed below.
In addition to those safety issues discussed above that were explicitly requested in Supplement 4 to GL 88-20, four generic safety issues were not specifically identified as issues to be resolved under the IPEEE program; thus, they were not explicitly discussed in Supplement 4 to GL 88-20 or NUREG-1407.
However, subsequent to the issuance of the generic letter, the NRC evaluated the scope and the specific information requested in the generic letter and the associated IPEEE guidance, and concluded that the plant-specific analyses being requested in the IPEEE program could also be used, through a satisfactory IPEEE submittal review, to resolve the external event aspects of these four safety issues.
The following discussions summarize the staffs evaluation of these safety issues at St. Lucie.
GSI-147, "Fire-Induced Alternate Shutdown/Control Room Panel Interactions" The licensee's response to the staff's request for additional information (RAI) contains
. information addressing this issue.
The licensee has considered the occurrence of loss of offsite power and reactor coolant pump (RCP) seal failure from a fire-induced event.
The licensee noted that the circuits for the alternate shutdown panel are isolated from the circuits whose routing passes through or terminates in the control room. Therefore, the staff considers that the licensee's process is capable of identifying potential vulnerabilities associated with this issue.
On the basis that no vulnerability associated with this issue was identified in the IPEEE submittal, the staff considers this issue resolved.
2.
GSI-148, "Smoke Control and Manual Fire-Fighting Effectiveness"
I The staff noted that manual fire-fighting was not credited in the analysis.
Therefore, manual fire-fighting effectiveness is not addressed in the submittal. The staff considers this issue not resolved.
3.
GSI-156, "Systematic Evaluation Program (SEP)"
St. Lucie is not an SEP plant. Therefore, this issue is not applicable.
4.
GSI-172, "MultipleSystem Responses Program (MSRP)"
I The licensee's IPEEE submittal and associated documentation were reviewed for information directly addressing the following external events-related MSRP issues: seismically induced spatial and functional interactions (Section 4.7 of the Stevenson report); non-safety-related control system/safety-related system dependencies (Section 4.7 of the Stevenson report); and effects of flooding and/or moisture intrusion on non-safety related and safety-related equipment (Sections 5.2 of IPEEE). Based on the fact that no vulnerabilities were identified, the staff considers these MSRP issues resolved.
In addition, the staff considers that the following MSRP issues are resolved for St. Lucie for the reasons given below:
(i)
In accordance with Table 7.17.2 of NUREG-1407, for reduced-scope plants (i.e., sites where the seismic hazard is low), the NRC recommendations for relay chatter review are the same as the Nuclear Management and Resources Council (NUMARC) recommendations, namely, performing an A<6 review, and not performing additional review for IPEEE relays.
Since St. Lucie is a reduced-scope plant and has performed an A-46 review for Unit 1, no additional review of relay chatter is needed for St. Lucie.
(ii)
In accordance with Section 3.2.4.5 of NUREG-1407, reduced-scope plants should use the safe shutdown earthquake (SSE) ground response spectra in their seismic margins methodology.
Therefore, evaluation of an earthquake greater than the SSE did not need to be addressed for St. Lucie, which is a reduced-scope plant.
(iii)
Regarding the effects'of hydrogen. line ruptures, it appears that the licensee used the FIVE walkdown verification checklist to identify any flammable liquid nr gas storage vessels or piping. Even though the effects of hydrogen line ruptures were not explicitly discussed, the licensee identified compressed hydrogen as a potential explosion source.
Ouring our review, the staff was unable to find any specific reference to all or part of the following five MSRP issues:
(i)
Regarding the seismic-fire interactions, the licensee stated that seismic-fire interactions were not included in the walkdowns.
This issue is closely related to GSI-57 discussed above.
(ii)
Regarding the effects of fire protection system actuation on safety-related equipment, the licensee did not provide any discussion of potential adverse effects on plant equipment by spurious suppression system actuation.
This issue is closely related to GSI-57 discussed above.
C (iii)
Regarding the IPEEE-related aspects of common cause failures associated with human errors, human errors occuring as part of recovery actions during certain fire scenarios were addressed in the submittal; however, the licensee provided a very limited discussion of operator recovery actions following a seismic event.
(iv)
The issue of seismically induced flooding was not addressed in the submittal.
(v)
Regarding the issue of seismically induced fire suppression system actuations, the licensee provided limited information of its assessment of seismic-induced multiple fire suppression system actuations which may in turn cause failures of redundant trains of safety-related systems.
This issue is part of GSI-57 discussed previously in this SER.
Based on the overall results of the staffs IPEEE submittal review, with the possible exception of the five MSRP issues discussed above, the staff considers that the licensee's process is capable of identifying potential vulnerabilities associated with GSI-172. The need for any additional assessment or actions related to the resolution of these five issues for St. Lucie will be addressed by the NRC staff separately from the IPEEE program.
For the MSRP issues that were addressed, on the basis that no potential vulnerability associated with these issues were identified in the IPEEE submittal, the staff considers the IPEEE-related aspects of these issues to be resolved.
Plant Safet Features Potential Vulnerabilities and Im rovements The licensee rep'orted the following safety features at the plant:
1.
The major plant structures were designed to withstand the wind loading, flying debris, and storm surge associated with hurricanes and tornados.
2.
Since the plant is located on the ocean shore, it is not subject to lengthy periods of external flooding as is the case for inland plants on rivers and lakes.
3.
Since the climate at the plant site is tropical, equipment is unlikely to freeze following a winter storm. The water at the intake structure is very unlikely to freeze and cause a loss of heat sink event.
4.
Feedwater can be provided by main feedwater (MFW) and AFW. MFW remains functional following a unit trip unless failed by the initiator (e.g., loss of grid, feedline break). The decay heat removal (DHR) capability is enhanced by the ability to provide once-through-cooling using high pressure safety injection (HPSI) pumps and power-operated relief valves (PORVs).
5.
St. Lucie has an automatic switchover for HPSI suction from the refueling water tank (RWT) to the containment sump.
6.
The RCP seal design is not susceptible to gross failure ifthe pumps'are secured within 10 minutes following a loss of RCP seal cooling.
7.
The containment design is such that water first flows to the containment sump which then overflows into the reactor cavity, thus providing a source of cavity flooding during many accident scenarios.
8.
There are no lower head penetrations in the reactor pressure vessel (RPV) thus eliminating those as potential locations for RPV failure.
The licensee's IPEEE submittal did not explicitly provide a definition of severe accident vulnerability.
However, the licensee's Individual Plant Examination (IPE) defined a vulnerability as: (1) a failure which makes a disproportionately large contribution to the total CDF or significant release probabilities and, in turn, is considered significantly higher than those of PRAs for similar plants, or (2) a failure which has any unusual and significant impact on the total CDF or release probabilities.
The licensee did n'ot identify any potential severe accident vulnerabilities related to seismic, fire, or HFO events.
's a result of the A46 program, the licensee made several significant improvements including improvements to anchorages, maintenance actions, and implementation of a strict housekeeping policy. Specifically, for St. Lucie Unit 1, five anchorages and the component cooling water (CCW) surge tank platform were identified as concerns by the seismic review team (SRT). In addition to these five anchorage concerns, six additional anchorage concerns were identified by FPL for similar components in different equipment trains. The licensee has proposed modification for the identified concerns.
The licensee also noted the following seismic interaction concerns at Unit 1:
1
~
Potential interaction involving the glass site tube for the CCW surge tank.
Based on a system review performed by FPL, the licensee determined that the tank could still perform its function even ifthe site glass broke. Therefore, the glass site tube was not modified or replaced.
2.
Potential interaction involving a block wall adjacent to the CCW surge tank The licensee indicated that FPL intended to verify that the block wall had previously been adequately addressed in the IE 80-11 program.
3.
An overhead crane adjacent to the intake cooling water pump should be secured away from the pump.
The licensee indicated that FPL intended to verify that the crane was properly parked or positioned.
In addition, some cases of poor seismic "housekeeping" were. observed and documented.-ln response to the NRC's USI A<6 review process, the licensee is implementing a program of strict seismic housekeeping.
For St. Lucie Unit 2, the licensee identified the following seismic interaction concerns:
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1.
One concern pertains to possible tipping of transformer PP236 which is mounted on a block wall above a 480 volt motor control center (MCC). The licensee's seismic review team (SRT) recommended that a strap/band could be placed around the transformer.
2.
Other concerns pertained to instances where the SRT recommended that a check of anchorage and support related to transformers mounted above cabinets should be performed, and it was indicated that FPL'ngineering would perform the needed checks.
Furthermore, the peer review by the licensee resulted in the following additional findings which have been addressed:
1.
Secure load center over-cabinet crane/winches, and verify that the tool box cart in the switchgear room is either removed or properly secured.
2.
Secure or remove instrumentation and control (l&C) locker from the control room.
3.
Reduce battery rack end gaps on the 2A and 2B batteries.
I 4.
Implement control-room housekeeping improvements regarding storage of Scott Air Packs and immobilizing an unsecured locker.
In the fire area, the licensee identified the following corrective actions to improve plant safety:
1.
Revise procedures to cross-tie power between the two units to further increase the availability of power to the fire-affected unit under certain fire scenarios.
2.
Revise the current fire protection procedures to ensure that a roll-up door between the two 4.16 kV buses is kept closed in each of the turbiine generator building switchgear rooms.
3.
Either protect or reroute a control cable for 2A5 load center in the "B" switchgear room.
With respect to HFO events, the licensee developed the following procedural improvement:,
1.
The administrative procedure Number 0005753, "Severe Weather Preparations," was revised to better prepare operators to weather a storm, based on the lessons learned from Hurricane Andrew that passed directly over Turkey Point Nuclear Plant in August 1992.
III.
CONCLUSIONS On the basis of the above findings, the staff notes that the IPEEE results are reasonable given the St. Lucie plant design, operation, and history. Therefore, the staff concludes that the licensee's IPEEE process is capable of identifying the most likely severe accidents and severe accident vulnerabilities, and therefore, that the St. Lucie IPEEE has met the intent of Supplement 4 to Generic Letter 88-20 and the resolution of specific generic safety issues discussed in this SER.
As indicated in Section II of this SER, there are three issues under the Fire Risk Scoping Study, five issues under the Multiple System Response Program (MSRP/GSI-172), and GSI-148 that the licensee did not appear to address in its submittal.
In addition, GSI-57 is addressed in part, but is not fullyresolved.
Of these ten unresolved issues, there are really six distinct issues which are discussed in Section II. The need for any additional assessment or actions related to the resolution of these issues for St. Lucie willbe addressed by the staff separately from the IPEEE program.
It should be noted that the staff focused its review primarily on the licensee's ability to examine St.
Lucie for severe accident vulnerabilities. Although certain aspects of the IPEEE were explored in more detail than others, the review was not intended to validate the accuracy of the licensee's detailed findings (or quantiTication estimates) that underlie or stemmed from the examination.
Therefore, this SER does not constitute NRC approval or endorsement of any IPEEE material for purposes other than those as'sociated with meeting the intent of Supplement 4 to GL 88-20 and the resolution of specific generic safety issues discussed in this SER.
1 C
Attachment ST. LUCIE NUCLEAR PLANT UNITS 1 AND 2 INDlYIDUALPLANT EXAMINATIONOF EXTERNALEVENTS
{lPEEE)
TECHNICALEVALUATIONREPORT