ML18057B202
| ML18057B202 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 08/01/1991 |
| From: | Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-68578, NUDOCS 9108120242 | |
| Download: ML18057B202 (7) | |
Text
consumers Power POWERINli M.ICHlliAN'S PROliRESS Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 August 1, 1991 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -
STATION BLACKOUT ANALYSIS; SAFETY EVALUATION (TAC NO. 68578)
GB Slade General Manager The May 20, 1991 Safety Evaluation Report on the Palisades Plant Station Blackout Analysis made several recommendations to enhance compliance with the Station Blackout (SBO) rule and requested a 30 day response to inform the staff when the recommendations would be completed.
By agreement with the NRC Palisades Project Manager, the 30 day response time did not begin until a July 2, 1991 telephone conference was held to clarify the interpretation of those recommendations.
The attachment to this letter contains Consumers Power Company's response to recommendations made in the May 20, 1991 Safety Evaluation Report.
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Gerald B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment A CMS ENERGY COMPANY (l()S°O lj1
ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 STATION BLACKOUT EVALUATION RESPONSE TO NRC SAFETY EVALUATION RECOMMENDATIONS 5 Pages
PALISADES NUCLEAR PLANT STATION BLACKOUT EVALUATION
- RESPONSE TO NRC SAFETY EVALUATION RECOMMENDATION On May 20, 1991, the NRC issued a Safety Evaluation Report (SER) for the Palisades Plant Station Blackout Analysis. The SER contained several recommendations which required resolution. The purpose of this document is to provide Palisades resolution of each of the recommendations identified in the SER and, where applicable, to provide a schedule for implementation of these recommendations.
The recommendation and its response provided below are numbered consistent with the numbering provided in the NRC Safety Evaluation.
2.2.2 Class IE Battery Capacity The licensee initially stated that the Palisades Plant Class IE batteries have sufficient capacity to meet station blackout for four hours assuming loads not needed to cope with a station blackout are stripped.
In a subsequent correspondence on November 7, 1990, the licensee submitted the battery analysis and excerpts from the Emergency Operating Procedure (EOP) related to the stripping of the loads from the batteries. After reviewing the available information, the staff agrees with the SAIC assessment in the Technical Evaluation Report (TER) that there are two areas of concern.
First, the battery load profile figure indicates a larger load shedding than the loads identified in the procedure (see TER).
Second, the licensee assumes that load shedding will begin 10 minutes into the SBO event which is contrary to the guidance provided in NUMARC 87-00, Section 7.2.2, which states that loads can be stripped commencing 30 minutes after the initiation of the station blackout event.
Recommendation:
The licensee should not consider load stripping to occur until 30 minutes into the event, verify that the battery load profile envelopes the resulting load requirements, and confirm the battery adequacy for the four hour coping duration and recovery thereafter. Also, the licensee needs to verify that the correct aging and temperature factors recommended in IEEE Std-485 have been applied.
The revised results should be reflected in the appropriate plant procedures and included in the SBO submittal supporting documents.
Response
The Palisades Battery Analysis does not assume that manual load stripping occurs until 30 minutes into the event.
The battery load reduction which occurs between 1 and 10 minutes on the battery load profile is due to the dropping out of short duration loads (eg relays which remain energized until a valve strokes to its final position, emergency sirens, etc). These short duration loads are conservatively assumed to be energized for the first 10 minutes of the event.
The manual load shedding is shown on the battery load profile at 30 minutes into the event.
Plant procedures for the station blackout event list battery loads to be shed which are consistent with this battery analysis.
Further, the battery analysis for Palisades does use the correct aging and temperature factors recommended in IEEE-Std-485.
2 2.2.4 Effects of Loss of Ventilation The licensee stated that heating, ventilation, and air conditioning (HVAC}
would not be available during a SBO event.
The licensee calculated the maximum bulk ambient temperature of the main control room and the containment and conducted tests to determine the temperature in the auxiliary feed water (AFW}, the cable spreading, and the switchgear rooms.
The results of these tests and the calculations were provided in the licensee submittals.
After reviewing the supporting documentation and SAIC's TER, the staff agrees with the licensee's stated results except in the following areas:
(l} the control room, (2} battery room, and (3} cable spreading room.
The staff concurs with SAIC's assessment of the deficiencies as identified in Attachment 1 for the above mentioned areas.
Recommendation:
The licensee should reevaluate the effect of loss of ventilation for the areas identified in this section, specifically in the control room where the licensee used a non-conservative initial temperature and used two different values for the thermal conductivity of concrete in the heat-up calculations. The licensee also should ensure that, in the cable spreading and battery rooms, at least one DC-powered fan will be available to each area after the load shedding process is complete or perform heat-up calculations of these rooms representative of expected room conditions and associated operating equipment during a SBO event. Also, the licensee needs to verify that the loss of heat tracing during a SBO event would not degrade the operation of safe shutdown systems.
The licensee should include the results of the evaluations and confirmations in the supporting documentation that is to be maintained by the licensee.
Response
Regarding the control room HVAC, Palisades will reevaluate the effect of a loss of ventilation for this room assuming a 90°F initial temperature.
90°F is consistent with a Technical Specification limit on control room temperature which is currently being developed. This reevaluation will also correct the value of thermal conductivity utilized in the analysis. This reevaluation is expected to be complete by December 31, 1991.
By reducing the conservative values of heat input utilized in the existing calculation, we are confident that the revised calculation will continue to show that the control room will remain below 120°F during a SBO event of four hours duration.
The battery room at Palisades would be subject to a complete loss of HVAC during a Station Blackout.
No detailed evaluation of the effects of the loss of ventilation has been performed for this room.
The battery rooms are located adjacent to the cable spreading room which has been shown to remain below its design temperature of 104°F for a loss of ventilation of up to six hours duration.
The only heat source available in the battery rooms is the heating due to internal battery resistance which is considered to be insignificant. The battery room temperature is thus expected to follow closely the cable spreading room temperature and to remain below 104°F for the duration of a SBO event.
During loss of ventilation testing for the cable spreading room, it was determined that certain cabinets required forced cooling to maintain cabinet internal temperatures below their design limits. Subsequent to this testing, fans were installed internal to these cabinets to provide this forced cooling capability. These fans are powered from DC-backed sources and will be
available to cool the required cabinets and internal equipment during a SBO event.
3 An evaluation of the effects of the loss of heat tracing durtng a SBO of four hour duration has been performed.
The only area of concern is the concentrated boric acid tanks and associated piping. This heat tracing system would be lost during a SBO.
A calculation has been performed which indicates that the temperature of the fluid in these components will remain above the precipitation temperature of the boric acid for the duration of a four hour SBO event.
2.2.5 Containment Isolation The licensee's initial submittal stated that the plant list of containment isolation valves (CIVs) had been reviewed to verify that valves which must be capable of being closed or that must be operated (cycled) under SBO conditions can be positioned (with indication) independent of the preferred and blackout Unit's Class IE AC power supplies. The licensee also stated that no motor-operated valves are necessary for containment isolation and no plant modifications or procedure changes are required to ensure appropriate containment integrity under SBO condition.
After reviewing the SAIC TER and list of isolation valves (UFSAR, Table 6-6),
the staff concurs with the SAIC TER that there are several valves which do not meet the exclusion criteria outlined in RG 1.155.
Recommendation:
The licensee should list in an appropriate procedure all CIVs that cannot be excluded by the exclusion criteria outlined in RG 1.155 (valves that are either normally closed or open and fail as is upon loss of AC power).
The procedure should identify the actions necessary to ensure that these valves are fully closed, if needed.
The staff's position is that the valve closure needs to be confirmed by position indication (local, mechanical, remote, process information, etc.). This information should also be included with the other documentation that is to be maintained by the licensee in support of the SBO submittals.
Response
Palisades has reviewed the plant list of containment isolation valves and has verified that these valves either meet the exclusion criteria of RG 1.155 or are capable of being closed from the control room under SBO conditions.
The containment isolation valves which are required to be confirmed closed are addressed in appropriate emergency operating procedures.
These valves are confirmed to be in the closed position by procedure if containment pressure begins to increase.
The two valves identified by SAIC as not meeting the exclusion criteria of RG 1.155 are normally closed and fail closed during a SBO.
The valves are air operated (with a backup N2 accumulator) with DC solenoids and also have DC powered position indication.
The valves are further backed up by a check valve or locked closed manual valve which do meet the exclusion criteria of RG 1.155.
2.4 Proposed Modifications The licensee stated that the coping duration of four hours was determined after accounting for modifications to provide an additional source of off-site power to the plant. These modifications have been completed and were declared operational in the fall of 1989.
The licensee also will add back-up compressed-air supplies to support the operation of the atmospheric dump
valves (ADVs) during a SBO.
These additions will be completed within two years from completion of the NRC review of the Palisades SBO evaluation in accordance with 10 CFR 50.63 (c)(3).
4 Recommendation:
The licensee should include a full description, including the nature and objectives of the required modifications identified above, in the documentation that is to be maintained by the licensee in support of the SBO submittals.
Response
Descriptions of the modifications described above will be available as part of the documentation maintained in support of the SBO submittals. The modification to add back-up compressed air supplies to the atmospheric dump valves will be completed by the end of the second refueling outage after January 1, 1992.
This refueling outage is currently scheduled to begin in May, 1993.
2.5 Quality Assurance and Technical Specifications The licensee did not specifically address Quality Assurance (QA) programs or Technical Specifications (TS) for the SBO equipment.
The technical specifications for the SBO equipment are currently being considered generically by the NRC in the context of the Technical Specification Improvement Program and remains an open item at this time.
However, the staff expects that the plant procedures will reflect the appropriate testing and surveillance requirements to ensure the operability of the necessary SBO equipment.
If the staff later determines that TS regarding the SBO equipment are warranted, the licensee will be notified of the implementation requirements.
Recommendation:
The licensee should verify that the SBO equipment is covered by an appropriate QA program consistent with the guidance of RG 1.155. This evaluation should be documented as part of the documentation supporting the SBO rule response.
Response
With the exception of the back-up air supply to the atmospheric dump valves (ADV) being installed as part of a future modification, no non-safety-rel ated equipment is used to meet the station blackout requirements of 10 CFR 50.63.
Design and installation of the ADV back-up air supply modification will be available as part of the documentation supporting the SBO rule response.
2.6 EDG Reliability Program The licensee stated that an EDG reliability program similar to that required by NUMARC 87-00 has been in place for some time at the Palisades Plant, and that the target reliability of 0.95 was selected based on an average reliability greater than 0.90 for the last 20 demands, greater than 0.94 for the last 50 demands, and greater than 0.95 for the last 100 demands.
The submittal did not specifically address the commitment to implement an EDG reliability program to conform to the guidance of RG 1.155, Position 1.2.
Recommendation:
It is the staff's position that an EDG reliability program should be developed in accordance with the guidance of RG 1.155, Section 1.2.
If an EDG reliability program currently exists, the program should be evaluated and adjusted in accordance with RG 1.155. Confirmation that such a program is in place or will be implemented should be included in the
documentation that is to be maintained by the licensee in support of the SBO submittals.
Response
Palisades currently has implemented programs which track and maintain Emergency Diesel Generator (EOG) Reliability. These programs incorporate the elements identified in Regulatory Guide 1.155 Section 1.2.
Details of the EOG Reliability Program are subject to change following resolution of Generic Issue B-56, "Diesel Generator Reliability."
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