ML18054A703

Forwards Response to Station Blackout Rule Re Ability of LWR Plants to Withstand & Recover from Station Blackout,Per Reg Guide 1.155, Station Blackout. Mods & Associated Procedure Changes Will Be Completed by End of Next Refueling Outage

ML18054A703
Person / Time
Site:	Palisades
Issue date:	04/17/1989
From:	Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.155, RTR-REGGD-1.155 NUDOCS 8905010231
Download: ML18054A703 (6)

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consumers Power Kenneth W Berry POWERIN& Director Nuclear Licensing MICHl&AN'S PRO&RESS General Offices: 1945 West Parnall Road, Jackson, Ml 49201 * (517) 788-1636 April 17, 1989 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT RESPONSE TO STATION BLACKOUT RULE 10CFR50.63 On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regula-tions in 10CFR, Part 50. A new section, 50.63, was added which requires that each light-water-cooled nuclear power plant be able to withstand and recover from a station blackout (SBO) of a specified duration. Utilities are expected to have the baseline assumptions, analyses and related information used in their coping evaluation available for NRC review. Section 50.63 also identi-fies the factors that must be considered in specifying the station blackout duration. This section requires that, for the station blackout duration, the plant be capable of maintaining core cooling and appropriate containment integrity. Section 50.63 further requires that each licensee submit the following information:

1. A proposed station blackout duration including a justification for the selection based on the redundancy and reliability of the onsite emergency AC power sources, the expected frequency of loss of offsite power, and the probable time needed to restore offsite power;

2. A description of the procedures that will be implemented for station blackout events for the duration (as determined in 1 above) and for recov-ery therefrom; and

3. A list and proposed schedule for any needed modifications to equipment and associated procedures necessary for the specified SBO duration.

The NRC has issued Regulatory Guide 1.155 "Station Blackout" which describes a means acceptable to the NRC Staff for meeting the requirements of 10CFR 50.63.

Regulatory Guide (RG) 1.155 states that the NRC Staff has determined that NUMARC 87-00 "Guidelines and Technical Bases for NUMARC Initiatives Addressing

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Palisades Plant

~* * ' ~uclear Regulatory Commission Station Blackout Rule 10CFR50.63

• 2 April 17, 1989 Station Blackout At Light Water Reactors" also provides guidance that is in large part identical to the RG 1.155 guidance and is acceptable to the NRC Staff for meeting these requirements.

Table 1 to RG 1.155 provides a cross-reference between RG 1.155 and NUMARC 87-00 a~d notes where the RG takes precedence.

Consumers Power has evaluated the Palisades Plant against the requirements of the SBO rule using guidance from NUMARC 87-00 except where RG 1.155 takes precedence. The results of this evaluation are detailed below.

A. PROPOSED STATION BLACKOUT DURATION NUMARC 87-00, Section 3 was used to determine a proposed SBO duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. This coping duration category was determined after accounting for modifications to provide an additional source of offsite power to the plant as described in Item 1 of our letter to D M Crutcpfield, Director, Division of Reactor Projects dated September 24, 1987. Completion of this modifica-tion is currently scheduled for the end of the next refueling outage.

The following plant factors were identified in determining the proposed station blackout duration:

1. AC Power Design Characteristic Group is Pl based on:

a. Expected frequency of grid-related LOOPS - does not exceed once per 20 years.

b. Estimated frequency of LOOPS due to extremely severe weather places the plant in ESW Group 1.

c. Estimated frequency of LOOPS due to severe weather places the plant SW Group 2.

d. The offsite power system is in the Il/2 Group.

2. The emergency AC power configuration group is C, based on:

a. There are 2 emergency AC power supplies not credited as alternate AC power sources.

b. 1 emergency AC power supply is necessary to operate safe shutdown equipment following a loss of offsite power.

3. A target emergency diesel-generator (EDG) reliability of 0.95 was selected based on having a nuclear average EDG reliability greater than 0.90 for the last 20 demands, and greater than 0.94 for the last 50 demands, and greater than 0.95 for the last 100 demands.

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' '"Nticlear Regulatory Commission Palisades Plant Station Blackout Rule 10CFR50.63

• 3 April 17, 1989 B. PROCEDURE DESCRIPTION Plant procedures for coping with a station blackout have been developed based on Combustion Engineering Emergency Procedure Guidelines (CEN-152, Revision 3). These procedures WE;!re reviewed against the guidelines pro-vided in NUMARC 87-00, Section 4. No modifications to the existing procedures were identified as a result of this review. Changes to these procedures will be required to incorporate changes being made to the offsite power arrangement, discussed in Section A above, or to incorporate other modifications made to enhance the plants capability to cope with a station blackout event.

C. PROPOSED MODIFICATIONS AND SCHEDULE The ability of Palisades to cope with a station blackout for four hours in accordance with NUMARC 87-00, Section 3.2.5 and as determined in Section "A" above; was assessed using NUMARC 87-00, Section 7 with the following results:

1. Condensate Inventory for Decay Heat Removal It has been determined from Section 7.2.1 of NUMARC 87-00 that 56,000 gallons of water are required for decay heat removal for four hours.

The Palisades Technical Specifications require that a minimum of 100,000 gallons of water be available in the condensate storage and primary coolant system makeup tanks combined. Capability is provided to gravity drain the contents of the primary coolant system makeup tank to the condensate storage tank. This capability is addressed in the plant Station Blackout Emergency Operating Procedure. Thus, the 100,000 gallons required to be maintained available by Technical Specifications exceeds the required quantity for coping with a four hour station blackout.

2. Class lE Battery Capacity A battery capacity calculation verified that the Class lE batteries have sufficient capacity to meet station blackout loads for four hours assuming loads not needed to cope with a station blackout are stripped.

These loads and the stripping procedure are identified in plant procedure EOP-3.

3. Compressed Air Air-operated valves relied upon to cope with a station blackout for four hours can either be operated manually or have sufficient backup sources independent of the preferred and Class lE power supply. V~lves requiring manual operation are identified in plant procedure EOP-3.

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-Nuclear Regulatory Commission Palisades Plant Station Blackout Rule 10CFR50.63 4

April 17, 1989 Emergency Procedure Guidelines (CEN-152, Revision 3) indicate that the preferred method of controlling steam generator pressure, and thus primary system temperature, during a station blackout is via the atmospheric dump valves. At Palisades, the atmospheric dump valves are air operated and do not have a backup air supply. The Palisades emergency operating procedure for station blackout controls steam generator pressure by aligning and controlling a manually operated steam vent path. Actions to align and control this steam generator vent path are performed outside of the control room. Consumers Power considers it prudent to enhance the capability to control steam gen-erator pressure for a postulated station blackout in order to minimize cycling of the steam generator safety valves and to reduce the number of manual actions required outside of the control room. Thus, a backup air supply will be provided for the atmospheric dump valves. This backup air supply will be sized to last for a minimum of four hours following a loss of the normal instrument air supply.

4. Loss of Ventilation

a. The steady state ambient air temperature for the steam driven AFW pump (the dominant area of concern for a PWR) during a station blackout is 152°F. This temperature is based on observed room temperatures during a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test run of the AFW turbine driven pump with the ventilation system for the room turned off.

b. The assumption in NUMARC 87-00 Section 2.7.1 that the control room will not exceed 120°F during a station blackout has been assessed.

It has been calculated that the control room at Palisades will not exceed 110°F during a station blackout. Therefore, the control room is not a dominant area of concern.

Reasonable assurance of the operability of station blackout response equipment in the steam driven AFW pump room has been assessed using Appendix F to NUMARC 87-00. No modifications or associated procedures are required to provide reasonable assurance for equipment operability.

5. Containment Isolation The plant list of containment isolation valves has been reviewed to verify that valves which must be capable of being closed or that must be operated (cycled) under station blackout conditions can be positioned (with indication) independent of the preferred and blacked-out unit's Class lE power supplies. No plant modifications and/or associated procedure changes were determined to be required to ensure that appropriate containment integrity can be provided under SBO conditions.

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"Nuclear Regulatory Commission Palisades Plant Station Blackout Rule 10CFR50.63

• 5 April 17, 1989

6. Reactor Coolant Inventory The ability to maintain adequate reactor coolant system inventory to ensure that the core is cooled has been assessed for an assumed 100 gpm (25 gpm per pump) primary coolant pump seal leak. This plant-specific analysis indicates that, at this assumed leak rate, the resultant reactor coolant inventory loss will not result in core uncovery during a SBO of four hours. Testing and operating experience on primary coolant pump seals of the type used at Palisades indicates that a loss of seal cooling, such as would occur during a SBO, does not result in a loss of seal function. Consumers Power evaluation of available data on the primary coolant pump seals suggests that a conservative upper bound on seal leak rate would be 5 gpm per pump. The 100 gpm leak rate assumed for the four hour duration of the station blackout event is thus five times more conservative than the maximum leak rate which could reasonably be expected to occur.

The control rod drive mechanisms (CRDM) provided at Palisades are of a rack and pinion design. The rotating shaft which drives the pinion gear penetrates the primary coolant system pressure boundary. This penetration is closed by means of a face-type rotating seal which is cooled by component cooling water. Leakage through the seal on each of 45 CRDMs is normally in the range of 0-400 ml/hr which was considered insignificant for purposes of the reactor coolant inventory loss evaluation. Recently, however, it was identified that no data exists regarding steam leakage past the CRDM seals. These seals could be exposed to a steam environment during the course of a four hour station blackout event concurrent with a primary coolant pump seal leak of sufficient magnitude to drain the pressurizer, allowing formation of a steam bubble in the reactor vessel head. It is currently our opinion that the 100 gpm leak rate assumed for the reactor coolant inventory loss evaluation conservatively bounds the worst case leak rate expected from both the reactor coolant pump and CRDM seals. We are, however, continuing to evaluate the potential for significant CRDM seal leakage during a station blackout event. This evaluation may require develop-ment of a test program to determine performance of the CRDM seals when exposed to steam. We will inform you by January 1, 1990 of any effects on our station blackout analysis resulting from our further evaluations of CRDM seal leakage The ability to maintain adequate reactor coolant inventory to ensure that the core is cooled has been assessed for four hours. Pending confirmation of our assumptions regarding leakage past the CRDM seals, we conclude that the expected rates of reactor coolant inventory loss under SBO conditions do not result in core uncovery in a SBO of four hours. Therefore, we presently conclude that a makeup system which would be available under SBO conditions is not required to maintain core cooling under natural circulation (including reflux boiling).

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.~Nuclear

• Regulatory Commission Palisades Plant Station Blackout Rule 10CFRS0.63

• 6 April 17, 1989 The modifications and associated procedure changes relating to the incor-poration of an additional source of offsite power identified in Part A above will be completed by the end of the next refueling outage currently scheduled to begin in March 1990. The modification and associated proce-dure changes relating to providing a backup air supply to the atmospheric dump valves identified in Part C.3 above will be completed within two years after the notification provided by the Director, Office of Nuclear Reactor Regulation in accordance with 10CFR 50.63(c)(3). Additional information relating to evaluations performed to quantify CRDM seal leakage identified in Part C.6 above will be provided by January 1, 1990.

K.enneth W Berry Director, Nuclear Licensing CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades NUMARC OC0489-002S-NL01