ML17329A243
| ML17329A243 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 10/31/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17329A242 | List: |
| References | |
| RTR-REGGD-01.155, RTR-REGGD-1.155 NUDOCS 9111140078 | |
| Download: ML17329A243 (13) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION STATION BLACKOUT RULE (10 CFR 50.63)
INDIANA MICHIGAN POWER COMPANY DONALD C.
COOK UNITS I AND 2 DOCKET NOS. 50-315/316
1.0 INTRODUCTION
On July 21, 1988, the Code of Federal Regulations, 10 CFR Part 50, was amended to include a
new Section 50.63, entitled "Loss of All Alternating Current Power," (Station Blackout).
The Station Blackout (SBO) Rule requires that each light-water-cooled nuclear power plant be able to withstand and recover from an SBO of a specified duration.
The SBO Rule also requires licensees to submit information as defined in Part 50.63 and to provide a plan and schedule for conformance to the SBO Rule.
The SBO Rule further requires that the baseline assumptions,
- analyses, and related information be available for NRC review.
Guidance for conformance to the SBO Rule is provided by (I) Regulatory Guide (RG) 1.155, Station Blackout, (2) the Nuclear Management and Resources Council, Inc.
(NUMARC) 87-00, Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors, and (3)
NUMARC 87-00 Supplemental guestions/Answers and Major Assumptions dated December 27,
- 1989, (issued to the industry by Nuclear Management and Resource Council, Inc.
(NUMARC) on January 4, 1990).
To facilitate the NRC staff's (hereafter referred to as staff) review of licensee responses to the SBO Rule, the staff endorsed two generic responses formats.
One response format is for use I':,'lants proposing to use an Alternate AC (AAC) power source and the otner format is for use by plants proposing an AC independent response.
The generic response formats provide the staff with a sumary of the results from the licensee's analysis of the plant's SBO coping capability.
The licensees are expected to verify the accuracy of the results and maintain documentation that supports the stated results.
Compliance to the SBO Rule is verified by a review of the licensee s
submittal, an audit review of the supporting documentation as deemed necessary and possible follow-up NRC inspections to ensure that the licensee has implemented the appropriate hardware and/or procedure modifications that will be required to comply with the SBO Rule.
The licensee's responses to the SBO Rule were provided by letters from H. P.
Alexich on April 14, 1989, and March 30, 1990, to the U.S. Nuclear Regulatory Commission, Document Control Desk.
Also, there was a teleconference between representatives of the licensee and the NRC staff on February 27, 1991.
The 9111140078 911031 PDR ADQCK 05000315 PDR
licensee's responses were reviewed by Science Applications International Corporation (SAIC) under contract to the NRC.
The results of the review are documented by an SAIC Technical Evaluation Report (TER) SAIC-91/6677, "Donald C.
Cook Nuclear Plant, Units I and 2, STATION BLACKOUT EVALUATION," dated July 30, 1991, (Attachment 1).
2.0 EVALUATION After reviewing the licensee's submittals and the SAIC TER the staff concurs with the SAIC analyses and conclusions as identified in the SAIC TER (refer to Attachment I for details).
The staff findings and recommendations are summarized as follows.
2.1 Station Blackout Duration The licensee has calculated a minimum acceptable SBO duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> based on a plant AC power design characteristic group "P2," an emergency AC (EAC) power configuration group "C," and a target Emergency Diesel Generator (EDG) reliability of 0.975.
Initially the licensee classified the AC power design characteristic group to be "P2."
However, the licensee failed to consider the October 1988 errata sheet for the NUtlARC 87-00, Table 3-5a showing the plant to be "Pl."
This error was brought to the licensee's attention during a
telephone conversation on February 27, 1991.
The licensee confirmed that the AC power design characteristic group is "Pl."
The group "C" EAC configuration is based on 2 EDGs credited as emergency ac power supplies with 1 EDG required to operate safe shutdown equipment following a loss of offsite power.
The target EDG reliability was based on the D. C.
Cook plant having an average EDG reliability greater than'0.90 over the last 20 demands.
Using this data, the target EDG reliability (0.975) selected by the licensee is appropriate.
- However, the licensee should also include the EDG reliability calculations for the last 50 and 100 demands in the documentation to be retained by the licensee in support of the SBO submittals.
The "Pl" grouping is based on an independence of offsite power classification of group "I I/2," a severe weather (SM) classification of group "2," and an extremely severe weather (ESW) classification of group "2."
After reviewing the available information in the liceosee s submittals, RG 1.155, NUMARC 87-00, and SAIC's TER, the staff agree~ with the licensee's evaluation of a 4-hour SBO coping duration.
2.2 Station Blackout Co in Ca abilit The licensee has proposed coping independent of an alternate AC power source for the required SBO coping duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and recovery therefrom.
The characteristics of the following plant systems and components were reviewed to assure that the systems have the availability, adequacy, and capability to achieve and maintain a safe shutdown and to recover from an SBO for a 4-hour coping duration.
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2.2.1 Condensate Inventor for Deca Heat Removal The licensee states that approximately 90,000 gallons of water per unit are required for decay heat removal, as well as for primary/secondary side pressure reduction, during a 4-hour SBO event.
The licensee's calculation is based on the guidance provided in Section 7.2.1 of NUMARC 87-00.
The licensee states that the minimum permissible condensate storage tank level per Technical Specification (TS) provides 175,000 gallons of water per unit, which exceeds the required quantity for coping with a 4-hour SBO.
In addition, the licensee states that with respect to the need to ensure an adequate condensate storage tank inventory, as well as to avoid the turbine-driven AFW pump runout conditions, procedure changes for the limitation of turbine-driven AFW pump operation will be provided in the EOP for the SBO scenario.
Based on its review, the staff concludes that the D.C.
Cook plant wi 11 have sufficient condensate inventory for decay heat removal and cooldown during an SBO event.
2.2.2 Class lE Batter Ca acit The licensee stated that the Class lE batteries were determined to be inadequate without load shedding to meet SBO loads for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
The licensee's UFSAR states that there are three Class 1E batteries,'Division I and 2, station batteries, and the "N Train" battery, all of which are 250 volt and sized to provide power to all connected loads for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.
In order to conserve the battery capacity so it can support SBO loads over 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, the licensee states that three non-Class lE loads will be shed:
turbine DC emergency lube oil pump of each main feedwater pump, the NSAC inverter, and the main turbine DC emergency bearing oil pumps.
The licensee also states that these loads will be shed within I hour after the SBO event begins and will be identified in plant procedures.
Since no battery calculations were provided for staff review, we were unable to confirm the adequacy of the Class 1E batteries.
Recommendations:
The licensee should confirm that the calculations used to y
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10K to 15% design margin to compensate for less than optimum operating conditions, recent discharge, or ambient temperature less than anticipated.
The licensee needs to verify that such a margin has been used or show other conservatisms that were used in the sizing calculations to compensate for loss of the assumed margin.
This analysis and confirmation that the battery had adequate capacity should be included in the documentation supp ting the SBO submittals that is to be maintained by the licensee.
2.2.3 ~Cd Ai The licensee stated that air-operated valves necessary to cope with an SBO for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> will be either operated manually or have sufficient backup sources.
Valves requiring manual operation or backup sources for operation will be identified in plant procedures.
A review of the auxiliary feedwater and the atmospheric steam dump, or PORV systems, was performed to determine their dependency on compressed air. It was concluded that compressed air is not needed for operation of the auxiliary feedwater
- system, as the valves and controls are powered by the Class lE batteries.
By following the emergency remote shutdown procedure, backup bottled nitrogen for operation of the air
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- 4 operated PORVs can be provided through a manual connection, if needed.
Based on its review, the staff concludes sufficient compressed air is available for the operation of the needed air-operated valves.
2.2.4 Effects of Loss of Ventilation The results of the ventilation analyses for the dominant areas of concern (DACs) and the control room were summarized by the licensee including the associated final SBO temperatures, type of heat-up analysis performed, and justification for reasonable assurance of operability (RAO).
RAO is es-tablished without further analysis if temperatures in the DAC are calculated to be equal to or less than 120'F (NUMARC 87-00 Supplemental guestions/Answers f2.2).
The licensee concluded that RAO of SBO response equipment in the DACs has been assessed using Appendix F to NUMARC 87-00 and/or the Topical Report and no modifications or associated procedures are required.
However, pro-cedural changes will be provided to conform with the guidance described in NUMARC 87-00 for opening the control room cabinet doors.
The staff's findings regarding the licensee's calculations are summarized as fol1ows.
2.2.4.1 Control Room We reviewed the information provided by the licensee for the control room heat-up calculation and found the initial conditions and the assumptions to be reasonable, except for the following:
1.
The licensee assumed the outside air temperature to be 95'F.
Review of the NUREG/CR-1390 extreme annual temperature for the D. C.
Cook site indicates that the outside ait temperature could reach 106'F once every 50 years.
Therefore, the 95'F air temperature is non-conservative.
2.
The licensee assumed the temperature above the control room drop ceiling panels, "attic area," to be 100'F initially and to remain unchanged for the duration.
In reality, this temperature increases during the SBO period.
However, the licensee assumed an initial control room temperature of 95'F and added 10kW heat load as margin to the heat generated during normal operating conditions for conservatism.
Therefore, the staff agrees with its consultant that, the control room calculated peak temperature is acceptable.
2.2.4.2 Inverter Room The licensee's assumptions appear to be reasonable except for the outside air temperature.
However, its impact on the final temperature is expected to be small.
With regard to equipment operability in this room, the licensee should have used the manufacturer's equipment qualification temperatures for the inverters (GRID inverters) as opposed to the use of generic data given in Appendix F of NUMARC 87-00.
It is our understanding that the inverters are normally qualified for a 104'F ambient air temperature.
Recommendation:
The licensee needs to use the manufacturer's equipment quali-p f
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Also, this verification and confirmation should be included in the documentation supporting the SBO submittals that is to be maintained by the licensee.
2.2.4.3 Containment In accordance with NUMARC Supplemental guestions/Answers and Major Assumptions dated January 4, 1990, the licensees were asked to verify that the heat-up conditions resulting from a LOCA/HELB in the containment envelop the conditions expected during an SBO event.
However, the licensee has not provided this verification.
Recommendation:
The licensee needs to verify that the heat-up conditions LPLA/IILBI h
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d during an SBO event, as required by NUMARC Supplemental guestions/Answers.
The results of the verification should be included with the other documentation that is to be retained by the licensee in support of the SBO submittals.
2.2.5 Containment Isolation The licensee stated that the plant list of containment isolation valves (CIVs) was reviewed to verify that CIVs that must be operated under SBO conditions can be positioned, with indication, independent of the preferred and blacked-out Class lE AC power supplies.
No modifications or procedure changes were necessary to ensure containment integrity under SBO conditions.
In response to questions raised during the telephone conversation on February 27, 1991, the licensee supplied a list of 14 CIVs which cannot be excluded by the criteria given in RG 1.155 on NUHARC 87-00, and provided justifications for the deviations from the exclusion criteria.
Based on its review of the licensee's rationals and each of the above 14 CIVs, the staff finds that these 14 CIVs with the exception of MCM-221 and MCM-231 have met the intent of the guidance described in RG 1.155 and therefore, are acceptable.
With respect to the valves, HCM-221 and HCM-231, the staff finds that although these valves are required to be in the open position during an SBO, the licensee needs to list them in a procedure and ensure that these valves could be closed, if needed.
Recommendation:
Although containment isolation valves MCM-221 and HCM-231 are
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during an SBO event, the licensee needs to list them in a procedure and ensure that these valves could be closed, if needed.
This information should be included in the documentation supporting the SBO submittals that are to be maintained by the licensee.
2.2.6 Reactor Coolant Inventor The licensee states that the ability to maintain adequate reactor coolant system (RCS) inventory to ensure that the core is cooled has been assessed for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
A plant-specific analysis was used for this assessment.
The licensee stated that the expected rates of reactor coolant inventory loss under SBO conditions do not result in core uncovery.
Therefore, RCS makeup systems under SBO conditions are not required to maintain cote cooling under natural circulation (including reflux boiling).
Expected maximum losses from the RCS are 25 gpm from each of the four RCS pumps and 11 gpm allowed by the TS for a total of ill gpm per each unit.
Over 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> this leak rate results in a loss of 26,640 gallons which is equivalent to an RCS mass loss of 222,000 ibm.
The primary system at D.
C.
Cook has an estimated liquid volume of 11,780 ft~
( 530,000 ibm) of water at rated power.
Therefore, a loss of 222,000 ibm of water from the RCS would not uncover the core.
The staff agrees
- that, under these conditions, there is reasonable assurance that the reactor coolant inventory will be adequate during an SBO.
The reactor coolant inventory evaluation as described above was based on the guidance provided in NUMARC 87-00 of 25 gpm per reactor coolant pump (RCP) seal leakage for pressurized water reactors.
The 25 gpm value was agreed to between NUNRC and the staff pending resolution of Generic Issue (GI) 23. If the final resolution of GI-23 defines higher RCP leakage rates than assumed for this evaluation, the licensee should be aware of the potential impact of this resolution on their analyses and actions addressing conformance to the SBO Rule.
2.3 Pro osed Procedures and Trainin The licensee stated that plant procedures have been reviewed and, where necessary, will be modified by July 31, 1989, to meet the guidelines in NUHARC 87-00, Section 4, in the following areas:
1.
SBO response, 2.
AC power restoration, and 3.
severe weather.
The licensee identified the procedures that have been reviewed as well as those that have been modified to cope with an SBO event.
The staff did not review the procedures or proposed procedure modifications.
The staff expects the licensee to implement and maintain these porcedures including any others that may be required to ensure an appropriate response to an SBO event.
Although personnel training requirements for an SBO response were not specifi-cally addressed by the 1'icensee's submittal, the staff expects the licensee to implement the appropriate training to ensure an effective response to an SBO.
2.4 Pro osed Modifications The licensee stated that two plant modifications are required to enhance the coping capability during a 4-hour SBO event.
1.
Of the 4
RCS temperature
- channels, 2 are normally powered by an opposite unit diesel-backed power source.
However, based on the single failure criteria postulated within NUNRC 87-00 for the non-SBO unit, this opposite unit power source may not be available.
Therefore, direct RCS pressure indication may not be available during SBO-recovery depending on the source of power established for recovery.
Modifications necessary for ensuring direct indication of RCS pressure and temperature in the event of an SBO are scheduled for implementation during both units'990 refueling outages.
2.
Several additional emergency lights were identified as needed.
These lights will be added as part of the Long Range Planning Module of the Plant Integrated management System.
At present, reliance will be placed on operators'lashlights.
The staff review identified no additional modifications necessary to cope with a 4-hour SBO.'he proposed modifications if properly implemented will provide the information needed by the operators and enhance the operators ability to perform functions during the SBO event.
Recomendation:
The licensee should include a full description including the
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documentation that is to be maintained by the licensee in support of the SBO submittals.
2.5 ualit Assurance and Technical S ecifications The licensee did not specifically address guality Assurance (gA) programs or TS for the SBO equipment.
The TS 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 would expect that the plant procedures wi 11 reflect the'ppropriate testing and surveillance requirements to ensure the operability of the necessary SBO equipment.
If the staff later determines that TS regarding the SBO equipment is warranted, the licensee will be notified of the implementation requirements.
Recommendation:
The licensee should verify and confirm that the SBO equipment Ifl dby pp pi Iydp g
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gfd of Appendix A, RG 1.155.
Verification that such a program is in place should be included as part of the documentation supporting the SBO Rule response.
2.6 EDG Reliabilit Pro ram The licensee stated that the target reliability of 0.975 will be maintained.
The licensee stated that a TS change in accordance with NSAC-108, as well as NUMARC Initiative 5A may be pursued.
However, the licensee did not specifically state that a reliability program in accordance with RG 1.155, Section 1.2 would be implemented.
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aa Recommendation:
The licensee should implement an EDG reliability program I
9 id f RG 1.l55, S ti 1.2.
C fi that such a program is in place or will be implemented should be included in the documentation supporting the SBO submittals that is to be maintained by the licensee.
2.7 Sco e of Staff Review The SBO Rule (10CFR 50.63) requires licensees to submit a response containing specifically defined information. It also requires utilities "...to have baseline assumptions,
- analyses, and related information used in their coping evaluations available for NRC review."
The staff and its contractor (SAIC) did not perform a detailed review of the proposed hardware and procedural modifications which are scheduled for later implementation.
- However, based on our review of the licensee's supporting documentation, we have identified the following areas for focus in any follow-up inspection or assessment that may be undertaken'by the NRC to verify conformance with the SBO Rule.
Additional items may be added as a result of the staff review of the actions taken by the licensee in response to this SE.
t a.
Hardware and procedural modifications; b.
SBO procedures in accordance with RG 1.155, Position 3.4, and NUMARC 87-00, Section 4
c.
Operator staffing and training to follow the identified actions in the SBO procedure; d.
EDG reliability program meets, as a minimum, the guidelines of RG 1.155; e.
Equipment and components required to cope with an SBO are incorporated in a gA program that meets the guidance of RG 1.155, Appendix A; and f.
Actions taken per taining to the specific recommendations noted above in the SE.
3.0
SUMMARY
AND CONCLUSION The staff has reviewed the licensee's responses to the SBO Rule (10 CFR 50.63) and the TER prepared by the staff's consultant, SAIC.
Based on our review, several confirmations and commitments need to be made as described in the recommendations itemized herein.
These include verification and confirmation to assure that Class lE battery capacity is adequate, verification that the CRID inverters are qualified for the calculated ambient temperature of 121'F, verification that the temperature conditions resulting from a LOCA/HELB in the containment envelops the temperature conditions expected during an SBO event, an appropriate plant procedure for valves MCM-221 and MCM-231, a description of your two proposed modifications, confirmation that the SBO equipment is covered by an appropriate gA program consistent with RG 1.155, and a commitment to implement an EDG reliability program that meets, as a minimum, the guidelines
l of RG 1.155, Section 1.2.
The licensee should include the documentation associated with the above actions and verifications with the other documentation supporting the SBO submittal, and maintain this documentation for further inspection and assessment as may be undertaken by the NRC to further verify conformance with the SBO Rule.
Based on our review of the submittals, we find the licensee's responses and proposed method of dealing with an SBO to be in conformance with the SBO Rule contingent upon receipt of confirmation from the licensee within 30 days that the recommendations identified within this SE will be implemented; The schedule for implementation should also be provided in accordance with 10 CFR 50.63(c)(4).
4.0 Attachment SAIC-91/6677, Technical Evaluation Report, Donald C.
Cook Nuclear Plant Units 1 and 2, Station Blackout Evaluation, July 30, 1991.
Principal Contributors:
C. Thomas T. Colburn Date:
October 31, 1991
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