ML20248A019
| ML20248A019 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/30/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20248A008 | List: |
| References | |
| NUDOCS 8906080044 | |
| Download: ML20248A019 (4) | |
Text
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'k UNITED STATES l
NUCLEAR REGULATORY COMMISSION J
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.j WASHINGTON, D. C. 20555
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1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.129 TO FACILITY OPERATING LICENSE NO. DPR-32 AND AMENDMENT NO.129 TO FACILITY OPERATING LICENSE NO. DPR-37 VIRGINI A ELECTRIC AND POWER COMPANY SURRY POWER STATION, UNIT N05. 1 AND 2 DOCKET NOS. 50-280 AND 50-281 1.
INTRODUCTION By letter dated March 20, 1989, Virginia Electric and Power Company (the licensee), requested changes to the Technical Specifications (TS) Sections 3.14
" Circulating and Service Water Systems" and 3.23, " Control and Relay Room Ventilation Supply filter Trains." The proposed changes would impose; additional operating restrictions on the Main Control Room and Emergency Switchgear Room (MCR and ESGR) Air Conditioning System.
2.0 DISCUSSION AND EVALUATION By letter dated October 19, 1988, and by coninitments made during a meeting on October 26, 1988, the licensee identified several items which required further analysis and appropriate corrective action prior to plant restart. One of the items identified addressed the adequacy of the MCR and ESGR Air Conditioning Sy stem. By letter dated March 20, 1989, the licensee submitted an amendment request which included test results and corrective actions, and proposed a number of interim operating restrictions as they relate directly to this issue at Surry Units 1 and 2.
The MCR and ESGR Air Conditioning System is a shared system that cools the Surry Unit I and Unit 2 main control rooms, emergency switchgear rooms, and relay rooms.
The MCR and ESGR Air Conditioning System cools only the air within the area bcundaries and does not serve to pressurize the control room pressure boundary nor condition incoming outside air.
The system was originally designed to consist of one operating full capacity air conditioning train and one full capacity back-up air conditioning train. As discussed later, the licensee, based on test results, concluded that each air conditioning train would not provide the required 100 percent heat removal capacity.
Each train contains one chiller refrigeration unit and four air handling units (AHU) - a dedicated AHU for each of the areas served, i.e., the Unit 1 MCR, Unit 2 MCR, Unit 1 ESGR, and Unit 2 ESGR (reference to the ESGR implies reference to the relay rooms also). A third chiller is provided as a maintenance swing chiller.
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2-The system is designed to maintain the bulk air in the MCR and ESGR within the design temperature envelope following a loss-of-coolant accident (LOCA) coin-cident with a loss-of-offsite power (LOOP) and a single failure. On September 9, 1988, the licensee prepared a Station Deviation Report to address a potential inadequacy in the MCR and ESGR Air Cond'itioning System to maintain design room temperatures. Subsequently, a special test was conducted to obtain system and equipment performance data.
Extrapolation of the test results showed that the 4
MCR air bulk temperatures would be within the design envelope following an acci-dent. However, the test data also showed that the design accident heat load in the emergency switchgear rcoms would exceed the design capacity of a single train of the ESGR air handling units.
In addition, the test results indicated that the calculated ESGR design heat loads, when added to the MCR design heat loads, exceeded the design capacity of a single chiller refrigeration unit. The test also indicated that certain system equipment was not performing adequately, e.g., the air handling unit fan speeds and inadequate chilled water flow.
To maintain design basis room temperatures and the original system oesign config-uration, i.e., two 100% capacity air conditioning trains, a permanent modification must be implemented to replace undersized equipment with new, higher capacity equipment. Due to the long lead time for safety-related, custom designed equip-ment, this modification is scheduled for implementation during the next Surry refueling outages, currently estimated to occur in the fall of 1990.
In the interim, the MCR and ESGR Air Conditioning System will be modified to utilize the existing equipment to meet the system design basis, i.e., maintain design room temperatures under design basis assumptions (LOCA, LOOP, Single Failure). Specifically, the interim system modifications will require the opera-tion of two air handling units in each emergency switchgear room and two chillers to maintain design ESGR temperatures under design heat load conditions. Mod-
!fications to the ESGR air handling units include increasing fan speeds and installing redundant drive motors on each air handling unit which is powered from different power sources.
A chiller modification will also be necessary to account for credible equipment failure. Because only two of the three existing chillers are required to operate under maximum design heat loads, modifications to the chillers are less extensive then those for the ESGR air Landling units. However, in one of the failure scenarios considered for the existing design configuration, emergency power would be lost to two of the three chillers. To accommodate this failure scenario, the licensee will install a manual power transfer switch to enable the swing chiller to be powered from either of two emergency buses.
By telecon on May 9, 1989, the licensee indicated that their proposed design is such that no s',J e failure 1
in the transfer switch can challenge or cause failure.of both emergency buses at the same time.
In addition, the licensee indicated that analysis demonstrates that both emergency buses and their associated power supplies and electric distribution systems will have sufficient capacity and capability to acconinodate the increased loading proposed by the modification for any design basis condi-tions. Other associated activities, such as de-energizing unnecessary heat loads, cleaning fans, cooling coils, and refurbishing of pumps, are being performed to enhance system operability.
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" In addition to the. identified hardware modi.'ications, deficiencies in the current maintenance and surveillance programs will be reviewed and corrected to ensure that system reliability and performance ace maintained throughout the interim operating period.
In addition, the existing Nuclear Design Control Program will' be reviewed and ennanced, as appropriate, to ensure that the cumulative effects of incremental heat load additions to critical areas are properly ascessed and taken into consideration.
These interim modifications will restore the MCR and ESGR Air Conditioning System to its design basis by ensuring that safety equipment reliability and control room habitability are maintained under normal and accident conditions.
These modifications will also restore equipment redundancy to provide single failure protection under credible equipment failure scenarios. The interim limiting conditions for operation will require that three chillers and eight air handling units be operable when at power operation.
Further, the interim limiting conditions for operation will require that both crive motors on each ESGR air handling unit be operable.
In addition to the equipment restrictions above, a fire watch will be required during this interim period in both units' ESER and Mechanical Equipment Room (MER) #3 to address Appendix R considerations.
Action statements will allow that redundant equipment be inoperable for a period not to exceed seven (7) days to facilitate preventative and corrective maintenance.
If the inoperable equipment is not returned to operable status within seven (7) days, the appropriate reactor unit (s) must be brought to the shutdown condition.
The action stetements only allow continued operation (i.e., 7-day window) when sufficient equi > ment is operable to maintain design room temperatures under maximum design Teat loads. The action statements require that the appropriate reactor unit (s) be shut down whenever less than the requisite equipment is operable.
Based on the staff's evaluation of the licensee's analysis, and the proposed TS changes and action statements, we conclude that the implementation of the MCR and ESGR Air Conditioning System interim modifications meets design basis criterio for the Surry Power Station and will provide acceptable assurance that the design temperatures in the control rooms and emergency switchgear/ relay rooms will be maintained under normal and accident conditions. We, therefore, conclude that the proposed changes to the Technical Specifications are acceptable until c permanent upgrade is implemented during the next refueling outage currently estimated to occur in the fell of 1990.
ENVIRONMENTAL CONSIDERATION These amendments involve a change in the installation or use of the facilities components located within the restricted areas as defir.ed in 10 CFR Part 20.
The staff has determined that these amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite ard that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding. Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forthin10CFR51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
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CONCLUSION We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be i
endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations and the issuance of these amendments will.not be inimical to the common defense and security or to 1
the health and safety of the public.
Dated:
May 30, 1989 l
l Principal Contributor:
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B. C. Buckley l
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