ML20125B518
| ML20125B518 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/27/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20125B514 | List: |
| References | |
| NUDOCS 9212100039 | |
| Download: ML20125B518 (5) | |
Text
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SAFETY EVtLVATION BY TPE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDcl.NT N0.
18 TO FACILITY OPERATING LICENSE NO. NPF-86 FP.
NORTH ATLANTIC ENERQY SERVICE CORPORATION FEABROOK STATIC",_ NIT NO. 1 DOCKET NO. E -443 i
Q l.0 INTRODUCTION By letter dated Septereber 30, 1992 and supplemented October 14, 1392, North Atlat'lc Energy Service Corporation (NAESCO or the lice ser) requested an amandment to the Seabrook Station (Seabrook) Technical Specifications (TSs).
Tha pressed change will increase the TS temperature limit for the cooling towar L: sin water frcs the current value of 67.3*F to 70*F, permit coaling tower fans to be considered operable if the fans are capable of beit;- S.arted manually, replace a sur'reillance requirement which verifies the coo tower
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fans start automaticslly on a tower actuation signal with a requirei e to
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verify appropriate valves actuate to their correct positica in respt to a tower actuation signal, and revise the bases of TS 3/4.7 5 by adding a paragraph discussing manual operation of co 0in tower spray valves and fans.
The analysis supporting this license :mendent.equest was submitted by latter dated October 14, 1992, and the infr M5,ior. nretided therein was not out:ide the scope of the no significant hm i c9nt%; tion analysis in the Septer$er 30 1992 request.
The in.t..se in the TS temperature limit for the cooling tower basin water is intended to reduce the probability that cooling tower operation with spray would be necessary to cool the basin wate during the summer months. The proviLon permitting manual actuation of cooling towcr sprays and fans fem the main control board is intended to prevent the icing and reduced coolic.g affecti,eness which could result under certain environmental conditions follo<ing automatic actuation of cooiing tower sprays and fans.
Verification that appropriate v&ives actuate to their correct position on a tower actuation signal ensures that the correct flow path will be established to support cooling tower operation with or without fans and spray. A recent modification installed valves remotely operable from the mair control board which allows the service wz.ter return flow to be directed to the basin, bypassing the spray header.
Procedures directing the operator in the manual C.iitiation of cooling tower sprays and fans have been developed.
2.0 EVALVATION The Seabrook cooling tower functions as the backup ultimate heat sink, and is capable of cooling the service water system heat loads following a safe l
9212100039 921127 PDR ADOCK 05000443 P
4 shutdown scismic event which assumes the collapse ard greater than 95%
blockage of the circulating water system tunnels.
The design basis for the cooling tower also assumes a loss of coolant accident (LOCA) coincident with a loss of offsite power (LOOP).
The design basis heat load for the tower therefore consists of the residual heat removal (RHR) system heat rejection, containment building spray (CBS) system heat rejection, diesel generator cooling water (DGCW) system heat rejection, the cooling tower pumps, and other small heat loads imposed on the primary component cooling water (PCCW) system during the design basis event.
During the initial stage of a LOCA, the emergency core cooling system (ECCS) operates in the injection phase.
In this mode of operation, the whter supply for the ECCS pumps is the refueling water storage tank (RWST) and the heat loads imposed on the coriing tower are minimal, including only the DGCW system, the cooling tower pumps, and minor PCCW system heat loads.
The majority of the heat load on the cooling tower occurs following the transition from the injection phase to the recirculation phase.
During the recirculation phase, valves are aligned to draw water from the containment recirculation sump to supply the RHR and CBS system pumps. This water is cooled in the RHR and CBS heat exchangers prior to injection into the reactor vessel and containment, respectively.
The heat removed in these heat exchangers is ultimately rejected to the cooling tower, imposing a significant load on the cooling tower.
NAESCO performed an analysis which demonstrated that, if the cooling tower is manually operated, a minimum of 74 minutes will be available for the operator to initiate cooling tower fans and sprays in order to prevent the PCCW heat exchanger shell side outlet temperature from exceedirl its maximum analyzed value at any time following the accident.
Components in 6he PCCW system were analyzed assuming an operating design PCCW supply temoerature of 120*F with a transient increase to 126'F for a 1.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period.
The analysis assumed an initial cooling tower basin temperature of 70*F which conservatively bounds the current TS maximum value of 67.3*F.
The licensee evaluated one and two trains of safety system operation in the ;.ost-LOCA cooldown environment, and two train operation during a normal cooldown. Two train operation post-LOCA was found to be limiting with regard to time available to mant 11y initiate cooling tower fans and sprays due to the shorter duratice,.,f the injection phase and the greater rate of heat removal from containment to the ultimate heat sink during the recirculation phase.
The licensee states that there is adequate procedural guidance, operator training, ano main control room indication available to alert the operator to the need ta initiate cooling tower fan and spray operation.
Step 10 of the Seabrook Station emergency operating procedur; E-0, " Reactor Trip or Safety l
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i Injection," dir7 cts the operator to verify operation of the uldmate heat sink.
If a loss of the normal heat sink were to occur without a safety injection or a reactor trip, abnormal procedure 0S1216.01, " Degraded Ultimate Heat Sink," provides guidance on cooling tower fan and spray operation.
For the above procedures, if the cooling tower is performing the function of the ultimate heat sink, the operator is directed to initiate cooling tower fan and spray operation based on PCCW heat exchanger outlet temperature and environmental wet bulb ten.perature.
In addition, PCCW high temperature alarms on the main control board will alert the operator to the need to initiate l
cooling tower fan and spray operation. Operator training is tenducted using abnormal and emergency simulator scenarios, several of which empnasize monitoring of ultimate heat sink performance.
Both the cooling tower fans and the spray bypass valves are operated from t' main control board.
2 The staff reviewed the licensee's analysis.
Based on the staff's review of the licensee's analysis, tha staff finds the assumptions ar.d methocology of the analysis to be acceptatle.
However, the staff noted that the analysis failed to include the heat loads associated-with the DCCW system and the 4
cooling tower pump during the injection phase of the design basis LOCA cooldown. The staff e m uated the impact of this omission on the peak PCCW 4
i heat exchanger outlet temperature and determined that the-value for the limiting two train case did not exceed the design peak operating temperature.
Calculations were also performed which verified that the computer model accurately represents the appropriate thermodynamic and heat transfer relationships describing the affected systems. Therefore, the staff finds this analysis to be valid for justifying manual operation of the cooling tower fans and sprays.
It a staff performed an independent bounding calculation to provide additional assurance that adequate time it waihble following a design basis LOCA to manually initiate cooling tower fans and spvys prior to reaching design temperature limits.
This calculation used tne heat ennunger effectiveness value provided in the licensee's current analysis, ar.d PCCW heat exchanger design parameten and two train peak post-LOCA heat loads from the Seabrook Station Update.1 Final Safety Analysis Report (UFSAR). Assuming two trains of safety-reh,wd equipment are operating and the cooling tower basin temperature is initially 70*F, the rtaff calculated-a minimum of 50 minutes are available j
to initie.te cooling towar fan and spray operation before PCCW heat exchanger outlet temperature exceeas 120*F.
The increase in the TS cooling tower basin temperature.imit to 70*F is consistent with the initial basin temperature value used in the supporting analysis.
Since there is margin impicit in the procedures directing the initiation of cooling tower fans and sprays, the usc. of the analysis value for the TS basin temperatu e limit is acceptable.
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i Based on the per19d of time available to initiate cooling tower fans and sprays determined by analysis, the availability-of procedures, the relevant operator training, and the accessibility of the cooling tower fan and spray i
bypa:s valve controls, the staff concludes that there is adequate assurance tht the cooling tower will operate properly to remove the necessary heat with manual initiation of cooling tower fans and sprays.
In addition, procedures to manually initiate cooling tower fans and sprays under cold weather conditions provide protection from damage potentially resulting from fan operation with excessive ice accumulation and degreded performance of the cooling tower due to ice blocking flow through the fill tile. Therefore, permitting the cooling tower fans to be considered operable if the fans are capable of being started manually is acceptable.
Verification that appropriate valves actuate to their correct position on a tower actuation signal ensures that the correct flow path will be established to support cooling tower operation, with or without fans and spray.
Since manual initia. ion of the cooling tower fans and sprays it shown to be adequate in the analysis, a surveillance requirement testing thd the cooling tower fans start automatically on a tower actuation signal is not necessary. The cooling tower spray bypass valves and cooling tower fans are demonstrated to be manually operable from the main control board through existing surveillance requirements 4.0.5 and 4.7.5c.l. respectively. Therefore, the proposed replacement of a surveillance requirement which verifies the cooling tower fans start automatically on a tower actuation signal with a requirement to verify appropriate valves actuate to their correct position in response to a tower actuation signal is acceptable.
The addition to the TS bases reflecting manual operation.of cooling tower fans and sprays is consistent with the intended method of operation of these components.
Therefore, the proposed addition to the bases of TS 3/4.7.5 is-acceptable.
The staff has determined that the cooling tower is caoable of removing the necessary heat loads under design basis accident condition: with manual initiation of cooling tower fans and sprays, and with an initial cooling tower basin temperature of 70*F.
The staff also determined that the ability of the cooling tower to perforr' its design function under adverse cold weather conditions where freezing is of concern is improved by the proceduralized manual initiation of cooling tower fans and sprays. These capabilities are consistent with the guidance of section 9.2.5 of the Standard Review Plan (SRP),NUREG-0800.
Existing surveillance requirements test the capability to manually operate cooling tower' fans and spray bypass valves from the main l
control board. Therefore, the proposed changes to TS 3/4.7.5.are acceptable.
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3.0 STATE CONSULTATION
In accordance with the Commission's regulations and past actice, the New Hampshire and Massachusett:, State officials were notified of the proposed issuance of the amendment. The State officials he.d no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined i
that the amendment involves no significant increase in the amounts, and no-l significant change in the types, of any effluents that may be released offsite, and that there is no significant increaso in' individual or cumulative occupational radiation exposure. The Commission has previously-issued a proposed fins 1g that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (57 FR 48822). _Accordingly, the amendment meets the eligibility-criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR i
51.22(b) no environmental impact statement or environmental assessment need be l
prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the l-public will not be endangered by operation in the proposed manner, -(2) such L
activities will be sonducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will'not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
S. Jones
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Date:
November 23, 1992 t
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