ML20009G227
| ML20009G227 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/23/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20009G226 | List: |
| References | |
| NUDOCS 8108030459 | |
| Download: ML20009G227 (3) | |
Text
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[paatgf, UNITED STATES
{ i.\\. *j c ( ',g NUCLEAR REGULATORY COMMISSION D
.E WASHINGTON, D. C. 20$55 i
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TUPPORTING AMENDMENT NO. 72 TO LICENSE AO. DPR-46 NEBRASKA PUBLIC POWER DISTRICT DOCKET NO. 50-298 COOPER NUCLEAR STATION INTRODUCTION f
Due to the recent heat wave and drought in the midwestern region of the country, the Missouri River, which is used for service water for the Cooper facility, has reached a high enough temperature so the suppression pool 0
temperature cannot be mairtained at 90 F by cooling from this water. This is significant because the suppression pool's maximum allowable temperature 0
is limited to 90 F by the plant's Technical Specifications. The design basis for all plant transients assumes a maximum suppression pool temperature of 0
90 F.
Any incrcase in river water temperature from existing levels will cause the torus water temperature to rise above 90 F.
If this were to occur, the plant would have to shutdown.
By phone on July 16, 1981, and confirmed by letter dated July 16, 1961, the Nebraska Public Power District (NPPD) licensee requested an emergency Technical Specification change regarding maximum suppression pool tenceratures.
The licensee proposed that during periods when the river water temperature is sufficiently high that the suppression chamber water temperature cannot 0
be maintained below 90 F, the maximum permitted uater temperature in the 0
0 suppression chamber may be increased to 95 F from the current 90 F Technical Specification 1imit.
Discussion The Technical Specifications for :he Cooper Nuclear Station plant require that:
(1) the suppression pool temperature shall not exceed 90 F during 0
normal plant operation; (2) during testing which adds heat to the suppression 0
9001 the water temperature shall not exceed 10 F above the normal power operation limit specified in condition 1 tbove. In connection with such testing, the pool temperature shall be reduced below the normal power operation limit specified i condition 1 within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or the plant shall be in a cold shutdown condition in the subsequent 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />; (3) in the 0
event that the suppression pool temperature reaches 110 F, the reactor shall be scrammed and power operation shall not be resumed until the pool temperature is reducad below the power operation limit specified in condition 1; and (4) in the event that the suppression pool temperature reaches 120 F during 0
reactor isolation conditions, the reactor shall be depressurized to le,s 8108030459 810723 PDR ADOCK 05000298 P
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> than 200 psig at normal cooldown rates. These requirements stem from the initial conditions assumed in the containment response analyses for loss-of-coolant accident (LOCA) and safety-relief valve (SRV) discharge transients.
0 0
In its request, NPPD requested that the 90 F limit be increased to 95 F and provided the results of analyses of the design basfs LOCA and SRV discharge events which consider the revised limit.
Evaluation 1
(
With respect to LOCA transients, the principal considerations are (1) the containment design pressure and temperature, (2) the net positive suction i
head (NPSH) for the Emergency Core Cooling System (ECCS) pumps, and (3) the maximum suppression pool temperature for steam condensation. To address these considerations, NPPD has submitted the results of a General Electric analysis for Cooper, which used the 95 F initial condition. This analysis is being performed by General Electric so Cooper could request a permanent Technical Specification suppression pool temperature change. The results l
of this analysis showed that the suppression pool Technical Specification 0
l limit may be raised from 90 to 950F without exceeding the 200 F Mark 1 l
temperature limit, LOCA considerations and ECCS pump NPSH requirements.
In a similar Technical Specification change issued for peach Bottom on August 1,1980, the original design basis LOCA for the Peach Bottom plar.t 0
was predicated on maintaining the pool temperature below 170 F to assure complete condensation of the steam evolving from the postulated break and the subsequent removal of heat from the containment via the suppression 0
pool and the Residual Heat Removal (RHR) system.
The 170 F limit was l
based on data from the Bodega Bay and 1%mboldt Bav test facilities which formad the criginal basis for the containment design, as described in the plant's Final Safety Analysis Report. (FSAR). The suppression pool temperature response in the ifcensee's submittal and the FSAR show a peak pool 0
temperature of approximately 190 F at 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after the postulated accident i
for minimum cooling capability. However, steaming from the break ends much earlier in the transient (i.e., within minutes) and subsequent heat l
soval from the core to tne pool is via subcooled ECCS water. The pool 0
temperature reached 170 F at approximately 1.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for an initial pool l
temperature of 90U and approximately 15 minutes sooner for an initial 0
pool temperature.cf 95 F, still well after steaming has stopped.
- Further, recent tests in the Mark I Full Scale Test Facility (General Electric topical report NEDE-24539) have indicated condensation effectiveness at pool 0
temperatures above 170 F.
It was therefore, concluded that the proposed change would not adversely affect the condensation effectiveness or the heat removal capability of the containment system. Since Cooper and Peach Bottom have approximately the same ratio of torus water volume to core 0
thermal power. the same original design basis 170 F pool temperature and since they reach approximately the same original peak suppression pool 0
temperature (192 compared to 190 F) the above conclusion should be applicable for the proposed change to Cooper.
. In a General Electric letter dated July 16, 1981 which was an attachment to the Nebraska Public Power Distrist July 16, 1981 letter the results of the suppression pool temperature analysfy assuming the initial suppression 0
pool temperature was 95 F was provided.
the results of this analysis showed 0
the maximum bulk pool temperature did not exceed 179 F and the maximum local 0
pool temperature did not exceed 199 F.
Although the maximum bulk pool 0
temperature is 9 F higher than the original design basis since that time Cooper has installed T-Quenchers which increase the condensation effective-ness of the suppression pool at maximum bulk pool temperatures higher than 0
0 170 F.
The maximum local pool temperature of 199 F is below tb gesent limit 0
of 200 F specified in NUREG-0661. With regard to SRV discharge transients, the limiting event is a stuck-open valve.
For the limiting event, the con-trolling parameter is the time of reactor scram. Since the Technical Specifi-0 cation requirement for reactor scram at a pool temperature of 110 F has not been changed, we conclude that the proposed change will not significantly affect the SRV discharge transients.
Summary I
Based on the evaluation described above, we conclude that the propesed increase in the maximum suppression pool temperature during normal plant 0
operation from 90 F to 950F will not adversely affect the containment design basis and is, therefore, acceptable. This hange is effective for 45 days commencing July 16, 1981.
ENVIRONMENTAL CONSIDERATIONS We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this i
determination, we have further concluded that the amendment involves an 8
action which is insignificant from the standpoint of environmental impact, and pursuant to 10 CFR Section 51.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
CONCLUSION We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the pr uacility or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration. (2) i'ere is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and se'.arity or to the health and saft!.y of the public.
vated:
July 23,1981
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