ML20011E059
| ML20011E059 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 01/31/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20011E058 | List: |
| References | |
| NUDOCS 9002070203 | |
| Download: ML20011E059 (5) | |
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'I NUCLEAR REGULATORY COMMISSION WASHlWGTON. D, C. 30846 e
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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 26 T0. FACILITY OPERATING LICENSE NO. NPF-58 THE CLEVELAND ELECTRIC ILLUMINATING COMPANY ET AL.
J PERRY NUCLEAR POWER PLANT. UNIT N0. 1 DOCKET NO. 50-440
1.0 INTRODUCTION
On January 7,1990, the Perry Nuclear Power Plant Unit 1 experienced a loss of feedwater transient and reactor scram which resulted in automatic initiation of HighPressureCoreSprayandReactorCoreIsolationCooling(RCIC)atlevel2 in the reactor vessel. After approximately 37 minutes of operation, the RCIC systemisolatedbecauseofindicatedhighdifferentialtemperature(delta-T) in the RCIC equipment room. The high delta-T trip measures the temperature between the RCIC room temperature and the downstream temperature of the RCIC room cooler cooling coils.
It is intended to trip RCIC upon indication of a steam leak.
Investigation into the cause of the isolation by the licensees revealed that the trip was not caused by a steam leak in the RCIC equipment room but b decreasing temperature indication at the RCIC room cooler thermocouple (y a of about 68-70'F) with a steady ambient room temperature of about 105-107'F.
The RCIC room cooler cooling coils are cooled by the Emergency Closed Cooling (ECC) system which is in turn cooled by the Emergency Service water (ESW) system whose temperature is highly dependent on lake water temperature.
As lake temperature decreases, so does ESW temperature and correspondingly, ECC temperature.. As ECC water is being supplied to the RCIC room cooler during the wintermonths(withlaketemperaturesaslowas32*F)airflowacrossthe cooling coils causes the temperature sensed by the downstream thermocouple to decrease. During the January 7 event, the decrease was sufficiently low enough as to actuate the high delta-T trip even when no steam leak existed in the RCIC equipment room. Further investigation into the event by the licensees indicated that ECC flow to the cooler was also higher than desired (6.5 gallons per minute (gpm)versus4.3gpm).
Based on the results of start-up tests conducted in February 1987, the licensees
. attributed the spurious trip of the RCIC system to this approximately 50 percent
. higher cooler flow rate. The licensees then reestablished and verified system paramecers to be per the 1987 start-up test, declared RCIC operable, and committed to conduct a confirmatory RCIC operational test as soon as practical upon restart of the plant. On January 18, 1990, the licensees conducted their confirmatory test to verify RCIC operability. While RCIC did not isolate on high delta-T, the margin to trip was sufficiently narrow, that the licensees P
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. j could not ensure RCIC reliability during future responses to plant transients or accidents. The licensees declared RCIC inoperable and entered the Action Statement of TS 3.7.3 which requires restoration of RCIC to operable status within 14 days or be in hot shutdown within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The plant would be required to shutdown on February 1,1990.
On January 19,)1990, the licensees submitted a TS change request pursuant to I
10 CFR 50.91(a (5) describing the emergency circumstances that existed and why j
they could not be avoided. The proposed change would delete the RCIC high l
delta-T isolation feature from the TS, Based upon discussions with the staff, the licensees modified their proposed TS change on January 26, 1990 to modify the trip setpoint for the RCIC high delta-T trip.
2.0 DISCUS $10N The proposed change would temporarily revise the Reactor Core Isolation Cooling (RCIC)EquipmentRoomDifferentialTemperature(delta-T)-Highsetpointand allowable value. This change is being made on an emergency, temporary basis t
for the winter months, in order to avoid unnecessary isolations of RCIC during system operation with no steam leaks present. Theproposedsetpoint(and allowable value) bounds the range of conditions which might be experienced during any operational transients or accidents from the present time until lake temperatures reach 55'F, which usually occurs in early May. The setpoint was chosen with margin to allow for normal RCIC system operation under winter conditions, while still retaining the capability to detect and isolate leaks in the lower range of crack sizes.
A change in initial conditions for operational purposes is that the ECC outlet valve to the room cooler would no longer be throttled in winter due to concerns that fluctuations in ECC system flow rates could invalidate any calculations. With the valve throttled down to an almost closed position in the winter, even minor changes in valve position could result in a large percentage change in flow rate through the cooler.
In determining the new delta-T isolation setpoint, the licensees performed several bounding steam leak cases included a " cold" case with lake temperature at 33*F and no heat loads on ECC other than the RCIC room cooler, and a " cool" case with lake temperature at 55'F and maximum post-small-break LOCA plant l
heat loads on ECC such as the control complex chiller units.
These calculations address these bounding conditions, and also consider the RCIC room arrangement and its interconnections with adjoining rooms, heat sinks such as walls which absorb heat from the released steam, pressurization effects and HVAC impacts.
The results of these bounding cases were analyzed and the optimal setpoint for these conditions was chosen. The licensees have determined that the proposed setpoint for RCIC equipment room delta-T would be sensitive enough to detect steam leaks of between approximately 5 gpm (32*F lake temperature) and 25 gpm (55'F lake temperature).
Based upon the staff's review of the licensees' submittals, the staff finds
.that the proposed TS change will provide adequate diversity of trip function l
'for steam leaks associated with crack sizes of consideration and will also
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3 avoid spurious isolations of the RCIC system during winter operation. Thus, for the interim period until lake temperature exceeds 55'F, the staff finds the licensees' proposed TS change to be acceptable.
3.0 EMERGENCY CIRCUMSTANCES The licensees have provided arguments with respect to the emergency circumstances existing with respect to the amendment request. The licensees have stated that the plant is currently in a TS Action Statement which will require plant shutdown if the TS change is not approved prior to February 1,1990. With respect to why the emergency situation occurred and why it could not be avoided, the licensees have stated that until the RCIC differential temperature isolation actuation instrumentation failed to meet the licensees' acceptance criteria during the January 18, 1990 testing, the licensees believed that corrective action taken in response to the January 7,1990 event was sufficient to restore operability. The licensees believed that restoration of system configuration to the 1987 start-up test configuration would allow RCIC operation without spurious delta-T isolation.
Therefore, prior to January 18, 1990, the licensees' could not have foreseen or avoided the emergency situation. The staff has evaluated the licensees' arguments of the emergency circumstances associated with this amendment request and has determined that the need for immediate relief from the TS under consideration would not have been avoided and that, therefore, valid emergency circumstances exist.
4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The standards used to arrive at a determination that a request for amendment requires no significant hazards consideration are included in the Commission's Regulations,10 CFR 50.92, which states that the operation of the facility in accordance with the proposed amendment would not:
(1) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reducticn in a margin of safety.
The licensees have provided the following discussion as to whether the proposed change involves a significant hazards consideration:
(1) The proposed change does not involve a significant increase in the probability or consequences of a previously evaluated accident.
l The differential temperature isolation instrumentation provides monitoring for leaks. Therefore, the probability for leak initiation is not affected by the revision of the delta-T isolation setpoint.
The consequences of a previously evaluated accident also have not changed. The range of possible RCIC steamline breaks (up to and including a circumferential steamline break) is not affected by this proposed change. The leak detection isolation actuation instrumentation
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and alarms cover a wide range of steam piping breaks. including both small leaks and large breaks in the RCIC line. As such any signifi-cant leak in the RCIC room will continue to be sensed by redundant and diverse instrumentation with appropriate setpoints for alarm and/or isolation _ capability. As such the consequences of a RCIC I
steamline break will not change, and are still bounded by the steam-
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line break outside of containment scenario analyzed in USAR Section 15.6.4.
Thus, the consequences of a previously evaluated accident have not changed.
(2) The proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
As stated above the differential temperature isolation actuation instrumentation is a monitoring system. Revision of the isolation setpoint of this monitoring system cannot create a new type of accident, since breaks of the RCIC steamline, up to and including a circumferential break, are bounded by other accidents presently analyzed in USAR Section 15.6.4.
(3) The proposed change does not involve a significant reduction in the margin of safety. There will still exist sufficient redundant and diverse leak detection instrumentation with appropriate setpoints to detect steam leaks / breaks in the RCIC area. This change does not therefore affect any accident analysis nor does it have any effect on performance characteristics of safety systems.
As such it will not result in a reduction in the margin of safety. Also, since this change will increase the reliability of the RCIC system by reducing the possibility of an unnecessary isolation of RCIC when it is being called upon to restore reactor water level, overall plant safety will be slightly increased.
The staff has reviewed the licensees' determination with respect to significant hazards considerations. The staff has determined that the licensees have adequately analyzed the effects of the proposed change and adequately determined its safety significance. Accordingly, based on the above discussions, the Commission has determined that the proposed amendment involves no significant 1
hazards considerations.
5.0 STATE CONSULTATION
l The staff attempted to contact the State of Ohio on January 29 and January 30 E
1990 to obtain comments on this amendment request. The State of Ohio represent-l ative had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to a requirement with respect to the instal-lation or use of a facility component located within the restricted area as i
defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types,
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f 5-of any effluents that may be released offsite and that there is no rignificant t
increase in individual or cumulative occupational radiation exposure. The Comission has made a determination that this amendment involves no significant hazards consideration and there has been no public coment on such finding.
Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in c
connection with the issuance of this amendment.
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7.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be 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 this amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
T. Colburn Dated: January 31, 1990 t
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