ML17156B537
| ML17156B537 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 12/06/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17156B536 | List: |
| References | |
| NUDOCS 8912180165 | |
| Download: ML17156B537 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.
94 TO FACILITY OPEPATING LICENSE NO.
NPF-14 AND AMENDMENT NO.
61 TO FACILITY OPERATING LICENSE NO.
NPF-2P PENNSYLVANIA POWER 0 LIGHT COMPANY ALLEGHENY ELECTRIC COOPERATIVE, INC.
DOCKET NOS. 50-387 AND 50-388 SUS UEHANNA STEAM ELECTRIC STATION, UNITS 1
AND 2
- 1. 0 INTRODUCT ION By letter dated October 19, 1989, Pennsylvania Power 8 Light Company requested an amendment to Facility Operating License Nos.
NPF-14 and NPF-P2 for the Susquehanna Steam Electric Station, Units 1 and 2, requested that. certain requirements of'echnical specifications (TS) be eliminated on a one time basis
<or a period of three months.
Specifically, the licensee requested relief from the operability of differential temperature sensing systems in Table 3.2.2 items 3q, 4c, 5e, Sg and 6h.
The differential temperature instruments are located in the RCIC and RWCU equipment room, the HPCI/RCIC piping area and in the main steam tunnel.
These instruments initiate an isolation siqna".
on detection of steam leaks at a predetermined di<ferential temperature.
The licensee indicated that in the course of performing RCIC room steam leak temperature pro+ile and pressure transient studies, it was found that the backdraft isolation dampers (ROID's), which isolate the room ventilation on high di~~erential pressure between the room and the atmosphere, would actuate first.
This would render the differential temperature sensing instrumentation located in the ducts inoperable.
A similar configuration also. was
<ound to exist in the RWCU equipment room, the main steam tunnel and in the HPCI/RCIC piping area.
2.0 EVALUATION The licensee has stated that
'.n addition to differential temperature instrumentation, the Susquehanna Units 1 and 2 have other safety-related diverse and redundant instrumentation systems which can detect leaks and cause automatic isolation of the a~ ected systems.
For relatively small leaks in reactor coo>ant pressure boundary in RCIC, automatic isolation wi 11 be provided by high ambient room temperature and high room cooler inlet temper ature.
For large breaks, automatic isolation will be
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provided by RCIC high steam flow, low steam supply pressure and high steam turbine exhaust vent pressure.
In addition to automatic isolation, other instruments provide alarms which are indications of reactor coolant boundary leaks.
For RCIC room, these are high ambient and high area cooler inlet temperature, high area radiation, room flood detection and backdraft isolation damper closure.
The other affected systems by this change have similar levels of diverse and redundant methods for detecting, alarming and automatically isolating steam leaks.
Additionally, the operator will be directed that the receipt of the pertinent alarms is indicative of a pressure boundary leak.
The staff has reviewed the licensee's basis as summarized.
For small leaks, automatic isolation is provided by high ambient temperature in all areas.
Some diversity in automatic isolation for small leaks would be lost due to inoperability of the differential temperature instruments.
However, this would be compensated by early backdraft isolation dampers closure alarm and directive to the operator that receipt of this alarm is indicative of a pressure boundary leak.
With another diverse indication of a steam leak, the operator will manually isolate the system.
The licensee has also committed to maintain the differential temperature instruments as described in the Technical Specification.
Based on the above, the staff considers the requested relief for a period of three months acceptable.
The staff concludes that the licensee's request for relief from the operability requirements of differential temperature monitors for a period of three months from October 19, 1989 to January 19, 1990 is acceptable.
However, the staff requires and the licensee has committed to continue to maintain the differential temperature instrumentation as required in the Technical Specification.
The licensee's commitment is documented in a letter dated October 24, 1989.
3.0 EMERGENCY BASIS In its October 19, 1989 letter, the licensee has shown that under the current plant configuration the differential temperature sensing system for leakage detection in RCIC and RWCU equipment
- rooms, main steam tunnel, and HPCI/RCIC piping area would have to be declared inoperable and the actions of Technical Specification 3.2.2 invoked.
Those actions require that each affected system be isolated.
In the case of main steam tunnel, the action would result in shutdown of both units.
Therefore, the requirement of 10 CFR 50.91 that "failure to act in a timely way would result in derating or shutdown of a nuclear unit" is satisfied.
A second requirement of 10 CFR 50.91 to suppor't an application for Technical Specification changes on emergency basis states that the licensee "... explain why this emergency situation occurred and why it could not avoid the situation..."
The discovery of the design problem which puts the differential temperature instrumentation in an non-operable condition was a result of an extensive effort by the licensee to analyze the steam leak detection and isolation system.
As a result of that effort the licensee discovered that the original design of the system was inherently incompatible with the operability requirements.
As soon as the design inconsistency was discovered, the licensee contacted the NRC to initiate a request for relief from Technical Specification requirements to avoid shutting down both the nuclear units.
The staff agrees with the licensee's basis for an emergency and finds that the proposed Technical Specification changes be processed on an emergency basis.
4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission has provided standards for determining whether a significant hazards consideration exists (10 CFR 50.92(c)).
A proposed amendment to an operating license for a facility involves no significant hazards consideration if 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 previously evaluated; or (3) involve a significant reduction in a margin of safety.
The staff has reviewed the licensee's request and concurs with the following basis and conclusions provided by the licensee in its September 14, 1987 submittal.
I.
The proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
Susquehanna is provided with many diverse and redundant methods of detecting,
- alarming, and automatically isolating systems which interface with the reactor coolant pressure boundary when a leak is detected in one of these systems.
The systems being discussed herein are RCIC, Reactor Water Cleanup (RWCU), HPCI and the Main Steam Line.
Redundancy in automatic isolation for relatively small leaks in the reactor coolant pressure boundary is provided in each case by multiple high room ambient temperature sensors.
RCIC is also provided with automatic isolation for area cooler inlet high temperature and HPCI/RCIC piping area high temperature.
Other types of signals which cause automatic system isolations for the larger break accident scenario include high steamline flow, low steam inlet pressure, and high turbine exhaust diaphragm pressure for HPCI and RCIC; high differential flow, high flow, and low reactor water level for RHR; and low reactor water level, high main steam line flow, and low condenser vacuum for the main steam line.
In addition to the automatic isolations mentioned above, other instruments provide operators with alarms which are indications of a reactor coolant pressure boundary leak in these rooms.
Pre-isolation
alarms are provided for high room ambient and high area cooler inlet temperature where applicable.
Other types of alarms which alert operators to an abnormal condition related to a steam leak in a.
particular room include high area radiation, room flood detection, room fire detection and backdraft isolation damper closure.
There are diverse and redundant methods available for detection,
- alarming, and automatic isolation o< a reactor coolant pressure boundary leak in secondary containment.
Elimination o< differential temperature monitoring does not in any way significantly reduce this capability.
II.
Create the possibility of a new or different kind of accident from any previously evaluated.
Based on the analysis presented in Item I above, the elimination of differential temperature monitoring does not significantly affect the ability to detect and isolate leaks in secondary containment.
Therefore the proposed action does not create the possibility for a new or different type of accident
~rom any previously evaluated.
III. Involve a significant reduction in the margin of safety.
The proposed action, while reducing the number of specific loops acting to isolate a leak as measured by a thermal condition, does not measurably change the probability o< successful leak detection of that condition and isolation of the leak.
Therefore the margin of safety is not reduced.
5.0 STATE CONSULTATION
The Commonwealth of Pennsylvania was consulted on October 25, 1989, and they had no comment on these Amendments.
6.0 ENV!RONMENTAL CONSIDERATION These amendments involve changes to a requirement with respect to the installation or use of a facility component located within the restricted area as defined ir 10 CFR Part 20 and changes to the surveillance requirements.
The staff has determined that these amendments involve no significant increase in the amounts, and no significant change in the types, of any e<~luents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has made a final no significant hazards finding with respect to these Amendments.
Accordingly, these amendments meet the eligibility criteria for categorical exclusion set <orth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement nor environmental assessment need be prepared in connection with the issuance of these amendments.
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7.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) the amendment does not (a) significantly increase the probability or consequences of an accident previously evaluated, (b) increase the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety margin and, therefore, the amendment does not involve significant hazards consideration; (2) there 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 wi 11 be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security nor to the health and safety of the public.
Principal Contributors:
Mohan C. Thadani and R.
Goel Dated:
December 6,
1989