ML20141P106
| ML20141P106 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/13/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20141P105 | List: |
| References | |
| NUDOCS 8603190008 | |
| Download: ML20141P106 (3) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION j
WASHINGTON, D. C. 20065
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 36 TO FACILITY OPERATING LICENSE NO. NPF-11 COMMONWEALTH EDISON COMPANY LA SALLE COUNTY STATION, UNIT 1 DOCKET NO. 50-373
1.0 INTRODUCTION
By letter dated January 9, 1986, Commonwealth Edison Company (licensee) proposed an amendment that would change the La Salle County Station, Unit 1 Technical Specifications to revise the response time for the Main Steam Line Low Pressure trip function in the Technical Specifications Table t
3.3.2-3 from 1 to 2 seconds.
2.0 EVALUATION La Salle Unit 1 is currently shutdown performino refueling and is replacing environmentally non-qualified equipment with qualified eouipment as required by License Condition 2.C.(11) during this first refueling outage. The Main Steam Line Low Pressure switches are scheduled to be changed from the non-qualified Barksdale model currently installed to environmentally qualified Static-0-Ring (SOR) pressure switches.
These switches protect the reactor core by closing the Main Steam Isolation valves during a deoressurization transient caused by a failure of the pressure regulator.
These same Barksdale switches were replaced with SOR switches in Unit 7 in June 1985. At that time, the licensee discovered that the new SOR pressure switch triD function could not Consistently meet the less than or equal to 1 second response time required by the Technical Specifications in Table 3.3.2-3.
The licensee took numerous steps to obtain conformance with the 1 second response time. These steps included testing at various ramp rates, discussions with the instrument supplier and General Electric Company (l.a Salle's vendor), and additional retesting and various configurations (without instrument snubbers and with modified snubbers). All of this effort was to no avail. The switches' averace response time remains at or about 1.1 seconds.
The Final Safety Analysis Report of the Main Steam Isolation Valve (MSIV) closure transients includes:
(1) the overpressure aspects from rapid closure from 3 seconds of MSIV closure at 105 percent steam flow conditions, and (2) the long-term MSIV closure where 105 percent steam flow is assumed to persist for 30 seconds due to loss of alternating current power and other adverse failures indicating acceptable results. The safety analysis of concern to this Technical Specification Table 3.3.2-3 A.1.C(2) apportions the response time as follows:
Sensor - 1.0 second MSIV
- 13.0 seconds (actually Diesel Generator start interval dominates the MSIV actual closure time which is 3 to 5 seconds).
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_ The safety analysis for the Main Steam Line Low Pressure isolation via MSIVs was done at 825 psi pressure (analytical minimum limit to assure validity above the GEXL fuel correlation threshold). The allowable Technical Specifi-cation setpoint is 834 psig and the nominal setpoint is 854 psig. At the analytical limit of 825 psi, the 30 second MSIV closure time (total of sensor and valve and its auxiliaries) is acceptable. At this condition, the present Technical Specification utilizes 14 total seconds of this 30 second safety analysis interval. The revised Technical Specification extends this utilization to 15 total seconds-(2 seconds for the sensor and the same 13 seconds for the valve) of the 30 second interval. This is an insignificant chance in the pre-analyzed safety envelope because the pro-tective isolation action (MSIV closure) occurs prior to the time when the system pressure decreases to the analytical limit (825 psi) even from the lowest allowable Technical Specification value (834 psig).
The purpose of the low pressure isolation is to protect the fuel by restric-ting reactor operation to the pressure regimes covered by the data base for the GEXL correlation. Because the analyses using the 30 second MSIV closure time are still applicable, the staff concludes that use of the GEXL correla-tion is still valid. We find the proposed Technical Specification chrnge acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change in the installation and use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. The staff has determined that this amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumula-tive occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accord-ingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.2?(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (51 FR 3712) on January 29, 1986.
No public comments were received, and the state of Illinois did not have any comments.
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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 endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regula-tions and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
A. Bournia, RWR Proiect Directorate No. 3. DBL Dated: We : 3
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