ML20216G977
| ML20216G977 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 04/14/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20216G964 | List: |
| References | |
| NUDOCS 9804200538 | |
| Download: ML20216G977 (2) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION
'2 WASHINGTON, D.C. 30666 0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATEDTO AMENDMENT NO.124 TO FACILITY OPERATING LICENSE NO. NPF-11 AND 1
AMENDMENT NO.109 TO FACILITY OPERATING LICENSE NO. NPF-18 COMMONWEALTH EDISON COMPANY LASALLE COUNTY STATION. UNITS 1 AND 2 DOCKET NOS. 50-373 AND 50-374
1.0 INTRODUCTION
l By letter dated December 12,1997, Commonwealth Edison Company (Comed, the licensee) submitted a request for changes to the LaSalle County Station, Units 1 and 2, Technical Specifications (TS). The proposed changes would modify the bypass logic for Main Steam Line l
Isolation Valve (MSIV) Isolation Actuation Instrumentation on Condenser Low Vacuum as stated in Note
- of TS Tables 3.3.2-1 and 4.3.2-1. TS 3.3.2 states that the Condenser Vacuum - Low trip i
l function is applicable in Modes 1,2, and 3, but may be bypassed in Modes 2 and 3 with reactor l
steam pressure 51043 psig and all turbine stop valves closed. The purpose of automatic closure of the MSIVs when condenser vacuum is low is to prevent overpressurization of the main condenser.
l Closure of the MSIVs prevents the addition of steam that would lead to additional condenser pressunzation and possible 'spture, thereby preventing a potential radiation leakage path following an accident. This automatir. 2ction can be bypassed by a manual switch under the following conditions: (1) the reactor Mode switch is not in the run position, (2) all turbine stop valves are closed, and (3) all four channels of reactor vessel steam dome pressure switches are 51043 psig.
2.0 EVALUATION The bypass interlock associated with reactor vessel steam dome pressure was included in the original design of LaSalle and was based on experience at a European BWR1 in the 1960's where difficulty was encountered in controlling reactor power above a specified pressure without pressure control. Subsequent testing at a US facility indicated that this condition was not experienced at that l
site and General Electric modified the design of all BWR plants to eitherincrease the pressure trip l
point to the high pressure scram setpoint or remove all circuits associated with the Hot Standby l
pressure trip. LaSalle implemented the first option and increased the pressure trip point to 1043 psig, the scram setpoint for reactor vessel steam pressure - high. LaSalle now proposes to implement the second option and remove all circuits associated with this bypass interlock and l
delete the TS requirement.
l The current setpoint of 1043 psig renders this interlock essentially ineffective, if reactor vessel pressure exceeds 1043 psig, an automatic scram will occur and the plant will be in a condition in which the automatic isolation on Condenser Vacuum - Low is not applicable. The remaining interlocks will ensure that this function is not bypassed in an inappropriate condition. The requirement that the function be operable during Mode 1 and during Modes 2 and 3 with the turbine stop valves (TSVs) open will ensure that an MSIV isolation will occur on low condenser vacuum in thosa conditions that could resuit in damage to the condenser. Because the interlock related to reactor vessel pressure is not necessary for safety of the plant, its deletion is acceptable.
9004200538 980414 PDR ADOCK 05000373 P
. The current TS state that the function may be bypassed with ali TSVs closed in Modes 2 and 3.
The licensee proposes to revise the wording from " closed" to "not full open" based on the actual logic. The instruments that measure closure of the TSVs are set to actuate certain actions, includmg isolaten bypass on less than or equal to 5 percent closed. The same instruments are used to actuate the Reactor Protection System when the turbine stop valves begin to close. TS 2.2.,1 specifies a setpoint for TSV closure trip of less than or equal to 5% closed to initiate actens required upon closure of the TSVs. TS 4.3.1 requires verification of this setpoint through surveillances..
)
The current surveillance requirement for channot t slibration and functional tests of the condenser vacuum - low isolation instrumentation in Table 4.3.2.1-1 is modified by a footnote that explains that the surveillance is required in Modes 2 and 3 when reactor steam pressure is greater than 1043 psig and/or any turbine stop valve is open. The licensee has proposed rewording this footnote to be consistent with the footnote in Table 3.3.2-1 to state that the surveillance is not required when all turbine stop valves are not full open. When all TSVs are not full open, all channels can be bypassed in which case the trip function is not active The proposed footnote also deletes reference to the reactor steam pressure interlock, as discussed above. The proposed footnote is consistent with the footnote used in Table 3.3.2-1, " Isolation Actuation Instrumentation" and is an accurate representation of the trip logic. Therefore, the proposed change is acceptable.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the lilinois State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments chan0e a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve 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 cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (63 FR 6982). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(g). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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 public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and secunty or to the health and safety of the public.
Principal Contributor: D. Skay Date:
April 14, 1998