ML20117P660
| ML20117P660 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 09/20/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20117P659 | List: |
| References | |
| NUDOCS 9609240441 | |
| Download: ML20117P660 (5) | |
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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.115 TO FACILITY OPERATIls LICENSE NO. NPF-Il AND
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AMENOMENT NO.100 TO FACILITY OPERATING LICENSE 110. NPF-18 i
COfMONWEALTH EDISON COMPAIN LASALLE COUNTY STATION. UNITS 1 AND 2 i
DOCKET NOS. 50-373 AND 50-374
1.0 INTRODUCTION
l By letter dated April 9,1996, Commonwealth Edison Campany (Comed, the licensee) submitted a request to amend the LaSalle County Station, Units 1 and 2, Technical Specifications (TS). The proposed amendment will eliminate j
the Main Steamline Radiation Monitor (MSLRM) high radiation trip which initiates an automatic reactor scram and automatic closure of the isolation valves for the main steam lines, main steam drain lines, and the reactor recirculation water sample line.
Elimination of these functions will improve the availability of the Station by reducing spurious scrans and isolations caused by the MSLilM. Since LaSalle is proposing to eliminate automatic reactor scrams and closure of the main steam isolation valves (MSIV) on a high radiation or inoperable trip, the reference to MSLRM trip instrumentation will be removed from the TS. The existing alarms signals, which are not part of the current TS, will remain functional.
This request was submitted as the plant specific portion which, in conjunction with the General Electric Licensing Topical Report IED0-31400A, " Safety Evaluation for Eliminating the Boiling Water Reactor Main Steam Line Isolation Valves Closure Function and Scram Function of the Main Steam Line Radiation Monitor," and the NRC's May 15, 1991, Safety Evaluation (SE) on this topical report, formed the basis for the package to be evaluated.
Comed states that elimination of this trip function would result in reduced potential for unnecessary reactor shutdowns caused by spurious MSLRM trips and would increase plant operational flexibility without compromising plant 0
9609240441 960920 PDR ADOCK 05000373 P
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i 1 safety. The licensee's proposed changes a ay 1987 BWR Owners' Group. Licensing Topical Report NEDD-31400A[e based on the and NUREG-0800 In NED0-31400A, a reevaluation of the role of the MSLRM in the control rod drive accident (CRDA) analysis was performed, confirming that removal of the MSLRM scram / isolation features would not compromise CRDA consequences. The topical report also evaluated the potential effect on occupational exposure in l
the event of a sudden release of radioactive material from the fuel and concluded that the elimination of the scram / isolation features would have no
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adverse effect.
I Specifically, the licensee proposed the following changes for Units 1 and 2:
1.
Table 2.2.1-1 (Reactor Protection System Instrumentation Setpoints) -
delete setpoint requirements for " Main Steam Line Radiation - High"
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(i.e., Item 6).
2.
Bases 2.2.1 (Reactor Protection System Instrumentation Setpoints) -
l delete reference to "...high steam line radiation,..." (i.e., a section of Item 5).
3.
Bases 2.2.1 (Reactor Protection System Instrumentation Setpoints) -
l delete paragraph " Main Steam Line Radiation-High" (i.e., Item 6).
4.
Table 3.3.1-1 (Reactor Protection System Instrumentation) - delete operational condition requirements for " Main Steam Line Radiation -
High" (i.e., Item 6).
5.
Table 3.3.1-1 (Reactor Protection System Instrumentation - ACTION) -
delete action statement reference to main steam line isolation valves (i.e., ACTION 5).
6.
Table 3.3.1.2 (Reactor Protection System Response Times) - delete response time requirements for " Main Steam Line Radiation - High" (Item 6).
7.
Table 4.3.1.1-1 (Reactor Protection System Instrumentation Surveillance Requirements) - delete surveillance requirements for " Main Steam Line Radiation - High" (i.e., Item 6).
8.
Table 3.3.2-1 (Isolation Actuation Instrumentation) - delete operational condition requirements for " Main Steam Line Radiation High" (i.e.,
Item A.I.c.1).
l
'NED0-31400A, " Safety Evaluation for Eliminating the Boiling Water Reactor Main i
Steam Line Isolation Valve Closure Function and Scram Function of the Main Steam Radiation Monitor."
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NUREG-0800, Standard Review Plan 15.4.9, Revision 2, July 1981.
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Table 3.3.2-2 (Isolation Actuation Instrumentation Setpoints) - delete setpoint requirements for " Main Steam Line Radiation - High" (i.e., Item A.I.c.1).
10.
Table 3.3.2.3 (Isolation System Instrumentation Response Time) - delete response time requirements for " Main Steam Line Radiation - High" (i.e.,
Item A.I.c.1).
11.
Table 3.3.2-3 (Isolation System Instrumentation Response Time) - delete table notation "**" concerning response time testing of radiation detectors.
12.
Table 4.3.2.1-1 (Isolation Actuation Instrumentation Surveillance Requirements) - delete surveillance requirements for " Main Steam Line Radiation - High" (i.e., Item A.I.c.1).
2.0 EVALUATION The MSLRM consists of four redundant radiation detectors located on the outside of the main steam lines and external to the primary containment.
The MSLRM was designed to provide an early indication of gross fuel cladding failures. The original intent of this monitor was to mitigate the releases of the detected fuel failure by providing a scram signal to terminate the initiating event and a Main Steam Isolation Valve closure signal to assure containment of the release. However, no credit is taken for these trips and closures in any design basis event for terminating the initiating event or assuring the radioactive release remains within accepted limits.
The only design basis accident in which either the MSLRM scram or MSIV isolation functions are mentioned is the control rod drop accident. To be consistent with Section 15.4.9 of the Standard Review Plan, all of the postulated radioactive material is assumed to be released to the condenser and turbine before the isolation occurs. Hence, the automatic isolation resulting from the MSLRM signal does not affect the analyzed dose consequences from the control rod accident. However, for LaSalle the dose analysis does rely on the operator tripping the mechanical vacuum pumps within 15 minutes after receiving the high alarm from the MSLRM.
In a May 15, 1991, SE on NED0-31400A, the staff concluded that removal of the MSLRM trips that automatically shut down the reactor and close the Main Steam Isolation Valves was acceptable and that NEDO-31400A may be referenced in support of an amendment request as long as the following three conditions were met:
1.
The applicant demonstrates that the assumptions with regard to input
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values (including power per assembly, X/Q, and decay times) that are made in generic analysis bound those for the plant.
j The licensee provided a comparison of the key input parameters and the dose assessment assumptions between the LaSalle design basis and the NEDO-31400A i
e analysis. The comparison shows that on an overall basis the LaSalle dose analysis is bounded by the NED0-31400A analysis. The NEDO analysis did not include consideration of the open drain and sample lines; however, their contribution to the overall dose analysis is insignificant. The staff finds that the licensee's analysis has met the applicable requirements of condition 1, and is, therefore, acceptable.
i 2.
The applicant includes evidence (implemented or proposed operating procedures, or equivalent commitments) to provide reasonable assurance that increased significant levels of radioactive material in the main steam lines will be controlled expeditiously to limit both occupational doses and environmental releases.
In the response to Condition 2, the licensee has in place the Offsite Dose Calculation Manual (ODCM), a Radiation Protection Program, including an as low as reasonably achievable (ALARA) program, and a Radiological Environmental Monitoring Program.
Existing procedures for responding to high radiation alarms from MSLRM and offgas initiate actions through Emergency Operating Procedures which ensure that significant levels of radiation in the main steam lines (MSL) are controlled expeditiously to limit both occupational doses and environmental releases.
LaSa11e's radiation protection, chemistry, and emergency operating procedures and the 00CM will be revised, as necessary, to incorporate specific considerations to change isolation of the main steam lines from an automatic to a manual function. Thus, any significant increase in the levels of radioactivity in the MSL will continue to be promptly controlled to limit effluent releases and on-site occupational exposure.
The MSLRM alarm setpoint of 1.5 times the normal full power background will be used to initiate sampling and surveillance actions. Confirmation of elevated activity will cause administrative controls to be implemented that ensure offsite and onsite doses are maintained ALARA. Manual action to close the main steam lines and shut down the reactor will occur when all the evidence has indicated the need for isolation and shutdown. Also, procedures will require immediate notification of Radiation Protection and Chemistry upon annunciation in the Control Room of the high radiation alarm of the MSLRM or Offgas Radiation Monitor. The staff concludes that the licensee's commitment is acceptable and responsive to Condition 2 which was addressed in the Topical Report NED0-31400A.
3.
The applicant standardizes the MSLRM and offgas radiation monitor alarm setpoint at 1.5 times the nominal nitrogen-16 (N-16) background dose rate at the monitor locations, and commits to promptly sample the reactor coolant to determine possible contamination levels in the plant reactor coolant and the need for additional corrective actions, if either the MSLRM or offgas radiation monitors or both exceed their alarm setpoint.
In response to Condition 3, Comed will maintain the MSLRM alarm setpoint at 1.5 times the normal full power N-16 background dose rate. Comed will also maintain the offgas radiation monitor alarm setpoint at 1.5 times the nominal
. l background. Either of these alams will trigger entry into a procedure which will require a reactor coolant sample to be obtained and analyzed. The offgas radiation monitor alare is also set to help ensure that effluents are maintained ALARA in accordance with the ODCM. Based on a review of the licensee's commitment, the staff has determined that Condition 3 has been satisfied.
Based on a review of Coned's submittal and safety analysis, the staff concludes that there are no adverse safety implications associated with removal of the MSLRM scram and MSIV closure function since the licensee has provided reasonable assurance that the offsite radiation exposure levels are within the acceptance criteria of Section 15.4.9. of the SRP and are well within the 10 CFR Part 100 guidelines. The staff concludes that the proposed changes to eliminate the reactor scram and MSIV requirements associated with 3
the MSLRMs are acceptable.
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3.0 STATE CONSULTATION
1 In accordance with the Comission's regulations, the Illinois State official j
was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of i
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 Comission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (61 FR 25701). Accordingly, the amendments meet 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 connection with the issuance of the amendments.
5.0 CONCLUSION
The Comission 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 comon defense and security or to the health and safety of the public.
Principal Contributor: John Minns Date: September 20, 1996