ML20211P335
| ML20211P335 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 10/09/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20211P312 | List: |
| References | |
| NUDOCS 9710200168 | |
| Download: ML20211P335 (4) | |
Text
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t UNITED STATES
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NUCLEAR RE2ULATORY COMMISSION WASHINGTON. O.C. 30846-4001 o% **.../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENOMENT NO.121 TO FACILITY OPERATING. LICENSE NO. NPF-11 AND AMENDMENT NO.106 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
By letter dated July 1,1997, Commonwealth Edison Company (Comed, the licensee) requested changes to the Technical Specifications (TS) for the LaSalle County Station, Units I and 2.
The proposed changes reflect modifications to the Control Room Ventilation Air intake Radiation Monitoring System logic that are being made to restore separation and redundancy of the radiation monitoring trip systems.
The Main Control Room Atmospheric Control System (MCRACS) is designed to limit the exposure of control room personnel to less than the limits specified in General Design Criteria 19 of 10 CFR Part 50, Appendix A.
The system consists of two 100 percent heating, ventilttion, and air conditioning (HVAC)iontrains, each supplied through its own ventilation intake.
The HCRACS radiat monitoring instrumentation continuously monitors outside air intake and, upon detection of high radiation, isolates the control room from the normal outside air by closing dampers and initiates the Emergency Makeup Mode of the Control Room Emergency Filtration System.
The MCRACS radiation monitoring instrumentation consists of four radiation monitors in each intake, in the current configuration, if any two monitors in an intake sense radiation above the setpoint of 3.5 mR/hr, the system will trip to initiate the protective features. Therefore, the current design is a two-out-of-four logic.
The licensee has determined that the current design does not ensure redendancy and separation because all four monitors in an intake are electrically connected. Therefore, a single fault in one radiation monitor could result in a loss of the automatic isolation function for that intake. The licensee has detennined that the logic must be modified to meet single failure criteria.
The revised design will consist of two inde>endent trip systems per intake, each consisting of two monitor r.nannels. Tae revised logic will require that both channels in a trip system indicate high radiation for the trip system to actuate. Actuation of either trip system will result in isolation of that intake.
The revised logic will maintain the current two-out-of-four design 9710200168 971009 PDR ADOCK 05000373 P
and will meet the single failure requirements as described ^in the Safety Evaluation Report.
2.0 EVALVATf,;d Current TS Table 3.3.7.1-1 requires two channels per i 6ake to be operable at all times except when a unit is in cold snutdown or urueled. Due to the modification to the system design, and to clarify the system requirements, the licensee has proposed to modify the TS to requir' that two channels per trip system per train (intake) be operable.
The current trip logic configuration consists of four monitors divided into two trip systems.
The licensee had implemented a Technical Specification Clarification in 1993 that defined a trip channel as consisting of two radiation monitors. Therefore, the current TS was interpreted to require all four monitors operable, but the TS wording is unclear.
In the proposed modification, each radiation monitor is considered a channel. The proposed TS will require that two channels per trip system per train be operable and the Bases will clarify that each intake consists of two trip systems.
The proposed TS requirement is consistent with the proposed design change which will require both channels in a trip system to actuate the protective actions, and is consistent with the intent of the current TS. The wording of the proposed TS will also clarify that both trains (intakes) are required to be o)erable to ensure operability of the system, consistent with the current TS.
T.1e proposed change is an enhancement of the current TS and is acceptable.
The current TS contains a footnote (**) which allows a channel to be placed in an inoperable status for up to 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for the performance of required surveillance testing without placing the Trip System in the tripped condition, provided at least one other operable channel in the same Trip System is monitoring that Trip Function. This footnote allows a channel to be inoperable for up to 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> without placing the control room emergency filtration system in the pressurization mode.
This footnote is based on surveillance intervals specified in General Electric Topical report GENE-770-06-1, " Bases for Changes to Surveillance Test Interals and Allowed Outage Times for Selected Instrumentation Technical Specifications" and was approved by Amendment Nos.104 and 90 to the LaSalle TS.
This footnote uses t1e generic term " Trip System" as defined in GENE-770-06-1 to refer to the train of instrumentation logic which will actuate the protective function.
Therefore, in the current and proposed TS, the Trip System referred to in this footnote is a train of MCRACS radiation moritoring instrumentation and the Trip function is initiation of the automatic actions to close the intake dampers. The footnote requires that the train maintain automatic initiation capability (i.e., a channel may not be removed from service for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> for surveillance testing if the redundant trip system is inoperable). The Bases for this TS clarify this requirement. This footnate is not revised in the proposed TS and is appliceble to the modified logic configuration and proposed TS.
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The licensee also proposed to revise action 70 in Table 3.3.7.1-1 for clarification. The current action requires that with one of the required monitors inoperable, the inoperable channel must be placed in the downscale tripped condition within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and must be restored to operable status within 7 days, or, within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, the control room emergency filtration system must be operated in the pressurization mode.
The wording in the t.urrent TS is unclear as to which are the required monitors and what constitutes a channel.
In addition, placing a channel in the downscale i
tripped condition does not result in a trip of that channel and a downscaled channel is not available to initiate the protective actions.
Therefore, a Technical Specification Clarification was prepared in 1993 to specify actions that would ensure automatic trip capability was maintained.
The licensee proposed a revised action 70(a) which would require that with the number of operable channels one less than the minimum required, the inoperable channel must be placed in the tripped condition within one hour.
Revised action 70(b) would require that with both channels in a trip system inoperable, the trip system must be declared inoperable and must be restored within 7 days, or, within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> the control room emergency filtration system must be operated in the pressurization mode.
The proposed action maintains the intent of the current TS since, under the current logic configuration, a trip system is considered to be a channel. The proposed action ensures that automatic trip capability is maintained as long as one trip system in the train is operable.
If automatic trip capability can not be maintained (i.e., if bath trip systems in a train become inoperable) the licensee is required to place the centrol room emergency filtration system in the pressurization mode of operation within one hour in accordance with action 70(c). This is consistent with the current TS action which requires that with beth of the required monitors inoperable, the control room emergency filtration system must be placed in the pressurization mode within one hour.
The proposed TS maintains the current requirements ard allowed outage times and provides clarification. Tim proposed actions ensure that automatic trip capability is maintained and are, therefore, acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official 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 a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has datermined that the amendments involve no vqnificant increase in the ar.ounts, 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 curalative occupational radiation exposure. The Commission has previoucly issued a proposed finding that the amendments involve no significant hazards consideration, and there has been
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no public comment on such finding (62 FR 45{55). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).- purruant to 10 CFR 51.22(b), no environmental im)act statement or environmental assessment need be ptepared in connection wit 1 the issuance of the amendments.
5.0 CONCLUS10N 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 security or to the health and safety of the public.
Principal Contributor:
D. Skay Date:
October 9, 1997 4
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