ML20203H932
| ML20203H932 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 02/12/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20203H928 | List: |
| References | |
| NUDOCS 9902230154 | |
| Download: ML20203H932 (3) | |
Text
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UNITED STATES
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30eeH001 J
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.130 TO FACILITY OPERATING LICENSE NO. NPF-11 AND AMENDMENT NO.114 TO FACILITY OPERATING LICENSE NO. NPF-18 l
j COMMONWEALTH EDISON COMPANY I
LASALLE COUNTY STATION. UNITS 1 AND 2 DOCKET NOS. 50-373 AND 50-374
1.0 INTRODUCTION
By letter dated October 16,1998, Commonwealth Edison Company (Comed, the licensee) requested changes to the LaSalle County Station, Units 1 and 2, Technical Specifications (TS).
The proposed changes affect TS Sections 3.3.1 (Reactor Protection System Instrumentation) and 3.3.4.2 (End-Of-Cycle Recirculation Pump Trip System Instrumentation) by revising the setpoint below which the Turbine Control Valve (TCV) and Turbine Stop Valve (TSV) closure se, ram signals and the End-of-Cycle Recirculation Pump Trip (EOC-RPT) signals are automatically bypassed. The setpoint is measured using tutt>ine first stage pressure and is currently set at 140 psig which corresponds to 30 percent rated thermal power. The licensee proposes to reduce the setpoint to 25 percent rated thermal power and de. ate the reference to turbine first stage pressure from the TS. In addition, to encure that the trips are enabled when they are needed, a requirement is proposed to be added to periodically ver;fy that TCV and TSV scram trip functions and the EOC-RPT functions are not bypassed when at greater than or equal to 25 percent rated thermal power. The licensee statea that the reduction of the setpoint from 30 percent to 25 percent will reduce the complexity of reload analyses and increase operating flexibility at low power levels.
2.0 EVALUATION Either a generator load rejection or turbine trip will initiate closure of the TSV and fast closure of the TCV to protect the turbine. Closure of the TSVs and fast closure of the TCVs results in the loss of a heat sink that produces reactor pressure, neutron flux, and heat flux transients. To protect the reactor from overpressure due to positive reactivity, a reactor scram is initiated on TSV closure and TCV fast closure in anticipation of the transients that would result. In addition, the EOC-RPT instrumentation initiates a recirculation pump trip to reduce the peak reactor pressure and power resulting from a generator load rejection or turbine trip.
The scram that results from the TSV closure or TCV fast closure reduces the amount of energy required to be absorbed and, along with the actions of the EOC-RPT system, ensures that the minimum critical power ratio (MCPR) safety limit is not exceeded
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9902230154 990212 PDR ADOCK 05000373 p
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i The TSV closure and TCV fast closure scram functions and EOC-RPT must be enabled during
. power operation. However, at low power levels, the scram and RPT may be bypassed because the severity of pressurization transients is reduced and because the majority of steam can bypass the turbine.. LaSalle, Units 1 and 2, have approximately 30 percent bypass capability.
- Therefore, a scram on TCV or TSV closure is not needed unless power is greater than i
30 percent as adequate steam bypass capacity is available. The current TS allow the TSV-Closure Scram, TCV-Fast Closure Scram, and EOC-RPT to be bypassed at less than j
30 percent rated thermal power (P,,,,,). Comed proposes to reduce the current setpoint to l
25 percent. This reduction from 30 percent to 25 percent provides a more conservative setting for the TSV closure and TCV fast closure scram bypass setpoints and EOC-RPT and will reduce the overpressure effects on scram actuation.
t The reduction in P.,,,,, will impact the power dependent core thermal operating limits. LaSalle utilizes power and flow dependent thermal limits (ARTS). The licensee submitted a revised General Electric (GE) analysis of the ARTS Improvement Program for LaSalle that included an evaluation of the effects of the change in P.,,
. The analysis was performed to validate a linear extension of the generic thermal limits from 30 percent power down to 25 percent. New thermal limits were determined for LaSalle, Unit 1, Cycle 8, through the use of the NRC-approved ODYN reactor dynamic model for the limiting power dependent transients, Load Rejection Without Bypass and Feedwater Controller Failure events. With P.,,,,, at 25 percent power, the transient consequences for analyses between 25 percent and 30 percent power were much less severe than with P.,,,,, at 30 percent rated thermal power. This analysis is representative of limits that will be determined each cycle as part of the normal reload licensing process. For Unit 2 and future reloads, the licensee will evaluate these transients under 10 CFR 50.59 as part of the normal reload licensing process and submit the revised thermal limits in the Core Operating Limits Report in accordance with TS 6.6.A.6.d.
The current applicability and action statements for TCV and TSV closure and EOC-RPT trip instrumentation refer to turbine first stage pressure as a measurement of rated thermal power.
While the P.,,,,, setpoint will continue to be measured by turbine first stage pressure, the reference will be deleted from the TS. Listing of the pressure is an unnecessary detail and its deletion is consistent with the format of this specification in NUREG-1434, ' Standard Technical Specifications, General Electric Plants, BWR/6", Revision 1.
The licensee also proposes to revise the wording of TS Table 3.3.1-1, Note (i) and Table 3.3.4.2-1, Note (b). The revised notes will state that the scram signals shall not be automatically bypassed at greater than or equal to 25 percent of Rated Thermal Power, rather than stating that they shall be automatically bypassed below the P.,,,,, setpoint. This change ensures that the scram function and EOC-RPT function will be available and will not be automatically bypassed above 25 percent rated thermal power. The proposed wording is consistent with NUREG-1434.
j The licensee also proposes to add a surveillance to ensure that these functions are not j
bypassed at greater than or equal to 25 percent rated thermal power. The proposed j
surveillance will require verification once per 18 months that the TSV-Closure and TCV-Fast i-Closure trip functions are not bypassed when thermal power is greater than or equal to 25 j
percent of rated thermal power. This addition is also consistent with NUREG-1434.
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_. _ _ _ _ _. _ _ _ _ _ _.. _ _ _ _. _ _. _ _ _. _ _ _ _ The reduction in P. from 30 percent to 25 percent of rated thermal power will continue to ensure that the reactor is protected from overpressurization due to closure of the TSV or fast closure of the TCV during operation while still ensuring that unnecessary scrams and recirculation pump trips do not occur at low power levels. The changes to eliminate the reference to first stage turbine pressure and reword the applicability statement are administrative changes consistent with NUREG-1434. The addition of a surveillance to ensure that these functions are not bypassed at greater than or equal to 25 percent rated thermal power is conservative. Therefore, the proposed TS changes are 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 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 64108). 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 CONCLUSIQN 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: February 12,1999 i