ML20036B301
| ML20036B301 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 05/13/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20036B300 | List: |
| References | |
| NUDOCS 9305180494 | |
| Download: ML20036B301 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 74 TO FACILITY OPERATING LICENSE NO. NPF-62 ILLIN0IS POWER COMPANY. ET AL.
CLINTON POWER STATION. UNIT NO. 1 DOCKET NO. 50-461
1.0 INTRODUCTION
t By letter dated February 11, 1993, Illinois Power Company, et al. (IP, the licensee) proposed to amend facility Operating License No. NPF-62.
The amendment would revise the Clinton Power Station Technical Specification {TS) 3/4.3.4.2, "f nd-Of-Cycle Recirculation Pump Trip Syst Instrumentation."
The End-0f-Cjcle P.ecirculation Pump Trip (E0C-RPT) shifts the recirculation pumps from fast to slow speed upon signals from the Reactor Protection System logic. This shift is provided to insert negative reactivity by using voids in the event of a turbine top valve closure (turbine trip) or control valve fast closure (generator load reject) scram. The need for the additional negative reactivity in excess of that normally inserted on a scram is because of end-of-cycle reactivity considerations.
Flux shapes at the end-of-cycle are such that the control rods may not be able to ensure that thermal limits are maintained by inserting sufficient reactivity during the first few feet of rod travel upon a scram caused by turoine control valve fast closure or turbine stop valve closure.
The EOC-RPT function ensures sufficient negative reactivity is inserted by another means. While the EOC-RPT is only needed near the end of the fuel operating cycle, the function is availab!e for the entire fuel operating cycle.
The EOC-RPT system response time is defined as the time from initial movement of the associated turbine stop valves or turbine control valves to complete suppression of the electric arc between the fully open contacts of the recirculation pump circuit breakers. The incremer.ts that make up the system response time include:
the time from initial valve movement to reaching the trip setpoint; the response time of the sensor; the response time of the system logic; and the time allt L breaker arc suppression. The EOC-RPT e,
system response time used in il ent analyses (i.e., 140 ms) is verifiec through periodic surveillances.
Clinton Power Station Technical Specification Surveillance Requirement 4.3.4.2.3 requires that the EOC-RPT system response time test be performed at least once every 18 months.
By letter dated February 11, 1993, the licensee requested that the surveillance interval for measuring the breaker arc suppression time be increased from 18 months to 60 months.
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2.0 EVALUATION t
The current technical specifications require measuring the EOC-RPT system response time at least once every 18 months. While the licensee's proposal will still include verification of the overall system response time every 18 months, verificaticn of the breaker arc suppression time (i.e., the time j
interval necessary for breaker arc suppression from energization of the recirculation pump circuit breaker trip coll) will only be performed every 60 i
months. The licensee proposes to measure the EOC-RPT system response time every 18 months and add it to the most recent breaker arc suppression time.
l The resulting response time will be verified to be within acceptable limits.
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Part of the licensee's justification for this proposed change is based on the demonstrated reliability of the circuit breakers. Operational experience at the Clinton Power Station has demonstrated that the reactor recirculation pump i
breakers and their arc suppression function are reliable. The breakers are not routinely cycled and the short breaker arc suppression time does not appreciably change.
In addition, the licensee's practice of maintaining the circuit breakers as recommended by the manufacturer should further ensure reliability.
The licensee's justification is also based on the potential impact to plant equipment and outage schedules. Measurement of the breaker arc suppression time requires the installation of special jumpers and instrumentation.
l Accommodating the breaker arc suppression measurement may require additional j
cycling of the reactor recirculation pumps and pump breakers; thus, increasing I
wear on these components, including the reactor recirculation pump seals l
(thereby increasing the potential for seal leakage).
In addition, measurement of the ECC-RPT system response time at full power is not desirable resulting in testing being performed during plant outages.
t The staff has previously considered the benefits of verifying the individual I
time increments of the EOC-RPT system response time. The staff agrees with the licensee that measuring the breaker arc suppression during every refueling i
outage is not necessary.
Surveillance requirements found in the improved Standard Technical Specificdions for the BWR/6 reactors, identify a 60 month interval for measuring the breaker arc suppression time. Thus, the proposed change will bring the Clinton Power Station Technical Specifications into agreement with the staff's improved Standard Technical Specifications.
Therefore, based on our review, the staff finds the licensee's proposal acceptable.
3.0 STATE CONSULTATION
In acccrdance with the Commission's regulationc, the Illinois State official was notified of the proposed issuance of the amendment. The State official 4
had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
This amendment changes a surveillance requirement. The NRC staff has l
determined that the amendment involves no significant increase in the amounts, i
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 amendment involves no significant hazards consider-ation and there has been no public comment on such finding (58 FR 16862).
l Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no j
environniental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not he endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, l
and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Douglas V. Pickett
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Date:
May 13, 1993 I
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