ML20046C204
| ML20046C204 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/15/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20046C199 | List: |
| References | |
| NUDOCS 9308090340 | |
| Download: ML20046C204 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS. 178 AND 181 TO FACILITY OPERATING LICENSE NOS. DPR-44 and DPR-56 PHILADELPHIA ELECTRIC COMPANY PUBLIC SERVICE ELECTRIC AND GAS COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION. UNIT NOS. 2 AND 3 DOCKET NOS. 50-277 AND 50-218
1.0 INTRODUCTION
By letter dated February 26, 1993, the Philadelphia Electric Company (the licensee) submitted a request for changes to the Peach Bottom Atomic Power Station, Unit Nos. 2 and 3, Technical Specifications (TS).
The requested changes would revise the surveillance testing interval for the Logic System Functional Tests (LSFTs) for the 1) Primary Containment Isolation System (PCIS), 2) Core Standby Cooling System (CSCS), 3) Control Rod Block Actuation System and 4) Radiation Monitoring System actuations. The revised surveillance tests will require the performance of the LSFTs once-per-operating-cycle (which is currently defined as 550 days with 25% grace period) rather than every 6 months as is currently required.
2.0 EVALUATION 2.1 Definition The licensee proposed to change the TS Section 1.0 definition of Logic System Functional Test.
The proposed change clarifies the definition so that the requirement to test all relays and contacts from sensor through actuated device is clearly called out.
In addition, the definition is expanded to state that the test may be performed as a series of sequential, overlapping or total system steps such that the entire logic system is tested.
The licensee did not propose any changes to the way in which LSFTs are currently performed at Peach Bottom. The proposed change adopts most of the wording of the definition of Logic System Functional Test provided in the improved Standard Technical Specifications (NUREG-1433) for BWR-4 reactors.
The licensee chose to maintain the requirement to test the actuated device as part of the LSFT.
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.. The staff concludes that the change to the TS definition of Logic System Functional Test clarifies the existing definition and, therefore, is acceptable.
2.2 Surveillance Interval 2.2.1 Primary Containment Isolation System Technical Specification Table 4.2.A specifies the requirement to perform LSFT on primary containment isolation systems (PCIS). The affected systems are: 1) main steam isolation valves, main steam line drain valves and reactor water sample valves, 2) residual heat removal (RHR) isolation valves, shutdown cooling valves and head spray valves, 3) reactor water cleanup (RWCU) isolation valves, 4) drywell isolation valves, traversing incore probe (TIP) i withdrawal valves, atmospheric control valves and sump drain valves and 5) standby gas treatment and reactor building isolation valves. The current frequency for these LSFTs is once-per-six-months.
2.2.2 Core and Containment Coolino Systems Technical Specification Table 4.2.B specifies the requirement to perform LSFTs on core and containment cooling systems (CSCS). The affected systems are: 1)
Core Spray, 2) low pressure coolant injection (LPCI), 3) containment cooling,
- 4) high pressure coolant injection (HPCI), 5) HPCI system isolation, 6) reactor core isolation cooling (RCIC) isolation, 7) automatic depressurization (ADS) and 8) area cooling for safeguards systems. The current frequency for these LSFTs is once-per-six-months.
2.2.3 Control Rod Block i
Technical Specification Table 4.2.C specifies the requirement to perform an l
LSFT on the control rod block function. The control rod blocks prevent excessive control rod withdrawal so that the minimum critical power ratio (MCPR) does not decrease to the fuel cladding safety limit. The trip logic 1
for the control rod block is such that any one trip out of six average power range monitors (APRM), eight intermediate range monitors (IRM) or four source range monitors (SRM) will cause a rod block. The current frequency for this LSFT is once-per-six-months.
2.2.4 Secondary Containment Technical Specification Table 4.2.D specifies the requirement to perform LSFTs on certain systems related to secondary containment. The affected systems are
- 1) reactor building isolation and 2) standby gas treatment (SBGT) as actuated by the radiation monitoring system.
Reactor building isolation and SBGT initiation are triggered by the radiation monitoring system for the refueling floor or the reactor building below the refuel floor. The current frequency for these LSFTs is once-per-six-months.
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2.2.5 Evaluation of Extended Interval The licensee proposed to extend the interval for these tests to once per operating cycle. The current TS definition of an operating cycle is once-per 550 days with a 25% grace period.
By letter dated October 19, 1992, the licensee applied for a TS amendment that would, among other things, revise the definition of "Once Per Cycle" to "at least once per 732 daye.." with a 25%
grace period. That application is currently under staff revra.
In the February 26, 1993 application, the licensee provided a justification to extend LSFT frequencies to once-per-operating cycle for an interval of 24 months with a 25% grace period. The licensee conducted a review of LSFT surveillance test history and found no evidence of excessive random equipment failure re.tes.
In addition, the licensee cited the redundant design of the i
systems involved as additional assurance that impact on system availability would be small.
Logic systems are comprised of detection devices activated by.a certain physical condition (e.g., pressure switches, temperature switches, etc.) and decision making relay networks that will cause a safety system ~ component or device (e.g., pump, valve, etc.) to operate when needed. Each relay in a
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decision making logic network has one or more contact pairs associated with it. A logic system functional test is a test of all relays and contacts in these decision makir.g networks to assure that the system will operate as designed upon demand.
Industry reliability studies for boiling water reactors (BWRs), prepared by the BWR Owners Group (NEDC-30936P) show that the overall safety systems reliabilities are not dominated by the reliabilities of the logic systems, but by that of the mechanical components, (e.g., pumps and valves), which are i
consequently tested on a more frequent basis.
Changing the frequency of various LSFTs form once-per-six-months to once-per-operating-cycle increases the surveillance interval.
However, the reliability of the mechanical components of a safety system remain unchanged because these components are functionally tested or calibrated at unchanged intervals.
Since the probability of a relay or contact failure is small relative to the probability of a mechanical component failure, increasing the logic system 1
functional test interval represents no significant change in the overall safety system unavailability.
The existing LSFT procedure requires installing jumpers or lifting leads to accomplish the verification of the relays and contacts operability.
By changing the LSFT surveillance to be performed during plant shutdown, it will reduce the potential for inadvertent transients or safety system actuations induced by human errors during testing.
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.. The staff recognizes that logic system functional tests are complex surveillance tasks which require numerous temporary alterations and complicated administrative controls. The complexity of the surveillance tests has a significant potential for undesired actuations and operator error which can induce undesirable plant transients.
In addition, system redundancy is reduced during the performance of the test.
LSFTs are best performed during conditions that apply during a plant outage, which reduces the potential for unplanned transients at power.
Performing the LSFTs at intervals of up to 24 months with an additional 25% grace period, is consistent with the interval that the NRC has determined to be adequate to achieve the goal of high safety system availability, considering uncertainties in component failure rates, uncertainties in common mode failure rates, and reduced redundancy during testing and component wear caused by testing. The staff therefore, finds the proposed increase in the surveillance interval for the affected LSFTs to 24 months with a 25% grace period, acceptable.
The staff finds the licensee's justification for performing the subject LSFTs on a 24-month interval acceptable for the reasons described above. However, in the February 26, 1993, application, the licensee specifically requested to change the frequency of the subject LSFTs to "once-per-operating-cycle." The existing TS definition of " operating cycle" is "550 days" (approximately 18 months).
The licensee's October 19, 1992, proposal to change the definition of operating cycle to "732" days (approximately 24 months) is still under staff review due to the number of other surveillance requirements which are based on the operating cycle. Therefore, since the interval for the LSFTs of 24 months was acceptable, the lesser interval of 18 months is also acceptable, the staff finds acceptable and approves the licensee's specific proposal to revise the surveillance frequency of the subject LSFTs to "once-per-operating-cycle" and notes that until further action on the October 19, 1992, i
application, the definition of " operating cycle" remains "550" days.
3.0 STATE CONSULTATION
J In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.
The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a surveillance requirement. The NRC staff has determined that the amendments involve no significant increase in the amounts, ind 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 hazaeds consideration, and there has been no public comment on such finding (58 FR 16868). 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.
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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, i
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:
J. Shea Date: July 15, 1993 P
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