ML20199F640
| ML20199F640 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/14/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20199F633 | List: |
| References | |
| NUDOCS 9711240283 | |
| Download: ML20199F640 (3) | |
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.... 4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 153 TO FACILITY OPLRATING LICENS.I NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY. ET AL.
MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423
1.0 INTRODUCTION
By letter dated May 5,1997, the Northeast Nuclear Energy Company, et al. (the licensee), submitted a request for changes to the Millstone Nuclear Power
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Station, Unit No. 3 Technical Specifications (TS). TS Surveillance 4.8.4.1 requires periodic testing of icwer voltage circuit breakers for all containment penetration conductor overcurrent protective devices. The proposed amendment would modify the requirements for determining the operability of lower voltage circuit breakers by using the manufacturer's curve. of current versus time to test delay trip elements, clarify the use of two pole in series testing, and expand the Bases description of the testing.
.O EVALUATION 2.1 Lono-Time and Short-Time Delav Trio Element Testing In its letter date wording of T3 Surv,d May 5, 1997, the licensee proposed a modification to the eillance 4.8.4.1.a.2.
The purpose of the proposed modification is to clarify: (a) that the requirement of the surveillance is to ensure that lower voltage circuit breakers operate within the manufacturer's time de by band width for the specified test currents; and (2) that the test currents specified in the surveillance (i.e., 300% pickup and 150% pickup) are not exact values from which the licensee may not make minor deviations.
Presently, the wording of TS Surveillance 4.8.4.1.a.2 requires: (1) that the licensee test long-time delay trip elements using an injection current equal to 300% of pickup and short-time delay tri) elements using an injection current equal to 150% of pickup; and (2) t1at the licensee verify that the circuit breakers tested operate within the time delay band width for these test currents as specified by the manufacturer.
In order to clarify the surveillance _ requirements, the licensee has proposed: (a) removing from TS Surveillance 4.8.4.1.a.2 the requirement to test long-time delay trip elements using an injection current equal to 300% of pickup and short-time delay trip elements using an injectial current equal to 150% of pickup; and (b) adding a sthtement to the bases to clarify that a nominal injection current value of 300% pickup is used to test long-time delay trip elements and a nominal 9711240283 971114 DR ADOCK 050 423
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. injection current value of 150% pickup is used to test short-time delay trip elements.
The requirements to test long-time delay and short-time delay trip elements and to verify that the circuit breakers tested operate within the time delay band width specified by the manufacturer are retained in the modified TS Surveillance 4.8.4.1.a.2.
The NRC staff h$s reviewed the licensee's proposed modification to clarify TS Surveillance 4.8.4.1.a.2 and determined that the proposed modification retains the original intent of the surveillance, which is to ensure that lower voltage circuit breakers operate within the manufacturer's time delay band width.
The purpose for specifying the values of injection current as 300% pickup and 150%
pickup in TS Surveillance 4.8.4.1.a.2 is that these values are relatively easy to attain and the heat they produce will not significantly affect adjacent poles of the circuit breaker being tested or the test results. Minor deviations from the test currents specified in TS Surveillance 4.8.4.1.a.2 (i.e., 300% pickup and 150% pickup) will not invalidate the purpose of the surveillance test, and these values of injection current are not vined by the stW f.as exact values from which the licensee may not make minor deviations.
Because the injection current values specified in the surveillance are not exact values, it is appropriate to move these specified test currents to the bases.
The staff finds t1e licensee's proposed modification for TS Surveillance 4.8.4.1.a.2 acceptable because it clarifies the surveillance without changing its intent.
The staff notes that in a conversation with the licensee on October 23, 1997, the licensee agreed that the word "approximately" be removed from the proposed wording in Bases Section 3/4.8.4.
The word "approximately" is not needed based on the above discussion of the surveillance testing requirements.
2.2 Two Pole in Series Testina By letter dated January 20, 1988, the NRC staff approved the use of te pole in series testing to determine molded case cir'.uit breaker (NCCB) c;,erability following a failure of an MCCB to pass a singie pole te'.t.
Snxifically, the staff found the series combination pole tests accept h haacse (1) the proposed specification was clarified to indicate that the series combination pole testing is only applicable to the instantaneous elements of MCC8/ unitized starters used in 480V circuits; (2) the 480V distribution system is ungrounded; (3) a single line-to-ground connection on the ungrounded system will not produce any fault current; (4) a line-to-line fault occurring u the ungrounded system will produce fault current flowing through at least two poles of the circuit breaker, which is the case for which the circuit breaker has been satisfactorily tested by the series combination pole tests; and (5) procedures exist to ensure that the 480V distribution system will be maintained as an ungrounded system.
TS 4.8.4.1.a.2 currently states that for those MCCB/ unitized starters used in 480V circuits, if single pole instantaneous test results fall outside these tolerances, additional instantaneous testing shall be conducted using two pcles in series, including A-B, B-C, and C-A phase combinations. All combination test results shall fall within the specified tolerances.
In its letter-dated May 5,1997, the licensee proposed to clarify the surveillance
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_3 specification by specifically stating that the two sole in series test determines HCCB operability. The licensee stated t1at failure of a single pole test does not result in the MCCB being declared inoperable, but does require that all combinations of two pole in series tests be performed on that MCCB. Only if the MCCB is determined to be inoperable is the subsequent testing of a representative sample of that type breaker required.
The NRC staff has reviewed the licensee's request and has determined that the proposed change clarifies the existing surveillance requirement in that it defines the necessary steps the licensee must take to determine whether the MCCB is operable or inoperable and whether subsequent testing of an additional representative sample must be conducted.
Therefore, the staff finds the change accs ytable.
2.3 Bases Chance The NRC staff has reviewed the proposed change to Bases Section 3/4.8.4 and, with the removal nf the word "approximately" as previously discussed, has no objection to the wording.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes surveillance requirements.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no siCnificant change in the types, of any effluents that may be released offsite, and thu 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 consideration, and there has been no public comment on such finding (62 FR 30637 dated June 4, 1997). 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 environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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, 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: J. Andersen Date: November 14, 1997