ML20116F561
| ML20116F561 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/30/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20116F554 | List: |
| References | |
| NUDOCS 9211100378 | |
| Download: ML20116F561 (6) | |
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UNITED STATES i
NUCLEAR REGULATORY COMMISSION r
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g WASHINGTON D.C. 205 A
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 168 FACILITY OPERATING LICENSE NO. NPF-4 VIRGINIA ELECTRIC AND POWER COMPANY OLD DOMINION ELECTRIC COOPERATIVE NORTH ANNA POWER STATION. UNIT NO. 1 DOCKET NO. 50-338 l.0 IntrrJuction By letter dated October 26, 1992, the Virginia Electric and Power Company (the licer ee) requested an emergency Technical Specification (TS) change to the s
Nor'.n Anna Power Station, Unit No. 1 (NA-1).
The proposed change would revise the current NA-1 TS surveillance requirements pertaining to the auxiliary feedwater (AFW) pump relay response time testing.
The TS change is requested on an emergency basis in accordance with 10 CFR 50.91(a)(5).
The proposed change and basis for the emergency change request are provided below.
2.0 Discussion The proposed change would modify TS 4.3.2.1.3, Table 3.3-5, Item 11 surveillance requirement by adding a footnote to TS page 3/4 3-30 which would read as follows:
" Response time testing of the two relays in the auxiliary feedwater pump start circuit (Relays 3-CKT-lFWSA05 and 3-CKT-lFWSB05) due to a main feedwater pump trip is suspended for the duration of Cycle 9."
There are four events that automatically start the AFW pumps.
They are:
1) safety injection, 2) steam generator low-low water level, 3) loss of offsite power, and 4) main feedwater pump trip.
Response time testing is required to provide assurance that the protective and emergency safeguards feature (ESF)-
actuat:on functions are completed within the time limits assumed in the accident analyses.
However, the main feedwater pump trip signal is anticipatory and no credit is taken in any safety analysis for that event.
TS 4.3.2.1.3, Table 3.3-5, Item 11 requires the initiation of the AFW pumps within 60 seconds of a main feedwater pump trip.
The basis for suspending the response time test requirement for the two relays in the AFW pump start circuit for the remainder of the operating cycle involves several factors.
First, the relays have repeatedly been demonstrated 9211100378 921030 PDR ADOCK 05000338 P
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. 1 tc perform as expected during periodic functional testing as required by the TS.
The only aspect not specifically addrcssed during the functional test has been the relay response time.
Second, no credit is taken in the safety analysis for an AFW pump start on a main feedwater pump trip. Jhird, the-affected relays are HFA relays, which are used throughout the plaat.
Response
time testing of those relays in othe installed configurations has consistently demonstrated a response time, typically much less than 0.1 seconds, well within that assumed in the response time acceptance criterion that forms the basis for the TS requirement.
In addition, in August 1991, a safety injection occurred on NA-1.
The seguence of events acorder during that event documented that the required relay function occurred well within the TS requirement.
Similar information is documented for an August 1992 safety injection on NA-2.
Although the sequence of avents recorder only_
documented the first of the ti.o relays t0 actuate, it clearly showed that one relay functioned as expected and had a response time well within the required time.
Finally, the type of relays for which a TS change is being sought are reliable and generally known to have acceptable respcnse times.
Although the TS change does not pose a significant safety impact, several compensatory measures have been identified that will provide additional assurance of safe operation during the interval until NA-1 completes its-current operating cycle.
Therefore, for the remainder of the current NA-1 operating cycle, the following compensatory measures will be in piace:
(1)
The standby main feedwater pump will not be removed from service for pre-planned maintenance.
This will ensure that one standby main feedwater pump will be available to auto-start in the event of a loss of the other main feedwater pumps, (2) The Emergency Operating Procedures (E0Ps) currently require the manual start of the AFW pumps in the event that all normal feedwater flow is lost.
This requirem.:nt will be reviewed with operations personnel, and (3) Operations will review the material condition of the main feedwater pumps during each operating shift.
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3.0 Evaluation Suspending the requirement to response time test the two relays in the AFW pump start circuit due to a main feedwater pump trip for the remainder of the operating cycle does not pose a significant safety impact. No~ credit is taken j
for'it in the plant's safety analysis.
Instead, the safety analysis-assumes I
an AFW pump start on steam generator low-low level in the event of a loss of normal feedwater.
The start of the auxiliary feedwater system on a main feedwater pump trip is considered anticipatory in nature and provides a diverse protection feature not directly credited in the accident analysis.
Also, because NA-1 -is in a coastdown mode with power levels currently about -
70% and decreasing daily, any-plant transient would be initiated _ from a reduced power condition and be less severe than those that would occur starting from full power. The potential consequences of any such_ reduced-power transients' are well _within the limits of the current safety analysis.
Therefore, the staff finds the proposed change to be acceptable.
I 4.0 Emeraency Circumstances NRC regulations (10 CFR 50.91(a)(5)) require that whenever an emergency situation exists, a licensee must explain why this emergency situation occurred and why it could not avoid this situation, and the NRC will assess the licensee's reasons for failing to file an application sufficiently in advance of that event. An emergency situation exists when the NRC's failure to act in a timely way would result in derating or shutdown of a nuclear plant, or in prevention of either resumption of operation or of increase in power output up to tha plant's licensed power level.
In such cases, the NRC i
may issue a license amendment involving no significant hazards consideraticr without prior notice and opportunity for a hearing or for public comment.
Also, in such cases, the regulations require that the NRC be particularly sensitive to environmental considerations.
TS surveillance requirement 4.3.2.1.3, Table 3.3-5, Item 11 requires ESF response time testing of the auxiliary feedwater (AFW) pump circuit as a result of a main feedwater pump trip.
The test is required at least once per 18 months. On October 21, 1992, at 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br /> the licensee determined that this requirement had not been met for NA-1.
The requirements of Technical Specification 4.0.3 were immediately, invoked which permit conducting the required surveillance test within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following discovery cf the missed surveillance.
While preparing a test procedure to conduct the required surveillance, it was determined that the actuation of two relays in the AFW pero start circuit (Relays 3-CKT-lFWSA05 and 3-CKT-lFWSB05) due to a main feedwater pump trip would cause a turbine trip.
Lifting a lead to prevent relay actuation is possible; however, an error or an arc on the contacts could cause the relays to actuate and cause a turbine trip / reactor trip.
On October 22, 1992, the licensee requested a temporary waiver of compliance from TS surveillance requirement 4.3.2.1.3, Table 3.3-5, Item 11 which requires the ESF response time testing of the AFW pump circuit as a result of a main feedwater pump trip.
This was documented in the licensee's letter to the NRC, dated October 22, 1992 (Serial No.92-687). The NRC verbally approved the waiver request, followed by a formal letter to the licensee on October 22, 1992, and requested that the licensee propose an emergtncy TS change by October 26, 1992, to appropriately modify the surveillance requirement.
NA-1 is currently in coastdown operation at approximately 70% power and near the end of its operating cycle prior to the 1993 Steam Generator Replacement Outage (SGRP) scheduled to begin January 2,1993. At that time this temporary license amendment will automatically expire and the surveillance requirement 4
will again be controlling.
The surveillance test that is then required to meet the surveillance requirement is usually performed while NA-1 is in a-shutdown condition and will be performed during the SGRP.
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I Without NRC approval of the proposed emergency TS change, either the surveillance test would have to be conducted with the plant at powr.--with the possibility of a plant trip or transient--or NA-1 would be shut do'wn in accordance with the TS.
It is desirable to avoid the potential for an unnecessary plant trip.
Similarly, in the event NA-1 would be shut down, a management decision whether to begin the steam generator outage early would be required since NA-1 is near the end of its current operating cycle.
- However, initiating the outage prior to the scheduled January 2, 1993, date would result in inadequate resources being available to support the early outage, an unproductive period at the beginning of the outage as plant forces and personnel ar] mobilized, and substantial replacement power costs.
Therefore, the staff concludes that failure to act in these circumstances could reasonably be expected to result in an unnecessary shutdown of the unit and therefore meets the criteria in 10 CFR 50.91(a)(5) for an emergency situation.
5.0 Final No Sianificant Hazards Consideration Determination The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in acccrdance with the amendment would not:
(1)
Involve a significant increase in the probability or consequences or' an accident previously evaluated; or (2)
Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of safety.
The licensee proposed that the proposed TS change did not involve a significant hazards consideration, stating as follows:
"The proposed Technical Specification changes:
1.
[Do) not involve a sign'ficant increase-in the probability or-consequences of an accicent previously evaluated.
No credit is taken for the AFW pump start in the event of a mair feedwater pump trip in the accident analysis.
The type of relay in question is used throughout the plant and response time testing of HFA-type relays in other applications has consistently been well within specifications.- Therefore, not response time testing the two relays in the AFW pump start circuit during the interval until the unit shuts 'down--roughly 73 days--does not significantly affect the performance of the AFW system.
Lastly, the surveillance test is normally conducted when the unit is shutdown.
Performing the i -:
surveillance during power operation has the potential for creating an undesired transient or plant trip.
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[00] not create the possibility of a new or different kind of-accident from any accident previously evaluated.
Since.the change in the surveillance requirement will require no hardware modification (i.e., alterations to the plant configuration),
operation of the facility without those surveillance requirements does not create the possibility for any new or different kind of.
accident which has not already been evaluated in the Updated Final Safety Analysis Report (UFSAR).
Suspending the requirement for response time testing of the two relays will not result in any physical alteration to any plant system and there will not be a change in the method by which any safety related system performs its function. The design and operation of the AFW system, to include an automatic pump start due to a main feedwater pump trip, remains unchanged.
The type of relays for which [TS] change is being sought are reliable and generally known to have acceptable response times.
3.
[Do] not involve a significant reduction in the margin of safety.
The design and operation of the AFW system is not being changed.
The type of relays for which a [TS] change is being-sought are -
reliable and generally known to have acceptable response times.
When compared to the entire circuit response time, the response time of the relays is insignificant.
Further, the margin of safety will not be reduced because the accident analysis
_f assumptions will continue to be met, i.e., the AFW pumps will start within the required response time-initiated by a steam generator low-low level signal."
Based on this evaluation, the staff concurs with the licensee's analysis and, therefore, concludes that this amendment meets the criteria and, does not involve a significant hazards consideration.
6.0 STATE CCNSULTATION In accordance with the Commission's regulations, the Virginia State official was notified of the proposed issuance of the amendment.
The State official-had no comment.
7.0 ENVIRONMENTAL CONSIDERATION
This amendment changes the surveillance requirements.
The NRC staff has determined that the amendment involves 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 made a final no significant hazards finding with respect to this amendment.
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.
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8.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) the amendment does not (a) significantly increase the probability or consequences of an accident previously evaluated, (b)-increase the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce _ a safety margin and, therefore, the amendment does not involve a significant hazards consideration; (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner; and (3) 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 deferise and security or to the health and safety of the public.
Principal Crntributor: Leon Engle Date: October 30, 1992 f
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