ML20044A983
| ML20044A983 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/10/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20044A982 | List: |
| References | |
| NUDOCS 9007170121 | |
| Download: ML20044A983 (6) | |
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.jAFETYEVALUATIONBYTHEOFFICEOFNUCLEARREACTORREGULATION RELATED TO AMENDMENT NO. 31 TO FACILITY OPERATING LICENSE NPF-68 AND AMENDHENT NO. 11 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER COMPANY. ET AL.
V0GTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 i
DOCKET NOS. 50-424 AND 50-425
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1.0 INTRODUCTION
By letter dated May 25, 1990, Georgia Power Company (GPC), et'al..(the licensee),
requested a Technical S Generating Plant (VEGP)pecification (TS) amendment to allow the Vogtle Electric Emergency Diesel Generator (EDG) high jacket water temperature (HJWT) trip to be bypassed to minimize the potential for spurious diesel generator trips in the emergency start mooe. Specifically, the requested change would revise TS 4.8.1.1.2h(6)(c) to aod a note (Hf) that states "the high jacket water temperature trip may be bypassed." The requested change results from GPC's desire to install a modification that adds isolation valves in the instrument tubing between the EDG HJWT elemtnts and the local EDG
, control panel.
The installed valves would then br. normally closed so that the HJWT sensors would not provide input to the EDG crip logic for emergency start signals. The isolation valves may be opened to enable the jacket water trip l
for non-emergency manual starts or EDG surveillance tests, t
2.0: EVALUATION The criteria which govern whether an EDG trip can be bypassed for emergency or normal EDG. starts are provided in Revision 2 of Regulatory Guide 1.9.
Position 7 of Regulatory Guide 1.9, Revision 2, states that all diesel generator protective trips should be either bypassed when the diesel generator is required for a design-basis event or implemented with two or more independent measurements with i
-coincident logic provisions. All protective trips are allowed during periodic testing. The allowed exceptions to the above requirements for bypassing are diesel engine over* peed and generatur differential current. Currently, all the i
protective trips on the VEGP EDGs except engine overspeed, generator differential, low lube oil pressure, and HJWT are bypassed during an emergency start. The low lube oil pressure and HJWT trips are implemented by three independent measurements for each trip parameter. Actuation of these trips is initiated by two-out-of-three coincident logic. The current design satisfies the requirements of Position 7 of Regulatory Guide 1.9.
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2-Regulatory Guide 1.9, Revision 2, allows the HJWT trip to be bypassed under accident,. conditions provided the operator has sufficient time to react appro-priately m an abnormal diesel generator condition. The proposed TS change and associatec plant modification would bypass the HJWT trip for all emergency starts while niaintaining the local and control room alarms for abnormal jacket water temperature. The alarms would provide the operator with an indication of abnormal conditions and provide sufficient time for the operator to take actions to mitigate the condition. Althougl. there is an increased potential for diesel generator damage due to loss of engine cooling during energency starts, the operating experience to date at Vogtle indicates that it is outweighed by the increased EDG reliability achieved with the comnensurate benefit to overall plant i
safety.
Accordingly, the NRC staff finds that the proposed TS change to Surveillance Requirement 4.8.1.1.2h(6)(c) and the associateo plant modification meet the intent of Regulatory Guide 1.9, Revision 2, and are acceptable.
With regard to the impact of the proposed TS change on events postulated in the updated VEGP Fins 1 Safety Analysis Report (FSAR), the bypassing of the HJWT trip will not affect the capability cf the EDG to mitigate those design basis events in which the preferred off site power source is postulated to fail. The accident analyses postulated in the VEGP FSAR do not take credit for a restart cf an EDG.
If an EDG should fail from a loss of engine cooling (worst single failure), emergency onsite AC power would be provided by the redundant EDG and associated electrical train. Consequently, the proposed TS change does not I
impact plant safety as analyzed in the updated VEGP FSAR.
3.0 EXIGENT CIRCUMSTANCES
The Commission's regulations,10 CFR 50.91, contain provisions for issuance of amendments when the usual 30-day public notice period cannot be met. One type of special exception is an exigency. An exigency is a case where the staff and licensee need to act promptly, but failure to act promptly does not necessarily involve a plant shutdown, derating, or delay in startup. As described below.
the requested TS amenament and associated plant n.odification represent a safety -
enhancement.
On May 23,1990, the licensee entered the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement associated with TS 3.6.1 after the Unit 1 "B" EDG failed the applicable Surveillance Requirements. Troubleshooting and additional EDG testing indicated that the nest likely cause for the failure was the HJWT switches. These switches were i
new and had been recently installed and calibrated per the revised calibration procedure (incorporating the lessons learned from the Wyle Lab tests).
Given j
that the most probable root cause for the EDG failure was the same as the root l
cause (HJWT switches) for the March 20, 1990, loss of all vital AC event, and i
l given the repeated difficulties the licensee has experienced with HJWT trips, the licensee determined that the best resolution was to bypass the HJWT trip for all emergency starts. The licensee promptly notified the NPi of its intentions to install a modification to manually by ass the HJWT trip and the need for an expedited TS change to TS 4.8.1.1.2h(6)p(c).
The licensee then subsequently processed the TS change request and plant nodification in an expeditious n.anner.
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The licensee lett the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement of Limited Cond) tion for
. Operation 3.8.1 on May 25, 1990, cf ter having reinstalled the original HJWT switches into the IB EDG ano successfully performing the required surveillance testing. However, given recent operating experience, particularly the March 20, 1990 event, 3nd the difficulties experienced with HJWT trips, the licensee thought it pruent in terms of enhanced plant safety to request the TS change on an expedited b o is.
The NRC staff concurred with the licensee's assessment and provided a Tempo N ry Waiver of Compliance on May 25, 1990, f rom SR 4.8.1.1.2h (6)(c)untilsuchtimethataTSamendmentcouldbeprocessed.
The Comission notifieo the public by publishing a notice in the Federal Register on June 22, 1990 (55 FR 25756). The notice provideo an Tpportunity for hearing and allowed 15 days for public comments on a proposed determi-nation of no significant hazards consideration.
There were no public comments in response to the notice published in the Federal Register.
4.0 FINAL NO $1GNIFICANT HAZARDS CONSIDERATION DETERMINATION The amendment request would revise the existing TS Surveillance Requirement 4.8.1.1.2h(6)(c) to acd a note that allows the HJWT trip to be bypassed.
Essentially, the proposeo change allows the EDGs to be started on an emergency signal (Safety Injection (SI) signal, Loss of Offsite Power (LOSP) signal, or Emergency Manual Start signal) with the HJWT trip bypasseo.
The Comission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards constoeration if operation of the ficility in accordance with the amendment would not:
1 (1)
Involve a significant increase in the probability or consequences of
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any accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; cr (3)
Involve a significant reduction in a margin o' safety.
The licensee has provided the following analysis regarJing no significant hazards consideration using the Comission's standards.
In order to accomodate the current design, the TSs require verification that L
all automatic diesel generator trips are automatically bypassed upon loss of voltage on the emergency bus concurrent with a Safety Injection Actuation signal,
-except for engine overspeed, generator differential, low lube oil pressure and HJWT.
The proposed TS change will not, that the jacket water temperature trip may be bypassed. The HJWT trip is des iner' to protect the diesel generator from a loss of engine cooling.
For suc" u.svent, the safety functions would be provided by the diesel f or the other train.
During an accident, the advantage of the automatic trip is small relative to the increased reliability achieved by reducing the possibility of a spurious trip.
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This change will not increase the probability of an accident previously evaluated because it does not affect any of the design basis events that have been previously evaluated in the FSAR.
The analyses of accident consequences i
do not take credit for the ability to restart a diesel following a diesel generator trip.
Therefore, this change will not affect the previously i
evaluated consequences.
1 The revision to the TSs will net create the possibility of a new or different kind of accident from any accident previously cvaluated.
No new modes of operation are being imposed on the plant and the diesel generators will continue to perform their function as designed.
The revision will not result in a significant reduction in the margin of safety previded for events involving a loss of electrical power.
The proposed revision will allow the implementation of a modification which is intended to improve the te11 ability of the diesel generators by mintuizing the possibility of spurious trips.
Based on the preceding analysis, the licensee determined that the proposed i
change to the TSs would not involve a significant increase in the probability or consequences of an accident previously evaluated, create the possibility of a new or different kind of accident from any previously evaluated or involve a significant reduction in a margin of safety.
The NRC staff has reviewed the licensee's no significant hazaros consideration determination and agrees with the licensee's analysis. Accordingly, the staff finds that the requested anendments do not involve a significant hazards consideration.
5.0 STATE CONSULTATION
in accoraance with the Commission's regulations, the State of Georgia was contacted on May 25, 1990. The state representative had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
'These anendments involve a change to a TS Surveillance Requirement. The staff has determined that the anendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that ney be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure.
The NRC staff has made a final determination that the amendments involve no significant hazards consideration.
Accordingly, the anendnents reet the eligibility criteria for categorical exclusionsetforthin10CFR51.22(c)(9).
Pursuantto10CFR51.22(b),no
. environmental impact statement or environmental assessnent need be prepared in connection with the issuance of these amendments.
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7.0 CONCLUSION
We have concluced, based on the considt. rations aiscussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Comission's regul6tions, and the issuance of these anendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
T. Reed, PDII-3/DRP-I/II S. Saba, SELD/ DST Date: July 10, 1990
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