ML19317G948
| ML19317G948 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/20/1978 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004020606 | |
| Download: ML19317G948 (3) | |
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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 s street, Box 15830, sacramento, California 95813; (916) 452-3211 July 20,1978 Director of Nuclear Reactor Regulation Attention:
Mr. Robert W. Reid, Chief gg Operating Reactors, Branch 4 U. S. Nuclear Regulatory Commission
- 7 [.24 [7Y Washington, D. C.
20555 I'[,,,,
Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit No. 1 V
Dear Mr. Reid:
On July 18, 1978 the Sacramento Municipal Utility District
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requested authorization for the operation of Rancho Seco Nuclear Generating Station, Unit No.1 at 100% full power.
This request was based on a Babcock
& Wilcox Company analysis of a small break loss of coolant accident and our commitment to provide the proper operator action following such an accident to assure adequate high pressure injection (HPI) flow to the reactor core.
As you requested, we are proposing the following plant modifica-tions to eliminate the need for operator action:
1.
The valves in the crosstie line connecting the two HPI loops will remain open whenever the HPI system is in service.
2.
The two Loop A injection valves (one in each leg) will be powered from the 125 volt DC, Class 1, C battery.
3.
The two Loop B injection valves (ort. in each leg) will be powered from the 125 volt DC, Class 1, D battery.
4.
The makeup isolation valve will be powered from the 125 vol t DC, Class 1, C battery.
5.
The four injection valves will receive a signal to open from both Channels A and B of the safety features activation system.
The makeup isolation vaive presently receives a signal from both Channels A and B.
This modification is possible because Rancho Seco Unit No.1 incorporates four independent Class 1 battery systems in its design.
Battery A supplies control power to the A safety features system, including the A HPI pump.
The B battery supplies control power to the B safety features system, including the B HPI pump.
The proposed DC power operation of the injection 4Bse6 M foo W 0b ' 4p AN ELECTRIC S YS TE M S E RVIN G MORE THAN 600,000 IN THE HEART OF C ALIFo R N I A
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" ' Mr~. R. W. Reid 2-July 20,1978 and makeup isolation valves would result in the following conditions following a single failure, assuming the coincident loss of offsite AC power:
Single Failure Resultina Condition A.
Failure of the A safety HPI Pump A would fail to operate, features s AC power (y= tem backup however, Pump B would provide Diesel A) adequ&te flow into all four HPI legs.
B.
Failure of the B safety HPI Pump B would fail to operate, features s ACpower(ystembackup however, HPI Pump A would provide Diesel B) adequate flow into all four HPI legs.
C.
Failure of Battery A HPI Pump A would fail to operate, however, HPI Pump B would provide adequate flow into all four HPI legs.
D.
Failure of Battery B HPI Pump B would fail to operate, however, HPI Pump A would provide adequate injection into all four HPI legs.
E.
Failure of Battery C The two A injection valves would fail to open and the makeup isolation valve would fail to close.
- However, both HPI pumps would provide adequate flow into the two B injection legs and the one A injection leg, which is fed by the makeup line.
F.
Failure of Battery D The two B injection valves would fail to open, however, both HPI pumps will provide adequate injection flow to the two A injection legs.
If the break is in the leg, which is fed by the injection leg which is in turn fed by the makeup line, adequate flow to the core would not be starved by excess flow to the break since the makeup valve is powered from the same battery which powers the injection valve in that leg so it will close if the injection valve opens.
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Mr. R. W. Reid July 20,1978 Single Eilure Resulting Condition G.
Failure of the A or B The A or B HPI pump will fail to safety features activation operate, however, the other pump signal will provide adequate flow through all four injection legs, since each injection valve will receive a signal to open from the other activation signal.
H.
Any other failure of a Results as described in Table 6.1-5 single component of the Rancho Seco Unit No.1 FSAR.
An analysis has been performed to verify adequate battery capacity to power the five valves. This analysis assumed that the DC starter used for operating the motor operated valves are full voltage reversing starters which will be capable of operating the valve within 10 seconds and at the same time have the battery capable of supplying the existing load.
This modification to the high pressure injection system has been reviewed by the District and we feel itwill provide the required protection.
We do consider it to be an unreviewed safety question and in accordance with 10 CFR 50.59, requires your approval before its implementation.
Sincerely yours, h.c-bh J. J. Mattimoe Assistant General Manager and Chief Engineer l
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