ML19321B105
| ML19321B105 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/04/1980 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| IEB-80-12, NUDOCS 8007250676 | |
| Download: ML19321B105 (2) | |
Text
r
[tV e,
5 SWlUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, Box 15830, Sacramento, California 95813; (916) 452 3211 June 4, 1980
,,p
.I@%
3 v
[.
,2 o
j u.1 t
/
Mr. R. 11. Engelken, Director q
ri
,[])
Region V Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission b
1990 North California Boulevard q
Walnut Creek Plaza, Suite 202 Walnut Creek, CA 94596 Re: Operating License DPR-54 Docket No. 50-312 IE Bulletin 80-12
Dear Mr. Engelken:
In response to your letter of May 9, 1980, which transmitted the subject IE Bulletin, the Sacramento Municipal Utility District is hereby submitting the required reaponse.
As a result of IF Bulletin 80-12 (Loss of Decay lleat Removal System at Davis-Besse), an operational assessment was performed on that incident.
Two distinct differences between the Davis-Besse and Rancho Seco DilR/ECCS systems preclude the probability of a similar occurrence at Rancho Seco.
These differences are:
a.
At Rancho Seco, the DilR system suction valves from the RCS (IIV-20001 end 20002) are not automatically closed for containment isolatien on an ECCS signal.
b.
At Rancho Seco, the Reactor Building Emergency Sump isolation valves are not autonatically opened on an ECCS signal.
Ilowever, minor interruptions of decay heat flow can occur at Rancho Seco.
The most probable caus.: would be the tripping or loss of a 120V vital power inverter.
This would result in the RCS pressure transmitters (PT-21092 and 21099) indicating a high RCS pressure and causing the interlocked DHR suction valve (s) (llV-2000' and 20002) to close. A second interlock between the valve (s) and the purp(s) would then trip the operating DilR pump (s).
In the event of such an inefi_..L, D;L ilow can be reestablished by either restorinh 120V.'tal power or dispatching an operator to manually open the DilR suction valve.
Such an event would not allow air to enter the system and therefore, time-consuming venting of the system prior to reestablishing flow would not be necessary.
During the recent refueling outage a situation arose where the DlIR system redundancy was degraded. This situation was initiated by mechanical
)
failure of the "A" DHP punp seal.
This was reported to your office via LER 80-5.
80 07250676 AN ELECIPIC S Y S T E *,f SERV'"G
't 0 R E THAN ' J 0,0 0 0 IN THE ff L A R T OF C A li f 0 P N I A
% DE
o Mr. R. H.
Engelken Page 2 June 4, 1980 Recognizing the aspects of degraded redundancy, an analysis of plant procedures for diversity of DHR capability and adequacy of responding to DHR-loss events ensued.
This resulted in a special order to all operating pc sonnel (SO l-80 dated January 28, 1980), giving specific instructions on providing alternate core cooling in the event of a loss of both DHR systems. These detailed instructions were later incorporated into Emergency Procedure D.16, Loss of Decay Heat Removal Systen, on March 17, 1980.
At the present time, both administrative controls and safeguards against DHR degradation at Rancho Seco are deemed satisfactory. A possible future change to alleviate or minimize the possibility of DHR f'ev interruption on loss of 120V vital power is presently being studied. Whether this additional safeguard is implemented will depend upon the review and recommendations of the Management Safety Review Committee.
Respectfully submitted, L.{ - $
' J.7J. Mattimoe Assistant General Manager and Chief Engineer JJM:HH: jim Sworn to and subscribed before me rd
................................e*
6 OfflCIAL SEAL this 8 day of June, 1980.
.7 -7 MM PATRICIA K. GEISLER f,35)
NOTARY PU8UC CAUFORNIA
@\\y.gg y
eaiNcient or Fict is sAcwerNro couNrv My commisson bpres racvember 22,1983
- /& ' '
ftMlk _/
/-
e..................a............e Notary Public '