ML19317F916
| ML19317F916 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/20/1976 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19317F917 | List: |
| References | |
| 760830, NUDOCS 8002210637 | |
| Download: ML19317F916 (2) | |
Text
,
7
.EliBJD (1, SACRAMENTO MUNICIPAL UTILITY DISTRICT C2 1708 59th S
\\g August 30, 1976 f.
Mr. R..H. Engelken
?
' Director of Regulatory Operations
. E!
NRC Operations Office, Region V 1990 N. California Boulevard Walnut Creek Plaza, Suite 202 Walnut Creek,' California 94596 5
Re:
Operating License DPR-54 e'
Docket No. 50-312 Reportable Occurrence 76-10 L
Dear Mr. Engelken:
g e
av In accordance with Technical Specifications for Rancho Seco ' Nuclear -
Generating Station, Section 6.9.1, and Regulatory Guide 1.16, Revision 4, Section C.2.b.2, the Sacramento. Municipal Utility District is hereby reporting thel following Reportable Occurtence as RO 76-10.
.j b.
J l
(y~
While performing a special test of the diesel generator air start system capacity'on; August 6, 1976, Diesel Generator "A" failed to start once in a series of starts. The system was in a testing mode (other diesel generator available) with the DC air start system isolated so the starting capacity of the AC system could be checked.
Af ter four success-ful starts, one failure to start occurred, followed by two more successful C,
starts. During the failure it was observed that the lower pinion engaged in the ring gear on the start and air was pulsing through the solenoid valve, but no air was flowing to the air start motors.
Since both upper and lower pinions must be engaged in order for the air start motors to rotate, the failure to crank could be caused either by the upper pinion not engaging or the main air control' valve not opening.
An investigation revealed no apparent defective parts in the air start system. The most likely cause of the failure was that the upper pinion may.have been prevented frer' engaging if the pinion teeth were exactly. aligned (flat to flat) with the ring gear teeth. This interference could have' prevented the pinion from engaging, which would interrupt the E;
air flow path to open the main air-control valve.
-The special test had isolated'one of the two air start systems on the diesel generator. The single air start system has a finite probability of
. failure due to having perfectly aligned (flat to flat) pinion and ring gear
.a teeth ~. Normally,'both air start systems would be in service. One of the j
.A two systems would engage and start the ring gear moving which would then
,/
\\~
permit the second system to properly engage independent of the alignment.
(,)
- With two air start systems in service. the probability of two failures -
e (both ~ systems aligned flat to flat) is acceptably reduced.
8 o os sie f3'?
M H
~
COPY SENT REGIO N
g A A ^ )- E L E C T R I C j S Y S T E M SfRVlNG MOPE T H A N' 600,000 IN I H i~ HiAPI-OF f A i ' l O k' 4 3 A -
. c Mr..R.
H.' Engelken' August 30, 1976 We are working with the diesel generator vendor to totally climinate this problem; however, until a solution is reached, and to maintain the j!
. probabilities of recurrence at a minimum icvel, the diesel generators will
- s be declared out of service whenever one of the air start systems is not operational.
'The diesel generator is a Bruce, G.M. Diesel, Type G886B, rated at
.2750 KW.
t,
~ Diesel Generator "B" was proven operable during the time Generator "A"
- was out of service for repairs. There have been no previous failures at Rancho Seco of this type and the failure did not produce any transient.
/,
Respectfully submitted, 9
d,k O
- J J. J. Mattimoe Assistant General Manager and Chief = Engineer 4
,i'
'th 4
/
.JJM:RWCisal ~
Attachment cs: MIPC (3) '
T IE (30)
^
j.
~
a b'
l
- r
,,w
-tv,*
e 4
4 r