ML19317F929
| ML19317F929 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/30/1976 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| Shared Package | |
| ML19317F930 | List: |
| References | |
| NUDOCS 8002210645 | |
| Download: ML19317F929 (2) | |
Text
.____..
~
,. ~
-m, A( j)(
e
.,u-
.u SACRAMENTO MUNICIPAL UTILITY O! STRICT C) 6201 S Street. Box 15830,' Sacramento, California 95813; (916) 452-3211 April 30, 1976 IE FILE COPY Mr. R._H. Engelken i
Director of Regulatory Operations NRC Operations Office, Region V V
1990 N. California Boulevard
<f
(
Walnut Creek Plaza, Suite 202 C
Walnot Creek, California 94596
- , z
- <N
~
- m..
H Q. x,e,,
~:-
RE: Operating License DPR-54 C
NN j.
Docket No. 50-312 s
~
Reportable Occurrence 76-6
_, '.; f
.y
Dear Mr. Engelken:
~
In accordance with Technical Specificat' ions for Rancho Seco Nuclear Generating Station, Section 6.9.1, and Regulatory Guide 1.16, Revision 4,
~~
Section C.2._b.3, the Sacramento Municipal Utility District is hereby
)
reporting the following Reportable Occurrence as RO 76-6.
j
\\
Following a review of surveillance records to assa.re compliance with Technical Specifications Table 4.1-1, it was repm.ed on April 9, 1976, that -on ten occasions a heat balance calibration was not performed as required.
Item No. 3 of Table 4.1-1 requires that a heat balance calibration be performed on a power range amplifier (Reactor Protection y" System) whenever the difference between neutron power indicated on the nuclear instrumentation and the core thermal power as calculated by a
~
heat balance exceeds two percent. Nine of the instances involved the indicated neutron power being greater than the core thermal power, a conservative situation which would result in an overpower trip prior to reaching the Technical Specifications setpoint.
Core thermal power exceeded neutron power on one occasion for two of the RPS channels.
The remaining two channels were within the acceptable range, assuring adequate protection in the two out of four logic of the ' Reactor Protection System.
There exists a possibility that several of these instances of 2
apparent disagreement in power indication were the result of the method f
by which data was used to make the comparison.
Specific blocks of data.
can be obtained from the plant computer in the form of computer groups l
identified by number.. Originally, the data for core thermal power and l
indicated neutron pow' could be obtained only by calling two separate l
groups. Due to the c:
utation time involved for each group, up to a period of six minuted the data for the heat balance-calculation may M
have represented a di erent time ' period than the data for indicated l (A Thislpotentialsourceofinaccuracywhichcouldnecessitate j'
J.
neutron power.
,-V
.an unnecessary calibration has been eliminated by combining all of the
- g 8002210EVS m-COPY SENT CGION
- t. ).
EtECTRIC-SYSTEu sERytNG f.t o p t 19 4 n. 6 0 0. 0 c 0 IN THI,i ! t. E r ;) t
.3 s
1
l fg.
\\_,)
Mr..R. H. Engelken April 30, 1976 information required for the comparison on one group, which gathers all necessary data at the same time.
The surveillance procedure has been revised to request that this group be called when using the
. l computer data.
Six surveillance checks performed between February 17 and 23,
[I 1975, were at power levels below 15%. An accurate heat balance cannot be obtained from the secondary system and data from the primary system is used. Because of the assumptions used in heat losses and gains in the primary system, the accuracy of the measurement at low power levels below
_~
15% is difficult to obtain. The surveillance procedures during this time
~
period were accepted by the Engineer due to the associated xenon transient and difficulty of obtaining an accurate heat balance. On February 25 the reactor power was increased to 42% and on February 26 the reactor power was increased to 55%. During both these days the system was in a xenon
~
transient and the Engineer stated the conditions on the procedure. The.
/
reactor power was increased to 92% on February 28, 1976, and the same reasra for. acceptance was stated on the procedure that day. The calibrations we'r'e performed as required during full power operation until March 13, 1976,
.I when reactor power was reduced to 50%. Again the system was in a xenon transient and the Engineer stated this fact in the procedure for not requiring
)
a Yecalibration.
2 (O)
\\s /
The requirements of Table 4.1-1 have been clarified, the surveillance procedure has been modified to require coincident data collection, and the,
surveillance records will receive closer review. These measures will assure calibration of the power range amplifiers as required.
fs The failure to calibrate the power range amplifiers did not compromis'e the safety of the plant.
In the only instsnee where the instrumentation <
error was in a nonconservative direction, sufficient accurate indication was available for the Reactor Protective System to operate as required. There was no transient associated with this occurrence.
Respectfully,
-i-J. Mattimoc Assistant General Manager
^
and Chief Engineer l-3.
.G, i
- 5
/
%f r
JJM:RWC: sal-(
' Attach.
es: - MIPC(3)'.
_IE(30)
?
~ Q1 e
-