ML20002C775
| ML20002C775 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 07/19/1974 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101100844 | |
| Download: ML20002C775 (3) | |
Text
M
[ :m',
i %;.m 1
F 7,w;
.,,lI.
o
~dJ i
CODSumBIS Q :.ULEOI9[ A p0WBi o
i 9, c.
.e,
C0mpBuy fe,
a v - TC.p',r
'Agekeral Offices: 212 West Michegan Avenue. Jackson, Mich6gan 4920t e Area Code 517 78B-0550 July 19, 197h Of//
at V'
4
'/
ccacu
- f. s N
35AEC 0
3 JUL 23 5
.3 Mr. John F. O' Leary, Directo 3 T-Re: Docket 50-155 Directorate of Licensing d
gjA$
License DPR-6 US Atomic Energy Commission cma cm y
Big Rock Point Washington, DC 20545 J
Dear Mr. O' Leary:
By letter dated May 1, 1974, Consumers Power Company sub-mitted additional information concerning the "as-found" control rod withdrawal times of seven (7) of the thirty-two (32) Big Rock Point control rod drives being less than the 23-second withdrawal limit re-quired by the Technical Specifications (AO-3-74). The letter described temporary measures that were being implemented to reduce the probability of exceeding the 23-second withdrawal specification in the hot condition.
Since that time, the Safety Audit and Review Board has performed another review and recommended other temporary corrective action which thaf believe to be more appropriat_e than that stated in the May 1,1974 let.ter.
The May 1,1974 letter stated in part:
"To. reduce the proba-bility of exceeding the 23-second withdrawal specification in the hot condition, the withdrawal rates vill first be set in the cold condition and at the slowest rate possible to maintain proper operation (approx-imately 36 seconds). Following the heat-up to the hot condition, the drives vill then be inserted and the withdrawal rate on each drive checked. Any control rod drive that withdraws faster than 25 seconds vill be adjusted to withdraw slo"er to account for minor hydraulic sys-tem changes. This test vill te conducted each time the reactor is started up from either a cold condition or a hot standby condition un-til either a preposed Technical Specifications change is submitted and approved to r,;4uce the 23-second withdrawal time or a modification of the existing system is performed that enhances its ability to meet the 23-second withdraval time requirement with a less rigorous surveillance and timing prograc."
The hot, staMby sta-t,-up accident is the accident which establishes the 23-second withdrawal limit. The accident, as sies-cribed in the FHSR, assumes an error in which the operator withdraws an off-standard sequence of control rods in a local grouping which maximizes control rod vorth. Then, at that time, the strongest con-trol rod in worth is. continuously withdrawn (due to operator error in positioning the jog-run switch) at the rate of three (3) inches per second (23 seconds total withdrawal time).
b h~'. 4 t/wo ceW
~
c(
Mr. John F. O' Leary, Director 2
Docket 50-155 License DPR-6 Big Rock Point July 19, 1974 As the start-up accident is based on an operator error which causes the continuous withdrawal of the control rod, the Safety Audit and Review Board concluded that if the physical ability to continuously withdraw the control rod is removed, the 23-second withdrawal limit for continuous motion would not be a concern. It is physically impos-sible to move a drive from the fully inserted position to the fully withdrawn position in the jog mode of operation in less than 23 seconds.
Therefore, the Safety and Audit Review Board concluded that if the jog-run switch were disabled, the need for the temporary additional timing surveillance specified in the May 1, 1974 letter would no longer be re-quired. This action is also considered to be a te=porary measure until permanent action as described in the May 1,197h letter ce.n be taken.
The disabling of the switch will be accomplished by lifting and insulating lead 1 on the 1/1T contacts of the control rod posi-tioning Jog-run hS5 switch. This lead will be lifted at all plant operating conditions except when the plant is in the cold shutdown condition. The lead vill be lifted, insulated and tagged in accor-dance with appropriate plant administrative procedures. The lead will be reinstalled in the cold shutdown condition as necessary to allow continuous withdrawal timing and testing of the control rod drives.
This testing is perfor=ed to establish proper jogging operation follow-ing maintenance or to fulfill Technical Specifications testing require-ments at six-month intervals.
Based on the modification described above to temporarily dis-able the jog-run switch in the jog mode during all conditions except the cold shutdown condition, the Big Rock Point Plant Review Coamittee and the Safety Audit and Review Board have concluded that this modifi-cation does not involve an unreviewed safety question nor require a Technical Specifications change.
As described in the May 1, 197h letter, analysis is being performed to justify reduction of the 23-second withdrawal time. This analysis has not yet been completed. When this analysis is completed and if the results are acceptable, a proposed Technical Specifiestions change vill be submitted.
Yours very truly, Y
}k I
RBS/ds Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC
-