ML20056B630
| ML20056B630 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 12/03/1971 |
| From: | Wachter L NORTHERN STATES POWER CO. |
| To: | Grier B US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20056B627 | List: |
| References | |
| NUDOCS 9102070633 | |
| Download: ML20056B630 (3) | |
Text
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t NORTHERN STATES POWER COMPANY
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December 3, 1971 l
Mr. Boyce H. Grier, Regional Director Region III Compliance Office United States Atomic Energy Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Grier:
I MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 i
In your letter of November 16, 1971, you identified certain items which appeared j
to be in noncompliance with AEC requirements and which raised questions concerning.
i the safety of operations. A copy of these items is attached for reference. You requested that we provide, in writing, within 20 days, our comments concerning the items, any steps that have been or will be taken to correct them, any steps that have been or will be taken to prevent a recurrence, and the date all the corrective f
actions or preventive measures were or will be completed. The following information
- Di is hereby submitted in response to your request.
Item A:
The Group I (Main Steam, Main Steam Drain and Recirculation Sample Valves) isolation reset switch is identical to and located adjacent to the Group III (reactor cleanup l
isolation valves) isolation reset switch. Following scrams from high power, normal void collapse in the core results in a low water level signal which initiates a Group III isolation. Therefore, Group III isolation must be, and is, routinely reset following every scram from high power. Because of repeated Group III isolation due to high temperature at the inlet to the cleanup demineralizers, it is co==on to have to reset more than once.
It is possible that the operator accidentally reset Group I while attempting to reset Group III. The Operations Committee concluded that this must have occurred on September 5,1971, a conclusion reached only af ter inspections and tests had eliminated every other known possibility.
The following steps were taken to prevent a recurrence:
1.
The procedural errors were discussed with the individuals involved.
2.
A memo was distributed to the plant operators. This memo summarized the Operations Committee conclusion and re-emphasized that the isolation mu'st not be reset until it can be definitely determined that system isolation
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is not required.
(This memo was posted on the control room bulletin board for a period of about four weeks and has been initialed by all shift
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supervisors and control room operators.)
9102070633 711216 CF ADDCK 05000263 CF DEC 6 - 1331
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Mr. Boyce H. Grier 2
December 3, 1971 i
3.
A plastic cover has been placed over the isolation reset switch to prevent inadvertent operation.
The above steps were all completed by September 10, 1971.
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1.
On November 17, 1971, additional operating procedures for the review and documentation of the investigation of operating disturbances were issued.
The procedures require the completion of a checklist which is designed ~to assure that a thorough review is performed. Equipment malfunctions, pro-i cedure inadequacies, and operating errors identified by the review must
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be listed and a separate followup record form must be completed for every such item.
Prior to a plant restart, the checklist and records of corrective actions taken must be reviewed and approved by'the Plant Results Engineer and the Operations Supervisor. A copy of the checklist, the record form, Land the instructions for their use, was given to Mr. Seyfrit of your office on his most recent visit.
l 2.
The NSP System Operation Department was advised on November 3,1971, that 'in i
the event of a Monticello plant trip, the assumption be made that it will be j
at least twenty-four hours before the unit will return to service and to i
arrange for replacement power on that basis. This was done to minimize pressures for an early plant restart and to assure adequate time for a thorough investigation.
Yours very truly, l
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L. J hachter, Vice President i
Power Production and System Operation LJW/vm cc R. O. Duncanson C. E. Larson s
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.D ENCLOSURE
s Docket No. 50-263 A.
Certain activities under your license appear to be in nonco=pliance with the requirements of License No. DPR-22, as indicated below:
Appendix A to Provisional Operating License DPR-22, Section 6.2, Plant Operating Procedure, Paragraph A states in part that, " plant operations will be conducted in accordance with written procedures
-contained in the Operations Manual.""
e Contrary to the above, operations were not conducted in accordance with your written procedures when, in conjunction with recovery from the reactor scram, isolation and emergency core cooling system initiation which occurred on September 5,1971, an operator reset the main steam isolation valves, causing them to reopen before an analysis of system conditions had verified that system isolation was not required.
B.
Certain activities under your license appear to raise questions concerning the safety of operations as identified below:
-'k' On September 5, 1971, the reactor was restarted following an immediate investigation of an unplanned reactor shutdown, before a thorough evaluation of all aspects of the occurrence (reactor scram, isolation and emergency core cooling system initiation) had been ' conducted. The anomalous performance of the main steam isolation valves (MSIV) was not identified until after subsequent review of the occurrence, which-resulted in the reactor being shut down for a further investigation of the unexplained MSIV behavior.
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