ML20062K190
| ML20062K190 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 12/13/1993 |
| From: | Donnelly P CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9312210166 | |
| Download: ML20062K190 (2) | |
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Consumers Patrick M Donnelly 1%nt Manager MICHIGAN'S PROGRESS Big flock Point Nuclear Plant.10269 US-31 North, Charlooen. MI 49720 December 13, 1993 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - MAIN STEAM ISOLATION VALVE (MSIV; M0-7050) UPDATE TO ADDRESS NUCLEAR REGULATORY COMMISSION ASSESSMENT PERFORMED JUNE 29, 1993.
On November 15, 1993, Consumers Power Company submitted a response to update the Commission with regards to a NRC assessment of Big Rock Point's emergency l
condenser and main steam isolation valves. The update addressed the emergency condenser inlet isolation valves, MO-7052 and M0-7062; however a request was made to address the main steam isolation valve within an additional submittal.
The purpose of this letter is to advise the NRC to the current status of the actions taken with regards to the ' main steam isolation valve. This is the last of the actions requested by NRR/EMED (Office of Nuclear Reactor Regulation / Mechanical Engineering Branch) to provide an acceptable level of-confidence that the MSIV could close against high differential pressure; and reduce the risk associated with a small steam-line break or other plant transients.
MAIN STEAM ISOLATION VALVE (MSIV) M0-7050 An indepth review of the original Big Rock Point staff proposal to revise Standard Operating Procedure (50P) 10, Containment Vessel, to caution against-premature attempts to close the MSIV prior to differential being within the capability of the valve operator, has been performed. All current station procedures, including emergency operating procedures, were reviewed to ensure that the operator was not directed to close the MSIV against conditions outside of the design basis. The revision will add-the following statement to the Precautions and Limitations section of S0P 10:
"The MSIV operator thrust output at torque switch trip is sufficient to close the valve under design basis conditions. However, any attempts to close the valve at differential pressure greater than 500 lbs may not be'within the
-capability of the MSIV.
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.MSIV. UPDATE December 13, 1993 If the MSIV fails to close, it may be due to premature tripping of the torque switch. It may be necessary to give a momentary open signal to reset the torque switch; then resignal the valve in the closed direction."
By this letter, Consumers Power Company considers all actions with regards to this issue complete.
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/ b '; I;nul Patrick M Donnelly O
Plant Manager CC: Administrator, Region III, USNRC NRC Resident Inspector - Big Rock Point j