ML19249A255

Submits Interim Rept Re Potentially Unsafe Situation If Reactor Coolant Pumps Are Tripped After High Sys Void Fractions Develop in Loop.Analyses Show Safe Condition If Pumps Are Tripped Promptly in Transient

ML19249A255
Person / Time
Site:	Midland
Issue date:	08/15/1979
From:	Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
HOWE-221-79, NUDOCS 7908210477
Download: ML19249A255 (1)

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? Q Q ' P0rl8f g Stephen H. Howell

= Senior Vice President General Offices: 1945 West Parnall Road, Jackson, Michigan 49201 . (517) 788-0453 August 15, 1979 -

Eeve-221-79 -

Mr J G Keppler, Regional Director Office of Inspection and Enforcement US Nuclear Regulator;, Com:nission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 MIDLAND NUCLEAR PIANT -

UNIT NO 1, DOCKI7f NO 50-329 UNIT NO 2, DOCKET NO 50-330

• SMALL BREAK / REACTOR COOLAITI PIEP OPERATION INTERACTION In accordance with the requirements of 10 CFR 50 55(e), this letter constitutes an interim report concerning a potentially unsafe situation if the reactor coolant pumps are tripped after high system void fractions develop in the loop.

Specifically, for the lov probability events gnvohing a range of en11 reactor coolant system breaks (approximately 0.025 ft to 0.2 ft ), analyses show that a high void fraction vill develop in the primary system during the course of the accident. 10 C7R 50 Appendix K criteria may be exceeded if reactor coolant pu:nps are tripped after creation of this high void condition. ELW, Midland's NSSS Supplier, has been workin6 closely with the NRC staff (Dr Rosztozy) concerning this analysis.

B&W reports that analyses have been perfomed which confirm a safe situation if tl e reactor coolant pems are tripped promptly in the transient prior to establishing a high void fraction. E&W made a reco=nendation to the 1TTFA opercting plants that "Upon receipt of an ESFAS actuation caused by low RC pressure, ell operating RC pumps must be tripped i-adiately." CPCo is con-sidering an automatic /cafety grade trip system to accomplish the recommended action for the Midland Plant.

Another report, either interim or final,, vill be sent ca er before October 19, 1979

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W CC: Direr. tor of Office of Inspection and Enforcement Att: Mr Victor Stello, USNRC (15)

Director of Office of Mana6ement g 7(orNN Information and Program Control, U3NRC (1) 2 908 210 7n S

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