ML20126E983

Page 10 to Insp Rept 50-263/72-06,inadvertently Omitted from Original Submittal

ML20126E983
Person / Time
Site:	Monticello
Issue date:	11/14/1972
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20024G193	List: IR 05000263/1972006 ML20126E983
References
50-263-72-06, 50-263-72-6, NUDOCS 9212300068
Download: ML20126E983 (1)

See also: IR 05000263/1972006

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differential pressure variations which resulted in a reactor scram.

Following a safety evaluation, the modification was approved by the

Operations Committee in June 1971, with the reconsnendation that

periodic response time checks be made to ensure against plugging

of the snubbers. Operational checks were performed following

installation by the application of a differential pressure to the

sensing lines, with switch response times observed to be less than

one second (to switch set point equivalent to 144 percent of the

full power differential pressure). At the request of the Safety

Audit Counnittee, a procedure for the measurement of response time

was also developed. Performance of this procedure in the workshop

with a spare differential pressure switch and associated snubbers

yielded a response with a time constant of 1.28 seconds as compared

to an allowed time constant of 2.5 seconds (corresponds to a trip

response time of 0.4 seconds, as assumed by the FSAR).

13. Failure of Hain_ Steam Line j rain Valves to Close

A licensee reportM / discussed the failure of a main steam line ,

drain valve to close on July 28, 1972. Discussions with plant

staff personnel indicated the event to have been as described in

the subject report. As stated in the report, a followup inspec-

tion revealed 12 contactors to have loose screws. Licensee

personnel concluded that the screws had apparently not been

sufficiently tightened during initial manufacture. All loose

screws were tightened as necessary, which should prevent recurrence,

since lockwashers are provided.

14. MSIV Reset Switches

During a previous inspection 3.2,/ the licensee indicated an intention

to install a second MSIV reset switch during an outage in May 1972,

such that one switch would reset the inboard and one switch would

reset the outboard MSIV's. The inspector verified by observation

of the control panel that the intended installation had been completed.

15. _ Fuel Pool Siphoning

The potential for inadvertent siphoning of the fuel pool was discussed

with a plant staff representative during the inspection and a subse-

quent telephone conversation. Discussion with the licensee representa-

tive and review of a piping diagram of the fuel pool system indicated

11/ Letter, NSP to Directorate of Licensing, dated 8/28/72

12] RO Inspection Report No. 050-263/72-03

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