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Forwards Insp Rept 50-312/74-07 on 740814,19,20,0903-05 & 11-13.Corrective Measures Taken in Response to AO 74-3 Re RCS Overpressure During Heatup Considered Adequate
	ML19309A412
Person / Time
Site:	Rancho Seco
Issue date:	09/30/1974
From:	Spencer G; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Thornburg H; US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML19309A413	List: IR 05000312/1974007; ML19309A412; ML19309A416;
References
	NUDOCS 8003270858
	Download: ML19309A412 (4)
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UNITED STATES

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ATOMIC ENERGY COMMISSION

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H. D. Thornburg, Chief, Field Support and Enforcement Branch

Directorate of Regulatory Operations, HQ

SACRAMENTO MUNICIPAL UTILITY DISTRICT (RANCHO SECO)

DOCKET NO. 50-312

The attached report by our field inspector of a visit to the subject

facility on August 14, 19, 20 and September 3-5 and 11-13, 1974 is

forwarded for action.

We consider the corrective measures taken by the licensee to be adequate

in response to the events described in his Abnormal Occurrence Report

No. 74-3 (reactor coolant system overpressure during heatup) . We also

expect the licensee will fulfill his commitment to change the plant

technical specifications so that pressurizer level instrumentation will

be required to be operational during operation of the reactor, and

intend to maintain close surveillance on this item until the change has

been completed.

T'a1.: cecurrence indicates a possible weakness in tha criteria currently

used in classification systems. In the case in point, the a.c. nower to

non-nuclear control instrumentation at Rancha Seco is classified as a

Class II quality system; thus, redundancy is not required. Although we

recognize that the ability of the safety features to function was not

jeopardized in the situation in question, technical specifications that

permit operation of a nuclear plant without reliable indication of

important paranaters such as pressuriser level and reactor pressure

,

appear to make academic the AEC regulation that requires an AEC licensed

operator to be at the reactor controls at all times during operation of

the unit.

Another aspect of the design / classification problem associated with this

occurrence is that the consequences of the letdown and makeup flow

control valves positioning at the midrange point could aggravate the

transient analyzed for a moderator dilution accident.

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In view of the above, we recomunend that Licensing and Standards evaluate

the current criteria that permit non-nuclear control instrumentation to

be less than Class I.

It appears to us that at least certain non-

nuclear control instrumentation should receive the same considerations

during design that the reactor protection system receives.

We also plan to submit a proposed RO Bulletin on the matter since the

circuit design deficiency may be applicable to other facilities as well

as B&W designed plants.

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G. S. Spencer, Chief

Reactor Construction &

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Ope. rations Branch

Enclosure:

RO Inspection Report

No. 50-312/74-07 (21 copies)

cc w/ enclosure:

RO:HQ (5)

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