ML19309A304

Requests Addl Info within 30 Days Re Proposed Measures to Prevent Reactor Vessel Overpressurization

ML19309A304
Person / Time
Site:	Rancho Seco
Issue date:	12/10/1976
From:	Reid R Office of Nuclear Reactor Regulation
To:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
References
TAC-6710, NUDOCS 8003270731
Download: ML19309A304 (5)

Text

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' DIS QIBUTION:

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December 10, 1976 NRC PDR ACRS (16)

Local RR l'DR Gray File ORB #4 Rdg.

Dock *et No.:

50-312-V. Stello K. R. Goller Attina.ntBEkBx T. J. Carter Attorney, OELD Sacramento Municipal Utility OIAE (3)

District R. Reid ATTH: Mr. J. J. Mattimoe V. Rooney Assistant General Manager R. Ingram and Chief Engineer D. Eisenhut 6201 S Street T. B. Abernathy a-P. O. Box 15830

.J.'R. Buchanan Sacramento, California 95813 f

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Gentlemen:

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At the November 5,1976, meeting between Babcock & Wilcox (B&W)-

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licensees and the staff, we indicated that we would advise each

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ti censee of the additional information needed to complete our eval-

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uation of the measures he had proposed to prevent reactor vessel overpressurization.. This information has_now been identified and

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t is listed in the enclosure.

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In order that we.may c.omplete 'our review in a timely manner, you

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, are req' vested to' submit the information' listed' in the' enclosure 4

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.'within 30 days Lof receipt of this letter.

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Sincerely,

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L, Robert W. Reid, Chief Operating Reactors Branch f4 I

1 Division of Operating Reactors 2.

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Enclosure:

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. Request for Additional

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2 Information

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Sacramento Municipal Utility District 3

cc: David S. Kaplan, Secretarf and

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e General Counsel 6201 S Street Post Office Box 15830 i

Sacramento, California 95813 Business and Municipal Department Sacramento City-County Library 828 I Street Sacramento, California 95814 6

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In light of design criteria discussed on November 5,1976, it appears'that further analysis may be necessary to verify that your overpressurization system design is' adequate to meet Appendix G limits assuming an additional single failure.

Please provide a schedule for submittal of further system analyses, or justify why further analyses will not be necessary.

2.

The criteria discussed.at the November 5 meeting are listed below:

1)

Credit for operator action

2) Sing'le failure criteria

3) Testability v

4) Seismic design and IEEE 279 criteria i

Provideinformationregardinghowjouintendtomeettheabove i

design criteria. Where deviations from the criteria are contem-j plated, please provide a detailed justification including the j

technical basis for not meeting the criteria and, when significant l

the impact on the schedule for implementation.

Describe all redundant and diverse systems which are available to provide overpressure protection.

3.-

Provide schematic ~ piping'and instrumentation diagrams 'of.all systems which are utilized during plant shutdown and startup operations, indicate primary and alternate flow paths, fluid and j

heat sources, pressure and flow controllers, RCS pressure protection.

systems, and ECCS and make up systems.

4.

Provide a failure modes and effects analysis of the overpressure' protection system for startup, shutdown, and testing operations which defines the limiting combination of initiating event and additional single failure or operator error subsequent to initiation of the overpressure transient.

5.

Indicate for your low temperature overpressure protection system '

how the system has been designed to handle common failure modes such as those resulting from loss of offsite power and seismic events. Describe the failure mode of the air operated makeup flow i

control valve and the letdown flow control valve upon loss of air os a r su p y L'. _

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Discuss the basis for determining the most limiting initial

. conditions for analysis of the overpressure transient.

Items-that must be considered include ~but should not be limited to; RCS pressure, valve opening time, steam generator temperature

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difference, reactor coolant pump seal pressures, pressurizer level, makeup tank level, accumulator pressure, relief valve water.

relief capacity, and pump heads and flows.

7.

Please provide a transient analysis of the reactor coolant system response to inadvertent actuation of a single train of high pressure injection pumps. Describe what administrative controls and procedures are used during startup and shutdown, and during component and/or system testing to justify the assumption that inadvertent injection by more than'one high pressure train is'not credible.

Provide a similar discussion and analysis of a core flod tank discharge.

For both situations indicate the basis for i

identifying the limiting single failure or common failure mode.

8.

Does your plant have relief capacity installed in the decay heat removal system that could provide additional protection in the j

event of an overpressure transient? What is the water relief capacity of the valve? Is the decay heat removal system automa-tically isolated on RCS high pressure.? What are the pressure i

setpoints for the DHR relief valve opening and its automatic isolation?

I 9.

During the November 5th meeting, the possibility of limiting the volume of water in the RCS inake up tank was discussed.

It was stated that this could preclude filling the pressurizer if the make up control valve should fail full open.

Is this procedure a viable option at your facility? Is water level in the Make Up Tank generally controlled automatically? Specify your assumptions for initial pressurizer level, make up tank water volume, and oth'er design considerations which would result in limiting RCS pressure to within Appendix G limits.

10.

Describe what instrumentation and alarms are available to the operator to aid in detection and temination of an overpressure transient.

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11. What precautions are taken during startup, shutdown and testing to verify that critical procedural steps are performed to reduce the likelihood of inadvertently initiating an overpressure transient and minimizing the impact of the transient on the RCS.

Would steps such as lock out of pumps and accumulators and reducing the water level in the pressurizer and make up tank be accomplished by double check off and sign off procedures to insure against error? What procedures normally are followed for altering the status of pumps or valves under administrative restriction?

12.

If power is removed from valves as part of administrative controls used for overpressure protection, what status lights and indicators are available to verify their proper alignment? When adminis-trative controls call for removing power from a valve or a pump, is this accomplished from the control room or from a motor control center?

13.

Describe any testing procedure proposed to insure operation of overpressure protection devices. At what times would these tests be performed?

14. The problem of pressurizer relief valve maintenance was also discussed at the November'Sth meeting. The relief valve is nor-mally isolated and removed during shutdown conditions if main-tenance is required. This would reduce the level of protection available to mitigate the consequer.ces of a pressure transient.

Please discuss what measures will be taken at your plant to provide overpressure protection when the relief valve is removed frt:o service and indicate how the criteria enumerated at the November 5th meeting will be met.

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