ML20003B391

Order for Mod to License DPR-46,designing Automatic Dump Sys to Be Independent of Air Pressure Instrumentation for Manual Scram

ML20003B391
Person / Time
Site:	Cooper
Issue date:	01/09/1981
From:	Eisenhut D Office of Nuclear Reactor Regulation
To:	NEBRASKA PUBLIC POWER DISTRICT
Shared Package
ML20003B392	List: ML20003B391
References
TAC-42227, TAC-47003, TAC-47004, NUDOCS 8102100745
Download: ML20003B391 (6)

Text

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of

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NEBRASKA PUBLIC POWER DISTRICT Docket No. 50-298 (Cooper Nuclear Power Station)

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ORDER FOR MCDIFICATION OF LICENSE I.

The Nebraska Public Power District (licensee) is the holder of Facility Operating License No. DPR-46 which authorizes the operation of the Cooper Nuclear Power Station at stea@ state reactor power levels not in excess of 2381 megawatts thermal (rated power). The facility consist,s of a boiling water reactor locsted at the licensee's site in Nemaha County, Nebraska.

II.

During a routine shutdown of Browns Ferry Unit No. 3 on June 28, 1980, 76 of 185 control rods failed to fully insert in response to a manual scram from approximately 30% power. All rods were subsequently inserted within 15 minutes and no reactor damage or hazard to the public occurred. However, the event did cause an in-depth review of the current BWR Control Rod Drive Systems which indentified design deficier.cles requiring both short and long-term corrective measures. These measures are set fcrth in the Generic Safety Evaluation Report - BWR SCRAM DISCHARGE +. SYSTEM, dated December 1,1980, prepared by the NRC staff.

One of the deficiencies identified was a failure mode of the control air system, which can conceivably cause an inability to scram 8102100 7tE

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7590 02 the control rods. Sustained low pressure in the control air system could result in complete or partial opening of multiple scram outlet valves before opening of the scram inlet valves, causing the Scram Discharge Volume (SDV) to fill rapidly, thus leaving a relatively short time for the operator to take corrective action before scram capabilit/ is lost.

It appears that an even: of this general type (but with no adverse consequences) actually occurred at the Quad Cities Unit 1 reactor on January 3,1977.

IE Bulletin 80-17 (Supplement 3) requires an immediate manual scram when low pressure occurs in the Control Rod Drive (CRD) air system or when other indications occur, such as multiple rod drift alarms or a marked change in the number of convol rods that are at high temperature.

Beginning on December 1,1980, protectic; was also provided by continuous monitoring of the SDV as required by IE Bulletin 80-17 (Supplement 1).

However, since only a short time could be available for the operator to sue:essfully initiate i

a reactor scram, a question remains as to the adequacy of equipment and procedures. This continuous monitoring system and operator response provide j

important protection against water accumulation in the SDV headers under slow fill conditions; however it does not address c:mpletely all the potential loss of air events.

In addition, a human factors evaluation determined that reliance on the operator to successfully carry out a manual scram within a limited time frame may not be assured. Therefore', in the short term in order to provide prompt added protection for credible degraded air conditions in BWR control air supply systems, it is necessary that an automatic system be operable to initiate control rod insertion by rapidly dumping the control air system header if the air pressure decreases below a prescribed value.

Tne NRC staff is developing revised design and safety criteria for a lone term solution to this problem.

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III.

The Generic. Safety Evaluation Report (SER) cf December.1.1980, I

racomended that this automatic '2ir header dump system be installed within two unths. As a result of questions as to whether a reliable system could be installed within two months, the staff ec:,tinued to review this require-ment. We have performed a more detailed risk assessment which has shown a lower probability for the loss of scram capability due to a loss of air than our original estimate. We have also raevaluated the human factors involved in carrying out the requirements of IE Bulletin 80-17 (Supplement 3) which requires a-manual scram of the reactor on alarms related to the loss of air pressure in the air system. These alams provide some added assuranet t..

that the operator can trip the reactor before the scram discharge volume l

t fills.

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As a result of these analyses I have determined that the public health, u.- -

i safety and interest require that the automatic air dump system be in operation 1

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within 90 days of the date of this Order and that operation during this l

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period does not present an undue risk to the public health and safety.

I have further detemined based on staff evaluations of installed air systems, and on staff discussions with industry rephsentatives that l-a 90-day period will aOow adequ._.. time for design, procurement, fabrication, installation, and testing for an automatic air dump system of the type prescribed in this Order.

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As discussed above, although (1) the failure of the control air system is a low probability event, (2) the actions already required provide a significant measure of assurance that such an event will not occur and (3) the criteria for a long term fix are currently being developed, I have determined that the public health and safety require the additional mcasures prescribed by t51s Order and their implementation on this short time s chedule.

However, in view of the intnediacy of the need for this system, the system being mandated by this Order is not being made subject to the requirements of Appendices A and B to 10 CFR Par-50.

IV.

Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, f r.cluding Sections 103 and 1611, and the Commission's rules and regulations in 10 CFR Parts 2 and 50, IT IS ORDERED THAT EFFECTIVE IMMEDIATELY, Facility Operating License No. OPR-46 is hereby amended to add the following provisiens:

(1 )

An automatic system shall be operable to initiate control rod insertion on low pressure 1e the control air header, which meets the following criteria:

l (a) The system shall automatically initiate control rod i'sertion at n

10 psi or greater above scram outlet valve opening pressure; (b) The system shall not degrade the existing safety systems (e.g.,

I reactor protection system);

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(c) The system shall allow for scram reset; (d) The desis shall consider the potential for inadvertent or unnecessary scrams;

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(el Any required p:wer supply should not be suitect to any failure made which could also initiate the degrad,ed-air conditions, unless it can be demonstrated that an automatic scram will oc:ur pro =ptly because of the failure mode of the Power supply; (f) The system is not subject to the requirements of Appendices A and B obl0 CFR 50;

(g) There shall be a documented independen: design review of the system; (h) Before the system is declared operable, a docu:nented pre-operational test of the system will be sue:essfully completed; and (i) The system shall be functionally tested at each Unit shutdown, but need not be tested more than ence each 90 days.

(2) After April 9,1931, the Automatic Dump System as described above shall be operable in all modes other than shutdown and refueling or the unit shall be placed in a cold shutdown condition within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> unless system operability is restored.

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V.

The' If censee or any person whose interests may be affected by, this Order may request a hearing within 20 days of the date of publication of this Order in the Federal Reefster. Any request for a hearing will not stay the effective date of this Order.

Any request for a hearing shall be addressed to the Director, Office of Nuclear Reactor Regulation, U. S.

Nucle'ar Regulatory Com:lission, 'r.:shington, D. C.

20555. A copy of the

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request should also be sent to the E.xecutive Legal Director U. S. Nuclear ~

Regulatory Commission Washington, D. C.

20555.

If a person other than the li ansee requests a hearing, that person shall set forth with

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l particult.rity the nature of their interest and the manner in which such interest may be affected by this. Order.

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l VI.

If a hearing is held concerning this Order, the issue to be considered at the hearing shall be:

Whether the licensee should be required to have the automatic p

1 system required by Section IV to be operable by April 9,1981.

Operation of the facility on terms consistent with this Order is not stayed by the penden;y of any proceedings on the Order.

OR THE NUCLEAR REGULATORY COMMISSION j

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i Darrell G. E,isenhu, 1 rector Division of Vicensing Office of Nuclear Reactor Regulation

1. 1. 6 Dated:

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5ethesda, Maryland

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