ML20003B864
| ML20003B864 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/09/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | NORTHERN STATES POWER CO. |
| Shared Package | |
| ML20003B865 | List: |
| References | |
| NUDOCS 8102260015 | |
| Download: ML20003B864 (6) | |
Text
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D 590 ul UNITED STATES OF AMERICA NUCl. Eta REGULATORY C0lHISS10N In the Matter of Oocket No. 50-263 NORTHERN STATES POWER COWANY (Monticello Nuclear Generating
)
Plant)
ORDER FOR MODIFICATION OF LICENSE I.
The Northern States Power Conpany (licensee) is the holder of Provisional Operating License No. OPR-22 which authorizes the operation of the Monticello Nuclear Generating Plant, at stea# state reactor power levels not in excess of 1670 megawatts thermal (rated power).
The facility consists of a boiling water reactor located at the licensee's site in Wright County, Minnesota.
II.
28, 1980, During a routine shutdown of Browns Ferry Unit No. 3 on June 76 of 185 control rods failed to fully insert in response to a manual scram All rods were subsequently inserted within from approximately 30% power.
- However, 15, minutes and no reactor damage or hazard to the public occurred.
the event did cause an in-depth review of the current B)E Control Rod Drive Systems which indentified design deficiencies requiring both short and long-These measures are set forth in the Generic Safety term corrective measures.
Evaluation Report - BWR SCRAM DISCHARGE SYSTEM, dated Decenber 1,1980, One of the deficiencies identified was a failure prepared by the NRC staff.
mode of the control air system, which can conceivably cause an inability to scram 81022eg975
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1 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 (SOV) to fill rapidly, thus leaving a relatively short time for the operator to take corrective action before scram capability is lost.
It appears that an event of this generil type (but with no adverse consequences) actually occurred at th'e 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 control rods that are at high temperature. Beginning on December 1,1980, protection was also provided by continuous monitoring of the SDV as required by IE Bulletin 80-17 (. Supplement 1). liowever, since only a short time could be available for the operator to successfully initf ate i
a reactor sham, a question remains as to the adequacy of equipment and procedures. This continuous monitoring system and operator response provide important protection against water accumulation in the SDV headers under slow fill conditions; however it does not address completely all the potential loss of air events.
In addition, a human factors evaluation detencined 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.
l The NRC staff is developing revised design and safety criteria for a lona term solution to. this problem.
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i III.
The Generic Safety Evaluation Report (SER) of Decenber.1,1980, recomended that this automatic air header dump syster be installed within two months. As a result of questions as to whether a reliable system could be installed within two months, tr staff continued 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 reevaluated 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 E
air pressure in the air system. These alams provide sone added assurance that the operator can trip the reactor before the scram discharge volume
._. fills..
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As a result of these analyses I have determined that the public health, r_.
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safety and interest require that the automatic air dump system be in operation
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within 90 days of the date of this Order and that operation during this Y
period does not present an undue risk to the public health and safety.
I have further detamined based on staff evaluations of installed air i
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systems, and on staff discussions with industry representatives that
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a 90-day period will allow adequate time for design, pmcurement.
fabrication, installation, and testing for an automatic air dump system of the type prescribed in this Order.
a-o 9
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7590 01 As discussed above, although (1) the failure of the control air system
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is a low probability event, (2) the actions already required provide a f
significant measure of assurance that such an event will not occur and I have (3) the criteria for a long term fix are currently being developed, determined that the public health and safety require the additional measures prescribed by this Order and their implementation on this short time schedule. However, in view of the immediacy 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 Part 50.
IV.
Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, including Sections 103 and 1611, and the Comission's rules and regulations in 10 CFR Parts 2 and 50. IT IS ORDERED THAT EFFECTIVE IMEDIATELY, Provisional Operating License No. DPR-22 is hereby amended to add the following provisions:
(1)
An automatic system shall be operable to initiate control rod insertion on low pressure in the control air header, which meets the following criteria:
(a) The system shall automatically initiate control rod insertion at 10 psi or greater above scram outlet valve opening pressure; (b) The system shall not degrade the existing safety systems (e.g.,
(c) The system shall allow for scram reset; (d) The' design shall consider the potential for inadvertent or unnecessary scrams; 1
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7590 01 s-(el Any required power supply should not be subject to any failure mode which could also initiate the degrad,ed-air conditions, unless it can be demonstrated that an automatic scram will occur promptly because of the failure mode of the Power supply; (f) The, system is not subject to the requirements of Appeiidices A and B of 10 CFR 50; s
(g) There shall be a documented independent design review of the system; (h) Before the system is declared operable, a documented pre-operational test of the system will be successfully completed; and (i) The system shall be functionally tested at each Unit shutdown, but need not be tested more than once each 90 days.
(2) After April 9,1981, 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 sliutdown 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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- i V.
,72L The licensee or any person whose interests may be affected by.this Order may request a hearing within 20 days of the date of phblication of this Order in the Federal Register. Any request for a heart.ng will not
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stay the effective date of this Order. Any request for a hearing shall be addressed to the Director Office of Nuclear Reactor Regulation.,U. 5.
Nucle'ar Regulatory Connission, Washington, D. C.
20555. A copy of the g.
request should also be sent to the E:ecutive Legal Director, U. S. Nucle r Regulatory Connission, Washington, D. C.
20555. If a person other than the licensee requests.a hearing, that person shall set forth with particularity the nature of their interest and the manner in which such e
interest may be affected by this. Order.
VI.
If a hearing is held concerning this Order, the issue to be considered
(
at the hearing shall be:
l Whether the licensee should be required to have the automatic j
system required by Section IV to be operable by April 9,1981.
Operation of the facility on terms consistent with tnis Order is not stayed by the pendency of any proceedings on the Order.
R THE NUCLEAR REGULATORY COM4ISSION fI rell senhut, Director Division o Licensing Office of Nuclear Reactor Regulation 8
Dated: # #
Bethesda, Maryland
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