ML20008F014
| ML20008F014 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/09/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML20008F015 | List: |
| References | |
| NUDOCS 8103120029 | |
| Download: ML20008F014 (6) | |
Text
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7590 01 UNITED STATES OF AMERECA g
NUCLEAR REGULATORY COMMISSION In the Matter of
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COMMONWEALTH EDISON COMPANY
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Docket No. 50-237
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(Dresden Nuclear Power Station,
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Unit No. 2)
ORDER FOR MODIFICATION OF LICENSE I.
The Commonwealth Edison Company (licensee) is the holder of Provisional Operating License No. DPR-16 which authorizes the operation of the Oyster' Creek Nuclear Generating Station at steady state reactor power levels not in excess of 1930 megawatts thermal (rated power).
The facility consists of a boiling water reactor located at the licensee's site in Grundy County, Illinois.
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.ods were subsequently inserted within 15 minutes and no reactor damage or hazard to the public occurred. However, j
the event did cause an in-depth review of the current BWR Control Rod Drive l
Systems which indentified design deficiencies requiring both short and long-term corrective measures. These measures are set forth in the Generic Safety Evaluation Report - BWR SCRAM DISCHARGE SYSTEM, dated December 1,1980, prepred by the NRC staff. One of the deficiencies identified was a failure
" mode of the control air system, which can conceivable cause an inability to scram l
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. 73g3 y 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 capability is lost.
It appears that an' event of this general type (but with no adverse consequences) actually occurred i
at tee Q"ad Cities Unit 1 reactor en January 3,1977.
IE Sulletin 80-17 (supplement 3) requires an immediate manual scram when l
low pressure occurs in the Control Rod Drive (CED) 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 tem;erature.
Beginning en December 1,1980, protection was also provided by continuous monitoring cf j
the SDV as required by IE Eu11etin 80-17 (Supplement 1).
However, since only a shcrt time could be available for the operator to successfully initiate a reactor scram, a question remains as to the adequacy of equipment and rf precedures. This continuous monitoring system and operator response provide i
,f important protection against water accumulation ir the SDV headers under slow fill conditions; h: wever it does not address ccmpletely all the potential loss of air events.
In addition, a human factors evaluation detemined 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 Ba 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.
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Tne NRC staff is developing revised design and safety criteria for a inna term solution to. this problem.
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III.
The Generic Safety Evaluation Report (SER) of Deceder.1,1980, recommended that this automatic air header dump syster, be installed within two months.
As a result of questions as to whether a reliable system could I
be installed within two months, the staff continued to review this require-ment. We have performed a more detailed risk assess ent which has shown a lower probability for the loss o'f scram capability i:e 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 air pressure in the air system. These alams provide some added assurance that the operator can trip the reactor before the scram discharge volume i
filis.
f 4-As a result of these analyses I have determined that the public health, T--
i safety and interest require that the automatic air dump system be in operation within 90 days of the date of this Order and that operation during this l "__.
period does not present an undue risk to the public health and safety.
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!i I have further determined based on staff evaluations of installed air systems, and on staff discussions with industry rept,esentatives that a 90-day period will allow adequate time for design, procurement, fabrication, installation, and testing for an automatic air dump I
system of the type prescribed in this Order.
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i As discussed above, although (1) the failure of t?ie 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 tem fix are currently being developed, I have detemined 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.
i Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, including Sections 103 and 1611, and the Commission's rules and regulations in 10 CFR Parts 2 and 50, IT IS ORDERED THAT EFFECTIVE IMMEDIATELY, Provisional Operating License No. DPR-19 is hereby amended to add the following j
provisions:
f (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; i
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(.el Any required pcwer 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 failunt mode of the i-power supply;
(.f) The system is not subject to the requirements of Appendices A andBok10CFP,50; '
(g) There shall be a decumented independent design review I
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 et each Unit shutdown, but need not be tested more than once each 90 days, i
i (2) After April 9,1951, 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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The licensee or any person whose interests may be affected by this Order may request a hearing within 20 days of the date of publication of
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this Order in the Federal Recister. Any request for a hearing will not i
stay the effective date of this Order.
Any req'.es fer a hearing shall be
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addressed to the Director, Office of Nuclear Reactor Regulation, U. S.
Nucleir Regulatory'Cc=ission, Washington, D. C.
20555. A copy of the request should also be sent to the Executive Legal Director, U. S. Nuclear Regulatory Co=ission, k'ashington, D. C.
20555.
Ifapersonothertha$
the licensee requests.a hearing, that person shall set forth with particularity the nature of their interest and the manner in which such intemst 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 3
system required by Section IV to be operable by April 9,1981.
Operation of the facility on terr.s consistent with this Order is not stayed by the pendency of any proceedings on the Order.
$0R THE NUCLEAR REGULATORY COMMISSION
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Director Darrei Division of Cicensing Office of Nuclear Reactor Regulation
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Dated:
- 8 Bethesda, Maryland