ML20003B527
| ML20003B527 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/09/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | COMMONWEALTH EDISON CO. |
| Shared Package | |
| ML20003B528 | List: |
| References | |
| NUDOCS 8102120351 | |
| Download: ML20003B527 (6) | |
Text
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E0a UNITED STATES OF AMERICA g
NUCLEAR REGULATORY COMMISSION In the Matter of COMMONWEALTH EDISON COMPANY Docket No. 50-249 (Dresden Nuclear Power Station Unit No. 3)
ORDER FOR MODIFICATION OF LICENSE I.
The Conno1 wealth Edison Conpany (licensee) is the holder of Facility Operating License No. DPR-25 which authcrizes the operation of the Dresden Nuclear Power Station, Unit No. 3,at steady state reactor power levels not in excess of 2527 megawatts thermal (rated power). The f acility consist,s of a boiling water reactor located at the licensee's site near Morris, 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 scre n from approximately 30% power. All rods were subsequently inserted within 15 minutes and no reactor damage or hazard to the public occurre'd. However, the event did cause an tri-depth review of the current BWR Control Rod Drive Systems which indentified design deficiencies requiring both short and long-term corrective measures. There measures are set forth in the Generic Safety Evaluation Report - BWR SCRAM DISCHARGE. SYSTEM, dated December 1,1980, prepared by th's NRC staff. One of the deficiencies identified was a failure mode of the control air system, which can conceivably cause an inability to scram 8102120)
7590-01 -
the control rods. Sustained low pressure in the control air system could result in complete or partial opening of multiple s'eram 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 at t!ie Quad Cities Unit 1 reactor on January 3,1977.
IE Bulletin 80-17 (Supplement 3) requires an immediate manual scram when icw pressure occurs in the Control Ttod 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). However, since only a short time could be available for the operator to successfully initiate a reac'er scram, 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 i
slow fill conditions; however it does not address completely all the potential loss of air events.
In addition, a human factors evaluation determined l
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 E'n2 control air supply systems, it is necessary that an automatic system be operable to initiate control red 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 lanc term solution to this problem.
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III.
The Generic Safety Evaluation Report (SER) of December 1,1980, recomended that this automatic air header dump syste:. be installed within two months. As a result of questions as to whether a reliable system could be installed within two months, the staff continued to review this require-ment. Wa have performed a more detailed risk assessment whf ch 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 alarus related to "e loss of air pressure in the air system. These alarms provide s::me a
.3 assurance that the operator can trip the reactor before the scram disc.arge volume
... fills-.. _ L As a result of these analyses I have determined that the public health, m_
safety and interest require that the automatic air dump system he in operation 1-within 90 days of the date of this Order and that operation during this period does not present an undue risk to the public health and safety.
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I have further determined based on staff evaluations of installed air t
l systems, and on staff discussions with industry repps'entatives that r-i a 90-day period will allow adequate time for design, procurement, e
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fabrication, installation, and testing for an automatic. air dump j
system of the type prescribed in this Order.
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7590-01 :
As discussed above, although (1) the failure of the control !'r 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 measures prescribed by this Order and their implementation on this short time s chedule.
However, in view of the irrraediacy of the need for this system, the system being manda'ted 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, including Sections 103 and 1611, and the Cornission's rules and regulations in 10 CFR Parts 2 and 50, IT IS ORDERED THAT EFFECTIVE IP. MEDIATELY, Facility Operating License No. DPR-25 is he eby 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 I
criteria:
(a) The system shall automatically initiate control rod insertion at j
l 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 I
unnecessary scrams;
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- (el Any required p:wer supply should not be subject to any i
failure made which could also initiate the degraded-air conditions, unless it can be demonstrated that an automatic scram will oc:ur promptly because of the failun mode of the t
power supply; (f) The, system is not subject to the require.v_nts of Appendices A and B oil 0 CFR 50:
l (g) There shall be a documented ir. dependent design review of the system; (h) Before the system is declared operable, a documented pre-operational test of the system will be sue:essfully completed; and 1
1 (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 9,1931, the Automatic Du=p Syste= as described above shall be operable in all modes other than shutdcwn 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 I
system operability is restored.
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7 5 6 0 0 1_.
Y.
The1teenseeoranypersonwt.:seinterestsmayheaffNtedby.this Order my request a hearing within 20 days of the date of p$blication of this Order in the Federal Register. Any request for a hearing will not stay the effective date of this Order.
Any request for a haaring shall be addressed to the Director, Office of Nuclear Rea: tor Regulation, U. S.
~
Nucleir Regulatory Cott:rission. Washington D. C.
20!55. A copy of the request should also be sent to the Executive Legal Director. U. S. Nuclear Regulatory Corx:ission. 'n'ashington, 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 wh.h such 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:
i Whether the licensee should be required to have the automatic g
I 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 pendency of any proceedings on the Order.
t FO', THE NUCLEAR REGULATORY C0!filSSION t
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T Da. e &{Eisenhu..
irector u.
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Division of LV:ensing.
Office of Nuclear Reactor Regulation l
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G Da:ed:
Eetnesda, Maryland
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