ML19341C781
| ML19341C781 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 01/09/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | CONNECTICUT YANKEE ATOMIC POWER CO. |
| Shared Package | |
| ML19341C779 | List: |
| References | |
| NUDOCS 8103040177 | |
| Download: ML19341C781 (6) | |
Text
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
)
{
CONNECTICUT LIGHT AND POWER
)
1 THE HARTFORD ELECTRIC LIGHT CO.
)
Docket No. 50-E45 l
WESTERN MASSACHUSETTS EL'"TRIC CO.
)
AND NORTHEAST NUCLEAR ENERGY CO.
)
(Millstone Nuclear Power Station, UnitNo.1)
ORDER FOR MODIFICATION OF LICENSE I.
.The Connecticut Light and Power, The Hartford Electric Light Co.,
Western Massachusetts Electric Co., and Northeast Nuclear Energy Co.
(licensees) are the holders of Provisional Operating License No. DPR-21 which 1j authorizes the operation of the Millstone Nuclear Power Station, Unit No.1 at steady state reactor power levels not in excess of 2011 megawatts I
thermal (rated power). The facility consists of a boiling water reactor located at the licensee's site in Waterford, Connecticut.
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 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, 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 8103 040.177 ca
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the centrol rods.
Sustained low pressure in the control air system could result in complete or partial opening of multiple scram outlet valves befort opening of the scram inlet valves, causing the Scram D,ischarge Volume (SDV) to fill rapidly, thus leaving a relatively short-time for the operator to take corrective action before scram capability is 1,ost.
It appears that an event of this general type (but with no adverse consequences)~ actually occurred at th'e Quad Cities Unit I 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 i
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 1
December 1,1980, protectica was also provided by continuous monitoring of the SDV as required by IE Eulletin 80-17 (Supplement ll.
However, since only a short time could be available for the operator to successfully initiate
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a reactor scrac, a questien remains as to the adequacy of ecuipment and 2.
h procedures. This continuous monitoring system and o'perator response provide important protection against water accumulation in the SDV headers under slow fill conditions; however it does not address completely all the potential less of air events.
In addition, a human factors evaluation determined that reliance on the operator to successfully carry out a mandal scram within a limited time frare 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 cor. trol 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 lona term solutica to this problem.
7590 01 3-f 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. We have performed a core detailed risk assessment wh!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 reevaluatec the human factors involved in carrying' out the requirements of IE Bulletin 30-17 (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 fi11s.
As a result of these analyses I have deterrined that the public health, safety and interest require that the automatic air dump system be in operation y
within 90 days of the date of this Ordhr 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
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systems, and on staff discussions with industry representatives that a 90-day period will allow adequate time for design, procurement, fabrication, installation, and *asting 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 h:alth and safety require the additional measures prescribed by this Order and their implementation on this short time s chedale. However, in view of the imediacy of the need for this system, the system being mandated by this Order is not being made subject to the recuirements of Appendices A and B to 10 CFR Part 50.
IV.
I Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, 6
in:luding Sections 103 and 1611, and the Comission's rules and regulations i
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in 10 CFR Parts 2 and 50, IT IS ORDERED THAT EFFECTIVE IK'CDIATELY, Provisional I
Operating License No. DPR-21 is hereby amended to add the following l
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;
/590 01 l
Cel Any required pcwer supply should not he subject to any failure made which could also initiate the degrad,ed-air conditions, unless it can be demonstrated that an automatic scram will occur prcmptly because of the failure mode of the power supply; (f) The system is not subje:t to the requirements of Appendices A and B of'10 CFF, 50;
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(g) There shall be a documented independer.t design review of the system; (h) Before the system is declared operable, a documented i
pre-op,erationa' test of the system will be su::essfully completed; and (i) The. system shall be functionally tested c each Unit shutdown, but need not be tested more than once each 90 days, i
(2) After April 9,1981, the Automatic Dump System as described above shall be operable in all modes other than shutdcen and refueling or the unit shall be placed in a cold shutdown conditi:n within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> unless 4
system operability is restored.
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The licensee or any person whose interests may be affected by. this
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Crder may request a hearing within 20 days of the date of publication of this Order in the Federal Re;fster. Any request for a hearing Will n:t stay the effective date of this Order.
Any re:;uest for a hearing shall be addres ed to the Director, Office of Nuclear Rea: tor Regulation. U. S.
Nucleir Reguiatory Co=fssien, Washingt:n, D. C.
20555. A copy of the 4
request should also be sent to the Executive Legal Director, U. S. Nuclear Regulatory Commission, 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 su:h interest may be affected by this. Order.
i 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 system required by Section IV to be operable b April 9,1381.
j Operation of the facility on terr.s consistent with this Order is not stayed by the pendency of any pro:eedings on the Order.
[0RTHENUCLEAP, erULATORY COMMISSION r
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4 Dar e G. (E, ser. hut, Director Division ofdLicensing-Office of Nu: lear Reactor Regulation Dated: ^*iN Y 9 1581 Sethesda, Maryland
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