ML20003B895
| ML20003B895 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/09/1981 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | TENNESSEE VALLEY AUTHORITY |
| Shared Package | |
| ML20003B889 | List: |
| References | |
| NUDOCS 8102260081 | |
| Download: ML20003B895 (6) | |
Text
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Q UNITED STATES OF AMERICA O
NUCLEAR REGULATORY COMISSION In the Matter of
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TENNESSEE VALLEY AUTHORITY Docket No. 50-296 (Browns Ferry Nuclear Plant, Unit
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No. 3)
ORDER FOR MODIFICATION OF LICENSE I.
The Tennessee Valley Authority (licensee) is the holder of Facility Operating License No. OPR-68 which authorizes the operation of the Browns Ferr,y Nuclear Plant, Unit No. 3, at steady tate reactor power levels not in excess of 3293 megawatts thermal (rated power). The facility consists of a. boiling water reactor located at the licensee's site in Limestone County, Alabama.
II.
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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 l
from approximately 307, power. All rods were subsequently inserted within l
l 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 mtasures. 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 410226 0c#
7590 01_
2 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 Dischtrge Volume (SDV) to fill rapidly, thus leaving a relatively short tit e for the operator to take ccrrective action before scram capability is lost.
It appears that an event of this general type (but with no adverse consequencesi actually occurred at the 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 indications occur, such as multiple rod drift alanns or a marked change in ti.e 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 operatcr to successfully initiate a reactor sciam, a questien remains as to the adequ.:y of equipment and l
procedures. This continudus monitoring system and operator response provide important protection against water accumulation in the SDV headers under I
slew fill conditions; however it does not address completely all the potential loss of air events.
In addition, a human factors evaluation detennined l
l-that reliance on the operator to successfully carry out a manual scram within I
a limited time frame mai not be assured. Therefore, in the short term in l
order a provide prompt added protection for credible degraded air conditions in BWR control air supply systems, it is necessary that an automatic system l
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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E590 di III.
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The Generic Safety Evaln1* ion Report (SER) of December.1,1980, recomended that this automatic air header dump system be installed within two months. As a nsult of questio'ns as to whether a reli.able system could t
be installed within two months, the 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 l
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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 rea: tor on alarms related to the loss of l
air pressure in the air system. These alarms provide some added assurance
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that the operator can trip the reactor before the scram discharge volume i
1 fills.
e As a result of these analyses I have determined that the public health, l[.
g-safety and interest require that the automatic air dump system be in operation within 90 days of the date of this Or<ier and that operation during this
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period does not present an undue risk to the public health 1"d safety.
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i have further determined based on staff evaluations o' installed air
.e systems, and on staff discussions with industry repre'sentatives that
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a 90-day period will allow adequate time for design, procurer:at, fabrication, installation, and testing for an automatic. air dump system of the type prescribed in this Order.
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7590 01 As discussad 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 assuran.a that such an event will not' occur and (3) the criteria for a 1:ng term fix are currently beinc developed.
I have determined that the public health and safety require the additional l
measures prescribed by this Crder and their implementation on this sr. ort time i
schedule. Mcwever, in view of the insnediacy 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.
l Accordingly, pursuant to the Atomic Energy Act of 1954, as amend %
i ncludi r.9 Sections 103 and 161i, and the Comission's rules and regulations i
in 10 CFR Parts 2 and 50, IT IS ORDO'O THAT EFFECTIVE IMMEDIATELY, Facility Operating License No. DPR-68 is hereby amended to add tha 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 l
10 psi or greater above scram nutlet valve opening pressure; l
(b) The system shall not degrade the existing safety systems (e.g.,
(c) The system shall allow for scram reset; The design shall consider the potential for inadvertent or (d) unnecessary scrams;
7590 01 5-(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 Appendices A and B of'10 CFR 50;
,e (g) There shall be a documented independent design review of the systec:;
(h) Before the system is declared operable, a documented pre-operational test of the system will be successfully-com;leted; 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 shutdown condition within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> unless smem operability is restored.
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7530 01 Y-u
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The licer.see or any person whose interests may he affected by. this
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Ort.2r may request a hearing within 20 days of the date of publication of
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this 3rder in the Federal Register. Any request for a hearing will not stay t'he effective date of this Order.
Any request for a hearing shall be addressed to the Di ector, Office of Nuclear Reactor Regulation, U. S.
Nucleir Regulatory >Co=ission, Washington, D. C.
20555. A copy of the
-request should also be sent to the Executive Legal Director, U. S. Nuclear Regulatory Comission 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 i
i interest may be 'affected by this. Order.
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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 g
system required by Section IV to be operable by April 9,1981.
l Operation of the facility on terms consistent with this Order is not stayed by the pendency of any proceedings on the Order.
R THE NUOLEAR REGULATCRY C0!94ISSION y.
A
=lse.. hut, irector Divisionofficensing'.
Office of Nu: lear Reac+4r Regulation Dated:
Bethesda, Maryland
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