ML20003B890
| ML20003B890 | |
| 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 8102260070 | |
| Download: ML20003B890 (6) | |
Text
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50?hl UNITED STATES OF AMERICA NUCLEAR REGULATOR 1 ':0MMISSION l
In the Matter of
)
)
TENNESSEE VALLEY AUTHORITY
)
Docket No. 50-260
)
(Brcuns Ferry Nuclear Plant, Unit
)
No. 2)
ORDER FOR MODIFICATION OF LICENSE I.
The Tennessee Valley Authority (licenses).s the holder of Facility Operating License No. DPR-52 which authcf;m the operation of the Browns Ferry Nuclear Plant, Unit No. 2, at ste.W state reactor power levels not in excess of 3293 megawatts th9ful (rated power). The facility censists of a boiling water rew-located at the licensee's site in Limestone County, Alabama.
II.
During a rerMne shutdown of Browns Ferry Unit No. 3 on June 28, 1980, 76 of 185 cot.Tht rods failed to fully insert in response to a manual scram from ' app' wtately 307. power. All rods were subsequently inserted within 15 mitym and no reactor damage or hazard to the public occurred. However, the eient did cause an in-depth review of the current BWR Control Rod Drive
.hsce:s which indentified design deficiencies requiring both short and long-tern 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
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7590-01 the control rods.
Sustained low pressure in the control air system could result in complete or partial opening of multiple scram outlet valves before f
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 the Quad Cities Unit i reactor on January 3,1977.
IE Bulletin 80-17 (Supplement 3) requires an ic:nediate manual scram when low pressure occurs in the Control Rod Drive (CRD) air system or when other indications occur, such as multiple rod drift alams or a marked chang; in l
the number of control rods that are at high temperature.
Beginning on December 1,1980, protection was also provided by continuous mon'toring of the SDV as requ' ired by IE Bulletin 80-17 (Supplement 1). However, since only a short time could be available for the operator to successfully initiate a reactor t ci am, a question remains as to the adequacy of equipment and
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procedures. This continuous monitoring system and operator response provide important protection against water accumulation in the SDV headers under l
l, slow fill conditions; however it does not address ccmpletely all the potential loss of air events.
In addition, a human factors evaluation detennined l
that 7cliance 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 l
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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.
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l Tne NRC staff is developing revised design and safety criteria for a lona term solution to. this problem.
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7390E 3-III.
The Generic Safety Evaluation Report (.SER) of December.1,1980, recomended that this automatic air header dump system 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 rsview this nquire-ment. We have performed a more detailed risk assessment whf ch has shown a i
lower probability for the less of scram capability due to a loss of air than cur 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 alanns provide some added assurance
-hat the operator can trip the reactor before the scram discharge volume
. fills.
As a result of these analyses I have detemined that the public health, 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 period does not present an undue risk to the public health and safety.
I have further determined based on staff evaluations of installed air systems, and on staff' discussions with industry repr,es'entatives that a 90-day period will allow adequate time for design, procurement, l
fabrication, installation, and testing for an automatic. air dump
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l system of the type prescribed i-this Order.
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7590-01 4-As discussed above, although (1) the failure of the control air system is a lcw 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 inplementation on this short time s chedule. However, 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.
Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, including Sections 103 and 1511, and the Comission's rules and regulations in 10 CFR Parts 2 and 50, IT IS ORDERED THAT EFFECTIVE IMMEDIATELY, Facility Operating License No. DPR-52 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 scran:s; y
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759001 5-(el Any required power supply should not be subject to any failure mode which could also initiate the degraded-air conditions, unless it can be demonstrated that an automatic scram will occur promptly because of the failure mode of the i
power supply; (f) The system is not subject to the requirements of Appendices A and B cf'10 CFR 50; (g) There shall be a documented independent design review of the system; l
(h) Before the system is declared operable, a documented pre-operational test of the system will be successfully l
completed; and (i) The system shall be functionally tested at each Unit shutdown, l
but need not be tested more than once each 90 days.
(2) After April 9,1981, the Automatic Dump System as described above shall i
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 rettored.
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V.
The Itcensee or any person wh :e interests may be affected by.this be ~ may request a hearing within 20 days of the date of phblication of
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this Order in the Federal Reefster. Any request for a hearing Will not stay the effective date of this Order. Any request for a hearing shall be
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addressed to the Director Office of Nuclear Reactor Regulation, U. S.
NucTear Regukatory Com::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 tha$.
the licensee requests.a hearing, that person shall set forth with particularity the nature of their interest and the manner in which su:0 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:
Nhether the licensee should be required to have the automatic g
system required by Section IV to be operable by Aprk19,1981.
Operation of the facility on ter=s consistent with this Order is not stayed by the pendency of any proceedings on the Order.
dR THE NUCLEAR REGULATORY COW.ISSION
. Y
.hu., h C
u.tief c.or
.re Division of Licensing-Office of Nuclear Reac*ar Regulation Dated:
Bethesda, Maryland