ML20003B888
| ML20003B888 | |
| 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 8102260061 | |
| Download: ML20003B888 (6) | |
Text
'.
O 7590 01 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of TENNESSEE VALLEY AUTHORITY
)
Docket No. 50-259
)
(Browns Ferry Nuclear Plant, Unit
)
No. 1)
ORDER FOR MODIFICATION OF LICENSE I.
The Tennessee Valley Authority (licensee) is the holder of Facility Operating License No. DPR-33 which authorizes the operation of the Browns Ferry Nuclear Plant, Unit No.1, at steady state 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.
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 307, 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 8:1022.6 M
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 7
f opening of the scram inlet valves, cau:ing the Scram Discharge Volume l
(SDV) to fill rapidly, thus leaving a relatively short time for the operator i
to take corrective action before scram capability is lost.
It appears ti.at i
I type (but with no adverse consequences) actually occurred an event of this generiti
~
l at the Quad Cities Unit I reactor en January 3,1977.
IE Bulletin 80-17. (Supplement 3) requires an i=nediate manual scram when I-low pressure occurs in the Control Rod Drive (CRD) air system or when othes indications occur, such as multiple rod drift alarms or a marked change in the number of control rods that are at high temperature. Beginning en December 1,1980, protection was also provided by continuous monitoring of the SDV as required by IE Bulletin 80-17 (Supplement 11. However, since only i
a short time could be available for the operator to successfully initiate a reactor scr'am, a question mmains as to the adequacy of equipment and
~
procedures. This continuous acnitoring system and operator response provide important protection against water accumulation in the SDV headers under l ~
slow fill conditions; however it does not address ccmpletely all the potential loss of air events.
In addition, a human factors evaluation determined tfutt reliance on the operator to successfully carry out a manual scram within i
a limited time frame may' not be assured. Therefore', in the short term in order to provide prompt added prrtection for credible degraded air conditions 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 l
air system header if the air pressure decreases below a prescribed value.
. Tne NRC staff is developing revised design and safety criteria for a lone term j
solution to this problem.
3
,-----m.
.,-ec
,,e
.+,.,,m.,
--e w
3
7590 01_ -
4 III.
The Generic. Safety Evaluation Report (SER) of December. l.1980, rece mended that this automatic air header dump system be installed within l
I two months. As a result of questic'ns as to whether a reli.able system could 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 1 css 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 alarm related to the less of air pressure in the air system. These alams provide some added assurance that the operater can trip the reactor before the scram discharge volume
.. filis....-.
I,-- -
As a result of these analyses I have determined that the public health,
- b...
safety and interest require that the automatic air du=p system be in operation L
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
.u i
systems, and on staff discussions with industry rep [entatives that
~
~~ ~
a 93-day period will allow adequate time for design, procurement, fabrication, installation, and testing for an automatic. air dump system cf-the type prescribed in this Order.
M
,, u..;.
. -. ~..
~
~.. - -
~
i
]59001.
As discussed above, although (1) the failure of the control air system is c. 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 schedule. However, in view of the innediacy of the need for this system, thecsystem 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 1611, 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-33 is hereby amended to add the following provisions:
(1)
An automatic system shall be opeable to initiate control rod insertion l
on low pressure in the control air header, which meets the following criteria:
l (a) The system shall automatically initiate control rod insertion at i
10 psi or greater above scram outlet velve opening pressure; I
(b) The system shall not degrade the existing safety systems (e.g.,
(c) The system shall al!N for scram reset;
~
(d) Tl.1 design shall consider the potential for inadvertent or unnecessary scrams; l
l
I 7590 01 5-Lel 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 premptly because of the failu e node of the power supply; (f) The system is not subject to the requirements rf Appendice A
~
and B cf'10 'C R 50; (g) There shall be a documented independent design review 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 at each Unit shutdown, but need not be tested more than once each 90 days.
(2) After April 9,1981, the Automatic Dump Syste= as described above shall be operable in all modes other than shutdewn 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 sys>Jn operability is restored.
4
.... n., ~.
E590 01 Y.
- m...
.. ~. - - '
The licenses or any persen whose interests may he affected by, this
' ~
Order rnay request a hearing within 20 days of the date of publici.tfon of this 3rder in the Federal Re;fster. Any request for a hearing will not
~~
stay the effective date of this Order.,ny request for a hearing shall be addressed to the Director, Office of Nuclear Reactor Regulation,U. S.
fiucle'ar Regulatory Cot:=ission. Washington, D. C.
20555. A copy of the
. -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 r.anner in which such ir.terest may be affected by this. Order.
VI.
t 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 IY 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 oroceedings on the Order.
', THE NUCLEAR REGULATORY COPEISSION OP I.
, y.,.
{ iser. hut, 1
irector Darrel Division of' Licensing-Office of Nuclear Reactor Regulation l..
I-Dated: #N 5 G31 Sethesda, Maryland
.