ML20083L679
| ML20083L679 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/13/1984 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8404170329 | |
| Download: ML20083L679 (3) | |
Text
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e, TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II April 13, 1984 Director of Nuclear Reactor Regulation Attention:
Ms. E. Adensam, Chief Licensing Branch No. 4 Divison of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Ms. Adensam:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
At the request of Carl Stahle of your staff, we are providing additional information to an exemption request provided also on April 13, 1984 for 12 additional components which have been unable to be completed during the unit 1, cycle 2 refueling outage. We are providing a revised enclosure which provides additional information and clarification to the previous submittal. All 12 items can be completed during non-outage periods as discussed in the enclosure.
At your request, TVA will reevaluate its listing of electrical equipment within the scope of 10 CFR 50.49 and will provide within 30 days to you a reconfirmation that the listing is complete and accurate.
If you have any questions concerning this matter, please get in touch with K. P. Parr at FTS 858-2685.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Nanager Nuclear Licensing Sworn togd subsopped. pefore me t is /3 day of(A M 1984.
l'a otary,Public My Commission Expires 64//[148Y.
Enclosure cc:
U.S. Nuclear Regulatory Commission (Enclosure)
)Wl Region II fV Attn: Mr. James P. O'Reilly, Regional Administrator F
.101 Marietta Street, NW, Suite 2900 l
f Atlanta, Georgia 30303 8404170329 840413 PDR ADOCK 05000327 P
PDR An Equat Opportunity Employer
ENCLOSURE f
NEB 8152 The six components listed below are used as containment isolation valves.
It was determined that certain environmental conditions could exist that might cause a failure of the limit switches assoicated with the valves listed below. This modification will entail extensive wiring changes (i.e., cable pulling, terminations, etc.) of which the design nature is not fully known at the current time. The current design of the modification consists of logic changes to these valves to ensure that the valves in question will not reopen during a postulated submergence event.
This modification will be completed substantially before the March 31, 1985, date. Our current schedule is to have these modificaticas completed by June 1, 1984, providing the present design can be implemented.
FCV-62-72, 73, 74 ; FCV-77-16; FCV-87-7, 8.
JUSTIFICATION FOR CONTINUED OPERATION (JCO)
Letdown valves 1-FCV-62-74, 1-FCV-62-73, and 1-FCV-62-72 use a limit switch in the containment isolation seal-in circuit. Failure of these limit switches due to submergence inside contaiment could result in the reopening of the valves if the Phase A containment isolation signal was reset. Several other conditions would have to occur together with the limit swtich failure in order to allow the valve to enner on reset of the isolation signal. These include:
1.
Limit switch failure gives a " valve open" sign 2.
valve solenoid and valve operator must not fai.
mergence; 3
interlock with other inboard letdown isolation
-how these valves to be " full open;"
4.
one charging pump must be running; 5.
pressurizer level greater than 17 percent aus in,
- channels, 6.
the control swtich must be in the A-Auto positic 6nd 7.
control air must be available at the valve.
If the above conditions are met the valve would reopen when the Phase A signal is reset. Containment isolation would not be lost unless the outboard isolation valve failed open. Futhermore, the control circuit for the inboard containment isolation valves are designed such that they can be closed from the main control room regardless of the status of the
" full open" limit switches.
These conditons make it highly unlikely that containment isolation will be lost upon reset of the containment isolation signal.
Test valves 1-FCV-87-7, 1-FCV-87-8, and 1-FCV-77-16 also use a limit switch in the containment isolation seal-in circuit. Failure of these limit switches due to submergence inside containment could result in the reopening of the valves if the Phase A containment isolation signal was reset. Several conditions would have to occur together with limit switch failure in order to allow the valve to reopen on reset of the isolation signal. These include:
1.
Limit switch failure gives a " valve open signal,"
2.
valve, solenoid and valve operator must not fail due to submergence 3
control switch must be in the A-Auto position, and 4.
control air must be available at the valve.
If the above conditions are met the valve would reopen when the Phase A signal is reset. Containment isolation would not be lost unless the outboard isolation valves and other outboard valves failed open or were open. There are several normally closed manual isolation valves downstream of 1-FCV-87-7 and 1-FCV-87-8.
There is a gas analyzer sequencing valve downstream of 1-FCV-77-16. Furthermore, the control circuit for the inboard containment isolation valves are designed such that they can be closed from the main control room regardless of the status of the " full open" limit switches.
These conditions make it highly unlikely that containment isolation will be lost upon reset of the containment iso' ation signal.
For the above listed components we affirm that the NRC has been provided appropriate JCO's for the time up to the end of the unit 1, cycle 2 refueling outage. This JC0 has not changed and remains valid up until the schedules indicated for replacement.
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