ML19256G047
| ML19256G047 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 12/19/1979 |
| From: | Howard J BOSTON EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| 79-270, NUDOCS 7912270320 | |
| Download: ML19256G047 (3) | |
Text
=
BOSTON EDISON COMPANY 600 SQYLSTON STR EET B o sTc N, MAssAcHussits 02199 J. EDWARD HOWARD vies massion=,
muc6aae December 19, 1979 BECo Ltr. #79-270 Mr. Thomas A.
Ippolito, Chief Operating Reactors 3 ranch 43 Division of Operating Reactors Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 License No. DPR-35 Docket No. 50-293 Interim Positions for Containment Purce and Vent Valve Operation
Reference:
a) USNRC Letter to BEco dated October 22, 1979
Dear Sir:
Reference a) requested Boston Edison Company to review the interim positions for containment purge and vent valve operation and commit, within 45 days, to operating in conformance with these positions. A three day extension of the specified reporting period was requested of and granted by Mr. John Hannon of your office in a telecon on December 14, 1979. Therefore, the following is now provided as our response to each of the subj ect interim positions.
Position 1.
Whenever the containment integrity is required, emphasis should be placed on operating the containment in a passive mode as much as possible and on limit-ing all purging and venting times to as low as achievable. To justify venting i
or purging, there must be an established need to improve working conditions to l
perform a safety related surveillance or safety related maintenance procedure.
(Examples of improved working conditions would include deinerting, reducing temperature, humidity, and airborne activity sufficiently to permit efficient performance or to significantly reduce occupational radiation exposures).
Response
Purge isolation valves are used far inerting 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after startup and for deinerting 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to shutdown as permitted by Technical Specifications.
The benefit gained by enabling access to the drywell for leak inspection during these periods is added plant safety withcut significantly reducing the margin in safety. This valve operation is limited in its use to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year during power operation.
/ )g y
.S 1643 118
/o l9122 7o
BOSTON EDISON COMPANY Mr. Thomas A. Ippolito, Chief December 19, 1979 Page 2 The two inch suppression pool purge isolation valves are operated in the open po sition to maintain the 1.5 psi differential pressure between the drywell and suppression chamber as required by Technical Specifications. These valves isolate upon receipt of a containment isolation signal. Therefore, emphasis has been placed upon operating the containment in a passive mode as much as possible and purging and venting times are limited to as low as achievable.
Position 2.
Maintain the containment purge and vent isolation valves closed whenever the reactor is not in the cold shutdown or refueling mode until such time as you can show that:
a.
All isolation valves greater than 3" nominal diameter used for containnent purge and venting operations are operable under the most severe design basis accident flow condition leading and can close within the time limit stated in your Technical Specifications, design criteria or operating procedures. The operability of butterfly valves may, on an interin basis,
be jemonstrated by limiting the valve to be no more than 30 to 50 open (90" being full open). The maximum opening shall be determined in consulta-tion with the valve supplier. The valve opening must be such that the critical valve parts will not be damaged by DBA-LOCA loads and that the valve will tend to close when the fluid dynamic forces are introduced.
Response
All isolation valves greater than 3" ncminal diameter used for centainment purge and venting operations are maintained in the closed position except during the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> inerting and deinerting periods as stated in the first res po ns e.
b.
Modifications, as necessary, have been made to segregate the containment ventilation isolation signals to ensure that, as a minimum, at least one of the automatic safety injection actuation signals is uninhibited and operable to initiate valve closure when any other isolation signal may be blocked, reset, or overridden.
Resconse A review of Pilgrim Station's Primary Containment Isolation System (PCIS) revealed two instances where the isolation signal can be overridden. These are the two isolation valves in series in a two inch line venting the suppres-sion chamber and two isolation valves in series in a two inch line venting the dryvell to the Standby Gas Treatment System. The control logic for these valves allows an override of the centai= cent isolation signal if the key leck control switch for these valves is in the emergency locked open position.
The override position, by design, provides capability to perform purging and venting operations te satisfy long term containment clean-up or pressure con-trol following a LOCA situation. Utilizing the everride capabil to inhibit 1643 119
BasTc4 EDISCN COMPANY Mr. Thomas A.
Ippolito, Chief December 19, 1979 Page 3 a particular isolating signal, inhibits all other isolation signals. Therefore, Boston Edison has developed a te=porary design modification which will be imple-mented immediately and a permanent design modification which will be implemented during the 1980 refueling outage which commences January 5,1980.
Temnorary Design Modification The emergency open function will be removed from the 2" vent valve circuitry.
To provide for the reinstallation of this function, should operating conditions require its avail bility, a procedure has been developed and issued which specifies the actions necessary to restore the " Emergency Open" function and directs a " dedicated" operator to manually close these valves in response to any subsequent containment isolation signals.
Permanent Design Modification The 2" vent valve " emergency open" circuitry shall be permanently modified in conjunction with the containment isolation system modifications planned in response to Lessons Learned, during the 1980 Refueling Outage.
This modifica-tion will segregate the containment isolation signals te ensure that bypassine one initiating signal does not inhibit reisolation of the 2" lines upon receipt of another isolation signal e.g. bypassing a "Hi Drywell Pressure" initiatinc signal will not inhibit reisolation of the 2" lines upon receipt of a " Low Reactor Vessel Level" signal.
Justification Boston Edison believes continued operation is justified until Januarv 3.1980 (Commencement of the 1950 Refuelinc outaze), on the basis that tencorary rencval of the " Emergency Open" control function f rom AO's 5041A&3 and 5043A63 consti-tutes no comprcmise in centainment isolation or venting capability followinz LOCA, while it eliminates the potential for non-isolation of the Containment Purge Bypass Valves in response to initial or subsequent diverse isolation sig na ls.
In conclusion we trust this information is responsive to your needs.
If we can be of any further assistance, please contact us at your convenience.
Very truly yours.
Commonwealth of Massachusetts) l_
'-[..
,(
County of Suffolk Then personally appeared before me J. Edward Howard, who, being duly sworn, did state that he is Vice President - Nuclear o f Boston Edison Company, the herein, and that he is duly authorited to execute and file the sub-applicant mittal contained herein in the name and on behalf of Boston Edison Ccmpany and the statements in said submittal are true to the best of his kncwledge that and belief.
164312])
/
My Commission expires:
/kd,/ff/
uY / O/.
'u c _/ /
Notdry Public
/