ML19210C546
| ML19210C546 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/23/1979 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 7911190070 | |
| Download: ML19210C546 (5) | |
Text
-
I ct%
c A nau
[p q(o, UNITED STATES P(,g NUCLEAR REGULATORY COMMISSION y
w g
/.E WASHINGTON, D. C. 20s55
\\..../
r October 23, 1979 Docket No. 50-29 Mr. Robert H. Groce Licensing Engineer Yankee Atomic Electric Company 20 Turnpike Road Westboro, Massachusetts 01581 Lear M:. Groce:
RE: Containment Purging and Venting During hormal Operation By letter dated November 29, 1978, the Commission (NRC) requested all licensees of operating reactors to respond to generic concerns about containment purging or venting during normal plant operation. The generic concerns were twofold:
(1) Events had occurrea where licensees overroce or Dypassed the safety actuation isolation signals to the containment isolation vcives.
These events were determined to be abnormal occurrences and reported to Congress in January 1979.
(2) Recent licensing reviews have required tests or analyses to show that containment purge or vent valves would shut without degrading con-tainment integrity during the dynauic loacs of a design basis loss of coolant accicent (DBA-LOCA).
The WRC position of the Noveuber 1978 letter requested that licensees take the following positive actions pending coupletion of the NRC review:
(1) pronioit the override or bypass of any safety actuation signal which woulc affect another safety actuation signal; the TMC Office of Inspection
'and Enforcement would verify that administrative controls prevent improper manual defeat of safety actuation signals, and (2) cease purging (or venting) of containment or limit purging (or ventin9) to an absolute minimum, not to exceed 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year. Licensees were requested to deuonstrate (by test or by test and analysis) that containment isolation valves would shut under postulated DBA-LOCA condition. The NRC positions were amplified by citation (and an attached copy) of our Standard Review Plan (SRP) 6.2.4 Revision 1 and the associated Branch Technical Position CSB 6-4, which have effectively classed the purge and vent valves as
" active" invoking the operaoility assurance program of SRP 3.9.3.
The NRC staff has mace site visits to several facilities, has uet with licensees at Bethesda, Maryland, and has held telecon conferences with many other licensees anc met with soue valee uanufacturers. During these aiscussions, the NRC staff has stressed that positive actions must be taken as noted above to assure that contai.%ent entegrity would be maintainea in the event of a DBA-LOCA.
1354 047 7911190 0 9 O 7
Mr. Robert H. Groce October 23, 1979 As a result of these actions, we have learned from several licensees that at least three valve vendors have reported that their valves may not close against the ascending differential pressure and the resulting dynamic loading of the design basis LOCA. All identified licensees who are affected have proposed to maintain the valves in the closed position or to restrict the angular opening of the valves whenever primary containment integrity is required until a re-evaluation is provided which shows satisfactory valve performance under the DBA-LOCA condition.
Recently, a report under 10 CFR Part 21 was received by the NRC from the manufacturer of butterfly valves which are installed in the primary containment at the Three Mile Island Unit 2 Nuclear Station. These butterfly valves are used for purse and exhaust purposes and are required to operate during accident conditions. The report discusses the use of an unqualified solenoid valve for a safety-related valve function which requires operation under accioent conditians. The solenoid valve is used to pilot control the pneumatic valve actuators which are installed on the containment ventilation butterfly valves at this facility.
?our re-evaluation of valve performance for conditions noted in the previous paragraph must consiaer the concerns iaentified in IE Bulletin 79-01A.
As the NRC review progresses, licensees which might have electrical overrice circuitry probleas are being advised not to use the override and to take coupensatory interim ueasures to minimize the problem.
In light of the information 9ainea curing our review of your submittal dated January o,1979, una the information cited above, we believe an interim CoGGitdent frou you is required at this time. This is the case, even though you have reported no purging with primary system aoove 300 psig since you have not specifically addressed ventilation.
For your use, we have provided as an attachment an interim NRC staff
~
position.
In accition, our recently developed "Guiaelines for Demonstration of Operability of Purge and Vent Valves" were provided by separate letter to licensees of each operating reactor. This letter in no way relaxes any existing licensing requirements for your facility.
Because of the potential auverse effects on the puolic health and safety which could result frou the postulated, D8A-LOCA while operating with open pur9e or vent valves, we Delieve your pronpt response to this letter is requirea.
In accordance with 10 CFR 50.54(f), you are requested 1354 048
Mr. Robert H. Groce
' October 23, 1979 to inform us in writing within 45 days of receipt of this letter of your commitment to operate in conformance with the enclosed interim position and to provide us with infonnation which demonstrates that you have initiated the purge and vent valve operability verification on an expedited basis. The information provided in your response will enable us to determine whether or not your license to operate Yankee Rowe should oe modified, suspended, or revoked.
Sincerely,
.i www i u y%
Dennis L. Ziema;, Chief Operating Reactors Branch #2 Division of Operating Reactors
Enclosure:
Interim Position for Containment Purge and Vent Valve Operation cc: w/ enclosure See next page 13So4 049
Mr. Robert H. Groce October 23, 1979 L
cc w/ enclosure:
Mr. Lawrence E. Minnick, President Yankee Atomic Electric Company 20 Turnpike Road Westboro, Massachusetts 01581 Greenfield Comunity College 1 College Drive Greenfield, Massachusetts 01301 1354 050
INTERIM POSITION'FOR CONTAINTENT PURGE AND VENT VALVE OPERATION PENDING RESOLUTION OF ISOLATION VALVE OPERABILITY Once the conditions listed below are met, restrictions on use of the containment purge anc vent system isolation valves will be revised based on our review of your responses to the November 1978 letter justifying your proposed operational mode. The revised restrictions can be established separately for each system.
1.
Whenever the containment integrity is required, emphasis should be placed on operating the containment in a passive mode as much as possible ano on limiting all purging and venting times to as low as achievable.
To justify venting or purging, there must be an established need to improve working conditions to perform a safety related surveillance or safety related maintenance procedure.
(Examples of improved working conditions would include deinerting, reducing temperature *, huridity*,
and airborne activity sufficiently to pennit efficient perfomance or to significantly reduce occupational radiation exposures), and 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 contdinment purge ana venting operations are operable under the uost severe oesi n Dasis accident flow condition loading and can 3
close within the time limit stated in your Technical Specifications, design criteria or operating procedures. The operability of butter-fly valves may, on an interim basis, be demonstrated by limiting the valve to be no more tnan 30 to 50 open (90' being full open). The maxiuun opening shall be determined in consultation with the valve supplier. The valve opening must be such that the critical valve parts will not be damaged by DBA-LOCA loaas and that the valve will tend to close when the fluid dynauic forces are introduced, and b.
riodifications, 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.
- Only where ter.'perature and humidity controls are not in the present design.
1354 051
_