ML19326C320
| ML19326C320 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/07/1977 |
| From: | Desiree Davis Office of Nuclear Reactor Regulation |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 8004220872 | |
| Download: ML19326C320 (3) | |
Text
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( j d-ev n NOV 0 71977 Docket r.
50-313j w.
Arkansas Power & Light Conpany f.TTil:
Mr. Willian Cavanauqh, III Executive Director, Generation T
NT CONTAINS
[,
and Construction
' HIS DOCUME T
b P0OR QUAUTY PAGES Lithe c
Art; ansa s 72202 Gentlenen:
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The ERC staff has conpleted a prelinin6ry review of the overpressure p~
protection systen for Arkansas Euclear One, Unit 1 ( Ai!0-1). 1:e heve tound tnat the syster currently installed, in combination with the i.
proposed changes, does not rect all the criteria estsblished by the GC.
Your proposed systen maintains a cas islanket or bubble in the pres-surizer at all times, in conjunction with a sinole 1cu pressure set-point power-operated relief valve (PORV).
This cesign nas certain advantages over other concepts tiocause failure of an operator to ranually enable the low pressure setpcint of the relief valve does not totally ceteat protection against a pressure transient. The staff hcs concluded that your proposed systen ac'ecuately acccmciates all nostuleted overpressure transients with the excestion of en inaavertent initiation of sc#ety injection by the high pressure in-jection (HPI) punp.
Llased en your analyses we have identifind HPI as tne liniting rass additian everpressure trarsier.t. Operation of the RPI purp, which ir, capable of delivering fica accinst full systcu operating pressure, is remired whenever a reactor coolant pump is in eneration. Since the discharge of the UPI pur.p is isolated fron the reactor coolant syster by a sin-le injection valve, a single errar or ecuipnent failure could open the injection valve and initiate a pressure increase in tN crimary systen.
If failure of the singic lw setpoint pos ce orcratec relief valve is then 4ssumed as the single failure following initiation of the event, your analysis sho'es that operatcr j
action is requird uitnin five r.inutes to r.'aintcin prinary system
- rcssure b?lov f.prencix C licits. This is not in accordece e.itu 43 d.
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uRC criteria for operator action chich crohibits onerator inter-g lq vention for te.c ninutes.
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8004220) 1.
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Arkansas Power & Light Co. -
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W5-dE Since your proposed systen does not fully satisfy our established criteria, we require that you propose systen rodifications that will provide overpressure protection in full comforrance with NRC criteria, and that you provide a schedule and a value-impact assessment to nake all necessary hardware changes.
It is also the NRC position that to assure proper alignaent of the overpressure protection systen during plant cooldown, an enabling alarm nust be provided which nonitors the systen enabling switch and the position of the isolation valve upstrean of the PORY.
In addition to the itens discussed above, the staff has identified several concerns relataa to maintenance and HPI testing for the currently proposed system.
If the relief valve requires pain-tenance, the upstream isolation valve vould need to be closed, thereby renoving the single relief valve fron service. Therefore the staff will require technical specifications which stipulate that when the reactor vessel temperature is below the ninimum value for which the vessel can be fully pressurized the PORY may be rencved frca service for o short period of tire only if: (1) charging pumps are out of service and all liPI injection valves are closed and power renoved, or (2) the vessel head is rersoved. Regarding liPI testing, the staff will require that your procedures state that the i!PI valve be allcwed to be cycled only i f all llPI pumps are out of service, or vessel tenperature is above the niniren value for ubich the vessel ten be fully pressurized, or the reactor vessel head is renoved.
ue still require that your technical specifications identify the system enauling te:.:pera ture and the PaiY setroint.
In addition, you should propose specifications related to systen testing.
These naintenance and testing restrictions should be exanined to assure compatiotlity with present technical specification rnouire-reents regarding the operability and periodic tssting of ECC and energency boration systens. Also, since the inpact of the proposed technical specifications will be considered by the stoff in de-ternining the acceptability of the proposed overcressure nitigatiny systen, you shuld nrovide a thorough evaluation of the ofrect of tnese r:aintemnce and testing remiirenents on the susceptibility of the reactor coolcnt syster to a pressure transient.
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3-Arkansas Power & Light Conpany m
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You strould provide the above reouested infamation and the proposed technical specifications within 45 days of receipt of this letter.
The follouing additional-infomation, which was reopested f. oil your staff during a telephone conversation on June 30, 1977, should also be provided within 45 days of receipt of this letter:
L-n (1) Assur.ptions made regarding stean bubble collapse.
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(2) Verification of nurrber of HPI:pumpstassumed..in.
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Eperation on F1stre A-1 of AP&L fiarch 24, 1977
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letter.
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(3) Result of AP&L investigation into lowering
=g shutdown pressurizer level to less than 180".
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(4) t. ascription of HPI test referred to in response to Ouestion !!o. 6. APbl liarch 2.4, 1977 Letter.
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(5) Dir,cussion of precability of operator error with JL regard to hPI test (response to Question l'o. 6, AP&L liarch 24, 1977 letter).
(6) Description of administrative controls to assurc HPI trains (punps and/or valves) are " racked out" when required and are " racked in" only when authorized and then only for specific, controlled purposes,
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such as stort-up or MPI test.
Ve consider your present overpressure,nitigatino systen to provirle g
ader,vate protection until all nodifications are complete, even
- .ss thcogh the present syste 1 does not neet all of the MC criteria.
[..
-DISTRIBUTION:
Sincerely, Docket DSnaide'r fiRC PDR GZech b
DEisenhut_
j VStello TAbernathy.
KGoller JBuchanan Don K. Davis, Acting Chief
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