ML20211J667

Proposed Tech Specs Re Primary Containment Isolation Valves, Per 10CFR50.92 Requirements

ML20211J667
Person / Time
Site:	Cooper
Issue date:	11/06/1986
From:	Kuncl L NEBRASKA PUBLIC POWER DISTRICT
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ML20211J660	List: ML20211J654 ML20211J667
References
NUDOCS 8611110212
Download: ML20211J667 (3)

Text

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Attcchmint 1 Revised Technical Specifications to

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. Change the Normal Position of Primary Containment Isolation Valves Revised.Pages: 168 Table 3.7.1 of the CNS ' Technical Specifications states that the normal position of the main steam line drain isolation valves MS-M0-74 and MS-MO-77 is. closed. In order to provide continuous drain paths for the UPCI and RCIC steam lines from points upstream of the respective isolation valves, it has been station practice to operate with these valves-open. Operation with this valve alignment prevents the buildup of water in the.HPCI and RCIC steam lines when either of these systems isolates. This reduces the probability of damage to the HPCI and RCIC turbines.

These two valves are redundant. Class A primary containment isolation valves located in series on the 3 inch main steam 'line drain- lines. Both valves close' automatically on the standard isolation signals. MS-M0-74 is located inside and MS-MO-77 outside containment. Their power supplies are independent and together they satisfy the requirements of GDC-55. Operation with these valves open will increase the reliability of the HPCI & RCIC systems and still satisfy all the applicable primary containment isolation criteria.

Evaluation of this Revision witih Respect to 10CFR50.92 A. The enclosed Technical Specification change is judged to involve no significant hazards based on the following:

1. Does the proposed license amendment involve a significant increase in the probability or consequences of an accident previously evaluated?'

Evaluation:

The failure probability of a component to operate when required is obviously. higher than the failure probability of the same component in the passive. mode. Operation with these valves open vs. closed will obviously result in a small increase in probability of failure to isolate the main steam drain lines in event of a pipe break.

These are redundant, safety grade valves on a 3 inch line. The bases to the Technical Specifications states that_tpe current probability that a line will not isolate is 1.1 x 10 per demand.

The increase due to adding one line to the list of those which require valve closure to isolate is not significant.

2. Does the proposed license amendment create the possibility for a new or different kind of accident fro.m any accident previously evaluated?

Evaluation:

Failure of these isolation valves to close when required would be no different from failure of any other set of redundant isolation valves to close when required. This change will not create the possibility for a new or different kind of accident from any accident previously evaluated.

8611110212 DR 861106 ADOCK 05000298

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3. ~Does the proposed amendment involve a significant reduction in a margin of safety?

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Evaluation:

No operating limits or trip set points are'aff'ected by this. change.

There is no change in the margin of safety. ,

B. Additional basis for - proposed no significant hazards consideration determination:

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The commission has provided guidance concerning the application'< of the standards for determining whether a significant hazards consideration exists by providing certain examples (48CFR14870).

The examples include: (vi) A change which either. may result in some increase to.the probability -or consequences .of a previously analyzed accident or may reduce in some way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan. . ." It is the District's belief that the proposed change is encompassed by the above example.

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TABLE 3.7.1.(Page 1)~

PRIMARY CONTAINMENT ISOLATION VALVES Number of Power . Maximum -Action On

. Operated Valves Operating Normal .

. Initiating Valve & Steam Inboard Outboard- Time'(Sec) (1) Position (2) Signal'(3)'

Main Steam Isolation Valves MS-AO A,B,C, & D . 4 31< T<5 0 GC MS-AO A,B,C, & D 4 3<T<5 0 'CC Drywell Floor Drain Iso. Valves 1 1 15 0 GC.

RW-AO-82, RW-AC-83 Drywell Equipment Drain 1 1 15 0 GC-

' . Iso. Valves RW-AO-94, RW-AO-95 .

Hain Steam Line Drain 1 1 30 0 GC Valves MS-MO-74, MS-MO-77 l Reactor Vater Sample Valves l' 1, 15- 0 GC KRV-740AV, RRV-741AV Reactor Water Cleanup System 1 1 60 0 GC Iso. Valves RWCU-MO-15, RWCU-MO-18 RilR Reactor.Ilead Spray 1 l' 60 C SC lso. Valves kilR-MO-32, RiiR-MO-33 -

RilR Suction Cooling Iso. 1 .l' 40 C RSC ~

Valve-RilR-MO-17, RilR-MO-18 kilR Discharge to Radwaste 1 1 20 C SC' Iso. Valves RilR-MO-57, RiiR-MO-67 Suppression Chamber Purge & 2 15 C SC Vent PC-245AV, PC-230MV Suppression. Chamber N '

9 Supply 2 15 C SC PC-237AV, PC-233MV

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