ML17285A782

Safety Evaluation Supporting Amend 74 to License NPF-21

ML17285A782
Person / Time
Site:	Columbia
Issue date:	10/03/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML17285A781	List: ML17285A780 ML17285A782 ML17285A783
References
NUDOCS 8910180223
Download: ML17285A782 (8)

Text

~gag RECy~

po pg~

qO

+a**+

UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 74TO FACILITY OPERATING LICENSE NO. NPF-21 WASHINGTON PUBLIC POWER SUPPLY SYSTEM NUCLEAR PROJECT NO.

2 DOCKET NO. 50-397

1.0 INTRODUCTION

By letter dated October 24, 1988, Washington Public Power Supply System proposed certain changes to Technical Specification Section 3/4.3.7 "Radiation Monitoring Instrumentation,"

including Table 3.3.7.1-1, Radia-tion Monitoring Instrumentation,"

by removing reference to "trips" actuated by the instrumentation.

Specifically, in accordance with the requirements of this specification, main control room ventilation radiation monitors should alarm in the control room during high radiation levels and also should trip air system intake valves to cause air to be drawn from a different point.

The amendment would allow continued operation without the automatic trip capability.

The alarm functions would be retained and the air intakes would be realigned manually.

Action 70(a) in the table is to be revised to show that the licensee would manually isolate a remote air intake when a monitor associated with that intake is inoperable.

This would achieve the same objective as the trip mechanism for the case of one inoperable monitor.

The associated bases would be changed to be consistent with the specifications.

The licensee stated that the change, which would delete the trip function, is necessary because under the existing specifications should a

LOCA occur, then a single failure (for example a short closing an isolation valve) could result in both remote air intakes remaining closed.

Such a sequence of events would force the control room ventilation system into the recir-culation mode resulting in higher control room in-leakage rates from the reduction in control room pressure.

This increased in-leakage in turn could cause excessive radiation exposure to the control room personnel.

To avoid this situation the licensee has already replaced the motor operators on the controlled intake valves with manual operators.

Following the deletion of the automatic trip function for these valves, the licensee has been operating the control room ventilation system in the pressuri-zation mode in accordance with requirements in Action 70(b) in the Technical Specification.

8910180223 891003 PDR ADDCN 05000397 P

PNU

P

'i

~ I

'I

'l C

l)

~

~ ~

l

) r'

) ~ 1

~

1

~

r ~

I J

~"

I l

'I t l

~

r I

l tt ~

1 lr

~

t I t

I

~

I ~

n I

t

).1 ~

~

1

~ )

~

I r'

l 1

t np,t n)

~

1 I II PP

~ 1

~

~

~ r

2.0 EVALUATION The control room habitability system protects operators from airborne radioactivity.

The control room HVAC system is arranged with one normal air intake and two remote air intakes that function during accident conditions.

Each remote air intake line has two radiation monitors and two electro-hydraulic valves in series which are normally closed and powered from different vital buses.

The normal air intake has two isolation valves which are normally open, but which close on an F, A, or Z signal (high drywell-pressure, low RFV level or high radiation, any of which could be indicative of a LOCA in progress).

An FAZ signal also causes the isolation valves in both remote air intakes to open, the emergency supply fans to start, and the control room exhaust fan to trip, and places the control room HVAC.in the pressurization mode, providing filtered air through filtration units.

When the radiation monitors in one remote intake line sense high radiation (after initial opening of the valves on an FAZ signal),

they provide an alarm function and cause the isolation valves in that line to close, but the control room remains in the pressurization mode through the other remote air intake.

On September 2, 1988, engineers from Generation Engineering discovered that the control room heating, ventilation, and air conditioning (HVAC) system was susceptible to a single failure for which WNP-2 was not analyzed (See Licensee Event Report 88-31).

The reactor was shutdown at the time and remained shutdown until the problem was resolved on September 5.

Should a

LOCA have occurred, a single failure could have resulted in both remote intakes remaining closed.

For example, a "hot short" could close an intake valve in one of the remote intakes while the opposite intake was isolated as a result of the LOCA release.

This event would have forced the control room ventilation system into the "recirculation" mode and caused higher control room in-leakage rates from the loss of control room pressure.

This in-leakage could have caused excessive radiation exposure to the control room personnel.

To avoid this situation, the Supply System replaced the motor operators on the remote air intake valves with manual operators.

In the event of a

LOCA, an operator would be dispatched to close the appropriate set of isolation valves for an alarming condition on the radiation monitors for a given remote air intake.

Procedures were revised to reflect this modification and a dry run was conducted to ensure that this could be accomplished in a timely manner.

Operation of the control room emergency filtration system has been maintained in the pressurization mode in accordance with ACTION 70(a) in the Technical Specifications.

V I

With the approval of this Technical Specification change request, operation in the pressurized mode would not be required.

Normal plant lineup would be such that the two remote intakes will be administratively controlled open with normal control room intake through those intakes and the normal intake.

Occasionally one remote intake might be isolated to facilitate maintenance or other activities.

The 750 cfm exhaust fan would remain operational.

In the event of an FAZ signal, the normal intake will close, the 750 cfm exhaust will de-energize, and the emergency filters will automatically be placed in service.

These FAZ initiated actions are per the original plant design and were not altered.

After the FAZ initiation, either intake can be manually isolated locally, given a change in radiological conditions as sensed by the original radiation elements.

This is similar to the original design concept that manually repositioned a remote air intake valve open following an FAZ condition and provided a single isolation given changing radiological conditions.

Evaluations and actual plant walkthrough demonstration have verified that the manual action can be accomplished well within the time frame evaluated in Section 6.4.4 of the WNP-2 FSAR.

(The FSAR evaluated the exposure which would occur with the alternate remote intake valve which is in the path of the plume stuck in the open position for three hours.

The licensee demonstrated that manual action would take less than 20 minutes, including the donning of protective clothing and accessing the valve area.)

Additionally, with both intakes normally open versus one as discussed in the FSAR analysis, the dose to the operators is diluted during the three-hour period and consequently is bounded conserva-tively by the analysis provided in the FSAR.

The purge valve also functions similarly and is opened depending on the position of its associated remote intake isolation valve.

The changes ensure that the emergency filtration system remains in service and that no single component failure can prevent operator action from establishing a suitable source of air for the pressurization mode.

Further, the changes retain the indication function of the remote radia-tion monitors.

When the trip function was eliminated from the instrumentation, the licensee initiated and has maintained the operation of the control room emergency filtration system in the pressurization mode of operation as required by action statement 70 of Table 3.3.7.1-1.

The proposed change to Table 3.3.7.1-1 of the Technical Specification would delete reference to the trip function and would require manual isolation of an air intake associated with an inoperable radiation monitor in lieu of manually tripping the inoperable channel.

Without the trip function as a requirement, the instrumentation would be operable and the licensee would no longer need to operate the plant in the action statement for this function.

/ g ~

s I

I I I

~

v I I,

<< I I

I I I

,s(

=vt 's

I lt

~ ~ '1 Jl I ( ~

~.

~ 's, I s

~

I

~

I l I(I

~. hi]

=I

~ <<IVI",

I

~

I (s'.

ll

~ I

~

,s'I I ~ I's ss

~

l

'I'

~

~

s

~

I

~

I tl I 'I IP I s

~

~

's I ( r s

't (

~

~

C(II

~

I

~

~

/

1' I

~

I

~.

~ s I

il I ts

~

r

~

I I>>

I

~

1'I

Is ~ L I

I (,

~ 't I

I I

s II' I

s (I sr 1 I (r ~

t

~

~

I I'

I

~

(

I t

~

(

~ < I I

I

~

r ~

~

l s

rs

~

~

=

I I

s t,'s,

~

I

~

>>t

~ I I I

I(

~ ('

I,

~ I

'f< < I II I g

s ~

~

~

(. "I

~ I I I

~

I

~

~

~

~

(

I I

I II Is

~

I

~ 'l I I

~

I I

.1 I

I s "r I

(.s,s,s 1

I I s'

"1.

~

I

~

(

ts j,s

~ ~ I

'<< I 3.0 Since the alarms are retained and timely operator action can be taken, the staff finds deletion of the trip function requirement from the technical specifications acceptable.

As indicated by letter dated November 30,,1988 from R. Samworth, NRC, to G.

C. Sorensen, WPPSS, the proposed addition of the footnote on page 3/4 3-58 and the proposed changes to ACTION statement 70 on page 3/4 3-59 specifying times to restore the monitors to operable status did not (I) indicate any need for these

changes, (2) present a safety analysis or (3) provide a "no significant hazards consideration analysis" addressing these changes.

Accordingly, no review was performed and these proposed changes are being denied.

ENVIRONMENTAL CONSIDERATION 4.0 This amendment involves a change to requirements with respect to the installation and use of a faci lity component located within the restricted area as defined in 10 CFR Part 20.

The staff has determined that this amendment involves no significant increase in the amounts, and no signi-ficant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.

The Commission has previously issued a

proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding.

Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b),

no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.

CONTACT WITH STATE OFFICIAL 5.0 The Commission made a proposed determination that the amendment involves no significant hazards consideration and consulted with the State of Washington.

No public comments were received, and the State of Washington did not have any comment.

CONCLUSION We have concluded, based on the considerations discussed above, that:

(I) there is reasonable assurance that the health and safety of the public wi 11 not be endangered by operation in the proposed

manner, and (2) such activities will be conducted in compliance with the Commission's regula-tions and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor:

R. Samworth Dated:

October 3, 1989

1 I

l,