ML20203L761

Insp Rept 50-344/86-32 on 860804-14.Violations Noted: Failure to Environmentally Qualify 11 safety-related Valves & RHR Sys Flowpath Inoperable

ML20203L761
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	08/15/1986
From:	Mendonca M, Richards S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
Shared Package
ML20203L752	List: ML20203L750 ML20203L761
References
50-344-86-32, NUDOCS 8608290156
Download: ML20203L761 (4)

See also: IR 05000344/1986032

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U. S. NUCLEAR REGULATORY COMMISSION

REGION V

Report No. 50-344/86-32

Docket No. 50-344

License No. NPF-1 ,

Licensee: Portland General Electric Company

121 S. W. Salmon Street

Portland, Oregon 97204

Facility Name: Trojan

Inspection at: Portland, Oregon and Rainier, Oregon

Inspection conducted: August 4 - 14, 1986

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Inspectors: N #"

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S. A. Richards, Chief Date Signed

Engineering Section

Approved By:  %

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M. M. Mendonca, Chief Date Signed

Reactor Projects Section 1

Summary:

Inspection on August 4 - 14, 1986 (Report 50-344/86-32)

Areas Inspected: Special inspec' tion of licensee identified deficiencies with *

the operation of the residual heat removal (RHR) system concerning

environmental qualification of valves and potential excessive flow situations

during the recirculation mode. Followup of Licensee Event Report 86-03 was

also conducted. I

Results: Two violations were identified. These violations involved: 1) the

failure to environmentally qualify eleven safety-related valves and 2) the

inoperability of an RHR system flowpath.

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DETAILS

1. Persons Contacted

W. S. Orser, Plant General Manager

• R. L. Steele, Manager, Nuclear Plant Engineering

• G. A. Zimmerman, Manager, Nuclear Regulation Branch

• C. M. Dieterle, Supervising Engineer, Systems Engineering Group

G. R. Alberthal, Nuclear Engineer

E. L. Davis, Supervising Engineer, Electrical Engineering Branch

• Denotes those attending the exit ictarview on August 14, 1986.

2. Residual Heat Remcval System Deficiem ies on Pump Excessive Flow and

Environmental Qualification of Valver

a. Background

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The two residual heat removal (RHR) pumps, the two safety injection

pumps (SIP), the two centrifugal charging pumps (CCP), and their

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associated flow paths, comprise the pumped flow portion of the

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emergency core cooling system (ECCS). The RHR pumps are high flow,

low head pumps, the SIPS are medium head pumps and the CCPs are high

i head pumps. ECCS is divided into two trains with each train

containing one of each type of pump. Following a postulated loss of

coolant accident (LOCA), both trains of ECCS are automatically

initiated by the plint protection system, such that each pump takes

a suction from the refueling water storage tank (RWST) and injects

borated water into the reactor coolant system (RCS) via cold leg

injection flow paths. , Prior to depleting the water volume of the

RWST, the RHR pumps stop automatically. The control room operators

then realign the ECCS for the recirculation mode. In this mode, the

RHR pumps take suction from the containment recirculation sump. The

discharge of the RHR pumps is aligned to inject into the RCS cold

legs and to provide water to the suction of the SIPS and the CCPs. -

When the ECCS is aligned for cold leg recirculation as described

above, the discharge of both RHR pumps and the suction of all SIPS

and CCPs are cross-connected together. Approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after

aligning the system for cold leg recirculation, the operators

realign the system for hot leg recirculation. In this mode of

operation, the RHR injection to the RCS cold legs is isolated and an

injection path to two RCS hot legs is established such that both RHR

pumps are then injecting to the same hot legs via a common flow

path, in addition to providing water to the suction of the SIPS and

CCPs. The SIPS are also aligned to discharge to the RCS hot legs

via separate headers.

The ECCS is designed to complete its safety function coincident with

a single active failure during the injection mode, or a single

active or passive failure during the recirculation mode. A passive

failure is defined as a system leak of less than 50 gallons per

minute (gpm) for 30 minutes. The single failure criteria are

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discussed in detail in chapter 3 of the plant Final Safety Analysis

Report (FSAR).

l Because of concerns previously raised regarding the correct

alignment of various valves associated with the RER system during

cold leg injection, the licensee commenced a review of the operation

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of the system. The licensee's review identified the following two

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potential problem areas. ,

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The failure of one RHR pump when in the recirculation mode

could result in the remaining RHR pump exceeding the pump's

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design flow capacity. This could occur during either hot or

l cold leg recirculation. Failure of the remaining RHR pump due

to operating beyond the pump's design could result in the plant ,

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being incapable of recirculating the water in the containment

recirculation sump for reactor core decay heat removal.

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Eleven valves in the ECCS system associated with alignment of

the system for recirculation were erroneously exempted by the

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i . licensee from environmental qualification (EQ). The subject of

valve EQ is discussed in detail in paragraph 3 of this report.

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1 b. Residual Heat Removal System Pump Excessive Flow

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The licensee conducted a detailed review of the potential for

exceeding design capacity of an RHR pump. The Nuclect Steam Supply

i System vendor, Westinghouse Corporation, was contacted for

i assistance with this effort. The licensee concluded the following.

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During cold leg recirculation with only one RHR pump operating,

the resultant flow rate was calculated to be 5850 spa to 5950

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spm, depending on the position of valves MO 8716 A/B. The

! design flow rate for each RHR pump is 4500 gpm. A licensee

! evaluation of the effect of the excessive flow rate concluded ;

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that the pump motor would probably operate indefiritely without

significant adverse consequences, however, the pusp impeller,

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under the worst case conditions, would experience mild .

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cavitation due to an approximate 10 foot deficiency in net i

positive suction head (NPSH). Pump cavitation over a period of

j time could significantly degrade the operation of the pump.

However, the control room operators have direct indication of

RHR flow and indication of pump motor current. Pump cavitation

normally causes motor current to oscillate. Therefore,

operations personnel would have two indications of an abnormal

condition to direct their attention to the excessive flow

condition. Additionally, the licensee's analysis

j conservatively assumes no subcooling of the water in the

i containment sump. Any degree of subcooling of the water will

serve to reduce or eliminate the pump cavitation.

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- During hot les recirculation with one RHR pump operating. the ,

resultant flow rate wa's calculated to be approximately 6500

i spa. The licensee again stated that the pump motor would

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probably not be adversely effected, however, a 24 foot NPSH

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> deffciency would exist with the potential for more severe

impeller cavitation. The pump vendor has been requested by the

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licensee to evaluate pump performance at this flow rate.

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The system description provided to the licensee by Westinghouse

when the plant commenced initial operation did not address

limiting RHR pump flow with only one pump in operation. The

l preoperational test of the RHR system apparently recognized the

l problem in that during the test, the RHR heat exchanger

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discharge valves were required to be throttled to limit total

pump flow, however, action was apparently not initiated at that

j time to prevent the potential for excessive flow when the plant

j entered operation.

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} As corrective action for this concern, the licensee has initiated

l the following.

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Emergency procedures for cold leg and hot les recirculation

j _ were revised such that the RHR pump discharges are now isolated

i from each other at the suction to the SIPS. This action t

i prevents the conditions necessary for an excessive flow l

} condition from occurring, however, should the 'A' RHR pump fail

i after the recirculation mode has been entered under the new

l procedure, the potential then exists for the 'A' SIP and both

CCPn to also fail due to a lack of pump suction pressure.

i Westinghouse has concurred that the licensee's action is

I acceptable and that if necessary, one SIP and one RHR pump

j provide adequate flow for decay heat removal during the

i recirculation mode.

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! - The licensee natified the NRC headquarters duty officer of the

i potential probles.via the ENS telephone after their initial

evaluation and provided a followup notification via the ENS

j after a more detailed review was completed. i

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- The licensee has discussed with Westinghouse the potential .

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beneric concerns with the problem. It should be noted that the'

individual plant pipe layout can significantly change the

system flow characteristics and therefore the operating

conditions of RHR pumps at other reactor sites. The licensee

has also questioned Westinghouse concerning why Westinghouse

was apparently aware of a similar probles at the Seabrook plant ,

and had not informed the Trojan plant of the situation.

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- The Final Safety Analysis Report will be urJattd to reflect

j changes made in the operation of the ECCS.

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- The Iteensee is continuing their review of the design and

operation of the RHR system.  !

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j No violations or deviations were identified. [

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