IR 05000344/1986032

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

ML20209C238
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
ML20209B928	List: IR 05000344/1986032 ML20209B923
References
50-344-86-32-01, 50-344-86-32-1, TAC-61523, NUDOCS 8609080422
Download: ML20209C238 (7)

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.U.'.S. NUCLEAR REGULATORY COMMISSION REGIO 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 9/204 Facility Name: Trojan

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Inspection at: Portland, Oregon and Rainier, Oregon Inspection conducted: . August 4 - 14, 1986 Inspectors: N- - " : N#

S. A. Richards, Chief f Date Signed

_ Engineering Section .

Approved.By: % Y# "

M. M. Mendonca, Chief Date Signed ,

Reactor Projects Section 1

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Summary:

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

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Areas' Inspected: Special inspection of licensee identified deficiencies with c the operation of the~ residual heat removal (RHR)'syst'em concerning , ,

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environmental qualification of valves and potential'exces_sive' flow situations during the recirculation mode. Followup of Licensee Event Report 86-03 was ,

-alse, conducte .

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

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

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inoperability of an RHR system flowpath.

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8609030422 860820 PDR ADOCK 05000344 O PDR

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% .1. '? Persons Contacted

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.- .W.~ S. Orser," Plant Gene'ral Managerf "

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-*R..L. St'eele,sManagers Nuclear. Plan't= Engineering-

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. *G.TA.'Zimmerman,lManager,LNuclear Regulation Branch 1

. *C. M. Dieterle, Supervising Engineer, Systems Engineering Group '

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G. R. Alberthal, Nuclear Engineer

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E..L. Davis, Supervising Engin'e'er, Electrical' Engineering Branch

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} * Denotes those. attending the exit interview on August' 14, 198 . 2i Residual Heat Remov'al System Deficiencies on Pump Excessive Flow and.

[ Environmental Qualification of Valves , 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

, associated flow paths, comprise the pumped flow portion of.the i-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 head pumps. ECCS is divided into two trains with each train containing one of each type of prop. Following a postulated loss of coolant 1 accident (LOCA),'both trains of ECCS are. automatically

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. initiated by the plant p'rotection 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 *

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

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

'RHR pumpr take_ suction from the containment recirculation sump'. . The i discharge of the RHR pumps is aligned to inject intorthe RCS cold '

F s legs and to provide water to the suction of the SIPS'and the CCP When the ECCS is aligned for cold leg recirculation as described j 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 operator '

I realign the system for hot leg recirculatio In this mode of l

operation, the RKR 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

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

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

The ECCS'is designed to complete its safety function-coincident with-j a single active failure during the injection mode, or a single

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active or passive failure during the recirculation mode. A passive '

failure is defined as a system leak of less than 50 gallons'per l minute (gpm) for 30 minutes. The single failure criteria are '

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

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Report (FSAR). i

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, Because of concerns previously raised regarding the correct

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alignment of various valves associated with the RHR system during cold. leg injection, the licensee commenced a review of the operation-of.the system. 'The licensee's review identified:the following two-

'_ potential problem area '

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The failure of one'RHR pump when in the recirculation mode

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could. result in the remaining RHR pump exceeding the pump's design flow capacity. This could occur during either hot or cold. leg' recirculation. Failure of the remaining RHR pump due to operating beyond the pump's design could result in the plant being incapable of recirculating ~the water in the containment recirculation sump for. reactor core decay heat remova Eleven valves in the ECCS system associated witih alignment of , ,

the system for recirculation were erroneously exempted by the licensee from environmental qualification (EQ). The subject of ,

valve'EQ is discussed in detail in paragraph 3 of this repor Residual Heat' Removal System Pump Excessive Flow The licensee conducted a detailed review of the. potential for exceeding design capacity of an RHR pump. The Nuclear Steam Supply System vendor, Westinghouse Corporation, was contacted for assistance with this effort. The licensee concluded the followin Oi -

During cold. leg recirculation with only~one RHR pump operating,

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< the resultant flow rate was calculated to be 5850 gpm to 5950 gpm, depending on the position of-valves MO 8716 A/B. The

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

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evaluation of the.effect of the excessive flow rate concluded . ,

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that the pump motor would probably operate indefinitely witho'ut' " fi significant adver:,e consequences, however, the pump impeller', '

under the worst case conditions, would experience mild ,

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- r - , cavitation due to.an approximate 10 foot deficiency,in net,

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

• 3 , ', time could significantly degrade the operation'of the pum '

, However, the control room operators have direct = indication of *

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RHR flow and indication of pump motor current. Pump cavitation:  ;

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normally causes motor current to oscillate. Therefore, -

operations personnel would have two indications of an abnormal

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!,i condition. Additionally, the licensee's analysis (4 conservatively assumes no subcooling of the water in the o"

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

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. serve to reduce or eliminate the pump cavitatio i !: '

.i During hot leg recirculation with one RHR pump operating, the

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resultant flow rate was calculated to be approximately 6500 8pm. The licensee again stated that the pump motor would probably 'not be adversely effected, however, a 24 foot NPSH

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deficiency would exist with'the potential for more severe impeller cavitation. The pump vendor has been requested by the licensee to. evaluate pump performan'ce at this' flow rat l -

The system description provided to the licensee by Westinghouse L -

when the plant commenced initial operation did not addres limiting RHR pump flow with only one pump in operation. The

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preoperational telt~of the RHR system apparently. recognized the prcblem in that during the test, the RHR heat exchanger discharge valves'were required to be throttled to limit total pump flow, however, action was apparently not initiated at that

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time to prevent the potential for excessive flow when the plant entered operatio , As corrective action for this concern, the licensee has initiated the following.

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Emergency procedures for cold leg and hot leg recirculation were revised such that the RHR pump discharges are now isolated-p from each other at the suction to the SIPS. This action prevents the conditions necessary for an excessive flow

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

[ after the recirculation mode has been entered under the new

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

~CCPs to also' fail due to a lack of pump suction pressur Westinghouse has concurred that the licensee's action is acceptable and that if necessary, one SIP and one RHR pump provide adequate flow for decay heat removal during the recirculation mode.

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The licensee notified the NRC headquarters duty officer of the-

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potential problem via the ENS telephone after their initial evaluation and provided a followup notification via the ENS after a more detailed review was completed, i -

The licensee has discuscad with Westinghouse the potential generic 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 l conditions of RHR pumps at ot*er reactor sites. The licensee has.also questioned Westinghouse concerning why Westinghouse

was apparently aware of a similar problem at the Seabrook plant i and had not informed the Trojan plant of the situatio The Final Safety Analysis Report will be updated to reflect

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changes made in the operation of the ECCS. The licensee is continuing their review of the design and operation of the.RHR syste No violations or deviations were identified.

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' Environmental Qualification of-Valves Ae discussed in paragraph 2, through their review of the operation of,the RHR system the licensee identified that eleven valves associated with the recirculation mode of ECCS operation were not "

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environmentally qu'alified for a high radiation environment. The valves concerned.are as follows:

- MO 8804 A RHR discharge to CCP suction

- MO 8804 B RHR discharge to SIP: suction

- M0;8807 A/B & MO 8924 SIP suction to CCP suction cross-connect

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- MO 8809 A/B , 'RHR discharge valves to the RCS cold legs

- MO 8923 A/B -

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SIP suction cross-connect valves

- M0 S716 A/B'< RHR pump discharge cross-connect valves When the environmental qualification of these valves was originally censidered in 1981, the licensee concluded that the valves were exempt from environmental qualification as documented in licensee memorandum JWL-659-81M dated-September 21, 1981. For valves MO 8809 A/B-and MO 8716,A/B,,the licensee recognized that the operation of these' valves was needed to place RHR in hot leg recirculation.

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l' However, theilicensee ' concluded that- SIP injection to the hot legs

,alone would provide ' adequate h,ot leg injection and therefore .

realignmentsef. valves:M0;8809'~A/B and,MO 8716 A/B in the recirculation mode would'not be required. The valves would then not-require environmental 1 qualification because their required position

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would be established-prior to receiving any significant radiation dose. The' licensee apparently failed to translate this conclusion into changes:in their'energency. procedures. As such,.the procedures

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I coatinued to require repositioning of MO 8809 A/B and MO 8716.A/B

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whenfswitching'to hotsleg recirculation. Failure of the'e s valves,

- during;the switchover could result in excessive flow through an RHR pump or' isolation of all RHR' direct. injection path One of the design criteria for the system is the ability.to isolate a passive failure after the recirculation mode is entered...The ' -

licensee's 1981 evaluation for valves MO 8804 A/B, MO 8807 A/B, MO 8923 A/B and MO 8924 concluded that these valves were esempt from

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environr. ental qualification because they would complete their safety function, i.e., be properly positioned,' prior to receiving a significant radiation dose. At the time the licensee apparently failed to consider the need for these valves to function after entry

- into the recirculation mode for the purpose of passive failure isolatio The licensee documented these environmental qualification problems with nonconformance report number 86-132 on July 9, 1986. An evaluation was performed to determine if interim operation of the valves was justified. The evaluation found that the valve components were all qualified under existing test reports except for the motor brakes and the internal wiring. The licensee concluded that the wiring could be analytically qualified for 12 years and was therefore-

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acceptable for interim use. With regard to the~ motor brake, the licensee ' concluded that.the only brake component of concern from a materials standpoint was the brake rubber pad. .The motor brake rubber pad was calculated'to suffer a'30-40 percent. reduction in compression set due,to_ radiation effects. .The licensee evaluation '

concluded that the brake rubber pad would have to completely disintegrate for-the brake to fail and therefore found the valves acceptable for interim use based on their consideration that.the.-

valves would likely function during an accident if called upon to do s For permsnent corrective action, the licensee intends to fully ,

qualify these valves either by testing, modification, . or replacement, during the 1987 refueling outage. The licensee is also reconsidering the exemption from environmental qualification of-various other valves in other plant systems.

E With regard to the original evaluation, the licensee has recognized "d that a proper design review was apoarently not performed.

i Nonconforming activity report number H86-99 has been initiated to

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document the deficiency. The licensee is reviewing-the

circumstances surrounding the original evaluation to ensure that

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present, design review methods would provide a greater. assurance that this type of error would be quickly identified and corrected.

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3 Additionally, the licensee has identified several discrepancies i between.the Westinghouse RHR system description, the description of

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! RHR system operation contained in the Final Safety Analysis Report ( (FSAR), and thejlicensee's emergency procedures. jThe licensee has

! revised their emergency procedures to account for the concerns of ,

excessive RHR flow (discussed in. paragraph-2). Westinghouse has concurred that the procedures, as revised, operate the ECCS in a manner which results in the accomplishment _of the. design safety ,

i function. The licensee is performing a detailed review of the

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appropriate FSAR sections'and will revise the FSAR as necessary to correctly describe the operation of the ECCS.

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(. The inspector concluded that the licensee clearly recognized in 1981 l~ that components of the valves in question were not environmentally

qualified and that these valves were mistakenly exempted from l

environmental qualification due to errors in the licensee's evaluation. Futher, the licensee recognized that a more rigorous

> review of the initial evaluation may have identified the error. The

licensee's failure to environmentally qualify,these valves is an apparent violation of 10 CFR 50.49 (344/86-32-01).

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! Residual Heat Removal System Injection Flow Paths i

As discussed in paragraph 8 of Inspection Report 50-344/86-10, the licensee had shut. valve MO 8809 A for a period of one. hour and ten j minutes on March 31, 1986, while performing preventative maintenance on

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the valve. The plant was in mode 1 operation at 100% power at the time.

,. This was carried as an unresolved item 8'6-10-0 The licensee documented j this in Licensee Event Report 86-03.

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S Licensee personnel had erroneously considered the cold leg injection paths of the residual. heat removal (RHR) system as segregated by trai i Factors which apparently contributed to this incorrect understanding included the following:

- The technical specification requirement for two independent ECCS subsystems can be read to mean that the system has two independent flow paths, when actually several sections of the ECCS flow paths are common to both subsystem During cold leg recirculation, the discharges of the RHR pumps are-required to be split by shutting the cross-connect valve The licensee's emergency procedures and training material previously stated that the RHR discharges were to be split during cold leg injection if both RHR pumps started. This action, however, was-in conflict with the Westinghouse system description. The inspector was unable to ascertain the origin of this mode of operatio Because each train of RHR must be capable of discharging to the reactor coolant system via all four cold leg injcetion points during mode 1 operation to be operable, the licensee rendered both trains of RHR-inoperable by shutting valve MO 8809 A. The licensee apparently violated technical specification Limiting Condition for Operation (LCO) 3.5.2 and LCO 3.0.3 in that the plant was not placed in at.least hot standby within one hour of exceeding the action statement of LCO 3.5.2. (344/86-32-02).

This closes unre* solved item 86-10-0 . Exit Interview The inspector met with the licensee representatives denoted in paragraph 1 at the conclusion of the inspection. During this meeting the inspector summarized the scope and findings of the inspectio .

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