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Insp Repts 50-498/90-28 & 50-499/90-28 on 900730-0808. Violations Noted.Major Areas Inspected:Onsite Followup of Two Events
	ML20059K943
Person / Time
Site:	South Texas
Issue date:	09/18/1990
From:	Joel Wiebe; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	;
Shared Package
ML20059K934	List: ML20059K932; ML20059K937; ML20059K943;
References
	50-498-90-28, 50-499-90-28, NUDOCS 9009250267
	Download: ML20059K943 (7)
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' APPENDIX B

U.S. NUCLEAR REGULATORY C0!HISSION

REGION IV

NRC Inspection Report: 50-498/90-28 Operating License: NPF-76

50-499/90-28 NPF-80

Dockets: 50-498

50-499

Licensee: Houston Lighting & Power Company (HL&P)

P.O. Box 1700

Houston, Texas 77251

Facility Name: South Texas Project (STP), Units 1 and 2

Inspection'At: STP, Matagorda County, Texas

Inspection Conducted: July 30 through August 8, 1990

Inspectors: J . I. Tapia, Senior Resident Inspector, Project Section D

Division of Reactor Projects

J. E. Whittemore, Operator Licensing Examiner, Operator

Licensing Section, Division of Reactor Safety

Approved:

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j[ o ) 0

. (1ebe, Chd ef, Project Section D Datt

0 ision of Reactor Projects

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inspection Summary-

Inspection Conducted July 30 through August 8,1990 (Report 50-498/90-28;

50-499/90-28)

Areas Inspected: Special, announced inspection included onsite followup of

two events.

Results: Within the area inspected, two apparent violations were identified.

.

The first violation involved an-improperly aligned auxilary feedwater test

return line.. This resulted in the affected train being inoperable when needed -

following a' loss of normal feedwater. The lineup error was also not identified

by the required independent check.- The inadvertant boron dilution event

represented a lock of licensee awareness for processes which could potentially

affect reactivity. The second violation (failure to include criteria in

procedure to determine that important activities were satisfactorily

accomplished) involved the failure to ensure that a mixed bed demineralizer

contained the proper boron content. This resulted in an inadvertant boron

dilution event during full power operation on August 6,1990, which resulted

in reactor thermal power exceeding 100 percent. (paragraph 2.B). An enforcement

. conference was held on August 29, 1990, to discuss the apparent violations and

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' the corrective actions. Based on the inspection' and infomation provided in' '

the enforcement conference..the NRC concluded that operator actions to control- -

reactor power and reactor coolant system temperature were appropriate, j

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DETAILS

1. ' Persons Contacted

- W. H. Kinsey, Plant Manager

- M. R. Wisenburg, General Manager of Assessnent

M. A. McBurnett, Nuclear Licensing Manager

J. Loesch, Operations Manager

K. Christian, Manager of Operations Unit 1

,'

C A. Ayala, Supervising Engineer, Licensing

A. K. Khosla, Senior Engineer, Licensing

Denotes those individuals attending the exit interview conducted on

August 1, 1990.

- Denotes those individuals attending the exit interview conducted on

August 8, 1990.

2. Onsite Followup of Plant Events

A. Auxiliary Feedwater System Valve Lineup Error

.

At 7:48 p.m. on July 30, 1990, Unit I was manually tripped when [

the "A" feedwater isolation valve went fully closed during the

performance of a surveillance procedure. The surveillance was being

performed to verify that both the permanent test circuitry and the ;

electrohydraulic control fluid solenoid dump valves were operating l

correctly. This surveillance is accomplished by stroking the

feedwater isolation valve from fully open to 90 percent open and then 'I

back to fully open. While placing a jumper wire for the ;

surveillance, the I&C technician inadvertently made contact with the

wrong tenninal block which caused the feedwater isolation valve to go .

fully closed. Control room operators manually tripped the reactor

when Steam Generator IA level reached 40 percent. An automatic reactor trip would have occurred at a level of 33 percent. ,

' Subsequent to the trip, control room operators noted that the level

..

in Steam Generator 1A was continuing to decrease even with auxiliary

l, feedwater (AFW) in service at a flow of 600 gpm. A reactor plant

operator was dispatched to the AFW pump to attempt to identify the

problem. Atter verifying the integrity of the piping and the pump,

h the dispatched operator discovered that the long path recirculation

l valve (AF-0040) was locked open although it should have been locked

closed. The open valve was allowing AFW to be pumped back to the <

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' AFW storage tank instead of into the steam generator. Steam. i

I Generator 1A was then fed through the cross-connect valve and AFW

l Pump No. 11 was stopped. Steam Generator 1A level decreased to .

l 35 percent before the level stabilized and started to increase. The :

! recirculation valve was repositioned, and AFW was then established to !

Steam Generator 1A via the No. 11 AFW pump. The valve restoration -

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took about 40 minutes. All other manual recirculation valves ,

associated with engineered safety feature (ESF) functions were ;

, subsequently verified to be locked closed in both units. !

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The last time that AF-0040 was known to have been operated was on

July 26, 1990, during the performance of procedure IPSP03-AF-0001, '

" Auxiliary Feedweter Pump 11 Inservice Test." Step 5.13.1 l

recuires AF-0040 to be closed and locked. Steo 5.13.2 recuires an ;

incependent verification that AF-0040 is closrd and lockec. !

Subsequent investigation by the licensee disclosed that Steps 5.13.1 .!

and 5.13.2 were performed at the same time. !

Recirculation Valve AF-0040 was apparently not locked closed and the- )'

independent verification requirements of Procedure 1 PSP 03-AF-0001,

" Auxiliary Feedwater Pump 11 Inservice Test" Step 5.13.2, apparently .

did not ensure that the long path recirculation valve (AF-0040) was

satisfactorily locked closed. Plant Procedure OPGP03-ZO-0004, " Plant

Conduct of Operations," Revision 11. Step 4.4.11, requires that

independent verifications shall be performed as prescribed by approved ,

procedures or instructions in accordance with Procedure OPGP03-ZA-0010, ,

t " Plant Procedure Compliance, Implementation, and Review." Plant '

!

Procedure OPGP03-ZA-0010, Revision l's Step 3.3.2.1, states that the

act of performing the independent y' ~fication must be completely i

separate and independent of G: ' ,i alignment, installation, or L

verification. The fact that Stec ' 13.1 and 5.13.2 were performed !

,

concurrently and not separate au, udependent represents a failure to

L follow the procedure specified for independent verification and is

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consideredanapparentviolation(50-498/9028-01).

B. Inadvertent Dilution of Reactor Coolant System Boron Concentration

,

On August 6, 1990 Unit 1 experienced a decrease in boron ;

concentration in the reactor coolant system (RCS). This resulted

L in an unexpected positive reactivity addition. The reactor was

L initially in a steady state condition at 100 percent power with -

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L the control rods in manual. Control Rod Bank D was at 244 steps.

L All other banks were at 259 steps. The sequence of events, as

I established during this inspection, is shown in the attachment to

this report. ,

At approximately 8:30 a.m. on August 6,1990, shift turnover briefings *

were conducted between reactor operators and chemical analysis

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technicians. At that time the chemical analysis techniciaas indicated

that' chemical volume and control system (CVCS) mixed bed ,

Demineralizer 1A needed to be placed in service in order to reduce

the sodium content in the RCS. They also informed the>>perators that

.CYCS mixed bed Demineralizer 1A had been previously bo'ated to

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2500 ppm. At 9:10 a.m. , pursuant to procedure IP0P02-CV-0004,

" Chemical and Volume Control System Subsystem," the control room

requested chemical analysis personnel to determine th! amount of i

water needed to flush the demineralizer bed to achieve equilibrium ,

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conditibns with the RCS. Based on the infonnation that mixed bed l

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Demineraiizer IA had 2500 ppm boron, the chemical analysis technician !

calculatt'd that 2500 gallons of RCS effluent would be required for a i

preservice t!ush. i

As discussed below, it was later demonstrated that mixed bed !

Demineralizer 1A did not contain the expected amount of boron and, :

as a result, the calculated amount of flush water was in error. l

Neither operations Procedure IPOP02-CV-0004, Revision 8. or any ;

administrative procedure contained adequate acceptance criteria to l

determine that the activities to place a mixed bed demineralizer ;

in service had been satisfactorily accomplished. This is an apparent #

violation of 10 CFR Part 50. Appendix B, Criterion V which requires,

in part, that procedures include acceptance criteria to be used to !

determine that important activities have been satisfactorily I

accomplished (498/9028-02).

At approximately 9:58 a.m., mixed bed Demineralizer 1A was aligned

to the waste holdup tank and 2500 gallons of RCS effluent was flushed ;

through the bed. At 10:58 a.m., mixed bed Demineralizer IA was +

placed in serv. ice and, at 11 a.m., mixed bed Demineralizer IB.was ,

removed from service.

At approximately 11 a.m., the Proteus computer was taken out of

service for a maintenance adjustment. When it was returned to

service at approximately 11:10, the reactor operator noted that a

slight increase in Tavg of 0.2 degrees had occurred. In response

to the increasing Tavg the reactor operator added boric acid by

L .the batch method. He added one 10-gallon and three 5-gallon volumes

within the next 4 minutes. These actions served to momentarily

L inhibit the Tavg increase, but power continued a slow increase. :

l During this period the unit supervisor went to the control boards to I

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observe indication and operator action. The demineralizer was

! bypassed approximately 4 minutes after the event detection

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. (11:10 a.m.), according to the licensee. This action was not

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documented.

l The licensee's subsequent review shows that:the operators started

to insert control rods at 11:17 (the Proteus computer data printout

shows that the control rods had been inserted four steps before

11:15). As shown in the attachments, thermal power exceeded licensed

power from 11:15 until 11:36 and then again from 11:41 until 11:45.

During this time the operators injected boron and inserted control

rods.in an attempt to reduce and stabilize reactor power below 100

'

percent.

1

Two other evolutions were in progress at the start of this event. :

l The:first evolution was an Analog Channel Operational Test (ACOT),

l- which was being performed on RCS Loop 2 deltaT-Tavg and several

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associated bistables were, therefore, tripped. This ACOT was secured

shortly after the start of the event and, therefore, had little if any

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influence on subsequent operator action. The second evolution was

that the operating crew was attempting to maintain a steady Bank "D"

rod position so that the shift technical advisor (STA) could

determine and establish a new core delta flux (delta-I) target band.

Interviews were held with the reactor operator (RO) and the unit

supervisor (US) on duty at the time of the event. Both operators

stated that they were concerned about inserting rods too fast and

too deep which would cause a core power distribution (delta-flux)

.,

problem. Discussions were subsequently held with the Unit 1

operations manager who stated that he was completely satisfied with

the control room operators' pcformance during this event. He

further stated that it was necessary to use a slow, deliberate

e approach to control the transient and preclude other problems, such

as safety injection initiation or severe flux tilts. The operators

themselves expressed the same reservations about complicating the

event. The inspectors observed that following this slow, deliberate

approach to control the transient, rather than initiating emergency

boration or significantly inserting control rods, allowed-the

indicated power level to exceed 103 percent by the highest indicating

nuclear instrument channel and to exceed 100 percent of licensed

thermal power for 21 minutes and then for 3 minutes.

Subsequent to the event, an enforcement conference was conducted

in the Region IV office on August 29, 1990, to discuss the causes

of the event and.the adequacy of operator actions. The handouts

used by the. licensee at this conference are attached to this

inspection report. .At this meeting the licensee presented the

following causes for.the event:

The procedure for placing the demineralizer in service did not

require a sample or provide acceptance criteria for boron

concentration prior to demineralizer use.

The procedure for ensuring proper boron concentration in the

demineralizers was less than adequate.

The conduct of operations procedure for controlling power

excursions contained less than adequate guidance..

The licensee also presented evidence that showed that maximum reactor

thermal power attained was 101 percent and that the reactor was above

100 percent reactor themal power for about 24 minutes. This

operation was'shown to be within the bounds assumed in the design

basis analyses.

Operator actions were found to have been adequate to control the

event and assure safety, however, the licensee has implemented

program improvements to assure that control rod insertion is to be

used in the event reactor power unexpectedly exceeds 100 percent

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power. Additionally, specific guidance was also developed to reduce

reactor power prior to planned evolutions that have the potential to

cause reactivity additions.

As a result of the NRC review of this event and the information

provided during the enforcenent conference, the NRC concluded that

o>erator actions in response to the transient were adequate. Although

tierwel power was above 100 percent for approximately 24 minutes, the

operators were aware of the cause of the transient and took adequate

actions to control the power increase. The transient was within the

plant design basis. ' One violation was identified involving the lack

of appropriate acceptance criteria in procedures to ensure that the

demineralizers have an appropriate boron concentration prior to being

placed in service.

3. Exit Interview

The inspectors met with licensee representatives (denoted in paragraph 1)

on August 1 and 8, 1990. The inspectors summarized the scope and findings

of the inspection. The licensee did not identify as proprietary any of

the information provided to, or reviewed by, the inspectors.

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ML20059K943

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