ML20004D552

Forwards LER 81-036/01T-0.Detailed Event Analysis Encl

ML20004D552
Person / Time
Site:	Fort Saint Vrain
Issue date:	05/27/1981
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20004D553	List: ML20004D552 ML20004D578
References
P-81155, NUDOCS 8106090525
Download: ML20004D552 (7)

Text

i D{ Public service company oe conomde TU Jj 16805 ROAD 19%

MEd PLATTEVILLE, COLOR ADO 80651 W

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s May 27, 1981 Fort St. Vrain

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pD*17 1 1 JUN 0 31981

,- u.s. nacun emarces ,s

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\,- , y' Mr. Karl V. Seyfrit, Director Nuclear Regulatory Cornission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 100J Arlington, Texas 7912

Reference:

Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Seyfrit:

Enclosed please find a copy of Reportable Occurrence Report No. 50-267/ >

81-036 Preliminary, submitted per the requirements of Technical Specifi-cation AC 7.3.2(a)2.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/81-036.

Very truly yours, Wot n Don Warembourg Manager, Nuclear reduction DW/cis Enclosure cc: Director, MIPC 00) s

//

82 o o09 o rar S

.O REPORT DATE: May 27, 1981 REPORTABLE OCCURRENCE 81-036 Determinee ISSUE O OCCURRENCE DATE: May 14, 1981 Page 1 of 6 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16805 WELD COUNTY ROAD 19 1/2 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/81-036/01-T-0 Preliminary IDENTIFICATION OF OCCURRENCE:

On Thursday, May 14,1981, at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, it was determined that the concentration of tritium in an unrestricted area following liquid waste resease number 460, which was made on May 12, 1981, exceeced the limit specifiec in LCO 4.8.2(a). At the time of the occurrence, the reactor plant was operating at 70% thermal power and approximately 230 MW electrical.

This event is reportable per Fort St. Vrain Technical Specification AC 7.5.2(a)2.

CONDITIONS PRIOR TO OCCURRENCE:

The conditions prior to occurrence or at the tima of reportability determination have no bearing on this report.

DESCRIPTION OF OCCURRENCE:

Upon analysis by plant personnel of samples taken during radioactive liquid waste release number 460, it was determined that the concentration of tritium in an unrestricted area exceeded the limit specified in LCO 4.8.2(a).

Refer .to Figure 1. Efflueists from the Reactor Building sump ( A )

and the liquid waste system ( ([) ) are disch rged to a common ine

( Oc ) leatins to the Goosecutil oisch ( o ). Circulatin9 water blowdown ( QE -) is admitted for dilution purposes prior to the effluent reaching the G osequill Ditch. Radiation monitors RIS-6212 and RIS-6213 ( 1 and U2A ) in the common discharge line alarm at preset values on high activity in effluent discharged from either the Reactor Building sump or the liquid waste system and provide a signal to rip the liquid waste transfer pumps ( Q3 ), close HV-6212

( ), and if the release is from the Reactor Building sump, close HV 204-2 ( (j) ), thus terminating the release.

Circulating water (dilution) flow is monitored by flow switch FSL-4101 ( ([ blowdown) ), which.at a preset value of low blowdown e

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/ :

REPORTABLE OCCURRENCE 81-036 ISSUE O Page 2 of 6 provides a signal lo close HV-6212 ( 04 ) and trip the liquid w ste transfer pumps ( U3 ) and Reactor Building sump pumps ( 7 )

((([> ) . In order o avoid a holdup of radioactive liquid waste in

ne oil separator ( 8 ) in the disenarge line common to the Rea ter Building sump and liquid waste system, normally open V-62247 ( 9 )

is closed and normally closed V-62248 ( (8) ) is opened prior to )

initiating a liquid waste release. These two valves are returned to  ;

their normal positions upon completion of a liquid waste release.

Liquid waste release number 460 was initiated at 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br /> on i May 12, 1981, and terminated at 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br /> on May 12, 1981. The recommended release rate was 9.0 gpm, with a recommended circulating water blowdown (dilution) rate of 2,000 gpm. A subsequent analysis indicated an average release rate of 9.2 gpm and an average circulating water blowdown (dilution) rate of 2496 gpm.

In order to track liquid waste concentrations in the unrestricted area during the course of liquid. waste release number 460, Health Physics Department personnel collected samples on an hourly basis throughout the release. Subsequent analyses indicated the following results.

Samole Date. Time Samole Number 3H Concentration, uCi/ml 5-12-81, 1300 RC 18349 3.55E-3" 5-12-81, 1400 RC 18370 2.36E-3 5-12-81, 1500 RC 18371 2.38E-3

• Result in excess of LCO 4.3.2(a) 3H limiting concentration in an

nrestricted area (3.00E-3 uC1/ml).

It should be noted that the sample indicating a concentration of .

tritium exceeding the limit of LCO 4.8.2(a) was taken from the <

Goosequill Ditch, considered to be in an unrestricted area, although  ;

~

located on Public Service Company of Colorado property. The Goosequill Ditch flows into a 25 acre farm pond, also on Company property. The overflow of this farm pond drains into the South ,

Platte River. The additional dilution provided by the pond ensures that the concentration of water entering the South Platte River is within the limits of LCO 4.8.2(a).

APPARENT CAUSE OF OCCURRENCE:

i The design of the Fort St. Vrain liquid waste discharge system is  !

inadequate to preclude problems of this nature from arising.

4 REPORTABLE OCCURRENCE 81-036 ISSUE O Page 3 of .

ANALYSIS OF  :

OCCURRENCE:

Radiochemical analysis of the liquid waste monitoring tank contents prior to liquid waste release number 460 indicated a tritium concentration of 5.66E-1 uCi/ml. Based on the recommend'ed release '

rate and dilution, the calculated tritium concentration in the unrestricted area would be 2.55E-3 uti/ml. Based on the average release rate and dilution, the calculated tri tium concentration in the unrestricted area would be 2.07E-3 uCi/ml. The results of samples taken at 1400 and 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on May 12, 1981, during liquid '

waste release number 460 show good agreement with the calculated concentrations. The result of the sample taken at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on May 12, 1981, was approximately one and one half times larger than the calculated concentrations. ,

An analysis of the main cooling tower makeup and blowdown flow recorder (FR 4101) subsequent to the occurrence indicated that blowcown flow was interrupted at approximately 1255 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.775275e-4 months <br /> on May 12, 1981, for approximately one to two minutes. Similar analysis of the liquid waste blowdown flow recorder (FR 6215) confirmed that the automatic control system responded properly by tripping the ,

liquid waste transfer pump and closing HV-6212. The transfer pump was manually restarted by Operations personnel approximately eight to ten minutes after tripping, and the release was completed without further incident.

Although the automatic control actions worked properly, the l approximately 150 to 200 gallons of liquid waste downstream of HV-6212 continued to be released upon loss of circulating water blowcown (dilution). The lack of sufficient dilution flow during this release period resulted in a tritium concentration in an unrestricted area in excess of the limit of LCO 4.8.2(a).

CORRECTIV:

ACTION: i

1. Operations personnel are investigating the cause of the circulating water blowdown (dilution) flow interruption.

2. Plant Management is investigating the possibility of installing {

another automatic valve at the location where the liquid waste  ;

discharge line meets the circulating water blowdown line, l designed to isolate the dead leg until conditions are acceptable '

for release to the unrestricted area.

Final resolution will be included in a future supplemental report.

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• REPORTABLE OCCURRENCE 81-036 ,

ISSUE O  :

Page 4 of 6 i

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. FAILURE DATA /SIMILAR f

., REPORTED OCCURRENCES: ,

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- PROGRAMMATIC IMPACT: i i

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CODE IMPACT:

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FIGURE 1 Circulating Water Blowdown a_ _. ) - fl' }

. _ . . ;st. ...g l l i e yst_4101 1

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-- > . + - - - l . .. . -

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'@ g @ 62t? 6H3 @ l V-62247 - _ - - - -

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R:dioactive Liquid l '

Waste (System 62) s l

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• V-62248  %$3

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l ', ponents referenced in this report 8

.._p.._.______-____-.~- liave been inct uded on this drawing.

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• Actual valve positions will depend M Recctor on the operation taking place.

Building i

Sump (Sys- * '

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ten 72) l To Liquid o Waste System $

Blowdown Flow

t REPORTABLE OCCURRENCE 81-036 ISSUE O

.Page 6 of 6 1

Prepared By: *d

( k. bM

.recericK J. B6vst '

Senior Plant Engineer t

Reviewed By:

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. . Ganm l chnical Services Supervisor i

Reviewed By: M Mr, I F. M. Ma Operatio/ hie / /

ns Marfaget

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Approved By: Yu Don Waremoourg / ,

Managei, Nuclear Produdtion .

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