L-77-116, 04/18/1977 Letter RWT Overflow

04/18/1977 Letter RWT Overflow

ML18127B072
Person / Time
Site:	Saint Lucie
Issue date:	04/18/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Volgenau E Office of Nuclear Reactor Regulation
References
L-77-116
Download: ML18127B072 (11)

Text

P.O. BOX 3100 NIAMI, FLORIDA 33I01 FLORIDA POWER SI LIGHT COMPANY April 18, 1977 L-77-116 Mr. Ernst Volgenau, Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Volgenau:

Re: St. Lucie Unit 1 Docket No. 50-335 RWT Overflow The attached report is being submitted in accordance with 10 CFR 20.405(a)(5). At the time of the event, a telephone report. was made to the Region II Office of Inspection and Enforcement in accordance with Regulatory Guide 1.16, section C.4.

Very truly yours, Robert E. Uhrig Vice President REU/MAS/ms Attachment.

cc: Norman C. Moseley, Region II Robert Lowenstein, Esquire HELPING BUILD FLORIDA

ATTACHMENT Re: St. Lucie Unit 1 Docket No. 50-335 RWT Overflow On April 6, 1977, during a unit outage, the refueling water tank was overfilled. The cverflow from the RWZ entered the storm drain system which drains to the east storm water basin. This basin is within the site boundary but outside the'adiation Controlled Area.

The incident occurred while operations was lowering the RCS level in pre-paration for repairing a steam generator manway gasket. Upon noticing the RWT overflowing, immediate action was to stop all flow into the tank.

After a short valve alignment the level in the RHT was lowered by pumping some of the tank's contents back into the RCS. Approximately 3,800 gallons were estimated to have overflowed. Of this, approximately 2,850 gallons was calculated to have reached the storm water basin.

g. ~Ana1 sis:

Although the activity has been released from the Radiation Controlled Area, it has been retained within the site boundaries since the storm sewers discharge to the on-site storm water basin. (See attached sketch)

Immediate implementation of radiological controls, in the areas of concern, prevented contamination from being spread beyond the initially affected areas. No significant radiation exposure problems have occurred due to this incident.

I C. Evaluation Extent and Ha nitude:

(1) Samples of the overflow during the incident were analyzed for Gamma Isotopic Activity, Gross Alpha, Tritium and Strontium. (See Table I)

(2) Samples of the East Storm Basin from four different locations were analyzed individually showing good mixing and composited for low level counting of Gamma Isotopic Activity, Tritium and Strontium.

'See Table II)

(3) Calculations based on Tritium have shown the actual quantity of the release to the storm drain to he 2 g56 gallons.

(a) Total activity discharged from the controlled area 3e 27 curies (b) Total activity in the basin water based on C (2) above 1.61 curies (c) Total. activity remaining in storm sewer piping, basin mud and vege-tation ~ 1-66 curies

REFUELING WATER TANK 0 LOW APRIL 6, 1977 Page Two C. Evaluation Extent and Ma nitude, Continued (4) Results from item C (2) above have shown all isotopes in the East Storm Water Basin to be less than their respective MPC's with the following exceptions:

Conc MPC Iodine 131 2.4 X 10 3 X 10 7

• Iodine 133 9X106 1xlo 6

• Iodine 133 has a half-life of 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> and should decay to below its MPC in approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> from time of sample (4/6/77 9 1830).

(5) Samples taken from the West Storm Basin (approximately 500 feet west of the affected Storm Basin) on 4/7/77, approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the release showed no detectable activity. (See Table III)

(6) Additional surveillance of. the Basin and surrounding areas is con-tinuing at this time (canals, Atlantic Ocean, Indian River).

.D. Cause:

Although there were some mitigating circumstances (which will be evaluated as part of the corrective. actions), the root cause was the Operator not responding to the high RWT level and not reducing the level to clear the annunciator.

E. Corrective Action:

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The affected areas were roped off, posted, surveyed and sampled. The around the RWT will be removed and properly disposed of. The manholes fill will be cleaned and the drain lines flushed. All of these efforts will be closely followed by the Health Physics Department.

At the present time the final plans for disposition of the water in the Storm Water Basin are not completed.

The FRG has requested that Power Plant Engineering review the piping for the RMT overflow and provide alternatives if they are deemed'ecessary, The operating procedures which involve adding water to the RWT have been revised to address assurances that adequate volume is available in the tank and that filling of the tank is secured upon receipt of a high level alarm.

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FLORI D~OVER 8 LI GHT COMPANY 4

PFe LUCI E UNIT I 1 RADI OACTI VE ANALYSIS REPORT 1~ DATE/TIME 2o SAMPLE LOCATION 3e SAMPLE TYPE CP e 4o TRI TI tM ( UC I /ML) 5o STRONTI U.'4 (UCI/HL)

'o 'GROSS ALPHA (UCI/ML)

Vo REMARKSA g o e

S GAMMA SPECTRUM ANALYSIS! CALL VALUES I N UCI/ML)

MN 54 l CO-58 FE" 59 CO-60 SB-122 SB-124 BR-82 I"131 I"'133 NB-95 MO 99 CS" 136 CS 137

'R" TC 99M 95

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I FLORI D ONER 8 LI GHT COMPANY ST>> 1 UCI E UNIT i'1 RADI OACTI VE ANALYSIS REPORT I DATE/TIME 3'.

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MN 54 ~-F CO-58 W/

'O" FE" 59 0 60 SB- i 22 SB- 124

'I R" 82 e"~

l3l I-l33

~ HB-9 5 MO-99 CS" 1 36 CS-137 TC-99M Q ~

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LUCI E UNIT PI RADIOA TI VE ANALYSIS REPORT Io DATE/TIME 2o SAMPL E LO GATI ON 3o SAMPL E TYP E 4o TRI TI Ui'I ( UCI /ML)

So STRONTI Us<I ( UCI /HL) 6+= 'GROSS ALPHA (UCI/ML) 7o REMARKS A AS~' g C <~P J'8loed Si FE 59

'SB 222 GAMMA SPECTRUM pg zP

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ANALYSIS:

co-ss CO- 60 SB-124

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(ALL VALUES I N UCI/ML)

J, BR-82

- I"131 NB-9 5 4 'P'-233 MO 99 CS" 136 CS" 237 TC-99M 'R" 95

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