ML20086S347

AO-S1-74-13:on 741107,tube Rupture Occurred in Component HX 1-CC-E-1D.Caused by Equipment Malfunction.Hx Isolated & Component Cooling Surge Tank Refilled & Observed to Verify No Further Leakage

ML20086S347
Person / Time
Site:	Surry
Issue date:	01/10/1975
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086S354	List: ML20086S347 ML20086S361 ML20086S369
References
AO-S1-74-13, NUDOCS 8403010520
Download: ML20086S347 (8)

Text

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s VIROINIA 15LECTitic AND POWER C NM l niouxoun.vinoi m cocci j

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yL E January 10, 1975 p*JAN1gyg?O' @z.,'JT

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'$ sp Mr. Norman C. Moseley, Director Serial <No. 361 l Directorate of Regulatory Operations P0&M/JTB:clw United States Atomic Energy Commission Region II - Suite 818 Docket No. 50-280 230 Peachtree Street, Northwest License No. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moseley:

Pursuant to Surry Power Station Technical Specification 6.6.B.1, the Virginia Electric and Power Company hereby submits forty (40) copics of Abnormal Occurrence Report No. A0-SI-74-13.

The substance of this report has been reviewed by the Station Nuclear Safety and Operating Committee and will be placed on the agenda for*the next meeting of the System Nuclear Safety and Operating Committee.

Very truly yours,

6. 2%,Jkduup C. M. Stallings Vice President-Power Supply and Production Operations Enclosures 40 copies of A0-S1-74-13 cc: Mr. K. R. Goller, Assistant Director for Operating Reactors Mr. B. P. Scholfield Supervisor, Radiological Health Section Department of Health l

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PDR ADOCK 05000280 S PDR 424-Y L COPY SENT REGION m

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't) LJ ABNORMAL OCCURRENCE REPORT REPORT NO. A0-SI-74-13 UNPLANNED RELEASE OF LOW LEVEL RADI0 ACTIVE COMPONENT COOLING WATER TO JAMES RIVER

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DECEMBER 9, 1974 DOCKET NO. 50-280 LICENSE NO. DPR-32

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SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY m

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I. INTRODUCTION i

j In accordance with Technical Specification 6.6.B.1 for Surry Power I

Station, Operating License Number DPR-32, this report describes an abnormal occurrence which occurred on November 7, 1974. The Directorate of Regulatory Operations, Region II, was notified on November 8, 1974.

The occurrence reported herein is classified as an abnormal occurrence 2

pursuant to Technical Specification 1.0.I.3 which states that "An abnormal occurrence is defined as: any uncontrolled or unplanned release of radio-

, activity from the site."

! The occurrence described herein resulted in the release of low level i radioactive component cooling water to the James River, i

j II.

SUMMARY

-0F OCCURRENCE i On November 7, 1974 at about 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br />, with both units at cold l shutdown, a tube rupture occurred in component cooling heat exchanger i

4 1-CC-E-1D. This resulted in the release of approximately 8000 gallons of 1

low level radioactive component cooling water to the service water system 4

and ultimately to the James River.

Investigation of this occurrence further revealed that slow leakage

of the component cooling system to the service water system had been i .

i occurring since early September 1974. . The slow tube. leakage resulted.in i

the release of approximate'ly 35,500 gallons of low' level radioactive component cooling water to the service water system and' ultimately to the JamesIRiver.

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g g V U Therefore, a total of approximately 43,500 gallons of low level radioactive component cooling water was released to the James River as a result of slow heat exchanger tube leakage and subsequent tube rupture.

III. ANALYSIS OF THE OCCURRENCE The annunciating of a component cooling water low pressure alarm in the control room caused the Shift Supervisor to check the level indication for the component cooling system surge tank (1-CC-TK-1). The level indicated an essentially empty tank. Immediate steps were taken to identify and isolate the source of leakage from the system. Approximately 30 minutes after the receipt of the low pressure alarm, component cooling heat ex-changer 1-CC-E-1D was isolated. The surge tank was refilled and no further leakage was observed.

It is estimated that approximately 10 minutes elapsed from the time the surge tank was at normal operating level (%1700 gallons) until it was observed to be empty. Thus, the leak rate from the component cooling system was about 170 gallor s per minute. For conservatism, the leak rate is assumed to be 200 gallons per minute. Therefore, the failure leakage from the heat exchanger resulted in the release of about 8000 gallons of low level radioactive water.

Inspection of chemistry records further revealed that the component cooling system had been undergoing minor dilution since about September 2, 1974. This was assumed to be caused by slow out-leakage of component l

t cooling water to the service water system. An analysis of chemical l

incentration behavior in the component cooling system from September 2, 1974 to November 7, 1974 revealed an average dilution rate of about .37 gallons per minute. This was assumed to be_ equal to the rate of component

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cooling out-leakage to the service water system. This small leakage rate has resulted in'the release of approximately 35,500 gs11ons of low level radioactive water over the 66 day period between September 2, 1974 and November 7, 1974. This quantity of leakage is conservatively high since J there are known leakages in the auxiliary building and containment which are processed as liquid waste. Therefore, the actual release was less than reported herein.

Investigation of this occurrence revealed that several equipment 1

1 malfunctions contributed to the unplanned release of component cooling water to the service water systems; i.e. the failure of a tube in the heat exchanger 1-CC-E-ID, the failure of the component cooling surge tank i

low level alarm to sound and the failure of the service water radiation monitor (RM-SW-107) to properly indicate radioactivity in the service water system which is the heat sink for the compoaent cooling water system.

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l IV. CORRECTIVE ACTION TO PREVENT RECURRENCE 1

The immediate corrective action was to isolate the heat exchanger .

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l thus terminating the release. The component cooling surge tank was t

refilled and observed to verify no further leakage was occurring.

The heat exchanger was taken out of service, opened and inspected to determine the degree of tube failure. It was found that only one '(1) tube had failed. This tube was plugged, and other. tubes.were inspected for defects. The slow leak was caused by the gradual degradation of the heat exchanger' tube. The other component cooling heat exchangers were?

' inspected _for tube leakage and none found. .This is the first tube' failure-in_any of the component' cooling heat exchangers.

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O O Maintenance on the component cooling heat exchanger was completed and placed back in service at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on December 8, 1974. After a i short time in service, component cooling system leakage was again dis-covered. During the second inspection for leakage it was noted that the component cooling system surge tank level was decreasing at a rate of 1 approximately 0.65 gallons per minute. On December 9, 1974 at 0640 hours0.00741 days <br />0.178 hours <br />0.00106 weeks <br />2.4352e-4 months <br />, I-CC-E-lD was again isolated. An internal inspection of this heat exchanger revealed pinhole leaks in two (2) tubes. These two leaking tubes resulted 4

in the release of additional low level radioactive component cooling water to the James River.

The failed tubes in the component cooling heat exchanger 1-CC-E-1B i . .

were plugged and returned to service.

The additional' leakage conservatively resulted in the release of 2445 gallons of low level radioactive' water from the component cooling

water system to the Jcmes River.

The malfunctions of the service water radiation monitor'(RM-SW-107) t t

and the component cooling surge tank low level alarm are being investigated.

Appropriate repairs or design modifications'will be implemented, commensurate-with the investigative findings, to restore these devices to' proper.

1 l working condition.

l V. ANALYSIS AND EVALUATION OF SAFETY IMPLICATION OF THE OCCURRENCE

' The source of radionuclides in . the component cooling ' water. was slow f .leaka'ge from-the reactor' coolant system to the non-regenerative. heat

, exchanger. The concentrations of the radionuclides'present in the~com--

ponent cooling water are assumed to belthe highest measured during the:

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66 day slow leakage period, and at the actual value measured on November 7, i

1974 during the 40 minute tube rupture period. This is considered con-servative since dilution had been occurring since September 2, 1974.

The release of low level radioactive water from the component cooling system has been analyzed as two separate events: a 66 day slow leak and a 40 minute rapid leak. The radionuclides taken into account for purposes of 1

l this analysis are as follows: Iodine-131, Cesium-134, Cesium-137, Cobalt-58, Cobalt-60, Tritium and Dissolved Xenon-133.

3 During the 66 day period of slow tube leakage from the heat exchanger

[ the maximum percentages of MPC released for each radionuclide are as i

follows: 1131 .0133%, Csl34 .0078%, Csl37 .0075%, Coss .000078%,

Co60 .0002%, 1H3 .000096%, Xel33-l% (based on an MPC of 3 x 10-7 pCi/ml).

l The represents a prorated aggregate of 1.0289% of MPC.

During the 40 minute tube rupture period, the maximum percentages of MPC released for each radionuclide are as follows: 1131-0%, Cs134 .278%,

Csl37 .325%, Coss-0%, Co60-0%, 1H3 .012%, Xel33-2.38%. This represents

[ a prorated aggregate of 2.95% MPC.

The total amount of activity released was 2.433 curies. The total amount of. each radionuclide released is as follows: I131-1.1 x 104 pCi, Csl34-20.3 x 104pC1, Cal 37-43.3 x 104 pC1, CoS8-2.0 x 104 pC1, Co60_

1.8 x 104 pCi, IH3-87.4 x '104 pCi, Xel33-86.4 x 104 pCi. The maximum

! percentages of MPC for each radionuclide af ter the release was terminated I

are as follows

1131 .0133%, Csl34.00783%,lCsl37 .00752%, CoS8 .000078%,

.Co60 .0002%, IH3 .00010%, Xe133-1%.(based on an MPC of 3 x 10-7 pCi/ml).

l This represents a prorated aggregate'of.1.03%.

Only two radionuclides were present in the component cooling. water r

_during the period of the leak which was discovered on' December 9, 1974

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Cesium-134 and Cesium-137. These radionuclides were present in the following concentrations: Cs134 - 9.83 x 10-5 pCi/ml and Cs137 _

2.04 x 10-4 pCi/ml. During the leak, the maximum percentages of MPC released for each radionuclide are as follows: Csl34 - .886 x 10-3g and Csl37 .828 x 10-3%. This represents a prorated aggregate of 1.71 x 10-3% of MPC.

The above figures are based on the assumptions of no radioactive decay of the radionuclides of interest and four recirculation water C

pumps running for the duration of the release.

All analyses made were conservative and no 10 CFR 20 limits have been exceeded as a result of this unplanned release. Therefore, there were no safety implications associated with this event.

VI. CONCLUSI0tS The licensee concludes that:

1. The unplanned release was due to slow tube leakage and subsequent rupture of a tube in component cooling heat exchanger I-CC-E-1D.

2. An insignificant amount of radioactivity was released to the environment and all radionuclide concentrations were within 10 CFR 20 limits.

3. The occurrence described herein did not affect the safe operation of the station.

! 4. The occurrence described herein did not affect the health and safety 6f the general public.

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