ML19095A773

LER 75-003-00 for Surry Nuclear Station, Process Vents Gaseous Waste Release

ML19095A773
Person / Time
Site:	Surry
Issue date:	02/24/1975
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	Moseley N Division of Nuclear Materials Safety II
References
LER 75-003-00
Download: ML19095A773 (8)

Text

VIRGINIA ELECTRIC AND POWER COMP.ANY RICHMOND, VIRGINIA 23261 February 24, 1975 Mr. Norman C. Moseley, Director Serial No. 439 Directorate of Regulatory Operations PO&M/JTB:clw United States Nuclear Regulatory Commission Region II - Suite 818 Docket Nos. 50-280 230 Peachtree Street, Northwest License Nos. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moseley:

Pursuant to Surry Power Station Technical Specification 6.6.B.l, the Virginia Electric and Power Company hereby submits forty (40) copies of Abnormal Occurrence Report No. AO-Sl-75-03.

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,

~./Y).xfl-~'r C. M. Stallings Vice President-Power Supply and Production Operations Enclosures 40 copies of Ao~sl-75-03 cc: Mr. K. R. Goller Mr. Bryce P. Scholfield Supervisor, Radiological Health Section Department of Health

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e ABNORMAL OCCURRENCE REPORT REPORT NO. AO-Sl-75-03 PROCESS VENTS GASEOUS WASTE RELEASE JANUARY 21, 1975 DOCKET NO. 50-280 LICENSE NO. DPR-32 SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY L

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• r. INTRODUCTION In accordance with Technical Specification 6.6.B.l for Surry Power Station, Operating License Number DPR-32, this report describes an ab-normal occurrence which occurred on January 15, 1975. The Directorate of Regulatory Operations, Region II, was notified on January 16, 1975.

The occurrence reported herein is classified as an abnormal occurrence 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 radioactive gases and airborne particulate matter to the atmosphere.

II.

SUMMARY

OF OCCURRENCE On January 15, 1975 at about 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br />, with Unit No. 1 at cold shutdown conditions and Unit No. 2 operating at approximately 100 per cent of rated power a process vent particulate monitor alarm occurred followed by a ventilation vent particulate monitor alarm at 1835 hours0.0212 days <br />0.51 hours <br />0.00303 weeks <br />6.982175e-4 months <br />.

Iodine-131 and Sy particulate samples of the process vents and venti-lation vents taken immediately after the alarms occurred revealed the following results: process vents - no detectable 1 131 , Sy particulate 1.78 x 10- 13 µCi/cc; ventilation vents - 1 131 6.12 x 10- 14 µCi/cc, Sy particulate 5.78 x 10- 12 µCi/cc.

An investigation revealed that relief valve RV-GW-107 was open causing the release of radioactive gaseous waste from the gas stripper surge tank (l-BR-TK-6). Further inspection revealed that pressure control valve PCV-GW-107 was stuck open causing RV-GW-107 to lift. The release was terminated by

~hutting manual isolation valve BR-79. The release lasted for two and one-half hours.

III. ANALYSIS OF THE OCCURRENCE The boron recovery overhead gas system normally discharges to the hydrogen recombiner. Manual valve BR-79 is the isolation boundary between the,gas stripper surge tank (l-BR-TK-6) and the hydrogen recombiner. Pressure control valve PCV-BR-132 controls pressure in 1-BR-TK.:....6 at 120 psi or less.

Pressure control valve PCV-GW-107 provides a flow of radioactive gaseous waste to the hydrogen recombiner at a pressure of 4 psi. Relief valve RV-GW~l07 is set at 15 psi to protect the hydrogen recombiner supply line from overpressure.

The boron recovery system and hydrogen recombiner had been shutdown for a period of about three months in the fall of 1974. It is likely that this long period of inactivity resulted in the accumulation of dirt and corrosion products in PCV-GW-107. This is felt to be the primary cause for the failure of PCV-GW-107 to properly control pressure. Although, the release of radioactive material was from the gas stripper surge tank, it is noteworthy that particulate monitor alarms rather than gas monitor alarms occurred in both the ventilation and process vent systems. The cause for this apparent inconsistency is not known. The reason for the particulate monitors alarming rather than the gas monitors alarming is still under investigation.

IV. CORRECTIVE ACTION TO PREVENT RECURRENCE Pressure control valve PCV-GW-107 was tapped lightly with a hammer in an attempt to free the valve. After doing this, the valve setpoint was checked and adjusted from 5 psi to 4 psi and returned to service.

In order to prevent recurrence PCV-GW-107 will be overhauled to ensure that all internal components are in proper working order.

V. ANALYSIS AND EVALUATION OF SAFETY IMPLICATIONS OF THE OCCURRENCE All radionuclides known to be present by actual sample results are taken into account for this analysis. The concentrations of these radio-nuclides in the process and ventilation vents along with their maximum permissible concentrations (MPC) as defined in 10 CFR 20 are listed below.

PROCESS VENTS Radionuclide Concentration (µCi/cc) MPC (µCi/cc) xel33 i.dl X 10- 3 3 X 10-7 Kr85m 6. 66 X 10- 6 1 X 10- 7 Kr88 2. 92 X 10- 6 2 X 10- 8 xel3 3m 7.44 X 10- 6 3 X 10-7 xel35 7.56 X 10-S 1 X 10- 7 Ar41 l. 35 X 10-S 4 X 10-8 1131 None Detected 1 X 10-10 Sy particulate 1. 78 X 10-l 3 1 X 10-10 VENTILATION VENTS Radionuclide Concentration (µCi/cc) MPC (µCi/cc) 1131 6.. 12 X 10-l 4 1 X 10-lO Sy particulate 5.78 X 10-l 2 1 X 10-l O Each of the above radionuclides is assumed to enter the environment at a flow equivalent to the design maximum flow of the system in which it is present. These flows are as follows: Ventilation Vents - 191,300 cfm (FSAR, Section 9.13, Fig. 9.13-2), Process Vents - 300 cfm (FSAR, Section 11.2.5, Page 3-2 "Process Vent Blowers").

Technical Specification 3.11-3.B.1 requires that gaseous and airborne particulate wastes originating from station operation be limited as follows:

I:Q

- -i- <2.0 X 105 m3 (MPC). sec 1.

where Qi is the release rate (curies per second) of any radionuclide i and (MPC)i, in units of µCi/cc, is defined in Column I, Table II of Appendix B to 10 CFR 20, except that for halogen and particulate isotopes with half-lives greater than eight days, the values of (}1PC).1. shall be reduced by a factor of 700.

The calculated values of Qi for each radionuclide present are given below.

PROCESS VENTS Radionuclide Qi (Ci/sec) xel33 143 X 10-6 Krs5m 94 X 10- 8 Kr88 41 X 10-8 xel 33m 105 X 10-8 xel35 107 X 10- 7 Ar41 19 X 10- 7 1131 0 Sy particulate 25 X 10-15 I I

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VENTILATION VENTS 1131 5.5 X 10- 12 Sy particulate 5. 2 X 10-l O The release rates ( Qi ) for each radionuclide present are given (MPC).

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below.

PROCESS VENTS Radionuclide Release Rate (m 3 /sec) xel33 477 Krssm 9.4 Kr88 20.5 xel33m 3.5 xel35 106 Ar41 47.5 1131 0 Sy particulate .175 Net Release Rate 664.1 m3/sec VENTILATION VENTS 1131 38.5 Sy particulate 3641 Net Release Rate 3679.5 m3 /sec This represents a total release rate of 4343.6 m3 /sec or 2.1 per cent of the limit specified in Technical Specification 3.11-2.B.l.

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.., * ,t, CONCLUSIONS

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The licensee concludes that:

1. The release of radioactive gaseous waste was caused by the malfunction of pressure control valve PCV-CW-107.

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

3. The occurrence described herein did not adversely affect the health or safety of the general public.

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