ML18095A318

LER 89-031-01:on 900605,determined That Waste Gas Sys O2 Greater than 2% Oxygen for More than 48 H,Per Tech Spec 3.11.2.5.a Requirements.Oxygen Entered Sys Via Holdup Tanks. Transmitters & Flow Control Valves recalibr.W/900626 Ltr

ML18095A318
Person / Time
Site:	Salem
Issue date:	06/26/1990
From:	Miller L, Pollack M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-031, LER-89-31, NUDOCS 9007020005
Download: ML18095A318 (6)

Text

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Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station June 26, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT B9-031-01; SUPPLEMENT This Supple2ental Licensee Event Report is being submitted to address a second event associated with high oxygen levels in the Waste Gas System contrary to the requirements of Technical Specifications. The root cause investigation associated with the first event is continuing. This second event is believed to have been caused by the same root cause as the first event. This supplemental LER 1s being submitted within thirty (30} days of the second event.

Sincerely yours, r~~

L. K. Miller General Manager -

Salem Operations MJP:pc Distribution r&::u.

I) J 95-2189 i10M) 12-89

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Oxygen concentration within the Waste Gas Holdup (WGH) System was greater than 2% for more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> between 10/17/89 and 10/19/89 and between June 3 t 1990 and June 6 t 1990 contrary to the requirements of Technical Specification Action Statement 3.11.2.5.a. The maximum oxygen concentration observed in any Waste Gas Decay Tank (WGDT) during the October 1989 event was 3.2% (in No. 11 WGDT) and 3.0%

during the June 1990 event (also in No. 11 WGDT) . No WGDT contained a concentration of oxygen above the 2% limit for more than approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Efforts to reduce the oxygen concentration were immediately implemented upon identification of the high concentrations in the WGDT's. It has been concluded that oxygen is entering the Waste Gas Holdup System via the eves Holdup Tanks. Samples of No. 13 eves Holdup Tank cover gas had oxygen concentrations as high as 3.5% on 10/28/89. Samples of the other tank cover gas sources, taken 11/12/89 through 11/14/89, {other than No. 11 eves Holdup Tank) to th,e Waste Gas Holdup System indicated concentrations of less than 0.1%.

Investigation as to the source of oxygen to the eves Holdup Tanks and thus ultimately the root cause of this event is continuing.

Associated transmitters and regulating valves have been recalibrated.

Work orders have been issued to support the investigation.

NRC F0<m ~

19-831 l

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 89-031-01 2 of 5 PLANT AND" SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reacto~

Energy Industry Identification System (EIIS) codes are identified in the text as (xx!

IDENTIFICATION OF OCCURRENCE:

Waste Gas Holdup System Oxygen Concentration Greater Than 2% For More Than 48 Hours Contrary to Technical Specification Action Statement 3.11.2.5.a

• Event Date(s): 10/19/89 and 6/05/90 Report Date: 6/26/90 I This report was initiated by Incident Report Nos.89-632, 89-635,89-638, and 90~366.

CONDITIONS PRIOR TO OCCURRENCE:

October 19, 1989 event: Mode 1, Rx. Power 100% Unit Load 1152 MWe June 3, 1990 event; Mode 5 (Cold Shutdown); Rx Startup in progress DESCRIPTION OF OCCURRENCE:

Oxygen concentration within the Waste Gas Holdup System {WEI was greater than 2% for more than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, contrary to the requirements of Technical Specification Action Statement 3.11.2.5.a.

On October 17, 1989, at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, Technical Specification Action Statement 3.11.2.5.a was entered due to an oxygen concentration of 2.6% by volume in the No. 11 Waste Gas Decay Tank {WGDT). Oxygen levels in the other three (3) WGDTs also exceeded 2% at various times through October 19, 1989, at 2140 hour0.0248 days <br />0.594 hours <br />0.00354 weeks <br />8.1427e-4 months <br />s_; when, the oxygen concentration in all the WGDTs was verified to be less than 2%. At this time the Action Statement was exited. The maximum oxygen concentration observed in any tank was 3.2% (in No. 11 WGDT). No WGDT contained a concentration of oxygen above the 2% limit for more than approximately 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

On June 3, 1990 at 0001 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, Technical Specification Action Statement 3.11.2.5.a was again entered due to an oxygen concentration of 2.3% by volume in the No. 11 WGDT. Oxygen levels in the other three (3) WGDTs also exceeded 2% at various times through June 6, 1990 at 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />; when, the oxygen concentration in all the WGDTs was verified to be less than 2%. At this time the Action Statement was exited. The maximum oxygen concentration observed in any tank was 3.0% (in No. 11 WGDT).

Efforts to reduce the oxygen concentration were immediately implemented upon identification of the high concentrations in the WGDT's. These methods included:

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 89-031-01 3 of 5 DESCRIPTION OF OCCURRENCE: (cont'd)

1. discharge of the Waste Gas Holdup Tanks, at pressure greater than 60 psi, via the plant vent (by procedure);

2. dilution of Waste Gas Holdup Tanks (if the tank pressure is less than 60 psi) with gas from other WGDTs if the oxygen concentration in those tanks is < 2% by volume;

3. nitrogen purge of the Waste Gas Holdup.tanks and eves Holdup Tanks; and

4. fill and vent of the eves Holdup Tanks Technical Specification 3.11.2.5. states:

"The concentration of oxygen in the waste gas holdup system shall be limited to less than or equal to 2% by volume.

APPLICABILITY: At all times.

ACTION:

a. With the concentration of oxygen in the waste gas holdup system greater than 2% by volume but less than or equal 4% by volume, reduce the oxygen concentration to the above limits within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

b. With the concentration of oxygen in the waste gas holdup system greater than 4% by volume, immediately suspend all additions of waste gases to the system and reduce the concentration of oxygen to less than or equal to 2% by volume without delay."

APPARENT CAUSE OF OCCURRENCE:

It has been concluded that oxygen is entering the Waste Gas Holdup System via the CVCS Holdup Tanks. Samples of No. 13 eves Holdup Tank cover gas had oxygen concentrations as high as 3.5% (on October 28, 1989). Samples of the other tank cover gas sources (other than No.

11 CVCS Holdup Tank} to the Waste Gas Holdup System indicated concentrations of less than 0.1%. When these samples were taken, between November 12, 1989 and November 14, 1989, the Waste Gas Holdup system was still indicating higher than expected concentrations of oxygen although not above 2%.

The source of the oxygen to the CVCS Holdup Tanks has not been determined as of the issue of this supplement. Investigations as to the source of oxygen to the eves Holdup Tanks and thus ultimately the ro6t cause of this event is continuing.

ANALYSIS OF OCCURRENCE:

The Waste Gas Holdup System is designed to provide controlled

LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 89-031-01 4 of 5 ANALYSIS OF OCCURRENCE: (cont'd) handling and disposal of radioacti~e gaseous wastes generated during routine plant operation. It will minimize exposure to plant personnel and to the general public as required by the Code of Federal Regulations.

The concern for oxygen-within the Waste Gas Holdup System is due to the presence of hydrogen gas within the system. In sufficient quantities, hydrogen in the presence of oxygen can be explosive. The Technical Specification level of not greater than 2% oxygen is conservatively low, ensuring that this explosive hazard is not present. Monitoring of the oxygen concentration in accordance with Technical Specifications ensures that if the oxygen concentration does increase above the 2% limitation expeditious corrective action can be taken to lower the level back below 2%. As discussed in the Description of Occurrence section, this action was taken, therefore, this event did not affect the health or safety of the public.

There are several direct pathways for oxygen to enter the WGDTs.

These direct pathways include cover gas from eves Holdup Tanks, the Volume Control Tank (VCT), the Spent Resin Storage Storage Tank (SRST), Reactor Coolant Drain Tank (RCDT) and the Pressurizer: Relief Tank (PRT). As identified in the "Apparent Cause of Occurrence" section, investigation has shown the oxygen is entering the Waste Gas Holdup System from the CVCS Holdup Tanks.

Historically, oxygen levels of greater than 2% by volume within the Waste Gas Holdup system is attributed to refueling/maintenance outage activities (i.e, reference LERs 272/87-019-01, 272/86-009-00, and 272/89-016-00). However, the Unit has been in operation for several months. Tperefore, this event cannot be attributed to such activity.

Investigation of the October 1989 event has included a review of a ,_

similar high oxygen event in September 1989 which did not result in I an LER. The source of the oxygen at that time was also found to be the CVCS Holdup Tank. The 1WG36 valve (Gas Decay Tank To Holdup Tank Regulating Valve} was found stuck in the closed position. When the Waste Gas Compressor drew upon the CVCS Holdup Tank cover gas, a vacuum formed within the tank(s} and the respective vacuum breaker opened allowing air into the tank. The 1WG36 valve was stroked and was shown to be operable.

If the oxygen concentration in the Waste Gas Holdup System exceeds 2%, it can normally be purged/diluted from the system within the 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Technical Specification time limit. However, as stated in the Description of Occurrence Section, the level could not be reduced within the Technical Specification Action Statement 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> time frame. Therefore, since Technical Speci~ication Action Statement 3.11.2.5.a was not complied with, this event is reportable in accordance with the Code of Federal Regulations 10CFR 50.73(a) (2) {i) {B).

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station I DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 gg....:..031-01 5 of 5 CORRECTIVE ACTION:

As discussed in the Description of Occurrence, section, the oxygen concentration was lowered to below the 2% limit.

As part of the investigation, transmitters and flow control valves have been recalibrated. No positive indication of the source of oxygen to the CVCS Holdup Tanks has been identified. Also, a dedicated team has been assigned and extensi~e monitoring has been established.

Investigation of the root cause of this event is continuing. Upon completion, a supplement to this LER will be prepared.

General Manager -

Salem Operations MJP:pc SORC Mtg. 90~075