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Information Notice No. 83-52: Radioactive Waste Gas System Events
SSINS No.: 6835 IN 83-52 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 August 9, 1983 Information Notice No. 83-52: RADIOACTIVE WASTE GAS SYSTEM EVENTS Addressees: All nuclear power reactor facilities holding an operating license (OL) or construction permit (CP). Purpose: This information notice is issued to alert licensees to two recent events involving radioactive waste gas systems. The PWR event involved the inadvertent, offsite release of the contents of a waste gas decay tank (WGDT) over a 7-hour period. The BWR event involved power operation for a 25-hour period without the automatic isolation function capability on the condenser offgas system. In both events the offsite radiological consequences were negligible. However, these events clearly demonstrate that the level of attention given to the status and procedural controls for the operation and maintenance of these radioactive waste gas systems can be significantly improved. The corrective actions taken by the licensees to prevent reccurences are presented. Attachment No. 1 contains nine summaries of related events taken mainly from the Licensee Event Report files. It is expected that recipients will review this information for applicability to their facilities. No specific action or response is required. Description of BWR Event: During the 2330 shift turnover on May 9, 1983, the Brunswick Unit 2 on-duty Shift Operating Supervisor (SOS) noted unusually low readings (for existing reactor power level) on both main condenser steam jet air ejector (SJAE) offgas radiation monitors. After the proper operability of these monitors and was verified, local flow at the SJAE monitors was found to be 3.5 - 5.5 CFM (normal should be 12 - 15). Subsequent investigations revealed SJAE monitor readings were not consistent with the main stack monitor readings which were properly following the ongoing power ascensions. At 0315 on May 10 the operations shift personnel, having exhausted other potential causes of the problem, checked the positions of the radiation monitors' manual root isolation valves (2-06-V35 and V36). Both valves were found to be shut and when opened, all control room SJAE related indications including radiation level and hi-lo flow, annunciator returned to normal levels/conditions. A subsequent licensee investigation of the events leading up to the SJAE monitor isolation incident revealed that a plant modification of the offgas system had required a valve clearance (30 valves), which included shutting 8308040020 . IN 83-52 August 9, 1983 Page 2 of 4 valves V35 and V36 on April 10. On April 17, the clearance was partially restored (21 valves) with V35 and V36 to be restored to their normal open positions. On April 25 a Unit 2 startup was in progress with the SJAE's started briefly but not maintained in service because of low supply steam, pressure and a Group 1 isolation--main steamline isolation valve closures. With the unit shut down on April 26, the plant chemistry group wrote a "trouble ticket" for the low flow condition on the SJAE monitor; no work was ever performed and the ticket was eventually cancelled since (in a shutdown condition) no flow is normal. On May 8, SJAEs A and B were placed in half-load condition with Unit 2 in startup mode. Operations personnel judged no immediate action was necessary in response to the annunciator for hi-lo SJAE flow -- a history of past problems during startup existed, because of sample line condensation removal problems and low supply steam pressure (which would clear shortly as startup progressed). Poor performance of loop seal drains further compounded the problem of putting the SJAEs on line. Three different operations shifts (from May 8, 2300 to May 19, 2300) during the Unit 2 startup failed to identify and act on the abnormally low SJAE radiation monitor readings. While the hi-lo flow SJAE annunciator was noted, it was not a shift turnover action item, and hence, no followup was performed. Other indications available to the operations staff for problem identification were: 1. Failure of SJAE monitor readings to track with the main steam line radiation monitors and main stack monitor during the power ascension from 0800 - 2300 period. 2. Hi-lo flow SJAE annunciator alarm. 3. Virtually the same SJAE radiation monitor reading recorded in Daily Surveillance Report over power ramp up to 55%. The licensee initiated the following corrective actions to prevent recurrence: 1. Upgraded Operations On-shift Training Program by stressing: need for increased awareness of available control room indications, strict adherence to clearance procedure, and importance of valve positioning. 2. Added specific requirement for each shift to review and update annunciator status. 3. Increased involvement of operations engineering staff through evaluation of impact of major maintenance activities and communication of potential concerns to on-shift operations management. 4. Clearance procedure will be reviewed and revised as necessary to provide for better tracking and auditability of equipment status (e.g., valve position be determinable by time and date. 5. Personnel involved with the incident will have their individual performance reviewed for possible disciplinary action, employee counseling, and possible training/retraining. . IN 83-52 August 9, 1983 Page 3 of 4 The licensee reported that a comparison of primary coolant Iodine-131 Dose Equivalent values, SJAE radiation monitor readings, and main stack release rates for periods before and after the event were very similar, indicating health and safety of public were not affected the incident. Description of PWR Event: On February 27, 1983, during normal power operation of Turkey Point Unit 3, the contents of waste gas decay tank (WGDT) No. 2 were inadvertently released to the environs via the auxiliary building exhaust fan to the plant vent. The licensee reported that over a 7-hour period beginning at 1700, the waste gas decay pressure decreased from a reading of 98 psig to a reading of only 10 psig. This low pressure reading prompted a review of associated process radiation monitoring equipment printouts (SPING-4 gas monitor and R-14 vent monitor) which confirmed that a radioactive release had occurred during the WGDT pressure decay period. Samples of the remaining WGDT contents were taken and analyzed and together with the radiation monitoring system printouts, the licensee determined approximately 18 curies of gaseous activity were released. This reported release quantity is about 0.02% of the allowable quarterly release limit for total gaseous releases. Licensee followup of the event focused on the safety valve and the two normally closed valves (4638B and RCV-014) in the line from the WGDT to the waste gas release header. A special test of the associated waste gas safety (relief) valve verified its proper operation. The licensee determined that the 4638B valve had apparently not seated properly, and the hand controller for the RCV-014 valve was found to be slightly off zero leaving the valve slightly open. As a result of the investigation, the licensee took the following corrective actions: 1. Verified proper operation of the 4638B valve and installed a new diaphragm (although old diaphragm had no apparent damage). 2. Revised the plant operating WGDT release procedure to ensure that the RCV-014 valve will be "failed" closed after each controlled release. The attachment contains nine summaries of other related events involving various equipment and personnel problems associated with radioactive waste gas systems and their operation. These summaries are provided to illustrate the wide scope of potential problems with these systems. . IN 83-52 August 9, 1983 Page 4 of 4 If you have any questions regarding this matter, please contact the Regional, Administrator of the appropriate NRC Regional office, or this office. Edward L. Jordan Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: J. E. Wigginton, IE (301) 492-4967 Attachments: 1. Related Summaries 2. List of Recently Issued IE Information Notices . Attachment 1 IN 83-52 August 9, 1983 Page 1 of 3 SJAE RADIATION MONITOR ISOLATED (Brunswick,2, BWR) RO-76-12 EVENT DATE: 1/19/76 CAUSE: Improper valve position POWER LEVEL: 84% ABSTRACT: While increasing power to 95%, control room operator observed that SJAE offgas radiation monitor reading was not increasing with power. Investigation revealed no SJAE monitor sample flow because of shut sample supply valve; likely to have been shut during 12/27/75 investigation of loss of condenser vacuum. SJAE RADIATION MONITORS ISOLATED (Monticello, BWR) RO-77-06 EVENT DATE: 3/21/77 CAUSE: Undetermined POWER LEVEL: 55% ABSTRACT: During plant startup, both SJAE radiation monitors were found to be isolated. Work control process and startup procedures were revised to prevent recurrence. SJAE RADIATION MONITOR ISOLATED (Pilgrim 1, BWR) LER 78-052/03L EVENT DATE: 10/28/78 CAUSE: SJAE isolation (block) shut POWER LEVEL: 58% ABSTRACT: While conducting routine startup, low level SJAE radiation monitor readings were noted and investigation revealed that the block valve to SJAE monitor was shut. Licensee could not determine reason for mispositioning of block valve. UNPLANNED GASEOUS RELEASE (Maine Yankee, PWR) LER 81-003 (REV 1) EVENT DATE: 4/17/81 CAUSE: Containment sampling valve left open POWER LEVEL: 97% ABSTRACT: Licensee discovered a 1/4 temporary line off the containment air particulate detector (APD) had been left open nine days, following sampling of containment. The resulting containment leakage rate exceeded plant Technical Specification limits. The temporary sampling valve was not included in formal valve control administrative procedure. . Attachment 1 IN 83-52 August 9, 1983 Page 2 of 3 NO OFFGAS STACK SAMPLE FLOW (Duane Arnold, BWR) LER 81-002E EVENT DATE: 4/27/81 CAUSE: Open breaker POWER LEVEL: Shut down ABSTRACT: During a refueling and maintenance shutdown, the breaker supplying power to the offgas stack radiation monitor sample pumps was found open (not tripped). Reason for open breaker not determined; breaker was marked as spare, rather than sample, pump breaker. Operations personnel acknowledged alarm for low sample flow, but took no action at time of alarm. INADVERTENT WGDT RELEASE (Cook 1, PWR) LER 81-035 EVENT DATE: 8/26/81 CAUSE: Drain valves left open POWER LEVEL: 100% ABSTRACT: Leakage pathway occurred from waste gas vent header through spent resin storage tank (SRST) drain valves via the clean sump tank vent out the unit ventilation system. A non-licensed operator left SRST drain valves open after draining operation,, resulting in a substantial pressure drop in waste gas decay tank pressure (but negligible amount of gaseous activity released). INADVERTENT WGDT DEPRESSURIZATION (San Onofre 1, PWR) LER 82-017 EVENT DATE: 6/14/82 CAUSE: Waste gas system back-leakage POWER LEVEL: Shut down ABSTRACT: During a 24-hour period between surveillances, a WGDT depressurized from 25 psig to O psig (no actual radiological release occurred). Followup comprehensive helium leak testing verified leakage path was back through WGDT system. CONTAINMENT-PLANT VENT AIR PARTICULATE DETECTOR (APD) INOPERABLE (Salem 1, PWR) LER 82-078 EVENT DATE: 10/17/82 CAUSE: Personnel Error--capped sample line POWER LEVEL: O% ABSTRACT: During containment purge operations, licensee noted APD sample line to the plant vent had been erroneously capped during TMI-design change. APD had been isolated since before unit start-up in April 1982. . Attachment 1 IN 83-52 August 9, 1983 Page 3 of 3 INOPERABLE MAIN STEAMLINE RADIATION MONITORS (Nine Mile Point 1, BWR) EVENT DATE: 7/17/83 POWER LEVEL: 90% CAUSE: Defective detector cables ABSTRACT: On July 18, the NRC Senior Resident Inspector (SRI) identified two of the four main steamline radiation monitors were reading too low for existing reactor power level (90%). Subsequent licensee investigation revealed the two monitors were inoperable for approximately 27 hours because of defective radiation detector cabling. The detector cabling was repaired, recalibrations performed, and monitors returned to service. .
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