United States Nuclear Regulatory Commission - Protecting People and the Environment

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  
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                                                             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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