A Method for Quantifying Noble Gas Releases

1. A Method for Quantifying Noble Gas Releases Doug Wahl Limerick Generating Station

2. Radiation Monitoring Display System (RMDS) • Design • Continuous monitoring gaseous effluents. • Alert Operations to abnormal releases. • Quantify gaseous effluents for reporting and dose calculations. • Sensitivity of 1E-06 uCi/cc (Xe-133) .

3. Effluent Monitoring History • RMDS Computer System failed in 1997. • System continued to function, but data was not stored for more than a one-hour period. • Live time available for emergency dose calculation. • Data was over written with new data. • No record of effluent releases. • Relied on grab samples for quantifying effluent releases. • Reported 0 curies of Noble Gas released in 1997 and 1998.

4. Effluent Monitoring History • New computer system installed in 1999. • Received an NRC violation in 1999. • Failure to maintain records of effluent releases - Tech. Spec. violation. • Inspector’s Philosophy • Power plants are not zero release. • Accuracy of numbers reported. • Urged Limerick to develop a means to quantify effluent monitor results.

5. New RMDS • Drawback • Electronic files not available except by IT. • Available as hard copy printouts only. • Don’t know when normal releases are occurring. • No Trending of data

6. Method of Quantification • Obtained the Weekly 1-hour Average Radiation Effluent Monitor Data Printout. • Determined the Daily High and Low 1-hour Readings (uCi/cc). • Averaged the Daily High and Daily Low to Obtain Daily Average.

7. Method of Quantification • Assigned the Lowest 1- hour Reading for the Week as Background (uCi/cc). • Subtracted the Background from each Daily Average. • Multiply by Flow and Time to obtain Curies released for Week. • In 1999 Reported 1412 Curies released.

8. Value used as Background for week HourlyAverage Monitor Readings for a 1-week Period

9. Consequences of Method • More than 1400 Curies of Noble Gas Released Annually from 1999 through 2002. • Limerick is in INPO’s Worst Quartile for Gaseous Releases. • Gaseous Effluents is one of the Twelve Areas of Plant Performance Measured by ANI’s Engineering Rating Factor. • Portion of Nuclear Plant’ Liability Premium is Redistributed. • Best performers – 20 percent credit • Worst performers – 30 percent surcharge. • Limerick Pays a Surcharge of about $40,000.

10. Airborne Fission and Activation Gaseous Effluents Comparison by Year per BWR Reactor (Total Curies)

11. Waste Management Occidental Limerick Why the ANI Surcharge? • A Perceived Increase Risk of Litigation. • ACE - Alliance for Clean Environment • Tooth Fairy Project • Limerick “Part of the Toxic Triangle”

12. 2000 Effluent Survey • 19 Plants Participated. • 11 Assigned Zero Activity for the Month if No Activity Found in Grab Sample. • Survey Raised Several Questions?

13. 2000 Effluent Survey • Is it Appropriate to Rely on the Monthly NG Grab Sample as the Station’s Sole Record of Release? • If No NG Activity is Found in the Grab Sample, Should you Report Zero Activity for the Month? • Are INPO’s Rankings Comparing Apples to Apples? • What is Background?

14. Noble Gas Grab Sampling • Monthly Requirement. • Additional Sampling as Warranted. • Increase Release Rate as Observed by Control Room • One Point in Time. • It doesn’t tell you what happened yesterday • Qualitative. • Nuclides being seen by rad monitors.

15. Noble Gas Grab Sampling • In 2003 No Activity was found in the Monthly Grab Samples. • Does that Mean there were No Releases for the Year? • If No Activity is Found – How to Quantify Gaseous Effluents?

16. NorthStack– A/B Monitor

17. North Stack 4/23/03

18. Goal • Develop a Method to Better Estimate Noble Gas Releases. • Statistically Driven • Determine a “Reasonable” Background • Understand the Role of the Noble Gas Grab Sample.

19. Limerick’s Revised Approach • Obtain the 2003 RMDS 1-hour Average Data from Information Technology. • Plot the Data, Observe and Investigate Anomalous Results. • Obtain the 2003 RMDS 15-minute Average Data for the Days that the Noble Gas Grab Sample was taken; as well as, for Days that Appeared to Show a Release from the 1-hour Data.

20. Limerick’s Revised Approach • Background Arbitrarily Chosen from 15-minute Data One Hour before the NG Grab Sample and One Hour after. • Assumed that if No Activity Found in Grab Sample then Effluent Radiation Monitor Reading was Background • Provided 8 data points for Statistics • Action taken for All Six Effluent Radiation Monitors (2 per release point).

21. Limerick’s Revised Approach • If 15-minute Data not Available or Suspect, then data from the Previous Month was used as Background. • Likewise, if Positive Activity were found in the NG Grab Sample, then Background Based upon a Previous Month where No Activity was Found.

22. Limerick’s Revised Approach • Each Monitor’s Monthly Calculated Mean and 2 Standard Deviations was used as Background for the Month.

23. Monthly Background ValuesMean + 2 SD of 15-Minute Data

24. Limerick’s Revised Approach • Each Monitors Background Number was Subtracted off Each Valid Hourly Reading. • Net Activity from the A and B Monitors were Averaged to obtain the Net Activity in uCi/cc. • Net Activity below Zero was Classified as Zero or “No Release”

25. Limerick’s Revised Approach • For Each Hour of Positive Net Activity the Number of Microcuries Released was Determined by the Formula: Where: Stack Volume (cc) = Total weekly stack volume 604800 (sec) = Number of seconds in a week uCi/cc = Net average hourly rate for the A and B monitor 3600 = conversion from seconds to hour

26. Limerick’s Revised Approach • Nuclide Mix Reported in FSAR Used to Calculate Dose • Using this Method Limerick Reported in the 2003 Annual Effluent Release Report 4.26 Curies of Noble Gas. • Significantly lower than the 1447 Ci reported in 2002. • Contribute to a Reduction in the ANI Surcharge • From INPO’s Worst Quartile to Best Quartile

27. Airborne Fission and Activation Gaseous Effluents Comparison by Year per BWR Reactor (Total Curies)