Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations

Presentation on theme: "A Method for Quantifying Noble Gas Releases Doug Wahl Limerick Generating Station."— Presentation transcript:

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. Inspectors 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. –Dont 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 Hourly Average Monitor Readings for a 1-week Period Value used as Background for week

9 Consequences of Method More than 1400 Curies of Noble Gas Released Annually from 1999 through 2002. Limerick is in INPOs Worst Quartile for Gaseous Releases. Gaseous Effluents is one of the Twelve Areas of Plant Performance Measured by ANIs 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 Why the ANI Surcharge? A Perceived Increase Risk of Litigation. –ACE - Alliance for Clean Environment Tooth Fairy Project Limerick Part of the Toxic Triangle Occidental Limerick Waste Management

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 Stations Sole Record of Release? If No NG Activity is Found in the Grab Sample, Should you Report Zero Activity for the Month? Are INPOs 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 doesnt 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 North Stack – 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 Limericks 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 Limericks 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 Limericks 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 Limericks Revised Approach Each Monitors Monthly Calculated Mean and 2 Standard Deviations was used as Background for the Month.

23 Monthly Background Values Mean + 2 SD of 15-Minute Data Month Common North Stack A Common North Stack B Unit 1 South Stack A Unit 1 South Stack B Unit B South Stack A Unit 2 South Stack B Jan7.59E-076.54E-075.71E-076.83E-077.73E-075.44E-07 Feb7.91E-075.34E-076.40E-078.11E-077.85E-073.44E-07 Mar7.63E-075.65E-075.63E-076.85E-076.22E-074.99E-07 Apr7.62E-076.40E-076.12E-071.05E-068.17E-074.05E-07 May7.58E-075.08E-076.46E-078.57E-071.06E-063.53E-07 Jun6.31E-075.77E-075.17E-078.47E-076.82E-074.88E-07 Jul7.01E-075.08E-074.84E-071.32E-065.63E-073.30E-07 Aug6.56E-074.42E-075.73E-077.12E-07 3.38E-07 Sep7.28E-074.97E-075.71E-079.34E-076.08E-074.57E-07 Oct7.48E-075.71E-076.10E-076.49E-078.48E-074.12E-07 Nov6.04E-074.73E-075.22E-076.49E-077.47E-073.48E-07 Dec7.16E-074.73E-075.05E-075.77E-077.45E-074.88E-07

24 Limericks 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 Limericks 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 Limericks 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 INPOs Worst Quartile to Best Quartile

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

Download ppt "A Method for Quantifying Noble Gas Releases Doug Wahl Limerick Generating Station."

Similar presentations

Ads by Google