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Radiological Impact of Commercial Nuclear Power Plant Releases: a 12-year Study

Radiological Impact of Commercial Nuclear Power Plant Releases: a 12-year Study. Jason T. Harris, Ph.D. Idaho State University/NATC. Introduction General Theory and Methodology Radiological Impact of Effluent Releases Correlation between Effluent Releases and Electrical Generation

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Radiological Impact of Commercial Nuclear Power Plant Releases: a 12-year Study

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  1. Radiological Impact of Commercial Nuclear Power Plant Releases: a 12-year Study Jason T. Harris, Ph.D. Idaho State University/NATC 18th Annual RETS-REMP Workshop June 23-25, 2008

  2. Introduction General Theory and Methodology Radiological Impact of Effluent Releases Correlation between Effluent Releases and Electrical Generation REMP Evaluation Summary and Future Work Presentation Outline 18th Annual RETS-REMP Workshop June 23-25, 2008

  3. NPP Radiological Releases • Small amounts of radiation released during normal operating conditions • Liquid effluents • Gaseous effluents • Three categories of radioactive by-products produced • Fission products • Over 300, many insignificant • 85Kr, 131I, 133I, 133Xe, etc. • Neutron activation products • 13N, 14C, 41Ar, 58Co, 59Fe, 60Co • Tritium (3H) • Typically, radiological emissions insignificant to population • Effluent activities decreasing Introduction (1/5) 18th Annual RETS-REMP Workshop June 23-25, 2008

  4. Introduction (2/5) • Regulatory Criteria for Releases • Radiation protection regulations based upon recommendations by ICRP and NCRP • U.S. regulations concerning nuclear power plant releases 18th Annual RETS-REMP Workshop June 23-25, 2008

  5. REMP • NPPs required to monitor the radiological impact of reactor operations on the environment and public (NEPA 1969 and FWPCA 1976) • Program • Preoperational and operational components • Trend and assess radiation exposure rates and conc. in the environment • Annual report submitted (and for releases) • Problem– decreased programs, decreased LLDs (positive results), public opinion, recent unexpected releases, and staff turnover Introduction (3/5) 18th Annual RETS-REMP Workshop June 23-25, 2008

  6. Although effluent releases are well below regulatory limits (1%) it is important to continually monitor and scrutinize effluent release programs • Effluent releases have a direct financial impact on nuclear liability insurance premiums via the ERF (Engineering rating Factor) program.  There is also an indirect financial impact.  Performance information also plays an important part in the development of insurance risk profiles that support loss control strategies at each nuclear power plant facility.  • As technology improves, MDAs will decrease and what may not have been there in the past, may now appear • Increased environmental findings at several operating and decommissioned plants • Public perception and confidence (Reputation!) Introduction (4/5) 18th Annual RETS-REMP Workshop June 23-25, 2008

  7. Purpose of Research • Protection of public health and safety • Study for entire U.S. commercial NPP industry • Litigation protection, environmental pathway validity, trending, projected impact (license renewals, new NPP construction, power-uprates), public perception • Compliance with National Environmental Policy Act of 1969, as amended and National Cancer Institute (1990 cancer study, NIH) • 11 year study of all data for U.S. NRC, NSF, NPP utilities and UNSCEAR • ICRP 2007 Recommendations (protection of non-human species) • Comprehensive database development • Recent NPP groundwater contamination and environmental release events • Hypothesis • Commercial nuclear power operations continues to pose little risk to the general public (radiological releases) Introduction (5/5) 18th Annual RETS-REMP Workshop June 23-25, 2008

  8. U.S. NRC Dose Models General Theory and Methodology (1/4) Generalized equation for calculating annual radiation dose via liquid effluent pathways (U.S. NRC Regulatory Guides 1.109 and 1.111) Cip= concentration of radionuclide i in the media of pathway p, (Bq L-1, Bq kg-1, or Bq m-3 ); Daipj = dose factor, specific to age group a, radionuclide i, pathway, and organ j (mSv pCi-1 ); Raipj= annual dose to organ j or an individual of age group a, from nuclide i via pathway p mSv y-1 ); and Uap = exposure time or intake rate (usage) associated with pathway p for age group a (hr y-1, L y-1 or kg y-1 ). Obtained by summing potable water, aquatic food, shoreline deposit, and Irrigated food pathway doses 18th Annual RETS-REMP Workshop June 23-25, 2008

  9. U.S. NRC Dose Models General Theory and Methodology (2/4) Combined equation for calculating annual radiation dose via airborne effluent pathways (USNRC Regulatory Guides 1.109 and 1.111) D(r,θ) = total annual dose to an individual from airborne releases at location (r,θ) (mSv yr-1); DT= annual total body dose from noble gas releases from free-standing stacks more than 80 meters high (mSv y-1 ); D∞T= annual total body dose from all other noble gas releases (mSv y-1 ); DG= annual organ dose from external irradiation from radionuclides deposited onto the ground surface (mSv y-1 ); DA= annual organ dose from inhalation of radionuclides in air (mSv y-1 ); and DD= annual organ dose from ingestion of atmospherically released radionuclides in food (mSv y-1 ); 18th Annual RETS-REMP Workshop June 23-25, 2008

  10. UNSCEAR Dose Model General Theory and Methodology (3/4) Generalized equation for calculating collective effective dose pathways (UNSCEAR 2000) Model site and conditions Ai =activity of release category i (GBq); DCE = total collective effective dose (person-Sv GW-1 y-1); Di = collective dose for release category I (person Sv-1 PBq-1 ); and E = energy produced by the nuclear reactor (GW y-1 ). Collective dose is divided according to release type (liquid or gaseous), radionuclide category (noble gases, tritium, C-14, iodine, particulate matter), and pathway (immersion, inhalation, ingestion, and external irradiation) 18th Annual RETS-REMP Workshop June 23-25, 2008

  11. Censored Data General Theory and Methodology (4/4) • Nuclear power plant releases are very small and may be below analytical detection limits (left censored data) • RETS and REMP reporting often include LLD and/or MDA values • Interpretation of results requires different statistical methods than for non-zero or non-LLD values • Because LLDs varied from one plant to another, substitution was used for less than values • Mean and median calculated for industry REMP study 18th Annual RETS-REMP Workshop June 23-25, 2008

  12. Methods • Data from annual effluent release reports (1995-2005) • Gaseous effluents • Fission and activation products, total iodine, particulates, tritium • Liquid effluents • Fission products, dissolved and entrained gases, tritium, “other” radionuclides • Trend analyses (Mann-Kendall) • Dose calculations • Collective effective dose - UNSCEAR • Theoretically maximally exposed individuals – U.S. NRC Radiological Impact of Effluent Releases (1/11) 18th Annual RETS-REMP Workshop June 23-25, 2008

  13. Results • F/A gases and tritium released in highest quantities • Iodines and particulates several orders of magnitude lower • Singular events can skew entire industry data • PWRs (total) released in higher amounts due to greater number of plants Radiological Impact of Effluent Releases (2/11) Variation of radionuclide activity released in gaseous effluents from PWR plants. 18th Annual RETS-REMP Workshop June 23-25, 2008

  14. Radiological Impact of Effluent Releases (3/11) Variation of radionuclide activity released in gaseous effluents from BWR plants. 18th Annual RETS-REMP Workshop June 23-25, 2008

  15. Results • Tritium released in highest quantities • Fairly level • Marked decline in BWR fission products and dissolved and entrained gases (fuel performance) Radiological Impact of Effluent Releases (4/11) Variation of radionuclide activity released in liquid effluents from PWR and BWR plants 18th Annual RETS-REMP Workshop June 23-25, 2008

  16. Trend Detection • Mann-Kendall Non-Parametric Test Statistic • Results • Gaseous PWR F/A Gases – decreasing trend • Liquid PWR Tritium– increasing trend • Gaseous BWR Tritium – increasing trend • Liquid BWR Other Radionuclides – decreasing trend • Gaseous Total F/A Gases – decreasing trend • Liquid Total Other Radionuclides – increasing trend • All other categories – no trend Radiological Impact of Effluent Releases (5/11) 18th Annual RETS-REMP Workshop June 23-25, 2008

  17. Results • CEDs show same pattern as activity releases • Variation in doses not as significant due to difference in collective doses • Even with small collective dose, tritium delivers highest CED due to volume released Radiological Impact of Effluent Releases (6/11) Gaseous effluent release collective effective doses for PWR plants 18th Annual RETS-REMP Workshop June 23-25, 2008

  18. Results • CEDs show same pattern as activity releases • Variation in doses not as significant due to difference in collective doses • F/A gases highest CED (less tritium released) Radiological Impact of Effluent Releases (7/11) Variation of radionuclide activity released in gaseous effluents from BWR plants. 18th Annual RETS-REMP Workshop June 23-25, 2008

  19. Results • PWR liquids give highest CEDs • Many BWRs do not release liquids Radiological Impact of Effluent Releases (8/11) Liquid effluent release collective effective doses for PWR and BWR plants 18th Annual RETS-REMP Workshop June 23-25, 2008

  20. Radiological Impact of Effluent Releases (9/11) Average effective doses received by members of the public in the U.S. from commercial nuclear power plant radiological effluent releases. 18th Annual RETS-REMP Workshop June 23-25, 2008

  21. Results • Cumulative doses obtained by summing total body air dose, skin air dose, critical organ air dose, total body liquid dose, critical organ liquid dose, and site direct radiation • Total cumulative dose for PWRs and BWRs similar Radiological Impact of Effluent Releases (10/11) Mean annual total-body dose and cumulative dose commitments received by maximally exposed individual members of the public in the U.S. from PWR and BWR nuclear power plant radiological effluent releases 18th Annual RETS-REMP Workshop June 23-25, 2008

  22. Radiological Impact of Effluent Releases (11/11) Yearly total-body dose and cumulative dose commitments received by maximally exposed individual members of the public in the U.S. from commercial nuclear power plant radiological effluent releases Doses to the general public are insignificant compared to other radiation sources 18th Annual RETS-REMP Workshop June 23-25, 2008

  23. Correlation • Determined to measure association between activity released and electrical energy generated • Specifically done to look at the affect of power-uprates • Release activities looked at for period of 3 years before and after uprate took affect • Normalized with capacity factor • Importance – effluent dose models (UNSCEAR) and trends normalized by plant type and electrical energy generated Correlation between Release Activity and Electrical Generation (1/2) 18th Annual RETS-REMP Workshop June 23-25, 2008

  24. Pearson product-moment correlation • Statistic is defined as the sum of the products of the standard scores of the two measures divided by the degrees of freedom • Numerical range of +1 - -1 • Results • No correlation (or pattern) between any release type and electrical generation (when compared alone) • Regardless of shared data • Industry mean – no correlation Correlation between Release Activity and Electrical Generation (2/2) 18th Annual RETS-REMP Workshop June 23-25, 2008

  25. Methods • Summary Data from annual REMP reports • Sample medium, type and number of analyses performed, LLD, mean and range of indicators, mean and range of control locations, and number of non-routine reports • Pathways and Analyses • Direct radiation (TLD) • Water - surface, ground, drinking (tritium, gamma) • Sediments (gamma) • Fish/Invertebrates (gamma) • Food products, vegetation (gamma) • Air particulates (gross beta) and Iodine • Soil and grass (gamma) • Non-routine samples (precipitation, storm water) • Number of analyses for study • Sites average ~2000 y-1 • Total – 1.4 x 106 REMP Evaluation (1/7) 18th Annual RETS-REMP Workshop June 23-25, 2008

  26. Results • Taken from effluent doses given by each pathway • Direct radiation largest contributor (especially for BWR plants REMP Evaluation (2/7) Percent total cumulative dose contribution of various pathways resulting from U.S. nuclear power plant effluent releases. 18th Annual RETS-REMP Workshop June 23-25, 2008

  27. REMP Evaluation (3/7) Ranking of environmental media based on potential radiation dose from BWR (above) and PWR (below) effluent releases.. 18th Annual RETS-REMP Workshop June 23-25, 2008

  28. REMP Evaluation (4/7) Percent of U.S. nuclear power plants sampling different REMP pathways and performing specific analyses (as of calendar year 2005) 18th Annual RETS-REMP Workshop June 23-25, 2008

  29. REMP Evaluation (5/7) Number and type of non-routine results reported in REMP samples for U.S. commercial nuclear power plants. Only 0.0116% of all analyses were non-routine. 18th Annual RETS-REMP Workshop June 23-25, 2008

  30. Results • Direct radiation from ISFSIs not statistically different from control locations • One plant gave exposure rates one order of magnitude higher • Emplacement of spent fuel is leading to higher exposure rates REMP Evaluation (6/7) Direct radiation gamma exposure rates from plant ISFSIs 18th Annual RETS-REMP Workshop June 23-25, 2008

  31. Conclusions • Summary Data • Detected radionuclides from background, weapons testing and plant produced • Use of controls and NRR isolate plant produced radionuclides • >99.9% of indicator results insignificant (compared to the controls) • Routine operation had no significant or measurable radiological impact to the environment • Releases well below regulatory limits (10 CFR 20 and 40 CFR 190) REMP Evaluation (7/7) 18th Annual RETS-REMP Workshop June 23-25, 2008

  32. Summary • Comprehensive evaluation and analysis of U.S. commercial nuclear power radiological effluent releases and REMP was conducted (1995-2005) • Effluent activities compiled and analyzed, showing trends • Average CED and doses to maximally exposed individuals calculated (continue to be very low compared to other sources of radiation and regulatory limits • No correlation found between effluent activity and electrical generation (when compared alone) • REMP evaluation showed no adverse radiological or environmental impact for the study period • Importance alone of database development can not be understated Summary and Future Work (1/2) 18th Annual RETS-REMP Workshop June 23-25, 2008

  33. Future Work • Total inventory still needed for radiological releases • Standardization of reporting needed • Standardization of LLDs • More research in precipitation washout and other pathways (particularly radionuclide concentration in ice/frost) • Continued industry analysis needed for providing accurate, scientifically bases information for the public Summary and Future Work (2/2) 18th Annual RETS-REMP Workshop June 23-25, 2008

  34. Acknowledgements • Ph.D. Committee – (Drs. Cember, Miller, Sandison, Schweitzer, Stewart) • US NRC PDR Staff • US NPP RETS-REMP staff • RETS-REMP Workshop Steering Committee • Ken Sejkora, Ph.D. – Pilgrim Station, Richard Conatser – Calvert Cliffs • Greg Barley – Progress Energy, Steve Sandike –Indian Point • John Doroski – Millstone, Doug Wahl – Peach Bottom • Richard Gilbert, Ph.D. Funding provided by Purdue University, NATC, NPP utilities, EPRI and DoE OCRWM Fellowship Program 18th Annual RETS-REMP Workshop June 23-25, 2008

  35. QUESTIONS? Thank you! 18th Annual RETS-REMP Workshop June 23-25, 2008

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