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The Potential Importance of HTD Nuclides

The Potential Importance of HTD Nuclides. John W. Doroski. Introduction . The potential importance of HTD nuclide monitoring (Effluents and REMP) Need for Generic/Site Specific Position Papers Audience Feedback. Overview . Times are changing!

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The Potential Importance of HTD Nuclides

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  1. The Potential Importance of HTD Nuclides John W. Doroski

  2. Introduction • The potential importance of HTD nuclide monitoring (Effluents and REMP) • Need for Generic/Site Specific Position Papers • Audience Feedback

  3. Overview • Times are changing! • HTD nuclides may have “significant” dose and or Curie impacts Text Text Text Text Text Text Text Text Text

  4. Vocabulary • HTD – Hard to Detect (for this purpose, nuclides that are not detectable by gamma analysis or by liquid scintillation for H-3); Examples: Sr-89, Sr-90, Ni-63, Fe-55, C-14, P-32, transuranics, I-129, ….) Sometimes referred to as Difficult to Measure or DTM (see EPRI NP-3840, Project 1560-3, Environmental Radiation Doses for Difficult-to-Measure Nuclides)

  5. Why Not Considered? • NUREG-1301 & 1302 – minimal “requirements” for HTD (Sr-89&90 and gross alpha for liquids and airborne effluents, Fe-55 in liquid effluents only, none for REMP) • Regulatory Guide 1.21

  6. However! • NRC Inspection Module: Attachment 71122.01 (5/25/06 revision) • 10 CFR 20.1302 • NRC Regulatory Guide 1.109 • EPRI NP-3940 • Changes in source term (age of plants, processing system changes, etc.) • Public/Peer Reviews

  7. NRC Inspection Module: Attachment 71122.01 (5/26/06) • Primary reason for “update” is to address the spill, leak, … groundwater issue • Section 02.02g – This sentence was added: “Evaluate the source term used by the licensee to ensure all applicable radionuclides discharged, within detectability standards, are included.” • Section 03.01g – “The in-plant 10 CFR 61 file may provide some indication of predominant particulate radionuclides for potential release.”

  8. Recent NRC Inspections • NRC Region 1 inspector specifically mentioned our site needs a Position Paper for Ni-63 – Millstone (Fall of 2005) – due to “significant” amounts indicated in our 10CFR61 analyses • Similar issue at other plants (Peach Bottom)???

  9. 10 CFR 20.1302 • (a) the licensee shall make or cause to be made, as appropriate, surveys of radiation levels in unrestricted and controlled areas and radioactive materials in effluents released to unrestricted and controlled areas to demonstrate compliance with the dose limits for individual members of the public in 20.1301.

  10. NRC Regulatory Guide 1.109 • Regulatory Position (page 1.109-2): “In addition, other exposure pathways that may arise due to unique conditions at a specific site should be considered if they are likely to provide a significant contribution to the total dose. A pathway is considered significant if a conservative evaluation yields an additional dose increment equal to or more than 10 percent of the total from all pathways considered in this guide.”

  11. EPRI NP-3840 (January 1985) • “Important” DTM nuclidesestimated dose > 0.5 mrem/year • “Possibly important” DTM nuclides0.05 < estimated dose < 0.5 mrem/year • “Unimportant” nuclidesestimated dose < 0.05 mrem/year

  12. EPRI NP-3840 • Based upon a “model plant” • Important nuclides: C-14, Pu-238 & Cm-244 • Possibly Important Nuclides: P-32, Fe-55 and Cm-242 • Pathways (details in Table 5-4):Gaseous: all except P-32Liquid: P-32 & Fe-55

  13. Changes in Source Term • 10 CFR 61 data • Radmonitor comparisons (McGuire OE) • Liquid treatment changes • Material changes (e.g., S/G replacement) • Plant age • Other utility experiences (including outside US)

  14. Public/Peer Reviews • Example: Review of our REMP program by a University professor suggested measuring transuranics in seafood. • We followed up with a “one time” measurement • May be good idea to periodically do this (“negative” documentation is often useful)

  15. Site Specifics • Periodic review of 10 CFR 61 data • RCS/effluent isotopics (e.g., Fe-55 %) • HTD measurements for effluents • Dose evaluations

  16. Ni-63 • Levels in Radwaste (10CFR Part 61) • Levels in Liquid Effluents (as high as 30-40%) • Potential liquid doses (+3-4 % for 1st Q2006, “LADTAP”) • Potential airborne dose (worse than Co-60) • Therefore: likely needs to be added to our effluent program (at least periodically) and to REMP if detectable levels of ?? (e/g., Co-60) are measured in REMP samples

  17. Fe-55 • Levels in radwaste • If in liquids, why not in airborne? • Liquid doses – see following charts • Airborne doses - low • Therefore, for airborne effluents: document “conservative evaluation yields an incremental dose increment” less than 10 % of the “routine” dose calculations

  18. Relative Doses for Liquid Effluents – Primarily Fish and Shellfish Consumption

  19. Relative Doses for Liquid Effluents – Primarily Fish and Shellfish Consumption

  20. C-14 • This issue has been discussed at previous RETS-REMP Workshops, however the “rules” seem to be changing • Most of effluent is discharged via airborne pathway • Conservative dose calculation: 8 Ci/year results in doses of 0.5 mrem/year WB and 2 mrem organ (much greater than 10%) – maximum garden – same # in 1979 EPA report on C-14 (EPA 520/5-80-004) • UNSCEAR 2000

  21. Other HTD Nulides • P-32 – see EPRI NP-3840 • Transuranics – becoming limiting nuclides for worker airborne exposure at several decomissoned plants, what about older plants (is often limiting at our Unit 2), also see EPRI NP-3840Note: NUREG 1301 LLD for alpha several orders of magnitude too high!!!!!Some plants are showing measurable gross alpha activity

  22. REMP Implications • Purpose of REMP – verify the accuracy and adequacy of effluent monitoring program (had data for Co-58&60, Mn-54, I-131, Zn-65, Ag-110m, others? Why not Fe & Ni?) • H-3 & Fe-55 – often highest dose contributors (Ni-63?) – for liquids (lowered our H-3 LLD) • C-14 airborne – vegetation • NUREG 1301 – use site specific bioaccumulation factors

  23. Questions • Why are we so focused on top quartile for liquid effluents?– when doses in range of 0.002 mrem (2 reactors) for worst quartile! • Can we confidently say doses are 2e-3 mrem airborne when we can not measure transuranics below 1e-1 mrem? • What will the new DCF’s show? (see Stewart Bland’s presentation)

  24. Summary • Review what has been learned • Suggestions for additional monitoring and Position Papers – EPRI NP-3840 is “old” • Request audience feedback

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