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Boby Abu-Eid, Ph.D. SLS Advisor Division of Decommissioning, Uranium Recovery and Waste Programs

U.S. Low-Level Radioactive Waste Classification System 10 CFR Part 61 - Basis, Updates, and Issues. Boby Abu-Eid, Ph.D. SLS Advisor Division of Decommissioning, Uranium Recovery and Waste Programs U.S. Nuclear Regulatory Commission April 17, 2019 LLW Forum Meeting –Alexandria, VA.

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Boby Abu-Eid, Ph.D. SLS Advisor Division of Decommissioning, Uranium Recovery and Waste Programs

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  1. U.S. Low-Level Radioactive Waste Classification System 10 CFR Part 61 - Basis, Updates, and Issues Boby Abu-Eid, Ph.D. SLS Advisor Division of Decommissioning, Uranium Recovery and Waste Programs U.S. Nuclear Regulatory Commission April 17, 2019 LLW Forum Meeting –Alexandria, VA

  2. Topics • Applicability and Basis of LLW Classification under 10 CFR Part 61: • Applicability • Waste class limits under §61.55 Tables 1&2 • Comparison with International waste classification (e.g.; GSG-1) • Waste classes limits and NRC ongoing activities: • Site-Specific Analysis & Waste Acceptance Criteria • Alternative Disposal Requests • VLLW • GTCC • Key Issues, Summary, and Conclusion

  3. Applicability of 10 CFR Part 61 10 CFR Part 61 (Licensing Requirements for Land Disposal of Radioactive Waste): • Applies to Radioactive Waste (RW) containing byproduct, source, and special nuclear material (SNM). • Doesn’t apply to: HLW, Transuranic (TRU), Spent Nuclear Fuel (SNF), U/Th tailings, and licensed byproduct material under 10 CFR 20.1003. • Waste containing radionuclides exceeding §61.55 Table 1 limits or limits in Table 2, Column 3, (designated GTCC) are not generally acceptable for near surface disposal.

  4. Basis of 10 CFR Part 61 Tables 1 & 2 Limits: Approach & Methodology • Set protection limits; derive scenarios for exposure; perform inverse calculations, and apply other factors to modify derived concentrations. • Waste classification tables were based on a 500 mrem (whole-body) exposure or other specific organ dose limits. • NUREGs-0782/0945 primarily considered two concentration-limited and one activity-limited intruder scenarios. • Concentration Limited Scenarios: Intruder-Construction (acute); and Intruder-Agriculture (chronic). • Common assumptions include: (a) institutional controls breakdown temporarily; (b) inadvertent intruder directly contacts waste; (c) intrusion occurs into last disposal cell constructed, and (d) waste remains locally dispersed.

  5. Radionuclides Considered in the Waste Source

  6. Intruder Normal Activities Scenarios Dwelling Construction Drilling for Water Agriculture

  7. Dose Conversion Factors (DCFs) Calculations • Intruder Construction PDCFs: NUREG-0782, Tables G.4 and G.7 • Intruder Agriculture PDCFs: NUREG-0782, Tables G.5 through G.7 • Calculated in NUREG/CR-1759 (1981), Vol. 3, App. B • DCFs • Inhalation DCFs from Health Physics 12, 173 (1966) and ICRP 19 (1972). • Ingestion DCFs from Reg. Guide 1.109, Rev.1 (1977) and NUREG-0172 (1977). • Direct gamma (volume) DCFs calculated from equations in HASL-195 (1968) with emitted gamma energy characteristics in Table of Isotopes, 6th Ed. (1967). • Direct gamma (air) DCFs are from NUREG-0456 (1978). • No dilution of I-129 with natural iodine. • All of above use dosimetry from ICRP 2 (1959).

  8. 10 CFR 61.55 Waste Classification Tables 1 & 2

  9. IAEA GSG-1 Generic Waste Classification Scheme and Illustrative Examples of Waste Categories for Sealed Sources

  10. Example Half-life Activity Volume Example Waste Class i<100 d 100 MBq Small Y-90, Au-198 VSLW (brachytherapy) ii <100 d 5 TBq Small Ir-192 VSLW (brachytherapy) iii <15 a <10 MBq Small Co-60, H-3 LLW (tritium targets), Kr-85 iv <15 a <100 TBq Small Co-60 LLW (irradiators) v <30 a <1 MBq Small Cs-137 LLW (brachytherapy, moisture density detectors) vi <30 a <1 PBq Small Cs-137 ILW (irradiators) Sr-90 (thickness gauges, RTGs) vii >30 a <40 MBq Small, but may Pu, Am, Ra (static ILW be large number eliminator) viii >30 a <10 GBq large numbers of Am-241, Ra-226 ILW sources (gauges) Example of Disused Sealed Sources Classes Based on IAEA GSG-1

  11. Comparison of IAEA Waste Management Categories with U.S.

  12. Waste Class Limits:Site-Specific Analysis New limits based on site-specific analysis could be established based on: • Use of different dose conversion factors • Use of site-specific exposure scenarios • Use of site-specific physical input parameters • Use of updated models/codes • Use of risk-informed probabilistic approach (inputs & results) • All of above would lead to different waste acceptance criteria • Limits established in Tables I & II wouldn’t be applicable to site-specific analysis.

  13. Waste Class Limits:Alternative Disposal Request (ADR) Reviews • ADR for disposal of licensed materials of usually low-activity and quantity waste under 10 CFR 20.2002. • §20.2002 does not have specific dose limits. However, NUREG-1757, Vol. 1 Section 15.12 refers specifically to on-site disposal of 0.05 mSv/y (5 mrem/y) and use of risk-informed probabilistic approach using updated dosimetry and models. • Licensees may request approval for disposal of waste off-site under § 20.2002 in a landfill. The derived radionuclide concentrations and inventories may represent a significant fraction of Class A lower limits. • Exempt waste category and/or conditional clearance materials may be disposed under ADR using site-specific analysis on a case-by-case bases. • Based on safety criteria only, a fraction of Class A waste may disposed under ADR.

  14. Waste Class Limits:Very Low-Level Waste (VLLW) Scoping Study • IAEA GSG-1 defines VLLW as: • Waste that does not meet the criteria of exempt waste, but does not need a high level of containment and isolation, and, therefore, is suitable for disposal in a near surface landfill type facility with limited regulatory control. • The NRC currently does not have a formal regulatory definition for VLLW. • Options that may be considered in the VLLW Scoping Study: (a) limited scope rulemaking; (b) developing guidance specific to VLLW including modifying the ADR guidance; and (c) status quo. See also 83 Fed. Reg. 6619.

  15. Waste Classes Limits: GTCC • GTCC LLW is defined based on the upper limits of Class C waste. • Licensees or applicants may request on a case-by-case approval (61.55(a)(2)(iv) using similar methodology to Part 61, but using updated DCFs, models, scenarios and probabilistic analysis approach; • Site-specific analysis may result in different case-by-case approved GTCC volumes/inventories because of site differences; • NRC is currently evaluating whether some or all of GTCC can be disposed in the near surface. A draft regulatory basis is planned to be issues in the next few months.

  16. Waste Acceptance Criteria • Licensees would review their waste acceptance program at least annually • Ensures that the program continues to be adequate and is being implemented in a way that continues to protect public health and safety Draft NUREG-2175

  17. 10 CFR Part 61 Waste Acceptance Criteria • Allowable Limits on Radioactivity • Waste-form Characteristics and Container Specifications • Restrictions and Prohibitions Draft NUREG-2175

  18. Key Issues in 10 CFR Part 61 Classification • Considering a generic LLW disposal facility concentration limits in Tables 1 and 2 that are not up-to-date because they are: • Based on superseded dosimetry ICRP 2 (1959) • Based on superseded models/codes, and software • Based on risk to intruder using deterministic approach • Considered disposal options under the stringent Part 61 requirements for all waste, no lower limits for exemptions, clearance, or short-lived nuclides • 10 CFR Part 61 did not consider certain waste streams such as DU , • International “Waste Acceptance Criteria” is typically based on site -specific analysis. • However LLW disposal sites under Part 61 are protective and safe.

  19. Summary & Conclusion • Current LLW classification system has provided adequate safety measures; however, there are several potential enhancements. • The concept of deriving waste classes limits based on a generic site with stringent requirements for all waste categories continues to be useful, but alternate risk-informed, performance-based approach could be viable. • ADR process allows for disposal of waste onsite or in RCRA facilities. • NRC is currently evaluating whether some or all of GTCC waste can be disposed of in a near surface facility. • The concept that GTCC waste cannot be disposed, on generic basis, in a land disposal facility should be revised. • The proposed Part 61 rulemaking has made changes to the rule that may allow use of site-specific waste acceptance criteria. • The Commission has directed staff to change the definition of LLW to be consistent with the 1985 Low-Level Waste Policy Act Amendments.

  20. Backup Slides

  21. Site-Specific Analysis • NUREG-2175 (Guidance for Conducting Technical Analyses for 10 CFR Part 61) provides: • Flowcharts, NRC staff recommendations, and examples for how licensees can develop high-quality technical analyses • Guidelines for what licensees or applicants should include and what regulators should review for each type of analysis • Suggested references, screening tools, and case studies • DRAFT final version made publically available in ADAMS and on the public website

  22. 10 CFR Part 61 Dose Impact Calculation • The scenarios employ common expressions for dose equivalent, H (mrem): • H = ∑i,jPDCF x Ca, where: • PDCF ≡ Pathway Dose Conversion Factor, • (mrem per Ci/m3) • Ca≡ [Radionuclide]access point, (Ci/m3) • i ≡ Radionuclide index • j ≡ Pathway index

  23. Dose Impacts Calculations (Cont’d) • Ca = I x Cw, where: • Cw≡ [Radionuclide]waste, (Ci/m3) • I = fo x fd x fw x fs, where: • I ≡ Interaction Factor, (-) • fo ≡ Time-delay factor, (-) • fd ≡ Site design and operation factor, (-) • fw ≡ Waste form and package factor, (-) • fs ≡ Site selection factor, (-)

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