U S LowLevel Radioactive Waste Classification System 10
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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
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 2
Applicability of 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. 3
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. 4
Radionuclides Considered in the Waste Source 5
Intruder Normal Activities Scenarios Dwelling Construction Drilling for Water Agriculture 6
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, 6 th 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). 7
10 CFR 61. 55 Waste Classification Tables 1 & 2 8
IAEA GSG-1 Generic Waste Classification Scheme and Illustrative Examples of Waste Categories for Sealed Sources 9
Example Half-life Activity Volume i <100 d 100 MBq Small ii <100 d 5 TBq Small iii <15 a <10 MBq Small iv <15 a <100 TBq Small v <30 a <1 MBq Small vi <30 a <1 PBq vii >30 a <40 MBq viii >30 a <10 GBq Small Example Waste Class Y-90, Au-198 VSLW (brachytherapy) Ir-192 VSLW (brachytherapy) Co-60, H-3 LLW (tritium targets), Kr-85 Co-60 LLW (irradiators) Cs-137 LLW (brachytherapy, moisture density detectors) Cs-137 ILW (irradiators) Sr-90 (thickness gauges, RTGs) Small, but may be large numbers of sources Pu, Am, Ra (static eliminator) Am-241, Ra-226 (gauges) Example of Disused Sealed Sources Classes Based on IAEA GSG-1 ILW 10
International Atomic Energy Agency Waste Categories U. S. NRC Waste Categories High Level Waste Intermediate Level Waste Greater-than-Class C LLW Low Level Waste (LLW) Class A, Class B and C LLW A portion of GTCC? Very Low Level Waste Class A Very Short Lived Waste Material held for decay storage Exempt Waste Liquids/Air: Effluent releases Solids: Case-by-case analysis Comparison of IAEA Waste Management Categories with U. S. 11
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 sitespecific analysis. 12
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 m. Sv/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. 13
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. 14
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. 15
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 16
10 CFR Part 61 Waste Acceptance Criteria • Allowable Limits on Radioactivity • Waste-form Characteristics and Container Specifications • Restrictions and Prohibitions Draft NUREG-2175 17
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. 18
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 riskinformed, 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. 19
Backup Slides 20
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 http: //www. nrc. gov/about-nrc/regulatory/rulemaking/potential-rulemaking/uwstreams. html 21
10 CFR Part 61 Dose Impact Calculation • The scenarios employ common expressions for dose equivalent, H (mrem): – H = ∑i, j PDCF x Ca, where: – – PDCF ≡ Pathway Dose Conversion Factor, (mrem per Ci/m 3) – Ca ≡ [Radionuclide]access point, (Ci/m 3) – – i ≡ Radionuclide index j ≡ Pathway index 22
Dose Impacts Calculations (Cont’d) – – Ca = I x Cw, where: Cw ≡ [Radionuclide]waste, (Ci/m 3) 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, (-) 23
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