Chapiter 7 (part II-1) Isabelle Majkowski SCK●CEN Isabelle Majkowski, SCK●CEN and chapter 7
Clearance measurements • 1. Terminology • 2. International scene • 3. Development of clearance methodologies • Instrumentation • How to verify compliance to clearance level • 4. Conclusions
Terminology • ICRP - 60 • Practice: • Nuclear fuel cycle • Exemption & Clearance • 2. Intervention: • Materials contaminated as a result of past practices which f.i. were not subject to regulatory control for any reason (e.g. military applications) or which were contaminated as a result of an accident. e.g. Phosphate industry Dir. 96/29 Third category: Work activities Presence of natural radiation sources. e.g. radon in dwelling
Clearance, exemption and exclusion Different ways of avoiding regulatory resources being wasted for practices resulting in no benefit or nothing but a trivial benefit Radioactive source No reporting if < E.L. Consumer product not in nuclear fuel cycle No reporting due to nature natural radiation sources Exclusion Exemption Regulatory control Residual material yes No Clearance radioactive waste management General clearance Specific clearance Destination defined
Specific Clearance Level >General Clearance Level • General Clearance Level: • Destination NOT defined. • Most restricted values – set of CL in RP 122. • Specific Clearance Level: • Destination defined – clear the material for a particular use. • Only the first step of clearance is defined (concept of clearance = release from regulatory control – no traceability) • Impact analyses – demonstrate through scenarios of exposure that the dose impact is acceptable for a health point of view • Specific clearance pathway should be recognised and approved by the regulatory authorities.
Scenario ’s and pathwaysE.g. Metal scenario 1. Takes into account the entire sequence of scrap processing Transport & handling scrap yard, smelting or refinery consumer goods manufacturing industry … 2. Looks at the exposure pathway: ingestion inhalation external g radiation b-skin irradiation W+P: fume resuspended dust W: handling public
Clearance level (Bq/g) CL < EL RP 89 (metal scrap) + RP 113 (building rubble) • Criterium 10 µSv/a: • Choice of scenarios • Pathway of exposure • Choice of parameter values • Calculation of individual doses per unit activity concentration • Identification of the limiting scenario and pathway • Reciprocal individual doses yield activity concentrations corresponding to 10 µSv/a, rounded to a power of ten. • Criterium 1 manSv/a: • Takes into account the number of people exposed. • For each radionuclide CL leads to collective dose <<< 1 manSv
Aim of recommendations: minimise the radiological risks to workers and public • The Safety Series N°89 that was issued jointly by the IAEA and the OECD-NEA in 1988 suggests: • a maximum individual dose/practice of about 10 µ Sv/year • a maximum collective dose/practice of 1 manSv/year • to determine whether the material can be cleared from regulatory control or if other options should be examined.
Need for international consensus 1.Transboundary movement 2. NORM industry 3. Car industry - waste industry
Transboundary movement General clearance: destination is not defined (Unconditional release) Specific clearance: traceability of the first step
Nuclear NORM B B Bq Bq NORM industry Naturally Occurring Radioactive Material Phosphate industry - Oil industry. • Activity levels in NORM industry ~ very low level waste. But quantities are much higher. • Strong campaign to regulate exposure to workers and public from both nuclear and Non-nuclear industries under the same radioprotection criteria.
International / EU recommendations and guidelines IAEA guidelines and recommendations • Safety Series No. 89 (Principles for the exemption of radiation sources from regulatory control) • IAEA TEC DOC 855 recommends a set of unconditional clearance levels (in solid material). Council directive 96/29 EURATOM • had to be implemented in national legislation by May 2000 - (few months ago) • does not prescribe the application of clearance levels by competent authorities. • RP N°89: Guidance on the recycling or reuse of metals. • RP N°113: Guidance for the clearance of building and building rubble • RP N°122: Practical use of the concepts of clearance and exemption (recommendations of the Group of Experts established under the terms of Article 31 of the Euratom Treaty).
Implementation of the council directive 96/29 in the Belgium legislation - clearance Annex 1B: art. 35: art. 18: ‘ Set of Clearance level ’ ~ CL in RP 122’ • Concentration Activity Level < CL (1B) • measurement procedures conform to the Agency directives or approved by the Agency (and by C.P) • (1st of march, list of released material to ONDRAF and Agency) Solid waste from nuclear installation of class 1, 2 or 3 or natural sources under art 9 that does NOT satisfy CL (given in annex 1B) request an authorisation by the agency. ’
Implementation of the council directive 96/29 in the Belgium legislation - NORM art. 4: art. 9: art. 20.3: Defines 3 groups of professional activities using Natural Sources (exposure to the daughter products of Radon - underground, Exposure risk, ingestion and inhalation risk to natural sources - phosphate, air craft industry) Declaration - decision - authorisation Level • Exposition of workers and public to radon: • effective dose > 3 mSv/year • annual exposition to radon > 800 kBq.m-³.h • Natural source • effective dose >1 mSv/year (worker) • dose public > general dose limit for the public. • Air craft industry • 1 mSv/year (worker)
Zone of free interpretation by the competent authority Grey zone… =
Trend… Full harmonization: Clearance = Exemption NORM = Nuclear One unique set of Clearance-exemption level Back to more Specificity Case by case clearance
Other consideration… • Other risk health aspect: • Chemical toxicity (industrial waste) • Infectious risk • Disposal: • Management of materials should comply with the specific relevant regulations;
Forbidden practices ‘Deliberated dilution with non radioactive material to reach the clearance level is forbidden’ RP 122 part I: “two factors generally lead to mitigate the radiological risk as time passes: • spontaneous or technological dilution • radioactive decay”
Hot spot - Avergaging value Averaging value ? Specific clearance: • Metal: total activity is averaged over a few 100 kg (or several 100 cm²). • building for reuse or demolition: tot A. in the structure/surface – max averaging value = 1 m² • buildings for demolition only: • building rubble resulting from demolition: Bq/g • or, clear the standing structure and then demolish: tot A. in the structure/surface • building rubble: • remove surface contamination & measure the rest in Bq/g • max averaging value = 1 Mg – if < 100 Tonnes/year -> C.L. x 10.