2 Clearance measurements 1. Terminology 2. International scene 3. Development of clearance methodologies Instrumentation How to verify compliance to clearance level 4. Conclusions
3 Terminology ICRP - 60 1.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. Dir. 96/29 Third category: Work activities Presence of natural radiation sources. e.g. radon in dwelling e.g. Phosphate industry
4 Clearance, exemption and exclusion Radioactive source Regulatory control Residual material Clearance yes General clearance Specific clearance No radioactive waste management ExclusionExemption Different ways of avoiding regulatory resources being wasted for practices resulting in no benefit or nothing but a trivial benefit No reporting if < E.L. Consumer product not in nuclear fuel cycle No reporting due to nature natural radiation sources Destination defined
5 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.
6 Scenario ’s and pathways E.g. Metal scenario 2. Looks at the exposure pathway: ingestion inhalation external g radiation b-skin irradiation 1. Takes into account the entire sequence of scrap processing Transport & handlingconsumer goods … scrap yard, smelting or refinery manufacturing industry publicW: handling W+P: fume resuspended dust
7 Clearance level (Bq/g) 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 CL < EL RP 89 (metal scrap) + RP 113 (building rubble)
8 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: 1.a maximum individual dose/practice of about 10 µ Sv/year 2.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.
9 Need for international consensus 1. Transboundary movement 2. NORM industry 3. Car industry - waste industry
10 Transboundary movement General clearance: destination is not defined (Unconditional release) Specific clearance: traceability of the first step
11 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. NORM Nuclear
13 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).
14 Implementation of the council directive 96/29 in the Belgium legislation - clearance ‘ 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. ’ Annex 1B: art. 35: art. 18:
15 Implementation of the council directive 96/29 in the Belgium legislation - NORM 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) art. 4: art. 9: art. 20.3:
16 Grey zone… Zone of free interpretation by the competent authority RP 122 part I Nuclear 10 µSv/a RP 122 part II NORM 300 µSv/a !!! Exemption level (K-40 100 Bq/g) Exemption level Clearance level (K-40 1 Bq/g) Clearance level (K-40 oil-gas 100 Bq/g others 5 Bq/g) =
17 Trend… Full harmonization: Clearance = Exemption NORM = Nuclear One unique set of Clearance-exemption level Back to more Specificity Case by case clearance
18 Other consideration… Other risk health aspect : Chemical toxicity (industrial waste) Infectious risk Disposal: Management of materials should comply with the specific relevant regulations;
19 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”
20 Hot spot - Avergaging 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 C.L. x 10. Averaging value ?