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Chapiter 7 (part II-1)

Isabelle Majkowski

SCK●CEN

Isabelle Majkowski, SCK●CEN and chapter 7

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Clearance measurements

1. Terminology

2. International scene

3. Development of clearance methodologies

Instrumentation How to verify compliance to clearance level

4. Conclusions

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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 indwelling

e.g. Phosphateindustry

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Clearance, exemption and exclusion

Radioactivesource

Regulatory control

Residual material

Clearanceyes

General clearanceSpecific clearance

No

radioactive waste

management

Exclusion Exemption

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

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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.

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Scenario ’s and pathwaysE.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 & handling consumer goods

…

scrap yard, smelting or refinery

manufacturing industry

publicW: handling W+P: fume

resuspended dust

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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)

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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.

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Need for international consensus

1. Transboundary movement

2. NORM industry

3. Car industry - waste industry

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Transboundary movement

General clearance:destination is not defined(Unconditional release)

Specific clearance:

traceability of the first step

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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

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Car industry

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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).

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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:

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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:

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Grey zone…

Zone of free

interpretation

by the competent

authority

RP 122 part INuclear10 µSv/a

RP 122 part IINORM300 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)

=

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Trend…

Full harmonization:Clearance = ExemptionNORM = Nuclear

One unique set ofClearance-exemption level

Back to more Specificity

Case by case clearance

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Other consideration…

Other risk health aspect:

Chemical toxicity (industrial waste)

Infectious risk

Disposal:

Management of materials should comply with the specific relevant regulations;

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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”

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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 < 100 Tonnes/year -> C.L. x 10.

Averaging value ?