Activity Report of TENORM Task Group

3. International Radiation Protection Concept for TENORM
3.1

ICRP

3.1.1 Exemption, Exclusion and Occupational Exposure for Natural Radiation
ICRP recommended the system of radiological protection in Publ.601). The system for
proposed and continuing practices is based on the general principles which are the justification ofa practice, the optimization of protection, and individual dose and risk limits. The types ofexposure are occupational exposure, medical exposure and public exposure. The system forintervention is based on the justification and the optimization.
In the Publ.60, ICRP defines that doses incurred in situations where the only available
protective action takes the form of intervention are excluded from the scope of the dose limits.
Radon in dwellings and in the open air and radioactive materials, natural or artificial, already inthe environment, are example of situations that can be influenced only by intervention.
ICRP also describes exclusion and exemption from regulatory control and the basis forthem in Publ.60.
In the Publ.75 “General Principle for the Radiation Protection of Workers”5), ICRP
recommends the control of occupational exposure to natural sources such as Radon at work andmaterials with elevated levels of natural radionuclides. ICRP recommends that the action level forintervention in workplaces should be applied to the effective dose and should be in the range 3-10
mSv in a year. As for materials with elevated levels of natural radionuclides, it is recommended
that regulatory agencies choose activity concentrations of parent nuclides within the range 1-10
Bq/g to determine whether the exposures from these materials should be regarded as occupational.
3.1.2 Existing Dose and Intervention Exemption Level
ICRP Publ.824) provides guidance on the application of the system of radiologicalprotection to situations of prolonged exposure to ionizing radiation. In this publication, ICRP
recommends the application of the system of radiological protection to practices resulting in
prolonged exposure and to intervention in prolonged exposure situations, generic reference levelsof existing annual dose for intervention, and application of the recommendations to specificprolonged exposure situations.
Generic reference levels for intervention, in terms of existing total annual doses, are given
as <100 mSv, above which intervention is almost always justifiable, and <10 mSv, below whichintervention is not likely to be justifiable. Intervention exemption levels for commodities,
especially building materials, are expressed as an additional annual dose of 1mSv. The dose limit
for exposures of the public from practices is expressed as aggregated additional annual doses fromall relevant practices of 1 mSv. Dose constraints for sources within practices are expressed as anadditional annual dose lower than 1 mSv (e.g. of 0.3 mSv), which could be 0.1 mSv for theprolonged exposure component. An exemption level for practices is expressed as an additional
annual dose of 0.01 mSv.

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3.2

IAEA

3.2.1

BSS (SS115)

International Basic Safety Standards (BSS) for Protection against Ionizing Radiation andfor the Safety of Radiation Sources published in 1996 as Safety Series No 115 of IAEA3) has been
widely introduced in the radiation protection policy in many countries. The principles of radiation
protection in the BSS are generally based on ICRP Publ.60. The principles on regulation ofTENORM are also mentioned in the BSS according to the policy of the ICRP recommendation.
The BSS shall apply to practices involving exposure to natural sources specified by theregulatory authority. The natural sources within the scope of the BSS include those related tomines, mills, processing radioactive ores and other source specified by the authority. Exposure tonatural sources shall normally be considered as a chronic exposure situation and shall be subjects
to the requirements for intervention except some cases of public exposure related to practices andoccupational exposure to radon. In the BSS, unmodified concentrations of radionuclides in most
raw materials are deemed to be excluded from scope of the standards. This means that every
material called as TENORM should be within the scope of the standards, if it can not be exempted.
BSS provided criteria for exemption from the requirements of the standards for the regulation aspractice. The exemption criteria is selected to be of order of 10µSv/y or less for the effective dosein any member of public and no more than 1 man·Sv of collective effective dose. In the BSS
exemption levels for both artificial and natural radionuclides are given which are derived by
calculation according to above criteria. The value for natural thorium or uranium is selected to be
1Bq/g and that for 40K is 100 Bq/g. Because these values were derived with calculation in a
scenario for a moderate quantity of material, BSS noted that unless the exposure is excluded,
exemption for bulk amounts of materials with activity concentrations lower than the exemption
levels given in the BSS may require further consideration by the regulatory authority.
3.2.2 RS-G-1.7 (DS161)
In IAEA, coherent system for the concepts of exemption, exclusion and clearance has been
discussed for a number of years. After IAEA was requested in the General Conference held in2000, to discuss the establishment of the level for radioactive concentrations for the smoothinternational trade of commodities by the some countries which territories were contaminated by
the Chernobyl accident, the Radiation Safety Standard Committee (RASSC) and the Waste Safety
Standards Committee (WASSC) started to discuss this issue. From the results of discussions overa period of more than 3 years, a document of draft safety guide (draft No. DS161), entitled“Application of the Concepts of Exclusion, Exemption and Clearance” was approved by theCommittees in March 2004 and published as Safety Series No. RS-G-1.76) in August 2004. The
exclusion levels for radionuclides of natural origin and the exemption levels for radionuclides ofartificial origin in bulk amount were provided in the document. As described above the exemption
level given in the BSS can be applied only to the exemption of moderate quantities of materials
which is considered to be less than 1 ton. Although the levels for artificial radionuclides werederived with calculation based on dose criteria of order 10 µSv/y for normal situation of exposure-6-

Activity Report of TENORM Task Groupand 1 mSv/y only for low probability events, those for natural radionuclides were derived using
the concept of “exclusion” prescribed in BSS. The values were selected on the basis ofconsideration of upper end of the worldwide distribution in soil reported in UNSCEAR. The valuefor 40K was selected to be 10 Bq/g and that for all other nuclides such as 238U and 232Th was 1
Bq/g. In relation to application of the values provided in the document, the values were selectedfor application to ordinary regulation of radioactive materials, to clearance level and to regulatory
control in national and international trade of commodities.
3.3 European Commission : Radiation Protection No. 122 Part II
The European Commission (EC) published the report as Radiation Protection No. 122 Part
II entitled “Practical use of the concepts of clearance and exemption (Part II) - Application of theconcepts of exemption and clearance to natural radiation sources-“in 20027). The objectives of thisreport are as follows;- application of the concepts of exemption and clearance to natural radiation sources, and- proposal of enveloping scenarios for establishing exemption and clearance values fornaturally occurring radionuclides.
The exemption levels in the BSS are not applied to the large volumes of material
processed and released by NORM industries, because they are derived only for moderatequantities (a few Mega-gram) of material. In the case of NORM industry, the amounts of material
to be considered are in general very large both for exemption and for clearance, contrary topractices for which clearance often relates to much larger volumes than exemption. For exemption
and clearance, where appropriate, the same levels should be used for naturally occurring
radionuclides.
RP 122 Part II deals with work activities. Work activities where the presence of naturalradiation sources leads to a significant increase in the exposure of workers or members of thepublic and the material is not used because of its radioactive, fissile and fertile properties.
Exposures by NORM industry are caused the following activities;- Product of a process- Re-use of by–product material- Disposal of solid waste- Recycling of scales deposited on steel pipes (oil & gas industry), and- Atmospheric or liquid discharges.
The derivation of exemption and clearance levels for NORM is carried out through theprocess shown in Fig. 1.

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Activity Report of TENORM Task Group

Choice of scenarios
Pathways of exposure
Choice of parameter values
Calculation of individual dose per 1 Bq/g
Identification of the limiting scenario & pathway
Reciprocal individual dose yield activity
concentrations corresponding to 300 μSv/yFig. 1 The Process of the Derivation of Exemption and Clearance Level for NORM
In the derivation of exemption and clearance levels the following enveloping scenarios areconsidered:- Transport over long/short distances (workers),- Disposal on a heap or a landfill (workers),- Person living in a house near a heap or landfill (members of the general public),- Transport over long/short distances,- Storage of moderate quantities, indoors,- Storage of large quantities, outdoors,- Road construction with NORM material,- Building construction with NORM containing building material,- Building construction using undiluted NORM as unshielded surface cover,- NORM as surface layer on public places/sports grounds,- Person living in a house with NORM containing building materials,- Person living in a house where undiluted NORM as unshielded surface cover is used,- External exposure to gamma emissions,- Inhalation of dust containing radioactivity,- Ingestion of material, and- Inhalation of 222Rn.

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Activity Report of TENORM Task Group

Groundwater pathway is also considered but the results are not reflected to set the levels,
because groundwater pathways largely depend on the site conditions. 222Rn concentration in air(Bq/m3) is calculated and is compared to the level of 200 Bq/m3 for members of the public and500 Bq/m3 for workers, respectively.
In the derivation of level the following materials are considered:- Waste rock,- Ash,- Sand,- Slag, and- Sludge from the oil/gas industry.
The EC concluded 300 µSv of annual effective dose increment is appropriate. For naturalradiation source (see Fig. 2) because 10 µSv/y would in general not be practicable to implement
control scheme and exemption-clearance levels for naturally occurring radionuclides should be set
at a higher dose level than for practices. Grounds of dose criterion are as follows:- Comparable to or smaller than regional variations in total effective dose from naturalradiation background (external exposure only),- Coherent with the exemption level proposed for building materials in EC RP 112, and- Coherent with dose constraint, e.g. control of effluents.
Total dose (=background + 0.3mSv/y)
Dose criterion
0.3mSv/yExtended dosecriterion

Background dosereduction

Original
Background dose

ReducedBackground doseFig. 2 Scheme for the Application of the Concept of Background Dose Reduction

Table 1 lists the nuclides and decay chains to be considered here. The 238U chain is assumed
to be in natural equilibrium with the 235U chain.

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Table 1 Summary of Nuclides and Chain Segments that are used in Modeling
ParentNuclides considered in secular equilibrium

Uranium decay chains
238

U sec

U nat

238

U , 234Th , 234Pa m, 234Pa (0.3%), 234U , 230Th , 226Ra , 222Rn ,Po , 214Pb , 214Bi , 214Po , 210Pb , 210Bi , 210Po
238
U , 234Th , 234Pa m, 234Pa (0.3%), 234U , 235U (4.6%),231Th(4.6%)
218

230

230

226

226

210

210

210

210

Th
Ra +Pb +Po

Th
Ra , 222Rn , 218Po , 214Pb , 214Bi , 214Po
Pb , 210Bi
Po

Actinium decay chains
235U sec

235

U , 231Th , 231Pa , 227Ac , 227Th (98.6%), 223Fr (1.4%), 223Ra ,219
Rn , 215Po , 211Pb , 211Bi , 207Tl , 211Po (0.3%)

235

235

231

231

U+Pa

227

Ac +U , 231Th
Pa

227

Ac , 227Th (98.6%), 223Fr (1.4%), 223Ra , 219Rn , 215Po , 211Pb ,211
Bi , 207Tl , 211Po (0.3%)

Thorium decay chains232

Th sec232

Th , 228Ra , 228Ac , 228Th , 224Ra , 220Rn , 216Po , 212Pb , 212Bi ,Po (64.1%), 208Tl (35.9%)

212

232

232

228

228

Th
Ra +

228

Th +ThRa , 228Ac

228

Th , 224Ra , 220Rn , 216Po , 212Pb , 212Bi , 212Po (64.1%), 208Tl(35.9%)

40

K

40

K

40

K

sec: Parent nuclide with their decay products which are in secular equilibrium.
+ : Parent nuclide with their decay products listed in right column which are in equilibrium.
nat: 238U sec and 235Usec in their fixed natural ratio.

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Activity Report of TENORM Task GroupIn Table 2 the recommended rounded general clearance and exemption levels for all typesof material are given. An additional column in Table 2 gives the (considerably higher) values only
applicable for wet sludge from the oil and gas industry. The general clearance and exemption
values for all materials are very much lower than those for wet sludge from oil and gas industry,essentially because the suspension/inhalation pathway can be ignored.
Table 2 Rounded General Clearance Levels in kBq/kgNuclideAll materials

U sec incl. 235U sec

0.55U nat

5100230

10100

226

0.5521051002105100235

1102355502315502271102320.55232

5100228

110228Th +0.55405100238

Th
Ra +
Pb +
Po
U sec
U+
PaAc +Th secThRa +
K

Wet sludges from oil and gas industry[Note] * For radionuclides considered to be in secular equilibrium see Table 1** 238U sec and 235U sec are in their fixed natural ratio (99.275 and 0.72 % atomic fraction)*** Separate values for radionuclides of 235U series are given here only for information. For NORM
these values are never limiting as 238U and 235U are always in their fixed natural ratio.

As a result of the large volumes of material processed and released by NORM industries,
the concept of exemption and clearance are merged in this report and a single set of levels both for
exemption and clearance is appropriate. Dose criteria for work activities are 300 µSv/y isappropriate and 0.5 Bq/g for U and Th in secular equilibrium is derived. This level iscorresponding to the upper range of concentrations usually found in ores. Therefore, regulatory
control for NORM is practicable by using these levels. The 222Rn concentrations were calculated
based on the minimum value of all exemption/clearance levels for 226Ra+ for each type of material.
The calculation results show the radon concentrations are below 200 Bq/m3 for members ofgeneral public and 500 Bq/m3 for workers for all exposure scenarios. There is possibility ofcontamination of groundwater as drinking water; the evaluation of doses is necessary case by case.

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