Data analysis

35 Invited Paper

CHALLENGES IN IMPLEMENTING THE CHANGE IN

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standards has been unnecessarily complicated and confusing, giving rise to misunderstandings and differences in the interpretation of the standards, mainly in basic and essential concepts.

New International Basic Safety Standards were published quite recently by the IAEA [3]

and have been implemented within the European Union through a new European Council Directive [4]. The requirements set out in the new Directive are in line with the 2007 Recommendations of the ICRP [5]. In particular, the three types of exposure situations specified by the ICRP (planned exposure situations, existing exposure situations and emergency exposure situations) are reflected in the structure of the new standards. Exposure to natural sources continues to be generally subject to the requirements for existing exposure situations but exposure control, rather than being based on the use of action levels as in the past, is now based on the use of so-called reference levels. Only a few exposures to natural sources are, by exception, subject to the requirements for planned exposure situations. The main example in this regard is exposure to material (other than commodities such as food, drinking water, fertilizer and construction material) with a radionuclide concentration exceeding 1 Bq/g for the U and Th decay series or 10 Bq/g in the case of ⁴⁰K — in other words, exposure to NORM. In addition, for the first time, numerical criteria for exemption and clearance of NORM have been included, with exemption being determined on the basis of dose commensurate with the natural background (about 1 mSv/a) and clearance being determined on the basis of activity concentration (1 Bq/g for U and Th series radionuclides and 10 Bq/g for ⁴⁰K). Also, as in the previous standards, exposures that are unamenable to control are excluded from the scope of the new standards. This is particularly important in the case of natural sources, because it leads to the exclusion of exposures such as to ⁴⁰K in the body, cosmic radiation at the surface of the earth and exposure associated with undisturbed terrestrial areas.

More specifically, the requirements for existing exposure situations should be applied to the following exposures to natural sources: exposure to radon in homes and in most workplaces, exposure to commodities (including food, feed, drinking water, agricultural fertilizer and soil amendments, and construction material) irrespective of the activity concentrations, exposure to residual radioactive material in the environment irrespective of the activity concentration, exposure from past activities that were not regulated and exposure to any other material provided that its radionuclide activity concentration does not exceed 1 Bq/g for each radionuclide of the ²³⁸U and ²³²Th series and 10 Bq/g for ⁴⁰K.

Only exceptionally are there some human activities where exposure to natural sources should be controlled in accordance with the requirements for planned exposure situations. They are the following: (a) Exposure to material — other than food, drinking water, agricultural fertilizer and soil amendments, construction material, and existing residues in the environment

— where the activity concentration in the material of any radionuclide in the uranium and thorium decay chains is greater than 1 Bq/g or the activity concentration of ⁴⁰K is greater than 10 Bq/g (such material being defined as NORM); (b) public exposure delivered by effluent discharges or the disposal of radioactive waste arising from the facilities concerned, irrespective of their activity concentrations; (c) Occupational exposure to radon, irrespective of the concentration, in situations where the exposure to other U and Th series radionuclides is controlled (as a planned situation); (d) Occupational exposure to radon in situations where the concentrations remain above the reference level after remedial action has been carried out.

3. CHALLENGES FOR REGULATION OF NORM

It seems evident that the new European Directive will provide greater clarity on the control of exposure to natural sources although its application will be far from being a trivial task, with several unavoidable remaining challenges for proper implementation in the NORM industry. Such challenges include the following:

37 (1) The requirements in the new Directive for existing exposure situations include the concept of ‘reference levels’, which are defined as levels of dose or risk above which it is judged to be inappropriate to plan to allow exposures to occur, and below which optimization of protection should be implemented. The reference level approach replaces the ‘action level’ approach in the previous Directive — action levels were defined as the levels of dose rate or activity concentration at or below which remedial action or optimization was not normally necessary. With the new Directive, some effort should be made for the proper implementation and full understanding of this ‘reference level’

approach. The tendency observed in the first months of implementation of the new Directive to simply interchange the concepts of action levels and reference levels (thinking that the change is merely one of terminology) should be properly corrected. The

‘reference levels’ sometimes have been used as limits, defeating the purpose of optimization.

(2) It is clear that the control of exposure to NORM in industrial activities should be performed in accordance with the requirements for planned exposure situations, in the same way as the control of public exposures due to release or disposal of wastes generated in NORM industries. This control must fulfil one of the key principles in the Directive — it should be commensurate with the characteristics of the practice or the source and with the magnitude and likelihood of exposures. In the case of NORM industries, this is particularly relevant because the exposures are generally (but not always) moderate with little or no likelihood of extreme radiological consequences from accidents. This philosophy of the graded approach to regulation is maintained unchanged in the new Directive, following the principle of optimization of protection. The only important difference from the previous Directive is that numerical criteria have been introduced for the basic concepts of exemption and clearance. In particular, where a radionuclide has an incidental presence, and where bulk quantities of material may be involved (as in many NORM activities), the new Directive makes provision for exemption using a dose criterion of about 1 mSv/a commensurate with natural background levels, as well as for clearance using criteria expressed as activity concentrations not exceeding 1 Bq/g for uranium and thorium series radionuclides and 10 Bq/g for ⁴⁰K. In this sense, a continuous didactic dissemination of the basic concepts of exclusion, exemption and clearance is needed, because they are being applied confusingly or wrongly by a non-negligible fraction of the parties involved in radiation protection for NORM.

(3) In some cases, there are situations where doubts can appear about which type of requirements (for planned or existing exposure situations) should be implemented. By default these cases should be treated as existing exposure situations and only in exceptional cases as planned exposure situations, following the philosophy of the European Directive that treats the great majority of exposures to natural sources as existing exposure situations.

(4) Obviously, although standards have been developed for the NORM industry in general without exceptions, it is clear that individual NORM industries are very different as are the practical radiation protection challenges they face. No single approach is appropriate for all NORM industries or for all industrial processes. The idea of a common protocol to control the exposures in all the NORM industries, i.e. a uniform approach to regulation of NORM, should be disregarded in favour of an industry specific approach. The importance of this point is reflected in the publication of the ‘positive list’ of industries proposed for Europe and (in the IAEA industry-specific publications in the Safety Reports Series) worldwide.

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(5) Through the individual studies performed in NORM industries it is clear that, in most of the workplaces of NORM industries, worker doses are less than 1 mSv/a and the majority of studies that have been published or presented in various international conferences have concentrated on the determination of individual doses in order to establish whether there is a need for regulatory control. Only in a very limited number of cases has information been provided on how such doses might then be optimized in practice. Additional detailed studies should be performed in NORM workplaces where optimization of doses is needed, devoting special emphasis to the evaluation of possible alternative approaches to decrease the occupational doses in practice.

(6) On the other hand, it is interesting to note that methodologies for the realistic assessment of worker doses suffer from non-standardized approaches. There is therefore a need to plan how such standardization can be achieved. The emphasis should be on actual monitoring data (individual and workplace) to ensure that the dose estimates are realistic, rejecting the approaches based on theoretical models.

(7) A key issue associated with the application of the new regulations in NORM activities is the legacy issue. Many NORM related industrial sites were abandoned in the past with little or no remediation and inefficient residue management. Such sites may include tailings facilities, fertilizer plants, thorium gas mantle factories, metal refineries and old oil production fields. Many of these legacy sites, including those in the vicinity of urban areas, now need remediation. In terms of the European Directive, the requirements for existing exposure scenarios must be applied. This poses the challenge of establishing coordinated international efforts for remediation. The goal of the remedial actions must be the timely and progressive reduction of the hazard and eventually, if possible, the removal without restrictions of regulatory control from the area. The nature and extent of remedial actions must be commensurate with the risks associated with the existing exposure, and must be justified in the sense that they do more good than harm. The form, scale and duration of the remedial actions must be optimized so as to produce the maximum net benefit and must be selected from a set of justified options for remediation.

The optimized protection actions must be implemented with the objective of reducing doses to below the reference level. However, in terms of the new reference level approach, this is no longer sufficient. Exposures below the reference level must not be ignored and possible reductions in such exposures need to be investigated to ensure that the remedial actions are optimized.

(8) Another important issue in NORM industries is the management of NORM residues (including those designated as NORM waste). This management is not a simple task, since such residues can be generated in a variety of forms, including solids in small quantities (scale, sludge, tailings, slag), solids in large quantities (mine tailings, waste rock piles, by-product piles), liquids (spent process water, spent solvents) or gases (from high temperature processes). NORM residues should be managed in accordance with the basic principles embodied in the European Directive. For some NORM industries, especially those producing low or medium volume residues with higher activity concentrations, disposal as waste in a suitable repository may be the only solution. In recent years, it is becoming increasingly accepted that these NORM residues may be disposed of in a manner similar to that for other hazardous wastes, rather than in facilities designed for the disposal of high activity radioactive waste containing artificial radionuclides. However, the problem is still the lack of suitable facilities that are prepared to accept NORM waste.

(9) For residues with moderate concentrations of radionuclides, there is increasing acceptance of recycling or use of such residues as by-products, rather than disposal as waste. The opportunity for recycling or by-product use of a NORM residue depends on a variety of factors such as the type of residue, the rate and place of generation and the local

39 market conditions, taking into account factors such as acceptability to the public, the existence or otherwise of uniform approaches to recycling and concerns about radon exposure in the case of building materials. For that reason, the recycling of these residues should be based on prior detailed assessments based on experimental studies to determine the potential health, environmental and radiological impacts of the product generated, as well as on assurances that the recycled residue will have the necessary characteristics and behaviour for the application in question.

4. CONCLUSIONS

The number and magnitude of the challenges summarized in the paragraphs above can be considered as quite important, but the writer, having been involved in NORM for more than 20 years, wishes to conclude by indicating that the actual situation of radiation protection in the NORM industry can be regarded with optimism. The experience gained in the field has been considerable and the regulations are becoming increasingly clear and properly applied. The challenges described in this paper are those that remain after having taken a good number of steps in the right direction. We are fortunate enough to be far from the initial erratic and chaotic situation that existed with respect to the application of NORM regulations some years ago, and are approaching the desired degree of maturity where radiation protection is a well established subject that can be handled routinely by NORM industries.

REFERENCES

[1] FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, WORLD HEALTH ORGANIZATION, International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, IAEA Safety Series No. 115, IAEA, Vienna (1996).

[2] COUNCIL OF THE EUROPEAN UNION, Council Directive 96/29/Euratom of 13 May 1996 laying down basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionizing radiation, Official Journal of the European Communities, L 159, vol. 39 (1996).

[3] EUROPEAN COMMISSION, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANIZATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, WORLD HEALTH ORGANIZATION, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA Safety Standards Series No. GSR Part 3, IAEA, Vienna (2014).

[4] COUNCIL OF THE EUROPEAN UNION, Council Directive 2013/59/Euratom of 5 Dec 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, Official Journal of the European Communities, L13, vol. 57 (2014).

[5] INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, The 2007 Recommendations of the International Commission on Radiological Protection, Publication 103, Elsevier, Amsterdam (2007).

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Poster Presentation

RADIOLOGICAL RISK CLASSIFICATION OF