Comments on the draft report for consultation: Radiological Protection from Naturally Occurring Radioactive Material (NORM) in industrial processes
Joint comments from the Dutch National Institute for Public Health and the Environment (RIVM) and the Dutch Authority for Nuclear Safety and Radiation Protection (ANVS)
RIVM: T. van Dillen, E. Folkertsma, C.P. Tanzi, and R.C.G.M. Smetsers;
ANVS: P.C. Görts and F.H.M.M. van de Put.
Part 1: General remarks
This publication elaborates on how to apply the situation-based system of radiological protection from ICRP Publication 103 (the ICRP-103 recommendations, 2007) to the industry involving naturally occurring radioactive materials (NORM), i.e., to the management of NORM in industrial processes. The global importance, large abundance, and variety of NORM industrial processes indeed call for international consensus on a proper system of radiological protection for NORM management (para. 10). That system should rely on the basic ethical values and concepts, and take into account (besides health considerations) economic and societal factors under the prevailing circumstances. RIVM and ANVS appreciate ICRP’s efforts to recommend such a system, as the proposed guidance would harmonize the approach to deal with the various exposures related to sources containing natural radionuclides (i.e., industry involving NORM versus: building materials, drinking water, radon etc.). Such consistency would in principle be of great value, however, with the recommendations in their current form, we are afraid that they will not contribute to the aforementioned, sought consensus.
In these new recommendations, NORM management in industrial processes is always considered an existing exposure situation and therefore they conflict - to a large extent - with the requirements laid down in the International Basic Safety Standards (IAEA, GSR part 3, 2014) as well as with those from the European Council Directive 2013/59/Euratom. In the latter two, the requirements associated with planned exposure situations are imposed on (most) industrial processes involving NORM. Many countries have implemented these requirements in their national legislation which already implies a high level of international consensus, and therefore, the current ICRP recommendations may lead to confusion and opposition. By narrowing the scope to existing exposure situations (which in itself is comprehensible), ICRP largely ignores the contrast with these current regulations as mentioned above, with the risk of the radiological protection community disregarding these recommendations. We therefore advise the ICRP to take this into consideration as well and, where possible or necessary, to broaden the scope of these NORM-management recommendations in view of the exposure situation. If ICRP chooses to remain with their current guidance, this controversy should at least be elaborated, detailing more clearly the choices behind the recommendations. More issues related to this contrast in ‘exposure situation’ (planned versus existing) can be found in part 2 of this review.
It is true that the exposure to ionizing radiation from natural radioactivity is not the only and often not the dominating hazard in industrial processes involving NORM, and thus we agree with the recommended overall protection strategy into which the radiological aspects should be integrated and which should follow a graded approach. Also, the explicit incorporation of the protection of the environment is very much appreciated, although it could be put more into context with the graded approach.
Guidance on how to implement the ICRP-103-based system of radiological protection for the management of NORM in industrial processes would be of great value. This publication provides general recommendations on how to approach such a system, integrated in the overall (worker) protection strategy, based on a graded approach, and taking account of the potential detrimental effects on the environment. Although the current draft publication addresses many of these issues, we feel that it may still need quite some work to address the controversial issues raised earlier to reach consensus on a framework whose foundation does not go entirely against the prevailing international legislation. Furthermore, the document requires an editorial review to correct the typos and grammar.
Part 2: Specific remarks
Definition of NORM
The definition of NORM (lines 1519 – 1523):
“Material containing no significant amounts of radionuclides other than naturally occurring radionuclides, in which the activity concentrations of the naturally occurring radionuclides have been changed by some process and giving rise to enhanced exposure to human and non-human species”
deviates from the previous definition in ICRP-103:
“Radioactive material containing no significant amounts of radionuclides other than naturally occurring radionuclides. Material in which the activity concentrations of the naturally occurring radionuclides have been changed by some process are included in NORM”.
We suggest to either change it back to the original, ICRP-103 description, or, if the definition has been changed for a reason, this should be mentioned and explained clearly in this publication. Consequently, some parts in the main text (e.g., Lines 135 - 138) may need to be changed correspondingly.
Planned versus Existing exposure situation
The definitions of planned exposure situations (PES) and existing exposure situations in the current recommendations are as follows (para. 32, Lines 423 - 426 and Lines 418 – 422, respectively):
“Planned exposure situations are situations resulting from the deliberate introduction and operation of sources, used for their radioactive properties. For this type of situation, the use of the source is understood, and as such the exposures can be anticipated and controlled from the beginning”;
“Existing exposure situations are exposure situations resulting from a source that already exists, with no intention to use the source for its radioactive properties, before a decision to control the resulting exposure is taken. Decisions on the need to control the exposure may be necessary but not urgent. Characterisation of exposures is a prerequisite for their control”.
The original definitions from the ICRP-103 recommendations read (para. 176):
“Planned exposure situations are situations involving the deliberate introduction and operation of sources. Planned exposure situations may give rise both to exposures that are anticipated to occur (normal exposures) and to exposures that are not anticipated to occur (potential exposures; see Section 6.1.3)”;
“Existing exposure situations are exposure situations that already exist when a decision on control has to be taken, including prolonged exposure situations after emergencies”.
The formulation in para. 32 of the current recommendations suggests that the definitions of PES and EES are consistent with those in ICRP-103, which is, however, not the case. For example, the ICRP-103 definition of EES does not include the part “with no intention to use the source for its radioactive properties”. We suggest that this should be clearly emphasized and it should be described in detail why these definitions are changed. Since many recommendations build further on the definitions of PES and EES, changing them should not be done lightly.
The ICRP approaches exposure to radiation from NORM as an existing exposure situation (EES), instead of as a planned exposure situation (PES). In essence, the basis for this choice is concealed within the definition of “deliberate”. Both exposure situations, defined in para. 32 (lines 418 – 426), refer to the deliberate or intentional use of a source “for radioactive properties”, see line 424 for PES and line 419 for EES. This exact definition of “deliberate” was originally not present in the ICRP-103 recommendations and has been added here.
There is, however, another way to define “deliberate”, also in the context of industrial processes involving NORM. Even though the natural radioactivity is already present in the material, the intended (industrial) process with the NORM source may change the activity concentrations and/or lead to an elevation of the incurred doses to workers and members of the public. This is often well known before starting the industrial process. If, however, one deliberately or intentionally chooses to commence or to proceed with the process, it could also be regarded as a planned exposure situation for which the (normal and potential) exposures can be anticipated and controlled from the beginning. Hence, even though the exposures are adventitious, there is a ‘deliberate’ component in the decision to perform these activities. This option should at least be addressed more clearly by the ICRP in the current publication, which would facilitate broadening the scope regarding NORM management as suggested in part 1 of this review.
We emphasize that many of the proposed recommendations (e.g., integrated protection approach, graded approach, protection of the environment) are still valid under the scope of PES. Moreover, the regime of PES does not necessarily imply that all industrial processes involving NORM should be under (some form of) regulatory control, since the concepts of (generic or specific) exemption and clearance still apply and delineate the boundaries of what should be controlled and what not. That is, the system still offers sufficient flexibility to limit the regulatory burden.
As mentioned in para. 69 (lines 706 – 707) “… there is often a lack of radiological protection awareness or a culture supporting such protection.”. In addition, according to para. 93 (lines 853 - 854) “There is a basic need to share information and generally raise awareness about NORM within the workplace.”. Such awareness may be difficult to achieve within the regime of EES, especially when the radiological risks do not constitute the dominating hazard of the process. However, within the regime of PES, such awareness may be better achieved due to the more explicit (and planned) nature of the implementation of the radiological protection framework and its provisions.
Furthermore, if treated as an EES, the roles and responsibilities of the stakeholders (government, operator, workers, etc.) should be described more clearly, which could be done after the sentence in lines 926-927 (“The protection … pathways.”). In this context, ICRP could also provide guidance on how to deal with the accumulation of industries involving NORM at certain locations. This is of special importance as the principle of application of dose limits (for the public) is not relevant in case of an EES (para. 34, lines 443 - 444). Please provide recommendations on how the choice of a reference level could take into account such an accumulation and on whose responsibility it is to monitor this.
Finally, if ICRP were to decide to continue considering industrial processes involving NORM as an EES, the choice of annual dose criteria (reference levels) for workers and for members of the public should be substantiated more clearly, taking into account the discussion above (e.g., the planned aspects of the situation, awareness and radiological protection culture, accumulation of industry) and discussed more explicitly in terms of the ethical value of justice.
Building materials
The following six issues with regard to Section 4.2.4 and Annex A on building materials are noted:
(1) Para. 115, lines 1014 - 1016 “A reference level of … to be exceeded.”
It is not obvious that this is always the case, especially for countries that set their radon reference level to a value below 300 Bq/m3, e.g. 100 Bq/m3 in the Netherlands. In the latter case, for concrete with an index I=1, the radon concentration in the Netherlands may increase by typically 40 Bq/m3 with respect to the average situation currently in the Netherlands. Together with the contribution of radon emanating from the ground, the reference level may then be well exceeded in several parts of the country.
Moreover, contrary to the influx of radon from the ground, radon emanating from building materials can be controlled much better. The aforementioned increase in radon concentration from (an increased level of) NORM in building materials could then lead to an additional effective dose of 1 to 2 mSv/y for a member of the public (apart from the increase of the external radiation exposure). Even if the increased radon concentrations remain below the corresponding reference level, this goes against the principle of ALARA. These issues could be described in more detail in this publication.
(2) Para. 115, lines 1016 – 1017: “The exhalation of thoron is not expected to be of concern.”
With this we do not agree. Building materials, especially those for wall-finishing purposes, satisfying the 1 mSv/y criterion for external exposure to gamma radiation could result in an incurred thoron inhalation dose that is of the order of 5 mSv/y, as follows from reference (Smetsers and Tomas, 2019): Smetsers R.C.G.M. and Tomas J.M., A practical approach to limit the radiation dose from building materials applied in dwellings, in compliance with the Euratom Basic Safety Standards, J. Environ. Radioact. 196 (2019) 40-49; DOI: https://doi.org/10.1016/j.jenvrad.2018.10.007.
(3) Para. 116, line 1024 – 1026: “Where the value of … any circumstances.”
Practical situations where a dose limit of 1 mSv/y is exceeded, even when the index is 1 do exist: A combination of 20 cm of concrete and a 3 cm thick wall-finishing material (gypsum), each one with an index of I=1 separately, may together result in a net, effective gammadose of 1.34 mSv/y in the CEN reference room, as follows from the aforementioned ref. (Smetsers and Tomas, 2019). We suggest to change the text of this paragraph to take into account these, and similar, situations.
(4) Para. 116, lines 1026 – 1027: “Because of its … building material.”
We do not share the opinion that the index I is a conservative estimator. Index I is only conservative for low-density bulk materials such as aerated concrete (density of 625 kg/m3), but not for higher density materials as calcium silicate brick or ceramic brick (densities of 1750 and 1900 kg/m3, respectively). In fact, for concrete (density of 2350 kg/m3), an index of I=1 may not even be conservative enough. This is explained in more detail in the aforementioned ref. (Smetsers and Tomas, 2019), in particular in Table 2, section 5.3 and Figure 6 of this reference.
(5) Para. A.18
Values more recent than those in (UNSCEAR, 1982) and (IAEA, 2003) can be found in literature, see for instance (Trevisi et al., 2018): Trevisi R, Leonardi F, Risica S, and Nuccetelli C, Updated database on natural radioactivity in building materials in Europe, J. Environ. Radioact. 187 (2018) 90-105; https://doi.org/10.1016/j.jenvrad.2018.01.024.
(6) Table A.3 (just below para. 19, lines 1411 – 1412)
Please check and update Table A.3, especially with regard to the following issues:
* Did something go wrong with Th-232 in phosphogypsum? Is the lower value missing in this range?
* Idem for Ra-226 in aerated concrete;
* For some materials a single value is listed, whereas for other materials a range of values is indicated;
* Blast furnace slag has a certain amount of K-40, see reference (EC, 1999b).
Part 3: Detailed and editorial remarks
Para. 4, Lines 147-150
It might be helpful to rearrange the timeline, by moving the sentence on radium emanation in petroleum (Line 148) - discovered in 1904 - forward, and first mention the discovery by Marie Curie. We suggest the following:
“Only two years after the discovery of radioactivity by A. H. Becquerel in 1896, Marie Curie identified radium and polonium after processing several tons of pitchblende, an ore with high uranium content. Radon – or “radium emanation” as it was called, was found a few years later in petroleum and in natural gas brought to the surface.”
Para. 21, Line 294:
Please change “fissile” to “fertile”.
Para. 23, Lines 313 - 318:
* It is not clear for whom the radiation exposure pathway is relevant (worker or member of the public).
* Line 314: Please add “waste” and “residues” to the first bullet. Note: this also holds for Line 677 (para. 66).
Lines 348-349, caption of Table 2.1:
* Please refer to the source of this Table in the caption as well.
Note: in Table 2.1 itself, please update the unit of the effective dose (first row) from mS to mSv
Lines 375-376, caption of Table 2.2:
* Please refer to the source of this Table in the caption as well.
Para. 36, Lines 461 – 467:
Except maybe when NORM waste is disposed of on a waste-storage facility.
Para. 41, Lines 495 - 496: “In rare cases, the level of dose … purposes.”
Please specify - to some extent - what level of dose is referred to here.
Para. 66, Line 677:
Please add “waste” and “residues” to the first bullet.
Para. 109, Line 972: “All waste should be characterised …”
Characterizing “all waste” leads to considerable issues related to measurements.
Para. 114, Line 1008: “… and by releasing radon into indoor air.”
Please change to “… and by releasing radon (Rn-222) and thoron (Rn-220) into indoor air.”
Para. 120, Lines 1052 – 1053 (Section 4.2.5): “Technologies … legacy sites.”
Even though briefly explained in Lines 1058 through 1060, some more explicit guidance could be given on how best to avoid new legacy sites.
Para. 134, Lines 1157 - 1159: “Doses from … protection.”
This raises the question why more flexible dose criteria (here in terms of reference level) could be applied/allowed to these industries. This should be explained in more detail, in context of the issues raised under ‘planned versus existing’ (see above).
Annex A, Lines 1255 – 1454:
Please add a description of the following activity: “Geothermal energy production” (because it was already addressed in Line 304 and because it is an increasingly important industrial activity with possible radiological consequences).