CEN/TR 17113:2017

SLOVENSKI STANDARD
01-maj-2018
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Construction products - Assessment of release of dangerous substances - Radiation
from construction products - Dose assessment of emitted gamma radiation
Bauprodukte - Bewertung der Freisetzung von gefährlichen Stoffen - Festlegung des
Verfahrens zur Beurteilung der Strahlendosis und Klassifizierung von emittierter
Gammastrahlung
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Ta slovenski standard je istoveten z: CEN/TR 17113:2017
ICS:
13.020.99 Drugi standardi v zvezi z Other standards related to
varstvom okolja environmental protection
13.280 Varstvo pred sevanjem Radiation protection
91.100.01 Gradbeni materiali na Construction materials in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 17113
TECHNICAL REPORT
RAPPORT TECHNIQUE
October 2017
TECHNISCHER BERICHT
ICS 91.100.01
English Version
Construction products - Assessment of release of
dangerous substances - Radiation from construction
products - Dose assessment of emitted gamma radiation
Produits de construction - Evaluation de l¿émission de Bauprodukte - Bewertung der Freisetzung von
substances dangereuses ¿ Détermination de gefährlichen Stoffen - Festlegung des Verfahrens zur
l¿estimation dosimétrique et classification en fonction Beurteilung der Strahlendosis und Klassifizierung von
de l¿émission de rayonnement gamma emittierter Gammastrahlung

This Technical Report was approved by CEN on 28 May 2017. It has been drawn up by the Technical Committee CEN/TC 351.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17113:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 7
2 Terms and definitions . 7
3 European Regulatory Framework . 9
3.1 Provisions on radiation protection . 9
3.2 Provisions on the marketing of construction products under the CPR . 10
3.3 Radon exhalation from building materials . 11
4 Provisions for dose assessment . 11
4.1 General . 11
4.2 Principle of calculation . 11
4.3 Room model . 12
4.4 Basic assumptions. 13
4.4.1 General . 13
4.4.2 Shielding effect of materials for cosmic radiation . 14
4.4.3 Conversion factor for absorbed dose in air . 14
4.4.4 Occupancy . 14
4.4.5 Activity concentrations for reference concrete in Europe . 14
4.5 Graded approach to dose assessment taking into account density and thickness . 14
4.6 Assessment of indoor gamma exposure due to building materials and construction
products . 17
4.6.1 General . 17
4.6.2 Composite material . 18
4.6.3 Dose assessment for concrete coated with a layer of thin material . 19
4.6.4 Roof tiles . 19
4.6.5 Materials not complying to Formula (3) . 20
4.6.6 Conclusive . 20
Annex A (informative) Calculation of external gamma dose rate . 21
A.1 Calculation of gamma dose rate . 21
A.2 Parameters for a simple computer program . 23
Annex B (informative) Examples of dose assessment using Table 2 . 25
B.1 Example 1: Exposure to gamma radiation in a concrete room where the Ra and
Th concentrations are slightly above average . 25
B.2 Example 2: Exposure to gamma radiation in a room where the walls are made of
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material with elevated Ra and Th concentrations and the floor and ceiling of
typical concrete . 26
B.3 Example 3: Exposure to gamma radiation in a room with concrete floor and ceiling,
and cavity walls with brick and limestone . 27
Annex C (informative) Estimate of indoor gamma dose based on mass per unit area as
control parameter . 29
Annex D (informative) Validation of the dose modelling and a density corrected index
formula . 33
D.1 General . 33
D.2 Calculations . 33
D.3 Conclusion . 38
Annex E (informative) Considerations on and justification for choosing an appropriate room
size . 39
E.1 General . 39
E.2 Chosen dimensions for the model room . 40
E.3 Calculation of values given in Table E.1 . 41
E.3.1 Rooms 1a and 1b, with dimensions 12 m × 7 m × 2,8 m . 41
E.3.2 Rooms 2a and 2b, with dimensions 3 m × 4 m × 2,5 m . 41
E.4 Specific dose rates from different structures in the EN 16516 model room . 42
Bibliography . 46

European foreword
This document (CEN/TR 17113:2017) has been prepared by Technical Committee CEN/TC 351
“Construction products: Assessment of release of dangerous substances”, the secretariat of which is
held by NEN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
Introduction
The aim of this report is to propose a dose assessment methodology that accounts for factors such as
density or thickness of the material as well as factors relating to the type of construction and the
intended use of the material (bulk or superficial) as required by Annex VIII of the 2013/59/EURATOM
[1]. This approach is specially needed for building materials and construction products with an index
exceeding 1 but that nonetheless may comply with the 1 mSv per year reference level established in the
2013/59/EURATOM [1].
NOTE Although the methodology is centred around the reference level of 1 mSv established in the
2013/59/EURATOM, the methodology is also applicable if a reference value other than 1 mSv per year is selected.
In that case, the selected dose value D and its corresponding index value I is adjusted accordingly.
In 1996, natural radiation sources were already included in the standards established by Euratom as
well as those established by the IAEA [2]. Since then, the European Commission has moved ahead
publishing, on a regular basis, technical support guidance and recommendations on Naturally Occurring
Radioactive Material (NORM) issues. In 1997, for instance, recommendations [3] were published to help
deal with "significant increase in exposure due to natural radiations". In 1999, the European
Commission published radiological protection principles concerning the natural radioactivity of
building materials [4] and reference levels for workplaces processing materials with enhanced levels of
naturally occurring radionuclides [5]. Lastly, in 2001 the European Commission published
recommendations dealing with exemption and clearance levels for NORM residues [6].
These recommendations have provided Member States with criteria and a sound technical framework
to help establish national regulations for NORM and building materials. Some Member States have
already included all or parts of these recommendations in their regulatory framework anticipating the
new EU directive.
Subsequently, the European Commission decided to harmonize, promote and consolidate the main
recommendations, introducing them into a new Council directive (2013/59/Euratom [1]) laying down
basic safety standards for the protection against the danger arising from exposure to ionising radiation.
This BSS directive was officially issued in January 2014. Member States have four years to transpose
and implement this directive and according to the Euratom treaty, these members will before then,
communicate to the Commission their existing and draft provisions. The Commission will then make
appropriate recommendations for harmonizing the provisions amongst member States.
Requirements of this directive (2013/59/EURATOM, [1]) dealing with building materials are hereby
presented. They should be taken into account along with the 2011 EU regulation laying down
harmonized conditions for the marketing of construction products (EU no 305/2011) [7], so called CPR,
containing many relevant articles which complement the aforesaid directive.
Both EU regulatory documents constitute the new basis for building material radiation protection
regulation and should be soon followed by more detailed EU guidance and standards of which this
document (CEN/TR 17113) should be part.
The European Commission (EC) has mandated the CEN to establish EU harmonized standards regarding
dose assessment of emitted gamma radiation from construction products. The EC has also informed
CEN (CEN/TC 351, Berlin 11 February 2013) that the aim is to establish one test method per product, or
product type, that the method should be demonstrably robust and should be adopted by all Member
States as soon as the 2013/59/EURATOM comes into force.
This document can help Member State regulators to complete the 2013/59/EURATOM and CPR
regulatory framework covering a screening tool, dose modelling, and related technical information
about radiation protection. Amongst others, the following recommendations were discussed by the CEN
and the EC for the content of this document:
— The scope will exclude radon and thoron exhalation from building materials because this
exhalation is dealt with in a different manner in the EU regulation. Regulatory explanations are
given in Clause 3.
— Main assumptions, coefficients and conversion factors are taken into account.
— The methodology enables establishing which building materials may lead to a dose exceeding
1 mSv per year for a member of the public or which building materials can be exempted from
further restrictions.
— Mass per unit area (kg/m ) of the material will be considered in the approach keeping a dose
estimate model based on similar room models as the one used to establish the index mentioned in
the 2013/59/EURATOM.
— Additional sensitivity analysis regarding the room geometry is presented in Annex E to
demonstrate that there is no more than 10 % of influence of such geometry upon the determination
of doses.
Lastly, it is important to underline that the EU regulatory philosophy is to ensure that gamma doses
from building materials to a member of the public remain under 1 mSv per year in addition to outdoor
external exposure (2013/59/EURATOM Article 75) [1]. A simplified model, so called "index" in the
2013/59/EURATOM is also proposed as a conservative screening tool ensuring that materials with an
index I less than 1 do not present any risk exceeding 1 mSv per year of indoor gamma radiation, in any
construction, to a member of the public.
Annex VIII of the 2013/59/EURATOM Directive presents such an index requiring determination of
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Ra, Th and K. For the purposes of this determination, CEN/TC 351 has developed a test method
to be published first as a Technical Specification (TS) and later after completed validation as a European
Standard (EN). In certain cases, there is a need to assess dose more precisely as described in Annex VIII
of the 2013/59/EURATOM Directive. This TR presents such a formula for more sophisticated
calculation of dose. It could serve as basis for a European approach supporting the implementation of
the 2013/59/EURATOM Directive taking place in member states, also from a harmonized approach
point of view.
As determination of three radionuclides of gamma radiation according to an EN (TS) will be part of
obligations of product manufacturers and will be referred to in harmonized product standards under
the Construction Products Regulation (CPR; EU 305/2011) (hEN) it is proposed that assessment of dose
could be consequently described in an EN.
This Technical Report presents the state-of-the-art on dose assessment presented in RP 112 [4] and
now further developed into the form of a more sophisticated formula. It has been noticed that for
credibility reasons exact correctness of all background data must be further checked. It is proposed that
this could take place when developing a European Standard.
1 Scope
The aim of this Technical Report is to propose a methodology to determine indoor gamma dose from
building materials and to help classify such a product as required in the Construction Products
Regulation [7]. This first technical approach could be a precursor for the development of a harmonized
European Standard based on this methodology.
NOTE 1 In this Technical Report, doses from radon and thoron exhalation are excluded. However, in 3.3,
information is given on how radon exhalation is dealt with in (EU)2013/59/Euratom, the Basic Safety Standards
Directive (2013/59/EURATOM) [1].
NOTE 2 Compliance with national exemption levels for NORM nuclides remains.
2 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16687 [8] and the following
apply.
2.1
authorization
registration or licensing of a practice
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (7) [1]]
2.2
building material
any construction product for incorporation in a permanent manner in a building or parts thereof and
the performance of which has an effect on the performance of the building with regard to exposure of
its occupants to ionizing radiation
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (9) [1]]
Note 1 to entry: Building materials considered in this Technical Report are the construction products used for
building works. Other construction products used for any other construction works (civil engineering, etc.) are not
relevant and out of the purpose of the scope of this Technical Report. The assessment described in this Technical
Report was carried out under the assumption of the CEN/TC 351 model room.
2.3
competent authority
authority or system of authorities designated by Member States as having legal authority for the
purposes of the 2013/59/EURATOM [1]
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (16) [1]]
2.4
effective dose
E
sum of the weighted equivalent doses in all the tissues and organs of the body from internal and
external exposure
Note 1 to entry: It is defined by the expression:
(1)
E w H w wD
T T T R TR,
∑ ∑∑
T TR
==
where
D is the absorbed dose averaged over tissue or organ T, due to radiation R [-];
T,R
wR is the radiation weighting factor [-];
wT is the tissue weighting factor for tissue or organ T [-].
Note 2 to entry: The values for w and w are specified in Annex II of the BSS [1].
T R
Note 3 to entry: The unit for effective dose is the sievert (Sv).
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (25) [1]]
2.5
exemption level
value established by a competent authority or in legislation and expressed in terms of activity
concentration, total activity at or below which a radiation source is not subject to notification or
authorisation
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (34) [1]]
2.6
practice
human activity that can increase the exposure of individuals to radiation from a radiation source and is
managed as a planned exposure situation
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (65) [1]]
2.7
Ra
radionuclide Ra and its progenies in secular equilibrium
2.8
radon
radionuclide Rn and its progeny, as appropriate
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (82) [1]]
2.9
reference level
level of effective dose or equivalent dose or activity concentration above which it is judged
inappropriate to allow exposures to occur, even though it is not a limit that may not be exceeded
Note 1 to entry: Exposure to gamma radiation from building materials is ranked by the EU BSS among the
existing exposure situations.
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (84) [1]]
2.10
regulatory control
any form of control or regulation applied to human activities for the enforcement of radiation
protection requirements
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (87) [1]]
2.11
Sievert
Sv
special name of the unit of equivalent or effective dose
Note 1 to entry: One sievert is equivalent to one joule per kilogram: 1 Sv = 1 J/kg.
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (91) [1]]
Note 2 to entry: 1 Gy is also 1 J/kg.
2.12
Th
radionuclide Th and its progenies in secular equilibrium
2.13
thoron
radionuclide Rn and its progeny, as appropriate
[SOURCE: 2013/59/EURATOM, chapter II, Article 4, (97) [1]]
3 European Regulatory Framework
3.1 Provisions on radiation protection
Some new requirements have been established for building materials in the 2013/59/EURATOM [1]
but they derive from earlier EU or IAEA principles and recommendations given in references [4], [5],
[6], [9], [10], [11], [12], and [13]. Such principles and recommendations were taken into consideration
by some Member States but further harmonisation and consistency throughout Europe were to be
established. Existing principles and recommendations were then reviewed and enhanced by EU
Member States to be turned into proper harmonized EU regulations (2013/59/EURATOM, [1]) which
was officially issued in January 2014.
For building materials of concern, which are identified by individual Member States (whether from
natural origin or from those in which specific residues from identified NORM industries have been
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incorporated), activity concentrations of Ra, Th and K need be analysed so that builders can
assess the final gamma dose from the building and its compliance with the reference level of 1 mSv per
year (compared to outdoor background dose).
If the dose resulting from building material exceeds the reference level of 1 mSv per year, the radium
concentration of this material can be quite high and this possibly leads to a significant emission
(exhalation) of radon. Due to the influence of the release (emanation) and of the transport process
(diffusion, convection) inside the building material, no clear correlation between the radium
concentration and the exhalation of radon can be found. Materials with a low radium concentration can
release a significant and relevant amount of radon, or vice versa. To regulate the radium concentration
is necessary but not sufficient to reduce the radon exhalation.
NOTE 1 The inhalation dose from radon is not considered in the reference level of 1 mSv per year. The radon
from building materials and soil is regulated by a separate reference level for indoor radon concentration. In many
cases, the radon indoors predominantly originates from the ground, and not from the building material.
Although responsible use of industrial by-products in building materials is well-known, there are some
examples where building materials have led to an increased dose for the inhabitants of buildings [14].
NOTE 2 An indicative list of building materials potentially of concern is included in 2013/59/EURATOM Annex
XIII [1] and is to be taken into account by Member States.
NOTE 3 In the case of composite material, like concrete, the activity concentration index can be calculated from
the contribution of the constituents (see Figure 3). Not every constituent will necessarily comply with the
condition I < 1, nor will every building material.
The EU RP 112 principles [4] established the first non-prescriptive EU radiation protection framework
concerning the natural radioactivity of building materials. This EU RP 112 was based on a publication
[15] from the Finnish regulator (STUK) and provides EU Member States with a user-friendly screening
tool to evaluate building materials’ radiation gamma emissions and help check compliance with the
maximum reference level mentioned above.
To establish this screening tool, a conservative dose estimate model was first created. This model
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considered the activity concentrations of Ra and Th in secular equilibrium with the members of
each decay chain (progenies) and K. The calculations were based on a hypothetical room (with
dimensions of 4 m × 5 m × 2,8 m) with walls, ceiling and floor of 20 cm thick and made of a material
with a fixed density of 2.350 kg/m (similar to concrete). In this model, it is also assumed: an annual
exposure time of 7.000 hours a year; a dose conversion factor of 0,7 Sv/Gy and a background absorbed
dose rate of 50 nGy/h. The doses were calculated according to the Berger approach with empirical
build-up factors and self-attenuation.
Considering all these assumptions, an activity concentration index (I) was then determined by the
following simplified Formula (2):
C C C
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Ra Th K
I= ++
(2)
300 200 3000
where
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C is the activity concentration of Ra, Th or K [Bq/kg].
The dose estimate is close to 1 mSv per year only when the index value is close to 1. An index < 1 with
the conditions mentioned above means a dose estimate in compliance with the maximum reference
level of 1 mSv per year for a member of the public. This simplified model was deemed to be sufficiently
conservative to be part of the 2013/59/EURATOM [1] since most dwellings or buildings will not be
designed to be as massive as the 'bunker' (hypothetical room) described above.
In the 2013/59/EURATOM [1], for building materials identified by the Member States as being of
226 232 40
concern, it is required that the activity concentrations of Ra, Th and K be determined
(2013/59/EURATOM article 75 and its annex VIII, [1]). The index can then be used as a screening tool
to allow building material to be placed onto the EU market without any restrictions. National regulators
and/or building codes may use this index to identify building materials which need no further analysis
with respect to emitted gamma radiation.
Although this screening tool should be sufficient for most building materials, it remains much too
conservative for thin materials such as tiles, for light density products or for materials used in marginal
quantities. The 2013/59/EURATOM [1] allows density, thickness and use of materials to be taken into
account in an appropriate dose modelling approach if need be.
3.2 Provisions on the marketing of construction products under the CPR
The CPR [7] regulates the placing and making available on the market of construction products. It
establishes the requirements and obligations that have to be fulfilled where a construction product is
covered by a harmonised technical specification (i.e. a harmonised standard or a European Technical
Assessment). For such products, a 'declaration of performance', has to be drawn up, and this permits
the affixing of the CE marking. The CE marking confirms that the product complies with its declared
performance, and its harmonised technical specification, and permits free trans-boundary movement
across the European Economic Area.
The manufacturer has to draw up such a declaration of performance with all related documentation.
The declaration of performance (CPR article 6, [7]) shall include the construction product's intended
uses along with levels or classes for its essential characteristics (CPR articles 6.3d and 6.3g, [7]).
This declaration of performance should be accompanied by information on the content of all hazardous
substances (Recital 25 of CPR [7] and Recitals 31-33 of EC Regulation n° 1907/2006 of the European
Parliament and of the Council of 18/12/2006 – REACH [16]).
The responsibilities of the manufacturers, importers and distributors are monitored by 'Market
surveillance authorities' (CPR articles 56-59).
3.3 Radon exhalation from building materials
Regarding radon exhalation from building materials, Member States decided not to deal with this issue
in the screening process, which, in consequence, addresses gamma radiation only. However, radon
exhalation might be dealt with separately, including additional requirements, in national action plans.
Additional strategies and methods for preventing radon ingress in new buildings, including
identification of building materials with significant radon exhalation might be added by some Member
States if need be (2013/59/EURATOM Annex XVIII.8 [1]).
Specific 2013/59/EURATOM parts deal with radon issues, requiring the establishment of national
reference levels. These reference levels should be less than or equal to 300 Bq/m for the annual
average indoor concentration from all possible sources.
It is important and an obligation on Member States to promote actions to identify dwellings with radon
concentration (as an annual average) exceeding the reference level mentioned above and to encourage,
where appropriate, by technical or financial means, radon concentration-reducing measures in these
dwellings (2013/59/EURATOM article 74.2, [1]). Action plans will have to be established by all EU
Member States to address radon exposure, including identification of building materials with significant
radon exhalation.
4 Provisions for dose assessment
4.1 General
In order to prospectively assess indoor external gamma doses resulting from the use of a given building
material, mathematical models need to be used. For that purpose, the activity concentrations of three
radionuclides in the building material have to be known, and a series of assumptions needs to be made
regarding the room model (shape and size, thickness and densities of the walls, existence of door and
windows, etc.).
226 232 40
The main contributors to the gamma dose are Ra, Th and their progeny, and K. The activity
concentrations of these radionuclides can be determined in accordance with draft TS 00351014 [17].
226 232
Hereafter, ' Ra' and ' Th' include all progenies in secular equilibrium (i.e. 226Ra++sec, 232Th++sec).
If a disequilibrium between the nuclides of a given chain can be assumed, it is recommended to use the
maximum concentration for typifying the whole chain, keeping in mind that this approach may
overestimate the dose.
The proposed method of dose assessment, together with the assumptions made on the room model, is
described below.
4.2 Principle of calculation
The method used in this report for calculating the external dose from building materials is based on the
approach of STUK [14], which was also the basis for the document “Radiation Protection 112” [4]. It
consists of a point-kernel method that uses the Berger approximation for the build-up factor. Further
details can be found in Annex A.
As suggested by the 2013/59/EURATOM directive, this document takes into account the real intended
use of the building material (such as whether it is used as superficial or as bulk material) along with its
thickness and density. It is important to bear in mind that the EU regulatory philosophy is to ensure that
gamma doses from building materials to members of the public remain under 1 mSv per year.
NOTE The calculated dose, despite its correction for surface density, still remains a conservative estimate and
is not necessarily representative for the product's dose under real conditions. Its limited representation under
real conditions is embedded in the choice of assumptions which include for example, no consideration of doors
and windows, assuming a room built from a single construction product and no consideration of alternative room
dimensions.
4.3 Room model
The typical room model used for gamma-radiation calculations is a rectangle parallelepiped in which all
construction parts are made of 200 mm thick concrete with no windows or doors (Koblinger, 1978 [18];
Markkanen, 1995 [15]). In particular, a room of 12 m × 7 m × 2,8 m was used in the document STUK-B-
STO 32 [14]. The EN 16516 [19] reference room, on the other hand, has dimensions of
2 2
3 m × 4 m × 2,5 m, a door (1,6 m ) in one of the long walls, and a window (2 m ) in one of the short
walls.
For products used as a superficial layer with a thickness of 30 mm or less, it is assumed the layer behind
is made of the reference concrete. The contribution of this concrete layer to the dose needs also to be
taken into account; for this reason, the assumption of RP 112 that an index I < 6 for superficial material
will lead to a dose < 1 mSv may not be conservative enough. The absorbed dose rate in air is usually
assessed in the middle of the room. For the STUK room model, the assumption of obtaining the dose
rate at the centre of the room is valid as the dose rate is fairly constant in most of the room and only
increases slightly (within 10 %) for areas within 50 cm of the walls [20].
Room size and dimensions have also very limited effect on the total dose, provided that the same
material is used in all structures. Risica et al. (2001) [21] reported variations of less than 6 % when the
width and length of the room were varied from 2 m to 10 m. Annex E provides more details.
Exclusion of windows and doors in the room provides for a conservative approach regarding radiation
protection (see Annex E). The EN 16516 reference room with no doors or windows is considered in this
report (see Figure 1). Whilst keeping consistency with other CEN/TC 351 standards, this room model is
compatible with the activity concentration index formula, as expressed in
2013/59/EURATOM Annex VIII [1].
Figure 1 — Room model; dimensions of 3,0 m × 4,0 m × 2,5 m
NOTE The room model for which the activity index formula was derived [13] and the model room used in
226 232 40
EN 16516 [19] result in nominal dose rates differing by roughly 4 %, 5 % and 6 % for Ra, Th and K,
respectively.
4.4 Basic assumptions
4.4.1 General
The 2013/59/EURATOM [1] defines the reference value of 1 mSv per year as a dose in addition to the
natural background (e.g. 0,29 mSv per year). Therefore, the total annual dose indoor – as sum of
building materials and background – can be higher than 1 mSv, e.g. 1,29 mSv. There are two possible
interpretations:
a) Building materials shield all of the natural background. The total dose resulting from the building
materials can be 1,29 mSv.
b) There are no shielding effects. The dose resulting from a building material can be 1 mSv per year.
RP 112 [4] follows the philosophy of option a). Therefore the basic approach in determining the excess
exposure is as follows:
1) The total exposure caused by the building is calculated;
2) The exposure caused by terrestrial background gamma radiation is then subtracted from it;
3) The result is referred to as the excess exposure.
In the example calculations presented in the Annexes, a European surface area weighted average value
of 60 nGy/h (corresponding to 0,29 mSv per year for an occupancy time of 7.000 h) is assumed for
terrestrial background gamma radiation. The average background gamma radiation was calculated
from data taken from the UNSCEAR 1988 and 2008 reports ([22], [23]).
NOTE 1 The background gamma radiation used in the calculations in this TR is based on the European average
and this is higher than the value of 50 nGy/h used as background in RP 112 [4].
NOTE 2 The UNSCEAR 2008 Report, Annex B [23] estimates an average worldwide value for outdoor dose
rates of 58 nGy/h.
4.4.2 Shielding effect of materials for cosmic radiation
The possible shielding effect of materials for cosmic radiation is considered to be small, and therefore
exposure originating from cosmic radiation is not considered in the assessments.
NOTE The 2013/59/EURATOM [1] specifically excludes cosmic radiation.
4.4.3 Conversion factor for absorbed dose in air
A conversion factor of 0,7 Sv/Gy is used for converting the absorbed dose in air to the effective dose
according to the UNSCEAR 2000 report [24].
4.4.4 Occupancy
An occupancy time of 7.000 h per year, as an average for the annual time spend indoors in Europe, is
used in the calculations.
4.4.5 Activity concentrations for reference concrete in Europe
Regarding activity concentrations for reference concrete in Europe, the values in Table 1, taken from
the RP 96 [12], will be considered.
Table 1 — Activity concentrations for reference concrete in Europe (RP 96 [12])
Radionuclide C
Ra 40 Bq/kg
Th 30 Bq/kg
K 400 Bq/kg
4.5 Graded approach to dose assessment taking into account density and thickness
The gamma dose rate is calculated in the middle of the standard sized room presented in Figure 1. The
specific dose rates contributed by the walls, floor and ceiling are given in Table 2. The total indoor dose
rate is calculated by summing the separately calculated dose rates caused by walls, floor and ceiling. A
variety of dose assessments resulting from the use of the specific dose rates given in Table 2 are
described in examples in Annex B. The dose assessments provide examples relating to massive concrete
structures (e.g. apartment blocks) and for a smaller simpler type of structure we may find in rural areas.
Table 2 — Specific dose rate in air from the different structures in the room of Figure 1
Mass
20 cm thick concrete
Wall, ceiling or floor
per unit
c
behind the wall, ceiling Shielding factor
b
a material (top layer)
area of
or floor material
wall,
ceiling
or floor pGy/h per Bq/kg pGy/h per Bq/kg
material
2 226 232 40 226 232 40 226 232 40
kg/m Ra Th K Ra Th K Ra Th K
Wall W : Dimensions 4,0 m × 2,5 m, distance to room centre 1,5 m
0 0 0 0 150 180 13 1,0 1,0 1,0
25 15 17 1,2 140 160 12 0,93 0,89 0,92
50 30 34 2,4 130 150 11 0,87 0,83 0,85
100 58 66 4,6 100 120 8,9 0,67 0,67 0,68
150 81 93 6,5 82 99 7,3 0,55 0,55 0,56
200 100 120 8,1 64 79 6,0 0,43 0,44 0,46
300 130 150 10 37 49 3,9 0,25 0,27 0,30
500 160 180 13 12 19 1,6 0,08 0,11 0,12
Wall W : Dimensions 3,0 m × 2,5 m, distance to room centre 2,0 m
0 0 0 0 89 100 7,5 1,0 1,0 1,0
25 8,2 9,4 0,7 83 96 6,9 0,93 0,96 0,92
50 16 19 1,3 76 89 6,3 0,85 0,89 0,84
100 32 36 2,5 63 75 5,4 0,71 0,75 0,72
150 45 52 3,6 51 61 4,5 0,57 0,61 0,60
200 57 65 4,5 41 49 3,7 0,46 0,49 0,49
300 74 84 6,0 25 32 2,5 0,28 0,32 0,33
500 91 110 7,6 8,5 13 1,1 0,10 0,13 0,15
Floor or ceiling: Dimensions 4,0 m × 3,0 m, distance to room centre 1,25 m
0 0 0 0 210 240 17 1,0 1,0 1,0
25 22 24 1,7 190 220 16 0,90 0,92 0,94
50 43 49 3,4 170 200 14 0,81 0,83 0,82
100 81 93 6,4 140 160 12 0,67 0,67 0,71
150 110 130 9,0 110 130 9,6 0,52 0,54 0,56
200 140 160 11 81 100 7,7 0,39 0,42 0,45
300 180 200 14 46 60 4,9 0,22 0,25 0,29
500 210 240 18 14 22 1,9 0,07 0,09 0,11
NOTE Calculations are based on the procedure presented in Annex A.
a
Mass per unit area of the wall, floor or ceiling is the product of the thickness and the density of the
structure. For example, in the case of a 15 cm (= 0,15 m) thick wall made of building blocks whose
3 3 2
density is 2.000 kg/m , the mass per unit area of the wall is 0,15 m × 2.000 kg/m = 300 kg/m .
b
This is the specific dose rate caused by the wall w or w , or floor or ceiling having a certain mass per
1 2
2 226
unit area. For example, if the wall w has a mass per unit area of 300 kg/m and its Ra concentration is
100 Bq/kg, the dose rate caused by the Ra in the wall w1 is (130 pGy/h per Bq/kg) × (100 Bq/kg) =
13.000 pGy/h = 13,0 nGy/h = 0,013 μGv/h. The “top layer” in brackets refers to the case where the wall,
ceiling or floor structure comprises two different material layers, for example a tile on the top and a
concrete structure behind it. In such a case the specific dose rates given in this column should be used for
the “top layer” material e.g. such as the tiles.
c
The shielding factor applies when the wall, floor or ceiling consist of two components. In that case the
shielding factor describes the shielding from the inner surface to the outer surface. These shielding
factors are applicable for example when computing the dose rate for a cavity wall. For such type of wall
the dose rate from the outer and the inner surface are computed separately and subsequently
accumulated. The dose rate for the outer surface is based on the dose rate for the outer wall multiplied
with the shielding factor. The shielding factor is based on the surface thickness of the inner wall. The dose
rate for the inner wall is obtained directly from this table. An example of a cavity wall is included in B.3.
The index I was derived under the assumption of a mass per unit area of 470 kg/m , corresponding to a
20 cm thick concrete with density 2.350 kg/m , and may be used as a screening tool to release building
materials from restrictions with regard to gamma radiation, see Formula (2):
C
C C
232 40
Ra Th K
I= ++ (2)
300 200 3000
where
C is the activity concentration of the radionuclide x [Bq/kg].
x
However, as can be seen from Table 2, the above screening tool results may be too conservative in two
types of situations:
— Building materials used in bulk amount with substantially lower densities than standard concrete,
such as lightweight concrete, where the index may overestimate the resulting dose up to a factor 3
or 4 [20].
— Building materials used as thin covering materials, such as tiles, whose small thickness results in
several-times-lower doses than predicted by the index.
As alternative to Table 2, a dose model formula which could account for both situations and provide a
more accurate assessment tool for light-density and thin building materials is prese
...