EN ISO 18589-7:2016

SLOVENSKI STANDARD
01-junij-2016
Merjenje radioaktivnosti v okolju - Tla - 7. del: Meritve radionuklidov, ki sevajo
žarke gama, na kraju samem (ISO 18589-7:2013)
Measurement of radioactivity in the environment - Soil - Part 7: In situ measurement of
gamma-emitting radionuclides (ISO 18589-7:2013)
Ermittlung der Radioaktivität in der Umwelt - Erdboden - Teil 7: In-situ-Messung von
Gammastrahlung emittierenden Radionukliden (ISO 18589-7:2013)
Mesurage de la radioactivité dans l'environnement - Sol - Partie 7: Mesurage in situ des
radionucléides émetteurs gamma (ISO 18589-7:2013)
Ta slovenski standard je istoveten z: EN ISO 18589-7:2016
ICS:
13.080.99 Drugi standardi v zvezi s Other standards related to
kakovostjo tal soil quality
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 18589-7
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2016
EUROPÄISCHE NORM
ICS 17.240; 13.080.01
English Version
Measurement of radioactivity in the environment - Soil -
Part 7: In situ measurement of gamma-emitting
radionuclides (ISO 18589-7:2013)
Mesurage de la radioactivité dans l'environnement - Ermittlung der Radioaktivität in der Umwelt -
Sol - Partie 7: Mesurage in situ des radionucléides Erdboden - Teil 7: In-situ-Messung von
émetteurs gamma (ISO 18589-7:2013) Gammastrahlung emittierenden Radionukliden (ISO
18589-7:2013)
This European Standard was approved by CEN on 21 February 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

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, 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
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18589-7:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
European foreword
The text of ISO 18589-7:2013 has been prepared by Technical Committee ISO/TC 85 “Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 18589-7:2016 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2016, and conflicting national standards shall
be withdrawn at the latest by October 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: 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, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 18589-7:2013 has been approved by CEN as EN ISO 18589-7:2016 without any
modification.
INTERNATIONAL ISO
STANDARD 18589-7
First edition
2013-10-01
Measurement of radioactivity in the
environment — Soil —
Part 7:
In situ measurement of gamma-
emitting radionuclides
Mesurage de la radioactivité dans l’environnement — Sol —
Partie 7: Mesurage in situ des radionucléides émetteurs gamma
Reference number
ISO 18589-7:2013(E)
©
ISO 2013
ISO 18589-7:2013(E)
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols, and units . 2
3.1 Terms and definitions . 2
3.2 Symbols and units . 3
4 Principles . 6
4.1 Measurement method . 6
4.2 Uncertainties of the measurement method . 6
5 Equipment . 6
5.1 Portable in situ spectrometry system . 6
5.2 Detector System . 7
5.3 Pulse processing electronics . 8
5.4 Assembly jig for a detector system . 9
5.5 Collimated detector . 9
6 Procedure.12
6.1 Calibration .12
6.2 Method of combined calibrations .12
7 Quality assurance and quality control program .17
7.1 General .17
7.2 Influencing variables .17
7.3 Instrument verification.17
7.4 Method verification .17
7.5 Quality control program .17
7.6 Standard operating procedure .19
8 Expression of results .19
8.1 Calculation of activity per unit of surface area or unit of mass .19
8.2 Calculation of the characteristic limits and the best estimate of the measurand as well as
its standard uncertainty .19
8.3 Calculation of the radionuclide specific ambient dose rate .21
9 Test report .22
Annex A (informative) Influence of radionuclides in air on the result of surface or mass activity
measured by in situ gamma spectrometry .23
Annex B (informative) Influence quantities .24
Annex C (informative) Characteristics of germanium detectors .27
Annex D (informative) Field-of-view of an in situ gamma spectrometer as a function of the photon
energy for different radionuclide distributions in soil .29
Annex E (informative) Methods for calculating geometry factors and angular correction factors.33
Annex F (informative) Example for calculation of the characteristic limits as well as the best
estimate of the measurand and its standard uncertainty .41
Annex G (informative) Conversion factors for surface or mass activity to air kerma rate and
ambient dose equivalent rate for different radionuclide distribution in soil .45
Annex H (informative) Mass attenuation factors for soil and attenuation factors for air as a
function of photon energy and deviation of G(E,V) for different soil compositions .52
Bibliography .54
ISO 18589-7:2013(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
The committee responsible for this document is ISO/TC 85, Nuclear energy, nuclear technologies, and
radiological protection, Subcommittee SC 2, Radiological protection.
ISO 18589 consists of the following parts, under the general title Measurement of the radioactivity in the
environment — Soil:
— Part 1: General guidelines and definitions
— Part 2: Guidance for the selection of the sampling strategy, sampling and pre-treatment of samples
— Part 3: Measurements of gamma-emitting radionuclides
— Part 4: Measurement of plutonium isotopes (plutonium 238 and plutonium 239 + 240) by alpha spectrometry
— Part 5: Measurement of strontium 90
— Part 6: Measurement of gross alpha and gross beta activities
— Part 7: In situ measurement of gamma-emitting radionuclides
iv © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
Introduction
In situ gamma spectrometry is a rapid and accurate technique to assess the activity concentration of
gamma-emitting radionuclides present in the top soil layer or deposited onto the soil surface. This
method is also used to assess the dose rates of individual radionuclides.
In situ gamma spectrometry is a direct physical measurement of radioactivity that does not need any
soil samples, thus reducing the time and cost of laboratory analysis of large number of soil samples.
The quantitative analysis of the recorded line spectra requires a suitable area for the measurement.
Furthermore, it is required to know the physicochemical properties of the soil and the vertical
distribution in the soil to assess the activity of the radionuclides.
INTERNATIONAL STANDARD ISO 18589-7:2013(E)
Measurement of radioactivity in the environment — Soil —
Part 7:
In situ measurement of gamma-emitting radionuclides
1 Scope
This part of 18589 specifies the identification of radionuclides and the measurement of their activity
in soil using in situ gamma spectrometry with portable systems equipped with germanium or
scintillation detectors.
This part of ISO 18589 is suitable to rapidly assess the activity of artificial and natural radionuclides
deposited on or present in soil layers of large areas of a site under investigation.
This part of ISO 18589 can be used in connection with radionuclide measurements of soil samples in the
laboratory (ISO 18589-3) in the following cases:
— routine surveillance of the impact of radioactivity released from nuclear installations or of the
evolution of radioactivity in the region;
— investigations of accident and incident situations;
— planning and surveillance of remedial action;
— decommissioning of installations or the clearance of materials.
It can also be used for the identification of airborne artificial radionuclides, when assessing the exposure
levels inside buildings or during waste disposal operations.
Following a nuclear accident, in situ gamma spectrometry is a powerful method for rapid evaluation of
the gamma activity deposited onto the soil surface as well as the surficial contamination of flat objects.
NOTE The method described in this part of ISO 18589 is not suitable when the spatial distribution of the
radionuclides in the environment is not precisely known (influence quantities, unknown distribution in soil) or in
situations with very high photon flux. However, the use of small volume detectors with suitable electronics allows
measurements to be performed under high photon flux.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
IEC 61275, Radiation protection instrumentation — Measurement of discrete radionuclides in the
environment — In situ photon spectrometry system using a germanium detector
ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the
confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 18589-7:2013(E)
3 Terms, definitions, symbols, and units
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
intrinsic efficiency
η
cross section of a detector for photons from the direction of the crystal symmetry axis
Note 1 to entry: The intrinsic efficiency depends on the energy of the photon.
3.1.2
detector efficiency
η (E)
detector efficiency in the direction of the crystal symmetry axis as a function of the photon energy E
3.1.3
detector height
d
distance between the geometrical centre of the crystal and the soil surface
3.1.4
efficiency per unit of surface area or unit of mass
ε
ratio between the net count rate of an absorption line with energy E and the photon emission rate per
unit area or mass
3.1.5
relative detection efficiency
ratio, expressed in percentage, of the count rate in the Co 1 333 keV total absorption peak to the one
obtained with a 3 x 3 inch NaI(Tl) scintillator for normal incidence and at 0,25 m from the source
3.1.6
geometry factor
G
ratio between the flux density without scattered photons measured at the detector location and the
photon emission rate per unit area or mass
3.1.7
aperture angle of collimator
ϑ
col
characteristic angle for an in situ gamma spectrometer with collimator
3.1.8
[7]
relaxation mass per unit area
β
mathematical parameter describing radionuclide distribution as a function of soil depth
Note 1 to entry: It indicates the soil mass per unit of surface area at which gamma activity decreases to 1/e (37 %).
3.1.9
field-of-view of a detector
soil surface area, from which 90 % of the unscattered detected photons originate
3.1.10
distribution model
V
entity of all physical and geometrical parameters to describe the distribution of the radionuclide in the
environment as well as the interaction of an emitted photon with soil and air
2 © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
3.1.11
angular coefficient
k
m
factor taking into account the angular response of the detector and the angular distribution of the
incident flux
3.1.12
measurement area
area in the soil and/or on the soil surface having radionuclide activity per unit of surface area or unit of mass
3.1.13
[7]
mass per unit area (collimator)
ζ
col
product of material density and wall thickness of a collimator
Note 1 to entry: The mass per unit area is reported for a polar angle, ϑ, of 90° in relation to the crystal centre.
3.1.14
cross section of the detector
ratio of the net rate of the total absorption line at energy E and the flux density of unscattered photons
of the energy E in the detector
3.1.15
calibration factor per unit of surface area or unit of mass
w
ratio of the activity of surface area or unit of mass of the radionuclide to the net count rate of the total
absorption line
3.2 Symbols and units
For the purposes of this part of ISO 18589, the symbols and units defined in ISO 11929 and given in
Table 1 apply.
Table 1 — Symbols
Symbols Designation Unit
a Activity of a given radionuclide at the time of measurement
-2
a) per unit of surface area Bq ⋅ m
-1
b) per unit of mass Bq ⋅ kg
â
Best estimate of the measurand of the activity of the radionu-
clide in question
-2
a) per unit of surface area Bq ∙ m
-1
b) per unit of mass Bq ∙ kg
a Activity of the calibration standard at the time of measurement Bq
K
-2
a Activity of the radionuclide in question at the soil surface Bq ⋅ m
-2
a(ζ) Projected surface activity as a function of mass per unit at the Bq ⋅ m
surface of the soil
a* Decision threshold of the measurand of the radionuclide in ques-
tion at the time of measurement
-2
a) per unit of surface area Bq ⋅ m
-1
b) per unit of mass Bq ∙ kg
#
a Detection limit of the measurand of the radionuclide in question
at the time of measurement
-2
a) per unit of surface area Bq ∙ m
ISO 18589-7:2013(E)
Table 1 (continued)
Symbols Designation Unit
-1
b) per unit of mass Bq ∙ kg
Upper and lower limit of the confidence interval, respectively,
 
a a
,
of the measurand of the radionuclide in question at the time of
measurement
-2
a) per unit of surface area Bq ∙ m
-1
b) per unit of mass Bq ∙ kg
c , c c Quantities to determine the decision threshold and limit of -
0 1, 2
detection
d Distance between the calibration source and the geometrical m
centre of the crystal
-1
Ambient dose rate as air kerma rate Gy ⋅ h
•
D
E Photon energy keV
E −αx -
∞
e
1. order exponential integral function E α = dx
() ∫
x
E −αx -
∞
e
2. order exponential integral function E ()α = dx
∫
1 x
f Decay factor -
d
f Factor for converting the activity of a radionuclide to ambient
D
dose rate as air kerma rate
2 -1 -1
a) per unit of surface area Gy ⋅ m ⋅ h ⋅ Bq
-1 -1
b) per unit of mass Gy ⋅ kg ⋅ h ⋅ Bq
Factor for converting the activity of a radionuclide to ambient
f
•
dose equivalent rate
H*(10)
2 -1 -1
a) per unit of surface area Sv ⋅ m ⋅ h ⋅ Bq
-1 -1
b) per unit of mass Sv ⋅ kg ⋅ h ⋅ Bq
G Geometry factor
a) per unit of surface area -
-2
b) per unit of mass kg ⋅ m
G(E, V) Geometry function of photon energy, E, and distribution, V
a) per unit of surface area -
-2
b) per unit of mass kg ⋅ m
-1
•
The dose equivalent rate at a point in a radiation field that Sv ⋅ h
*
would be produced by the corresponding expanded and aligned
H ()10
field in the ICRU sphere at a depth, d (here 10 mm), on the radius
opposing the direction of the aligned field
Quantiles of the standardized normal distribution -
kk, , kk,
11--αβ 12-γ /
k Angular coefficient for photon irradiation from the polar angu- -
m
lar segment, m
M Number of polar angular segments -
m Index for polar angular segment -
n Total counts of the total absorption line -
g
4 © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
Table 1 (continued)
Symbols Designation Unit
n Background counts (under the region of the total absorption -
b
line)
n Net counts in the total absorption line -
n
p Emission probability per decay for the considered photon -
energy, E
R Radius of the distribution model m
R Radius of field of view m
s
u(x ) Standard uncertainty of the input quantity x The unit results from
i i
the input quantity.
Relative variance of the input quantity x The unit results from
i
ux
()
reli
the input quantity.
t Measuring time s
V Distribution model -
W Angular correction factor -
-2 -1
w Calibration factor to calculate the activity per unit of surface m or kg
area or mass of the radionuclide in question
w Calibration factor to calculate the radionuclide specific ambient -
h
dose equivalent rate
-2
ζ Mass per unit area kg ⋅ m
z Soil depth m
z′ Variable of integration of the soil depth -
ϑ Polar angle Degree
ε Detector efficiency
a) per unit of surface area m
b) per unit of mass kg
η Cross section of the detector for photons from the polar seg- m
m
ment, m
η Intrinsic efficiency m
External polar angle of the angular segment of interest Degree
ϑ
ext
Limit angle of the distribution model Degree
ϑ
lim
ϑ Internal polar angle of the angular segment of interest Degree
int
ϑ Aperture angle of the collimated spectrometer Degree
col
-1
μ Linear attenuation coefficient of air m
Air
2 -1
μ /ρ Mass attenuation coefficient of soil m ⋅ kg
S S
-3
ρ (z) Soil density as function of soil depth, z kg ⋅ m
S
-1 -2
Φ Density of flux of unscattered photons of energy E for distribu- s ⋅ m
tion model V at the detector location
Portion of flux density of unscattered photons of energy E -
 Δ 
Φ
m
resulting from polar angle segment m for distribution model V
 
Φ
 
EV,
at the detector location
-2
β Relaxation mass per unit area kg ⋅ m
ISO 18589-7:2013(E)
4 Principles
4.1 Measurement method
In situ gamma spectrometry is a direct, physical method for fast determination of activity per unit of
surface area or per mass unit of gamma-emitting radionuclides present in or deposited on the soil surface.
In situ gamma spectrometry can be considered as a screening method that can supplement soil sampling
with a subsequent gamma spectrometry in the laboratory, with the following advantages:
— no time-consuming sampling and no test sample preparation necessary for laboratory;
— short measuring time;
— immediate availability of results in the field;
— representativeness of the results for a fairly large area corresponding to the field-of-view of the detector.
During the measurement, the detector is positioned preferably with the end cap down on an assembly jig.
For quantitative analysis of the pulse height spectra, assumptions are made concerning the distribution
of radionuclides in soil, as well as the specific physical properties of the soil and the air.
Generally, the distribution of the radionuclides in soil is not known. The following ideal models are used:
— homogeneous distribution for natural radionuclides;
— surface deposition on the soil top layer for fresh, dry deposition of fallout;
— exponential decreasing activity concentration with increasing depth in soil following a fallout
surface deposition of activity and subsequent migration down into deeper soil layers.
NOTE For the description of the activity distribution in the soil, simple exponential models are mostly used.
According to the assumed distribution model, for homogeneously distributed radionuclides, the activity
is given in activity per unit of mass, whereas for artificial radionuclides, which are deposited on the
surface and afterwards have migrated into the soil, the results are reported in activity per unit area.
4.2 Uncertainties of the measurement method
Uncertainties of the measurement method are principally due to
— uncertainty of the distribution of the radionuclides on and in the soil,
— contribution from other sources (e.g. activity in the surrounding air, see Annex A).
[14]
The main influence quantities are listed in Annex B, with the numerical values given in reference.
5 Equipment
5.1 Portable in situ spectrometry system
An in situ gamma spectrometer consists of five main components, as listed below:
— high purity germanium detector or scintillation detector;
— pulse processing electronics;
— data recording and evaluation system;
— fixture for mounting the detector (e.g. tripod);
6 © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
— cooling and, if required, shielding.
A portable in situ spectrometry system is recommended. It consists of a portable cooling device and
electronics [the latter being a compact multichannel analyser system (MCA) with integrated high voltage
power supply and pulse processing unit. Today, pulse processing is preferably performed as digital pulse
processing]. Data transfer can be performed through telecommunication, e.g. by cable, radio, or satellite.
The spectral data are transferred via cable, WLAN, or radio communication to a PC and stored on a hard
disk or digital storage media (e.g. memory sticks, memory cards).
Since, in general, there is no power supply during the measurements in the field, it is useful that the
measurement equipment is equipped with internal batteries for a self-contained operation.
5.2 Detector System
5.2.1 General
The high purity germanium system (HPGe System) is described in ISO 18589-3 and IEC 61275. Depending
on the measurement objectives, two different types of germanium crystals (n type, p type) can be used.
They can be built with different shapes, crystal mountings, end cap, and end cap window materials. The
detector characteristics also define the measurement range, both in terms of gamma energy and count
rate. A summary of the specifications is given in Annex C.
However, it shall be stressed that detectors capable of measuring at very low energies (like n-type
detectors or detectors with special end cap materials) are not very useful for in situ measurements. This
is due to the fragility of the detector and the large uncertainties of the measured activities caused by the
high absorption of gamma radiation in the air and in the ground.
NOTE 1 Although quantitative measurements of radionuclides at low photon energies are not possible with
p-type HPGe detectors for in situ measurements, the use of n-type detectors or detectors with special end cap
materials provides the ability to identify radionuclides whose energies are below 60 keV.
For general applications, such as the determination of the activity concentration of naturally occurring
radioactive material (NORM) in ground or soil contamination by artificial radionuclides, it is
recommended to use germanium detectors with a relative detection efficiency of 20 % to 50 % and an
energy range above 50 keV.
NOTE 2 In case of emergency measurements with high dose rates above 20 µSv/h (high photon fluxes) smaller
germanium detectors with relative detector efficiency less than 20% are preferable.
It is recommended to use detectors which have an isotropic response function, i.e. detectors, which have
no or nearly no dependency on the direction of the incident photons. This is the case if the surface area of
the detector (i.e. its cross section perpendicular to the direction of the incident photon) is independent
of the incidence angle, i.e. if the diameter of the crystal is approximately the same as its length.
NOTE 3 For detectors with a strong directional dependency, it is preferable to use mathematical methods to
simulate detector efficiency since this dependency is inherently taken into account. On the other hand, these
detectors are advantageous in cases where a limited field-of-view is required.
Under certain conditions, scintillation detectors [NaI(Tl), LaBr ] can be used especially if high precision
is not required. In this case, no cooling is required but the nuclide threshold decision and detection limit
are higher due to lower energy resolution.
5.2.2 Field-of-view
The field-of-view of the detector is the soil surface area, from which 90 % of the unscattered detected
photons originate. This area depends on the characteristics of the detector, the measurement height,
the gamma energy, and the distribution of the radionuclide of interest in soil. The field-of-view is always
calculated for an infinite measurement area.
ISO 18589-7:2013(E)
5.2.3 Special requirements
The detector system shall comply with the special requirements for in situ measurements according to
IEC 61275. Specifically, the following topics shall be considered.
a) The system shall be humidity-proof and waterproof (splashing). This is especially true for all
mechanical and electrical connections between the preamplifier and multichannel analyser.
b) The crystal shall be mounted in the detector end cap in such a way that the mechanical stress of
detector transport does not result in any detector damage. This may mean that special transport
containers shall be used.
c) The operating temperature for the detector shall be in the range of −20 °C to +50 °C. (Higher
temperatures at the detector end cap may result in worse vacuum in the cap).
d) The capacity of the cooling system shall be sufficient for a complete operation time. In case of loss
of cooling (e.g. if the Dewar vessel for liquid nitrogen runs empty), the detector recycling time as
specified by the supplier shall be taken into account.
NOTE 1 If the detector is cooled by liquid nitrogen, transport activities result in higher nitrogen consumption.
NOTE 2 For standard applications, high-purity materials for detector mounting, end cap, and end cap window
are not required.
5.3 Pulse processing electronics
5.3.1 Components
The pulse processing system consists of the following components:
— detector high voltage power supply;
— spectroscopy amplifier;
— analog-to-digital converter (ADC);
— multichannel analyser (MCA).
Latest versions of commercial electronic units use digital electronics to process the pulses. In this case,
the spectroscopy amplifier and the ADC are substituted by a digital signal processor.
It is highly recommended to use integrated pulse processing units. In this case, all the individual electronic
components are integrated into one box, which in turn is connected to the detector preamplifier and a
personal computer (PC).
The connection to the PC can be done by a serial connection (cable), by USB (cable), by WLAN (wireless),
or by other types of radio communication (wireless). The PC should be battery operated.
5.3.2 Special requirements
The pulse processing electronics shall fulfil the following special requirements for in situ measurements;
if no digital signal processing is used, the system should be temperature stabilized. This can be done by
a digital spectrum stabilizer. Digital signal processors normally are not temperature sensitive; hence,
stabilization is not required.
NOTE Stabilization can be done using the gamma line of K at 1 461 keV.
It is preferable to use battery-operated electronics. The minimum operation time of the batteries should
be 4 hours. Switching between battery and mains operation should be possible.
8 © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
5.3.3 Requirements for the evaluation program
Software programs for evaluation of spectra of an in situ spectrometer shall have additional functionalities
compared to those typically used in laboratory applications. These additional functions can be achieved
by special add-on programs or modules. The following basic functions shall be available:
— performing energy calibration and, if required, energy stabilization;
— automatic peak location and peak area quantification. There should be the possibility of manual
interaction (defining peak regions, etc.). The peak area quantification includes calculation of
the peak position, the peak FWHM, the peak net area, and the peak area uncertainty. Multiplet
deconvolution shall be possible;
— radionuclide identification algorithm, using a radionuclide library, which can be edited by
competent users. The radionuclide identification includes calculation of radionuclide activities,
decision thresholds, and detection limits according to ISO 11929. The algorithm shall also perform
interference corrections for interfering radionuclide lines. The activities, decision thresholds, and
detection limits shall be calculated for any user specified reference date.
Additional functions may be useful, such as the following:
— determination of the angular correction factor, W, of the detector;
— modification of the detector height above ground;
−2
— computation of the activity, in Bq·m , for each radionuclide exponential distribution in the soil, with
−2 −2
the possibility of variation of the relaxation mass per unit area from at least 3 kg·m to 150 kg·m ;
−2
— computation of the activity, in Bq·m , for each radionuclide deposited on the soil surface;
−1
— computation of the activity, in Bq·kg , for radionuclide which are homogeneously distributed in the soil;
— computation of the ambient dose rate at a height of 1 m above ground. The software shall allow to
edit the factor f or f which is used to convert the area or mass specific activity into air kerma
D
•
H*(10)
rate or ambient dose equivalent rate in air.
5.4 Assembly jig for a detector system
The detector mounting should be able to position the detector system at different heights. The assembly
should be built from materials with a low atomic number and low density (aluminium, plastic material,
wood). The assembly should have low intrinsic activity concentration. Usually, the detector is mounted
at a height of 1 m.
Most mounting assemblies are constructed as tripods.
5.5 Collimated detector
5.5.1 Construction
An in situ gamma spectrometer equipped with a collimated detector is a special case of an in situ gamma
spectrometer. The collimator reduces the field-of-view of the detector. The collimator defines the solid
angle of detection which delineates a finite measurement area at the surface of soil. It allows filtering the
flux of photons from outside this measurement area.
NOTE Typical fields of application of in situ gamma spectrometer with collimated detector are:
— activity measurement with a reduced field-of-view,
— activity measurement in case of external radiation influence (e.g. airborne activity),
ISO 18589-7:2013(E)
— increase of the upper measurement limit (intensity of the radiation field, see B.10), and
— measurements inside the nuclear facilities.
In situ gamma spectrometer with a collimated detector consists of a portable detector with a cylindrical
shape collimator (see Figure 1).
The design of the collimator depends on the objectives of the in situ measurement and on the local
conditions (energy and intensity of external radiation fields that have to be attenuated). The collimator
is characterized by the aperture angle and the mass per unit area.
Key
1 axis of symmetry
2 rear shielding
3 detector
4 lateral shielding
5 detector crystal
Figure 1 — Diagram of arrangement of detector and cylindrically designed collimator
The wall thickness of the collimator is typically 25 mm to 60 mm when lead is used as the shielding
material. The housing of the detector is enclosed by the collimator (typical distance 5 mm). A back shield
may enhance the shielding effect.
The axis of symmetry of the detector and the axis of the collimator are identical. The position of the
detector inside the collimator shall be adjusted reproducibly.
10 © ISO 2013 – All rights reserved

ISO 18589-7:2013(E)
5.5.2 Collimator parameter
5.5.2.1 Aperture angle
The aperture angle ϑ is mainly dependent on collimator construction, dimensions and material, as
col
well as on its position in relation to the detector.
The aperture angle is defined by the radius of the field-of-view of the collimated spectrometer for a
photon energy of 662 keV, an extensive and infinite surface contamination and a detector height of 1 m
above ground.
NOTE 1 The range of the aperture angle of a collimator is typically from 40° up to 70°. The aperture angle ϑ
col
is calculated with the radius R of the field-of-view of the collimated detector (see Annex D).
s
Rs 
ϑ =arctan (1)
col  
d
 
NOTE 2 The field-of-view of the collimated detector gives no reliable indication for the measurement area in
case of higher photon energies. The aperture angle of the collimator is different from the aperture angle defined
by the technical layout of the collimator.
5.5.2.2 Mass per unit area
The mass per unit area of a collimator, ζ , is given for a polar angle of 90°. It is important for shielding
col
of the external radiation (radiation background).
-2 -2
NOTE The range of the mass per unit area is typically from 200 kg ⋅ m up to 900 kg ⋅ m .
5.5.2.3 Materials
For the construction of collimators, material of high density and high atomic number is used. Those
materials are lead, tungsten (sintered), and copper. Materials used for the construction of collimators
are shown in Table 2.
NOTE For photon energies above 100 keV, the influence of the density is stronger than that of the atomic
number. High-density materials may reduce the mass of the collimator by reduced wall thickness at constant
shielding effect.
For reduction of the radiation intensity in
...