prEN ISO 18589-7

SLOVENSKI STANDARD
01-oktober-2025
Merjenje radioaktivnosti v okolju - Tla - 7. del: Meritve radionuklidov, ki sevajo
žarke gama, na kraju samem (ISO/FDIS 18589-7:2025)
Measurement of radioactivity in the environment - Soil - Part 7: In situ measurement of
gamma-emitting radionuclides (ISO/FDIS 18589-7:2025)
Ermittlung der Radioaktivität in der Umwelt - Erdboden - Teil 7: In-situ-Messung von
Gammastrahlung emittierenden Radionukliden (ISO/FDIS 18589-7:2025)
Mesurage de la radioactivité dans l'environnement - Sol - Partie 7: Mesurage in situ des
radionucléides émetteurs gamma (ISO/FDIS 18589-7:2025)
Ta slovenski standard je istoveten z: prEN ISO 18589-7
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.

FINAL DRAFT
International
Standard
ISO/FDIS 18589-7
ISO/TC 85/SC 2
Measurement of radioactivity in the
Secretariat: AFNOR
environment — Soil —
Voting begins on:
Part 7:
In situ measurement of gamma-
Voting terminates on:
emitting radionuclides
Mesurage de la radioactivité dans l'environnement — Sol —
Partie 7: Mesurage in situ des radionucléides émetteurs gamma
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 18589-7:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 18589-7:2025(en)
International
Standard
ISO/FDIS 18589-7
ISO/TC 85/SC 2
Measurement of radioactivity in the
Secretariat: AFNOR
environment — Soil —
Voting begins on:
Part 7:
In situ measurement of gamma-
Voting terminates on:
emitting radionuclides
Mesurage de la radioactivité dans l'environnement — Sol —
Partie 7: Mesurage in situ des radionucléides émetteurs gamma
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ISO/FDIS 18589-7:2025(en) © ISO 2025

ii
ISO/FDIS 18589-7:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 Principles . 6
5.1 Measurement method .6
5.2 Uncertainties of the measurement method .7
6 Equipment . 7
6.1 Portable in situ spectrometry system .7
6.2 Detector system.7
6.2.1 General .7
6.2.2 Field-of-view .8
6.2.3 Special requirements.8
6.3 Pulse processing electronics .8
6.3.1 Components .8
6.3.2 Special requirements.9
6.3.3 Requirements for the evaluation program .9
6.4 Assembly jig for a detector system .10
6.5 Collimated detector .10
6.5.1 Construction.10
6.5.2 Collimator parameter .11
7 Procedure .12
7.1 Calibration . 12
7.2 Method of combined calibrations . 13
7.2.1 General . 13
7.2.2 Intrinsic efficiency .14
7.2.3 Geometry factor .14
7.2.4 Angular correction factor . 15
7.2.5 Numerical calibration procedure .16
8 Quality assurance and quality control program . 17
8.1 General .17
8.2 Influencing variables .17
8.3 Instrument verification .17
8.4 Method verification .17
8.5 Quality control program .18
8.5.1 General .18
8.5.2 Description of periodical quality checks .18
8.5.3 Measurement verification .18
8.5.4 Qualification .18
8.5.5 Documentation of quality controls .19
8.6 Standard operating procedure .19
9 Expression of results . 19
9.1 Calculation of activity per unit of surface area or unit of mass .19
9.2 Calculation of the characteristic limits and the best estimate of the measurand as well
as its standard uncertainty .19
9.2.1 General .19
9.2.2 Standard uncertainty . 20
9.2.3 Decision threshold and detection limit . 20
9.2.4 Limits of coverage interval and best estimate of the measurand .21

iii
ISO/FDIS 18589-7:2025(en)
9.3 Calculation of the radionuclide specific ambient dose rate .21
10 Test report .23
Annex A (informative) Influence of radionuclides in air on the result of surface or mass activity
measured by in situ gamma spectrometry .24
Annex B (informative) Influence quantities .25
Annex C (informative) Characteristics of germanium detectors .28
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.30
Annex E (informative) Methods for calculating geometry factors and angular correction factors .34
Annex F (informative) Example for calculation of the characteristic limits as well as the best
estimate of the measurand and its standard uncertainty .42
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 .46
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

iv
ISO/FDIS 18589-7:2025(en)
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 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee, TC 85, Nuclear energy, nuclear technologies, and
radiological protection, Subcommittee SC 2, Radiological protection, in collaboration with the European
Committee for Standardization (CEN) Technical Committee CEN/TC 430, Nuclear energy, nuclear technologies,
and radiological protection,in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 18589-7:2013), of which it constitutes a minor
revision.
The main changes are as follows:
— B.10: correction of the information related to the activity concentration of 40 K;
— E.2 and E.6: correction of Formulae (E.5) and (E.11);
— F.4 : correction of β, according to the numerical values of the example;
−2 −2
— F.6: modify β = 50 g cm into β = 50 kg m ;
-2 -2 -2 -2
— G.3, Footnote 1 of Table G.3: modify 1 g cm = 10 kg cm into 1 g cm = 10 kg m .
A list of all parts in the ISO 18589 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
ISO/FDIS 18589-7:2025(en)
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.

vi
FINAL DRAFT International Standard ISO/FDIS 18589-7:2025(en)
Measurement of radioactivity in the environment — Soil —
Part 7:
In situ measurement of gamma-emitting radionuclides
1 Scope
This document 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 document 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 document can be used in connection with radionuclide measurements of soil samples in the laboratory
(see 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 document 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 are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 11929 (all parts), Determination of the characteristic limits (decision threshold, detection limit and limits of
the coverage interval) for measurements of ionizing radiation — Fundamentals and application
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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO/FDIS 18589-7:2025(en)
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
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.
3.2
detector efficiency
η (E)
efficiency in the direction of the crystal symmetry axis as a function of the photon energy, E
3.3
detector height
d
distance between the geometrical centre of the crystal and the soil surface
3.4
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
3.5
relative detection efficiency
ration expressed in percentage, of the count rate in the Co 1 333 keV total absorption peak to the one
obtained with a 7,62 cm × 7.62 cm (3 in × 3 in) NaI(Tl) scintillator for normal incidence and at 0,25 m from
the source
3.6
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
3.7
aperture angle
ϑ
col
characteristic angle for an in situ gamma spectrometer with collimator
3.8
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 %).
Note 2 to entry: See also Reference [7].
3.9
field-of-view
soil surface area, from which 90 % of the unscattered photons are detected by the detection device

ISO/FDIS 18589-7:2025(en)
3.10
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
3.11
angular coefficient
k
m
factor taking into account the angular response of the detector and the angular distribution of the incident flux
3.12
measurement area
area in the soil and/or on the soil surface having radionuclide activity per unit of surface area or unit of mass
3.13
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.
Note 2 to entry: See also Reference [7].
3.14
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
3.15
calibration factor
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
4 Symbols
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
Activity of the calibration standard at the time of measure-
a Bq
K
ment
−2
a Activity of the radionuclide in question at the soil surface Bq·m
Projected surface activity as a function of mass per unit at the
−2
a ζ
() Bq·m
surfaceof the soil
*
a Decision threshold of the measurand of the radionuclide in
question atthe time of measurement
−2
a) per unit of surface area Bq·m
−1
b) per unit of mass Bq·kg
ISO/FDIS 18589-7:2025(en)
#
Detection limit of the measurand of the radionuclide in ques-
a
tion at the time of measurement
−2
a) per unit of surface area Bq·m
−1
b) per unit of mass Bq·kg
 
Upper and lower limit of the probabilistically symmetric cov-
a , a
erage interval, respectively, of the measurand of the radionu-

clide in question at the time of measurement
−2
a) per unit of surface area
Bq·m
−1
b) per unit of mass Bq·kg
Quantities to determine the decision threshold and limit of
cc,, c
—
01 2
detection
Distance between the calibration source and the geometrical
d m
centre of the crystal
•
-1
Ambient dose rate as air kerma rate Gy⋅h
D
E Photon energy keV
−αx
—
∞
e
E
1. order exponential integral function E α = dx
()
∫
x
−αx
—
∞
e
E
2 2. order exponential integral function E ()α = dx
∫
x
f Decay factor —
d
f Factor for converting the activity of a radionuclide to ambient
D
dose rate as air kerma rate
-2 -
a) per unit of surface area Gy⋅m ⋅h
1 -1
⋅Bq
b) per unit of mass
-1 -1
Gy⋅kg⋅h ⋅Bq
f
Factor for converting the activity of a radionuclide to ambient
•
*
H ()10 dose equivalent rate
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 function of photon energy, E, and distribution, V
a) per unit of surface area —
-2
b) per unit of mass kg⋅m
GE(),V
Geometry function of photon energy, E, and distribution, V
a) per unit of surface area —
-2
b) per unit of mass kg⋅m
The dose equivalent rate at a point in a radiation field that
•
would be produced by the corresponding expanded and
-1
Sv⋅h
*
H 10
() aligned field in the ICRU sphere at a depth, d (here 10 mm), on
the radius opposing the direction of the aligned field
kk,,kk, ,,kk Quantiles of the standardized normal distribution —
11−−αβ 12−γ/ pq
Angular coefficient for photon irradiation from the polar —
k
m
angular segment, m
ISO/FDIS 18589-7:2025(en)
M Number of polar angular segments —
m Index for polar angular segment —
n Total counts of the total absorption line —
g
Background counts (under the region of the total absorption —
n
b
line)
n Net counts in the total absorption line —
n
Emission probability per decay for the considered photon —
p
energy, E
R Radius of the distribution model m
R Radius of field of view m
s
the unit
results from
ux() Standard uncertainty of the input quantity x
i i
the input
quantity.
the unit
results from
Relative variance of the input quantity x
ux()
i
reli
the input
quantity.
t Measuring time s
V Distribution model —
W Angular correction factor —
Calibration factor to calculate the activity per unit of surface
-2 -1
w m or kg
area or mass of the radionuclide in question
Calibration factor to calculate the radionuclide specific ambi-
w —
h
ent 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
Cross section of the detector for photons from the polar seg-
η m
m
ment, m
η
Intrinsic efficiency m
ϑ External polar angle of the angular segment of interest degree
ext
ϑ Limit angle of the distribution model degree
lim
ISO/FDIS 18589-7:2025(en)
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
μρ/
Mass attenuation coefficient of soil m ⋅kg
SS
-3
ρ ()z Soil density as function of soil depth, z kg⋅m
s
Density of flux of unscattered photons of energy E for distri-
-1 -2
Φ
s ⋅m
bution model V at the detector location
Portion of flux density of unscattered photons of energy E
ΔΦ
 
m
resulting from polar angle segment m for distribution model —
 
Φ
 
EV,
V at the detector location
-2
β Relaxation mass per unit area kg⋅m
distribution function of the standardized normal distribu-
φ()t
—
tion; φ kp= applies
()
p
5 Principles
5.1 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.

ISO/FDIS 18589-7:2025(en)
5.2 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).
The main influence quantities are listed in Annex B, with the numerical values given in Reference [14].
6 Equipment
6.1 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);
— cooling, as applicable, 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.
6.2 Detector system
6.2.1 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 should 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

ISO/FDIS 18589-7:2025(en)
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.
6.2.2 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.
6.2.3 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.
6.3 Pulse processing electronics
6.3.1 Components
The pulse processing system consists of the following components:
— detector high voltage power supply;
— spectroscopy amplifier;
— analog-to-digital converter (ADC);

ISO/FDIS 18589-7:2025(en)
— 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.
6.3.2 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 h. Switching between battery and mains operation should be possible.
6.3.3 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 (series). 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 the
−2 −2
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 rate or
•
D
*
H ()10
ambient dose equivalent rate in air.

ISO/FDIS 18589-7:2025(en)
6.4 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.
6.5 Collimated detector
6.5.1 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 measure
...