ISO 24953:2026

International
Standard
ISO 24953
First edition
Textiles — Determination of iodine
2026-07
isotope adsorption efficiency of
activated carbon fibre
Textiles — Détermination de l'efficacité d'adsorption des isotopes
d'iode par la fibre de carbone activé
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Reagents and materials . 5
7 Preparation of test specimens . 6
8 Test procedure . 6
8.1 Test condition .6
8.2 Canister preparation .7
8.2.1 General .7
8.2.2 Procedure for canister preparation .7
8.3 Procedure for leakage test .7
8.3.1 General .7
8.4 Stabilization period .8
8.5 Pre-equilibrium period .8
8.6 Equilibrium period.8
8.7 Adsorption period .8
8.8 I radiation injected during one test .9
8.9 Desorption period .9
8.10 Collection of activated carbon fibre and charcoal .9
8.11 Measurement .9
9 Calculation . 9
9.1 Penetration rate .9
9.2 Adsorption efficiency of test bed(E) and back-up bed (E ) .10
b1
9.3 I adsorption capacity of activated carbon fibre .10
9.4 Standard deviation of penetration.10
9.5 Counting conditions .11
9.6 Gamma count correction .11
10 Test report .11
Annex A (normative) Test system . .12
Annex B (informative) Test procedure and test results .16
Bibliography . 19

iii
Foreword
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iv
Introduction
Activated carbon fibre with a large specific surface area has excellent adsorption efficiency of iodine isotope
(I ). Therefore, standards for suitable adsorption efficiency test methods reflecting the geometric shape
and physical and chemical properties of activated carbon fibres are needed. The development of reliable test
methods that can objectively compare activated carbon fibres with non-fibrous activated carbon adsorption
efficiency will help boost the activated carbon fibre market for producers and consumers.

v
International Standard ISO 24953:2026(en)
Textiles — Determination of iodine isotope adsorption
efficiency of activated carbon fibre
1 Scope
This document specifies a method of testing the adsorption efficiency of activated carbon fibres, such as
nonwoven fabric or fibrous felt with a thickness of less than 20 mm for adsorption and removal of iodine
isotopes (I ), included in air or gas flow (exhaust).
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.
ASTM D3803-91, Standard Test Method for Nuclear-Grade Activated Carbon
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
packing density
ρ
p
weight of an activated carbon fibre specimens packed in the Labyrinth typed canister, calculated as
(1)
where
ρ is the packing density (g/cm );
p
W is the weight conversion value obtained by multiplying the mass of activated carbon fibre
m
specimens charged in a canister or guide with the same packing density and geometric shape
as measured by an electronic scale by gravitational acceleration (g);
V is the volume of the specimen filling part of the canister (cm ).
c
Note 1 to entry: The definition and measurement of the packing density of activated carbon fibre specimens packed in
labyrinth type canisters with a depth of (20 ± 0.2) mm and a bed diameter (50 ± 0.1) mm are obtained. In calculating
the packing density, the space between individual activated carbon fibre specimens packed in the canister or between
the specimen and the canister wall is completely compacted without any gaps using a pressurizer in this document's
test method.
4 Principle
The test specimens are stacked into the test canister and installed in the test facility along with back-up
layer canisters, which function as filters to capture as much methyl iodide isotope as possible. And a high-

humidity air stream containing the methyl iodide isotope is passed through the canisters. After adsorption
occurs in both the test specimens and the back-up layers, the supply of methyl iodide isotope is stopped. The
canisters are then removed from the test facility, and the test specimens are transferred into gamma-ray
detector samplers. The radiation levels are measured individually, and the penetration rate and adsorption
efficiency of the activated carbon fibre layer under test are calculated.
5 Apparatus
5.1 Punching cutter, that can cut a disk sheet-shaped specimen with a diameter of (50 ± 0,1) mm as
shown in Figure 1.
Key
1 rotary handle
2 support post
3 cutting blade
4 adjust bolt
5 slide adjust bolt
6 metal base
7 test specimen
8 ID: (50 ± 0,1) mm
Figure 1 — Punching cutter
5.2 Tweezers, soft-tipped tweezers, with a minimum length of 100 mm to evenly stack disc sheet-shaped
specimens without damage.
5.3 Cylinder-type stacking guide, made of transparent material and has a smooth inner wall surface, an
inner (test bed) diameter of (50 ± 0,1) mm, a depth of (20 ± 0,2) mm, a wall thickness of (2 to 3) mm, and the
inner volume is the same as the inner volume of the canister used in the same test as shown in Figure 2 and
Annex B, B.1.1. The guide is designed to rotate the male screw on the lower part, fit it into the upper part
of the canister so that transfer the specimen stacked in the guide into the canister, and then detach it. The
packing volume, mass and geometric shape of the specimen filled in the guide is almost the same as that of

the canister. The geometric uniformity of the filling shape of the specimens reduces the error of the gamma-
ray detector results for comparative measurement of iodine isotope adsorption efficiency.
Key
1 test specimen
2 guide
3 pressuriser
Figure 2 — Cylinder-type stacking guide
5.4 Pressurizer, with a length of (80 to 100) mm, a weight of (160 to 200) g, and disk shape bottom with a
diameter of (48 ± 0,5) mm as shown in Figure 3. The test specimen is geometrically uniformly stacked inside
the guide and canister as shown in Clause B.2. It is also used to uniformly fill test specimens that are not
shaped like disk sheets.
Figure 3 — Pressuriser
5.5 Electronic scale, with the measuring range of 0,01 mg to 250 g and 0,1 % precision.
5.6 Canister, with the height of (20 ± 0,2) mm and an inner diameter of (50 ± 0,1) mm with a labyrinth
surface in the inner wall of a depth of (0,5 ± 0,1) mm and an interval of (2 ± 0,2) mm as shown in Figure 4 and
Figure 5. The labyrinth surface of inner canister is provided to prevent leakage between the stacked test
specimen and the wall of the canister.
Figure 4 — Canister
a) Single layer specification b) Multi-layer connection configuration

Key
1 bed holder
2 adsorption media
3 O-ring gland
4 test specimen
5 retaining snap ring (both ends)
6 baffle (both ends)
7 holes for assembly tie-rods (four)
8 screw thread
9 bed ID
10 baffle ID
11 canister (four shown)
12 inlet cap
13 outlet cap
14 thermocouple
15 thermocouple fitting
16 static tap
17 tie bar (four)
18 gas inlet
19 gas outlet
Figure 5 — Canister multi-layer connection configuration
5.7 Gamma ray detector, multi-channel gamma spectrometer is using NaI detectors at 365 keV energy
positions. The detector should typically exhibit an energy resolution of approximately 7 % full width at
half maximum (FWHM) at 662 keV (Cs , as a typical performance benchmark). The actual count value
of the gamma photons (not an analogue rate) shall be obtained, and any disturbing factors (such as high
background or other radiation effects) shall be removed appropriately. This measurement system shall have
the ability to calculate and correct dead time, measurement efficiency, collapse rate, etc. using an internal
computer. The characteristics of the I energy spectrum obtained depend on the measurement results,
first, if there are few gamma-ray emission impediments, then the whole spectrum, including the main
energy I spectrum or Compton effect, is available at 364,46 keV. In addition, the assembly of the canister
shall consist of three layers of test layer, back-up layer and charcoal background and shall be measured
under the same geometric conditions, and a jig is installed on the detector to place each measuring vessel in
approximately the same position (±1 mm).
3 3
5.8 Gamma-ray measuring sampler, made of plastic with the volume of 50 cm to 100 cm .
5.9 Operation test system, is shown in Annex A with the operating conditions. Because of the handling of
isotope, the safety shall be extremely important. Pay attention to the following warning, on working on this
operation test system and especially on the test procedure 8.8.
6 Reagents and materials
6.1 Air, oil-free type compressor shall be used for air supply systems to minimize injection of hydrocarbons
or any particles into the system. Intake line filters shall consist of a dryer, activated carbon, and HEPA filters
and shall be adequately sized and maintained.
6.2 Water, deionized or distilled water shall be used to generate water vapour.
6.3 Radioactive methyl iodide, tracers which is synthesized as the following.
127 131 131 127
CH I + NaI CH I + NaI
3 3
This reaction proceeds via isotopic substitution through an nucleophilic substitution reaction (SN )
mechanism, where I¹³¹ replaces I¹²⁷ in the CH₃I molecule. This shortens the synthesis time and reduces
radiation exposure risk due to volatile material leakage during distillation.
In the reaction, the solubility of CH I in water is as small as 14 g/l (20 °C) and the specific gravity in water
is 2,28. So when the CH I and NaI solutions are mixed, the CH I layer is located under the vial. In CH I,
3 3 3
131 131 127
the substitution of radioactive I in the NaI solution layer or CH I layer as a well-reacting secondary
131 127
nucleophilic substitution reaction (SN ) results in CH I in the non-radioactive CH I layer, using
2 3 3
127 131 131
radioactive methyl iodine (a mixture of CH I and CH I ) in the lower CH I layer containing this CH I
3 3 3 3
as the tracer.
In addition, CH I with a boiling point of 42,5 °C shall be stored at low temperature as the vapour pressure
increases when handling the test specimen container. The CH I tracer is ionized by I of radioactive energy
to form I . The self-degrading resulting brown I ionizes (I -) to Na S O , maintaining a high chemical purity
2 2 3 2 2 3
of CH I in the tracer.
The methyl iodine solution shall be stored in a dark place below 0 °C to minimize decomposition into
elemental iodine (I ).
6.4 Adsorbents
6.4.1 Test layer adsorbent, the adsorbent of I for the test layer is the activated carbon fibres as the test
specimens. The test specimens are nonwoven fabric or loose fibre in the form of disk sheets with a thickness
of (20 ± 0,2) mm or less.
6.4.2 Back-up layer adsorbent, charcoal or activated carbon fibres are used. The absorbent with an I
adsorption rate of 97 % or more are used in each back-up layer.
The test specimen preparation and packaging method of charcoal (impregnated granular activated carbon)
in a back-up canister shall conform with the standard methods specified in the guidelines for sampling
granular activated carbon in ASTM D3803-91.
7 Preparation of test specimens
The test specimens are cut into disks with diameter of 50 mm ± 0,1 mm by using a punching cutter (5.1).
from the activated carbon sample fabric sheet. After drying the disk-shaped test specimens in a convection
oven at 110 °C for 5 hours, cool it 3 hours in a desiccator containing a silica gel absorbent, and measure the
weight of the test specimens under moisture reduction.
The disk-shaped test specimens are packed in the test canister (5.6) with a thickness of less than 20 mm.
The mass of the test specimen fully filled in the canister shall be obtained by subtracting the mass of the
guide measured in advance from the total mass of the guide and filled test specimens and recorded.
8 Test procedure
8.1 Test condition
The test conditions of the canister test system are temperature (30 ± 0,4) °C, absolute pressure (101 ± 5)
kPa, flow rate (24 ± 0,5) m/min, relative humidity (93 to 96) % and face velocity (12 ± 0,2) m/min.
Refer to ASTM D3803-91 for other specifications and operating conditions which are not specified in this
document, except for the canister test system portion of the entire test system.
The test conditions shall be monitored at 5 min intervals on temperature, pressure, relative humidity,
and flow rate continuously. When measuring the temperature at the top and bottom of the test layer, the
experiment is stopped if the air temperature at the top of the layer decreases or a pressure drops throughout
the layer.
WARNING — The facilities for this testing shall provide an air conditioning system equipped with a
filter that adsorbs and removes radioactive substances and the ventilation air in the testing facility
shall be maintained below 1 mSv/yr, which is the allowable concentration limit of the radioactive
iodide isotope (I ). Entry into the facilities for this testing is strictly controlled except for permitted
testing personnels.
WARNING — The testing personnel shall comply with IAEA's radiation practice technical manual
[1]
and IAEA Safety Standards Series No. GSR Part 3 , wear a radiation shield protective suit, have a
personal dosimeter, and monitor at all times. Thyroid physical examination shall be performed on a
regular basis and training in health and physical procedures shall be performed.
8.2 Canister preparation
8.2.1 General
For the purpose of securely filling multiple disk sheet-shaped test specimens (processed using a punching
cutter) into the canister, several apparatus (a cylinder-type stacking guide, pressurizer, and
...