BS ISO 18417:2017 pdf download – Iodine charcoal sorbents for nuclear facilities — Method for defining sorption capacity index
5 Preparation of the test
5.1 General
Based on the typical arrangement proposed in Clause 4, the test involves the following stages.
5.2 Removal of air impurity and humidity into the installation
Removing air pollutant and controlling humidity and temperature are important for the tests because these parameters can have a significant impact on the results. In order to clean the installation before a new test, the indoor air is passed through an aerosol filter, dehumidifier and charcoal filter to remove particulates, humidity and some volatile compounds. As an example, dehumidifier with zeolite warms at the temperature 350 °C to 400 °C in vacuum during 6 h and activated carbon to warm at temperature 300 °C to 350 °C in vacuum during 6 h in order to avoid degradation of the charcoal properties.
5.3 Radioactive methyl iodide used for sorbent testing If radioiodide is supplied in ready-to-use form of radioactive methyl iodide (CH 3 131 I) received from producer, a certificate date and activity shall be required. It shall be stored in a dark place at conditions that slows down the process of its decomposition into the molecular form (I 2 ). Otherwise, methyl iodide labelled with 131 I isotope is produced by its isotopic exchange (e.g. with Na 131 I or K 131 I without carrier). Its activity shall be defined and specified with a date. For this purpose, 2 cm 3 of methyl iodide are injected into the container with Na 131 I or K 131 I and kept at a room temperature of 20 °C for 48 h. To define the mass activity concentration (Bq/g), three portions of 5 g of activated carbon impregnated with triethylenediaminne (TEDA) are weighed and placed in weighing bottles, the diameter of which is close to that of the test column. Three samples of 4 µl of radio-labelled methyl iodide are taken and placed into weighing bottles with activated carbon. Activities of resulting samples are measured and correlated with methyl iodide mass that is defined as the volume of samples taken and methyl iodide density at the temperature of its storage. Mean value of mass activity concentration is calculated. The mass activity concentration (expressed in Bq/g) is used for calculation of the mass concentration of methyl iodide in the gas flow (see Formula 8).
5.4 Preparation of sorbent samples Range of granulated/crushed grains sizes and bulk density ρ sorb of the sorbent sample are determined if these data are absent. The methods used to determine grains size and the bulk density are defined according to a national or international standard. When filing each section of the column, the filling shall be made uniformly in each section such that similar mass in each section is obtained, without specific compression or vibration. The sectional column is used to conduct the sorbent test. Examples of such column and of a small section inside the column are shown in Figure 2 and Figure 3.
The number of sections has to be adapted with regard to the uncertainties of the measurement.
5.5 Measuring devices
The uncertainties of the following measurement devices shall be known:
— temperature sensors;
— pressure sensors,
— relative humidity sensors;
— gamma activity detectors;
— flow rate sensors.
Typical uncertainties are given in 9.3.
5.6 Conditions for achieving equilibrium during the test
Prior to testing the sorbent in the sectional column, test conditions shall be maintained such that the conditions for the equilibrium of water vapours inside the samples are achieved (humidifier conditions at gas flow velocity, Q col ). This is generally done in 16 h for around 15 cm thickness of sorbent.
5.7 Safe conditions for workers and members of the public The tests use a radioactive form of iodine. Thus, the tests shall be performed following national radiation protection regulations (for workers and members of the public) in force in the country. All the handling with radioactive iodine solutions and iodine vapours shall be performed under protective glove boxes. The glove box should be in a negative pressure enough to avoid to spread contaminated flows to the rooms.BS ISO 18417 pdf download.