Qualification of a precision pattern dispenser

The European Commission Joint Research Centre in Geel (JRC-Geel) is on a regular basis preparing radioactive sources. These sources can be used as calibration standards or reference sources in different applications, e.g. proficiency testing of laboratories monitoring radioactivity in the environment organized by JRC-Geel. In order to automate the sample preparation process a precision pattern dispenser was designed to reproducibly dispense radioactive solutions. The set-up should be able to dispense pre-set amounts of stock solution in an automated and reproducible way in predefined positions or patterns. Correct dispensing should be ensured by defining the positions of ampoules or special source holders precisely. The set-up must also be able to dispense pre-set amount of liquid according to designed patterns on air filters having a maximum size of 60x60 cm. During all manipulations no evaporation of stock solution can be afforded in order not to compromise its concentration. The liquids to be handled are mainly acidic solutions so all parts must be resistant to the acidic environment. The number of instrument parts that come in contact with the radioactive solution must be kept to a minimum to limit the amount of radioactive waste and should be easily replaceable. The precision pattern dispenser is composed of a commercially available sample handling unit that makes use of syringes to handle the liquid. This unit is coupled to an XYZ-table where e.g. air filters can be fixed on. A custom-made interface (protocol generator software) is used to design dispensing patterns on filters of different sizes and shapes. The combination of the filter and the pattern, called protocol, is sent to the software steering the sampling unit and the XYZ-table. The mass or volume to be dispensed and the position where it has to be dispensed is easily introducible and made visible in the protocol generator. Qualification tests were conducted to evaluate the performance of the instrument and to assess the compliance with the requirements. The two most important parameters to be tested were trueness and precision. The maximum values according to the specifications were 2 % for trueness and 1 % for precision. Tests were performed by dispensing water into glass ampoules. All other parameters described above were examined and found to be compliant with the specifications. The results of the tests demonstrate that the precision pattern dispenser can dispense liquid within the required specifications. The instrument can be used to spike air filters with an almost homogenous distribution of activity within a predefined area. The precision pattern dispenser makes it possible to prepare sources for different applications in a fast and accurate way.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

Evaluation of the 2017 EC Proficiency Test on 131I, 134Cs and 137Cs in maize powder

A proficiency test (PT) on the measurements of I-131, Cs-134 and Cs-137 in maize powder was organised by European Commission Directorate-General (EC DG) Joint Research Centre in Geel on request of the EC DG for Energy. This PT was an integral part of the EC's work of realising verification of Member State's obligations towards Article 35 of the Euratom Treaty. It serves also as a quality control programme which JRC-Geel is coordinating in order to assess the quality of the results collected in the Radioactivity Environmental Monitoring (REM) database. The PT reference material was prepared by spiking blank maize powder. The samples were sent to 123 laboratories of which 120 laboratories submitted their results. The evaluation of the PT results was performed according to ISO 13528:2015. The zed (z) and zeta (ζ) and En scores, were calculated. The z scores of the reported results for I-131 were acceptable for 92% of laboratories. For both Cs-134 and Cs-137 they were acceptable for 94% laboratories. The ζ scores were satisfactory for 66%, 56% and 68% of results for I-131, Cs-134 and Cs-137 respectively. In case of En score the number of consistent results was the same as for ζ score.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Evaluation of EC Measurement Comparison on Simulated Airborne Particulates - 137Cs in Air Filters

This report describes the full life cycle of the measurement comparison of 137Cs in air filters among 43 European laboratories monitoring radioactivity in the environment. Gravimetrically pipetting droplets of a gravimetrically diluted standardised 137Cs solution onto real air filters, SI-traceable reference values were established for intercomparison filters carrying a large range of activity close to the routine measurement conditions of the corresponding laboratory. The sample preparation and measurement processes applied in the participating laboratories are described and the results of the intercomparison are presented and discussed in detail. The results point at some problems of radioactivity measurement in air filters which need to be improved by several laboratories. Overall, with 41 out of 48 reported measurement results lying within +/- 33 % of the IRMM reference value, this comparison renders a rather fair result.JRC.D.4-Isotope measurement

The 55Fe half-life measured with a pressurised proportional counter

The half-life of 55Fe has been measured accurately by following the decay curve of three sources with a large pressurised proportional counter. An argon(90%)-methane(10%) mixture was used as counter gas, at atmospheric pressure (∼1 × 105 Pa) and at enhanced pressures of 5 × 105 Pa and 8 × 105 Pa (for 1 source), respectively. The first measurements were performed in 2001, but the experiment was executed more systematically between 2005 and 2018, covering a period of about 5 half-lives. The residuals from an exponential decay curve were of the order of 0.1% to 0.2% at 1 × 105 Pa, and 0.03% at 5 × 105 Pa and 8 × 105 Pa. The gain of stability with increased gas pressure was due to asymptotically reaching the maximum counting efficiency, resulting in lower sensitivity to pressure variations. The deduced half-life value of T1/2(55Fe) = 1006.70 (15) d or 2.7563 (4) a is more accurate than other data in literature, which are mutually discrepant. It is consistent with previous measurements at JRC with an X-ray defined solid angle counter.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Half-life Measurement of 55Fe

The half-life of 55Fe was determined experimentally and compared with literature values. A solid 55Fe source was prepared by electro-deposition and repeatedly measured in an X-ray detector at a constant, defined small solid angle. In total, about seven hundred measurements were performed over a period of ten months, corresponding to one third of a half-life. The results of 1004.5+-1.5 days is somewhat higher than most recommended values. The experimental method and corresponding uncertainty budget are presented.JRC.D.4-Isotope measurement

Preparation of high resolution 238U alpha-sources by electrodeposition from aqueous solution

The source preparation procedure for high-resolution 238U sources is described in this work. For preparing alpha sources for high-resolution spectrometry many parameters of the electrodeposition had to be optimised such as the type of electrolyte, material and shape of the platinum anode, material of the cathode (backing), surface quality of the cathode, deposited mass, rotation of the anode, current density and the deposition time. This work was done in collaboration between CIEMAT and IRMM within the frame of MetroFission project aiming at the determination of the alpha-emission probabilities of 238U. MetroFission aims to address the measurement challenges posed by 'Generation IV' designs, by testing temperature measurements and materials for suitability, and ensuring sufficient nuclear data and radiation measurement techniques are available.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Linearity check of an ionisation chamber through 99mTc half-life measurements

The half-life of 99mTc was measured at the JRC using the ionisation chamber 'IC1' (type Centronic IG12). The result, T1/2(99mTc) = 6.00660 (18) h, is in good agreement with literature data. One experiment was performed in IC1's default set-up with the ionisation current being integrated over an air capacitor and read out as a voltage increase over time. This ensured excellent linearity and precision throughout the dynamic range, but the maximum current was limited to 2 nA. In a second test, the current was directly read out with a Keithley 6517A electrometer. Applying correction factors for the automatic range switching of the electrometer, an acceptable linearity was demonstrated over a range of 12 half-life periods starting at 20 nA. Piecewise fitting of the decay curve over periods of 6 h yields the same 99mTc half-life value within 0.04 % (0.0025 h) standard deviation over an activity range spanning at least 10 half-life periods (3 orders of magnitude).JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Experimental Verification of the Half-life of 65Zn.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Seven Techniques for Activity Standardisation of 125I

An 125I solution was standardised for radioactivity by means of seven primary techniques, of which six gave consistent results. The basic equations of most of the methods were put forward in this work.JRC.D.4-Isotope measurement