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.
