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The exercise will consist of two main parts:
1. Thermal INAA of total chlorine in organic solutions using HPGe gamma spectroscopy.
- Lectures/demonstrations in the 4 application areas radio-pharmacy, radio-ecology, radioactive waste management and reactor operations.
- The students are divided first into two groups. Each group follows the procedure below.
- The NAA laboratory is inside a barrier. Accordingly, students have to observe and adapt the following procedure:
- All participants have to bring personal dose-meters and a lab-coat.
2. Put on lab-coat and dose-meter on the outside of the barrier.
3. Put on shoe cover (plastic) according to the demonstrations of the laboratory assistant and enter into the “hot” side of the barrier. Bring a minimum of papers into the laboratory.
4. The NAA laboratory facility, which originally consists of 3 wet-chemistry labs and 2 instrument labs, has temporarily only available 1 wet-chemistry lab and 1 instrument lab. All sample preparation, including sample transfer to and from the reactor, is performed in the chemistry lab. As soon as the sample is irradiated, prepared and ready for detection, it is transferred to the instrument, or counting lab.
5. Detection will be carried out with an HpGe detector coupled to common nuclear electronics and a PC-operated MCA based on the Maestro-program from Ortec.
6. It is important that the students strictly follow the instructions from the lab.-assistant(s) and not operate on “their own”.
7. When the practical tasks in the laboratory is finished, it is time to leave the NAA-laboratory. Collect your belongings and follow the procedure:
- Go to the wardrobe with the barrier
- Check your hands and lab-coat for contamination with a contamination monitor.
- Take off the lab-coat and place it in a designed plastic bag.
- Wash your hands
- Remove the shoe plastic cover according to demonstration by the lab-assistant.
- Enter the non-radioactive side of the barrier.
- Carry out all calculations in the assigned conference room.
Determination of Total Cl in Organic Liquids
Natural Cl has the two stable isotopes 35
Cl(35%) and 37
Cl(65%). Thermal neutrons induce the two reactions 35
Cl (T1/2 =3•105
) and 37
= 37.3 min). Only the second reaction is useful here. The actual gamma energies for 38
Cl are 1642.7 keV and 2167.6 keV.
The detailed procedure is:
- Team 1 and Team 2 go to the detector room where a teacher will demonstrate the counting equipment. These teams will then be well prepared for the counting procedure after the following practical procedure.
- Team 3 and Team 4 go to the preparation laboratory and carry out the following procedure:
- Prepare a Cl-standard: Dry KCl in a heating cabinet at 110 oC for 24 h. Cool in a desiccator. Weigh exactly in ca. 0.21 g KCl and dissolve to 100.00 ml in a measuring flask with distilled water. This standard is approximately 1000 ppm.
- For the present analysis we will operate with a working standard of about 100 ppm. Take an aliquot of 10 ml from the standard and dilute to 100 ml with distilled water.
- Prepare 4 plastic irradiation ampoules by heat-sealing adequate lengths of a plastic (polyethylene) tubing in one end.
- To one ampoule transfer a fraction of 1.00 mL from the working standard. Heat-seal and label.
- To the three others transfer 3 parallels of 1.00 mL of the organic unknown sample. Heat-seal and label.
- Pack the ampoules into a rabbit container.
- Arrange irradiation with the reactor control room.
- Irradiate the sample 5 min and transfer back to the lab.
- After irradiation wash the ampoules on the outside with the washing solution sequence acetone-water-acid mixture-water-acetone. Every ampoule is washed for 5-10 s in each solution.
- Samples are transferred to the counting laboratory and a demonstration is given of the counting equipment for teams 3 and 4.
- Position the first sample in front of the detector inside the lead shield and start counting. Start the stop-clock. Counting time 5-10 min.
- Count the two other samples and the standard in the end.
- Integrate the appropriate peaks and note the results.