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TRIATHLER OPERATING INSTRUCTIONS
Counting beta emitters i.e. P-32
Remove the black lid over the sample well by pressing down slightly and twisting anticlockwise.
Make sure that the purple lever on the front is directed to the left of the instrument. If it is on the right, depress it slightly and slide it to the left.
- You have been supplied with a boiling tube containing a pre-weighed amount of uranyl nitrate (approx. 0.25 g). Note exact weigh as written on the tube – you will need this for your calculations.
- Add 10 cm3 deionised H2O to the boiling tube
- Add 1 cm3 of 5% ferric chloride
- Add excess 1M ammonium carbonate (at least same total volume)
- Warm in the dry bath in the fume hood until the precipitate is a fairly thick, chocolate brown sludge (approx. 10 – 20 min)
- Slowly turn on vacuum pump connected to a Buchner funnel lined with 20 mm diameter filter paper
- Carefully pipette the liquid fraction onto the filter paper using a plastic Pasteur pipette and then pour the remaining precipitate onto the filter paper
- When reasonably dry, transfer the funnel to a clean boiling tube
- Redissolve the residue on the filter paper by carefully dripping 1M nitric acid onto it and allow to filter under gravity
- Add more 1M ammonium carbonate (approx. twice the volume of dissolved residue) to reprecipitate the ferric hydroxide and reheat in the dry bath
- Filter through a 2ndclean Buchner funnel using the vacuum pump
- Wash with 1-2 cm3ammonium carbonate and 1-2 cm3deionised water
- Make sure the filter paper is as dry as possible by continuing to draw air through it using the vacuum pump
- Transfer the dry filter paper to a metal planchette with forceps
- Use a tray to transfer the planchette to the wooden block beneath the infrared lamp in the fume hood and dry completely.DO NOT leave this unattended as it could catch fire.
- Using forceps carefully place the dried filter paper into a 20ml plastic scintillation vial and add 10ml of scintillation fluid
- Use theTriathler on the P-32 setting to count the cpm (see operating instructions below)
- Repeat counts 3 times and average. Estimate the errors due to counting (Poisson statistics)
- Remove the planchette from the Geiger counter and repeat counts for background (3 x 1 min)
- Correct for background counts, and by making any reasonable approximations necessary, such as counting efficiency being ~5%, calculate the 235Th activity of your sample
1. Turn on the Triathler by pressing the button at the back of the instrument.
2. The following display screens appear in succession:
Clear saved parameters
Triathler Version 1.7 (or 1.9)
Start sys edit
3. If the isotope previously selected was not P-32, press the P-32 button (3)
4. The following screen may appear if you re-select an isotope label:
5. The instrument will be ready to use when the screen displays the following:
<P-32>, t (time), S (sample number), R (cpm).
6. Place sample in the holder in the instrument – make sure the vial lid is secured.
7. Replace the black sample well lid by matching the small circle on the lid with the raised yellow spot on the Triathler. Press down slightly and twist clockwise.
8. Press the start button. The Triathler will automatically count for 60 sec (t). Note the number of counts next to the R in the display window.
9. Remove the lid. Remove 1st sample and place next sample in the holder. Replace the lid.
10. Press next button to obtain count