Wipe tests are to be performed bi-monthly in general radiation laboratories, three-monthly in counting rooms and more frequently wherever risks may be higher.
Send the results of your tests to the Radiation and Safety Officer.
- Label counting vials with wipe test location (for example, 1 to 10).
- Wipe tests of bench and sink areas should be conducted over an area of 100cm2. (Wipe a square area of bench of sides measuring 10cm x 10cm. It will not be possible to wipe an area of 100cm2 when wipe-testing uneven surfaces such as telephones, centrifuge knobs or heat sealers.)
- Use an alcohol swab, moistened glass fibre filter disk or similar material.
- Wiping of bench and sink areas is done as a series of wipes evenly covering the area once. When wiping uneven surfaces, ensure that the surface is wiped once only, that is:
- The wipe can be transferred to the appropriate labelled press-seal bag or counting vial.
- If only beta-emitting radioisotopes (such as 3H, 14C, 35S, 32P or 33P) are used in the laboratory, then beta counting will be required on a liquid scintillation counter.
- If a combination of beta- and gamma-emitting radioisotopes are used in the laboratory, then gamma followed by beta counting will be required.
- Transfer wipe into labelled counting tube. For gamma counting, close the tube and place in gamma counter ready for counting. For beta counting, add liquid scintillant and place in the beta counter for counting. Take care not to place fingers around the side wall of each vial – hold the vial by the rim when adding scintillant, and use a tissue to hold vial when secruing the lid. Shake by holding the lid and base of the vial.
- Set the appropriate counting parameter settings for the counter.
- Beta counting can be followed by gamma counting for the same wipe test if there is suspected to be a mixture of gamma and beta radioisotopes present.
- Count samples for five minutes each and then obtain a printout of results. Transfer results to the "Wipe Test Results" book in the Radiation Manual.
- Rewipe test any areas that have a DPM value in excess of two times background, and enter results into the "Wipe Test Results" book.
- Send results to your School Radiation Safety Officer so that they may be forwarded to Jonathon Thwaites (+61 8 6488 7932) in the Safety and Health Office.
Monthly reporting sheet