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Wipe test counter
A wipe test counter is a device used to measure for possible radioactive contamination in a variety of environments. When using radioactive liquids it is necessary, per NRC (Nuclear Regulatory Commission) requirements, to test for accidental contamination in all areas where liquid isotopes are used. Technicians use a swab or small absorbent smear to “wipe” an area. This “wipe” is then stuffed into a test tube and counted on a “wipe test counter”. The results are processed by the machine and a PASS or FAIL is determined.
In the past, wipes were counted with a GM tube based counter. Regulations in most states now require the counter to be capable of reading down to 200 DPM ( disintegrations per minute ) for open access areas. GM tubes simply cannot achieve the level of efficiency required.
A modern wipe test counter like the “Wiper” ( manufactured by (Laboratory Technologies, Inc. )) consists of an NaI(tl) crystal/photomultiplier tube detector, which outputs the counts to a MCA ( multi-channel analyzer ). If a contaminant was found software can then identify the isotope, and convert the counts to an accurate DPM. This requires a wipe test counter with a MCA with enough channels ( typically 1024 or more ) to accurately identify the spectral fingerprint of the isotope. Once the isotope is identified, the counts must be converted to DPM. This calculation requires knowing the conversion efficiency of the NaI(tl) from CPM ( counts per minute) to DPM.
Recently, multiple well counters specifically designed for wipe testing such as the “Multi-Wiper” ( manufactured by (Laboratory Technologies, Inc. )) have entered the market. Multi-well counters can count up to 10 wipes simultaneously and are specifically designed for nuclear medicine departments.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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