| Popis: |
This report focuses on detectors for the assessment of inhaled heavy radioactive elements. Currently, phoswich detectors are the most prevalent type of detectors in use for assessing lung depositions of heavy element low-energy photon emitters. These detectors, along with their associated instrumentation, have proven their reliability for routine monitoring. Most phoswich detector systems are capable of detecting about one-half lung burden of {sup 238}Pu or about one and one-fourth lung burdens of {sup 239}Pu on an average individual who has a uniform distribution of plutonium in the lungs. Most all the large area NaI detection arrays have been replaced by the phoswich detectors. The NaI detectors are similar in basic characteristic to the phoswich, however, the large area NaI detectors exhibit higher background and sensitivities at the lower energies (< 70 keV) used for assessing inhalation exposures of heavy elements. Some lung counter facilities use proportional counters for assessments. Those in current use have anti-coincidence chambers to reduce background counts and improve the sensitivity. Semiconductor detectors are only practical when used in arrays and, therefore, are the most expensive detection system available. |
