A multicomponent dosimeter has been developed that uses an albedo detector to provide the measurement of low energy neutrons and as a screening element. It also contains track detector components, CR-39 and polycarbonate, which are only processed if the TLD indicates there has been an exposure to neutrons. Since the three components have significantly different energy responses, the dosimeter can act as a crude spectrometer. This report describes the dosimeter and briefly summarizes its use experience. 10 refs., 2 figs., 2 tabs.
Background The objective of this study was to compare differences in cost estimates for paediatric HIV hospital service provision based on hospital prices with cost estimates obtained through a research-based service-specific costing exercise. Methods Activity data on the use of hospital services of children by stage of HIV infection were collected from casenotes for 118 HIV antibody positive children, managed at St Mary's Hospital NHS Trust, London, 1 January 1986-31 December 1994. Hospital unit prices were obtained from the Hospital Trust Finance Department; unit cost estimates were obtained from relevant hospital departments through a research-based service-specific costing exercise. Financial data related to the 1993-1994 financial year, and were indexed to 1995-1996 prices. The main outcome measures were cost estimates per patient-year by stage of HIV infection. Three cost scenarios were calculated: first by linking activity data with hospital prices (Trust Prices); second by linking activity data with routinely available hospital prices plus units costs from the costing exercise where no relevant hospital prices existed (Supplemented Trust Prices); third, by linking activity data exclusively with unit costs from the hospital-specific costing exercise (Unit Costs). Results There were substantial differences between unit cost estimates per patient-year based on Trust Prices and Supplemented Trust Prices compared with those based on Unit Costs. Differences increased with more intense use of services. The deficit based on Trust Prices compared with Unit Costs ranged from £432 per patient-year for HIV negative children, £574 for asymptomatic HIV-infected children, £288 for indeterminate children, £1814 for children with symptomatic non-AIDS to £7418 per patient-year for children with AIDS. Conclusions In this hospital, reliance on generic hospital prices to derive cost estimates for paediatric HIV services produced considerable underestimates of the cost of service provision compared with data derived through the costing exercise. If this occurs across all or most areas of service provision, this can lead to substantial financial deficits, which in turn may mean that the needs of specific client populations may not be met.
CR39 proton sensitive track detectors were greeted by the radiation protection community at the end of the last decade as a major breakthrough for personnel neutron dosimetry. A number of laboratories eagerly began research on application of CR39 to their dosimetry needs. However, in the last two or three years the enthusiasm has subsided, and many health physicists have stopped working with the material. The number of participants using CR39 in the Oak Ridge National Laboratory Personnel Intercomparison Studies dropped from six in 1985 to three in 1986. On a national level, the Federal Republic of Germany with researchers active in CR39 research recently adopted an albedo system as their national standard. In contrast, the United States Department of Energy (DOE) is supporting development of a CR39 based combination dosimeter to meet Department wide dosimetry needs. The English National Radiological Protection Board (NRPB) now features the use of CR39 in the NRPB PADC(CR39). There has obviously been a range of experiences with CR39 in the dosimetry community. Why has this been the case, and what is the proper role for CR39 in personnel neutron dosimetry. 12 refs., 2 figs., 1 tab.
Cosmic ray neutron flux densities, neutron dose equivalent rates, and exposure rates for ionizing radiation were measured in a series of flights at 12.5 km (41,000 ft) in an Ames Research Center high-altitude aircraft. Instrumentation and analysis techniques were used which had been developed to measure accelerator-produced radiation. Neutron instrumentation consisted of Bonner spheres, threshold detectors, a moderated BF, counter, and a liquid scintillation spectrometer. A dose-equivalent meter from Brookhaven National Laboratory and an argon-filled ionization chamber were also flown. On three flights at average geomagnetic latitudes of 45, 38, and 48°N the neutron dose equivalent rates were 0.20, 0.14, and 0.22 mrem/hr. The corresponding exposure rates from the ionizing component were 0.37, 0.31, and 0.41 mR/hr. As measured by the liquid scintillation counter, the dose equivalent from 3- to 13-MeV neutrons is 30% of the total for all neutrons. The flux measured in this energy range agrees with the calculated values of Armstrong (Ar73). At a geomagnetic latitude of 43°N, a plot of the exposure rate against the pressure altitude yielded a relaxation length of 140 g/cm2. Simultaneous measurements of the neutron and ionizing components verified that the former is more sensitive to changes in geomagnetic latitude. A neutron spectrum derived from Bonner sphere measurements indicates that the flux densities in the Hess spectrum may be two or three times too high and that the evaporation bump at 1 MeV may not exist.
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