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NEUTRON DOSIMETRY INSTRUMENTATION FOR RADIATION PROTECTION AND RADIOBIOLOGY

Obiettivo

THIS PROPOSAL WILL PROVIDE MORE INFORMATION ON DOSIMETRY FOR THE PROTECTION OF WORKERS AND THE POPULATION. AREA MONITORING WILL BE IMPROVED.
In radiation protection dosimetry there is still a need for the development of sensitive detectors with a response proportional to dose equivalent for a wide range of radiation qualities. For the interpretation of biological results, obtained with various types of radiation, it is essential that dosimetry systems provide information on radiation quality in addition to accurate and precise dose values. The practical implementation of high pressure ionisation chambers for this purpose is being investigated. The experimental studies of the high pressure ionisation chamber system are mainly being performed under conditions relevant to radiation protection practice.

This research has produced the following conclusions.
To obtain a sensitive photon dosemeter, the aluminium high pressure chamber operated at 8 MPa of argon or 90 per cent argon + 10 per cent methane with relative neutron sensitivity values of 0.055 and 0.037 respectively, for d+T neutrons should be used.
The use of ethene which seemed promising on the basis of results for photons is not suitable to obtain a photon dosemeter.
The photon component of the 0.9 and 2.1 MeV mixed fields could be determined on the basis of the pressure dependence of the reading of both chambers filled with argon.
Conventional magnesium (or aluminium/argon ionisation chambers show various problems related to dependence of reading on gas flow rate, polarity effect, dependence of the reading on wall thickness and different relative neutron sensitivity values for different chambers of the same design.
The use of methane in the tissue equipment high pressure chamber appears to provide the most suitable detector among the investigated gas chamber combinations for total dose determination in neutron photon fields for neutron energies from 0.9 to 15 MeV. At 2 MPa, the relative readings are approximately 16, 23, 18 and 16 for 0.9 2.1 5.3 and 15 MeV neutrons, respectively.
Ion recombination in methane inside the tissue equipment high pressure chamber at elevated pressures seems most promising for assessment of radiation quality, although the pressure dependence of the reading can also be employed for this purpose. Extension of the measurements to lower and higher neutron energies are required to make a decision on the most practical method for a field instrument.
Calculations of cavity size effects, most likely on the basis of the NIST-code to be modified for large cavities, is of great interest for comparison with experimental results on the influence of cavity size as well as for analysis of ion recombination.
NEUTRON DOSIMETRY INSTRUMENTATION FOR RADIATION PROTECTION AND RADIOBIOLOGY.

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CSC - Cost-sharing contracts

Coordinatore

RADIOBIOLOGICAL INSTITUTE TNO
Contributo UE
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Indirizzo
DIVISION FOR HEALTH RESEARCH LANGE KLEIWEG, 151
2280 HV RIJSWIJK
Paesi Bassi

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