The electronic personal dosimeter PTB DOS-2002

At the "Neutron Radiation" Department, the electronic dosemeter PTB DOS-2002 was completed, the most important principles were patented and five prototypes were supplied to the Bundesamt für Strahlenschutz which supported the project with third-party funds for a two-year period. The small, battery- operated dosemeter displays the personal dose for direct reading in mixed neutron and photon fields. The rated ranges of use of the energy are 25 meV to 15 MeV for neutron radiation and 70 keV to 7 MeV for photon radiation. For photon radiation, the lower detection limit lies at approx. 16 nSv, for neutron radiation at 10 µSv. The dosemeter contains only a semiconductor meter with a thin epitaxial layer for simultaneous determination of the neutron and photon dose. With the aid of optimized converting and absorbing layers of polyethylene, lithium fluoride and boric plastics, charged particles (electrons and ions) are generated by irradiation with photons and neutrons, which deposit energy in the depletion zone of the semiconductor
p-n transition. The personal dosemeter has proved its suitability for monitoring tasks in nuclear plants by the comparison measurements at the Gorleben transport container repository. The measurements were carried out on different types of CASTOR containers.

a) Pulse height spectra for irradiation with photons (coloured curves) and neutrons (squares) b) The electronic neutron/photon dosemeter PTB DOS-2002 c) Comparison measurements at the Gorleben transport container repository