DD288732A7 - NEUTRON-personal dosimeter - Google Patents

Abstract

The invention relates to a personal dosimeter for measuring the caused by neutron radiation in the human body biological dose. The aim of the invention is to provide a robust and reliable dosimeter that can be evaluated in the simplest possible device under tactical conditions, the task being to measure the biological dose independently of the energy spectrum of the neutrons. The object is achieved by a combination dosimeter consisting of a detector which is sensitive only to gamma radiation and which is sensitive only to fast neutrons, the fluence sensitivity of the neutron-sensitive detector, defined as measurement signal per unit of neutron fluence, in the energy range of the neutrons of 0, 01 MeV to 15 MeV increases at least by a factor of 10 with the energy.

Description

Field of application of the invention

The invention relates to a personal dosimeter for measuring the caused by neutron radiation in the human body biological dose, which is a measure of acute somatic damage to the body.

The personal dosimeter is intended in particular for measuring that biological dose which is produced under tactical conditions by the neutrons of a nuclear weapon detonation in the human body.

The extended energy range of the neutron radiation of a nuclear weapon detonation, which is subject to strong changes depending on the type of nuclear weapon detonation, the distance to the nuclear weapon detonation and depending on material and thickness of any effective shielding, complicates the neutron dosimetry of nuclear weapon detonations.

When neutrons are applied to the human body, in addition to the direct damage to the tissue by the neutrons, the secondary gamma radiation resulting from neutron capture must also be taken into account, which likewise has a damaging effect on the body.

Characteristic of the known technical solutions

Various neutron dosimeters are known for the measurement of neutron person doses.

Thus, for example, in neutron failure dosimeters, activation detectors (resonant and / or threshold activation probes), solid-state track detectors (with and or without fission material converters), or core-tracking films are used.

As a major disadvantage of these dosimeters, the evaluation must be considered. Solid state track detectors are only after a chemical etching in hot liquor, films evaluated only after development. The evaluation represents a partly visual track count.

Another disadvantage of these detectors is c ^': i proportionality of their display for neutron fluence and not for biological dose. From the measuring effect of said detectors, the neutron fluence, using several different resonance and Schwellwertaktivierungstfetektoren the neutron spectrum is determined. From these data, the biological dose is calculated by multiplying or summing over different energy ranges by using suitable dose-fluonz factors. Incomplete knowledge of the neutron spectrum inevitably leads to errors in dose determination.

Also known as neutron dosimeters are special silicon diodes in which the change in the forward voltage is proportional to the neutron dose of fast neutrons.

A disadvantage of both silicon diodes and core-tracking films and solid-state track detectors is the fact that these detectors are sensitive only to fast neutrons.

Thermal and especially intermediate neutrons, which provide a significant contribution to the biological dose, are not registered by them, so that depending on the proportion z. B. intermediate neutrons on the neutron spectrum errors in the dose determination are the result.

Other neutron dosimeters exploit the fact that a number of substances have high thermal neutron cross sections, e.g. ⁶ Li, ¹⁰ B, Ag, rare earths, Cd. Using these materials, easily evaluable dosimeters, 7 B. thermoluminescence or Radiophotolumineszzzosozimeter can produce that have a high sensitivity for thermal N.

Since thermal neutrons are only partially present in the energy spectrum of the neutrons of a grain waffond tone onthalton and also only a neringon contribution to the biological dose in relation to fast Noutronon lioforn, oin for thermal neutrons t npfindliches dosimeter is only conditionally suitable for the tactical Dosimetrio. Somewhat improved is the applicability of this dosimntor by prevention as albedodoslmeters. An albedo dosimoter makes use of the scattering and, in particular, the moderating effect of the body of the dosimotor carrier, by means of which boi schnollon neutrons also produce a small proportion of thermal stray neutrons, which excite the albododosimeter. A disadvantage here too is a strong dependence of the measuring effect of the incident neutron Enorgiospektrum.

Object of the invention

OBJECT OF THE INVENTION It is to provide a robust and negligible personal eosmoter, which is evaluated in a simple and at the same time robust and reliable device. In addition, the requirement still exists for the smallest possible measuring error under the most diverse irradiation conditions.

Explanation of the essence of the invention The invention has for its object to provide a neutron personal dosemeter, which under field conditions

can be evaluated and the dio caused by the neutron radiation of a nuclear weapon detonation biological

Indicating dose independent of the energy spectrum of neutrons. The task is with a Porsonondosimeter for measuring dor caused by neutrons in the human body

biological dose, to obtain a low dependence of the sensitivity of the neutron energy for the measurement of the biological neutron dose in a wide range of energy, achieved in that the invention

Combination dosimeter worn on the body surface is made up of a substantially just for Gamma radiation sensitive and consists of a sensitive only for fast neutrons detector. The Fluenzempfindlichkoit the neutron sensitive detector, defined as a measurement signal per unit of neutron fluence must in Energy range of neutrons from 0.01 MeV to 15MeV increase at least by a factor of 10. In the evaluation of the

(Combination dosimeter is calculated from the measurement signals Μγ of the gamma-sensitive and M _{n of} the neutron-sensitive

Detector a proportional to the biological dose measured value M = ay · Μγ + a "· M _n determined, where av and a _n Are weight factors whose values are determined by calibration with neutrons of different energy. As a fast neutron sensitive detector, a silicon diode with a large base width is suitable in which the Neutron dose proportional change do ^r flux voltage is measured. As gamma sensitive detector is eino Semiconductor structure such. B. a MOS or MIS field effect transistor suitable whose Schwellspannungsänderung the Gammadosis is proportional. Both semiconductor structures can be used to form the combination dosimeter in one

common housing and / or be arranged on a common silicon block.

As a gamma-sensitive detector is also a thermoluminescent or Radiophotolumineszenz dosimeter geeignot that a

has low sensitivity to thermal neutrons by using only minimal amounts of ⁶ Li, ¹⁰ B, Cd, Ag or rare

Contains earth. To form the combination dosimeter, the thermoluminescent or radiophotoluminescence detector can be used

be arranged with a silicon diode with a large base width in a common housing.

To explain and describe the advantages of the solution according to the invention, the following facts are given: It has been found that the biological dose of neutrons in the energy domain of the thermal and intermediate neutrons

about 90% of the secondary γ-Einfangstrahlung caused in the interaction of the neutrons with the

Tissue of the human body arises. The secondary gamma capture radiation also occurs at the body surface and can

be registered there by a only γ-sensitive dosimeter. The biological dose of fast neutrons, on the other hand, is caused only to a small extent by the secondary gamma radiation. It must therefore be registered by a detector sensitive to fast neutrons. Research has shown that it is biological for a measurement. Dose, which should be carried out independently of the energy of the neutrons, necessary that the energy of the

Neutron sensitivity of the fast neutron detector is the same as that of neutron kerma in tissue. Furthermore, the investigations have shown that the measurement accuracy for the dosimetry of nuclear weapon detonation neutrons

is still sufficient, if the sensitivity of the detector for fast neutrons in the energy spectrum of 0.01 MeV to 15 MeVum a factor of 10 increases with energy.

By using a gamma-sensitive detector for registration of biological dose thermal and

Intermediate neutrons and a detector sensitive to fast neutrons for the registration of biological dose-fast neutrons, a good adaptation of the energy path of the detector sensitivity to the energy path of the biological dose is achieved, which is the prerequisite for one of the energy distribution of the neutrons independent

Dose determination and thus for low measurement errors. This is a significant advantage of the combination dosimeter according to the invention over others for the invention Neutron dosimetry used detectors. An optimal adaptation of the energy courses of the gamma sensitive and the neutron sensitive detector to the

biological dose can be achieved by appropriate choice of the weight factors a _n and βγ, which can be carried out for each of the possible combinations by measuring at different neutron energies.

The use of two detectors in the neutron dosimeter according to the invention also has the advantage that in principle

the separate consideration of the different for the secondary γ radiation on the one hand and for fast neutrons on the other hand biological fading is possible.

Another advantage of the solution according to the invention is the possibility of combining the dosimeter also for determining the

total biological dose of neutrons and gamma radiation of mixed fields, e.g. the instantaneous nuclear radiation of

Nuclear weapon detonations to use. Door this case is from the gamma sensitive part of the combination dosimeter

in addition to claiming that its gamma dose sensitivity must be independent of quantum energy.

embodiment

A particularly favorable embodiment of the compact dslmeter is a silicon diode with large basbres in conjunction with a MOS or MIS field-effect transistor. Both semiconductor structures can be arranged on a common silicon block if desired. This embodiment is particularly suitable because of the simple evaluation method that exists for both detectors in a simple voltage measurement. The advantage here is the ability to realize the weighting factors of the measured values by suitable choice of Spannungsmeßbereiches or by goeigneto voltage divider in Ausweitegerät, so that the display dos evaluator can be calibrated directly in units of biological dose.

In another embodiment, a large baseband silicon diode is combined as a fast neutron detector with a thermoluminescent or radioluminescent detector as a gamma detector. Beido detectors are housed in a common housing, which is provided with suitable means to bring it with the evaluation device in the necessary optical and electrical contact.

Claims (3)

1. Personal dosimeter for the measurement of neutron induced in the human body biological dose to obtain a low dependence of the sensitivity of the neutron energy for the measurement of the biological neutron dose in the energy range of slow, intermediate and fast neutrons, characterized in that a Kombinationsdosimetor is used consists of a detector substantially only sensitive to gamma radiation for the registration of the biological dose of thermal and intermediate neutrons and of a detector which is essentially only sensitive to fast neutrons for the registration of the biological dose of fast neutrons, the fluence sensitivity being defined for the detector of fast neutrons as a measuring signal per unit of neutron fluence, in the energy range of neutrons from 10keV to 15MeV at least by a factor of 10 increases. 2. personal dosimeter according to item 1, characterized in that as a detector for fast neutrons, a silicon diode with a large base thickness and a gamma detector, a MOS or MIS field effect transistor is used and that both detectors housed in a common Dosimeterkassette and / or are arranged on a common silicon block. 3. personal dosimeter according to item 1, characterized in that is used as a detector for fast neutrons, a silicon diode with a high base thickness and as a gamma detector, a thermoluminescence detector with low sensitivity for thermal neutrons.