[en] The secure storage and keeping of radioactive materials is increasingly important especially in times of a growing threat by terrorists. Authorities and users are jointly recommended to adapt the storage and keeping of radioactive materials to increasing security requirements. Here the different possibilities to fulfil the requirements regarding fire prevention and theft prevention which in Germany are set by DIN 25422 were determined for the radioactive materials and their storage and keeping places present in a research institute. The required measures were than agreed about with the relevant authority. Difficulties which are occurring due to the demanding combination of requirements out of the areas of radiation protection, fire prevention, and theft prevention are discussed. The storage and keeping of radioactive materials especially such of high activity requires a high level of security which must be continuously adapted to rising requirements.

[en] For the search and detection of concealed nuclear material and neutron sources we have equipped a conventional car with a neutron measurement system. It consists of six neutron slab counters on each side. Each slab counter has a size of approx. 25x50x9 cm³ and contains 6 He-3 tubes embedded in polyethylene covered by stainless steel. The active length of the tubes is 33 cm and the diameter 2.54 cm. The efficiency of all six slab counters on each side is 0.66 % for the detection of Cf-252 fission neutrons emitted from a point source in a distance of 100 cm from the center of the detectors. The complete system is mounted in a square steel rod assembly so that it can be fixed in most vehicles easily. Between the racks for the detectors we have fastened a voltage converter and the electronics. A view of this system installed into a car is shown. The pulses of the six modules on each side are summed passively and each side is analyzed separately. The results can be displayed on a handheld PC in the front of the car or in case of a covered search the data can be stored in a non-volatile memory in the electronics. For a clear location these data will be synchronized with a GPS signal. A measurement performed with a car equipped with this neutron detection system is shown. We placed a small neutron source (Cf-252) two meters away from the driving way of the car. The neutron intensity corresponds to less than 10 g reactor plutonium with a burn up of 30 GWd/t. The results show a very clear signal on the right side whereas the signal from the left row of the detector modules is only slightly above background. In addition we have performed measurements in practical operation. The typical neutron background was 10 cps on the test site. A neutron source (Cf-252) was hidden inside a house in the ground floor approx. I m above the floor. The neutron intensity of this source was 1.86 10⁵ n/s (in 4π). This corresponds to about 530 g reactor plutonium (burn up of 30 GWd/t) or even less for higher burn up. In case of weapon grade plutonium this neutron intensity corresponds to a quantity of 3.5 kg. When driving slowly (velocity approx. 10 km/h) past the house in a distance of about 5 m a significant rise in count rate of up to 130 cps was monitored in the module row faced toward the house. Passing on the street in a distance of 10 m still a rise in count rate was monitored for velocities up to 10 km/h: we measured 25 - 30 cps. For strong sources neutron coincidences may be measured in addition. If coincidences are recorded this is a clear evidence for fissionable material. The measurements show that such fissionable material can be detected clearly and easily from a car. This system may be used to discover illicit trafficking of nuclear material and to prohibit nuclear proliferation

No abstract available

[en] For the search and detection of concealed nuclear material and neutron sources a conventional car with a neutron measurement system was equipped. It consists of six neutron slab counters on each side. Each slab counter has a size of approx. 25x50x9 cm³ and contains 6 He-3 tubes embedded in polyethylene covered by stainless steel. The active length of the tubes is 33 cm and the diameter 2.54 cm. The efficiency of all six slab counters on each side is 0.66 % for the detection of Cf-252 fission neutrons emitted from a point source in a distance of 100 cm from the center of the detectors. The complete system is mounted in a square steel rod assembly so that it can be fixed in most vehicles easily. Between the racks for the detectors we have fastened a voltage converter and the electronics. The pulses of the six modules on each side are summed passively and each side is analyzed separately. The results can be displayed on a handheld PC in the front of the car or in case of a covered search the data can be stored in a non-volatile memory in the electronics. For a clear location these data will be synchronized with a GPS signal. A measurement performed with a car equipped with this neutron detection system is shown. A small neutron source (Cf-252) was placed two meters away from the driving way of the car. The neutron intensity corresponds to less than 10 g reactor plutonium with a burnup of 30 GWd/t. The results show a very clear signal on the right side whereas the signal from the left row of the detector modules is only slightly above background. In addition measurements were performed in practical operation. The typical neutron background was 10 cps on the test site. A neutron source (Cf-252) was hidden inside a house in the ground floor approx. 1 m above the floor. The neutron intensity of this source was 1.86 10⁵ n/s (in 4π). This corresponds to about 530 g reactor plutonium (burn up of 30 GWd/t) or even less for higher burn up. In case of weapon grade plutonium this neutron intensity corresponds to a quantity of 3.5 kg. When driving slowly (velocity approx. 10 km/h) past the house in a distance of about 5 m a significant rise in count rate of up to 130 cps was monitored in the module row faced toward the house. Passing on the street in a distance of 10 m still a rise in count rate was monitored for velocities up to 10 km/h: we measured 25-30 cps. For strong sources neutron coincidences may be measured in addition. If coincidences are recorded this is a clear evidence for fissionable material. The measurements show that such fissionable material can be detected clearly and easily from a car. This system may be used to discover illicit trafficking of nuclear material and to prohibit nuclear proliferation

No abstract available

[en] To combat illicit use of nuclear and radioactive material and to take preventive action reliable measurement techniques are imperative for early detection of this material. Nuclear safeguards are an important tool to impede the illicit use of fissionable material. But only nuclear material is controlled by safeguards, radioisotope sources are not covered by the safeguards regime in general. Whereas in most western countries comprehensive regulations for the control of radioactive materials exist a lot of other countries have inadequate control and monitoring programs to prevent or even detect the theft of these materials. While radiation accidents caused by orphan sources may give an idea on the extent of such a risk, the injury caused by a well planed terrorist attack with radioactive or nuclear material may be even worse. Since the threat environment is very unpredictable mobile measuring systems are essential to detect and respond to malicious acts involving radioactive or nuclear material. For the detection and identification of radioactive and nuclear material Fraunhofer INT has built up a mobile measuring system integrated into a transportable container. A power generator on a trailer makes the system independent of local resources of electric power. This container as well as the power generator can be transported by land, air or sea. The system is equipped with various types of detectors for neutron and gamma radiation, some of the detectors are similar to those used in safeguards. The type of radiation and its activity level can be determined. In case of neutron emitting material it is possible to distinguish fissionable material from random neutron sources by means of coincidence counting. This system is completed by a measurement car, which is equipped with high efficient neutron detectors and a background subtracting gamma measurement system. With this system hidden radioactive material can also be revealed by a covered search. In case of a radiological dispersal device or an improvised nuclear device the danger zone may extend to several hundred meters. In this case the detectors and electronics are moved with a remote controlled manipulator vehicle near the suspicious object. The measured data are transferred via radio transmission to the container placed in a safe distance for evaluation and risk assessment. Depending on availability of telecommunication infrastructure, the measurement results can be communicated by telephone line, mobile phone or satellite. Based on the results the next action steps are decided by law enforcement authorities. The capabilities of these mobile detection systems have been demonstrated in field exercises. Details of on-site identification measurements and results will be presented

[en] Published in summary form only

[en] In case of a terrorist's threat to release nuclear or radioactive material methods and procedures are needed for fast search and, after detection, identification of the substance. For searching the German Fraunhofer-INT in Euskirchen has a car at its disposal, which is equipped with very sensitive detectors suitable for a first identification of the material. Advanced measurements are performed with portable detectors of high energy resolution or by scanning of buildings or objects with a gamma camera. Initially such material may be stored under water in preparation for an attack. In this case we have a special sensor available for detection and subsequent identification. In case of no suspicious material being detected with all these passive methods, even though a well-founded suspicion exists, active methods will be employed. Therefore neutron interrogation is briefly presented. With all these techniques it is possible to determine the presence of radioactive or fissionable materials, as well as, within certain limits, type and quantity of material. Hence information will be gained on the possible risk potential and, by actions taking radiological aspects into account, recommendations can be given on further actions to be taken. (orig.)

[en] Fraunhofer-INT is going to equip a transportable container with a system for the detection, identification and characterization of radioactive material inside objects with unknown content. This system will be a prototype for a mobile system to detect illicit trafficking of radioactive and especially nuclear material and will thus prohibit nuclear proliferation. This container will be equipped with systems for passive and active nondestructive measurements. For active measurements we use a sealed tube 14 MeV neutron generator with an without a moderating assembly between the interrogating neutron source and the object of interest. Because stolen or diverted radioactive material generally may not have a fixed geometry and will not be packaged in standard containers the main emphasis in this paper is on in-situ gamma measurements taking into account possible shielding around the radioactive source. High-resolution gamma measurements were performed on radioactive material behind different types of shielding. The measured data were evaluated by modeling the different parameters like the wall thickness of the box, matrix and shielding material inside and so on. Comparison with the actual experimental setup of the models showed good agreement and proved the power of this method. In this way significant information was gained on the content of the unknown box, which is important for further actions. (author)

[en] The VENUS facility is a zero-power research reactor mainly devoted to studies on LWR fuels. Localised high-neutron rates were found around the reactor, with a neutron/gamma dose equivalent rate ratio as high as three. Therefore, a study of the neutron dosimetry around the reactor was started some years ago. During this study, several methods of neutron spectroscopy were employed and a study of individual and ambient dosemeters was performed. A first spectrometric measurement was done with the IPSN multisphere spectrometer in three positions around the reactor. Secondly, the ROSPEC spectrometer from the Fraunhofer Institut was used. The spectra were also measured with the bubble interactive neutron spectrometer. These measurements were compared with a numerical simulation of the neutron field made with the code TRIPOLI-3. Dosimetric measurements were made with three types of personal neutron dosemeters: an albedo type, a track etch detector and a bubble detector