[en] A device was developed with an array of 8 silicon surface barrier detectors inside a vacuum chamber containing a rotating sample holder for large areas (200 mm diameter) aerosol filters. It serves for quick identification of α-emitters on these aerosol filters, and allows to measure the α-particles with a relatively constant efficiency along a filter diameter. Thus, the radiochemical treatment of single filters can be avoided. Troubles appeared in the course of development of defective semiconductors and their temperature dependence. To suppress the influence of temperature a cooling device was built. During practical testing a cross-efficiency of 13.6% was measured. It is possible to identify α-emitting nuclides with an activity of 10^-1 Bq per sample during about 2 hours of measuring time. Appropriate methodes of calculation are indicated. The data output of the device is suited for transfer to a computer. (orig./HP)

No abstract available

No abstract available

[en] ¹³¹I sampling in air is optimum if the activated charcoal volume is so high as to retain elementary ¹³¹I₂, although not too high so as to result in too low a counting efficiency of the Ge(Li) detector used in the measurement. The following sampling system is recommended as a result of optimization: A preceding aerosol filter serves to separate the ¹³¹I aerosols. This filter as well as two series connected 200 ml activated charcoal filters are flushed with 7.2 m³ of air per hour. The activated charcoal has been impregnated by TEDA. Gamma spectrometry of the activated charcoal of the first bed and of the absolute filter is carried out simultaneously within a 1,000 min measurement. Under most adverse conditions at least 95% of ¹³¹I are retained at the first filter (100% relative air humidity). This allows measurement of the concentration of ¹³¹I in air, which corresponds to half the value of the maximum permissible thyroid dose for infants. At least 50% of CH₃¹³I are retained. Since the radiotoxicity of CH₃¹³¹I is lower by at least the factor 100 than that of ¹³¹I₂ and ¹³¹I at the activated charcoal filter is evaluated as ¹³¹I₂, a dose calculation based on a retention of at least 50% means that one is on the safe side for each CH₃¹³¹I/¹³¹I₂ ratio. (orig.)

No abstract available

[en] The effects of tube pressure, furnace pressure and attachment forces acting on plain walls, walls with simple attachment plates or brackets, and corners with brackets have been studied using three-dimensional photoelastic models. In all configurations the tube axes were vertical. The simple horizontal attachment plates extended from crown to crown over three pitches and were integral with the tubewall; they were loaded by horizontal forces normal or parallel to the wall. The bracket attachments consisted of two horizontal plates or ribs integral with the tubewall and extending over five pitches, with the bracket itself fitting between these ribs and joined to them along the edges; the applied loads were horizontal or vertical forces at the bracket, and furnace pressure. Detailed surface stress distributions have been determined. The critical positions were found to be in the fillets at the fin-tube and plate-tube junctions. The application of the model results to the prediction of stresses in boiler walls is discussed

[en] At the Health Physics Division of the Karlsruhe Nuclear Research Center a NaI(Tl)-CsI(Tl) sandwich scintillation detector system was set in operation for monitoring of persons with regard to incorporation of transuranium nuclides. The report describes the calibration of the device, for which a makeshift lung and chest phantom as well as point sources were used. In addition several background measurements with and without persons have been carried out. Based on the results of these measurements the lower detection limit for ²³⁹Pu was found to be 6.5 nCi within a measuring time of 50 minutes. (orig.)

[en] The activity deposited per km² in the Karlsruhe region is comparable with the sum of aerosols released from all nuclear power plants in the Federal Republic of Germany. Results of measurements performed in 1986 on leaf and needle samples are compared to the corresponding results obtained in 1987. The behavior of cesium activity in trees is discussed. In addition the results of measurements made in 1987 on small vegetation, especially mushrooms, are indicated. The Cs-activity expected to be found in the meat of deer of the same region is estimated. (orig./HP)

[en] Major results derived from the measuring program are: The contaminations of soil and plants detected within the area of the Karlsruhe Nuclear Research Center are primarily attributable to nuclear weapons fallout. Other sources of contaminations by emitters of the Karlsruhe Nuclear Research Center were found to be the Central Decontamination Department, especially the zone close to the incineration facility. The tritium contamination of the soil resulting from the tritium content of the precipitations can be detected down to the ground water. On the basis of measuring results available for the distribution in terms of depth of the tritium concentration of the soil moisture an extrapolation gives estimated values for the vertical migration rate of tritiated water in the soil between 2 m/a and 4 m/a. The vertical migration rate of ₁₃₇Cs ranges from 0.4 cm/a to 1.6 cm/a. The radioactivity measured in the Hirschkanal cannot be explained solely as a result of fallout from nuclear weapons tests and from the discharges into the atmosphere by the Karlsruhe Nuclear Research Center. The tritium measurements in the water of precipitations yield a value for the proportionality constant s = ß/theta (ß = washout constant, theta = amount of precipitation) between 1x10^-₉ a/(mmxs) and 2x10^-₉ a/(mmxs). (orig./HP)

[en] A short description of the equipment now in use for lung counting at the Karlsruhe Nuclear Research Center is given. A new proportional lung counter has been developed for optimal efficiency with argon-methane as flushing gas, low background and an equal response over the window surface. Calibrations with a thorax phantom showed that if this proportional lung counter were used in conjunction with a pulse-shape discriminator, a lower detection limit for ²³⁹Pu could be achieved which is comparable to that of a commercial sandwich detector. (author)