Das Projekt "Behaviour of actinides and other radionuclides that are difficult to measure, in melting of steel" wird vom Umweltbundesamt gefördert und von Kraftwerk Union AG durchgeführt. Objective: various types of contaminated piping, valves, heat exchangers and vessels are removed from nuclear facilities in the course of decommissioning. Depending on their origin, these components are contaminated with various radio nuclides, e.g. alpha-emitters, pure beta-emitters, and gamma-emitters. Unrestricted or otherwise non-hazardous reuse of these components is possible if the residual activity concentrations are below the limits authorised. To achieve this goal, decontamination processes have to be used in general. In many cases, chemical decontamination of large components with complex surface geometry cannot be performed economically. Recycling can be achieved in many cases using melting processes. Thus the non-hazardous reuse of beta-, gamma-contaminated material which accumulated in the course of repairs and refittings of nuclear power plants has been demonstrated by the contractor in co-operation with Siempelkamp Giesserei GmbH und Co, Krefeld. The aim of this research programme is to extend the melt decontamination process to materials which are contaminated with actinides and radio nuclides that are difficult to measure. The distribution of these radio nuclides in the metal and the slag will be determined and direct measuring techniques or representative sampling techniques will be developed. General information: b.1. Literature review related to radio nuclide deposition on components, chemical separation procedures for iron and nickel, basic radio nuclide data and evaluation of authorised activity limits. B.2. Sampling of material and test melts at laboratory scale using well known activity quantities and accompanied by an appropriate measurement programme for original material, metal, slag and off-gas. B.3. Development of direct measuring techniques for alpha emitters in melt and slag, taking into account the alpha-energy of the emitting nuclides and the sample geometry. B.4. Development of measuring techniques for pure beta-emitters, such as c-14 and sr-90, expected to be found in metal and off-gas, and in slag, respectively. B.5. Development of a sampling technique and simple chemical separation procedures for nuclides decaying by electron capture, such as fe-55 and ni-59, emitting weak x-rays which cannot be measured directly. B.6. Large-scale melt in a commercial foundry of alpha-contaminated material to demonstrate the transferability of the laboratory results to industrial scale. B.7. Evaluation of results from both laboratory tests and large-scale tests with respect to alpha-activity distribution in metal, slag and off-gas, the most suitable measuring technique and costs. Achievements: the research work carried out confirmed the expected homogeneous distribution of the radio nuclides selected for the experiments (iron-55 and nickel-63) in the metal ingot, as was already known from the behaviour of cobalt-60. Cobalt-60 radio nuclide may be used as an indicator nuclide for iron-55 and nickel-63 which are both ...
Das Projekt "Messung der raeumlichen Verteilung von Schadstoffen auf Betonflaechen und der Akkumulation von Staeuben zur Verbesserung von Materialfreisetzungsszenarien" wird vom Umweltbundesamt gefördert und von Technischer Überwachungsverein Bayern Sachsen durchgeführt. Zielstellungen: The objective of the supplementary research work is the development of a high resolution in-situ gamma spectrometer with a collimied 'field of view'. For reasons of the collimied geometry and the expectable limited horizontal extension of contaminations, advanced calibration and analysis techniques must be developed to calculate the radioactive inventory of a deeply contaminated surface. On the one hand, the research builds up on the existing or just finished contracts (FI2D-0031, -0033, -0039, -0044 and -0055); on the other hand, it necessitates the knowledge acquired in, and active support of, these contracts for verification purposes. Allgemeine Informationen: At contaminated areas, conventional methods (eg taking samples, measuring the exposure rate) will be compared with the in-situ technique. The statistical significance of a collective of samples will be examined with the results of the 'full-scale' in-situ measurements. Some selected higher contaminated samples will be analyzed for difficult-to-measured pure beta emitters (eg Ni-63). The economical sensible minimum detection limits for important nuclides of the in-situ system will be determined and compared with the different national release criteria. Measurements and calculations with can improve the existing decontamination strategies in terms of reducing occupational doses or minimizing the volume of nuclear waste will be performed. These results will be used for recommendations for optimized decontamination strategies. The effects of the measurement results on radiological models and scenarios will be determined. The testing of the prototype of a collimied in-situ spectrometer and the various measurements on building structures will be carried out in facilities which are being decommissioned (such as Gundremmingen KRB-A, Brennilis EL4 or Marcoule G2/G3).