[en] Usually, quantal conditional expectations are introduced by the requirement of some algebraic and analytic properties known to hold in the classical theory. The resulting objects do not depend on a given state which is in contrast to the classical theory. Hence, the question arises whether these objects are the most appropriate analogues of the classical ones. - We proposed an alternative setting by going back to two more fundamental axioms for classical conditional expectations, transducing them into the language of operational approach to quantum theory and proposing generalized conditional expectations which seem to be closer analogues to the classical ones (H. Cycon, K.-E. Hellwig (1977)). In the present contribution a Hilbert space formulation is given and further results on the formulation of quantum stochastic processes based on generalized conditional expectations are presented. In particular, sufficient conditions on a one-parameter family of self adjoint operators such that a Chapman-Kolmogorov equation holds true are derived. (orig.)

[en] The reduction of oxides of non-noble metals Me with highly purified hydrogen in the presence of noble metals E (E = Pt, Pd, Ir, Rh) - the so-called coupled reduction - results in many cases in the formation of intermetallic compounds EMesub(x). It is shown how, by means of emf-measurements on solid-state galvanic cells, the course of the coupled reduction can be followed and subsequently the data employed to determine thermodynamic values for the system EMesub(x). A suitable experimental arrangement has been developed with which thermodynamic investigations on the systems yttrium-platinum and neptunium-platinum have been performed. From the behaviour of the standard molar free enthalpy of the dissolution of yttrium or neptunium in PtMesub(x) (Me = Y, Np) with changing temperature T and composition x the standard molar free enthalpy of formation of the following alloy phases were calculated: Pt₅Y (1100-1600 K), Pt₃Y (1300-1700 K), Pt₅Np (1100-1600 K) and Pt₃Np (1100-1600 K). (orig.)

[en] Synchrotron X-ray diffraction (XRD) during the atmospheric oxidation of epitaxial Nb(1 1 0) films at elevated temperature reveals the formation of highly ordered oxygen phases within the Nb lattice. The oxygen is stored on interstitial lattice sites without destroying the basic BCC structure of the Nb host lattice. However the lattice exhibits an out-of-plane lattice expansion of up to 4.3%. During oxidation we observe the formation of a non-ordered lattice gas phase succeeded by a well-defined sequence of oxygen superstructures until finally the whole film is consumed by the formation of amorphous Nb₂O₅. We show that XRD is an excellent tool to monitor the exact evolution of the different oxygen phases. In addition we demonstrate that UHV post-annealing of partially oxidized films can be used to rearrange the oxygen within the sample while keeping the overall amount of oxygen constant

[en] The Double Chooz experiment is a reactor antineutrino disappearance experiment located in Chooz, France. It was designed to measure the neutrino mixing angle θ${}_{13}$. The experiment is composed of two liquid scintillator detectors of almost identical design that were able to identify electron antineutrinos from the two Chooz B reactor cores by the unique signal of the inverse beta decay. The far detector at an average baseline of 1050 m from the two reactor cores was in operation from April 2011 to the beginning of 2018. The near detector at an average baseline of 400 m has been operating from the beginning of 2015 to the beginning of 2018. A neutrino oscillation analysis can be setup independently from any theoretical model of the reactor neutrino flux utilizing the different baselines of near and far detector relying only on the comparison of near and far detector data. In doing so, all correlated systematics cancel and the analysis is protected against potential bias due to a mismatch of reactor neutrino prediction and data. Apart from its original design goal to measure θ${}_{13}$, Double Chooz is sensitive to so called light sterile neutrinos. Sterile neutrinos are neutrino states that do not take part in the weak interaction but may lead to additional disappearance of the known neutrino states, if they mix with the latter. That mixing is described by additional neutrino squared mass differences and mixing angles. The 3+1 model assumes one additional sterile state. Here, Double Chooz is sensitive to the new mixing angle θ${}_{14}$ depending on the new squared mass difference Δm${}_{41}^2$ if it is in the range of 0.003 eV${}^2$ ≲ Δm${}_{41}^2$ ≲ 0.3 eV${}^2$. This work presents the analysis of Double Chooz data with respect to sterile neutrinos. A Poissonian likelihood fit approach not relying on reactor model predictions is used. It is found that the Double Chooz data is with a p-value of 24.7% ± 2.2% consistent with the no-sterile (i.e. θ${}_{14}$=0) hypothesis. The upper limit on sin${}^2$2θ${}_{14}$ at 95% confidence level is given as a function of Δm${}_{41}^2$.

[en] In a new type of fuel, called Inert Matrix Fuel (IMF), plutonium is embedded in a U-free matrix. This offers advantages for more efficient plutonium consumption, higher proliferation resistance, and for inert behaviour later in a waste repository. In the fuel type investigated at PSI, plutonium is dissolved in yttrium-stabilized zirconium oxide (YSZ), a highly radiation-resistant cubic phase, with addition of erbium as burnable poison for reactivity control. A first irradiation experiment of YSZ-based IMF is ongoing in the OECD Material Test Reactor in Halden (HBWR), together with MOX fuel (Rig IFA-651.1). The experiment is described herein and results are presented of the first 120 days of irradiation with an average assembly burnup of 47 kWd/cm³. The results are compared with neutronic calculations performed before the experiment, and are used to model the fuel behaviour with the PSI-modified TRANSURANUS code. The measured fuel temperatures are within the expected range. An unexpectedly strong densification of the IMF during the first irradiation cycle does not alter the fuel temperatures. An explanation for this behaviour is proposed. The irradiation at higher linear heat rates during forthcoming cycles will deliver information about the fission gas release behaviour of the IMF. (author)

[en] Yttria-stabilised zirconia doped with erbia and plutonia has been selected as inert matrix fuel (IMF) at PSI, Switzerland. The results of experimental irradiation experiments on yttria-stabilised zirconia doped with erbia and thoria samples utilising accelerators, tests with yttria-stabilised zirconia doped with plutonia and erbia or urania pellets within research reactors, and a study of natural zirconia contacted to actinide rich rock are evaluated and compared. The results obtained for zirconia implantation with xenon as a representative fission product are analysed in term of swelling and inertness of the material. The reactor tests preformed in the material test Boiling Water Reactor, Halden and in the High Flux Reactor, Petten are also described, with emphasis on the IMF properties under in-pile irradiation. The natural analogue study of baddeleyite from Jacupiranga, southern Brazil, provides additional information. Baddeleyite crystals enclosed within uranpyrochlore grains and received intense irradiation, which did not affect either the structural integrity or the durability of the mineral. The results of these case studies, with accelerator, use in-pile and contacted with natural radioactive sources, provide useful information on the outstanding of the behaviour of zirconia under irradiation

[en] Double Chooz is a reactor antineutrino disappearance experiment located in Chooz, France. A far detector at a distance of about 1 km from reactor cores is operating since 2011; a near detector of identical design at a distance of about 400 m is operating since begin 2015. Beyond the precise measurement of θ ₁₃, Double Chooz has a strong sensitivity to so called light sterile neutrinos. Sterile neutrinos are neutrino mass states not taking part in weak interactions, but may mix with known neutrino states. In this paper, we present an analysis method to search for sterile neutrinos and the expected sensitivity with the baselines of our detectors. (paper)

[en] In 1986, twelve segments containing sphere-pac UO₂ fuel and eight segments containing UO₂ pellets were loaded in the Swiss Goesgen PWR (KKG) for a comparative irradiation test. The segments were mounted in four equivalent full-length KKG fuel rods. One rod was to be withdrawn at each annual shutdown for post irradiation examination in the PSI hot cells. The irradiation has been successfully completed in 1991. Post irradiation examination revealed that the fission gas release after the first cycle and the segment length change are comparable for pellet and sphere-pac segments while the diameter decrease is more pronounced for the pellet segments than for the sphere-pac segments. One sphere-pac segment and one pellet segment, base irradiated during one cycle, were sent to Halden and an instrumented ramp test in the Halden Boiling Water Reactor (HBWR) was performed in 1994/95. After the ramp test, the two segments were investigated at IFE (Kjeller) non-destructivety and destructively (visual inspection, dimensional measurements and fission gas release analysis for both rods, axial γ-scanning, neutronradiography and ceramography for the sphere-pac segment only). Micro-probe analysis and modelling was performed at PSI. Results are presented in the paper (author) (ml)

[en] Gastight utility plugs for the shielding walls of hot cells are mainly used for the passage of mechanical actuating mechanisms, for electric cables, for the passage of liquid and gaseous media and for purposes of visual inspection. The plugs are normally inserted in steel or brass casings. The design requirements for such plugs are: (a) safe prevention of the contamination of the operating room located in front of the Hot Cell: (b) mutual replaceability of plugs (for example, a mechanical plug must be capable of replacement by an electric plug); (c) the radiation shield of the utility plugs must be equivalent to an 85 cm or 110 cm thick baryte concrete wall having a density of 3.5 t/m³; (d) excellent gastight properties are required in order to ensure that the vacuum underpressure of 10-15 mm H20 inside the Hot Cell cannot entrain air from the outside. A design solution which meets these requirements for a mechanical utility plug is described. (author)

[en] The FUJI project is especially dedicated to the early-in-life restructuring of two types of particle fuel 3/4 sphere-pac and vipac 3/4 in comparison to pellet fuel. Three types of sphere-pac fuel segments prepared by PSI will be irradiated in the High Flux Reactor (HFR) in Petten (NL), together with pellet-type fuel segments and vipac fuel segments (non-spherical, fuel-shard-packed segments), prepared in accordance with JNC specifications at PSI under the same irradiation conditions. MOX fuel, with 20% Pu and an oxygen-to-metal ratio of 1.97 (typical for fast reactor fuel), is currently being produced in different fuel shapes (pellets, microspheres and vipac particles). For the pellet and vipac fuel, the dry attrition mill method was used to prepare the MOX powder prior to pressing. Microspheres were produced following the internal gelation process, with nitrate solutions as the starting material. The pellet and the vipac fabrication have now been completed, although some analysis results are still missing. The special production route of vipac has led to particles of beneficial shape; the microsphere fabrication is underway. The preparation for the filling and welding of the segments have been completed, and production will take place before the middle of 2003. (author)