[en] This report describes the methodology which could elicit probabilistic representation from the experts' knowledge or qualitative data. It is necessary to elicit expert's knowledge while we quantitatively assess the reliability of safety critical software using Bayesian Belief Nets(BBNs). Especially in composing the node probability table and in making out the input data for BBN model, experts' qualitative judgment or qualitative data should be converted into probabilistic representation. This conversion process is vulnerable to bias or error. The purpose of the report is to provide the guideline to avoid the occurrence of this kinds of bias/error or to eliminate them which is included in the existing data prepared by experts. The contents of the report are: o The types and the explanation of bias and error The types of bias and error which might be occur in the process of eliciting the expert's knowledge. o The procedure of expert's judgment elicitation. The process and techniques to avoid bias and error in eliciting the expert's judgments. o The examples of expert's knowledge appeared in the BBNs The examples of expert's knowledge (probability values) appeared in the BBNs for assessing the safety of digital system

[en] Recently practical needs have required quantitative features for the software reliability for Probabilistic Safety Assessment which is one of the important methods being used in assessing the overall safety of nuclear power plant. But the conventional assessment methods of software reliability could not provide enough information for PSA of NPP, therefore current assessments of a digital system which includes safety-critical software usually exclude the software part or use arbitrary values. This paper describes a Bayesian Belief Networks based method that models the rule-based qualitative software assessment method for a practical use and can produce quantitative results for PSA. The framework was constructed by utilizing BBN that can combine the qualitative and quantitative evidence relevant to the reliability of safety-critical software and can infer a conclusion in a formal and a quantitative way. The case study was performed by applying the method for assessing the quality of software requirement specification of safety-critical software that will be embedded in reactor protection system

[en] This report propose a method that can produce quantitative reliability of safety-critical software for PSA by making use of Bayesian Belief Networks (BBN). BBN has generally been used to model the uncertain system in many research fields. The proposed method was constructed by utilizing BBN that can combine the qualitative and the quantitative evidence relevant to the reliability of safety-critical software, and then can infer a conclusion in a formal and a quantitative way. A case study was also carried out with the proposed method to assess the quality of software design specification of safety-critical software that will be embedded in reactor protection system. The V and V results of the software were used as inputs for the BBN model. The calculation results of the BBN model showed that its conclusion is mostly equivalent to those of the V and V expert for a given input data set. The method and the results of the case study will be utilized in PSA of NPP. The method also can support the V and V expert's decision making process in controlling further V and V activities

[en] ZrO₂ pellets were made by cold pressing. It has previously been found that sintered ZrO₂ pellets can produce thermoluminescence (TL) when irradiated by 254, 302 and 366 nm ultraviolet radiation. The influence of the sintering process of ZrO₂ pellets on TL is presented in detail. Parameters of the sintering process, including sintering temperature, heating rate and the time pellets were kept at the sintering temperature, were investigated experimentally. The results show that some of these parameters can affect the TL sensitivity and the existence of TL peaks. The experimental parameters of the sintering process were used to fabricate ZrO₂ pellets for application in ultraviolet dosimetry. (author)

[en] In previous work it was found that there were peaks around 70, 100 and 235^oC in the thermoluminescence (TL) glow curve of zirconia read out immediately after ultraviolet (UV) irradiation, but the 70^oC peak faded within approximately 30 min. Thus only 100 and 235^oC TL peaks usually appeared in the TL glow curve if the readout was not taken immediately after the UV irradiation. The discovery of the 70^oC in the TL glow curve of zirconia read-out the second time, right after the first TL readout, is reported. The ZrO₂ still emitted TL to some extent in the second readout if no annealing was done after the first readout, but the 70^oC peak in the TL glow curve became the main peak. The recovery of the 70^oC peak can be explained as heat transferred TL of zirconia stimulated by heat energy from the heating planchet of the TL detector during the first readout. Detailed experimental work and discussion are presented. (author)

[en] For a lattice Λ with n vertices and dimension d equal to or higher than 2, the number of spanning trees N_ST(Λ) increases asymptotically as exp(nz_Λ) in the thermodynamic limit. We present exact integral expressions for the asymptotic growth constant z_Λ for spanning trees on several lattices. By taking different unit cells in the calculation, many integral identities can be obtained. We also give z_Λ(p) on the homeomorphic expansion of k-regular lattices with p vertices inserted on each edge

[en] This paper studies the transport phenomena of disordered systems in the thermal relaxation process by cluster impact on a solid surface. Constant-temperature molecular dynamics simulations were applied for nanoscale modelling. The surface wetting and epitaxial behaviours of deposited clusters with various flow and internal kinetic energy were investigated. This revealed that the internal temperature of clusters enhanced the lateral activity of atoms, while normal incident energy was related to atomic implantation. By exchanging momentum and energy from the system to a heat sink with constant temperature, the collision system reached thermal equilibrium after a long enough simulation time. The temperature decay profiles of the system were presented as an exponential-type function, which is dependent on the efficiency of the cooling model and the heat conductivity of the material. Finally, the nanostructure growth mechanism by cluster deposition was studied. It showed that both epitaxial film and voids were constructed by the cluster-island and island-island collision mechanism, which was dependent on the incident energy of the cluster and the surface temperature. As a dynamic behaviour of a nanostructure with a non-zero momentum of its mass centre, the rocking phenomenon was presented as an important characteristic of thin films by cluster deposition

[en] The optical attenuation of the thermoluminescent (TL) glow in sintered ZrO₂ pellets induced by gamma irradiation has been studied. The TL glow in locally made ZrO₂ pellets can only penetrate a few top layers and the attenuation of the glow is an exponential function of the thickness of the pellet. The ZrO₂ film was produced by the combination of laser evaporation and ion plating techniques vacuum-coated on an Al substrate. The microstructure of the resultant film has been studied by scanning and transmitting electron microscopy and X ray diffraction respectively. The results of gamma irradiation showed that both the ZrO₂ pellet and film can produce TL glows, but the glow curves show different peak positions. This difference is due to the difference in the microstructures of the pellet and the film; the film was found to be amorphous but the pellet belongs to baddeleyite crystalline structure. A thickness of more than 1 μm is necessary for the film completely covering the Al substrate and a promising TL dosemeter can be made by correct choice of film thickness. (author)

[en] For a two-dimensional lattice Λ with n vertices, the number of spanning trees N_ST(Λ) grows asymptotically as exp(nz_Λ) in the thermodynamic limit. We present an exact integral expression and a numerical value for the entropy (asymptotic growth constant) z_Λ for spanning trees on 19 two-dimensional lattices with more than one type of vertex given in O'Keeffe and Hyde (1980 Philos. Trans. R. Soc. A 295 553). Especially, an exact closed-form expression for the entropy is derived for net 14, and the entropies of net 27 and the triangle lattice have the simple relation z₂₇ = (z_tri + ln 4)/4. Some integral identities are also obtained

[en] For n-vertex, d-dimensional lattices Λ with d ≥ 2, the number of spanning trees N_ST(Λ) grows asymptotically as exp(nz_Λ) in the thermodynamic limit. We present an exact closed-form result for the asymptotic growth constant z_bcc(d) for spanning trees on the d-dimensional body-centred cubic lattice. We also give an exact integral expression for z_fcc on the face-centred cubic lattice and an exact closed-form expression for z₄₈₈ on the 4 8 8 lattice