[en] The Swedish ATV data base has been analyzed with respect to the coverage of component failures in Swedish BWRs, and the correctness and quality of the ATV failure information. The main findings regarding the years 1974-1978 are: the coverage of occurred component failures is not greater than about 50 %, although the trend is upward; the correctness of the failure coding and the quality of the plain-language remarks should be enhanced; as the system is now, the coverage and description of common cause failures and human error is insufficient as far as the needs in probabilistic risk analyses are concerned. (Auth.)

[en] The environmental effects of SECURE-400 MW has been investigated for normal operation and after an accident. When calculating the doses during normal operation it has been assumed that 0.1 % of the fuel elements in the core have fuel cladding damages. The doses after an accident have been calculated only for the cases when there might be an effect on the environment: accidents at change of fuel, fracture of the biggest gas pipe and fracture of the main coolant loop. The result of the investigation is that a core melting accident in SECURE 400 is impossible due to the design of the different systems. Other typs of accidents which might happen will give extremly low doses to the environment. The doses will not differ significantly from doses during normal operation. (K.K.)

[en] Experience feedback can be extended to include almost all activities related to plant safety and operation, from control room operation to maintenance tasks. The presented safety related areas - i.e. analysis of operating incidents, education and training of operating personnel - are perceived by the Swedish utilities as the most important points of an integrated system for experience feedback. Suggestions and comments are formulated after two years of operative utilization of the Swedish system. (U.K.)

[en] This chapter discusses the collection, evaluation and feedback of information about incidents and transients in Swedish and foreign nuclear reactors. The Three Mile Island-2 accident demonstrated that a more structured system for experience feedback was needed to ensure a cumulative learning process from precursor incidents and transients. Topics considered include the Swedish transient data base, statistical trends of plant transients, the root causes of transients, and the impacts of plant transients (the impact on plant safety, the impact on plant availability). The Swedish plants have experienced only one transient sequence which could be classified as an abnormal occurrence (a small loss-of-coolant accident in the Ringhals 2). It is concluded that for increased knowledge and protection, the Swedish nuclear industry has to rely upon international operating experiences

[en] This article is a review of current European collaborative efforts with the Russian Federation on safeguards matters. Three particular projects are reviewed: (1) development of physical inventory-taking at VVER-1000 nuclear plants and at a low enrichment fuel fabrication plant, (2) development and implementation of a centralized information system, and (3) development and implementation of a computerized nuclear materials accounting system

[en] The paper presents the safety evaluation of the SECURE nuclear plant concept, which has been developed in a joint Finnish-Swedish design project. SECURE is an acronym of Safe and Environmentally Clean Urban REactor. The safety study covers the evaluation of inherent safety properties of the plant, the assessment of plant system reliability, environmental aspects and consequences both of normal operation and of potential accidents. Safety questions associated with urban siting are discussed. (author)

[en] This study reports on the computational analysis and experimental calibration of the whole-body counting detection equipment at the Nuclear and Technological Inst. (ITN) in Portugal. Two state-of-the-art Monte Carlo simulation programmes were used for this purpose: PENELOPE and MCNPX. This computational work was undertaken as part of a new set of experimental calibrations, which improved the quality standards of this study's WBC system. In these calibrations, a BOMAB phantom, one of the industry standards phantoms for WBC calibrations in internal dosimetry applications, was used. Both the BOMAB phantom and the detection system were accurately implemented in the Monte Carlo codes. The whole-body counter at ITN possesses a moving detector system, which poses a challenge for Monte Carlo simulations, as most codes only accept static configurations. The continuous detector movement was approximately described in the simulations by averaging several discrete positions of the detector throughout the movement. The computational efficiency values obtained with the two Monte Carlos codes have deviations of less than 3.2 %, and the obtained deviations between experimental and computational efficiencies are less than 5 % This work contributes to demonstrate the great effectiveness of using computational tools for understanding the calibration of radiation detection systems used for in vivo monitoring. (authors)

[en] The efficiency calibration of whole-body counters (WBCs) for monitoring of internal contaminations is usually performed with anthropomorphic physical phantoms assuming homogeneous activity distribution. Besides the inherent limitations of these phantoms in resembling the human anatomy, they do not represent a realistic activity distribution, since in real situations each incorporated radionuclide has its particular biodistribution after entering the systemic circulation. Moreover, the activity content in the different organs and tissues comprising the biokinetics is time dependent. This work aims at assessing the whole-body counting efficiency deviations arising from considering a detailed voxel phantom instead of a standard physical phantom (BOMAB) and at evaluating the effect of the anatomical differences between both phantoms. It also aims at studying the efficiency considering the biodistribution of a set of radionuclides of interest incorporated in the scope of environmental and occupational exposures (inhalation and ingestion) and at computing the time-dependent efficiency correction factors to account for the biodistribution variation over time. For the purpose, Monte Carlo (MC) simulations were performed to simulate the whole-body counting efficiencies and biokinetic models were used to estimate the radionuclides' biokinetic behaviour in the human body after intake. The comparison between the efficiencies obtained with BOMAB and the voxel phantom showed deviations between 1.8 and 11.7 %, proving the adequacy of the BOMAB for WBC calibration. The obtained correction factors show that the effect of the biodistribution in the whole-body counting efficiency is more pronounced in cases of acute activity uptake and long-term retention in certain organs than in cases of homogeneous distribution in body tissues, for which the biokinetics influence can be neglected. This work further proves the powerful combination of MC simulation methods using voxel phantoms and biokinetic models for internal dosimetry studies. (authors)

[en] This work reports on the use of three state-of-the-art Monte Carlo codes (MCNPX, PENELOPE, FLUKA) in the efficiency calibration of a Broad-Energy Germanium (BEGe) detector. Initial discrepancies found between the experimental and computational efficiency values are related to the poor knowledge of some physical parameters of the detector (dead-layers, crystal dimensions, etc.). As a consequence, a sensitivity analysis was carried out. Each parameter was systematically analyzed, and an accurate model of the detector was determined. The obtained results are consistent, allowing this model to be used in computational efficiency calibrations of the equipment at stake.

[en] A whole body counting system is in operation at the Nuclear and Technological Institute, in Portugal. Computational methods were used to determine the detection efficiency; a well-known source of bias in modelling the behaviour of a HPGe detector is the insufficient knowledge regarding the thickness of the lithium dead layer. In order to accurately simulate the detection system and to achieve agreement between the Monte Carlo results and the performed measurements, the value for the dead layer thickness was optimized.