Results 1 - 2 of 2
Results 1 - 2 of 2. Search took: 0.013 seconds
|Sort by: date | relevance|
[en] In order to maintain competence or to train new employees, it is necessary to prepare and organize some training sessions suitable to the concerned audience. As a TSO (Technical and Scientific Support Organization), IRSN (Institute for Radiation Protection and Nuclear Safety) is particularly implicated in this issue, specifically in the field of human radiation protection, protection of the environment and nuclear safety. IRSN created recently an 'In-house University' containing different 'Schools': 'Assessment', 'Emergency Planning/Response'.... The main objective is to support IRSN employees following a specific route. Concerning the 'Assessment' school, this route is first composed of a training on general topics (e.g. 'how to perform an assessment?'), then of other training on specific topics ('nuclear criticality safety', 'fire risks', 'containment'...). Implemented teaching methods are innovative and less academic than it used to be. These methods have been taught by training professionals specialized in andragogy (methods and principles used in adult education). In this context, the 'nuclear criticality safety' (NCS) training has been completely renewed by the SNC department (Neutronics and Criticality Safety Department)of IRSN. Scheduled over a period of one week, each day an expert teacher stays with the participants and interacts with the other speakers planned in the agenda, which allows dynamic discussions. Moreover, various exercises in groups (using paper boards, post-its, videos...) give the opportunity to test the newly acquired knowledge. The session begins with general notions concerning NCS (physical properties, consequences of a nuclear criticality accident...). Then, each control mode (mass, geometry...) is discussed considering lots of examples from actual facilities. Finally, a review of past nuclear criticality accidents is done, and the impact of other risks (fire, flood,...) on NCS is evaluated. A future project is to propose an international training in English intended in particular for other TSOs via the ENSTTI organization (European Nuclear Safety Training and Tutoring Institute). (authors)
[en] This article presents an extensive study of the calculations performed in the configuration where the criticality safety is achieved by both controlling the mass of fissile material and the moderation (for example water) of a single unit. This case often occurs when the control of the fissile mass alone is not sufficient to economically or practically operate a process. This method is often used for the fuel fabrication where an important quantity of powder need to be handled but may also be met in other nuclear facilities and transportation. In this context, from a calculation point of view, a homogeneous distribution of the moderation within the fissile material is generally not a penalizing configuration. So a heterogeneous repartition of the moderation is then considered: it currently consists in a given part of the fissile material uniformly moderated by the entire quantity of the moderator, this system being surrounded by the rest of the dry fissile material and eventually another reflector (water, concrete, lead, etc.). This paper will firstly briefly discuss how to calculate safety limits for this kind of configuration, in the past and nowadays, using state-of-the-art algorithms. Then, new results will be presented for this kind of configuration with various enrichments and densities. These calculations show that the penalizing configuration depends on the maximum dry density of the fissile material considered. The new results obtained with high maximum dry densities are more restrictive than those previously presented.