A Monte Carlo simulation based on the physical processes described by a partial redistribution function has been developed. Results are in good agreement with analytical calculations. The simulation has been tested for the rare gases Ar, Kr and Xe in the pressure range between 0.01 and 10 Torr.
The European ALARA Network regularly organises workshops on topical issues in radiation protection. In light of the Fukushima accident, the most recent workshop questioned the application of the ALARA principle in emergency exposure situations. This memorandum presents the conclusions and recommendations of this workshop. One of the outcomes is that the process of optimisation in emergency exposure situations should be flexible enough to be able to modify or refine decisions over the course of an accident. In the urgent phase, decisions must be made in a very time-constrained environment, based on scarce, uncertain and sometimes unreliable information. In this phase, optimisation and protection strategies are therefore developed and applied on the basis of conservative assumptions or 'reasonably foreseeable worst-case scenario' which could lead to an overestimation of the consequences. In the intermediate phase, knowledge of the situation improves, and more time is available to make the decision. This is reflected by adopting a less conservative approach, and transitioning to a more appropriate optimisation adapted as effectively as possible to the various exposure situations. When the situation is eventually stabilized (transition phase), there is time to shape the measures taken previously to reflect local conditions in the affected territories. In every phase, consideration should be given to the stakeholders, so that their needs and requirements can be incorporated as effectively as possible.
The European ALARA Network regularly organises workshops on topical issues in radiation protection. The topic of the 18th workshop was ‘ALARA for Decommissioning and Site Remediation’. The workshop was jointly organised with the ISOE Working Group on Decommissioning (ISOE WG-DECOM) and the French Atomic Alternatives Energy and Atomic Energy Commission (CEA). The main objective was to examine the conceptual and practical aspects of the implementation of the optimisation principle (or ALARA principle) in the ‘nuclear’ and ‘non-nuclear’ sectors and also for legacy sites. This memorandum presents a synthesis of the presentations and working groups discussion that took place. It also summaries the conclusions from former EAN workshops on the same topic (1997, 2006) to highlight the commonalities and the new topics.
The theoretical scheme for applying the ALARA principle is illustrated by the various presentations of decommissioning and remediation (D&R) projects given at the workshop. The theoretical scheme includes, a starting point, the planning and implementation of the D&R strategy (including ALARA analysis) and the definition of an end-state. To lay down the foundations of ALARA, the initial characterisation should be comprehensive; considering not only radiation protection but other risks and circumstances both on site and off site. Decision-making is not trivial because many factors influence the D&R strategy and they can be addressed together using an holistic approach. A general methodology for such an approach in D&R was drafted by the participants.
Techniques are apparently industrially mature and dosimetric data suggest that good control has been achieved, however experience shows that the D&R strategy will go through multiple adaptations along the way. The management of wastes remains a challenge in many cases as well as the decision on the end-state leading to question of what is a ‘sustainable ALARA end-state?’.
When calibrating neutron monitors, it is important to correct for scattering effects. In general, the correction factors depend on the type of source and monitor used, and on the configuration of the calibration room. These correction factors have been determined for the specific non-symmetric configuration of the calibration room used at SCK.CEN by means of the different analytical techniques recommended by the ISO. These results are compared with each other and also with the outcome of numerical calculations performed using the Tripoli-3 and MCNP 4B code.
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