Methods of minimising doses incurred by external exposure while moving in radiation hazardous areas

Abstract

Radiation doses received by workers during their movement within areas contaminated as a result of events and activities, leading to emergency or existing exposure situations, may provide a substantial contribution to total external exposure during remediation work. This paper describes an approach to minimise worker external exposure in these circumstances, based on graph theory. The paper describes several tasks, including: searching for a route with the lowest dose, searching for an optimal bypass with a given set of control points and searching for the optimal road network coverage. Classical graph theory algorithms have been used (Dijkstra’s algorithm, Chinese postman problem and travelling salesman problem). Algorithms for solving the above mentioned problems have been developed and were included in the information-analytical system for radiation safety. This software has been applied for optimisation of protection during remediation work at the Andreeva Bay site of temporary storage for spent fuel and radioactive waste in the Kola Peninsula, both in the context of existing exposure situations and improving the preparedness for emergency exposure situations.

The development and application of a method for assessing radionuclide surface contamination density based on measurements of ambient dose equivalent rate

“…Also relevant is the expected behaviour of the potentially exposed people. If they are expected to move about frequently, or are just passing 10 For gamma quanta of 0.662 MeV energy emitted by 137m Ba (daughter radionuclide of 137 Cs), the layer of half attenuation in the air is≈180 m; for beta particles with the highest energy of 1.173 MeV, emitted in the course of 137 Cs decay, the length of the maximum range in air is ≈5.3 m [2]. 11 For beta particles with the highest energy of 1.173 MeV emitted in the course of 137 Cs decay, the length of the maximum range in soil is≈0.3 cm (assessment for low-humus soils with density ρ=2.7 g cm −3 ).…”

“…ADER is measured in order to restrict radiation exposure to workers and the public, while SCD is measured to find areas where decontamination is required. In case of the ADER measurement, gamma quanta which passed through the sensitive volume of the detector, are recorded, while during the SCD measurement alpha and beta particles also fall into the sensitive volume of the detector; nevertheless, there is a principal difference in geometry of irradiation of the sensitive volumes of the detector, because the penetrating power of photons, alpha and beta particles of the same energy varies by orders of magnitude 10 . The measurement of gamma ADER at 1 m height (typical height of human vital organs location) means the measurement in almost isotropic radiation field.…”

Further development and application of a method for assessing radionuclide surface activity distribution and source location based on measurements of ambient dose equivalent rate. Examples for Andreeva Bay, Chernobyl NPP and Istiklol

“…Today, the remediation of nuclear legacy sites is underway in the Russian Federation [1]. We have issued a number of publications on the problem of regulatory supervision over the rehabilitation of the Andreeva Bay site of the North-Western Center (NWC) for radioactive waste (RW) management of SevRAO [2][3][4][5]. The function of the Andreeva Bay site of the NWC is as a site for temporary storage (STS) of spent nuclear fuel (SNF) and RW (hereafter STS Andreeva Bay).…”

An Efficient Computing of Correlated Equilibrium for Cooperative $Q$-Learning-Based Multi-Robot Planning

“…[22], [23] In addition to accidental scenario, in routine operations as well [24], avoidance of radiation hot-spots (indicating high radiation intensity) within a working area is necessary to achieve proper implementation of radiation protection principles like ALARA (As Low as Reasonably Achievable). [25] In highly contaminated zone, use of drones or robots [26] for radiation mapping can also an reasonable alternative for effective decision making. Undoubtedly, handling these situations require knowledge about the paths that not only has minimum radiation intensity but also timeefficient.…”

“…Further, issues with the low convergence rate, premature convergence and difficulties on finding global minima in large-dimensional space may restrict application of this method. [16], [31] Among other approaches, Dijkstra [15], [25] and A* algorithm [16] was applied in several studies. [32] Due to the deterministic nature of the algorithm, it produces one solution for the optimum path, which may not necessarily be logistically feasible path owing to the presence of obstacles.…”