Workers Of Nuclear Facility Research Articles

Design and Development of a Wireless Robotic System for Radiation Detection and Measurement

A wireless robotic system has been proposed for radiation measurement and monitoring around nuclear facilities. The purpose of the robot is to assist the radiation workers from getting unwanted radiation exposure. The system includes a ground vehicle, GM tube-based radiation counting unit, Raspberry Pi, Pi camera module, and web-based controlling and monitoring unit. With the developed robotic system, the robot is controlled from a server to be moved towards the desired location and measure the radiation level. Radiation level of natural back several radioactive point sources (Cs 137, Co 60, Mn 54) located at different places in the laboratory, has been measured and compared with a GM tube-based commercial survey meter Gamma Scout, w/ALERT model. Analyzing the measured data a deviation has been found varying from 0.29 to 2.18. The proposed system is suitable for radiation detection and measurement in absence of radiation workers in nuclear facilities.

DL-RRT* algorithm for least dose path Re-planning in dynamic radioactive environments

Abstract One of the most challenging safety precautions for workers in dynamic, radioactive environments is avoiding radiation sources and sustaining low exposure. This paper presents a sampling-based algorithm, DL-RRT*, for minimum dose walk-path re-planning in radioactive environments, expedient for occupational workers in nuclear facilities to avoid unnecessary radiation exposure. The method combines the principle of random tree star (RRT*) and D* Lite, and uses the expansion strength of grid search strategy from D* Lite to quickly find a high-quality initial path to accelerate convergence rate in RRT*. The algorithm inherits probabilistic completeness and asymptotic optimality from RRT* to refine the existing paths continually by sampling the search-graph obtained from the grid search process. It can not only be applied to continuous cost spaces, but also make full use of the last planning information to avoid global re-planning, so as to improve the efficiency of path planning in frequently changing environments. The effectiveness and superiority of the proposed method was verified by simulating radiation field under varying obstacles and radioactive environments, and the results were compared with RRT* algorithm output.

Grid-based RRT∗ for minimum dose walking path-planning in complex radioactive environments

This paper develops an approach to provide path navigation with minimum dose for occupational workers in nuclear facilities to increase personnel safety. An algorithm called GB-RRT∗ is proposed by combining the principle of the rapidly exploring random tree star (RRT∗) with the grid searching strategy. The proposed hybridized algorithm compensates for the weaknesses of RRT∗ with the strengths of the grid search strategy, and is applicable in complex environments with obstacles and narrow areas without relying on pre-designed road networks. Simulation results of the proposed algorithm under three radioactive environments with sparse obstacles, area cluttered with obstacles, and narrow areas are compared with those derived from RRT∗. The results show that the GB-RRT∗ performs better than RRT∗ in both convergence and reliability toward achieving the minimum dose path. Hence, we present a more reliable and efficient for providing the minimum dose path for occupational workers especially in complex radioactive environments with clutter obstacles and narrow areas.

The path-planning in radioactive environment of nuclear facilities using an improved particle swarm optimization algorithm

It is important to ensure the radiation safety of workers in nuclear facilities. The path-planning technology is one of the effective ways to reduce the radiation exposure to the workers in the radioactive environment of nuclear facilities. This work studies the path-planning technology in radioactive environment of nuclear facilities, and proposes an improved particle swarm optimization (PSO) algorithm to solve the path-planning problems. To be specific, particle swarm optimization algorithm is associated with chaos optimization algorithm, and new mathematical dose calculation models for the path-planning problem are built. Then, experimental simulation for 3 cases is carried out and the results are compared to those from traditional PSO method. In the first two cases, the average effective doses from the improved PSO method are similar to those from traditional PSO method, but its possibility that the effective dose value is too large becomes smaller. And this trend is more obvious in Case 3. Specifically, the effective dose value above 800 μSv is cut by 25% for the improved PSO method. Besides, the average effective dose decreases about 29 μSv in Case 3. Meanwhile, the overall convergence rate isn’t affected. Hence, the proposed path-planning method in the radioactive environment of nuclear facilities is demonstrated to be effective through the experiments and analysis.

The simulation method based on skeleton animation model and organ-monitoring-points for exposure dose assessment to workers in radioactive environments

The objective of this paper is to develop a dose assessment method that takes into account the working postures and the non-uniformity of the radiation fields to ensure the radiation safety of workers in nuclear facilities. To simulate different working postures, the working posture models were developed with skeletal animation technology. And to assess the exposure dose to workers in a non-uniform radiation field, virtual reality technology was used to develop a model of a hypothetical human with organ-monitoring-points distributed in his/her organs and tissues. And then a dose assessment method based on skeletal animation technology and the organ-monitoring-points was developed. Simulation results were compared with that of MCNP, the point model and the organ’s minimum bounding box model, and they show that the method is effective in providing dose assessments to workers, taking into consideration the working postures and non-uniformity of radiation environments.

A sampling-based method with virtual reality technology to provide minimum dose path navigation for occupational workers in nuclear facilities

This paper proposes a sampling-based method (SBM) for planning minimum dose path navigation for workers in nuclear facilities. To simulate and avoid obstacles, they were approximated by a combination of basic geometries and detected with the aid of virtual reality. To obtain an optimized walking path with minimum dose without considering the pre-designed road networks, a sampling-based method that utilizes the rapidly exploring random tree star (RRT*) algorithm, applicable in both continuous and discrete radiation fields, was proposed and implemented. The performance of this method was evaluated by simulating walk paths and estimating their radiation dose rates in a hypothetical nuclear facility, and the simulation results were compared with those derived from Dijsktra's algorithm under various radioactive environments.

Epidemiological Studies of radiation workers in nuclear facilities

INWORKSよりも10年前の2005年，15カ国の原子力産業に従事する放射線作業者の放射線疫学研究結果が発表された。この研究は｢15カ国研究｣と呼ばれ，低線量，低線量率，遷延被ばくで統計的に有意ながん死亡率が確認される結果を示したが，線量評価に問題があるカナダのデータを除いた結果，統計的に有意ながん死亡率は確認できなかった。15カ国研究では線量評価が困難との理由で，比較的被ばく線量が高いと考えられる中性子被ばく者と内部被ばく者を除いたことが統計的検出力が十分でない一因であると考えられた。

Epidemiological Studies of radiation workers in nuclear facilities

Epidemiological Studies of radiation workers in nuclear facilities

Epidemiological Studies of radiation workers in nuclear facilities

Epidemiological Studies of radiation workers in nuclear facilities

Prior malignant neoplasms as a risk factor for the second cancer in a cohort of employees of enterprises of the nuclear industrial complex

Purpose. Assessment of the persistence ofprevious malignancy as a risk factor for the detection of subsequent cancer in a cohort of nuclear workers. Material and methods. Retrospective cohort study with 60 years of follow-up on 22.373 workers of nuclear facility recruited from 1948 to 2008, with the use of data on individual external and internal dosimetry, and information about cancer incidence and mortality rate due to cancer neoplasma (CN). Results. In the studied cohort second and subsequent CN were diagnosed in 6,4% cases, out of them 92,4% were cases of second cancers, in other cases the number of CN was more than two. 8% of cases ofprimary multiple cancers were presented by non-melanoma skin cancers (NMSC). Mean age ofpersons with more than one diagnosis of cancer was 67 years. The relative risk of the detection of second CN (excepting NMSC) among persons with already diagnosed previous cancer was about 4 times higher in comparison in persons without diagnosis of solid cancer. Discussion. Detected solid tumors were proposed to be diagnosed in the order of their occurrence, but it cannot be excluded that in different latent periods of solid cancers of various localization this condition may fail to comply. The radiotherapy and the effect of dispanserization could play the essential role in the occurrence of second and subsequent cancers when the possibility of the detection of CN in a patient being under dispensary observation by oncologist is higher than in persons without dispensary observation. At the same time, the one possibility of carcinogenic effect of the first malignancy must not be excluded. Conclusions. Cancer risk among nuclear workers who have previous malignancy was 4 times higher in comparison with workers who had no previous diagnosis of cancer.

放射線防護の最適化における単位集団線量の貨幣評価値

The monetary value of unit collective dose, which represents the benefit of dose reduction due to the protective measures, is a key element in implementing the optimization principle of the radiation protection. The objectives of this paper are to evaluate the country-specific monetary value of unit collective dose reflecting the economic and population characteristics in Japan, as well as to analyze the balance of the cost and benefit of the radiological protective measures. When we calculated the monetary values of unit collective dose in Japan using human capital method and willingness to pay approach, the values were around several million yen/person-Sv and 20 million yen/person-Sv, respectively. In addition, we surveyed the data on costs of radiological protective measures per the avoided person-Sv. As the results of comparing the cost and benefit, the costs of radiological protective measures to reduce the concentration of radon in homes and to protect workers in nuclear facilities were balanced with the benefit. On the other hand, the costs of radionuclide emission control measures at industrial facilities tend to be higher than the benefit of those measures.

Performance Assessment on Continuous Air Monitors Under Real Operating Conditions

In the nuclear industry, workers may be exposed to artificial radioactive aerosols. These aerosols are generally composed of particles with a diameter between 0.1 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\hbox {m}}$</tex> </formula> and 10 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\hbox {m}}$</tex></formula> . To protect workers in nuclear facilities, monitors continuously measure radioactivity in the air. The main function of the monitor is to provide real-time measurement of activity concentration. Measurement of aerosol activity concentration can be affected by a number of factors specific to the aerosols and the instrument.

Enhancement of Surface Properties of Metal Materials by Underwater Laser Processing

The authors have developed underwater laser processing, namely welding and peening, to enhance surface properties of metallic components. The process developed could significantly reduce radiation dose to workers in nuclear facilities due to the shielding effect of water from radiation as well as due to remote operation attainable by laser technologies. Laser welding or cladding makes corrosion-resistant layers on the surface of components underwater, which reduces stress corrosion cracking (SCC) susceptibility. Various metallurgical and mechanical tests were performed to prove that the laser cladding made sound layers even if the surface had been degraded. Laser peening imparts compressive residual stress in near-surface layers by irradiating intense laser pulses without any surface preparation. High pressure plasma generated through ablative interaction underwater impinges on the surface and induces plastic strain to make compressive residual stress. Both processes are used to enhance surface properties, such as resistance to SCC, fatigue or wear of various metal materials.

原子力発電所作業者を対象とした個人モニタの装着基準に関する実験的考察

原子力発電所作業者を対象とした個人モニタの装着基準に関する実験的考察