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System Engineering and Safety Technology Research Group

 


 Marine transportation of radioactive materials plays an important role in the nuclear fuel cycle in Japan. In recent years, the cargo has been diverse and the volume of transportation has been increasing. Under this situation, demand for ensuring the safety and security of transport is growing.
 The System Engineering and Safety Technology Research Group conducts research on following subjects in order to ensure the safety and security in maritime transport of radioactive materials:


  1. Asessment technology of radiation shielding.
  2. Radiation measurement technology.
  3. Risk assessment/safety assessment technology.
  4. Environmental impact assessment technology, etc.

 We contribute to maritime administration by conducting safety assessments for nuclear fuel material transport containers and vessels, and providing technical support and new technologies related to rule revisions and international safety standards.



Conceptual diagram of nuclear fuel cycle and transportation in Japan




Conceptual diagram of nuclear fuel cycle and transportation in Japan

 

 Recently, we have been focusing on research on risk-based safety assessment methods aiming to reflect the knowledge gained from these studies not only on the risk assessment of radioactive material carriers but also on the risk assessment of ships in general.


 

Members 

(◎: Head of the Group,
☆: Concurrent Post)

 

Seiki Ohnishi
Kenichi Hakozaki
So Kamada



Main Research Topics

 
Survey of radioactive material concentration distribution in sea area and estimation method of radioactive material concentration in seabed soil
 Due to the Fukushima Daiichi Nuclear Power Plant accident following the Great East Japan Earthquake, radioactive materials were released into the atmosphere and ocean. In order to understand its impact on fisheries, to protect the environment of the sea area, and to understand the environmental dynamics, it is necessary to know the situation of radioactive substances distribution in the sea area for medium- to long-term. NMRI collaborate with the University of Tokyo on the surface mapping of the radioactivity concentration in the seafloor through the Nuclear Regulatory Agency project, etc., and also study the method for estimating the temporal change in the radioactivity concentration in the seafloor by ocean diffusion simulation.

 We are also conducting following research:

  1. Study on improvement of shielding safety evaluation method using Monte Carlo method for a radioactive material transportation container.
  2. Study on environmental impact assessment system for accidents during the transport of radioactive substances by ships.
  3. Study on risk assessment method for radioactive transport.
  4. Development of risk-based design support tools (fire, evacuation and chemical substance diffusion simulation).


  

Research Facilities

 
Shielding laboratory
 In the shielding laboratory, we conduct experiments to evaluate shielding performance of resins, serpentine concrete, boric acid water, etc. used as high performance neutron shielding materials. In addition, we evaluate shielding performance of models of spent fuel storage container (cask) for transportation. Furthermore, we conduct experiments to develop new shielding material with Akita University using a neutron source (Calfornium-252), and a gamma ray source (Cobalt-60).
 These experimental results include not only neutrons and primary gamma rays but also secondary gamma rays generated from thermal neutrons. With these data, we conduct detailed analysis using the continuous energy Monte Carlo code; MCNP(Monte Carlo N-Particle Transport Code) to improve and standardize the shielding performance evaluation method.


pict

Transport container model