Development of KURAMA-II and its operation in Fukushima
Introduction
The magnitude-9 earthquake in eastern Japan and the following massive tsunami caused a serious nuclear disaster of Fukushima Daiichi nuclear power plant. Serious contamination was caused by radioactive isotopes in Fukushima and surrounding prefectures. KURAMA [1] was developed to overcome the difficulties in radiation surveys and to establish air dose-rate maps during and after the present incident. KURAMA was designed based on consumer products, and enabled a large number of in-vehicle apparatus to be prepared within a short period owing to its high flexibility in the configuration of data-processing hubs or monitoring cars. KURAMA has been successfully applied to various activities in the radiation measurements and the compilation of radiation maps in Fukushima and surrounding areas.
As the situation was stabilized, the main interest in measurements moves to the tracking of the radioactive materials that have already been released into the environment surrounding the residential areas. KURAMA is not suitable for such purposes. Even though KURAMA enables measurements with a large number of monitoring cars over a wide area at one time, it still requires a trained operator and a driver in each monitoring vehicle. This means that a huge amount of resources and efforts will be required once the surveillance is changed into long-term (several tens years) and detailed monitoring in residential areas. Such monitoring can be realized efficiently if vehicles that periodically move around the residential areas, such as city buses, delivery vans or motorcycles for mail delivery, have compact and full-automated KURAMAs onboard. KURAMA-II is designed for such a purpose.
In this paper, a system outline and the development of KURAMA-II as well as the results of continuous monitoring using KURAMA-II will be introduced.
Section snippets
System outline of KURAMA-II
The system outline of KURAMA-II is shown in Fig. 1. KURAMA-II basically stands on the architecture of KURAMA [1], but the in-vehicle part has been totally re-designed. In KURAMA, a notebook PC was used in an in-vehicle unit, but KURAMA-II is based on the CompactRIO series of National Instruments [2] to obtain better toughness, stability and compactness. The 3G/GPS module for CompactRIO by SEA [3] provides time and location data as well as connection to a 3G network. The radiation detection part
Continuous monitoring by city buses
Recent applications of the KURAMA series are mainly with KURAMA-II because of its autonomous operation and ease of handling. One of such applications is continuous monitoring with KURAMA-II on city buses (Fig. 5). City buses are suitable for continuous monitoring purpose in residential areas because of their fixed routes in the center of those areas, and their routine operations.
Following the success of a field test in Fukushima city in 2012, the coverage area has been expanded to other major
Conclusion and future prospects
KURAMA-II has been developed to enable the long-term monitoring of the air dose rate in residential areas. A test operation throughout the year successfully observed the trends of air dose rates in residential areas, e.g., the shielding effect due to snowfall and reductions due to decontamination activities. Pulse-height spectra obtained by KURAMA-II provide important information concerning radioactive nuclides composing the air dose rates in residential areas. No severe troubles, such as the
Acknowledgments
The authors are grateful to Dr. Mizuno, Mr. Kimura, Mr. Ito and Mr. Kojima of the Fukushima prefectural government for a continuous support to field tests of KURAMA-II and the establishment of a monitoring scheme based on KURAMA-II on city buses. The authors are indebted to Dr. Saito, Mr. Yoshida and Dr. Takemiya at JAEA for discussions concerning the operation of KURAMA, and to Dr. Tsuda at JAEA for evaluating the G(E) functions of C12137 series. Mr. Nakamura at Hamamatsu Photonics offered the
References (14)
- et al.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
(2013) - National Instruments, NI CompactRIO, Web page, 〈http://www.ni.com/compactrio/〉,...
- S.E.A. Datentechnik GmbH, SEA 9724, Web Page,...
- Hamamatsu Photonics Corporation, Radiation detector modules C12137 series, Catalog,...
- D. Inc., Dropbox, 〈http://www.dropbox.com〉,...
- et al.
Health Physics
(1966) - S. Moriuchi, A Method for Dose Evaluation by Spectrum-Dose Conversion Operator and the Determination of the Operator,...
Cited by (33)
Calculations for ambient dose equivalent rates in nine forests in eastern Japan from <sup>134</sup>Cs and <sup>137</sup>Cs radioactivity measurements
2021, Journal of Environmental RadioactivityDecreasing trend of ambient dose equivalent rates over a wide area in eastern Japan until 2016 evaluated by car-borne surveys using KURAMA systems
2019, Journal of Environmental RadioactivityCitation Excerpt :The air dose rates were automatically measured every 3 s (in the first and second surveys, every 5–10 s) and sent to a data collection server along with the position coordinate information recorded by the GPS. The specifications and detailed characteristics of the KURAMA and KURAMA-II systems are described in the references (Tanigaki et al., 2013, 2015; Tsuda et al., 2013). The basic characteristics of the KURAMA-II, such as response variation with energy, dose rate, and incident direction of gamma rays, were evaluated in irradiation examinations using a calibrated radiation source (Tsuda et al., 2015).
Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016
2019, Journal of Environmental RadioactivityCitation Excerpt :Considering these specific features of walk survey, we decided to launch walk survey in the mapping projects. The second version of Kyoto University RAdiation MApping (KURAMA) system (The KURAMA-II system) was originally developed to survey air dose rates installed in a car (Tanigaki et al., 2015), and was used for the car-borne surveys in the mapping projects (Andoh et al., 2015b). We applied the KURAMA-II system to our walk survey.
External dose evaluation based on detailed air dose rate measurements in living environments
2019, Journal of Environmental RadioactivitySummary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident
2019, Journal of Environmental Radioactivity