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Hiraoka, Hirokazu; Kawasaki, Kohei*; Kimura, Masanori; Togawa, Orihiko; Saito, Shota; Ezaki, Iwao*
no journal, ,
When the nuclear emergency occurs, inhabitants take the contamination inspection to evacuate. A large number of vehicle will come to the inspection area and make there congested. To do the quick inspection, simultaneous measurement of tires and wipers using the portable radiation portal monitors for vehicles is a key point. Consequently, we attempted the count rates obtained from tires and wipers are discriminated. First, the vehicle was driven at 5 km/h and the 
-ray counts rate was measured by the monitor. 
Ba sources were attached around the tire or on the wiper and measurements were taken 30 times each. Next, discrimination conditions based on a linear function were applied to the normalized count rates, with the maximum count rate of the measured values (Net value) set to 1.0, to evaluate the discrimination accuracy between the tire and the wiper. The evaluation results showed that the pattern with the source attached around the tire correctly discriminated 29 out of 30 times, while the pattern with the source attached on the wiper correctly discriminated 20 out of 30 times. It was found that in order to improve the accuracy of discrimination, the measurement method must be improved so that there is a large difference between measured values of the tire and the wiper.
Kawasaki, Kohei*; Hiraoka, Hirokazu; Ezaki, Iwao*; Kimura, Masanori; Togawa, Orihiko; Saito, Shota
no journal, ,
Vehicles carrying evacuees during a nuclear emergency are subject to contamination inspections, and the operation of screening by measuring tires and wiper are required. The introduction of portable radiation portal monitors for vehicles is expected to be quick tire inspections, however, it is difficult to inspect the tire and the wiper at the same time, so further speeding up the inspection process is an issue. In this study, we attempted to discriminate each type of contamination by using a different the new set up of detectors for the purpose of simultaneous inspection of tires and wiper. We will report the usefulness of the new set up and the results of simulation calculations of detector response under realistic contamination assumptions.
Hiraoka, Hirokazu; Kawasaki, Kohei*; Kimura, Masanori; Togawa, Orihiko; Saito, Shota; Ezaki, Iwao*
no journal, ,
In nuclear emergency, vehicles which evacuating inhabitants use be taken the contamination inspection. For the quick inspection, it seems that realization of simultaneous inspection of tires and wipers by portable radiation portal monitors for vehicles is necessary. In order to fulfill the simultaneous inspection, the authors develop the measuring method which is able to suitably distinguish and evaluate each contamination. Monte Carlo simulation showed ahead that the new set-up of detectors improves the discriminative ability for contamination. In this study, based on the simulation results, the authors attached radiation sources to a vehicle, and verified the ability by the new-setup. As a result, the ability improved compared to one of the usual method.
Watanabe, Yuki; Hosomi, Kenji; Kawasaki, Kohei*; Ezaki, Iwao*; Takada, Chie
no journal, ,
no abstracts in English
Kawasaki, Kohei*; Hiraoka, Hirokazu; Ezaki, Iwao*; Kameda, Shuji*; Kimura, Masanori; Saito, Shota
no journal, ,
In the current contamination screening plan, the vehicle's tires are measured using a portable radiation portal monitor, while wiper area is measured by an inspector using a survey meter. These two measurements confirm that contamination levels are below the screening thresholds. However, if both areas could be screened simultaneously using the portal monitor, it would improve the efficiency of the screening process. In this study, the degree of efficiency that can be expected from simultaneous screening by the portal monitor was verified through simulated screening using actual vehicles. The results showed that this screening method can contribute to a 9.4 second time reduction, from an average of 29.5 seconds to 20.1 seconds per vehicle, and a reduction of two inspectors per lane.
Hiraoka, Hirokazu; Kawasaki, Kohei*; Kimura, Masanori; Saito, Shota; Ezaki, Iwao*; Kameda, Shuji*
no journal, ,
In the current contamination screening plan, the vehicle's tires are measured using a portable radiation portal monitor, while wiper area is measured by an inspector using a survey meter. These two measurements confirm that contamination levels are below the screening thresholds. However, if both areas could simultaneously be screened using the portal monitor, it would improve the efficiency of the screening process. In this study, we estimated the accuracy of simultaneous screening using the portal monitor based on radiation counts obtained from examinations using a vehicle. As a result, it was shown that tire screening with the portal monitor is less affected by wiper area's contamination and achieves high accuracy. Furthermore, it was found that keeping the alarm threshold low in wiper area screening can reduce the likelihood of false negatives. However, since wiper area screening has a higher likelihood of false positives, it is recommended that an inspector re-measure wiper area only if an alarm is triggered.