Investigation of the contamination induced by the cars travelling in the restricted area

Traffic on the Route 6 will increase after the revision of the evacuation area and the restricted one. The purpose of this investigation is to study on the contamination induced by cars travelling in the current restricted area. This study focuses on the police cars patrolling all over the restricted area, whose total number is up to 101 cars. The measurement issues are shown as the following, 1. Background contamination, 2. Initial contamination of a car, regarding a radiator, a tire and a tire-house in the front and the rear, just before going into the restricted area, 3. Subsequent contamination of the same parts just after leaving the area, 4. Question about the travelling routes, the districts, and the environmental conditions of every car. Each background contamination at 1cm, 30cm and 1.0m height shows about 200 cpm and keeps stable. The histogram of the contamination difference between the initial and the subsequent one corresponds to normal distribution, whose mean value lies about zero in the measurement cases of the radiators and the front and rear tires of all the cars. It means that no additional contamination by travelling in the restricted area has occurred on such parts. On other hands, the possibility of additional contamination which exceeds 500 cpm per day has been suggested particulary on the tire-houses. The contamination difference of the car travelling on roads between with and without pavements has not been identified as well as in weather conditions at least based on the obtained histograms. Eventually, patrolling around the restricted area or passing mountainous zones in the area has been recognized as a common factors which increases additional contamination to more than 500 cpm per day, but in such a case the accumulated contamination trend with daily travelling has not been identified. The average contamination level basically remains low against the screening one, 13,000 cpm, defined in the regulation. However, much attention should be paid so as not to travel particularly on the muddy road in the districts expected to be highly contaminated. (author)