[en] The RESUME95 exercise - Rapid Environmental Surveying Using Mobile Equipment, took place in Finland in August 1995. The objectives of the RESUME exercise were to compare different monitoring systems when used under the same conditions as well as to compare results from similar systems with different data analysis and presentation software. Another objective was to acquire some basic knowledge to standardize and cross calibrate the European air-borne gamma-ray surveying capability so that the results from different systems could be directly comparable. The exercise involved 10 airborn monitoring teams, 7 teams with vehicle monitoring systems as well as ground survey teams from 8 countries. Most systems incorporated GPS satellite navigational aids and computers for real time display of the data which was also recorded for post flight analysis. Most of the car- and airborne systems were based on Nal detectors whereas most of the In-situ systems and a few airborne systems were based on HpGe detectors. The exercise took place in an area near Lahti. Three different areas were surveyed. These were 1) An airfield near Vesivehmaa, which was intended as a calibration site. Soil samples had been taken previously and used to establish the ¹³⁷Cs activity of the soil as well as the activity of the natural radioactivity elements ⁴⁰K, ²¹⁴Bi and ²⁰⁸Tl. 2) An area contaminated by the Chernobyl nuclear accident, Area II. This area was intended to test the capabilities of the car- and airborne teams for mapping ¹³⁷Cs. A number of predefined points in the area were used by In-situ teams. 3) An area with a variety of hidden readioactive sources, Area III. These sources of ⁶⁰Co, ¹³⁷Cs, ¹⁹²Lr and ⁹⁹Tc ranged in activity from 0.6 mCi to 15 Ci and was used to test the capability of the different air-borne teams for locating lost radioactive sources. (EG)

[en] Nordic Safety Research (NKS) organised in August 1995 a field test of various techniques and instrumentation for monitoring radioactive fall-out. In an emergency situation, after a major release of radioactive material, many different measuring systems are going to be used, ranging from small hand hold intensitometer to complex spectrometer systems. In this test the following type of equipment were tested: Airborne spectrometers; Carborne spectrometers and dose rate meters; In situ spectrometers and intensitometers. Helinuc team was equipped of an airborne system and of a germanium device for in situ measurements. Different tasks were specified for each team: Mapping caesium fall-out and natural activity over two areas of 18 and 5 km²; Research of hidden sources. For measurements and data processing the respect of time allowed was strictly controlled for testing the ability of each team. (au)

[en] This paper presents the results obtained during the NKS, (EKO-3), Exercise Resume-95 by a group from the Division of Ionising Radiation and Fallout, FOA, Umeaa, Sweden. Field gamma measurements were performed in two areas with a HPGe-detector (p-type, 50% relative efficiency) mounted vertically 1 m above the ground or horizontally in a car. One of the areas was an airfield, Vesivehmaa, where 19 measurements were done. The calculated Cs-137 activity was 52.1 ± 4.5 kBq/m² assuming a two slice distribution model with a homogenous density and activity distribution in each slice. The report contains also the results from a task which included the finding, classification and estimation of the activity of hidden sources within two 10^* 10 m-areas. (au)

[en] Carborne radiation monitors were tested for point source responses at distances 10 m, 20 m, 50 m, 100 m, 150 m, and 200 m using speed of 20 km h^-1 and 50 km h^-1. A large pressurised ionisation chamber (PIC), and HPGe detector (relative efficiency 36.9%) and a NaI(Tl) scintillator detector (size 5'x5') were used. The sources had a nominal activity of 22 MBq (⁶⁰Co) and 1.85 GBq (¹³⁷Cs). The ⁶⁰Co source strength was under the detection limit in all measurements. The detection of the ¹³⁷Cs source is visually clear up to 50 m for the spectrometers and up to 20 m for PIC. Statistical analysis shows that ¹³⁷Cs source could be detected up to 100 m with the spectrometers and up to 50 m with PIC if the background is well known. (au)

[en] The main task of the team was to create a fallout map of ¹³⁷Cs in a specified area in Padasjoki Auttoinen village. The team used an MI-8 helicopter of the Finnish Air Force. The team had an HPGe system (relative efficiency 70%) to measure nuclide specific ground contamination level. For navigation the team took advantage of the DGPS service provided by Finnish Broadcasting company utilizing the RDS-channel to get position accuracy within 2 meters. The correction signal is reachable nationwide on the FM transmitter network. The system produced a distribution map for ⁴⁰K and fallout maps for ^134,137Cs using a Micro Station Program with TerraModeler application. The maximum measured ¹³⁷Cs ground contamination exceeded 130-140 kBqm^-2. (au)

[en] Geological Survey of Finland carried out its airborne gamma ray measurement flight for RESUME95 exercise at the planning stage of the exercise; actually 9 weeks beforehand. Although some of the flight parameters (line spacing 100 metres and altitude 30 - 40 metres) differ from those used by the other teams during RESUME95, the results obtained by GSF are in line with the others. Mapping Cs-137 fallout at Area II gave mean value of 83.8 kBq/m² and maximum of 137 kBq/m². (au)

[en] The task of the team was to locate and to identify hidden sources in a specified area in Padasjoki Auttoinen village. The team used AB-420 helicopter of the Finnish Frontier Guard. The team had two measuring systems: HPGe system (relative efficiency 18%) and 5'x5' NaI system. The team found two sources in real-time and additional two sources after 24 h analysis time. After the locations and characteristics of the sources were announced it was found out that altogether six sources would have been possible to find using the measured data. The total number of sources was ten. The NaI detector was good at detecting and locating the sources and HPGe was most useful in identification and calculation of the activity estimates. The following development should be made: 1) larger detectors are needed, 2) the software has to be improved. (This has been performed after the exercise) and 3) the navigation must be based on DGPS. visual navigation causes easily gaps between the flight lines and some sources may not be detected. (au)

[en] During the summer 1995 altogether 8,625 spectrometric and 3,108 dose-rate measurements were performed in Padasjoki Auttoinen village using carborne measuring devices. As a result ¹³⁷Cs fallout and dose-rate maps were produced. The highest measured values in the test area II were 160 kBq m^-2 for fallout and 0.22 μSv h^-1 for dose-rate. One hot spot was found beside the test area (dose rate 0.31 μSv h^-1). On the cultivated areas the measured count rates in ¹³⁷Cs-window are three to four times lower than in the forest areas in average, indicating an altered depth profile of caesium. (au)

[en] The Norwegian Radiation Protection Authority (NRPA) took part in the international survey measurement exercise RESUME95 that was arranged in Finland in August 1995. NRPA performed measurements with a simple car-borne measuring system based on standard equipment, a 3x3' NaI detector, an MCA and a GPS connected to a portable PC. The results show substantial variations in dose rate inside areas of a few square kilometres. Spectrum analysis shows that a major part of these differences are caused by variations in deposition of ¹³⁷Cs. Our results show that even standard 3x3' NaI detectors can be used for car based survey measurements in fall out situations and search for sources. The detection limits are higher than for larger detectors, but the main limiting factor seem to be the timing capabilities of the acquisition system. (au)

No abstract available