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The ‘GROUNDHOG’ service, offered by Nuvia Limited, provides a range of facilities to allow land and buildings, potentially contaminated with radioactive materials, to be assessed. The results of Groundhog surveys can be used to demonstrate the absence of types of contamination, or to plan the remediation of contamination that has been discovered. Groundhog surveys can provide information that allows waste volumes, and thus cost, to be reduced or for minimisation of land disturbance.
The Groundhog service provides a ‘family’ of radiation monitoring tools or services that encompass all types of radioactive contamination that can be detected in the field. The family covers the range of radioactive contamination from those found in military legacies such as radium luminising works through to discharges from nuclear research and processing facilities.
The core features of the Groundhog service are: the collection of a high density of survey measurements, generally more than one measurement in each square metre; automatic recording of all measurements data; the maintenance of quality assurance records to provide a complete ‘audit trail’ from each measurement to the final report delivered to the customer; the use of database and Geographical Information Systems to provide high-quality analysis and presentations, both in reports and data delivered to customers for their own use. All members of the Groundhog family take advantage of these features.
Groundhog can be readily deployed in a wide range of ways, from fully portable systems for use in compact or difficult areas, through to large area surveys using banks of detectors mounted on vehicles. Groundhog has also been deployed for ‘down hole’ monitoring of boreholes, and surveying of marine sediments. Another core feature of the Groundhog service is the ability of Nuvia Limited to rapidly design, validate and implement custom solutions for far-from-routine radiation surveys.
The Groundhog service covers all aspects of radiation surveys, from consultancy on the design of survey and sampling procedures, through to the design and implementation of remediation techniques and assay procedures. The Groundhog technologies can also be directly applied to assay procedures, so can provide continuity and compatibility of measurement, from first stage assessment, through remediation, to final clearance of land for future use.
Groundhog ‘Fusion’ is the general-purpose technology used for Groundhog services. Fusion systems can be used for portable surveys or several detectors can be combined on a vehicle.
Fusion systems are configured with 76x76mm (or smaller) Sodium Iodide detectors coupled to an advanced gamma radiation spectrometer. The detector and spectrometer are mounted in Carbon Fibre Composite cases, to reduce the weight of the detector and to improve the transmission of low-energy gamma radiation. The detector and spectrometer are connected to an Ultra-Mobile PC (UMPC) carried by the operator (as seen below) or fitted to the vehicle.
A mapping-grade GPS (actually GPS + GLONASS) is used to calculate the position of every radiation measurement with sub-metre accuracy. A survey-grade GPS may be used if decimetre accuracies are required.
Nuvias ‘GARNET’ software, running on the UMPC, logs the radiation and positional data from the instruments. Radiation data can be logged in a wide variety of ways, from simple counts-per-second through to full gamma radiation spectra every second. The rate at which data is collected can also be changed to allow the ‘over sampling’ which is essential for detecting very small items of radioactive materials.
The software can be configured with highly-flexible alarms to allow the operator to take action when contamination is discovered, which is important for the beach surveys described later.
Groundhog Fusion systems are typically used in projects which need to detect Caesium-137 distributed in soils at levels of 200-400 Bq per kilogramme. However, Fusion is the most flexible of the Groundhog family and has been used for surveys of sites contaminated with Radium-226 from luminous paints and for surveys of military dockyards where Cobalt-60 is of concern.
Groundhog Insight is a variation of the Fusion system, equipped with a FIDLER (Field Instrument for the Detector of Low-Energy Radiation) detector. This is a 125mm diameter by 1.6mm thick Sodium Iodide detector. The detector is used for measuring low-energy radiation and is ideal for detecting Amercium-241 and can detect Plutonium-239. The detector is contained in a carbon fibre case which has only 0.4 mm thickness over the face of the detector. As with Fusion, a gamma radiation spectrometer is used.
Groundhog ‘Evolution2’ and ‘Synergy’
These systems are designed for the detection of ‘particles’ of radioactive material, notably on beaches at Dounreay in Scotland and Sellafield in England. These particles of material are typical the size of a grain of sand or smaller. At Dounreay the particles are predominantly of Cs-137 and at Sellafield Am-241, Plutonium and Cs 137.
Groundhog Evolution2 systems are equipped with five 400x76mm Sodium Iodide detectors, arranged to survey a 2 metre strip of sand in each sweep. This is ideal for the detection of Cs-137 particles of typically 103–105 Bq in the top 100 200mm of the sand.
Groundhog Synergy systems are equipped with five 400x76mm detectors and an additional eight Insight (FILDER) detectors to improve the detection of Am-241, typically to levels of 104-105 Bq in the surface layer of the sand.
Because of the dynamic nature of the beach environment, it is not possible to map the beach and then return to remove particles. Particles must be removed as soon as they are detected. Thus the systems are equipped with advanced ‘alarm’ mechanisms to detect a variety of particles.
Groundhog Data Analysis
Data analysis may be conducted during the survey, using simple analysis tools which produce ‘alarm’ signals, or using a gamma radiation spectrum display with simple radionuclide analysis features. The spectrum display may allow the operator to identify the contaminant if the field if this is required.
However, analysing the data following a survey allows the more powerful features of Geographical Information Systems (GIS) to be employed. Typical survey practice is to collect the data at the end of each day and analyse it, to confirm the quality of the survey and to plan the next days work.
Nuvia uses the ESRI ‘ArcGIS’ software and has extended it to improve the analysis of radiation survey data. These features include the ability to select, group and analyse the gamma radiation spectra that can be collected during Groundhog surveys.
Groundhog surveys are also used to support remediation strategies based on in-situ selective sentencing of waste, which minimise the waste volume removed from a site and provide a record of the steps taken to detect, quantify and handle contaminants. Surveys results can be ‘turned around’ in less than an hour and be incorporated in continuous site operations.
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