The 12th International Conference on Environmental ... - Events

Abstracts Session 31
5) INTERDIGITATED ELECTRODE ARRAY BASED SENSORS FOR MONITORING OF CAESIUM - 16123
Ian D Nickson, John Tyndall Institute for Nuclear Research (UK); Colin Boxall, Lancaster University (UK);
G. Garnham,National Nuclear Laboratory (UK); Simon. N Port, DSTL (UK)
<strong>The</strong> requirement for on-line and in-situ monitoring of analytes in process and effluent streams and in ground waters has become
increasingly more important in recent years. We therefore describe the development of the transduction element for a fully automated
online instrument for the detection of caesium. <strong>The</strong> sensor layer for this instrument employs an Ion Selective Conductimetric
microsensor (ISCOM) as the detector. This is based upon a plasticized polymeric membrane incorporating a selective ionophore,
overlaying two interdigitated microelectrode arrays. A direct relationship has been observed between the bulk conductance (as
determined by the microelectrodes) of the ionophore loaded membrane and the concentration of the primary ions in solution.
Caesium selective ISCOMs were prepared using a ion selective membrane containing the commercially available ionophore
Calix[6]arene-hexaacetic acid hexaethyl ester, polyvinylchloride (PVC) and plasticiser Nitrophenylether (NPOE). Methods of ion
selective membrane deposition have been investigated in order to obtain a maximal response. <strong>The</strong> relative levels of membrane components
have also been varied in order to further enhance the ISCOM reponse. We also present preliminary data concerning the
caesium selectivity with respect to a range of possible interferents, including rubidium.
6) CONE PENENTRATION TESTING OF RADIOLOGICALLY CONTAMINATED BURIAL TRENCHES - 16086
Gareth Walker, Matt Lennard, Jeremy Lightfoot, Golder Associates (UK); Nick Jefferies, Serco Assurance (UK)
Golder Associates (UK) Ltd, in partnership with Serco Assurance (Serco), undertook targeted cone penetration testing (CPT)
of a series of six parallel on-site burial trenches on a nuclear licensed site in the UK. <strong>The</strong> form and concentration of radioactive and
chemical material within the trenches is unknown. CPT was used to confirm the location of the bund walls and to characterise the
material within the trenches <strong>The</strong> CPT technique involves hydraulically pushing rods fitted with specialist characterisation “cones”
into the ground. CPT generates no solid or liquid waste, and allowed rapid investigation of the trenches and bunds while ensuring
exposure of radiation and contamination to workers was kept to a minimum, or removed in entirety. As a result of the unknown
nature of radiological contamination within the trenches and the potential of introducing contamination into the inside of the CPT
truck, a purpose-built extraction rig was constructed to withdraw the CPT equipment from the ground. Extraction of the equipment
assumed airborne radioactive contamination was a potential hazard. <strong>The</strong> CPT locations selected for the investigation were based on
non-intrusive geophysical survey work and a radiation survey, which identified the approximate location of the trenches, anomalies
within the material (e.g. metallic objects), and radiation hotspots. <strong>The</strong> results of the geophysical surveys were overlaid with the
original as-built drawings of the trenches. During the investigation the following investigation cones were deployed: •
Resistance/friction cone, which determines geology through measurement of the friction on the sleeve of the cone and resistance
on the tip of the cone; this was used to investigate the geology of the bunds. • Total gamma cone, which was used to obtain total
gamma radiation results (in counts per second); • Groundwater sampler (BAT SamplerTM), which was used to obtain a water sample
from beneath the trenches; • Video cone, which was used to obtain a visual recording of the material within the trenches; and •
Conductivity cone, which was used to investigate the presence of and depth to bodies of water below ground level (e.g. perched
water, regional groundwater).
7) THE ADVANCED PEGASUS OVERLAND RADIATION DETECTION SYSTEM - 16321
Jeffrey Lively, Alejandro Lopez, Michael Marcial, MACTEC (USA); Mark Liddiard, Joe Toole, WorleyParsons (UK)
A variety of technical challenges are presented when one wishes to make radiological measurements over large areas of land.
Aside from the physical challenges posed by the land surface itself, the radiological composition, the physical properties, and the
nature of deposition of the contaminant often pose formidable scientific challenges. No one system or approach can be ideally suited
to every circumstance. One of the most formidable circumstances one could face in open land radiological surveys is the challenge
of locating discrete particle contaminants that may be widely distributed over large land areas. <strong>The</strong> measurement challenge
is akin to “hunting for the needle in a haystack.” While overland surveys have been performed by various means for many years,
the methods employed are often ineffective or utterly inadequate to address the confident detection of “super heterogeneous” contaminants
at reasonable activity thresholds.
At least three areas of inter-tidal contamination by particulate radioactive contamination have been identified in the UK. <strong>The</strong>se
cover substantial areas which can only be effectively monitored by vehicle based systems and are subject to rapid changes caused
by weather and tidal cycles. Of these contaminated sites, the most well known is the beaches that lie in proximity to the Dounreay
plant in northern Scotland. Other beach environments adjacent to the Sellafield plant and a former Royal Air Force (RAF) airfield
in eastern Scotland are also impacted with discrete radioactive particle contamination.
8) THE EFFECT OF HIGH-SCATTER SHIELDING GEOMETRIES IN VALIDATING
THE DOSE INFERRED BY N-VISAGE(TM) - 16130
Jamie Adams, Lancaster University (UK); Matthew Mellor, React Engineering Ltd. (UK);
Malcolm Joyce, Lancaster University (UK)
<strong>The</strong> aim of this paper is to further validate the physical capability of N-Visage” under more challenging shielding geometries,
when the number of mean free paths is greater than one. N-Visage” is a recently established technique developed at REACT Engineering
Ltd. <strong>The</strong> software locates radionuclide sources and contours radiation magnitude. <strong>The</strong> N-Visage” software uses a geometric
computer model combined with measured spectra. <strong>The</strong> software is able to estimate source locations through shielding materials
by using mass attenuation coefficients to calculate the number of unscattered gamma photons arriving at the detector, and buildup
factors to estimate scatter contribution to dose rate. <strong>The</strong> experiments described in this paper were carried out in a high-scatter
environment using cobalt-60 and caesium-137 sources, these two sources are the primary sources of radiological contamination
found in the nuclear industry. It is hoped that this will further assist in the identification, characterisation and removal of buried
radiologically contaminated waste.
97