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

Abstracts Session 37
4) ENVIRONMENTAL REMEDIATION AND USING A NEW SORTING AND FREE RELEASE SYSTEM
FOR CONTAMINATED SOIL AT NPP A1 SITE, SLOVAKIA - 16020
Ondrej Slavik, Miroslav Baca, Alojz Slaninka, VUJE, a.s. (Slovakia);
Stanislav Janecka, Camberra Packard (Slovakia); Ján Sirota, JAVYS, a.s. (Slovakia)
Environmental remediation at NPP A1 site is even presently a continual process of removing the contamination from the
ground or auxuliary objects within the NPP A-1 site with accidentally shut down reactor. This paper mainly deal with monitoring,
sorting out and disposal of large volumes of removed contaminated soil stored temporarily until now at the site which is necessary
for enhancement of environmental radiation situation at the site. It was also one of the topic of the Decommissioning Project of
NPP A1, Slovakia, - Phase No I, lasted from 1999 to 2008. Within the project, attention was paid to development of technical tools
for handling with and monitoring of large volume of contaminated soil, as well. Besides short description of contaminated lands at
the site, sources of their contamination and to date known inventory, details of a pilot contaminated soil sorting facility developed
and tested recently within the Decommissioning project will be described and discussed in the papper. <strong>The</strong> paper topics include
description of and uncertainty analysis results for the pilot soil sorting system based on the Canberra-Packard pilot conveyer belt
monitor with a pair of 1.5 inch LaBr scintilation detectors and integrated electronic belt scale. In addition experiences learned during
the metrological testing and operational trial will be summarised. MDA for Cs-137 of this system is 140 Bq/kg for 30 kg and
50 Bq/kg for 300 kg parts of soil at 500 Bq/kg of 40K and 0.15 mikroGy/h.
5) THE USE OF RADIOLOGICAL CHARACTERISATION IN SUPPORT OF THE DESIGN AND BUILD
OF A NEW FACILITY IN AN AREA OF ELEVATED DOSE RATE - 16009
Karl Hughes, David Thornley, VT Nuclear Services Ltd (UK);Czeslaw Pienkowski, Sellafield Ltd. (UK)
A new building, a maintenance facility, is to be constructed in the separation area of the Sellafield Site. Sellafield is a complex
and busy nuclear facility covering about 2 square miles in the north-west of the United Kingdom. <strong>The</strong> facility, which is to provide
necessary storage and maintenance functionality to support bulk waste retrievals from legacy silos, is being built in close proximity
to spent fuel storage ponds, intermediate level legacy waste stores and a pipebridge carrying active materials. In addition, the
site is adjacent to a main pedestrian and vehicle thoroughfare and a railway line used for the regular transfer of nuclear materials.
<strong>The</strong> facility itself is to be built on the site of a recently demolished active facility.
<strong>The</strong> ambient gamma dose rates in the construction area have been measured to be typically 5 to 50 microSv/hr. Although there
are known specific sources of dose rate close to the construction site, the relative contributions of each within the envelope of the
new facility are unknown.
This paper describes how a series of gamma dose rate measurements, gamma spectroscopy measurements and gamma-ray
imaging surveys, using RadScan® 800, have been used to better understand the origins of the dose rates at a number of key locations
within the area
6) THE APPLICATION OF ADDITIONAL, OFF-LINE, ANALYSIS TECHNIQUES TO PCM MONIT
OR RESULTS TO AID THE EFFICIENT AND COST EFFECTIVE REPACKAGING OF
LEGACY PCM WASTES CONTAINING PLUTONIUM FLUORIDE - 16034
David Thornley, Kareena McCrindle, Stephen Rayner, Jonathan Sharpe, VT Nuclear Services (UK);
Czeslaw Pienkowski, Carl Phillips, Sellafield Ltd (UK)
<strong>The</strong>re are a small number of legacy, orphan waste, PCM (Plutonium Contaminated Material) drums at Sellafield Site containing
calcium metal potentially contaminated by plutonium (Pu), some of which may be in the form of plutonium fluoride (PuF4).
<strong>The</strong>se drums were measured on a TRU-D® PCM Drum Monitor to give a Nuclear Safety value for the Pu mass based on Neutron
Coincidence Counting (NCC) and the Pu isotopic composition measured for each drum using a germanium detector based High
Resolution Gamma Spectrometry system.
In some circumstances the presence of Pu in the form of PuF4 can cause a significant overestimate of the measured Pu mass.
This is as a result of alphas emitted by the spontaneous decay of Pu isotopes interacting with light elements such as fluorine, resulting
in the emission of random(alpha, n) neutrons. <strong>The</strong> potential overestimate may be very large for total neutron counting based
systems if the presence of PuF4 is not accounted for in the system calibration. However, significant quantities of PuF4 may also
result in overestimates for NCC systems due to potentially large statistical uncertainties in the measurement results caused by accidental
coincidences involving the random (alpha,n) neutrons. <strong>The</strong>refore in some circumstances, less pessimistic measurements may
be obtained from the total neutron count, corrected using the measured PuF4 ratio.
7) THE RADIOACTIVITY DEPTH ANALYSIS TOOL (RADPAT) - 16144
Alan Shippen, Malcolm Joyce, Lancaster University (UK)
<strong>The</strong> Radioactive Depth Analysis Tool (RADPAT) is a PhD bursary project currently being undertaken at Lancaster University
in the UK. <strong>The</strong> RADPAT project involves the development of nuclear instrumentation capable of ascertaining depth of radioactive
contamination within legacy plant materials such as concrete. This paper evaluates the merits of two types of detector; sodium
iodide (NaI(Tl)) and cadmium zinc telluride (CZT), both of which have been identified as possible solutions for the final RADPAT
detector. A bespoke concrete phantom has been developed to allow a set depth of simulated contamination to be obtained with a
low measurement error within a concrete analogue: silica sand. Utilising this phantom, in combination with the selected detectors,
a set of measurements have been obtained varied with increasing depth of caesium-137 contamination. By comparing the relative
attenuation of the x-ray and g-ray photopeaks from the data-set to that suggested by a differential attenuation law, a set of model
parameters can be obtained. This model, once calibrated, describes the contact depth of contamination with the relative intensity of
the peaks in a measured spectrum with a high degree of accuracy. Thus, this technique allows for a set of measurements across the
surface of a given material to obtain the inherent distribution of the depth of caesium-137 contamination. This paper is primarily
interested in the ability of each detector type to derive the attenuation model, paying particular attention to the associated statisti-
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