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

Abstracts Session 25-26
During the decommissioning planning period, the scenarios covering possible routes of materials release into the environment
and radioactive waste disposal, should be discussed and evaluated. Unconditional and conditional release to the environment, longterm
storage at the nuclear site, near surface or deep geological disposal and relevant material management techniques for achieving
the final status should be taken into account in the analysed scenarios. At the level of the final decommissioning plan, it is
desired to have the waste management scenario optimised for local specific facility conditions taking into account a national decommissioning
background.
<strong>The</strong> analytical methodology for decommissioning waste management scenarios evaluation, presented in the paper, is based on
the materials and radioactivity flow modelling which starts from waste generation activities like pre-dismantling decontamination,
selected methods of dismantling, waste treatment and conditioning, up to materials release or conditioned radioactive waste disposal.
Necessary input data for scenarios, e.g. nuclear installation inventory database (physical and radiological data), waste processing
technologies parameters or material release and waste disposal limits, has to be considered. <strong>The</strong> analytical methodology principles
are implemented into the standardised decommissioning parameters calculation code OMEGA, developed in the DECOM
company. In the paper the examples of the methodology for the scenarios optimization are presented and discussed.
3) CHARACTERISATION OF RACTOR GRAPHITE TO INFORM STRATEGIES FOR
DISPOSAL OF REACTOR DECOMMISSIONING WASTE - 16389
Andrew Hetherington, Phil Davies, NDA (UK)
Graphite has been used extensively as a neutron moderator and reflector in reactors in the UK since the 1950s. <strong>The</strong> UK nuclear
decommissioning programme will result in some 90,000 tonnes of waste graphite being removed. A number of other countries also
have graphite reactors scheduled for decommissioning, but UK has the largest graphite waste liability of any.
<strong>The</strong> current UK baseline strategy, which is to package graphite waste and then consign it to geological disposal is considered
feasible, but it has not yet been shown to represent the optimum solution in terms of cost, safety and protection of the environment.
<strong>The</strong> NDA is currently engaged in investigating alternative solutions for reactor graphite. A review of worldwide developments has
enabled a decision chart to be compiled for managing graphite waste showing, at a high level, the strategic options and processes
needed to take the graphite from a shut?down reactor, to the point where it is finally disposed of.
Physical characterisation is needed to provide a detailed radionuclide inventory for the graphite to supplement theoretical calculations.
Such an inventory, together with information about the physical and chemical characteristics of the material is a prerequisite
for making decisions about its interim management as well as final disposition. <strong>The</strong>re is a need to progress understanding of
uncertainties in the activity of the long?lived radionuclides in graphite and of particular significance is precise characterisation in
relation to Carbon?14 and Chlorine?36. Using information about the impurity levels in graphite at the various sites along with irradiation
history, modelling tools will be used to assess the profile of key radionuclides within the graphite with a view to optimising
the disposal route.
4) DEMONSTRATION OF UK ILW TREATMENT BY GEOMELT VITRIFICATION - 16105
Keith Witwer, Kevin Finucane, Eric Dysland, AMEC, GeoMelt Division (USA)
Experiments for airborne dispersion ratio of radionuclides during plasma arc cutting were carried out in a contamination control
enclosure, using stored radioactive metal wastes arising from the decommissioning activities of Japan Power Demonstration
Reactor, which was a boiling water type reactor. Neutron induced-activated piping and surface contaminated piping were segmented
into pieces using air plasma arc cutting, using a current power was 100A. In addition, similar experiments for contaminated piping
of the Advanced <strong>The</strong>rmal Reactor, Fugen were carried out.
As a result, dispersion ratios for activated piping were 0.2 to 0.7% of Co-60 and 0.4% of Ni-63 under the condition with a covered
cap on the head. And those for surface contaminated piping were from 18 to 23%. In addition, those for vertically segmented
piping which simulated flat plate were from 34 to 43%. <strong>The</strong>re was no difference of dispersion ratios between stainless steel and
carbon steel base materials. All values obtained were smaller than the Handbook recommended value of 70% for contaminated
materials.
Filtering collection efficiencies of the coarse dust filter were approximately 40% for activated piping and approximately 55 to
80 % for surface contaminated piping. However there was no effect for collection of aerosols smaller than 1μm.
Size distribution analysis indicated a greater concentration of radionuclides in particles smaller than 0.1μm when compared
with larger particles. In addition, there was a tendency that the Ni-63 was concentrated to the particles smaller than 0.3μm compared
with the Co-60.
<strong>The</strong> results support data obtained in the previous studies using non-radioactive materials.
SESSION 26 - D&D UPDATE AND MANAGEMENT ISSUES
1) RENEWING THE FOCUS ON DECOMMISSIONING: BRINGING A NEW
MANAGEMENT PERSPECTIVE TO SELLAFIELD - 16243
Russ A Mellor, Sellafield Ltd (UK)
Sellafield site, on the West Coast of Cumbria, has recently emerged from a long competition process with new Parent Body
Organisation Nuclear Management Partners taking the helm of the UK nuclear industry flagship.
Bringing together three major companies, URS Washington Division, AREVA and AMEC, all leaders in their fields, NMP
bring a new perspective to the way the Sellafield site is managed, using an approach that focuses on three Ps People, Partnership
and Performance.
Following a restructure of the company, one of the key drivers for future lifetime plans is that of handling the legacy waste and
a major reorganisation of the site led to the evolvement of two distinct arms, Projects and Support. Sitting within Projects, and
evolved from the Nuclear Decommissioning and Major Projects Group, the Clean-up directorate look after four key areas; Contaminated
land, Legacy Ponds & Silos, Windscale and Decommissioning & Waste.
<strong>The</strong> paper will look in more depth at
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