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NDSL
has achieved a series of successes with innovative solutions.
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Commercial incineration of alkali
metals rather than water reaction.
This has been used for the disposal of sodium coupons and
bulk sodium from the Janetstown facility near Dounreay. Very substantial cost-savings
were achieved over alternative techniques, such as destruction through reaction
with water. Incineration at an HTI is likely to be used again for the disposal
of sodium and sodium-potassium alloys from several other sources, such as redundant
alkali metals from the Joint Research Centre of the EU Commission at Ispra. For
further information please see Sodium
Coupons. |
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Deployment of commercial ROVs (Brokks) on a range of
decommissioning projects.
NDSL suggested the use for Brokks for decommissioning the D8550 Plutonium Criticality
Facility and the D1217 PIE Cells; Brokks have not been used at Dounreay before
and we are responsible for their introduction to site. Brokks are widely used
elsewhere in the nuclear industry and are small, commercially available, remotely
operated demolition machines that can be equipped with a variety of tooling.
The one for D85550 is for wall demolition and also for the steel criticality
cell size reduction. In D1217 a Brokk will be used to cut up the benches in cells
with high contamination and radiation levels. |
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Design
of simple and cheap survey device for the Dounreay Materials
Test Reactor
At DMTR, an internal survey was necessary because there was insufficient information
regarding the internal state of the reactor vessel. NDSL suggested a probe and
a simple camera with lights on the end of drain rods inserted via the heavy water
pipework into the reactor. For less than £10K NDSL gathered both good pictures
of the reactor tank and also obtained excellent radiological dose data. |
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Tallow - a fuel particle recovery system
A survey of the D9814 pond within Building D1251 revealed a number
of radiation hot-spots on the pond floor that were thought
to be composed of small particles of irradiated fuel. These
needed to be removed before decommissioning could proceed,
and NDSL was asked to carry out an option study, produce the
associated Safety and Environment documentation, and propose
a detailed methodology. No doubt a high-tech, expensive and
complicated mechanical solution to the problem could have been
found but by borrowing the technology from sailing ships with
the lead line a cheap but effective solution was found: trials
using a piece of tallow showed that this material will satisfactorily
capture swarf, sand and stainless steel balls up to 25 millimetres
in size from the bottom of a tank full of water. Preparations
for full implementation are now underway.
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Use
of ROVs for survey in D1204 and DFR.
At Dounreay, pictures from thereactor vault were required; NDSL proposed
to lower an ROV with camera and gamma probe down an aperture from the
charge floor to the walkway under the NaK filled coolant circuits. Excellent
photos and useful radiological data were obtained. The photograph below
shows a more sophisticated ROV prepared for a D1204 survey and fitted
with two cameras, a gamma probe, a laser distance measurer and a highly
dextrous arm.
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Particle
discrimination trial.
NDSL was asked to find a way of discriminating between particles and naturally
occurring radiation on the seabed. We decided that it was easier to move the
source and keep the probe static. We used three cattle troughs with different
depths of sand to simulate the depth of the particle in the seabed and had an
electric train carrying natural and man made sources under the tanks. By placing
different instruments above the sand, which could have a few inches of water
over it, we could mock up the right scenario, and carry out an easily repeatable
trial. |
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© NDSL 2006. All rights reserved.
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