Fukushima Unit 2 Fuel Debris Plan Further Confirmed
The details of the equipment and process for initial fuel removal at unit 2 have been further refined. Most of the needed equipment has been established and is in a testing phase. The first removal of fuel debris is now a confirmed plan.
The collapsible arm has been shown to the public as it undergoes test runs in a robotics lab. This arm will be inserted into containment through an air lock installed on the X-6 containment hatch.
Lab tests to confirm the equipment will work as intended are under way. Initial tests are being conducted at the RACE lab facility in the UK.
More refined testing and worker training with the equipment will take place at the JAEA lab in Japan. The mock up at the JAEA lab show the containment entry pipe, CRD rail and a steel mock up of the inside of the reactor pedestal. This mock up gives a good visual of the size of the structures inside the containment vessel.
A dust suppression system is being developed to prevent fuel dusts from becoming airborne during the work. This system appears to be a water spray system. There were no notes about how this may impact contaminated water and radioactive fuel dust outflow from the reactor containment.
A pair of equipment heads will be installed on the robotic arm. A brush head will remove debris while a vacuum head collects it. This choice is for the initial fuel debris sampling. Other equipment may be used when large scale fuel debris collection begins.
A plastic resin container will hold the fuel debris while a large glove box will house the container and allow workers to manipulate it before it is removed for transport. TEPCO provided this photo of the glove box unit.
The prototype shielded transit container weighs 3 tons. TEPCO notes that the container design could change before actual use.
As part of the preparation work for fuel debris removal in unit 2, the pressure inside containment will need to be changed.
TEPCO describes this as being “decompressed” to prevent fuel particle migration out of containment. The gas management system will be used to increase the flow out through the HEPA filters in an effort to lower the pressure in containment down to atmospheric levels. This will be done as a test to determine if the concept will work properly.
The test will be conducted in increments. The flow rate will be changed, then wait a day to see how this influences containment pressure and dust concentrations/radiation levels at the HEPA filters.
As more information becomes available we will update with new reports.
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