Yes, primarily, and their decay products, e.g., Ba and Y, and a little Rb, precursor to Sr. They will be distributed at the surface and into the concrete. It's what accumulates at the surface, and it's not so much beta and decay gammas.Vanadium 50 said:cesium and strontium?
If you can just leave it alone then could be fine, but they are still supposed to work there for some time. And to keep the radiation levels of such working environment low enough to keep limits is troublesome. It's no longer an emergency, so limits are strict...Vanadium 50 said:If so, isn't that a good thing?
On 19 August, Tepco announced that it planned to remove a few grams of melted fuel debris from unit 2 on August 22. The operation was expected to last about two weeks using a telescopic device equipped with a gripper tool. The device can extend up to 22 metres and access the debris through a penetration point in the primary containment vessel (PCV). The removal technique, which is being used for the first time in unit 2, will then be gradually extended to unit 3, where a large-scale recovery is expected in the early 2030s.
"Unit 2 was selected as the first block for the recovery of the fuel debris because we take into account the situation in terms of safety, reliability, speed and progress in the removal of the used fuel elements," Tepco said.
Workers at the plant today began inserting the guide pipe of the telescopic debris retrieval device into the PCV penetration point. The guide pipe was inserted to the front of the isolation valve and the first of five 1.5-metre-long push pipes to be used was prepared to be connected. The pipes are used to push the device inside the PCV and pull it back out when the operation is completed.
However, it was then noticed during the final checking process that the order of the first push pipe was different from the planned order. The workers had in fact prepared the second push pipe for insertion instead of the first one. It was confirmed the push pipe that should have been in the first position was in the fourth position. The incorrect order of the pipes meant they could not be connected correctly.
. . .
TOKYO (AP) — An extendable robot began on Tuesday a two-week mission to retrieve the first sample of melted fuel debris from inside one of three damaged reactors at the Fukushima Daiichi nuclear power plant.
Highly radioactive fuel and other materials in the reactors melted when a massive earthquake and tsunami in 2011 damaged the plant’s cooling systems.
The plant’s operator, Tokyo Electric Power Company Holdings, has previously used small robots to examine the inside of the reactors, but this is the first time for it to collect a sample of the melted debris in what will mark the start of the most challenging part of the plant’s decadeslong decommissioning.
The mission was initially scheduled to begin on Aug. 22 but was suspended when workers noticed that five 1.5-meter (5-foot) pipes to be used to push the robot into the reactor had been arranged in the wrong order, TEPCO said.
Nuclear people these days already has a tendency for OCD, and they are ...Vanadium 50 said:Any idea why they don't?
I'm curious about what information the analysis results from such a sample will provide, and how that info can be used going forward. In other words, what does TEPCO hope to find out?Astronuc said:retrieve melted fuel ... a fragment measuring less than 3 grams
I think they will need to collect multiple samples to characterize the nature of the fuel and core support structure. In a severe accident case in which the 'core' (assemblies, control elements, and core support structures) melts, then one often refers to 'corium'.gmax137 said:I'm curious about what information the analysis results from such a sample will provide, and how that info can be used going forward. In other words, what does TEPCO hope to find out?
I suspect they want to deconstruct and remove the structure and return the site as close to natural as possible. If they basically entomb the structure in concrete, they will likely be required to do some kind of monitoring indefinitely.Vanadium 50 said:These robots are very impressive, if you've ever seen one.
It seems like an easier solution would be to full the containment vessel floor to ceiling with borated high density concrete. ("blue blocks") Any idea why they don't?