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?
TOKYO (AP) — Tokyo Electric Power Company Holdings’ former chairperson, who led the emergency response after a meltdown at its Fukushima Daiichi nuclear plant and was accused of being responsible for failing to prevent the disaster as top management, has died, with his trials still pending. He was 84.
Tsunehisa Katsumata died on Oct. 21, TEPCO said Thursday, without providing further details including the cause of his death.
Katsumata was TEPCO chair when Fukushima Daiichi was hit by a magnitude 9.0 earthquake and tsunami in March 2011 and suffered triple meltdowns. He led the emergency response after the company’s then-president stepped down due to health problems and served until mid-2012.
He later became one of the defendants in high-profile criminal and civil lawsuits seeking TEPCO management’s responsibility over their alleged failure to anticipate the massive quake and tsunami and to take preventive measures.
A tsunami with waves up to 10 m (33 ft) high struck the coast of Sagami Bay, Bōsō Peninsula, Izu Islands, and the east coast of Izu Peninsula within minutes. The tsunami caused many deaths, including about 100 people along Yui-ga-hama Beach in Kamakura and an estimated 50 people on the Enoshima causeway. Over 570,000 homes were destroyed, leaving an estimated 1.9 million homeless.
The 1896 Sanriku earthquake (明治三陸地震, Meiji Sanriku Jishin) was one of the most destructive seismic events in Japanese history. The 8.5 magnitude earthquake occurred at 19:32 (local time) on June 15, 1896, approximately 166 kilometres (103 mi) off the coast of Iwate Prefecture, Honshu. It resulted in two tsunami waves which destroyed about 9,000 homes and caused at least 22,000 deaths. The waves reached a then-record height of 38.2 metres (125 ft); this would remain the highest on record until waves from the 2011 Tōhoku earthquake exceeded that height by more than 2 metres (6 ft 7 in).
The extendable robot, nicknamed Telesco, first began its mission August with a plan for a two-week round trip, after previous missions had been delayed since 2021. But progress was suspended twice due to mishaps — the first involving an assembly error that took nearly three weeks to fix, and the second a camera failure.
On Oct. 30, it clipped a sample weighting less than 3 grams (.010.1 ounces) from the surface of a mound of melted fuel debris sitting on the bottom of the primary containment vessel of the Unit 2 reactor, TEPCO said.
Three days later, the robot returned to an enclosed container, as workers in full hazmat gear slowly pulled it out.
On Thursday, the gravel, whose radioactivity earlier this week recorded far below the upper limit set for its environmental and health safety, was placed into a safe container for removal out of the compartment.
Something isn't right here.3 grams (.01 ounces)
Fixed. It should be 0.1 oz.gmax137 said:Something isn't right here.
Fukushima Daiichi Unit 2 was a BWR/4 type with a gross electrical power generation of 784 MWe gross, 760 MWe net (so about 24 MWe used by the plant). Units 2, 3, 4 and 5 were much the same design, and apparently not uprated.Sotan said:I hope that little piece of debris is not being considered representative for the whole deposit at the bottom of the PCV - what was it, 200 tons plus?