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Cosmic rays to pinpoint Fukushima cores
Middleburg, Virginia-based DSIC will design, manufacture and deliver two muon detectors that will fit into the power plant building. The detectors will be part of Toshiba's overall Fukushima Complex project to determine the location and condition of the nuclear fuel inside the plant. The value of the contract has not been disclosed.
Muons are high-energy subatomic particles that are created when cosmic rays enter Earth's upper atmosphere. These particles naturally and harmlessly strike the Earth's surface at a rate of some 10,000 muons per square meter. Muon tracking devices detect and track these particles as they pass through objects. Subtle changes in the trajectory of the muons as they penetrate materials and change in direction correlate with material density. Nuclear materials such as uranium and plutonium are very dense and are therefore relatively easy to identify. DSIC has already applied the technology in its Multi-Mode Passive Detection System, used at ports for scanning containers for radioactive materials.
The 3-D image produced by the detectors should give a clear picture of the condition and location of the fuel in the cores of the three damaged reactor at Fukushima Daiichi. This will assist Toshiba in developing a safe and effective remediation plan. Different computer models have been used by Tepco and the Japan Atomic Energy Agency to analyse the positions of the Fukushima Daiichi cores, coming to the same conclusion for unit 1. Both models predict that all 77 tonnes of the fuel from unit 1 melted and passed from the reactor vessel to the drywell area immediately below. At units 2 and 3 the models differed but together indicated that 30-40% of their 107-tonne cores remain in the vessels, the rest in the drywell.
...snip...
LANL chief technology officer Duncan McBranch said that its technology "will allow plant operators to establish the condition of reactor-core material without the need to actually get inside." He added, "Invasive techniques such as video endoscopy or introduction of robots run the risk of releasing radiation. Furthermore, those techniques at best offer a partial view of material location. Muon tomography will enable plant operators to see the location of the nuclear material inside, determine its condition, and provide critical insight that can inform the design of a safer and faster cleanup."
http://www.world-nuclear-news.org/RS-Cosmic-rays-to-pinpoint-Fukushima-cores-1108144.html
Muons are high-energy subatomic particles that are created when cosmic rays enter Earth's upper atmosphere. These particles naturally and harmlessly strike the Earth's surface at a rate of some 10,000 muons per square meter. Muon tracking devices detect and track these particles as they pass through objects. Subtle changes in the trajectory of the muons as they penetrate materials and change in direction correlate with material density. Nuclear materials such as uranium and plutonium are very dense and are therefore relatively easy to identify. DSIC has already applied the technology in its Multi-Mode Passive Detection System, used at ports for scanning containers for radioactive materials.
The 3-D image produced by the detectors should give a clear picture of the condition and location of the fuel in the cores of the three damaged reactor at Fukushima Daiichi. This will assist Toshiba in developing a safe and effective remediation plan. Different computer models have been used by Tepco and the Japan Atomic Energy Agency to analyse the positions of the Fukushima Daiichi cores, coming to the same conclusion for unit 1. Both models predict that all 77 tonnes of the fuel from unit 1 melted and passed from the reactor vessel to the drywell area immediately below. At units 2 and 3 the models differed but together indicated that 30-40% of their 107-tonne cores remain in the vessels, the rest in the drywell.
...snip...
LANL chief technology officer Duncan McBranch said that its technology "will allow plant operators to establish the condition of reactor-core material without the need to actually get inside." He added, "Invasive techniques such as video endoscopy or introduction of robots run the risk of releasing radiation. Furthermore, those techniques at best offer a partial view of material location. Muon tomography will enable plant operators to see the location of the nuclear material inside, determine its condition, and provide critical insight that can inform the design of a safer and faster cleanup."
http://www.world-nuclear-news.org/RS-Cosmic-rays-to-pinpoint-Fukushima-cores-1108144.html
At units 2 and 3 the models differed but together indicated that 30-40% of their 107-tonne cores remain in the vessels, the rest in the drywell.
A recent change to data feeding one model implied that most/all of unit 3's core is out of the RPV.