What are the perils surrounding removal of nuclear fuel rods at Fukushima no.4?

Why TEPCO is Risking the Removal of Fukushima Fuel Rods. The Dangers of Uncontrolled Global Nuclear Radiation, Global Research, 24 Nov 13  By Yoichi Shimatsu After repeated delays since the summer of 2011, the Tokyo Electric Power Company has launched a high-risk operation to empty the spent-fuel pool atop Reactor 4 at the Dai-ichi (No.1) Fukushima Nuclear Power Plant.

The urgency attached to this particular site, as compared with reactors damaged in meltdowns, arises from several factors:

–         over 400 tons of nuclear material in the pool could reignite

–         the fire-damaged tank is tilting badly and may topple over sooner than later

–         collapse of the structure could trigger a chain reaction and nuclear blast, and

–         consequent radioactive releases would heavily contaminate much of the world.

The potential for disaster at the Unit 4 SFP is probably of a higher magnitude than suspected due to the presence of fresh fuel rods, which were delivered during the technical upgrade of Reactor 4 under completion at the time of the March 11, 2011 earthquake and tsunami. The details of that reactor overhaul by GE and Hitachi have yet to be disclosed by TEPCO and the Economy Ministry and continue to be treated as a national-security matter. Here, the few clues from whistleblowers will be pieced together to decipher the nature of the clandestine activity at Fukushima No.1.

Accidents happen

The delicate rod-removal procedure requires the lowering of a steel cylinder, called a transfer cask, into a corner of the pool and then using the crane to lift the 300-kilogram fuel assemblies (4..5-meter-tall bundle of fuel rods held inside a metal cage) one at a time from the vertical array of rods up and then down into the cask. The container can hold 22 assemblies for transfer to a temporary cooling unit built next to Reactor 4 before these are moved to a storage building.(1)

Lifting the 1,533 fuel bundles out of the pool is fraught with danger. If an assembly breaks away and falls, the impact could shatter other rods below, triggering an uncontrolled nuclear reaction. Compounding the threat, many rods are not intact but were fragmented into loose shards by a collapsing crane. In addition, many of the rods likely lost their protective cladding during the two fires that engulfed the spent-fuel pool on March 14 and 15, 2011.

The urgency of this transfer operation is prompted by the warping of the supporting steel frame by the twin fires that followed the March 11 quake. The pool is also tilting. If the unbalanced structure topples, the collapse would trigger nuclear reactions. A cascade of neutrons could then ignite the nearby common fuel pool for Reactors 1 through 6. The common pool contains 6,735 used assemblies.(2)

The Reactor 4 spent fuel pool contains an estimated 400 tons of uranium and plutonium oxide, compared with just 6.2 kilograms of plutonium inside Fat Man, the hydrogen bomb that obliterated Nagasaki in 1945.  (While predictions are bandied about by experts and bloggers, there exists no reliable method for calculating the potential sum or flow rate of radiation releases, measured in becquerel or sievert units, after an accident. The tonnage involved, however, indicates only that a large-scale event is likely and a cataclysm cannot be ruled out.)

More than 1,700 tons of nuclear materials are reported to be on site inside Fukushima No.1 plant. (My investigative visits into the exclusion zone indicate the existence of undocumented and illegal large-scale storage sites in the Fukushima nuclear complex of undetermined tonnage.)  By comparison Chernobyl ’s reactors contained 180 tons of fuel not all of which melted down.

Despite the looming threat to residents in Fukushima , surrounding provinces and the capital Tokyo , the office of Prime Minister Shinzo Abe along with TEPCO hews to the tradition of risk denial and blackout of vital information. No contingency plan has been issued to Fukushima residents or to the municipalities of the Tohoku and Kanto region in event of a nuclear disaster during the SFP clearance effort. A concurrent drive to impose a draconian law against whistleblowers on grounds of national security is reinforcing the cover-up of data and testimony related to nuclear power plants, including the Fukushima complex..

Fires last time

The rod-transfer operation from Unit 4 is scheduled for completion by the end of 2014. That estimate is optimistic since it does not take into account the obstruction posed by fragments of shattered fuel rods that were overheated in the two fires that swept through Unit 4 spent-fuel pool on March 13 and 15, 2011, according to NHK television news.(8) Another factor for uncertainty is the impact of the explosion that rocked the roofline of the reactor building.

….. http://www.globalresearch.ca/why-tepco-is-risking-the-removal-of-fukushima-fuel-rods-the-dangers-of-uncontrolled-global-nuclear-radiation/5359188

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