UPDATE: The process of removing the fuel rods at the Fukushima nuclear plant in Japan has so far been successful. The first of the 22 rod assemblies planned for removal (which contain unspent fuel) have been removed. See this Bloomberg News article for more. Also in the same article, a description of what “criticality” would mean for Reactor 4, if the spent rods go critical.
It’s difficult to get consistent news out of Japan about the Fukushima nuclear plant, but it appears, after a rumored delay on Friday, work at Reactor 4 is now under way.
There are actually several short items in this post, starting with the headline. The other items relate to rods previously damaged — damage which was not previously announced by TEPCO, the risk presented by the debris in the Reactor 4 spent fuel pool, and the risk of a “criticality” or nuclear reaction (it’s not zero).
(All links via ENENEWS.com; if you have a better source for Fukushima news, please let me know in the comments.)
Work on Removing the Fuel Rods has Started
NHK World (my emphasis, paragraphing and notes throughout):
The operator of the Fukushima Daiichi nuclear power plant [TEPCO] has begun removing nuclear fuel from a storage pool at a damaged reactor building. Workers placed a special fuel transport container ["cask"] in the storage pool of the Number 4 reactor building.
The pool holds 1,533 units of nuclear fuel, of which 1,331 are highly radioactive spent fuel. The rest  are unused ["unspent" or "reactor-ready"].
At around 3PM on Monday, the workers started to hoist the unused ["unspent"] fuel units into the steel container ["cask"], which can store 22 units of fuel. The utility decided to remove these units first as they do not release high levels of radiation and heat. A TEPCO official said that the first fuel unit was moved into the container by 4PM, and that the workers had encountered no problems.
The first 22 units will be transferred into the container through Monday night.
There is some variance in the reports of the count of rods, so I added some numbers above. Considering the source (NHK), I will take these counts as authoritative until shown otherwise.
To see what is meant by “steel container” or “cask,” see the first video in this reference post. It shows the idealized process in a nice TEPCO-produced animation. The steel container, or cask, holding 22 units is taken to the common spent fuel pool, about 50 meters away, to be added to the more than 6,000 fuel rods already there.
Note: Fifty meters is not far — half a football field. The site has been criticized for being too compact, with reactors and the common spent fuel pool too close together. Getting the fuel rods out of Reactor 4 is a very high priority, given the condition of the building. But taking care of the common fuel pool is also important.
The article also notes that:
▪ Debris in the pool could complicate the procedure, but doesn’t say how (see below for more).
▪ The removal from Reactor 4 could take through the end of next year.
▪ The entire decommissioning process will take up to 40 years.
NHK is Japan’s public broadcasting network. There’s a video at the news site, which I can’t embed, but you can watch it there. It’s worth viewing, especially at 2:40 and following. If you do though, listen carefully. All of the calming is sourced to “officials” — fair enough — but then presented uncontested.
And in other Fuku news …
Eighty Fuel Rods in Four Reactors Were Damaged Before the 2011 Earthquake
There are up to 80 damaged fuel rods in Reactors 1 through 4, three of them in Reactor 4, where current work has started. RT.com:
Three of the spent fuel assemblies that will be pulled from the Fukushima nuclear plant during a year-long operation were damaged before the 2011 earthquake and tsunami crippled the Japanese facility.
Tokyo Electric Power Co. (TEPCO), which operates the plant, said the damaged assemblies – 4.5 meter high racks with 50 to 70 rods of highly irradiated used fuel – won’t be lifted from the plant’s Reactor No. 4 when a large steel chamber, or cask, is employed to move over 1,500 assemblies to safe storage, Reuters reports.
In an 11-page information sheet released in August, TEPCO said one of the assemblies was even damaged as long ago as 1982, when it was bent out of shape during a transfer. … The damaged racks were first reported by a Fukushima area newspaper on Wednesday, as TEPCO is preparing to decommission the plant and remove the spent fuel assemblies from Reactor No. 4.
I believe this is references that local Fukushima newspaper report. Note the additional information about damaged rods in the other three reactors. EX-SKF:
TEPCO Admits Total 80 Spent Fuel Assemblies Had Damages Before the Nuclear Accident, 70 of Them in Reactor 1 Spent Fuel Pool
Move over, three fuel assemblies with damaged/deformed fuel rods inside in the Reactor 4 Spent Fuel Pool! You’re nothing.
According to Kahoku Shinpo, a Fukushima local paper, TEPCO admitted on November 15, 2013 that there are 70 fuel assemblies with damaged fuel rods in the Reactor 1 Spent Fuel Pool, located on the operating floor (top floor) of the reactor building whose air radiation levels are measured in millisievert/hour and sievert/hour (first floor). There are also three such fuel assemblies in the Reactor 2 SFP, and four of them in the Reactor 3 SFP.
Total 80 spent fuel assemblies in the SFPs in Reactors 1 – 4 are damaged. The damages had been there long before the March 11, 2011 accident, and TEPCO claims it properly notified the national government as they discovered the damages. But the company has come clean in public only now.
About that “debris” in Reactor 4 …
Has Debris Damaged the Rods in Reactor 4?
There’s clearly debris in the Reactor 4 spent fuel pool. How much, and what kind is the question. First, watch that video in the NHK news report at 2:40. The engineer is concerned that “there could be fragments of debris stuck between the [rod] assemblies and their holding racks.” Seems likely, given that debris comes in many sizes.
The article quoted just above says this:
In 2010, TEPCO said that another two spent fuel racks in the reactor’s cooling pool possibly contained wire trapped in them. Rods in the assemblies have small cracks and are leaking low-level radioactive gases, TEPCO spokesman Yoshikazu Nagai told Reuters on Thursday.
The AP is concerned that not only the rods (here called “assemblies”) but the handles at the top used to lift them could have been damaged during the disaster:
Q: What are the potential risks?
A: Fuel assemblies or the rods inside them may be damaged or break open if dropped or shaken violently. They may not come out of the rack smoothly. The fuel assemblies and their handles may have been damaged when big pieces of debris fell on them during explosions early in the crisis. A crane may drop a cask on the ground. Some fuel rods [meaning the zirconium alloy cladding] may be corroded because seawater was used to keep them cool during the emergency.
As a safety measure, the crane is equipped with a system that will stop pulling on the assemblies if it encounters a certain level of resistance to prevent any rods from getting damaged or broken. An underwater camera will monitor the work, and an underwater vacuum cleaner will collect small debris. Tokyo Electric Power Co., the plant operator, removed two unused fuel assemblies last year, and an examination suggests the assemblies have generally remained intact.
The rest of the AP article has good information. Do read if you’re following this story.
What’s the Risk of a Nuclear Reaction?
About that, no one knows, but it’s not zero. The WSJ:
Each 550-lb [fuel rod] assembly unit holds 60 to 74 of the metal-clad [thin] rods filled with fuel pellets that power nuclear reactors. The units are kept in a pool of cool water to prevent exposure to air, which can cause the radioactive material to heat up and could trigger a sustained nuclear reaction.
A “sustained nuclear reaction” is also called a “criticality,” though not necessarily of the atomic bomb type. There are many kinds of criticality. What happens inside a nuclear reactor is a controlled criticality, the control being the control rods that are moved into and out of the reaction to absorb more or less atomic particles released.
[Update: The shape of that criticality would be similar to the meltdowns at Reactors 1, 2 and 3, according to Bloomberg News.]
The problem with this situation, according to Arnie Gundersen, is that there are no control rods in any of the spent fuel pools anywhere on the site, including in Reactor 4:
Arnie Gunderson, a veteran US nuclear engineer and director of Fairewinds Energy Education, told Reuters that ”they are going to have difficulty in removing a significant number of the rods,” especially given their close proximity to each other, which risks breakage and the release of radiation.
Gundersen told Reuters of an incredibly dangerous “criticality” that would result if a chain reaction takes place at any point, if the rods break or even so much as collide with each other in the wrong way. The resulting radiation is too great for the cooling pool to absorb – it simply has not been designed to do so.
“The problem with a fuel pool criticality is that you can’t stop it. There are no control rods to control it,”Gundsersen said. “The spent fuel pool cooling system is designed only to remove decay heat, not heat from an ongoing nuclear reaction.”
Agence France-Presse has the same concern, as do others.
The WSJ piece above linked editorially calls the article with the Gundersen quote “hyperventilation.” Feel free to decide for yourself.
But as you do, ask first — How much billionaire money is at stake in the nuclear industry, and would the Journal be sensitive and protective of that? I do mean for you to decide for yourself; this isn’t an indictment of the Journal. But the question has to be asked. Part of the damage of Fukushima is to the billion-dollar nuclear industry in the U.S.
You may want to go back to this reference post and watch that TEPCO animation again, just to get these pictures in your head. The thin rods are called “rods,” and the square packages are sometimes also called “rods” and sometimes “assemblies.” The thin rods are clad in zirconium alloy, and it appears the assemblies are as well. I haven’t discussed zirconium in this space, but Gundersen has, in the second video here. It’s highly ignitable; it’s the stuff that flares bright in flash cubes. (See the zirconium comment above.)
And that’s what we know as of this writing. Please stay tuned.