There have been many official enquiries into the Fukushima disaster (2011-03-11). The report of the IAEA Fact Finding Mission (2011-06-16) can be set aside due to conflict of interest, and that of the UK ONR (2011-09) due to inadequacy. Both were written after only brief enquiries and published within six months of the disaster. Those of the Japanese safety agency NISA (2011-08-09) and of the operator TEPCO (2012-06-20) can also be set aside due to conflicts of interest. This leaves the reports of the Cabinet Office (Hatamura Panel) (2011-12-26), the independent Kitazawa Panel (2012-02-28) and the Japanese Diet (parliamindex.htmlent) (2012-07-05). The full reports are in Japanese, with shorter summaries in English. Published within 16 months of the disaster, these have failed to determine the causes of the three reactor meltdowns and the disastrous radioactive releases.
However NHK, the leading Japanese broadcaster, waited a year or more until people were ready to talk, interviewed over 300, later 400, of those directly involved and outside experts, and collected huge amounts of data. This has enabled realistic re-enactments of the sequence of events. Among many programmes on the Fukushima disaster, NHK has produced three 'Meltdown' documentaries in English, first broadcast on 2012-01, 2012-08-18, and 2013-03-05. This last was about 24 months after the disaster.
- 2012-01. 'Meltdown: The Fukushima Nuclear Crisis Behind the Scenes'. This is referred to in the later programmes, but I could not find any video file of it on YouTube.
- 2012-08. 'The Truth Behind the Chain of Meltdowns'. The video is here. It runs for 49:56.
So that the full import can be more readily appreciated, I produced a transcript, dated 2014-01-13. I added some words [thus] as clarifications.
The main findings of this programme are:- Even after a reactor stops operating, the nuclear fuel inside continues to emit massive amounts of heat. A loss of water to cool the fuel would result in a meltdown. The dissolved [molten] nuclear fuel would penetrate the bottom of the reactor and spread into the primary containment vessel. Should the containment vessel break, vast quantities of radioactive substances would spew out. Once that happened no-one would be able to come near to the reactor. Yet to replace that boiled off by nuclear decay heat, the operators could not inject water when the reactor pressure was high.
- The Reactor Pressure Vessel (RPV) could not be de-pressurized via the SR (Safety Relief) valve due to the effect of high RPV pressure on the valve operation. [Since the maximum RPV pressure was known, this is a fundamental design fault]. In addition, under Station Blackout (SBO), there was no electric power to actuate the valve. If the SR valve remains closed, there's no way to prevent a meltdown. This happened at Reactors 1, 2, and 3.
- The RPV could not be 'vented' with the AO valve, due to lack of compressed air to actuate the valve. This was due to lack of electric power for the air compressor. If the RPV cannot be vented, decay heat will cause it to rupture and release fission products to the environment. This happened at Reactor 2.
- There was a lack of critical backup items on site, such as batteries of the correct voltage. Operators even tried using batteries taken from their own cars.
- During the Fukushima crisis, three reactors melted down in succession. The radioactive material they released has contaminated the soil. More than 160 thousand residents are still unable to return home.
- 2013-03. 'Meltdown: Oversights in the Reactor Cooling System'. The video is here. It runs for 49:23.
So that the full import can be more readily appreciated, I produced a transcript, dated 2014-01-13. I added some words [thus] as clarifications.
The main findings of this programme are:- The RCIC (Reactor Core Isolation Cooling) system for Reactor 1 cannot be activated without electric power. Although the electric status indicators were also inoperative, the Isolation Condensers were assumed to be working. The operators mistook faint steam coming from the 'pig's nose' outlets as confirming that the Isolation Condenser was working. Yet in over 40 years, this had never been tested !
- As a last-ditch method of cooling the reactors, fire engines were used to inject water into the reactor buildings. However, due to a pump lacking power for operation, much of it leaked via an unexpected pathway into the main condensers, rather than reaching the reactors. Yet in over 40 years, this had never been tested !
NHK remarks that all the official enquiries have reported and peoples' memories are fading, yet the disaster has still not been fully explained. The third programme ends with: 'We'll keep digging to uncover the truth about the accident'. However, even these NHK programmes reveal deficiencies of design and operation additional to the official reports. Moreover, the re-enactments show the consequences of nuclear decay heat and the logical impossibility of preventing or averting every possible failure in such complex systems.
2014-01-16 NHK Fukushima 'Meltdown' Documentaries
There have been many official enquiries into the Fukushima disaster (2011-03-11). However NHK, the leading Japanese broadcaster, waited a year or more until people were ready to talk, interviewed over 300, later 400, of those directly involved and outside experts, and collected huge amounts of data. This has enabled realistic re-enactments of the sequence of events. So among many other programmes on the Fukushima disaster, NHK has produced three 'Meltdown' documentaries in English, first broadcast on 2012-01, 2012-08-18, and 2013-03-05. This last was about 24 months after the disaster