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@Peter it's more a general trend towards bigger reactors.. all 4 reactors at Fukushima Daini were the same spec as Daiichi 6... and for example the new Areva EPR reactor is rated at 1.6 GW

Removing highly toxic water remains difficult task at nuke plant

TOKYO, April 14, Kyodo

The government's nuclear safety agency on Thursday continued to grapple with pools of highly radioactive water at the crisis-hit Fukushima Daiichi nuclear power plant, as the level of polluted water filling an underground trench edged up again after it finished pumping out around 660 tons of water.

The removal of around 60,000 tons of contaminated water from the basements of the Nos. 1 to 3 reactor turbine buildings as well as trenches connected to them is vital because the water is hampering work to restore the cooling functions of the reactors lost since the March 11 earthquake and ensuing tsunami.

The pools of contaminated water are believed to be a side effect of plant operator Tokyo Electric Power Co.'s emergency efforts to continue injecting water into the reactors and their spent nuclear fuel pools from outside to cool them down.

The operator known as TEPCO pumped out around 660 tons of highly radioactive water Tuesday and Wednesday from one of the trenches to a ''condenser'' inside the nearby No. 2 reactor turbine building, where during normal operation steam from the reactor is converted into water.

But the Nuclear and Industrial Safety Agency said that the water level in the vertical part of the trench as of 11 a.m. Thursday had increased by about 4.5 centimeters from the level observed at 6 p.m. Wednesday.

The level of the water is now only 1.5 centimeters lower than shortly before the water-transfer mission started at 7:35 p.m. Tuesday.

Hidehiko Nishiyama, the agency's spokesman, told a morning press conference that the rise in the water level is likely linked to the continued injection of water into the No. 2 reactor core, which is necessary to prevent the nuclear fuel inside from overheating.

''As there is believed to be around 20,000 tons of water (in the No. 2 reactor turbine building and the trench connected to it), we're feeling the difficulty of lowering the level of the water in a stable manner,'' he said.

TEPCO is preparing to transfer more of the highly radioactive water into a facility for nuclear waste disposal at the plant, which can accommodate 30,000 tons of liquid.

Work is under way to ensure that the facility will be able to contain highly radioactive water safely without fear of the stored liquid leaking outside, but Nishiyama told the press conference that he was not sure when it will end.

The water in and around the No. 2 reactor turbine building is believed to contain higher concentrations of radioactive substances than other contaminated water found at the site, and is believed to originate from the No. 2 reactor's core, where fuel rods have partially melted.

The agency decided to remove water from the trench first as it feared that the water inside the trench would overflow and leak into the Pacific Ocean.

TEPCO also started looking into how to check the quake resistance of already heavily damaged reactor buildings at the site in line with an order issued Wednesday by the nuclear regulatory agency, in light of strong aftershocks from the March 11 quake.

The agency has told the utility to immediately examine the buildings and consider reinforcement work if they are judged as not sufficiently quakeproof.

TEPCO, however, has said that it cannot ''immediately conduct an investigation'' unless it confirms the safety of areas where checks will be conducted.

To enhance preparation for tsunami waves triggered by aftershocks and other emergency situations, emergency diesel power generators and vehicle-mounted power sources are to be placed at higher ground, while backup units for water injection at the troubled Nos. 1 to 3 reactors are expected to be installed, according to the nuclear agency.

Meanwhile, concern grew over the state of the No. 3 reactor at one point, as the agency said in the afternoon that the temperature of part of its reactor pressure vessel was found to be rising suddenly.

But TEPCO officials said that the data were likely due to a glitch in a measuring instrument, because other temperature data related to the vessel has not shown a similar rise.

==Kyodo english.kyodonews.jp

TOKYO - Japan’s fragile post-disaster political truce unravelled on Thursday as the head of the main opposition party called on unpopular Prime Minister Naoto Kan to quit over his handling of the country’s natural calamities and a nuclear crisis. Calls grow for Japan PM to quit in wake of quake
By LINDA SIEG AND MAYUMI NEGISHI, REUTERS
Last Updated: April 14, 2011 3:05am www.calgarysun.com

@Nancy NHK wanted you to look at physics forum (link pinned on other page). They're talking about you again...:)

@James Ward : just a glitch, no threat to human health.

Has this been posted? SRS equipment headed to Japan
Help to stabilize damaged nuclear reactors at Fukushima chronicle.augus ,,,,,,ta.com

A group of Japanese doctors on Friday urged workers at the Fukushima nuclear plant to have their blood stemcells stored as a safeguard should they be exposed to life-threatening levels of radiation.


www.deccanchronicle.com

More background documents on BWR Severe Accidents & Spent Fuel Pool Accidents via US DOE site. Not sure if these have been posted previously. (Showing links to search results page.).
There are more papers on the site that look useful.

1) Identification and assessment of containment and release management strategies for a BWR Mark I containment - published 1991
(Units 1 - 4 are Mark-1s)
www.osti.gov

2) BWR REACTOR VESSEL BOTTOM HEAD FAILURE MODES
(with a section on Debris Bed Formation in the BWR Lower Plenum)
www.osti.gov
Page 9 has an interesting summary of timing for events during station blackout.

3) Loss of Spent Fuel Cooling PRA: Model & Results
scenarios with spent fuel pools tryout
www.osti.gov

4) posted previously IDENTIFICATION AND ASSESSMENT OF BWR IN-VESSEL SEVERE ACCIDENT MITIGATION STRATEGIES with timelines for failures.
These underscore that really serious damage occurred early on.

@NHK Listener one of the videos on the pumpers trucks quoted the price of a new one, (these are slightly used) is 2.1mill plus 1.2 for freight..... and TEPCO now ownes them 3.3 mill a pumper

Japan Emperor's First Trip to Disaster Zone
www.time.com

More time needed to build tanks to hold wastewater www3.nhk.or.jp "TEPCO plans to build more tanks to hold 27-thousand tons of wastewater by the end of May."l

Japan automakers planning to check radioactivity -- new meaning to "hot rod"

4 seems to be fairly hot, but I haven't heard of anything really bad

@Markfm However, TEPCO plans to build more tanks to hold 27-thousand tons of wastewater by the end of May.

@marie rich en.wikipedia.org QUOTE from the linked site: "In June 2008, several scientists stated that the Rokkasho plant is sited directly above an active geological fault line that could produce a magnitude 8 earthquake. But Japan Nuclear Fuel Limited have stated that there was no reason to fear an earthquake of more than magnitude 6.5 at the site, and that the plant could withstand a 6.9 quake.[8][9]" Sounds familiar, doesn't it?

@James Ward It's a seriously big contaminent storage/spent fuel/enrichment facility. It's the first thing I thought of when I heard about the EQ. Scary...

Fukushima sets faithful to spin mode
James Norman From: The Australian April 11, 2011 12:00AM Then the long history of mismanagement, data falsification and cover-up that has been exposed in the global media of TEPCO, the company responsible for the Fukushima power plants, further exposed the nuclear industry to accusations of lack of proper transparency and international accountability.

Despite all this (or perhaps because of it) the nuclear industry will be redoubling its efforts to continue and hasten the growth that occurred in capacity globally last year -- seen by many as the first year of the so-called nuclear renaissance. www.theaustralian.com.au

When the Fukushima Meltdown Hits Groundwater By Dr. Tom Burnett March 27, 2011
hawaiinewsdaily.com Fukushima is going to dwarf Chenobyl.

the last time I read an article from that Hawaii news paper it was bogus