Fukushima

UPDATE, Thursday, Japan admitted this week that not only did three reactors melt down (Unit 4 had no fuel in its core, otherwise it would have melted too), but that the fuel melted through the containments. Not really news: the U.S. NRC had made that assessment in the first week of April (see April 6 and 7 below).

UPDATE, Thursday, Concern is growing that radioactive water in the reactor buildings and other facilities at Fukushima Daiichi may again be released into the ocean. Water levels have been rising, partly as a result of continued pumping of water for cooling and partly as a result of heavy rains last weekend from Typhoon Songda, which fortunately only grazed the Fukushima site. A Tepco spokesman said today that radioactive water could begin to overflow trenches within 5-7 days.

UPDATE, 11:30 am, Thursday, Evidence is growing that the March 11 earthquake itself caused major damage to the Fukushima Daiichi reactors even before the accompanying tsunami knocked out offsite power and ensured the subsequent meltdowns.

UPDATE, 2:30 pm, Friday, The world’s media are shocked (shocked, we tell you…) that three Fukushima reactors melted down. Where have they been the past 10 weeks? Where did they think all that radiation was coming from? You know, that radiation that has caused the evacuation/relocation of people as far as 25 miles from the reactor site? Not to mention contamination of food, seawater, etc…..

UPDATE, 12:30 pm, Monday, On March 27, we reported on a press conference by a Japanese nuclear engineer who believed that the meltdown at Unit 1 was caused by a loss-of-coolant accident initiated by the earthquake itself, which was exacerbated by the ensuing tsunami and loss of power. It now appears that assessment was correct. Tepco said today that radiation levels inside Unit 1 were measured at 300 MilliSieverts/hour within hours of the earthquake—meaning that fuel melting already had begun. For melting to have begun that early, coolant must have been lost almost immediately. It’s now believed that fuel melted and dropped to the bottom of the containment—melting a hole into it, within 16 hours. Most likely, a major pipe carrying cooling water to the core was damaged by the earthquake, which should lead to a new evaluation of the ability of key reactor components to withstand seismic events.

UPDATE, 11:30 am, Thursday, At a Tokyo press briefing today, Tepco officials said that there is likely a hole inside the Unit 1 containment which is allowing highly radioactive water to leak—where the water is leaking to isn’t known at this point. Tepco has flooded Unit 1 with some 11 million liters of water so far, and the unit can only physically hold less than 8 million liters—although much of that loss could have been by evaporation and release of radioactive steam. But now Tepco admits that the fuel rods inside Unit 1 are essentially uncovered—meaning that much of the water poured into the reactor has leaked back out. Much of the fuel—exactly how much isn’t known–is now a molten mass on the bottom of the reactor vessel.

UPDATE, 2:30 pm, Tuesday, Japanese Prime Minister Naoto Kan announced today that Japan is scrapping plans to build 14 new nuclear reactors and instead will rethink its energy policy with a focus toward renewable energy sources and efficiency.

UPDATE, 12:30 pm, Friday, Speculation in some media reports that Unit 1 will reach a cold shutdown within a week appears unwarranted; at best it will take about a month to achieve that goal—and that’s if all goes well. Of course, Units 2 and 3 need to reach cold shutdown (and fuel pools, esp. for Units 3 and 4 need to be brought fully under control) before this can move from an “ongoing accident” situation to a clean-up situation. Temperatures in all three units with fuel in the core (Units 1, 2 & 3) remain above the boiling point, meaning water continues to boil off and fuel rods remain exposed.