the sea from the Fukushima Dai-Ichi nuclear plant was 20 times the amount estimated by its owner, Tokyo Electric Power Co. Atmospheric releases were cited as amounting to 35,800 terabecquerels of caesium-137 by the Atmospheric Chemistry and Physics journal—an estimate about 42 percent of that released into the atmosphere in the Chernobyl explosion in 1986. Caesium-137 has a half-life of 30 years. November 2011 Tuesday, 1 November TEPCO reports the completion of a cover for the reactor unit 1, which is 54 metres high, 47 metres wide and 42 metres deep. The cover has a built-in ventilation system that is supposed to filter radioactive material. Wednesday, 2 November Boric acid is injected into reactor number 2 after the discovery of xenon in its containment vessel. The presence of xenon may be an indication that a self-sustained fission reaction has been occurring. Friday, 4 November TEPCO retracts Wednesday's statement about a possible self-sustained fission reaction, and now claims that the xenon was a result of the normal decay of radioisotopes in the fuel. Thursday, 17 November The Japanese government bans shipments of rice from a farm near the Fukushima Dai-ichi nuclear plant. 630 becquerels of caesium per kilogram was found in the rice, over the 500 becquerels of caesium per kilogram allowed for human consumption. (From hundreds of spots tested around Fukushima, none had previously exceeded the limit.) Tuesday, 29 November TEPCO now claims that there was no explosion at reactor number 2 on 15 March as previously reported, and that instead the explosion occurred at reactor number 4. However, TEPCO has no explanation for the observed rise in radioactive emissions from reactor 2 at this time. Wednesday, 30 November TEPCO reports that a new computer simulation of the meltdown shows nuclear fuel rod material melting through the pressure vessel and deep inside the concrete of the primary containment vessel, within a foot of breaching it fully in Reactor No. 1. In the pessimistic scenario, all of the fuel of Reactor No. 1 has escaped the pressure vessel, as well as a majority of the fuel for Reactor No. 2 and 3. December 2011 Saturday, 3 December Forty-five tons of highly radioactive water leaked from the apparatus being used to decontaminate the water at the plant. Plant workers attempted to contain the leak, but it was unknown if any of the water escaped into the water table or the ocean. Thursday,