TEPCO finds sign of fresh nuclear fission at Fukushima reactor

Unit 2 (Shut down)
- At approximately 6:00 am on March 15, an abnormal noise began emanating 
  from nearby Pressure Suppression Chamber and the pressure within the 
  chamber decreased. 
- At 10:10 am on March 26, we started injecting freshwater to the reactor 
  and are now injecting fresh water by a motor driven pump powered by the 
  off-site transmission line. 
- At 2:59 pm on September 14, we started injecting water to the reactor 
  through core spray system water injection piping arrangement in addition 
  to the water injection through reactor feed water system piping 
  arrangement.
  At 4:14 am on November 2, we adjusted the amount of water injection to 
  the reactor to approximately 3 m3/h through reactor feed water system 
  piping arrangement, and 7 m3/h core spray system water injection piping 
  arrangement.
  Water is currently injected at approx. 3 m3/h through reactor feed water 
  system piping arrangement, and at approx. 7 m3/h through core spray 
  system water injection piping arrangement.
- At 5:21 pm on May 31, we started cyclic cooling for the water in the 
  spent fuel pool by an alternative cooling equipment of the Fuel Pool 
  Cooling and Filtering System (From 10:12 am to 11:50 am on Octorber 31, 
  hydrazine  was also injected) .
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary 
  Containment Vessel.
- At 12:53 pm on October 28, we activated the exhaust fan of the gas 
  management system of the reactor containment vessel in the reactor 
  building and started test operation. As we confirmed stable operation of 
  the system, from 6:00 pm on the same day, we put the system in operation. 
- On November 1, we conducted a nuclide analysis of emitted gas sampled by 
  the gas management system of the reactor containment vessel. It was found 
  out that there was a possibility that short-half-life radionuclide (xenon 
  133, 135) was detected. There has been no significant variation as a 
  result of our continuous monitoring of the temperature and the pressure 
  in the reactor, and the figures of the monitoring posts. However, just to 
  be safe we injected boric-acid solution through reactor water injection 
  line from 2:48 am to 3:47 am on November 2, since it was undeniable that 
  fission reaction had occurred.