Photos showing radioactive steam release via SRV (Safety / Steam Relief Valves March 15th 2011): Original TEPCO PDF: http://www.tepco.co.jp/cc/press/betu15_j/images/151217j0102.pdf
December 2015 – similiar photos from the Leningrad RBMK Reactor near St. Petersburg: http://www.express.co.uk/news/world/628592/Chaos-Russians-flee-Chernobyl-style-plant-radioactive-leak
The History of Accidents:
– On 7 January 1974, an accident happened at the Unit 1 of the Leningrad NPP. In case of this accident, a ferroconcrete gasholder of the system to retain radioactive gases was destroyed. There were no victims
by this accident.
– On 6 February 1974, a rupture of the intermediate circuit of the Unit 1 of the Leningrad NPP occurred because of water boiling in it. Three persons were killed by this accident. High radioactive water together with radioactive sludge of the filter powder was discharged into the environment.
– In October 1975, a partial destruction of the core of the Unit 1 of the Leningrad NPP occurred. The reactor was shut down and the core was cleaned on the next day after the shutdown by pumping of an emergency reserve of nitrogen through the core to the ventilation chimney. Consequently, approximately 1.5 million Curie of radioactive substances was discharged into the environment: http://www.greenworld.org.ru/?q=ang_lnpp1_main
NO Reaction from CTBTO in Vienna then and now.