Carnegie Endowment for International Peace, was of the opinion that "Fukushima is not the worst nuclear accident ever but it is the most complicated and the most dramatic, was a crisis that played out in real time on TV. Chernobyl did not." A survey of radiation in seawater outside unit 2 shows radioactive isotope concentrations (iodine-131, caesium-134 and caesium-137) falling for the third consecutive day since the leak was plugged. However, the levels are still high at several thousand times legal levels. Other nuclides are being investigated, but Japanese regulator NISA has flagged up problems with TEPCO's sampling methodology. Monday, 11 April Coolant injection into reactors 1 and 3 is interrupted for 50 minutes due to a loss of power after a strong earthquake in the region. Workers plan to pump water into turbine condensers, but need to pump water out of them first. Work to transfer water from the unit 2 and unit 1 condensers to a central storage tank was completed on 9 and 10 April. Workers have also knocked holes through the turbine hall buildings of units 2 and 4 to accommodate hoses for the water transfer. At unit 3, work continues to make space for water in the turbine condenser by pumping existing water into other tanks. Japanese news wire NHK reports that workers are laying hoses to transfer water to an LLW waste processing facility, which continues to be inspected. TEPCO says that it cannot start work switching on emergency systems on site until the turbine hall is dry. NHK also reported that radioactive water filling a tunnel near unit 2 has risen 12 cm since a leak in a trench was stopped on Wednesday 6 April. Tuesday, 12 April Japan officially raises Fukushima to INES Level 7, the same as Chernobyl. This new rating considers the accidents as a single event and uses estimated total release to the atmosphere as a justification. Following the hydrogen explosion in the reactor 1 building on 12 March and releases from the reactor 3 building, the equivalent of 190,000 terabecquerels of radioactive iodine had been released from the reactor buildings by 15 March, according to calculations by the Nuclear Safety Commission of Japan. A terabecquerel is equivalent to 1 trillion becquerels. The high level meant that by 15 March the Fukushima plant accident had already reached the worst level 7 on the International Nuclear and Radiological Event Scale,