From Fukushima Diary
On 5/25/2015, Tepco reported still 960,000 Bq / hour of Cesium-134 and 137 is assumed to be discharged from Reactor 1 -4 to the air this April.
This is 2.7 times much as their provisional figure published in the end of April.
Tepco states the difference is caused by the change of calculation method. It strongly suggests the entire historical discharged volume of Cs-134/137 has been underestimated since 311 however they did not disclose the recalculated discharged volume before April of 2014.
Comparing to May of 2014, the discharged volume of Cs-134/137 increased to 180% this April. Tepco however states this is lower than 10% of the set point of “discharge control”, and they haven’t made any explanation on this increase.
Especially in Reactor 3, the discharged volume increased 78 times much as May. 2014. Also, 95,000 Bq / hour of Cs-134/137 is discharged from Reactor 4 building though it does not contain nuclear fuel.
Regarding noble gas (such as Kr-85), PCV (Primary Containment Vessel) gas control system detected 2,336,000,000 Bq of gas discharged from Reactor 1-3 every hour this April. Tepco states noble gas passes by as radioactive cloud to cause only external exposure so the exposure dose caused by the discharged noble gas should be significantly small.