Cutaway diagram of the central reactor vessel and thick concrete containment in a typical boiling water reactor of the same era as Fukushima Daiichi 1
Yah beat me.
Re: Pressure and releases
quote from the article’s analysis:
“Without enough power for cooling systems, decay heat from the reactor cores of units 1, 2 and 3 has gradually reduced coolant water levels through evaporation. The consequent increase in pressure in the coolant circuit can be managed via pressure release valves. However, this leads to an increase in pressure within the reactor building containment. Tepco has said that the pressure within the containment of Fukushima Daiichi 1 has reached around 840 kPa, compared to reference levels of 400 kPa.”
(840 kPa is approx 122 psi)