Comment Re:FUD filled.... (Score 2) 212
No, it wasn't by design.
By design (back in 1962) it was supposed to use steel-clad fuel rods. Which didn't work as well as they hoped, so they were replaced by zirconium cladding. The impact of hydrogen being formed during the meltdown of a zirconium clad core was later judged to be non-catastrophic from the point of view that the containment wouldn't be destroyed. But that's about it. There were clear warnings that the destruction of the building around the containment would make handling the situation much more difficult, and of course all of the material that would otherwise be trapped in the building is released in the explosion and subsequent (uncontrolled) venting of the containment. But since such accidents were judged to be unlikely, nothing was done about those outcomes at least in the USA and Japan.
To prevent such outcomes, you need filters installed to vent the containment. While they vent the same stuff that escaped from Fukushima Daiichi, they also scrub at least 99.99% of the Cs and 99% of iodine from the stream/hydrogen/aerosol mixture before releasing it to the atmosphere. (That can be tested. From the filter-point-view it doesn't matter wether the stuff is radioactive or not, so you just use ordinary Cs or I for testing purposes.) Filters always come equipped with hydrogen recombiners (you don't want your filter to explode), which can also be installed in the rest of the containment building. Both has been required by law for more than 20 years in Germany and France - and in Japan since last year.