Reactor Design in Japan Has Long Been Questioned

By TOM ZELLER Jr.
Published: March 15, 2011

Design of G.E.’s Mark 1 Nuclear Reactors Shows Weaknesses - The New York Times

G.E. began making the Mark 1 boiling water reactors in the 1960s, marketing them as cheaper and easier to build — in part because they used a comparatively smaller and less expensive containment structure.

American regulators began identifying weaknesses very early on.

In 1972, Stephen H. Hanauer, then a safety official with the Atomic Energy Commission, recommended in a memo that the sort of “pressure-suppression” system used in G.E.’s Mark 1 plants presented unacceptable safety risks and that it should be discontinued. Among his concerns were that the smaller containment design was more susceptible to explosion and rupture from a buildup in hydrogen — a situation that may have unfolded at the Fukushima Daiichi plant.

福島の原発では上にあるMark １というGEが１９６０年代に開発したタイプの冷却炉を使っているようですが、Mark 1の安全性については当時から指摘されていたようです。

In the late 1980s, all Mark 1 reactors in the United States were also ordered to be retrofitted with venting systems to help reduce pressure in an overheating situation, rather than allow it to build up in a containment system that regulators were concerned could not take it.

It is not clear precisely what modifications were made to the Japanese boiling water reactors now failing, but James Klapproth, the chief nuclear engineer for General Electric Hitachi, said a venting system was in place at the Fukushima plants to help relieve pressure.

１９８０年代に米国内にあるMark 1の冷却炉に関しては圧力を減らすように改良されたようですが、日本にある冷却炉に関してはどのような改良がなされたのかは明確ではないとのころです。