Pilgrim has a Mark 1 containment design, just like the four stricken reactors in Fukushima. The year that Pilgrim was licensed, Atomic Energy Commission Chairman Joseph Hendrie considered ending the practice of allowing such reactors in his response to this memo from Steven Hanaur. But of course his loyalty to the industry was greater than any concern for public safety, so he wrote this memo.
Harold Denton, then the NRC’s top safety official, said in 1986, “you’ll find something like a 90% probability of that containment failing.” After this statement the NRC suggested that owners of Mark 1 and Mark 2 reactors might want to install vents to relieve ‘over-pressurization’ of the wimpy containment structures. Most, including Fukushima units 1-3, did. Pilgrim was the first to install a vent. For most people, “Vented containment” is an oxymoron, but not the industry.
In March of 2011, the vents were tested for the first time – at Fukushima units 1, 2 and 3. All three failed: massive explosions occurred resulting in major releases of radioactive material and containments that continue to leak today, and probably will for many years. Unit 4 also suffered a massive explosion, although it had no fuel in the reactor.
So the containments don’t contain and the vents don’t help. So 41 years later and nearly 2 years after Fukushima, the NRC started thinking about… not closing these accidents-waiting-to-happen, but possibly filtering the vents (as is done in France and Germany). Of course this would cost the industry MONEY, which put the Commissioners in a position similar to that of Chairman Hendrie in 1972, and caused heavy lobbying by the nuclear industry.
David Lochbaum of the Union of Concerned Scientists testified about filtered containment vents to the NRC last December, and wrote about it on the excellent site All Things Nuclear.
Almost exactly 2 years after the Fukushima disaster, a majority of the commissioners voted to disregard their Staff Safety Recommendation, allowing 31 operating U.S. Fukushima-style reactors to operate without filters on their “containment” VENTs.