Leaked Study from Nuclear Regulatory Commission: Fukushima Far from Over April 7, 2011

The New York Times has obtained documents from the Nuclear Regulatory Commission’s evaluation of the ongoing crisis at the Fukushima Nuclear Facility. The document paints a grim picture of evolving threats to the afflicted facility.

• mounting stresses placed on the containment structures as they fill with radioactive cooling water, making them more vulnerable to rupture in one of the aftershocks rattling the site • the possibility of explosions inside the containment structures due to the release of hydrogen and oxygen from seawater pumped into the reactors • semimolten fuel rods and salt buildup impeding the flow of fresh water meant to cool the nuclear cores • new questions about whether pouring water on nuclear fuel in the absence of functioning cooling systems can be sustained indefinitely

In a related development, Congressman Edward Markey announced today that he had information indicating that the fuel in reactor number 2 had melted through and breached the containment vessel of that reactor, an ominous development that may have unpredictable effects.

“I have been informed by the Nuclear Regulatory Commission that the core of Unit Two has gotten so hot that part of it has probably melted through the reactor pressure vessel,” said Markey, a prominent nuclear critic in the House of Representatives

The Times article noted that the document was dated March 26, and as a result, may not have reflected some of the more recent developments, such as the apparent “re-criticality” occurring in reactor number 1, as damaged fuel has apparently been sporadically flashing to a fissioning activity, creating new radioactive materials, and more heat.

TEPCO announced today that work has begun pumping Nitrogen into the reactor 1 unit in the hopes of staving off further violent explosions from the production of hydrogen and oxygen.

The document mentions that cooling water probably has not been reaching all the fuel in the reactors.

Because slumping fuel and salt from seawater that had been used as a coolant is probably blocking circulation pathways, the water flow in No. 1 “is severely restricted and likely blocked.” Inside the core itself, “there is likely no water level,” the assessment says, adding that as a result, “it is difficult to determine how much cooling is getting to the fuel.” Similar problems exist in No. 2 and No. 3, although the blockage is probably less severe, the assessment says.

Another issue arising is the burden of tons of water on damaged reactor components, especially in light of continuing aftershocks in the area.

A rise in the water level of the containment structures has often been depicted as a possible way to immerse and cool the fuel. The assessment, however, warns that “when flooding containment, consider the implications of water weight on seismic capability of containment.” Experts in nuclear plant design say that this warning refers to the enormous stress put on the containment structures by the rising water. The more water in the structures, the more easily a large aftershock could rupture one of them. Margaret Harding, a former reactor designer for General Electric, warned of aftershocks and said, “If I were in the Japanese’s shoes, I’d be very reluctant to have tons and tons of water sitting in a containment whose structural integrity hasn’t been checked since the earthquake.”

The report also suggested that the explosion at Unit number 4 could have spread much radioactive material into the surrounding area.

An editorial in the Japan Times today quoted a group of 16 expert consultants who were advising the Japanese government TEPCO on further actions at the site. The group stated, “The situation at Fukushima No. 1 is “extremely serious” and demands Japan’s all-out efforts.”

The 16 “as people who have pushed peaceful use of nuclear power” expressed their regret over the nuclear crisis and apologized to people. But they did not hide their fear that a critical situation may develop at Fukushima No. 1. They do not rule out the possibility that as time goes on, a molten core melts a weak part of a pressure vessel and enters a containment vessel, destroying the reactor’s function to contain radioactive substances, or that hydrogen gas forming inside a pressure vessel explodes and destroys a containment vessel, causing serious radioactive contamination over a large expanse of land and sea. They warn that release of a large amount of radioactive substances could make uninhabitable not only the current evacuation zone but also larger areas.

Dave Lochbaum, and independent expert from the Union of Concerned Scientists, quoted in the story, noted:

“Even the best juggler in the world can get too many balls up in the air…They’ve got a lot of nasty things to negotiate in the future, and one missed step could make the situation much, much worse.”