040329 　原子力発電所へのテロ攻撃と使用済み燃料の一時的貯蔵方法：　ＮＡＳとＮＲＣの意見対立

度々お伝えしておりますように、現在米国で最も恐れられていることは、９．１１タイプの核テロ攻撃（原子力施設へのテロ攻撃を含む）が行われることですが、とくに原子力発電所が狙われ、使用済み燃料を一時貯蔵しているプールが破壊された場合には大変なことになる危険性があるので、使用済み燃料をなるべく早くプールから取り出して乾式貯蔵用キャスクに入れて保管すべきであるーーとする内容の報告書が全米科学アカデミー（ＮＡＳ）によりまとめられました。この報告書は9.11以後かかる危険性を懸念する議会の求めによってまとめられたものですが、この報告書を連邦政府の原子力規制委員会（ＮＲＣ）から議会に送付する3月14日付け書簡の中で、ＮＲＣは、「大量の使用済み燃料を乾式貯蔵方式で保管するのはテロ対策として効果があるか疑わしいし、金がかかりすぎるから不必要である」とのコメントをつけていたことが明らかになり、ワシントンで問題になっている模様です。この報告書自体は、ＮＲＣの判断ではテログループに知られては困る情報を含んでいるとの理由で最近まで不公表になっていたもので、現在も大部分が秘密のままですが、ＮＡＳ側では、「ＮＲＣの説明は国民に真実を伝えておらず、誤解を与えるものである」として強く批判している由。

原子力発電所関係の情報をテロ対策上どこまで公表すべきなのか、不用意にすべてを公表すれば市民に多大の不安を感じさせる一方、テログループにとって有益な情報を与えることになるわけで、この辺が難しい問題となっているわけです。他方、全米の１０３基の原子炉から出た膨大な量の使用済み燃料は、ネヴァダ州のヤッカマウンテン地層処分場に運び込まれる予定ですが、肝心のヤッカマウンテン計画が地元の反対や訴訟続きで実現が延び延びとなってなっているため、連邦政府としても動きが取れないという苦しい状況がしばらく続きそうです。詳細は以下のWashington Post記事でどうぞ。

Science Academy Study Points to Risk of Attack

A classified report by nuclear experts assembled by the National Academy of Sciences has challenged the decision by federal regulators to allow commercial nuclear facilities to store large quantities of radioactive spent fuel in pools of water.

The report concluded that the government does not fully understand the risks that a terrorist attack could pose to the pools and ought to expedite the removal of the fuel to dry storage casks that are more resilient to attack. The Bush administration has long defended the safety of the pools, and the nuclear industry has warned that moving large amounts of fuel to dry storage would be unnecessary and very expensive.

The report was requested by Congress after the terrorist attacks of Sept. 11, 2001, as homeland security officials sought to understand the potential consequences of a Sept. 11-scale attack on a nuclear facility.

Because the report is classified, its contents were not made public when it was delivered to the Nuclear Regulatory Commission (NRC) last summer. Even a stripped-down, declassified version has remained under wraps since November because the commission says it contains sensitive information.

However, the commission made excerpts of the report public when Chairman Nils Diaz sent a letter to Congress on March 14 rebutting some of the academy's concerns. His letter also suggested that the academy had largely backed the government's views about the safety of existing fuel storage systems.

E. William Colglazier, executive officer of the academy, said the letter was misleading and warned that the public needs to learn about the report's findings.

"There are substantive disagreements between our committee's views and the NRC," he said in an interview. "If someone only reads the NRC report, they would not get a full picture of what we had to say."

Although the commission said it is keeping the report under wraps for security reasons, some officials who have seen the document suggest that the NRC is merely suppressing embarrassing criticism.

"At the same time that the NRC is saying that the National Academy's study is classified and not releasable to the public, it has somehow managed to send a detailed rebuttal of the report's conclusions to Congress in unclassified form," said Rep. Edward J. Markey (D-Mass.), who has seen the report.

"I am concerned that the totality of the Commission's actions reflect a systemic effort to withhold important information from . . . the public, rather than a genuine effort to be protective of national security," Markey said in a March 21 letter to the commission's inspector general.

NRC spokesman Eliot Brenner countered that the commission is "a very open agency" and that regulators are working with the academy to make the report public.

"Our core concern is making sure that information that could reasonably be expected to be available to a terrorist is not publicly available," he said. "We are continuing to work with them on finding the right balance."

The report was solicited by Congress to study how best to store spent nuclear fuel -- tons of rods containing radioactive byproducts of nuclear fission reactions are produced each year by the nation's 103 electricity-generating nuclear reactors. Spent fuel rods generate intense heat and dangerous long-term radiation that must be contained.

Most of the spent rods are stored in large swimming-pool-like structures called spent fuel pools, said David Lochbaum, a nuclear safety engineer at the science and advocacy group Union of Concerned Scientists, who has worked at several plants. The pools are about 45 feet deep and 40 feet square and are filled with about 100,000 gallons of circulating water to remove heat and serve as a radiation shield, he said.

After cooling for about five years, the rods can be moved to dry storage -- heavy casks of lead and steel. But the casks are expensive, and commercial reactors have elected to leave the rods in the pools until the pools fill up. Lochbaum said some pools hold 800 to 1,000 tons of rods. In the event of a terrorist strike, Lochbaum said, the dry casks would be much safer, because explosions could drain the pools and set off fire and radiation hazards.

The nuclear industry wants the fuel moved to a storage site in Nevada, but that project has long been plagued by delays and opposition. Steven Kraft, director of waste management at the Nuclear Energy Institute, an industry group, said studies had shown that the pools are as safe as the dry casks -- the same position adopted by the Nuclear Regulatory Commission.

Kraft said that the risk of catastrophic attacks is minuscule and that modeling analyses have shown that even plane crashes are unlikely to affect the pools' integrity. And even if they did cause damage, he added, there would not be catastrophic consequences because of safety systems already in place.

"If the pool is safe and the casks are safe and they both meet the requirements, there is no justification for going through what is a huge amount of expense and worker exposure" to move the rods to dry storage, he said.

In his letter to Congress, Diaz said the academy's recommendation to move fuel to dry storage was based on "scenarios that were unreasonable."

But Arjun Makhijani, a nuclear engineer with the Institute for Energy and Environmental Research, a nonprofit research and advocacy organization that supports underground dry storage of the rods, said the commission had been lax.

"There is no question that any terrorist who wants to know about spent fuel has plenty of information already," he said of the withheld report. "Publication of a report on security will not help terrorists. The only thing it is hindering is discussion of public safety."

Diaz's letter to Congress shows that the academy recommended that the government conduct additional analyses to evaluate "the vulnerabilities and consequences" to storage pools of "attacks using large aircraft or large explosives." The academy also called for a review and upgrade of security measures to prevent theft of spent fuel rods by insiders and an assessment of security by "an independent organization."

The commission letter defended measures it has in place and said that "the likelihood an adversary could steal spent fuel . . . is extremely low." The letter said the additional analysis demanded by the academy study was "more than is needed" and rejected the call for an independent security analysis, saying the commission's own assessments were "sound and realistic."

To keep the report secret, the federal agency used a classification called "Safeguards Information" that it applies to data that are unclassified but reveal sensitive details about nuclear facilities and security procedures. Brenner, the spokesman, emphasized that the academy's report and the commission's response had been seen by the Department of Homeland Security and members of Congress charged with oversight. "The full report is there with those with the appropriate clearances," he said.

The academy's Colglazier said the science organization had produced many classified reports but had never encountered such hurdles in creating a public version.

"We don't want to provide information in our report that could be used by terrorists to exploit vulnerabilities," he said. "But we also want the public and decision makers to know what things need to be addressed."

The scientist also rejected Brenner's reassurance that the classified report had been seen by relevant decision makers. Governors of states with nuclear plants need to see the report, he said, and the public had an important role as well.

"The way our political system works, when politicians hear from their constituents, they are motivated to take action that they don't when the public is unaware," he said.