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Guarding U.S. Nuclear Facilities: The ABCs Of DBTs

Anyone familiar with risks and accident histories knows that for every major disaster in a reasonably complex system, there are usually several less damaging minor incidents that can be called near misses or close calls. The May 27 intrusion at Oak Ridge is just such a near miss.

Earlier this summer, I blogged about a small but determined team of anti-nuclear protesters, including a nun, who managed to get uncomfortably close to a supposedly secure stockpile of nuclear material maintained by the U. S. Department of Energy in Oak Ridge, Tennessee. Fortunately, the most damage they caused was spray- painting some slogans on a wall, but if they had been terrorists determined to steal enough enriched uranium to make a nuclear weapon, the story might have ended differently. 

A recent report by a group of researchers at the LBJ School of Public Affairs at the University of Texas at Austin points out what they consider to be serious flaws in the way we currently establish levels of security for the various nuclear facilities in the U. S., which range from small research reactors and commercial nuclear power reactors up to full-scale armed nuclear weapons. According to their report, the present method of deciding how much security is enough is based on something called the Design Basis Threat (DBT). While the basic idea seems sound, the devil, as always, is in the details.

In order to protect something, you have to know (or guess) what you’re protecting it against. The way the Design Basis Threat approach works is as follows. Say you run a small research-type nuclear reactor, the kind operated by many universities, including for example the University of Texas at Austin. You go to the appropriate agency, in this case the Nuclear Regulatory Commission, and ask what the appropriate Design Basis Threat is for your facility. It turns out that “research reactors generally do not have to protect against radiological sabotage or provide an armed response to an attack.” The Design Basis Threat is presumably an attack so feeble that the usual class of security guards found on college campuses would be able to handle it. So you just go with the minimal kind of security you will typically find at a high-dollar lab of any kind in a public university, and you’re set.

On the other hand, if you run a large commercial power reactor near, say, New York City, such as the Indian Point plant on the Hudson, you are told that your Design Basis Threat includes “multiple groups attacking from multiple entry points; willing to kill or be killed; possessing knowledge about target selection; aided by active and/or passive insiders; employing a broad range of weapons and equipment, including ground and water vehicles.” This typically means you have to maintain a dozen or so military-style armed guards at all times who are ready to fight off an attack by people who intend either to steal fissionable material or to blow up the place and spread the hot stuff around. However, no commercial nuclear facility is required to be secure against an attack from the air. 

The requirements for safeguarding nuclear weapons, generally held only by the U. S. military, are even more stringent, as you might imagine. 

Anyone familiar with risks and accident histories knows that for every major disaster in a reasonably complex system, there are usually several less damaging minor incidents that can be called near misses or close calls. The May 27 intrusion at Oak Ridge is just such a near miss, and to my mind seems to indicate that there may be cracks in the armor with which we protect our nuclear assets. And some of these cracks may be due to the uneven way the Design Basis Threats are assigned, depending on the size and nature of the nuclear facility.

The main criticism that the UT Austin researchers mount agains the current DBT regime is that while the larger facilities may be more likely to attract certain types of attacks, the nuclear material in the smaller facilities could be just as dangerous if stolen. And the very fact that research reactors are not heavily guarded like commercial nuclear power plants are, makes the smaller operations more attractive to a potential terrorist, not less, if all they are trying to do is obtain a fissionable amount of material. The UT Austin researchers point out that there are several examples of regulatory agencies backing down on the level of the assumed DBT because of industry’s protests that the resulting required protective measures would be too expensive.

This is one of these matters that may never be resolved unless we wake up some morning to the news that a major attack on a nuclear facility has succeeded. And I hope that never happens. But I can’t help but agree at least with the report’s claim that some of the ways that DBTs are currently established are lacking in logic. For example, the Nuclear Regulatory Commission has stated that current nuclear plants have enough strength in their existing containment vessels to withstand aircraft attack without any further enhancements. But on the other hand, it has made a rule for new nuclear-plant designs: designers must show how the plant will withstand the intentional crash of a commercial airliner into it. Probably the truth of the matter is that nobody knows what would have happened if the 9/11 attackers had targeted the Indian Point plant instead of the symbolically much more attractive World Trade Center towers. But it’s clearly something we don’t want to learn about from experience.

The UT Austin report will probably be criticized as an academic armchair exercise by those who spend their lives in the nuclear industry. But academics who are remote from day-to-day issues in an industry can nevertheless bring different and sometimes valuable perspectives to a problem, and so I hope the report’s suggestions of how to improve nuclear security in the U. S. contribute to the ongoing challenges of living with nuclear materials, benefiting from them where possible, and not allowing them to fall into the wrong hands.

Sources: I referred to a news article about the Nuclear Proliferation Prevention Project’s report which appeared on the CNN website on Aug. 15, 2013 at The Project’s working paper itself can be accessed at Full disclosure: I hold a Ph. D. in electrical engineering from the University of Texas at Austin and a part-time research professor appointment there. My blog on the protesting nun and her group appeared on May 27, 2013.

This column originally appeared on the Engineering Ethics blog, you can find it by visiting

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