MIT team finds that the ratio of component atoms is vital to performance.
A recent article in the Christian Science Monitor that was distributed by its syndicate and appeared in newspapers across the country contains many misconceptions about the MIT nuclear reactor and other research reactors. This article should clarify these misconceptions.
Nuclear science and engineering are critical areas of research and study in the United States. Important medical diagnoses and therapies as well as energy advances owe their existence to nuclear science. As one of about two dozen university research reactors in the United States, the MIT reactor is an important contributor to achieving these goals.
MIT uses its reactor primarily for research in nuclear medicine, particularly neutron capture therapy (NCT), which is a novel method for the treatment of incurable brain cancers. In addition, the reactor is used for research on advanced materials, environmental and geochemical analysis.
This 5-megawatt research reactor, which does not generate power, has been in safe operation since the 1950s. Safety and security receive the highest priority at the MIT reactor, which is a model for a contained, safe, secure environment to carry out this research.
The use of HEU (highly enriched uranium) fuel in the MIT reactor has been questioned. The MIT reactor has a small core and cannot operate with the current LEU (low enriched uranium) fuels because they do not contain sufficient amounts of the necessary uranium isotope. Ongoing research at the Argonne National Laboratory may develop a higher-density LEU. MIT is committed in writing to the NRC to convert its reactor to LEU once an LEU of suitable density is available.
MIT follows NRC-approved security procedures for the operation of its research reactor, including the handling of its HEU. In particular, we maintain our onsite inventory of fresh HEU at zero as much as possible. Thus, there is normally no fresh fuel to steal should someone try to do so. If a refueling is required, the HEU is delivered in amounts insufficient to create a weapon.
The HEU in our core or which accumulates in our spent fuel storage pool is also not attractive as weapons-grade material for several reasons:
1. We maintain the inventory of spent fuel as low as possible by expeditiously returning such fuel to the U.S. Department of Energy, using sound security procedures that are subject to considerable scrutiny by law enforcement and other public officials.
2. The fuel is not attractive because it is alloyed with other metals. Also, once irradiated for even a short time, fission products make it unusable in a weapon without extreme measures involving separation and processing. The technologies to achieve separation are complicated and time-consuming.
The current status and potential availability of weapons-grade fissile materials in the former Soviet Union and in certain Third World areas have recently been the subject of a report on securing nuclear weapons by Harvard University ("Securing Nuclear Weapons and Materials: Seven Steps for Immediate Action," by Bunn, Holdren and Wier) and a National Nuclear Security Agency (NNSA) Congressional budget request (Defense Nuclear Nonproliferation/International Nuclear Safety and Cooperation section of the 2003 DOE Congressional Budget Request). These documents make clear the need to identify all such materials and to place them in secure storage pending their ultimate disposition.
Unfortunately, the Harvard Report and the text of the NNSA Budget Request appear to have created confusion within the media. The focus of both documents is material in the former Soviet Union/Third World areas where some reactors are subject to poor or non-existing security, where regulatory agencies are ineffective, and where the funding to ensure appropriate safeguards is insufficient. Media reports have inaccurately assumed that these problems also exist at research reactors in operation in the United States and Europe as well as in other modern economies such as Japan, Korea, Australia, and Canada.
Equating the security status of research reactors in the former Soviet Union with those in the developed world has no basis in fact and needlessly alarms the public. That alarm may in turn cause public authorities to devote more of their attention to the security of U.S. research reactors and consequently less to overseas programs such as those advocated by the NNSA. We can ill afford to do this because such activity diverts us from the real nuclear threat to our security: the unsecured material in the former Soviet Union and Third World areas.
The Christian Science Monitor article illustrates the confusion. Midway through the article, the author reports:
"Research reactors pose a safety threat because they are not as closely regulated as nuclear power plants," says the U.S. Department of Energy's 2003 congressional budget request. "If attacked with a conventional explosive, some could have a radiological release equivalent to Chernobyl."
In its budget request (see pp. 168-173), the NNSA is not talking about U.S. reactors at all. It is referring to some unspecified Russian reactors. The CSM article misconstrued the NNSA words to create a very false and very wrong conclusion.
It is misleading to compare a U.S. research reactor to Chernobyl. Not only are the designs and purposes totally different, but U.S. research reactors have vastly smaller amounts of fuel than the Chernobyl reactor and operate at power levels that are orders of magnitude smaller than the 3,200-megawatt Chernobyl reactor. The amount of radioactivity present in a reactor is a function of the amount of fuel, the rate at which the fuel is converted to radioactive fission products (i.e., the power level), and the total operating time. A 5-megawatt research reactor simply doesn't compare with a 3,200-megawatt power reactor.
A version of this article appeared in MIT Tech Talk on August 14, 2002.