No abstract

reactor that could produce more plutonium than it consumed (dubbed a "breeder reactor") was first raised during World War II by scientists in the U.S. atomic bomb program. They were concerned that uranium 235, the rare chainreacting isotope that fuels today's nuclear reactors, was insufficiently abundant on Earth to support a large-scale deployment of nuclear power. Over the next 20 years, Britain, France, Germany, India, Japan, and the Soviet Union followed the United States in establishing national plutonium breeder reactor programs. (Belgium, Italy, and the Netherlands joined the French and German programs as partners.) In all of these programs, the main driver was the hope of solving the long-term energy-supply problem by deploying large numbers of nuclear power reactors. In "Fast Breeder Reactor Programs: History and Status," a new report by the International Panel on Fissile Materials, experiences with fast breeder reactors in six countries are examined. 1 These studies make clear that the assumptions driving the pursuit of breeder reactors for the past six decades have proven to be wrong. False assumptions. The rationale for pursuing breeder reactors was based on the following key assumptions (sometimes explicit, sometimes implicit): (1) Uranium is scarce, and high-grade deposits would quickly become depleted if light water nuclear reactors, which do not breed more fuel than they consume, were deployed on a large scale; (2) breeder reactors would quickly become economically competitive with light water reactors (the dominant reactor

The South Asian nuclear race is moving to sea, with India's government announcing that it has successfully put nuclear weapons at sea, and evidence suggesting that Pakistan is preparing to do so. This article traces India's decision to deploy nuclear-powered submarines, some armed with nuclear weapons, and the debate in Pakistan on the utility of nuclear-armed submarines and the possible acquisition of nuclearpowered submarines. The article then reviews the global history of submarine accidents, especially those where nuclear-powered submarines were involved, and looks in particular at the consequences of a potential naval reactor accident where radioactivity might be released into the environment. Such naval reactor accidents constitute a major but unappreciated challenge associated with the deployment of nuclear submarines in addition to new pathways for escalation to nuclear war that are more widely recognized.

We consider the influence of water on the near-surface rheology of Venusian and terrestrial rocks and hence the way their heat transfer processes have been able to shape their planetary surfaces. We suggest that Earth is now unique in having plate-like surface movements at velocities characteristic of 'deep' material in self-regulating convective states (-few cm/year) only because liquid water is there available to facilitate mechanical failure of its lithosphere (sic). The relative absence of free water on Venus is thought to more than compensate for the effect of higher temperatures on the deformability of its surface rocks and is interpreted as the reason for an absence of Earth-like platetectonics and the distinctive distributions of volcanism and seismicity accompanying such a process for > lo9 years. The characteristics of Venusian volcanism in its post plate-tectonic era are now expected to be similar to Earth's intraplate ('hotspot') volcanism.Terra Nova, 2,[455][456][457][458][459]

The Treaty on the Prohibition of Nuclear Weapons requires States Parties to designate a "competent international authority or authorities" for negotiating and verifying the irreversible elimination of nuclear-weapons programs. Ensuring that such an authority or authorities is able to be fit for purpose when required to meet these tasks will be crucial for both the future implementation and legitimacy of the Treaty. To address this challenge, this article proposes the early creation of a two-part organizational structure, comprising an implementation support unit and a dedicated scientific and technical advisory body, to begin the process of institutionalizing the treaty, and build the technical basis for meeting its verification goals should a nuclear-weapon-possessing state decide to join. The article then discusses how such two-part structure could be scaled-up as a standing international organization tasked with the coordination of an ad hoc inspectorate, which would also cooperate and complement the work of existing nuclear verification organizations, such as the International Atomic Energy Agency. This evolutionary and adaptive strategy to institution building could empower the new Treaty by supporting the emergence of a new regime complex for nuclear disarmament, while taking into account the initially limited financial and technical resources of its member states.