Workplan for the ARIES Neutron Source Study


Introduction and Background

The application of fusion plasmas as neutron sources has been considered since the earliest days of the fusion program. Initial considerations included: (1) hybrids for fuel breeding, that is, in an energy-suppressed mode of operation, and also hybrids for energy production, that is, in a mode in which the fusion neutrons drive a subcritical blanket; (2) the use of fusion neutrons for the transmutation of radioactive waste from fission reactors; and (3) the application of a fusion-based neutron source for fusion materials and engineering testing.

More recent studies have added to the repertoire of possible applications such as tritium production, the burning of plutonium from dismantled weapons, radioisotope production, hydrogen production, and the detection of explosives. A unique characteristic of the more recent studies is the consideration of applications allowing a range of neutron source strengths from ~1011-1013 n/s, on the low end, up to ~1019- 1021 n/s on the high end. The high-end studies have considered plasmas based on either advanced mode tokamak operation or the spherical torus. The low-end studies have focused on inertial electrostatic confinement concepts.

Most studies have considered the D-T fuel cycle, but a few have examined the D-D-T fuel cycle. Although less reactive than the D-T fuel cycle, the D-D-T fuel cycle has the advantages of (1) eliminating the need for tritium breeding, and (2) providing a much greater neutron excess per unit power than the D-T fuel cycle.

For the most part, existing fusion neutron source studies have been at the conceptual level. As yet there has been no detailed, self-consistent study which considers engineering, economics and environmental issues. Moreover, no detailed development plan exists.

In assessing the potential of a fusion-based neutron source, the potential of fission-based and accelerator-based systems must also be considered and evaluated. Recent studies of fission reactors and accelerators for tritium production have employed a useful metric for comparative purposes, the cost of neutrons. In these studies the estimated neutron costs have been in the range of $60,000-$120,000 per mole of neutrons. Thus, cost of neutrons would provide a useful metric in assessing a fusion-based neutron source. Other useful metrics would include: the unique features of the neutron source; the total number of moles of neutrons produced per year; the total capital cost; the value of the product; the magnitude of the extrapolation from the current physics and technology databases; the complexity of the system; the environmental, safety and health effects; and the timeframe and cost of the development plan.

As a final point in this discussion, I note that in a recent document, "The Decision-Makers' Forum on a New Paradigm for Nuclear Energy", two priority issues identified for nuclear technology were: (1) to develop options for disposal and recycle of spent fuel; and (2) the use of new and existing reactors to burn weapons plutonium.

Proposed Workplan

Based on the previous discussion it is proposed that the ARIES team undertake the study of a fusion-neutron source focused at the high-end neutron strength, ~1019-1021 n/s. The purpose of this study would be to assess the potential and competitiveness of a fusion neutron source as a near-term application of fusion energy research. This study would consist of two phases: (1) a concept definition phase; and (2) a design phase, including the evolution of a development plan.

The concept definition phase would last about six months; however, the ARIES team would focus effort to provide a preliminary report on the results of this phase at the Snowmass Meeting in July. A status report would be provided at the ARIES May Meeting. The concept definition phase would consist of the five activities described below:

  1. Continued assessments to identify the most useful application and product. This activity would be coordinated by Les Waganer. Les would involve other members of the ARIES Team and selected individuals from the fusion program and outside the fusion program.

  2. Continued interactions with the fission and accelerator communities to understand the potential of reactors and accelerators for neutron source applications. This activity would be coordinated by Don Steiner. Don would involve Dave Petti, Laila El-Gubaly, Dai Kai Sze, Ron Miller, Leslie Bromberg and individuals outside the Team.

  3. System studies to assess the performance/metrics of ITER-based and advanced mode tokamaks, and the spherical torus for neutron source applications. These studies would include assessments of both the D-T and D-D-T fuel cycles. This activity would be coordinated by Ron Miller. Ron would have input from Steve Jardin and the Physics Group, and Mark Tillack and the Engineering Group.

  4. A compilation and assessment of the engineering and nuclear performance of the various concepts proposed for neutron-source applications including fusion, fission and accelerator systems. This activity would be coordinated by Mark Tillack with substantial input from Laila and the Wisconsin Group, and Dai Kai and the ANL Group. Ed Cheng would also be involved in this activity.

  5. An assessment of the environmental, safety and licensing implications of fusion neutron-source applications such as plutonium disposition and radioactive waste transmutation. This effort would be coordinated by Dave Petti with input from others as determined by Dave.

Assuming a favorable result from the concept definition phase, an embodiment would be chosen for the design phase. It is assumed that the design phase would be completed in 12-18 months.