Brad W. Sleaford

The Attractiveness of Materials in Advanced Nuclear Fuel Cycles for Various Proliferation and Theft Scenarios

We must anticipate that the day is approaching when details of nuclear weapons design and fabrication will become common knowledge. On that day we must be particularly certain that all special nuclear materials (SNM) are adequately accounted for and protected and that we have a clear understanding of the utility of nuclear materials to potential adversaries. To this end, this paper examines the attractiveness of materials mixtures containing SNM and alternate nuclear materials associated with the plutonium-uranium reduction extraction (Purex), uranium extraction (UREX), coextraction (COEX), thorium extraction (THOREX), and PYROX (an electrochemical refining method) reprocessing schemes. This paper provides a set of figures of merit for evaluating material attractiveness that covers a broad range of proliferant state and subnational group capabilities. The primary conclusion of this paper is that all fissile material must be rigorously safeguarded to detect diversion by a state and must be provided the highest levels of physical protection to prevent theft by subnational groups; no “silver bullet” fuel cycle has been found that will permit the relaxation of current international safeguards or national physical security protection levels. The work reported herein has been performed at the request of the U.S. Department of Energy (DOE) and is based on the calculation of “attractiveness levels” that are expressed in terms consistent with, but normally reserved for, the nuclear materials in DOE nuclear facilities. The methodology and findings are presented. Additionally, how these attractiveness levels relate to proliferation resistance and physical security is discussed.

Measurements of the angular and temporal structure of second‐harmonic emission from laser‐produced plasmas

We have measured and analyzed the second harmonic emission, both in the plane of the laser electric field and perpendicular to it, at several angles near 135° from the laser wave vector. The experiments used from 1 to 80 J of 1.053 μm light to irradiate carbon–hydrogen (CH) targets with a 550 ps pulse. A random phase plate was used, producing characteristic intensities in the range of 1013–1014 W/cm2. This was sufficient to drive the Ion Acoustic Decay Instability, producing Stokes emission well‐separated from the emission spike at the second harmonic of the laser frequency. The spectral structure of the Stokes emission was qualitatively similar for all intensities and angles of observation. The duration of the signals showed trends anticipated from linear theory. To explain the scaling of the signal strength and spectral width requires nonlinear theory.

Measurement of the frequency and spectral width of the Langmuir wave spectrum driven by stimulated Raman scattering

Thomson scattering was used to measure the spectrum of Langmuir waves, in both frequency and wave number, driven below quarter-critical density by a laser beam. These measurements were capable of detecting and identifying waves driven by stimulated Raman scattering (SRS) and also of detecting waves driven by other effects such as the bump-on-tail instability postulated by the enhanced Thomson scattering model of Raman emission. The observed Langmuir waves were consistent with SRS and not with other possible sources. The width in k-space of the measured Thomson scattering signals also has implications for the saturation amplitude of the Langmuir waves.

Thomson scattering measurements of ion‐acoustic waves driven by ion‐acoustic decay instabilities

A large angle, multichannel ultraviolet Thomson scattering diagnostic was developed to study ion‐acoustic waves in laser‐produced high‐density plasma. The time evolution of the spectral density function of the ion‐acoustic wave (IAW) was measured by the scattering system. When a weak IAW was excited, the measured spectrum had a well‐defined narrow peak, which was consistent with plasma parameters predicted by computer simulations assuming an electron transport flux limit of 0.1. The spectrum of the IAW was quite different, and broad, when it was excited strongly.