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Microdosimetric investigations were performed in a solid TE phantom at the DT-neutron generator at Hamburg-Eppendorf. Event size spectra were measured at different depths on the axis of a 10 X 10 cm2 field and at different lateral positions at a constant depth. Additionally, the microdosimetric spectrum of a 60Co source was determined. From radiobiological measurements the relative biological effectiveness (RBE) of crypt stem cells of mice was estimated as a function of lineal energy. The measured microdosimetric spectra are folded with this RBE function so that RBE values at different positions in the phantom were obtained. The predicted change of the RBE inside and outside the useful beam of a 10 X 10 cm2 field is shown. Contributions to the RBE dose from the various charged particle components are analyzed separately.

Argonne National Laboratory has performed research and development on the use of Associated Particle Sealed-Tube Neutron Generator (APSTNG) technology for treaty verification and non-proliferation applications, under funding from the DOE Office of Nonproliferation and National Security. Results indicate that this technology has significant potential for nondestructively detecting elemental compositions inside inspected objects or volumes. The final phase of this project was placement of an order for commercial procurement of an advanced sealed tube, with its high-voltage supply and control systems. Procurement specifications reflected lessons learned during the study. The APSTNG interrogates a volume with a continuous 14-MeV neutron flux. Each neutron is emitted coincident with an "associated" alpha-particle emitted in the opposite direction. Thus detection of an alpha-particle marks the emission of a neutron in a cone opposite to that defined by the alpha detector. Detection of a gamma ray coincident with the alpha indicates that the gamma was emitted from a neutron-induced reaction inside the neutron cone: the gamma spectra can be used to identify fissionable materials and many isotopes having an atomic number larger than that of boron. The differences in gamma-ray and alpha-particle detection times yield a coarse measurement of the distance along the cone axis from the APSTNG emitter to each region containing the identified nuclide. A position-sensitive alpha detector would permit construction of coarse three-dimensional images. The source and emission-detection systems can be located on the same side of the interrogated volume. The neutrons and gamma rays are highly penetrating. A relatively high signal-to-background ratio allows the use of a relatively small neutron source and conventional electronics. No collimators or personnel radiation shielding are required, and a complete APSTNG inspection system could be transported in an automotive van. Measurements have been performed to study the system stability, reliability, spatial depth resolution of identified elements along the cone axis, element composition ratios, discrimination between items of different composition, and the characteristic signature of prompt gamma rays from uranium fission. Proof-of-principle experiments and analyses have been conducted related to weapons dismantlement, detection of uranium and plutonium smuggling, radioactive waste characterization, detecting cocaine in propane tanks, and identifying chemical and high-explosive munitions. The table on the next page summarizes proposed APSTNG applications mentioned in this report. They have been grouped into six categories: Monitoring warhead dismantlement, monitoring at checkpoints for smuggled fissionable material, miscellaneous arms-control and nonproliferation, detecting contraband explosives, detecting illicit drugs, and waste remediation. These items illustrate the range of potential use of this technology, but not necessarily its limits.

Results of Fuel Heterogeneity Experiments Applied to Entire Core 43. Assembly Configuration for Distributed Worths Experiments. 44. Assembly Configuration for Measuremients of Worth of Enriched Uranium Column 45. Reactivity Worth of Enriched Uranium Column Versus Radius 46. Assembly Configuration for Measurements of Worth of Sodium Column 47. Reactivity Worth of Sodium Colunans Versus Radius ....... LIST OF FIGURES No. Title Page 48. Assembly Configuration for Measurements of Local Sodium Worth. 49. Reactivity Worth of Sodium in Local Volumes. 6 50.