[en] Los Alamos has been collaborating since 1984 with scientists from the Chinese Institute of Atomic Energy (CIAE) to develop nuclear measurement instrumentation and safeguards systems technologies that will help China support implementation of the nonproliferation treaty (NPT). To date, four Chinese scientists have visited Los Alamos, for periods of six months to two years, where they have studied nondestructive assay instrumentation and learned about safeguards systems and inspection techniques that are used by International Atomic Energy Agency (IAEA) inspectors. Part of this collaboration involves invitations from the CIAE to US personnel to visit China and interact with a larger number of Institute staff and to provide a series of presentations on safeguards to a wider audience. Typically, CIAE scientists, Beijing Institute of Nuclear Engineering (BINE) staff, and officials from the Government Safeguards Office attend the lectures. The BINE has an important role in developing the civilian nuclear power fuel cycle. BINE is designing a reprocessing plant for spent nuclear fuel from Chinese nuclear Power reactors. China signed the nonproliferation treaty in 1992 and is significantly expanding its safeguards expertise and activities. This paper describes the following: DOE support for US and Chinese interactions on safeguards; Chinese safeguards; impacts of US-China safeguards interactions; and possible future safeguards interactions

[en] This report reviews the progress to date in the measurement of delayed neutron energy spectra from fast-neutron-induced fissions of ²³²Th, ²³³U, ²³⁵U, ²³⁸U, and ²³⁹Pu

[en] The near-equilibrium energy spectra of the delayed neutrons associated with fast-neutron-induced fission of ²³²Th, ²³³U, ²³⁵U, ²³⁸U and ²³⁹Pu were measured at the University of Washington Nuclear Physics Laboratory. The neutron spectrum, produced from the ⁹Be(p,n)⁹B thick target reaction with 10 MeV protons, approximates a prompt fission spectrum. Data were collected in a repetitive sequence consisting of a 1.0-sec irradiation, 0.1-sec delay and a 1.0-sec counting period. Electrostatic deflection of the proton beam produced an on/off ratio greater than 10⁵

[en] Analytical formulations that describe the time dependence of neutron populations in nuclear materials contain delayed-neutron dependent terms. These terms are important because the delayed neutrons, even though their yields in fission are small, permit control of the fission chain reaction process. Analytical applications that use delayed neutrons range from simple problems that can be solved with the point reactor kinetics equations to complex problems that can only be solved with large codes that couple fluid calculations with the neutron dynamics. Reactor safety codes, such as SIMMER, model transients of the entire reactor core using coupled space-time neutronics and comprehensive thermal-fluid dynamics. Nondestructive delayed-neutron assay instruments are designed and modeled using a three-dimensional continuous-energy Monte Carlo code. Calculations on high-burnup spent fuels and other materials that contain a mix of uranium and plutonium isotopes require accurate and complete information on the delayed-neutron periods, yields, and energy spectra. A continuing need exists for delayed-neutron parameters for all the fissioning isotopes

[en] In recent years, both passive- and active-neutron nondestructive assay (NDA) systems have been used to measure the uranium and plutonium content in 200-ell drums. Because of the heterogeneity of the wastes, representative sampling is not possible and NDA methods are preferred over destructive analysis. Active-neutron assay systems are used to measure the fissile isotopes such as ²³⁵U, ²³Pu, and ²⁴¹Pu; the isotopic ratios are used to infer the total plutonium content and thus the specific disintegration rate. The active systems include 14-MeV-neutron (DT) generators with delayed-neutron counting, (D,T) generators with the differential die-away technique, and ²⁵²Cf delayed-neutron shufflers. Passive assay systems (for example, segmented gamma-ray scanners)5 have used gamma-ray sessions, while others (for example, passive drum counters) used passive-neutron signals. We have developed a new passive-neutron measurement technique to improve the accuracy and sensitivity of the NDA of plutonium scrap and waste. This new 200-ell-drum assay system combines the classical NDA method of counting passive-neutron totals and coincidences from plutonium with the new features of ''add-a-source'' (AS) and multiplicity counting to improve the accuracy of matrix corrections and statistical techniques that improve the low-level detectability limits. This paper describes the improvements we have made in passive-neutron assay systems and compares the accuracies and detectability limits of passive- and active-neutron assay systems

[en] The near-equilibrium energy spectra of the delayed neutrons associated with fast-neutron-induced fissions of ²³²Th, ²³³U, ²³⁵U, ²³⁸U and ²³⁹Pu are reported over the energy range 30 keV to 1500 keV. The fission source spectrum approximated a prompt fission spectrum. A significant fraction of delayed neutrons were found to exist at energies below 100 keV and peaks in the spectra are in agreement with peaks reported by others. Comparisons with existing measurements show agreement at energies above 150 keV but have significant differences at energies below this value

No abstract available

[en] The end of the superpower arms race has resulted in an unprecedented reduction in stockpiles of deployed nuclear weapons. Numerous proposals have been put forward and actions have been taken to ensure the irreversibility of nuclear arms reductions, including unilateral initiatives such as those made by President Clinton in September 1993 to place fissile materials no longer needed for a deterrent under international inspection, and bilateral and multilateral measures currently being negotiated. For the technologist, there is a unique opportunity to develop the technical means to monitor nuclear materials that have been declared excess to nuclear weapons programs, to provide confidence that reductions are taking place and that the released materials are not being used again for nuclear explosive programs. However, because of the sensitive nature of these materials, a fundamental conflict exists between the desire to know that the bulk materials or weapon components in fact represent evidence of warhead reductions, and treaty commitments and national laws that require the protection of weapons design information. This conflict presents a unique challenge to technologists. The flow of excess weapons materials, from deployed warheads through storage, disassembly, component storage, conversion to bulk forms, and disposition, will be described in general terms. Measurement approaches based on the detection of passive or induced radiation will be discussed along with the requirement to protect sensitive information from release to unauthorized parties. Possible uses of measurement methods to assist in the verification of arms reductions will be described. The concept of measuring attributes of items rather than quantitative mass-based inventory verification will be discussed along with associated information-barrier concepts required to protect sensitive information

[en] The storage and shield cask for the dual californium source is designed to shield and transport up to 3.7 mg (2 Ci) of ²⁵²Cf. the cask meets Department of Transportation (DOT) license requirements for Type A materials (DOT-7A). The cask is designed to transfer sources to and from the Flourinel and Fuel Storage (FAST) facility delayed-neutron interrogator. Californium sources placed in the cask must be encapsulated in the SR-CF-100 package and attached to Teleflex cables. The cask contains two source locations. Each location contains a gear box that allows a Teleflex cable to be remotely moved by a hand crank into and out of the cask. This transfer procedure permits sources to be easily removed and inserted into the delayed-neutron interrogator and reduces personnel radiation exposure during transfer. The radiation dose rate with the maximum allowable quantity of californium (3.7 mg) in the cask is 30 mR/h at the surface and less than 2 mR/h 1 m from the cask surface. This manual contains information about the cask, californium sources, describes the method to ship the cask, and how to insert and remove sources from the cask. 28 figs

[en] The Fluorinel and Storage (FAST) Facility delayed neutron interrogator (DNI) is a dual-assay instrument used to assay spent fuel for a criticality control check before dissolution and also to measure waste solids for material accountability before disposal. A separate shielded cubicle located below the fluorinel fuel dissolution cell houses the DNI. Two tubes penetrate the dissolution cell floor and extend down through the instrument. The smaller tube enables precision assays on waste canisters containing small amounts of uranium, and the larger tube enables measurement of fuel packages of various shapes containing large quantities of uranium. A hard-copy operations terminal located in the crane corridor above the DNI cubicle is used to operate the DNI. This location allows the operator visual access for positioning and moving samples to and from the DNI tubes. The assay system is controlled by complex software programs (initiated through simple commands) that perform diagnostics and system checks, and then the sequential operations required to properly complete measurements. This report describes the design of the control system and electronic components composing the DNI