LANL`s mobile nondestructive assay and examination systems for radioactive wastes

The ability to accurately and rapidly measure nuclear material within drums and examine their contents without having to unpack the drums saves time, reduces characterization costs and minimizes radiation exposure. Over the past two years, Los Alamos National Laboratory (LANL) has developed and fielded a suite of mobile nondestructive assay and examination systems for use primarily on its own transuranic (TRU) waste but that also have application to low level, mixed and hazardous wastes. It has become obvious that systems like these are generally useful and have applications at other Department of Energy (DOE) production and environmental technology sites. Mobile capabilities present a potential cost savings where waste drums have to be transported to a fixed NDA facility. In other cases they fill a void where there is no fixed facility available because construction costs are prohibitive (as in the case of small quantity sites) or the available facilities may not meet current or evolving safety standards. Rather than bringing waste to a facility to be characterized, one can bring the characterization capability to the waste. The three systems described are: (1) mobile radiography system; (2) mobile segmented/tomographic gamma scanner; and (3) mobile passive/active neutron assay system

Percolation and jamming in random sequential adsorption of linear segments on square lattice

We present the results of study of random sequential adsorption of linear segments (needles) on sites of a square lattice. We show that the percolation threshold is a nonmonotonic function of the length of the adsorbed needle, showing a minimum for a certain length of the needles, while the jamming threshold decreases to a constant with a power law. The ratio of the two thresholds is also nonmonotonic and it remains constant only in a restricted range of the needles length. We determine the values of the correlation length exponent for percolation, jamming and their ratio

Kinetics and Jamming Coverage in a Random Sequential Adsorption of Polymer Chains

Using a highly efficient Monte Carlo algorithm, we are able to study the growth of coverage in a random sequential adsorption (RSA) of self-avoiding walk (SAW) chains for up to 10^{12} time steps on a square lattice. For the first time, the true jamming coverage (theta_J) is found to decay with the chain length (N) with a power-law theta_J propto N^{-0.1}. The growth of the coverage to its jamming limit can be described by a power-law, theta(t) approx theta_J -c/t^y with an effective exponent y which depends on the chain length, i.e., y = 0.50 for N=4 to y = 0.07 for N=30 with y -> 0 in the asymptotic limit N -> infinity.Comment: RevTeX, 5 pages inclduing figure

Experience operating LANL`s passive/active neutron (PAN) assay system

We present a summary of our operating experience with LANL`s mobile PAN assay system, which was acquired from the Carlsbad Area Office in 1994, refurbished, calibrated, and fielded for the first time on LANL`s TRU waste in the winter of 1996. It is functionally identical to other PAN systems throughout the DOE complex and its software is the same as at INEL. Since Jan. 1996, it has passed the first round of the Performance Demonstration Program and has been used to assay several hundred drums of LANL`s TRU waste. Difficulties in assaying homogeneous wastes with high ({alpha},n) neutron fluxes and experience in assaying debris waste in both active and passive PAN modes are reported on

Preparation of the First Shipment of Transuranic Waste by the Los Alamos National Laboratory: A Rest Stop on the Road to WIPP

The Los Alamos National Laboratory (LANL) achieved a national milestone on the road to shipping transuranic (TRU) waste to the Waste Isolation Pilot Plant (WIPP) when it received certification authority on September 12, 1997. Since that time, LANL has been characterizing a non-mixed TRU waste stream and preparing shipments of this TRU waste for disposal in the WIPP. The paper describes the TRU waste identified as waste stream TA-55-43 Lot No. 01 from LANL Technical Area-55 and the process used to determine that it does not contain hazardous waste regulated by the Resource Conservation Recovery Act (RCRA) or the New Mexico Hazardous Waste Act (HWA). The non-mixed determination is based on the acceptable knowledge (AK) characterization process, which clearly shows that the waste does not exhibit any RCRA characteristics nor meet any RCRA listing descriptions. LANL has certified TRU waste from waste stream TA-55-43 Lot No. 01 and is prepared to certify additional quantities of TRU waste horn other non-mixed TRU waste streams. Assembly and preparation of AK on the processes that generated TRU waste is recognized as a necessary part of the process for having waste ready for shipment to the WIPP