In the last two or three years there has been a notable improvement in the knowledge and understanding of reactor lattice physics. During this interval, measurements of parameters have been improved and the methods of analysis have been greatly strengthened. It has become apparent that the classical ways for computing the lattice parameters are not sufficient. It is the purpose of this report to publish under one cover as much of the most recent information as possible.

The Biology Operation, Hanford Laboratories, required plutonium dioxide particles in five different micron and sub-micron size ranges. These were to be supplied as a water suspension in small containers. It was necessary to design equipment, suitable for hood operation, which would give a satisfactory separation of these particles.

In the continuing search for better methods of effecting the secondary fusion welded closure in Alsi bonded aluminum clad uranium metal fuel element, an article on "The Twin-Argon Welding Process" by J. A. Donellon was recently found in the September 1954 issue if the British Welding Journal. From a review of the article, the process appeared to have enough possibilities to warrant exploring it. Communication were established with the General Electric Company, Ltd..

Investigation of aqueous and steam corrosion at elevated temperature has been carried on at Hanford for several tears. A number of reports have been published on various phases of the corrosion program but, except for monthly reports, little has been written on the progress of the Corrosion and Coatings Operation alloy development program. This interim report will outline the more important current phases of the aluminum alloy program.

At the present time, high-radioactivity-level wastes at Hanford are neutralized and stored as liquid in underground tanks lined with mild steel. This method of storage is relatively inexpensive and is satisfactory on a short-term basis. However, on a long term basis, liquid storage is less desirable than solid storage because of the greater mobility of the liquid. In addition, storage as aa solid would significantly reduce the volume of waste stored. Consequently, various research and development studies have been undertaken in an attempt to develop a practical waste solidification.

The purpose of this document is to describe the design and construction of a full-scale, electrically-heated model of a 19-rod PRTR fuel element for use in heat transfer experiments.