This document details activities of the N-Reactor Department during the month of March 1963.

The loss associated with low goaling rupture-prone material is quite small compared to the benefits. There is an optimum goal exposure for a given metal quality. At this optimum exposure the loss associated with irradiating rupture-prone material is minimized. Reasonable decision rules are as follows: Discharge, at the first opportunity, tubes containing rupture-prone material whose exposures are equal to or greater than 50 percent of normal goal. Discharge tubes under 50 percent of normal goal which would be expected to reach 70 percent of normal goal before the next scheduled outage. Irradiate all tubes containing rupture-prone material whose exposures will not be expected to exceed 70 percent of normal goal before the next scheduled outage. Discharge all tubes containing rupture-prone material, regardless of exposure, if an additional rupture is incurred in the lot. Return unirradiated rupture-prone material to Production Fuels Section as reject material.

The scheduled termination of PT IP-659-AC, presently being irradiated in F Reactor, will result in discharge of 105 columns of enriched uranium (0.947 w/o U-235) at less than 50 per cent of the goal exposure. The test block is currently scheduled to be replaced with natural uranium columns. Since F Reactor is on a semiblock discharge plan (alternate rows), subsequent operating plans would require that 64 of these replacement columns of natural uranium be likewise discharged during the scheduled outage in May of 1964 at less than 50 per cent of goal. It appears desirable to minimize the economic costs of the production test by an alternative discharge scheme (e.g., interim poison irradiation). The objective of this supplement is to soften the economic impact of low exposure fuel discharge scheduled by IP-659-AC and simultaneously to obtain a useful alternate product by irradiating nine columns of Li-Al and Bismuth in a ``striped`` charge.

Heat discharged to the Columbia River in reactor cooling water is one of the more important pollutants from Hanford operations. The effect of this heat on river temperatures has been studied for several years, primarily because of the potential effect on the Columbia River fisheries. This document presents a summary of recent river temperature experience, with comparison data for a better perspective.

A design was developed for leading thermocouples from a high-temperature, pressurized water reactor-coolant system of such integrity that no reactor shutdowns were caused by its use. Using this design, measurements of the fuel-element-cladding temperature and its variation with time were made in three tests on elements clad in type X-8001 aluminum alloy. The following conclusions were reached from the test results: (1) the cladding temperature of a fuel element operated at low heat flux in high bulk-outlet temperature water did not increase with time and was slightly lower than predicted by the Sieder-Tate equation; (2) cladding temperatures of fuel elements operated at high heat flux in either high bulk-inlet or outlet temperature water increased 40 C higher than predicted by the Sieder-Tate equation with initial temperatures equal to the predicted temperatures; and (3) the rate of temperature increase appeared dependent only on fuel-element heat flux and location with respect to the front and rear faces of the reactor.

This report is divided into: present reactor fuel production, NRD production fuels, N fuel development, and current reactor fuel development.