This report is a summary of the neutron attenuation data which have been obtained at the Brookhaven shielding facility on a mock-up of the fuel-rod-unloading plug used in the KAPL Reactor. Before this program was initiated, a number of small scale tests had been made in the ORNL lid tank on carbon steel mock-ups of components of the rotating plug. The results of the tests indicated considerable neutron streaming through the vertical steel and air members of the plug. However, the lid tank source strength and dimensions did not permit the tests to be extended to the full plug height. In view of the concern aroused by the ORNL tests and the absence of fundamental information on the transmission of neutrons through steel and the addition height (12') available here resulted in a request for BNL to construct and test a mock-up of a sector of the SIR top plug in accordance with KAPL specifications.

We have recently completed measurement of resonance escape probability in the BNL reactor and in several slightly-enriched uranium light water moderated lattices. In addition, WAPD has made available to us data from other slightly enriched uranium-water lattices, so that about 18 lattices in all have been done.

Radiation damage to graphite has several consequences of practical importance. The growth of graphite under radiation (Wigner's disease) in production reactors has always been a serious concern. The thermal conductivity of graphite decreases greatly with time of irradiation and is important in long range studies of reactor temperature problems.