الفهرس 
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Abstract
The purpose of the present investigation is to study the thermal behaviour of the First Egyptian Research Reactor core when there is a drop or El complete stoppage of the cooling flow. It is an experimental and theoretical investigation.
To start with, it was necessary to study the behaviour
of the reactor under normal operating conditions. For such study, knowledge of the coolant flow distribution, thermal flux distribution ~nd the fuel percent burn-up was necessary. The latter was evaluated by following the complete history of each fuel basket in the core from the day the reactor started working in 1961. Both the thermal flux distribution and the coolant flow distribution we~e taken from available reports and reactor design catalogues.
Different models were developed to calculate the temperature distribution in the reactor core. The distribution was incorporated both inside fuel and on clad surface, in addition to bulk coolant. These calculations were made for both a fresh core and the core in its present condition. Appreciable differences were noticed between the results obtained from the different models.
For a fresh core, the clad surface tempereture was higher by
about 15% than the present core under the same operating conditions.
. The differences in the results obtained from the models necessitated carrying out an experimental investigation to find the appropriate one. The experimental study was carried out
using an instrumented fuel basket equi~ped wi~h 9 the~GOcouples. Seven of these thermocouples were inst~lled in the cladding of two fuel rods representing the best an~ the worst cooling conditions in the basket. The two others were for measuring the inlet and outlet temperatures of the coolant flow to the basket.
Several basket locations in the reactor core were investigated to get a rather complete picture of th~ temperature distribution, and to check the hottest core location needed for the flow reduction experimental work.
Comparison of the experimental results with the theoretical c$lculations indicated that one of the models developed, which takes into consideration the fuel bundle as a whole, best represents the actual conditions. The hottest core location, which was proven experimentally and an~lytically, was found to lie in the third ring from the core centre.
This proven model was used for evaluating the fuel temper-
conditions when the coolant flow changes in the hottest core location of the core. The theoretical results were verified by an experimental study to check the thermal behaviour of the reactor the flow was reduced.
An ICL-~RTRAN code was developed based on the proven theocretical modal to calculate all the temperature and flow d1stribuin the reactor core. The code could be used for other