January, 1956 Report on the Inspection of the First Raleigh Research Reactor


On January 12, 1956, an opportunity arose at Oak Ridge
National Laboratory
for a meeting of representatives of several
groups to discuss the results of the ORNL inspection of certain dis-
reactor components, and in particular to hear information
and recommendations concerning steps that might be taken to avoid
in the future reactor the various corrosion problems of the first
reactor. Any appreciable corrosion presents a severe health and
safety problem.

Personnel Present

A meeting was arranged through Dr. K. Z. Morgan who, un-
, was called away by an emergency just before the meeting
started. Those present were as follows:

Ed BohlmanW. H. BehrmanC. C. CardwellF. P. Pike
Arnie Olson(for H. M. Roth)William Foley
George E. MooreDurand

Inspection Procedure

The core was stuck so tightly that the aluminum jacket
had to be cut and torn away. The core was then quartered longitudin-
in such a way as to do the least possible cutting of the coils
inside. Six metal pieces were then cut from strategic areas. From
each piece a number of metallurgical samples were taken for careful

Major Findings

[page 2]

Diagnosis of Core Failure

It was agreed by all that the corrosion was the consequence
of the high chloride content (>200 ppm). Pitting is characteristic
of chloride attack on stainless steels under comparable conditions
(oxidizing media), as is also the location just above the solution

It was not characteristic that the corrosion outside
should be so much more extensive than inside, particularly since
on the outside the solution contact with aluminum should have given
protection. The metallurgists were at a loss for a possible ex-
of this anomalous behavior.

The localization of all pits within a 2 inch streak was
also puzzling. However, while no one could say why this occurred,
there was no lack of possible explanations. It could readily have
derived from some past incident, such a a linear occlusion before
or during rolling. Another suggestion was that the welder could
have accidentally struck an arc there.

[page 3]

Diagnosis of the Coil Corrosion

It seemed clear that the coils failed because of the
corrosive action of the cooling water, probably through the action
of chlorides.

Corrosion Resistance of Alloys

There was no information on corrosion resistance under
exactly our conditions. Most of the available information pertained
to uranyl sulfate solutions under more severe conditions of temperature
and solution velocity. One conclusion was that the net effect of
the simultaneous presence of hydrogen, oxygen, and peroxide was
that of an oxidizing solution.

By extrapolation of available (classified) data, these deductions were

NickelNo good.
IncoloyQuite good at high temperature.
NionelNo information, but question the
high nickel content.
Chlorimet 3Much too high in nickel.
Carpenter No. 20Probably O.K.
Hastalloy CNot bad, almost as good as 347.
Stainless 316Poor.
Stainless 347Reasonably good, but not very good.

For sulfuric and other acids on Stainless 347, data
are available from unclassified sources. We were referred to C. P.
as a start.

Recommendations for the Core

[page 4]

It is pertinent that the Babcock and Wilcox metallurgist
said that it was their experience that chloride was a severe danger
for Stainless Steels, and that there were a small but disturbing
number of instances where stainless equipment had become accidentally
contaminated with chloride between early fabrication and first use.
Usually the cause of the contamination remained unknown. To combat
this situation, they have frequently adopted a procedure of flushing
with trisodium phosphate before items are permitted to leave the
plant. A check by the receiver before the use was considered only
common sense. In important cases of interest to them, they would
insist upon a camera recording of the welding operations, and on
the storage of suitable metal samples.

Recommendation for the Cooling Coil

In some way the cooling water must be made less corrosive.
If the cooling water is used once, then discarded, it must be chemi-
treated, such as in accordance with the suggestions of our
Sanitary Engineers. Alternately the cooling water loop could be
isolated by a heat exchange unit, and distilled water used as the
media. The closed loop was apparently the preferred alternate of
those present.

The decision to adopt a closed-loop of distilled water will
not be a simple one. The decomposition of water into hydrogen and
oxygen will be a hazard that might be aggravated by the purity. The
circulating water should be monitored and maintained at a specified
specific resistance, which would be about 1/4 million reciprocal ohms
if there are no corrosion inhibitors or agents to reduce the
radiation damage to the water.