Brookhaven National Laboratory Annual Report: 1957 Page: 58
xxxvii, 149 p. : ill. ; 30 cm.View a full description of this report.
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58
nal piping, structure, exchanger, cooler, furnace,
etc. The loop will convey a solution of U-Bi-Zr-
Mg through a pipe in the BNL reactor at a rate
of a few gpm. Since U235 will be used in the bis-
muth, fission will take place. The loop will be used
primarily to determine the corrosion behavior of
various steels in the presence of radiation (neu-
trons and fission products). Samples of steel and
graphite inserted in the loop will be studied for
other radiation-induced changes. A high level
facility for examining radioactive specimens is
being designed. This unit should permit exami-
nation of all the components of the above loop.
Equipment for operating, examining, and testing
is either on order or being developed for this hot
facility.
In addition to the above, a few smaller thermal
convection loops were constructed for salt corro-
sion work. Also, a large number of loops were
operated by the Metallurgy Group; these are
discussed in the following section.
Corrosion and Mass Transfer
The thermal convection loop program has been
expanded and has yielded very valuable, if in-
conclusive, results. Some 40 loops have now been
run in which the upper temperature of the hot leg
has been held at 5500C and the temperature
differential between hot and cold leg has been
varied between 400 and 1500C. The test ma-
terial in most of these experiments has been a low
chrome steel (21/% Cr-1% Mo-0.4% Mn). The
results of these tests may be summarized as follows.
If the zirconium and magnesium concentrations
in the uranium-bismuth alloy are maintained at
approximately 250 and 360 ppm respectively, these
loops will run for very long times without plug-
ging, i.e., such loops have been shut down after
13,000 hr without having formed a solid plug in
the cold leg. However, after 3000 to 5000 hr of
thermal circulation the hot leg is seen to have
been attacked quite severely. This attack which
apparently progresses with time, is referred to as
pit type corrosion for lack of a better descriptive
term. Actually, the pits extend laterally as well
as in depth, although to date no loop has been
perforated as a result of corrosion. With tem-
perature differentials of the order of 90 C (5500 to
4600) the severity of attack is markedly reduced.
Very little deposition is noted in the cold leg. With
temperature differentials above 100 oC (5500 to450) the type of attack described at ove is noted.
The welds, which in these early loot:s were made
with a 5 chrome welding rod, were tlso severely
attacked. When calcium is substitute I for magne-
sium as the deoxidizing agent, loc ps plug in a
much shorter time. Of all the loops run to date,
the one giving the most favorable re ults, i.e., no
pit type corrosion and very little p ecipitation,
was of Bessemer steel. This loop operated for
12,000 hr at a temperature different :al of 135 oC.
The newer loops, started in the pa t fiscal year,
are being run to test some ideas evolved as a result
of the previous runs. In particular, ' he tempera-
ture differential is being varied betwi en 100 and
125 C, the upper temperature being either 550,
525 , or 500C. The effect of heat reatment of
the test material on the behavior unc er operating
conditions is also being tested. The e: Tect of using
different types of welding rods to joi l 2/ chrome
is also being tested. Finally, the effect_; of nitriding
the steel prior to test and of varying tl e concentra-
tion of inhibitors are also being deti rmined. Al-
though these loops have run only fo about 3000
to 5000 hr, which is too short a tim for conclu-
sions to be drawn, most of them ha re shown no
corrosion in the hot leg and very lit le precipita-
tion in the cold leg as determined by adiography.
However, one result obtained is anon alous in that
a new batch of steel of the same genm ral composi-
tion has shown the development of pits both in
the weld and in the pipe wall prior 1 imposition
of the temperature differential. T lis loop had
been given an annealing heat treat nent, which
may have been a factor in its behav: or, although
it has been suspected for some tim that slight
variations in composition of the steel nay be suffi-
cient to give the observed poor resis ance to cor-
rosion.
The fourth run on the electroliaagnetically
pumped loop (referred to in last y-ear's report)
has been completed. The loop was sl!ut down be-
cause of a plug which formed as a res It of a power
failure after 2500 hr of operatioI at 5500 to
4000 C. Examination of the loop sho' red extensive
corrosion in the region operated a ove 500oC.
A large amount of deposit was found in the finned
cooler section (coldest section). However, the plug
which cut off circulation was due to localized
precipitation of zirconium, magnesi im, and ura-
nium. Two other loop runs have bee,-i completed,
one with Loop G, a mechanically pu aped loop, in
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Brookhaven National Laboratory. Brookhaven National Laboratory Annual Report: 1957, report, December 1957; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc67224/m1/100/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.