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ANP PROlECT PROGRESS REPORT
The tube that failed and two adjacent tubes
were mounted intact and carefully ground to permit
examinations of their longitudinal cross sections
as seen against the direction of air flow. The
tube that failed is shown in Fig. 3.4.23. The
neckdown of the tube wall indicates a tensile
fracture similar to that observed2 in York radiator
No. 1.
Longitudinal cross sections of the two adjacent
tubes that were examined are shown in Figs.
3.4.24 and 3.4.25. Incipient fractures may be seen
in both these tubes. Three tubes were also taken
from corresponding positions on the air exit face
and prepared for examination in a similar manner.
Only one tube exhibited evidence of incipient
fracture, as shown in Fig. 3.4.26.
It is concluded that the radiator failed as a
result of the initiation of a fracture in a braze
alloy fillet by shear forces and the propagation
‘P. Patriarca et a&, ANP Qwr. Prog. Rep. Dec. 10,
1955, ORNL-2012, p 145.
of this fracture through the tube wall by tensile
forces or combinations of tensile and shear forces
during periods of cyclic operation. Since the
incidence of incipient fractures was associated
exclusively with the presence of support members
or plates, it is recommended that these transverse
restraints be removed entirely. This can be
accomplished, as suggested previously, by using
a high-conductivity fin to provide transverse
support at 2- or 4-in. intervals3 and modifying
the brazing procedure accordingly.
The tensile loading contribution to the York
radiator failure was attributed at the time of
examination to the restraining influence of the
support member, which extended up the side of
the radiat~r.~ In view of this conclusion, the
support members of subsequent radiators, including
PWA No. 2, were slit, as shown in Fig. 3.4.20,
3R. J. Grpy and P. Patriarca, Metallo raphic Ex-
ammation of ORNL HCF Radiator No. 1 Faifures, ORNL
CF-55-10-129.
Fig. 3.4.23. Longitudinal View of Opposing Walls of the Tube That Failed in Nak-to-Air Radiator PWA !
No. 2 as Viewed Against the Air Flow. Note neckdown at fracture. 75X. Reduced 22%.
192