that we believe were caused by seawater that entered
the helium release vents when the sphere wasfirst
submerged. The defects appeared to be ruptures ad-
jacent to the external closure weld. The inside of the
cladding showed corrosive attack along grain boun-
daries, sometimes penetrating to 30% of the wall
thickness, presumably caused by the seawater, but
metallography of typical specimens showed no
evidence of sodium chloride. The plutonia sphere
showed no sign of corrosion. Probably, sudden immersion of the hot FSA caused water penetration
through the vents in the cladding and the water and
the salt residue, together with the high temperature
and intense alpha and gammairradiation caused
chemical attack and disintegration of the iridium
cladding from within.
VI. BEHAVIOR OF CAPSULE MATERIALS
IN AQUATIC ENVIRONMENTS
_ (George M. Matlack, Gilbert B. Nelson, and James
H. Patterson)
Heat source capsule materials were immersed in
simulated seawater at 23° for 1 to 3 yr, then examined for corrosion of the surfaces and of boundaries
between dissimilar metals. The materials tested
were molybdenum, T-111 alloy, Pt-20Rh, and Ta-
10W. Molybdenum sheet, after immersion for 1 yr
showedno corrosion other than deposition of crystals
containing elements present in seawaterand a slight
increase of the molybdenum concentration in the
water. Couples formed of T-111, Pt-20Rh, and Ta10W showed nogross corrosion after 3 yr of immer-
sion, and none of the elements was found in the
water. There were very thin layers of a dark
amorphoussubstanceat the contact boundaries, and
in all instances these layers were composed chiefly of
manganese, also presentin the seawater. These capsule construction materials seem to remain uncorroded for up to 3 yr of immersion in seawater.
VII. BEHAVIOR
OF
SIMULATED SEAWATER
(Zr,U)
FUEL
IN
(George M. Matlack)
were immersed for over 2 yr in simulated seawater.
One sample from a Hastelloy-N clad fuel rod was
immersed for 20 months, and a similar sample, ex-
cept that it was from an unclad rod, was immersed
for 25 months. Neither underwentanyvisible change
in the luster of its cut surface; fine burrs and saw
marks were unchanged. The radioactivity in the
water became twice normal background within a
week after sample immersion and did not increase
thereafter. The activity was mainly !°’Cs, with a
minorfraction of ©°Co activity from the clad sample.
The excellent stability of this fuel in seawater was
also confirmed by ocean exposure tests conducted at
San Clemente Island by the Naval Undersea Center.
REFERENCES
1. W. W. Weir, Soil Science (J. B. Lippincott Co.,
Chicago, 1949), p. 132.
2. D. Rohr, LASL, private communication.
3. M. W. Nathans, LFE Environmental, Richmond,
CA, private communication.
4.
J. H. Patterson, G. B. Nelson, and G. M.
Matlack,
“The
Dissolution
of
78Pu_
in
Environmental and Biological Systems,’’ Los
AlamosScientific Laboratory report LA-5624 (1974).
5. O. G. Raabe, G. M. Kanapilly, and H.A. Boyd,
“Studies of the In Vitro Solubility of Respirable Particles of 2°8Pu and 78°Pu Oxides and an Accidentally
Released Aerosol Containing 78°Pu,” in “Lovelace
Foundation for Medical Education and Research,
Inhalation Toxicology Research Institute Annual
Report” LF-46 (1973), pp. 24-30.
6. B. O. Stuart, “Comparative Distribution of “°8Pu
and “9Py in Rats Following Inhalation of
the
Oxide,” Battelle Northwest Laboratories report
BNWL-1050 (1979), pp. 3.19-3.20.
7. J. Hudson, “Analysis of Microsphere Debris,” in
“Sandia Laboratory Quarterly Report, Aerospace
Nuclear Safety Program, April 1, 1968,” report SCPR-68-451, pp. 34-36.
Two irradiated, enriched uranium SNAP fuel
samples, each a 6-mm-thick section of ZrH-10 U
(93° enriched 2351), cut from a full-size fuel rod,
15