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11-30-64
RADIOJISOTOPE SHPÉPING-CONTAINER DEVELOPMENT*
.. K. W. Haff
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Conf-641201-13
Oak Ridge National Laboratory
Oak Ridge, Tennessee
MISTERI
The results of a series of structural and fire tests on the fire and
impact shield designed for the Oak Ridge National laboratory radioisotope
shipping containers are presented here. This work is being conducted by
the Isotopes Development Center at ORNL as a part of its program to con-
tinually improve its shipping procedures and packaging. Since 1946, the
beginning of the radioisotope program, more than 180,000 shipments contain-
ing -2.2 million curies have been made without a single accident in which
a significant release of radioactivity was involved. However, with the
trend in radioactive material shipments to larger curie content per package,
the need of greater safety in package design has become essential.
For radioisotope shipping carriers weighing up to wi.25 tons and which
are ~20 in. in dia., a low-cost fire and impact shield was designed and
tested which will meet the packaging requirements given in the new federal
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regulation 10 CFR 72, il étably the fire requirement and the 30 foot free
fall requirement. The shield is constructed of 3-5/8-in.-thick maple (finished
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4 in. lumber) (Figure 1) with mitered corners of nailed construction. A
mild steel frame holds the shield intact under impact conditions. The frame
is made of l-in. steel straps and 1.5-in. steel angle iron for the small
shields and up to 2.5-in. straps and 3-in. angle iron for the largest shields.
The top is hinged for removal of the container.
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*Research sponsored by the U. S. Atomic Energy Commission under contract
with the Union Carbide Corporation.
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The smallest shield tested weighs 120 lb.; it measures 14 x 14 x 17-3/8
in. and holds a 60-lb. lead-shielded steel shelled container that has 1.5-in.
shielding. The largest, shield weighs 570 lb.; it measures 28-3/8 x 28-3/8 x
36-1/4 in. and holds a 2600-lb. container with 8-in.-thick lead shielding.
The design of the fire and impact shield as shown in Figure 1 has
evolved from a series of tests performed on several different types of
shields and kinds of wood. In the first series of tests, the resistance
to fire of various kinds of wood was evaluated.
The tests are designed
to duplicate to some degree the time-temperature conditions of a standard
l-hr. fire test as defined by the National Fire Protection Association
(NFPA Sulletin No. 251) and ASTM-E119-61.
Maple, pine, and hickory were exposed
for 1 hr. to the flamesoſ a
pressurized kerosene burner. The outside temperature was maintained at
900 + 50°C to duplicate the maximum temperature of the standard l-hr. fire
test. Maple showed only a 2-in. penetration vs 2.5 to 3 in. for pine.
Considering the strength, availability, insulating properties, and cost,
maple was the best wood to use. Maple, however, was not as good an insula-
tor as pine, since the maximum temperature inside the pine shield rose
only 30°C, and inside the maple shield it, rose 60°C during the 1 hr. test.
Hickory was not available in the thicknesses and widths needed and is no
less expensive than map.le. As a result of these tests, maple was selected
as the material for use as a shield.
Each shield was instrumented with two thermocouples -- one on the
outside surface and one in the interior cavity -- which were connected to
a 10-point Brown recorder. The fire shield was placed in a sheet metal
enclosure and heated with a pressurized kerosene burner.
The burner was
manually moved toward the shield at a rate that caused the rate of tenpera-
ture increase indicated by the exterior thermocouple to conform to the
standard 1-hr. fire test specifications.
Three wooden shields were fire tested in this manner. The first shield
(external dimensions 24 x 24 x 24 in., thickness 4 in. j was constructed of
2- by 4-in. pine stacked vertically around the cask cavity and was bolted
together with 1/2-in. bolts spaced 4 in. apart. The pine shield withstood
the l-ħr. fire test successfully. Exterior temperatures were ~1000°C, and
the maximum interior temperature at the end of the test was 140°C. At the
completion of the test, the wood was charred to a depth of ~3 in. in the
area of direct flame impingement, and other areas were charred to a depth of
wl-1/2 to 2 in. The fire in this shield was not completely extinguished at
the end of the test, and ~3 hr. later the entire shield was completely burned.
It was observed during the test thai the wood burned much more rapidly
when the flame impingement was parallel to the grain than when perpendicular
(Figure 2). All future wooden fire shields were designed to minimize the
area of flame impingement parallel to the grain of the wood.
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A secoud shield, used in routine radioisotope shipments and constructed
of 3/4-in. aluminum-clad plywood reinforced with aluminum angle on the corners,
was tested. The isotope shipping cask was removed from the wooden box for
this test.
The aluminum cladding began to buckle after 30 sec. exposure to
the flamme and was completely melted after 45 sec. exposure (melting point
of Al = 659.7°c). Temperature at the outside surface of the shield was held
at 900°C + 50°C. The maximum interior temperature was 40°C for 20 min., at
which time the shield burned through. The glue between laminations of the
plywood ceused the layers to crack and split when burned through, thus reducing
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the layer of insulating charcoa). on the outside. For this reason, this
particular plywood is not considered a good fire shield material.
ke
In the second series of tests an attempt was made to differentiate
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between the practicality of using a fabricated wooden shield with a steel
angle iron frame for support and a solid wood block with space drilled out
to hold the radioisotope shipping cask. In this series of tests, two
wooden fire and impact shields were built. The first type was built of
4- by 16-in.-thick white pine with outside dinensions of 19 x 19 x 19 in. and
a finished wali thickr.e88 of 3-5/8 in. The side corners were mitered and
nailed together and were protected with a 1-1/2-in.-wide angle iron frame.
The top and bočtom were purposely attached with the end grain of the wood
exposed to determine the difference in burning rate of end grain and per-
pendicular grain. Two of these shields were built and each shield was
instrumented with a thermocouple on the inside surface of the wood wall
and another thermocouple on the outside surface of the wood wall.
Each of the shields was exposed to the flame of a pressurized kerosene
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burner. The temperature on the outside was held at 900°C + 50°C for 1 hr.
by manually adjusting the position of the burner. Inside both shields, the
temperature remained at 15°C for the first 50 min. of the fire test. In the
remaining 10 min. of the test, the temperature rose to 25°C in one shield
and to 30°C in the other. Charring occurred to a depth of ^2-5/8 in. on the
side of each shield where the direction of flame impingement was perpendicular
to the grain of the wood and to a degth of ~3 in. on the top and bottom edges
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where the flame was parallel to the grain. The flame did not penetrate the
shield during the test.
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The second type of fire and impact shield tested was built of a solid
piece of 14 x 14 x 14 in. douglas fir with a 6-in.-dia. hole drilled in the
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center to hold a small cask. The top was constructed of 14 x 14 x 4 in.
douglas fir and was attached to the main body with four counterbored lag
screws. Three shields of this type were dropped from a height of 15 ft.
onto a solid concrete floor. Shield No. 1, when dropped onto a top corner
at an angle of -20°, split in half, and the small lead container on the in-
side of the shield fell out (Figure 3). Shield No. 2 was dropped onto one
of its vertical side corners. A strip, 2 by 5 in., was broken off one cor-
ner (opposite the point of impact) and a lag screw was exposed. Another
split, ~1/2 in. deep, occurred on another corner opposite the corner of
impact. Shield No. 3 was dropped on its bottom, and a strip 2 by 1 in.
split off the top corner upon impact. Two other cracks, one ~2 in. deep
and the other ~1-1/2 in. deep, appeared on the sides of the shield.
Shields No. 2 and 3 were submitted to a l-hr. fire test with instrumenta-
tion and test conditions the same as described previously. The inside wall
temperature increased from 0 to 15°C for shield No. 3 and from 0 to 30°C for
Shield No. 2 in 1 hr. No damage to the small lead cask inside the shield
occurred. In the area of the cracks, the shields were charred nearly
through the entire depth, but the lead casks were not damaged.
The shields for the third series of tests were designed using the
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knowledge gained from the first two series but using maple. (This was the
shield shown in the first figure.)
• ' Two wooden fire and impact shields fabricated of 3-5/8-in. thick maple
with mitered corners, nailed construction, and a mild steel frame to hold
the entire shield intact, were tested.
The shield weighed ~120 lb. and was
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loaded with four lead bricks weighing -28 lb. each, for a total weight of
234 1b. The first shield was dropped from a height of 15 ft. onto a 6-in.-die.
piston, fastened to a pad consisting of a 12- by 12-ft. piece of steel armor
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plate 4.5-in. thick, backed up by a 5-ft.-thick slab of reinforced concrete.
Below the pad was a 3-ft. dia. reinforced concrete column reaching down ~7
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ft. to bedrock and extending 3 ft. into the bedrock. The pad was considered
to be unyielding. There were no broken welds or cracking or splintering of
the wood. The hinges on the top of the box were sprung but not broken, and
the steel bracing on the bottom of the shield was slightly bent. The shield
was then dropped from 30 ft. onto a 6-in.-dia. piston. The damage to the .
impact area of the shield was only slight; the steel frame was bent inward
~1/2 in., and one weld was broken. The hinges on the top of the shield
straightened ~1/2 in., but there was no cracking or splintering of the
wood (Figure 4).
The second shield in the third series was dropped from 30 ft. onto one
of its bottom corners at an angle of w45°. As is seen in Figure 5, this
shield suffered only negligible damage. The corner of impact was slightly
bent and the bottom brace was bent outward ~1/4 in. However, there were
no broken welds or cracking and splintering of the wood.
The two fire shields were subjected to a l-hr. fire test after the impact
tests. Each shield was instrumented with two thermocouples -- one on the out-
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side surface and one in the interior cavity. The shields were placed in a
sheet metal enclosure and heated with a pressurized kerosene burner, which was
manually positioned to maintain a constant outside temperature of 900 = 50°C.
A 1/8-in.-thick perforated steel plate was placed on the bottom of one
shield to test the value of this device as a flame deflector which would dis-
tribute the heat while allowing the volatile constituents contained in the
wood to escape and be burned in the air. One corner joint on this shield was
assembled with epoxy cement rather than nails to evaluate this type of construc-
tion.
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Due to operational difficulties with the burners prior to the testt,
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more kerosene was consumed than had been expected and the fuel was exhmusted
after 45 min. of testing. Both shields were allowed to burn in air fox 30
min. while more fuel was obtained. During this 30-min. shutdown, the tempera-
ture inside the shield behind the flame deflector rose from 30 to 55°C. The
temperature inside this shield at the completion of the test (1 hr. tottel
kerosene burner operation) was 90°C. The temperature inside the other
shield at the completion of the test was 60°c.
At the completion of the test, the fire was extinguished with a water
spray and the shields were inspected. The use of the flame deflector did
not appear to be effective since the fire penetrated the wood to a deptah of
m2 in. in both shields; however, the screened area did burn more evenly. The
glued corner joint failed and separated during the test (Figure 6), but the
nailed joints remained intact. There was no damage to the lead bricks con-
.--"em
tained inside both shields.
The fourth and final series of tests was conducted on a shield similar
to but larger than the ones discussed previously. The largest size proposed
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for use at ORNL was tested. Maple was selected as the wood because it 38
easily obtainable in the southeastern section of the United States.
Thus
shield weighing 570 lb. was designed to carry a cask with 8 in. of lead
shielding weighing ~2600 lb. For the tests 2600 lb. of lead bricks were
placed inside to simulate the weight of the cask.
In the first test, the shield was dropped from 30 ft. onto an edge
The damage was minimal.
This shield was then sent to Underwriters! Laboratories for fire test-
ing in their safe-testing furnace. The shield was subjected to the standard
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l-hr. fire test as outlined in ASTM-E119-61. During the test approximately
one-half of the wood burned away and the maximum temperature reached in the
lead inside the shield was 200°F. Complete details of this fire tesį vare
published by Mr. L. Horn (2.) of Underwriters' Laboratories.
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LEGAL NOTICE --
Two report wo mopure un account of Commen uponored wort, .olcher the Uwund
damo, nor the counton, sor my person acting a ball of the Coaneros:
1. Saken my wuruly or reprimtadon, proud or inaund, nu respect to accu.
pay, completi, or wohlcuni 'Worada continuo report, or that uw we
ol wy taloration, appuntos, mehed, or procou dlecloud In this report wy hot latring
privately owned righwa; or
B. Asmunas wywabtuvos muros act to who we of, or lor damage rond de trou the
w ol w laboration, apparte, muhod, or procon decloud laws report.
As du do bom, "mro Kun og ball of the Commuta" ucludm my .
piogne ar contractor of K Cougastos, or duploys of much contractor, how extent that
inch toploys or contractor of the Coualaiku, or oployee of much coairclor propre.
duwutmain, or prortons secolo, muy taformation purul to his deployment or contract
will the cou doskou, or No employment will need coatractor.


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Literature Cited
1. L. Horn, Underwriters' Laboratories, 200-277, March, 1964.
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DATE FILMED
-3 / 19 /65


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"IMPID
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LEGAL NOTICE
This report was proparod as an accourt of Govornmont sponsored work. Neither the United
Statos, nor the Commission, nor any porson acting on behall of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completoners, or usofulnost of tho Information containod in this roport, or that the use
of any Information, apparatus, method, or process disclosod in this roport may not infringe
privately owned rights; or
B. Assumos any liabilities with respect to the uso of, or for damages resulting from the
use of any information, apparatus, mothod, or procoss disclosed in this report.
As used in the above, “por son acting on behalf of the Commission" includes any om-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor propares,
disseminates, or provides access to, any Information pursuant to his employment or contract
with the Commission, or hio employment with such contractor.

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