A study to determine the feasibility of containing the fission products of a mobile reactor in the event of an impact is presented. The model simulated the reactor core, energy absorbing gamma shielding, neutron shielding and the containment vessel. It was impacted against an 18,000 pound reinforced concrete block at 1055 ft/sec. The model was significantly deformed and the concrete block demolished. No leaks were detected nor were any cracks observed in the model after impact

Puthoff, R. L.

English

NASA Technical Reports Server

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A 1055 FT/SEC IMPACT TEST OF A TWO FOOT DIAMETER
MODEL NUCLEAR REACTOR CONTAINMENT
SYSTEM WITHOUT FRACTURE
by Richard L. Puthoff
Lewis Research Center
Cleveland, Ohio
June, 1972
https://ntrs.nasa.gov/search.jsp?R=19720020071 2020-03-23T11:52:33+00:00Z
A 1055 FT/SEC IMPACT TEST OF A TWO FOOT DIAMETER
MODEL NUCLEAR REACTOR CONTAINMENT
SYSTEM WITHOUT FRACTURE
by Richard L. Puthoff
Lewis Research Center
National Aeronautics and Space Administration
Cleveland, Ohio
ABSTRACT
S? An impact test was conducted on a 1119 pound - 2 foot diameter sphere
05
<f model at the Holloman Sled Track in Alamogordo, New Mexico, This test
is part of a study to determine the feasibility of containing the fission products
of a mobile reactor in the event of an impact,, The model simulated the re-
actor core, energy absorbing gamma shielding, neutron shielding and the
containment vessel. It was impacted against an 18,000 pound reinforced con-
crete block at 1055 ft/sec. The model was significantly deformed and the
concrete block demolished. No leaks were detected nor were any cracks ob-
served in the model after impact.
A 1055 FT/SEC IMPACT TEST OF A TWO FOOT DIAMETER
MODEL NUCLEAR REACTOR CONTAINMENT
SYSTEM WITHOUT FRACTURE
by Richard L, Puthoff
Lewis Research Center
National Aeronautics and Space Administration
Cleveland, Ohio
*
S SUMMARY
COI
Future applications of nuclear energy may require the use of a mobile
nuclear reactor. Fission products in mobile reactors must be contained
with the same level of confidence as in stationary powerplants. One method
for containing fission products in the event of an impact of a mobile reactor
is to put the reactor in a containment vessel and design the containment
vessel and its contents to absorb the impact energy without rupturing the
containment vessel.
A previous set of five tests was conducted at Sandia Corporation on
two-foot diameter mock-up models of a reactor containment vessel system.
The models weighed from 350 to 1305 pounds. They were impacted at speeds
from_241 to 580 feet per second. No leaks were detected nor cracks ob-
served on any of the models after impact. Examination of the models indi-
cated-a potential for survival at impact speeds of 1000 feet per second^
. A-new series of tests were then planned with impact velocities up to
1000 ft/sec. The first test model of this series was impacted at 640 ft/sec.
This report describes another test conducted at 1055 ft/sec impacting against
an 18,000 pound reinforced concrete block. The model weighed 1119 pounds.
It simulated the reactor core, energy absorbing gamma shielding, neutron
shielding and the containment vessel.
Observations made from the results of this test included
(1) No leaks were detected nor cracks observed on the model.
(2) The concrete block, was totally destroyed at impact,
(3) There was no rebound velocity observed when the model impacted
the concrete block.
(4) The maximum diametral increase measured on the model was
21 percent.
(5) The deformation 6/R was measured as 0,91 (where 6 is defined
as the diameter of the vessel before impact minus the height of the vessel
after impact and R is the vessel radius before impact).
INTRODUCTION
In all mobile nuclear reactors, fission products must be contained with
the same level of confidence as in stationary power plants. In the case of
a high speed mobile reactor, such as a nuclear airplane, impact velocities
of 800 to 1000 ft/sec can occur.
One method for containing fission products under these severe conditions
is to put the reactor in a containment vessel and design the vessel and its
contents to absorb the impact energy without rupturing the containment vessel.
The energy of impact would be absorbed by deformation of the containment
vessel and the internal components of the vessel such as the shielding and
reactor parts.
Initially, experimental deformation data was correlated by Morris on
3/4 inch to 4 inch i.d. hollow vessels (refs. 1 and 2) which had been impact
tested to 700 ft/sec as part of an isotope space program (ref. 3). His
correlation predicted that a large reactor containment vessel would deform
similar to the small vessels. The correlation, however did not consider
the effects of internal components. Tests were necessary to correlate these
effects.
Five two foot diameter mock-up models of reactor containment vessel
system were tested (refs. 4 and 5). The models weighed from 350 to 1305
pounds. The first design was simply a hollow sphere to check Morris'
correlation which relates small sphere data to larger spheres
and 2). The remaining designs represented a reactor surrounded by radia-
tion shielding and a containment vessel, both of which were designed to ab-
sorb impact energy. The tests were conducted at the Sandia Sled Track in
Albuquerque, New Mexico , They were impacted at speeds from 241 to
580 ft/sec. No leaks were detected nor cracks observed on any of the
models after impact. Also, test data from the first impact test of the 24 inch
diameter hollow vessel design verified that large vessels do deform like
small vessels as predicted by the hollow vessel correlation derived from the
3/4 inch to 4 inch o,d, vessel data. This lent credibility that the data ob-
tained on two foot model tests could be applied to the full scale reactor con-
tainment vessels which are of the order of 15 to 20 foot in diameter,
As a result of this program a new series of impact tests were planned
to determine the effect on the containment vessel and reactor core of higher
velocities, vessel welds, vessel penetrations, and type of impact surfaces.
The models are similar to those formerly tested with an emphasis on dif-
ferent shield and containment vessel materials, and core and containment
vessel designs. These models are designed and built at LeRC and tested
at the Holloman Track, Alamogordo, New Mexico by the Kirtland Air Force
Weapons Laboratory Albuquerque, New Mexico, Impact velocities in ex-
cess of 1000 ft/sec were planned. Post evaluation is conducted by both
LeRC and the Air Force,
The first test model of this series of tests was impacted at 640 ft/sec
(ref,, 6), This report describes another test conducted at 1055 ft/sec, A
description of the model, test set-up and results of the the test are presented.
The model is being measured, sectioned and analyzed in detail at the Lewis
Research Center but these results are not yet available,
DESCRIPTION OF SLED TEST
The impact test was conducted at the Holloman Track in Alamogordo,
New Mexico, This is a dual rail track extending 35, 588 feet. Only 2000 feet
of the track was used for this test. The test set-up is shown schematically
in figure 1. It consists of a pusher sled, payload sled, sled splitter and
target. A bridge frame is placed over the track for mounting some of the
cameras.
The model is placed on a "payload sled" (ref. fig. 2). It is attached
by nylon straps which provide the support during sled operation,- A "pusher
sled" containing four Genie motors for its propulsion thrust pushes the
"payload sled" down the track (ref. fig. 3). Having reached predesigned
speed the "pusher sled" is stopped by water braking and momentum ex-
change. It is reused for additional tests. The "payload sled" continues
down the track; propelled by twelve Zuni motors staged six and six .^
A "sled splitter "placed at the^end of the track (ref. .4)is designed
to, separate the impact "model'.from the "paiiyload sled.',' .This massive7 J
22,000 pound structure is weld fabricated from 3 and 6 inch armor plate.
Knives are positioned on the "sled splitter" to cut the nylon support straps
and allow the impact model to pass through. The "payload sled" is de-
stroyed with each test by the "sled splitter I1'.' Small shape charges are also
placed on the "payload sled" to initiate its destruction.
Fifty feet beyond the "sled splitter" is a concrete block (ref. fig. 5)
five foot on a side weighing approximately 18,000 pounds. The impact
model having been separated from the "payload sled" continues a free
flight impacting against the concrete block.
Three movie cameras are mounted at the impact point (ref. fig. 6,
Fx 2, 3, and 4). They operated at speeds of 4545 and 9090 frames/sec. An
additional camera was mounted on a bridge over the track looking toward
the impact area (Fx 1). This camera operated at 4545 frames/sec. Its
purpose was to record an overall view including secondary impacts. Addi-
tional movies were taken from a helicopter in real time and 250 frames/sec,
showing the entire test sequence.
5TEST MODEL
A.drawing of the model tested is presented in figure 7, A photograph
of it prior to impact is- presented in figure 8, It consists of a reactor core
mock-up surrounded by shielding and a two foot diameter spherical stainless
steel containment vessel. The shielding consists of metal saddles (fig, 9)
and rock salt. The metal saddles simulate an energy absorbing gamma
shield. Rock salt simulating a LiH neutron shield material is poured into
the 80 percent void spaces provided by the saddles.
The fabrication stages of the core and containment vessel are shown
in figures 10(a) to (c). The simulated core consists of an 8-inch diameter
by 8-inch long cylinder, 1/4 inch, thick, filled with approximately 850 -
1/4 inch tubes of 0,065 inch wall thickness (fig, 10(b)), This assembly is
capped on both ends and placed within a 12 inch diameter spherical stain-
less steel vessel 5/16 inch thick.
This assembly is then centered within a 5/8 inch thick two foot diameter
containment vessel by small rods which are tack welded to the containment
vessel and to the simulated reactor sphere (fig, 10(c)). The rods are weak
and have no effect on the results of the impact test. Saddles aacLsalt are
added, via the b> ^ ncn PiPe fitting after completion of the welding of the con-
tainment vessel.
The tubes in the model core simulate the fuel pins and flow passages of
either a fast or thermal reactor core. The 12 inch containment vessel rep-
resents a gamma shielding material.
The tfotal weight of this model was 111-9 /pounds (fig, 7). . The core in-
cluding tubes cylinder and one foot diameter sphere weighed 13&-pounds.
The saddles and salt weighed 450 and 180 pounds, respectively^ The out-
side two foot diameter by 5/8 inch nominal wall thickness vessel weighed
350 pounds.
6TEST RESULTS
The impact model was slung on the "payload sled" by nylon straps. It
was oriented such that the pipe fitting was up-range from the impact point
(fig, 2). In this position the impact did not occur on the weld, ije...-, the
weld was in a plane parallel to the face of the concrete block0 The weld,
however, was deformed due to the diametral increase of the model. This
orientation also caused the impact forces to be applied to the mocked-up
reactor core along its longitudinal axis. The direction of impact-is shown
in the drawing of the model of figure 7.
The rocket ignition point was at the 32850 foot track station. Impact of
the sled with the "sled splitter" and subsequent release of the model oc-
curred at the 34790 foot track station. The last speed recorded by the
track sensors was 1023 ft/sec. ~
Upon impact of the sled with the "sled splitter" the model separated
from the nylon sling and passed through the "sled splitter" impacting with
the concrete block 50 feet beyond,, In prior tests the concrete block was
positioned only 25 feet beyond the "sled splitter7' and the result was that
the splitter was pushed back to the concrete due to the impact forces of the
sled. The extra 25 feet, plus a trench half way between, prevented the sled
from interfering with the impact sequence of the sphere and the concrete
block.
Figure 5 shows the "sled splitter" and concrete block prior to impact.
Shape charges on the "payload sled" intitiated destruction of the sled with
the "sled splitter" prior to impact. The position of the splitter after the
test is shown in figure 11. Little damage resulted to the splitter and it can
be used for additional tests.
Impact velocity of the model with the concrete block, as measured by
the high speed film was 1055 ft/sec. This is an increase in velocity of
32. ft/sec over that recorded just prior to impact of the sled with the "sled
splitter. " This increase velocity is due to the "sling shot" effect of the
nylon strapping. The model is retained in the sled by two sets of straps.
Just prior to impact of the "sled splitter" with the "payload sled, " the
cutter on the splitter severs the first set of straps leaving the model mo-
mentarily suspended in the sled by the second set of straps which are still
under tension. The model then is accelerated in the direction of motion by
about 32 ft/sec. When the "payload sled" impacts the splitter the momentum
of the model tears loose the second set of straps.
Figure 12 (a) to(h) shows a consecutive sequence of photographs of the
model at impact with the concrete block. These pictures were taken with
camera Fx 3 (9090 frames/sec) in figure 6. During the impact4iie model
disappears in a cloud of dust indicating that the concrete block is being
pulverized during the impact.
After impact the model was found laying some distance away (about
50 ft) from the impacted concrete (see fig. 13). It had been deflected by
the concrete and came to rest in the position shown. The concrete block
suffered total destruction.
Ehotographs of the impacted model are shown in figures 14(a) to (c).
Deformation occurred in both, the impacted hemisphere and the hemisphere
opposite from the direction of impact. The hemispherical weld was not
oriented perfectly in a plane parallel to the face of the concrete target. Con-
sequently, the weld is closer in some areas to the deformation radius of the
impacted face than the others. This results in a concave impacted face in
the area where the weld is the closest. The reason for this is that the weld
region is the thickest and therefore stronger than the adjacent material thus
forcing the adjacent material to greater strains.
A,leak test was performed on the model. This test consists of pres-
surizing the containment vessel to 50 psig with helium gas. The entire as-
sembly is then encapsulated in a plastic bag; the interior of the bag is
probed for leaks using a mass spectrometer type leak detector. No leaks
were detected.
Measurements were taken of the sphere. These measurements indicate
how much strain occurred. The maximum"dTa"meteF occurfed'laf the impacted
face. It was measured as 29 inches compared to 24 inches prior to impact.
8This is a diametral strain of 21 percent. It is of the same magnitude as
similar impacted models (refs. 4 to 6) . . The amount of deformation 6/R
was measured as 0.91 (where 6 is defined as the diameter of the vessel
before impact minus the height of the vessel after impact and R is the .
vessel radius before impact). The 0.91 value for 6/R is larger than those
impacted models measured before. At higher impact velocities the di-
ametral deformation also increased. The diametral deformation, however,
did not show an increase comparable to the deformation 6/R. This probr
ably was partly; due to the^weld restraining the diameter from growth. Dis-
tortion of the containment vesseliin the noriimpacted hemisphere was trans;^
f erred to the upper regions around the filler plug as shown in figure 10.
Further measurements will be taken to more accurately evaluate the
deformation and strain that occurred on the unit. The model will be sec-
tioned to evaluate the distortion that occurred on the core. Test specimens
will be machined and tensile tests made.
CONCLUSIONS
This report presents data of an impact test against a reinforced con-
crete block of a 2-foot diameter mock-up model of a reactor containment
vessel system. The test was conducted at the Hollo man Test Track in
Alamogordo, New Mexico. The model weighed 1119 pounds. It was im-
pacted against an 18,000 pound concrete block at 1055 ft/sec. The following
observations were made from the results of this test:
1. No leaks were detected nor cracks observed on the model.
2. The concrete block was totally destroyed at impact.
3. There was no rebound velocity observed when the model impacted
the concrete block.
4. The maximum diametral increase measured on the model was
21 percent.
5, The deformation 6/R was measured as 0.91 (where 8 is defined
as the diameter of the vessel before impact minus the height of the vessel
after impact and R is the vessel radius before impact).
6, The velocity of 1055 ft/sec for this test was the highest impact ve-
locity that has been run to-date,
REFERENCES
1. Morris, Richard E.: Permanent Impact Deformation of Spherical
Shells, NASA TMX-2067, 1970,
2. Morris, Richard E.: Empirical Correlation of Small Hollow Sphere
Impact Failure Data Using Dimensional Analysis, NASA TM X-52874,
1970.
&, Simonis, John C,; and Stoneking, Charles E,: A Study of Impact Effects
of Spherical Shells, Part II: A Theoretical and Experimental Study of
the Response of Spherical Shells to Impact Loads. Georgia Inst, Tech.
(AEC Rep, SC-CR-67-2540), Dec, 1966.
4, Puthoff, R, L.; and Dallas, T,: Preliminary Results on 400 fps Impact
Tests of Two 2-ft Diameter Containment Models for Mobile Nuclear
Reactors. NASA TM X- 52915, 1970,
5, Puthoff, R, L.: High Speed Impact Tests of a Model Nuclear Reactor
Containment System, Presented at the American Nuclear Society
Annual Meeting, Boston, Mass,, June 13-17, 1971,
6, Puthoff, Richard L,: A 640 Foot per Second Impact Test of a Two-Foot
Diameter Model Nuclear Reactor Containment System Without Fracture,
NASA TMX-67997, 1971.
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Figure 13. - Concrete target and model after impact.
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Figure 14. - Model - post impact.
NASA-Lewi.-Com'l


A 1055 ft/sec impact test of a two foot diameter model nuclear reactor containment system without fracture

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