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CFSTI PRICES
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1966
APR 1

MASTER
PROJECT SALT VAULT: DESIGN AND OPERATION*
F. M. Empson, R. L. Bradshaw, W. J. Boegly, Jr., W. C. McClain
F. L. Parker, and W. F. Schaffer, Jr.
Health Physics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee

LEGAL NOTICE
RELEASED FOR ANNOUNCEMENT
IN NUCLEAR SCIENCE ABSTRACTS
This report was prepared as an account of Goverament sponsored work. Nellber the United
Sules, oor the Commission, nor any person acung on behalf of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect in the accu- :
racy, completeness, or usefulness of the Ir'ormation contained in this report, or what the use
of any lnformation, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or
B. Asrumos vay liabillues with rospect to the use of, or for damages resulting from the
use of any taformation, apparatus, method, or process disclosed in this report,
As used in the abovo, "por son acttag on beball of the Commission" Includes any en-
ployee or contractor of the Commission, or employee of such contractor, to the oxtent that
such employee or contractor of the Commission, or employee of such contractor preparts,
disseminates, or provides access to, way Information pursuant to his employment or contract
with Se Commission, or bio employment with such contracior.
For publication in
Proceedings of International Symposium on the
Solidification and Long-Term Storage of
Highly Radioactive Wastes
Richland, Washington
February 14-18, 1966
*Research sponsored by the U. S. Atomic Energy Commission under contract
with the Union Carbide Corporation.
*
.
PROJECT SALT VAULT: DESIGN AND OPERATION, b
F. M. Empson, R. L. Bradshow, W. J. Boegly, Jr., W. C. McClain
F. L. Parker, and W. F. Schaffer, Jr.
.
Health Physics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee
ABSTRACT
PS
The demonstration disposal of high-level radioactive
solids, initiated in November 1965 in the Carey salt mine
at Lyons, Kansas, is known as "Project Salt Vault." The
objectives of the demonstration are: (1) confirmation of
feasibility and safety of disposal in salt mines; (2) de-
monstration of required waste-handling equipment and tech-
niques; (3) determination of the stability of salt under
the influence of heat and radiation; and (4) collection
of information on creep and plastic flow of salt, which
is needed for the design of an actual disposal facility.
Fourteen irradiated fuel assemblies from the Engineering
Test Reactor serve as a source of radiation in lieu of
actual solidified wastes. The assemblies, contained in
seven cans, ave been p.laced in an array of holes in the
floor. During the course of the 2-year test, four sets
of assemblies will be used to achieve a peak dose to the
salt of about 8 x 100 rad and the temperature of the ad-
jacent salt will be raised to 200°C with auxiliary elec-
trical heaters. A second array will be installed in less
pure salt at the end of the first 6 months, using the fuel
assemblies which are now in the main array. A third array,
con..isting only of heaters, is being operated as a control
to determine those effects due solely to heat. In addi-
tion to the radioactive and control arrays, a rib-pillar
will be heated by electrical heaters at its base to produce
additional information on salt flow characteristics at ele-
vated temperatures.
T
.
For publication in Proceedings of International Symposium on the solidifi-
cation and Long-Term Storage of Highly Radioactive Wastes, Richland, Washington,
February 14-18, 1966.
Research sponsored by U. S. Atomic Energy Commission under contract with
Union Carbide Corporation.
1
1.
INTRODUCTION
The safe disposal of radioactive wastes is of paramount long-range impor-
tance to the development of nuclear power. At present the most favored scheme
is disposal in geologic formations of high-level radioactive wastes after they
have been solidified.
The investigation of rock salt as a medium for disposal of liquid hifih-
level radioactive was'te began in 1956 following the recommendations of the Na-
tional Academy of Sciences-National Research Council Committee. In the soring
of 1962, at the request of the Division of Reactor Development and Technology,
a study was made of the feasibility of using irradiated fuel elements to simu-
late solidified high-level radioactive was te storage in salt formations. It
was concluded that it was feasible to use irradiated fuel elements to establish
the practicality of using sult formations for waste disposal before significant
quantities of solidified wastes would be produced. In addition, it was con-
cluded that for a small additional cost the scope of the demonstration could
be extended to yield additional information which would be valuable in the
design of an actual disposal facility. Project Salt Vault has included, there-
fore, the design and fabrication of prototype waste-handling equipment and is
being operated to obtain additional information on the effect of elevated tem-
peratures on the creep and plastic flow of salt.? The objectives of Project
Salt Vault are (1) confirmation of feasibility and safety of disposal of high-
level solidified radioactive was tes in sal' mines; (2) demonstration of re-
quired waste-handling equipment and techniques; (3) determination of the
stability of salt under the influence of heat and radiation; and (4) collection
of information on creep and plastic flow of salt, which is needed for the de-
sign of an actual disposal facility.
Choice of Site
Project Salt Vault is being carried out at the Lyons, Kansas, mine of The
Carey Salt Company. This mine is located in the city of Lyons, Rice County,
Kansas. The mine, which has a depth of 1020 ft at the shaft, was operated
from 1890 to 1948 and has been kept in stand-by condition since that time.
Alternate sites considered were Project Gnome in New Mexico, the Hutchin-
son, Kansas, Naval Air Station, and The Carey Salt Company's Hutchinson mine.
The Carey Salt Company ruled out the Hutchinson mine, as it is a producing
mine. The Naval Air Station would have required a complete mine development,
including the shaft and hoisting equipment. The Gnome site had the advantage
of being on government-owned land with a suitable shaft and hoisting equipment
available. However, the salt is of poor quality and not representative of for
mations likely to be considered for a permanent facility. Also, it is in a
remote location (both an advantage and a disadvantage) and conflicts with the
Plowshare program were considered possible. The Lyons mine had the advantages
of a more accessible location, and a favorable public relations background at
both the state and local levels, but the disadvantages of an inadequate hoist-
ing system and inefficient mine space.
Concept of Project Salt Vault
The basic operations of Project Salt Vault as conceived are as indicated
in Fig. 1: (1) canning the irradiated Engineering Test Reactor fuel assemblies
_
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.
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.
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Fig. 1. Basic Operations of Project Salt Vault (ORNL-DWG 63-2432).
UNCLASSIFIED
ORNL-DWG 63-2432

Headframe
Shipping Cask for the Fuel Assembly
Rail Car,
Charging
Shaft for
the Fuel
Assembly
1000

Transporter for the Fuel Assembly
INTI!
Double
Containment.
Shield
All Dimensions in Feet
Liners
Encapsulated
Fuel Assembly
:11; Idaho, (2) shipment to Lyons by truck in a shielded cask equipped with sup-
ponential cooling, (3) trano l'er of the canisters into the mine with the cask
L! Cherylni, device, (H) transfer of the canisters into the disposal holes in
the f'loor with a special shielded cask designated as a fuel assembly trans-
porter. The canning operation, the handling equipment, anå the design of the
liners are detailed in the paper by W. F. Schaffer, Jr.
.
.
21 PTT
2. DESIGN OF PROJECT SALT VAULT
I
-
?
2
Following the decision to use irradiated fuel assemblies as a radiation
source in lieu of actual solidified waste, a study was made of available fuel
elements and of fission product sources. 2 The ETR fuel assembly (aluminum
alloy) was chosen because of the short operating cycle of the reactor (which
produces sufficient assemblies to allow che rging the seven hol.es of the experi-
ment at convenient intervals), the relatively high radioactivity level when
first removed from the reactor, and the physical dimensions of the assemblies.
Power reactor fuel assemklies (stainless steel) would have been preferable
from the standpoint of allowable element temperature. However, the uncertain-
ties in availability of the power reactor assemblies at a particular time and
the length of most such assemblies determined the choice of ETR assemblies.
Isotope sources were ruled out, because they did not offer appreciable cost
advantage and had the disadvantage of a relatively narrow energy spectrum.
LA
TAL
1
.
1.
It would be expected that the logical choice of space for waste disposal
in a salt mine would be in existing mined-out areas. However, in the Lyons
mine, as in most other mines in bedded salt, the salt beneath the floor con-
tains water-bearing siale strata, which would accelerate corrosion problems
with stainless steel containers. The Lyons mine pattern, while regular in the
areas available for the experiment, does not fit any repea:Sing pattern. This
would cause difficulty in interpreting the data of the movement of the struc-
ture. Because of the high stresses already on the mine pillars, future exca-
vation could involve serious hazards, considering the instabilities already
observed in the Lyons mine. Therefore, it was decided to create a newly mined
area at the periphery of the mine, at a higher level, and of the most desirable
geometry, so as to use the relatively pure salt strata.
Figure 2 is a plan of the experimental area showing the arrays which con-
sist of seven cans, on triangular spacing, 5 ft apart. This design was chosen
so that a reasonably large mass of salt would be exposed to radiation dosages
and temperatures comparable to those anticipated in an actual disposal oper-
ation. In Project Salt Vault we are exposing a circular area about 12 to 14
ft in diameter to the desired temperature and dosage. The 5-ft-triangular
spacing is reasonable for an actual operation based on Purex wastes postulated
for the mid-1900's. Use of an additional ring of 12 cans would more than dou-
ble the area affected, but is not believed to justify the additional cost and
complexity.
For comparison with the radioactive array, a geometrically similar elec-
trical array is included to serve as a control to permit the evaluation of the
effect of heat alone and to determine if there are synergistic effects due to
radiation and heat. A third array, duplicating the main radioactive array but
located in the original mine floor, will be operated using the canisters which
were in the main radioactive array the previous 6 months.
UNCLASSIFIED
ORNL-DWG 63-974A

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EXISTING FLOOR-
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WASTE CHARGING
SHAFT FROM
SURFACE
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RAMP UP
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EXISTING MINE WORKINGS SHOWN
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FLOOR RADIOACTIVE
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Fig. 2. Layoul, of Experimental Area.
Radiation Dose to Salt
Calculated doses for canneå ETR fuel assemblies and for hypothetical
Purex calciner pots are shown in Fig. 3. The dose from hypothetical Purex
waste assumes high burnup fuel (10,000 Mwd per metric ton of 2% enriched
uranium, cr 50% burnup of the 2350) and is more radioactive than any waste
currently being produced. The calcire: cylinder would contain about 15 kg of
fission products, contrasted with the 0.12 kg in the two ETR assemblies which
have 15% burnup of 93% enriched 2350. The hypothetical Purex pot at 2 years
decay is about an order of magnitude more radioactive than the 2-year decayed
pot from the ORNL Pot Calciner Pilot Plant at Hanford is anticipated to be.
Curve B shows that beyond l ft from the can, a dose of less than 10' rad
will be accumulated by the salt. With the cans on 5-ft centers, any given
rigion is only significantly affected by the dose from one can.
Temųerature in Salt
Temperature profiles around the arrays were calculated using the thermal
properties of salt at 100°c.2 Predictions may be 10%. low in the range of 200°
and high for regions well below 100°c. Figure 4 is the vertical temperature
profile in the floor along radii between heaters in the array after 1 1/2 years.
Figure 5 shows the temperature rise after the same period in the horizontal
plane 9 ft below the floor. The average temperature 9 ft below the floor in
the array is about 150°C.
Heated Pillar
In addition to the arrays described above, the temperature beneath the
salt pillar between rooms 2 and 3 will be raised to 100°C. Temperature rise
isotherms at midpoint of the heaters, 9 ft below floor level, are shown in
Fig. 6. The heaters in this experiment are contained in steel pipe which is
in direct contact with the salt. There is no radiation involved.
The objectives of this experiment are to induce such radical salt movement
that even the roof may fail. Start-up has been deferred, awaiting establish-
ment of a technique for roof support or for protection of personnel who will
enter the area for data taking. Operation is expected to begin during the
current year.
3. MINE PREPARATION+, 5
Mine Rehabilitation.-- Figure 7 is a "before and after" picture of the
hoist house and headframe installation. The makeshift headframe was replaced
with a heavy structure having a capacity of 7 tons. The existing double drum
electric hoist, 150 horsepower, was strengthened with a support bearing between
the two drims. The electrical system was completely rep.laced, above and below
ground. Ventilation was improved by installing a 30,000-cfm fan at the shaft
head. This replaced a smaller fan installed following shutdown of the mine.
Mining. -- Approximately 2000 ft of entry or tunnel was cleared for access
to the experimental area at the periphery of the mine. Preparation of the ex-
perimental area involved the mining of approximately 19,000 tons of salt which
UNCLASSIFIED
ORNL.-DWG 63-773
A - TWO-YEAR DOSE FROM TWO ETR ASSEMBLIES , SURROUNDED BY 2 in. OF
STEEL , BURIED AT 90 DAYS AGE.
3 - SAME AS A EXCEPT CHANGEOUT OF ASSEMBLIES EACH SIX MONTHS.
C - TWO-YEAR DOSE FROM 6-in. diam BY 10-ft long ACID PUREX CALCINER POT
BURIED AT 2.3 yr.
D - ULTIMATE DOSE FROM PUREX POT,
DISTANCE FROM HOLE (cm)
.
109
1011

106
107
108
1040
SALT DOSE (rads)
Fig. 3. Dose to Salt from ETR Assemblies and Acid Purex Calciner Pots.

10
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ORNL-DWG 63-779R

UU
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SALT PILLAR
ROOM
0
ROOM
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0000
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DU
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DISTANCE FROM FLOOR LEVEL (ft)
UD
DU
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6030 20
2.5
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TEMPERATURE RISE (°C)
DU
DVD
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70
10 20 30 40 50 60
DISTANCE FROM CENTER OF ARRAY (ft)
Fig. 4.
Tenperature Rise Profiles in Vertical Plane in Array.

UNCLASSIFIFD.
ORNL-DWG 63-780R

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DISTANCE FROM CENTER OF ARRAY (ft)
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TEMPERATURE RISE (°C)
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.
1
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00
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LLLLLLLLL
20 10 0 10 20 30 40 50 60
DISTANCE FROM CENTER OF ARRAY (ft)
70
Fig. 5. Nine Feet Below Floor Level - Temperature Rise isotherms After 12,800 hr
Operation of One Array. ( 7 Cans, 1546 w/can, 100°C Thermal Properties
of Salt ).
Tu
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UNCLASSIFIED
ORNL-DWG 63-775
-

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TEMPERATURE RISE (°C)
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80
10 20 30 40 50 60 70
DISTANCE FROM LONG AXIS OF PILLAR (A-A) (ft)
Fig. 6. Nine Feet Below Floor Level; Temperature Rise Isotherms After
12, 800 hr Operation of 22 Heaters at Base of Pillar ( 1546
w/ heater ).
PHOTO 68265

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was disposed of in nearby unused areas of the mine. Figure 8 shows the ramp
from the original mine level up to the experimental area, and Fig. 9 shows the
experimental area after completion, looking south toward the control room.
20
W
.
e
Waste Charging Shaft.-- Transfer of the radioactive canister's into the
mine 18 made through a 19-in.-diam shai't adjoining the experimental area. This
shaft is cased with 20-in.-OD casing and double cased above 300 ft. Both cas-
ings are grouted in place. The waste shaft also serves as a means of emergency
exit from the mine, and a one-man escape cage has been provided.
-
-
.
Experimental Equipment.-- Installation of experimental equipment was car-
ried forward as rapidly as possible behind the mining. Holes for plastic flow
gages (2631 ft of hole and 359 measurement points) and gage installation were
complete within approximately 40 days after completion of mining. Twenty-one
array holes (16-in. and 12-in. diameters by 12 1/2 ft deep) and 141 thermocouple
holes were drilled. With completion of mining, the effort was directed to in-
stallation of liners, thermocouples, temperature recorders, power wiring, ra-
diation detection equipment, and off-gas equipment.
Preoperation Work and Equ£pment Testing. -- Reading of plastic flow gages
began immediately after installation. Data taking on some gages in the old
workings began 2 years before start-up of the demonstration. All gages in the
experimental area were read for at least 6 months before start-up.
After installation of all equipment, a check operation with a dummy can-
ister was carried out, revealing some mechanical problems. After correction
of these problems, a complete test operation was carried out with two canis-
ters, each containing 500 curies of 60co. These tests showed that the system
operated satisfactorily mechanically, but that additional shielding was needed
in one region of the shipping cask and that a more level floor was required
under the waste shaft in order to butt the top of the transporter shield more
evenly against the shaft bottom. It was also found that when the canisters
were in place in the salt floor, scatter shields were needed inside the shot
retainer tubes. With these modifications, radiation exposures were reduced
to an acceptable level during all parts of the transfer.
Instrumentation
Equipment is provided for measuring temperature, salt movement (plastic
flow), and radiation dosage. It is also planned to check for possible leak-
age of radioactive particulates or gases, moisture released from the salt
structure, and for radiolyticly produced chlorine. In addition, an alarm sys-
tem is actuated by excessive temperature on fuel elements.
Temperature.-- Approximately 600 thermocouples are installed in the ex-
perimental area. These are read on two 132-point loggers, six multipoint
recorders, or with a portable potentiometer. Thermocouples are located be-
tween plates of the fuel assemblies, on the hole liners, in the air annulus,
in the salt floor, and in the rib (wall) of the rooms.
:
.
Salt Movement. -- Movement of the salt is measured by a variety of tech-
niques, two of which are shown in Fig. 10. In addition, floor uplift is fol-
lowed by careful leveling from bench marks anchored 30 ft below the floor at
some distance away in the mine workings.
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Fig. 8. Faip to Experimental Area.

Fig. 8. Pacip to Experimental Area.
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ORNL-DWG 64-922R2

- ANCHOR

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DIAL
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REMOVABLE
READING
UNIT
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FLOOR-TO-CEILING
CONVERGENCE GAGE
INTERNAL STRAIN
GAGE
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.
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Fig. 10. Plastic Flow Gages.
..
A
.
Radiation.-- Radiation dose to the salt is measured. at regular intervals
by a combination of chemical (ferrous sulfate) and radiophotoluminescent glass
rod dosimeters. They are exposed to incident radiation from the canister and
at various distances into the salt.
.
In addition, a radiation detection system draws a continuous air stream
from inside the liner (just above the canister) through a charcoal bed and
then through a rare-gas detection chamber, in which is installed a Geiger-Muller
tube connected to an alarm-actuating count-rate meter.
Alarm System.-- Alarm signals are provided for (1) high temperature of
the fuel elements in the canister, (2) radiatior. indication by the fission
product leak detection system, (3) failure of the power circuits to the arrays,
and (4) bag of ceiling at either of two points in the experimental area.
Either high fuel element temperature or a radiation alarm will deactivate
power to the array. Thermocouple failure also activates an alarm in the mine
level control room.
Alarm signals for high fuel eleinent temperature, for high radiation levels,
and for power failure are transmitted to the hoist house at the surface, thence
to the residences of the two ORNL operators, and to the office of the Rice
County Sheriff. In this way, 24-hr surveillance of the alarm system is accom-
plished without the necessity of an operator being at the mine or at home at
all times. Contact is maintained with the sheriff's office when the operators
are away from home during off hours.
4. SAFETY ANALYSES
A comprehensive safety analysis of Project Salt Vault has been completed.
The maximum credible accident is one in which the canister and fuel assemblies
are severely damaged, resulting in the release of 1311 and noble gases. Fuel
meltdown during handling or storage is not possible unless simultaneous fail-
ures occur in the electrical control circuits and the high-temperature alarm
circuits. Atmospheric release of the activity from the maximum credible acci-
dent does not produce intolerable conditions.
5.
OPERATION
The first transfer of radioactive material into the mine occurred on No-
vember 17, 18, and 19, 1965, when seven canisters containing 14 irradiated
ETR fuel assemblies were placed in the radioactive array without incident and
with a maximum personnel exposure of 200 mr. The fuel assemblies were approxi-
mately 105 days out of the reactor and contained about 206 curies.
Operating procedures for the transfers involve a detailed check list
covering each move. A supervisor at the surface and another under ground con-
trols actual operations, with all movements co-ordinated by an over-all super-
visor whose responsibility is to see that the procedure on the check list is
followed exactly.
+:
..

In the transfers, one individual received approximately 200 mr and another
approximately 100 mr. No other personnel received significant exposures. Af-
ter placement of the canisters in the liners, there is no measurable radiation
field in the array area except directly over the liners where the levels are
generally less than 10 mr/hr and a small diameter beam may reach 40 mr/hr.
Future fuel assembly changeouts are scheduled for 6-month intervals with
the canisters in the main array being transferred to the array in the original
mine floor.
The demonstration is now operating in a routine manner.
REFERENCES
1. The Disposal of Radioactive Wastes on Land, NAS-NRC Publication 519, April
1957.
2. R. L. Bradshaw, J. J. Perona, and J. 0. Blomeke, Demonstration Disposal of
High-Level Radioactive Solids in Lyons, Kansas, Salt Mine: Background and
Preliminary Design of Experimental Aspects, USAEC Report ORNI-TM-734, Oak
Ridge National Laboratory, January 10, 1964.

3. W. J. Boegly, Jr., Safety Analysis: Project Salt Vault, in preparation
as an ORNL report.
4. W. J. Boegly, Jr., et al., Health Physics Divi
July 31, 1964, ORNI-3697, pp. 19-22.
5. W. J. Boegly, Jr., et al., Health Physics Division Annual Progress Report,
July 31, 1965, ORNL-3849, pp. 10-12.
LIST OF FIGURES
Fig. 1.
Basic Operations of Project Salt Vault (ORNL-DWG 63-2432).
Fig. 2. Layout of Experimental Area.
Fig. 3. Dose to Salt from ETR Assemblies and Acid Purex Calciner Pots.
Fig. 4. Temperature Rise Profiles in Vertical Plane in Array.
Fig. 5. Nine Feet Below Floor Level - Temperature Rise Isotherms After 12,800 hr
Operation of One Array. (7 cans, 1546 w/can, 100°C Thermal Properties
of Salt)
Fig. 6. Nine Feet Below Floor Level; Temperature Rise Isotherms. After 12,800 hr
Operation of 22 Heaters at Base of Pillar (1546 w/heater).
Fig. 7. Before and After Views of Topside Facilities.
Fig. 8. Ramp to Experimental Area.
Fig. 9. Experimental Area.
Fig. 10. Plastic Flow Gages.
.

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4 / 28 / 66
DATE FILMED
END
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