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LEGAL NOTICE –
APR 27 86
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The report we prepared an account of Government O rd work. Watcher the United
data, por the Courtoa, nor w pur og sett og blod Comindoni
A. Maka may marteaty or reprezestadon, aprend w lap., Moroct to die noco-
racy. capith, or totalment at the talordito contatud b to report, or out the w
ol ay tuloration, apparte, wethod, or procu declared in the report any not to be
printaly owned rtcu; of
B. Awer my abilities with respect to the wwe of, for den su rezulthy fross the
in day taformation, appuntua, bet ud, or procu daclound in this report
As and b e bore, "persoa actag on all of the Cocaminator" tuctura ay na-
ploys or contractor of the Commission, or employee of such sootractor, to the most chat
much mployee or contructor of de Constanta, or employee of mucha contractor sopar,
1 dins butus, or provides noceo to, nay tafordato para DI M. employment of contract
wobe De Coagularla, or his employment wild anica contractor,
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312
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contract with the Union Carbide Corporation.
*Research sponsored in part by the U. S. Atomic Energy Commission under
(Sponsored by the European Nuclear Energy Agency of the 0.E.C.D.).
Research Center of Grenoble, Grenoble, France, 15th - 18th June 1965
Symposium on Working Methods In High Activity Hot Laboratories, Nuclear
To be presented (17 June 1965, 16:05-16:20 hr) at the International
Vallecitos Atomic Labora
Robert F. Stearns
U.S. Naval Radiological Defense Laboratory
Ross K. Fuller
Los Alamos Scientific Laboratory
Jerome E. Dummer
Vallec Robe Acond St Laboratory IP
(Formerly Hanford Laboratories)
Pacific Northwest Laboratory
Ernest A. Berreth
Oak Ridge National Laboratory
Clyde D. Watson
RU
ARE ON FILE IN THE RECEIVING SCHON
THE PUBLIC IS APPROVED, PROCEDURES
PATENT CLEARANCE OBTAINED. RELEASE TO
ASI-AYNUO
DECONTAMINATING 10T CELLS*
POLICY AND PROCEDURES USED IN THE UNITED STATES PORTAL
1
Paper
Communication
No. 40
.3.6138
CONF-650604-3
"
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ORML - AEC - OFFICIAL .,


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ORNI - AI- OFFICIAL
POLICY AND PROCEDURES USED IN THE UNITED STATES FOR
DECONTAMINATING HOT CELLS
Clyde D. Watson, Ernest A. Berreth, Jerome E. Dummer,
Ross K. Fuller, and Robert F. Stearns
Abstract
In the United States, hot cells and equipment for handling radio-
active solids or liquids are successfully decontaminated as required.
The frequency varies from about three times a year to only once in
three years for the larger pilot plant units. The normal time required
to decontaminate a facility is about two to six weeks. Decontamination
is usually done remotely, through appropriate design, precontamination
application of protective coatings, expendable equipment, the proper
choice of cleaning reagents (detergents, organic solvents, acids,
alkalies, chelating agents and physical methods (grinding, ultrasonic
cleaning, blasting, and abrading).
Methods have been developed and are presented in this paper for
decontaminating hot-ce118 and adjacent areas subjected to the uncon-
trolled release of radioactivity.
RÉGLEMENTS ET MÉTHODES EMPLOYÉCS AUX ÉTATS UNIS POUR
LA DÉCONTAMINATION DE CELLULES CHAUDES
Clyde D. Watson, Ernest A. Berreth, Jerome E. Dummer,
Ross K. Fuller, and Robert F. Stearns.
Résumé
Aux Etats Unis les cellules chaudes à activité élevée et l'équipe-
ment utilisé pour manipuler les éléments radioactifs sont décontaminées
à la demande avec grand succes. La fréquence de décontamination varie
de 3 fois par an à une fois seulement en 3 ans pour les grandes unités
pilotes. Le temps normalement requis pour décontaminer une installation
est de l'ordre de deux à six semaines. La décontamination est ordinaire.
ment faite a distance grâce à une disposition appropriée de l'équipment,
à l'emploi de recouvrements protecteurs avant contamination, et de
pièces non réutilisables et grâce au choix de produits de nettoyage
(détergents, solvants organiques, acides, bases et agents de chelation)
et de méthodes physiques (broyage, ultrasons, nettoyage par jets et
polissage). .
:
La présentation décrit des méthodes utilisées pour' décontaminer
les cellules chaudes et les zones adjacentes ou la radioactivité peut
involontairement s'étendre.
mera ORNE
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-2.
INTRODUCTION
0111-ABC - OFFICIAL
Research and development investigators using radioactive nuclides
are confronted ultimately with the problem of removing and disposing of
them. Decontamination is the practice or art of removing radioactive
materials in the form of soils, chemical compounds and solutions,
The tal fines, reaction products, etc., from valuable surfaces in order
to:
. 1. render such surfaces (hot cells, buildings, areas) harmless
or safe to unprotected operators and the surrounding bic!og-
ical environment;
restore valuable production, research, development facilities,
and equipnent to a condition suitable for reuse; or to
3. aid in safely removing unwanted radioactivity, contaminated
materials, and equipment from an undesirable location to a
more desirable one.
Decontamination became a serious topic of interest soon after the
Enrico Fermi Pile began operating, in December 1942. Early in 1943
at Oak Ridge National Laboratory, then Clinton Laboratories, the
literature reports an investigation (1,2,3) of reagents for removing
fission products from work areas and equipment used in processing
plutonium. As the nuclear industry grew, each laboratory or site
developed favorite methods, but no "universal" methods or "magic"
solutions emerged. Consequently, decontamination as practiced in the
United States varies from one site to another, depending on the nature
of the work, age (design) of facilities, and convenience of waste
disposal.
Since 1943, the field has been extensively investigated and the
results presented in numerous reports. Much of the information is
contained in recent books (4,5,6,7). Commercial interest has grown
sufficiently that several companies have entered the field in the past
10 to 15 years (8,9, 10, 11, 12, 13). Nuclear sites now depend more and
more on commercial sources for chemical and physical methods.
Generally, decontamination is considered to be a highly effective
cleaning process (14, 15). In addition, the processes carry with them
the associated problems of controlling the exposure of workers to
ionizing radiation; preventing the contamination of workers and
recontamination of areas; criticality considerations; the generation,
10
QINI-AEC - OFFICIAL
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treatment, and disposal of various types of radioactive wastes; and
the loss of use of work areas and equipment for extended times.
This paper is a survey of current decontamination policy and basic
procedures practiced throughout the United States for removing radio-
active contaminants. The procedures reported here are specific for
hot-laboratory operations, especially hot cells handling solids and, or,
11quido, and for supporting enclosures and other barriers used in
conjunction with the cells. The practices range from spraying and
mopping of solutions designed to decontaminate metals while only
slightly affecting the inetals, themselves, to gross surface removal
by grinding or blasting. In addition, some procedures are presented
which were found effective in the decontamination of the structural
and biological environmer. contaminated as the result of the uncontrolled
release of radionuclides from hot-cell operations.
GENERAL POLICY
Decontamination work has undergone significant evolutionary changes . .
during the past 20 years both in general policy and in procedures.
When first tried, the nearly complete removal of radioactivity was
attempted. However, it was soon realized that complete decontamination
was not only costly and impractical but that the object or surface
treated was either damaged or ruined. Most important, thorough decon-
tamination cailed for close contact, a threat to the health of the
worker. Thus, it became much more economical and safer to clean the
inside of a hot cell remotely, even if fairly expensive equipment was
required, than to use the "ce11-entry" or direct-worker method in high
radiation fields.
The present attitude may be summed up as, "Radioactive contamina-
tion is a necessary evil best managed by avoiding it or by working
around it." This is done by designing cells and equipment to minimize
the need for decontamination. In addition, equipment is arranged so
that it can be remotely maintained by replacement of parts of subassem-
blies with manipulators. For example, equipment, tools, etc., where
practicable, is inexpensive and commercially available. They are
usually modified to make remote installation, operation, maintenance, .
and removal easier. If worn out or if remote maintenance proves
unsatisfactory, such equipment can be discarded. It is also advan-
tageous to localize or limi'e the spread of contamination by placing
ORNL - AEC - OFFICIAL
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ORN - AEC - OFFICIAL
shielding around the hottest sources, conducting the experiment in a
box placed in the cell and by using other barriers, and trays (see
Paper 52 of this Symposium, "u.s. Practices In The Control and Contain-
ment of Radioactive Contamination," K. R. Ferguson).
In addition to being protected by containment barriers, the cell
walls and floors, equipment surfaces, and tools are further protected
by surface treatments before contamination occurs. Radiation-resistant
organic protective coatings, marking inks, water soluble paints, plas-
tic sheeting, and tapes are commonly used.
The u.s. policy is reflected in the Transur anium Processing Plant
at ORNL, now being built, which is designed for completely remote
maintenance and decontamination (16). All equipment, including the
piping system, may be disconnected and replaced by in-cell manipulators.'
Normally, complete decontamination of a cell for entry by workers should
never be required here. The cell bank is designed so that all opera-
tions can be isolated and so that transfers between the nine cells can
be made in a sealed conveyor. This helps ensure that even a serious
spill in one ce11 will have little effect on adjacent ones.
Summarizing, in the U.S.A. today, we design hot cells to reduce
the need for cleanup, and, when we do decontaminate them, it is done
by remote manipulation and only to the extent required. Total decon-
tamination is rarely required or accomplished. Insofar as possible,
a similar policy is pursued in the older hot cells and large-scale
engineering facilities, some of which ar: not equipped with mechanical
ustnipulators.
CONTAMINATION AND DECONTAMINATION MECHANI SMS
com.
It is generally accepted that contamination of a surface by
radionuclides occurs through chemisorption, by ion exchange with free
surface ions, and by physisorption or physical adhesion. A11 this is
accompanied by migration of the nuclides into cracks and crevices.
Only a few minutes is required for radioactive ions to become attached
to the surfaces of metals and other structural materials (17). Experi-
ence has shown that radioactive ions are fixed by the visible and
invisible oxide films on metals; after extended contact times (months ),
the contaminants diffuse into the parent metal and interact beneath
ORNL - AEC - OFFICIAL
the oxide films.
-5-
Decontamination (15) also includes chemical and physical mecha-
nisms. The radioactive atoms which have combined with nonradioactive
ones are dissolved by contacting them with a strong solvent while
simultaneously preventing their redeposition. This 18 usually done
with solutions of strong acids or alkalies which also contain com-
plexing and chelating agents.
The physical methods include the removal of loosely adhering
surface scales, soils, salts, and particulate matter, and the abrading
away of oxides and a surface layer of the material itself. Examples
of the methods are: vacuum cleaning, swabbing, brushing, high-impact
jet cleaning (with steam or water), sandblasting, and grinding. An
ideal method would be one that leaves a surface in its original condi-
tion of smoothness and utility, but this is rarely achieved.
PROCEDURES
To simplify the presentation of typical procedures, either chemi-
cal or physical, two general types of hot-ce11 facilities are considered.
Hot Cells in Which Solids are Handled
Hot cells in which solids are handled are used primarily for
conducting experiments that include mechanical processing or dis-
mantling, and metallurgical operations, all of which generate partic-
ulate matter (principally grindings, sawings, turnings, oxides, etc.).
Although the cleaning sequence may vary from site to site, it is
usually done in three phases.
Phase I includes the general cell cleanup, in which loose,
transferable or smearable activity is removed by remotely controlled.
operations. Debris generated by the operation, itself, 18 collected .
by sweeping or vacuum cleaning. Then it is removed from the cell
(see Paper 30 of this Sympos lum, "Methods used in the U.S.A. for
Transferring Materials Through Radiation Barriers," J. W. Schulte).
Sticky tapes, treated paper, dusting cloths, damp sponges, or absorbent
rags are used when vacuum cleaning fails.
In the second part of phase I, visible deposits of more tightly
held soil, rust, dried salts, and thin films of grease, and oil, etc.
are removed from equipment, cell walls and floors. This is done with
brushes, absorbent pads, sponges, and rags moistened in aqueous
solutions of detergents and, or, complexing agents. Wet vacuum-
ORNL - AEC - OFFICIAL -----
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cleaning devices like the "slurpper" (18, 19) are also useful.
Manipulator-operated household floor polishers, fitted with a líquid
supply line and coarse brushes or steel wool, are used for scrubbing
floors, walls, and other flat working surfaces. Grease and oil are
removed easiest with an organic solvent such as trichloroethylene (20).
Some degreasers are obtainable in aerosol cans. Some sites remove
loosely held radioactive matter with steam and water jets. Here,
proper cell design and large disposal facilities for these liquid
wastes are necessary. Other sites do both: Swab and clean with steam
jets. Contamination that is smearable or that can easily be resuspended
in air to form aerosols is sometimes fixed to the surface of equipment
with glycerin or acrylic and vinyl lacquer (21). The fixing of radio-
activity, along with other normal packaging precautions used in
transferring equipment into temporary storage or to a nearby decon-
tamination facility, prevents the spread of radioactivity and the
recontamination of areas.
The overall cleaning operation is best done by beginning high in.
the cell, taking care not to flood electrical equipment and in-cell
filters (some items can be covered with protective polyethylene mem-
brane taped in place). Then one works downward to the floor. Clean-
ing only a portion of a cell at a time is essential to prevent fogging
the viewing windows. Rubber squeegees placed in the cell before jet
cleaning are helpful for removing moisture from the windows.
In phase II, the radioactivity level of the cell and equipment
is measured and graphically charted, followed by more drastic measures
for tenaciously held activity. A record is essential in following
amer met
the degree of decontamination and in determining which equipment can
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be removed by remote manipulation to make access to the remaining
equipment easier. In addition, it is necessary to determine when
radiation levels in the cell are sufficiently low to permit entry by
the operators. The hot spots in the cell are selectively attacked,
beginning with the most contaminated areas; chemical and physical
methods are used, according to the materials involved. Effective
chemical decontaminants for various sur faces are listed in Table 1.
More information can be found in a review of commercial procedures
for cleaning metals. A recent book by Spring (22) 18 an excellent
reference.
-ORNL - AEC - OFFICIAL
x LLERLE.L1.MA.
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Table 1. Chemical Decontaminants for Removing Mixed Fission
Products From Various Types of Surfaces
02115 ~ AEC - OFFICIAL
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1. Stainless Steel
3. Aluminum
a. Oxalic acid, 0.5 M (33);
a. Use solution 2a.
hydrogen peroxide, 0.3 M;
sodium or ammonium fluoride,
| b. Turco (8) and others as in lc.
0.1 M;
Temp., 85-95°C
4. Lead
Contact time, about 1 hr
a. Dilute nitric acid chosen for
Can be destroyed by adding
desired degree of attack
H2O2 and heating
• Concentrated hydrochloric
Oxalic acid, 0.4 M (23);
acid
hydrogen peroxide, 0.5 M;
c. Turco (8) and others as in lc.
ammonium citrate, 0.
sodium or ammonium fluoride,
0.05 M;
5. Copper, Brass
Raise to pH 4 with NH OH;
a. Dilute nitric acid
Temp., 85-95°C
b. Turco (8) and others as in lc.
Contact time, about 1 hr
This version less corrosive
Household and industrial
to nearby carbon steel;
cleaners for brass, copper
Can be destroyed as in la.
(25)
Turco Products (8):
4306-B, 4306-C
6. Glassware
Consult Turco and others a. Ultrasonic cleaning using
(9, 10, 11, 12, 13)
Turco 4234
d. Nitric acid, 1.5 M (24);
b. Automatic household dish-
sodium fluoride, 0.02 M
washers and their cleaning
e. Sulfuric acid, 1.5 M (23);
agents
hydrogen peroxide, 0.1 M;
7. Painted Surfaces
Temp., 85-95°C
Contact time, about 1 hr
a. Commercial paint cleaners
such as Oakite (26) and
2. Carbon Steel
others
a. Oxalic acid, 0.4 M (33);
b. Steam-water and detergent
hydrogen peroxide, 0.34 M;
I c. Solvents and paint strippers
citric acid, 0.16 M
Ad just to pH 4 with NH4OH or
8. A11 Surfaces
suitable mixture of salts
Temp., 85-95°C
a. Steam-water and detergent
Contact time, about 1 hr
b. Turco (8) and others as in lc.
Can be destroyed as in la.
Removes rust and inhibits
future rusting
9. Special Equipment
b. Turco Products (8):
See (8, 9, 10, 11, 12, 13) and
4518, 4512, 4324
(27 28)
Consult Turco and others, as
in lc.
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C. Commercial rust removers
02:11 HIC - OFFICIAL
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Physical methods for cleaning hot spots include ultrasonic clean-
ing (for tools, etc.), chipping, scraping, grinding with an abrasive
disc mounted on a flexible shaft, filing, scouring with coarse
stainless-steel wool, with wet pumice, or with wet-dry emery cloth
and toothbrush-size brushes fitted with stainless-steel bristles.
The surfaces on the coll and equipment are repeatedly subjected
to chemical and physical treatments until they are no longer effective
or until tolerable levels of radioactivity are reached. Equipment
that can be removed by remote handling is selectively taken out of
the cell as decontamination progresses.
In phase III, operators enter the cell to (a) assist in removing
the remaining equipment, (b) continue the decontamination of remain-
ing hot spots, and (c) install new equipment for future work. All
this may be done by the cell operators or by an independent group
specializing in this kind of work.
As equipment is removed from the cell, workers are usually
required to cut lines not easily cut by manipulators remotely. They
often use power tools or hydraulic shears. Initial encry is made
by workers wearing two suits of coveralls sealed with masking tape,
shoes or boots covered with two pairs of shoe covers, two pairs of
rubber gloves, an assault mask and hood, or a plastic air suit. After
smears are taken and the extent and type of contamination has been
established, later entries may be made by workers wearing plastic
rain gear over the coveralls. In addition, an assault mask or plastic
air mask is worn. After all equipment has been removed, the remaining
hot spots are cleaned remotely or directly by in-cell workers as re-
quired. The radioactivity levels should now be no higher than 10 to
100 mc/hr. Generally, as new equipment is installed, all cell entries
can be made by workers clad in a single suit of clothing and wearing
the assault mask. A full-vision plastic face mask supplied with fresh
air by a hose has replaced the assault mask at some sites.
IČ usually takes two to six weeks to drcontaminate typical facil. .
ities, from the smallest to the largest. An exception is found in
specialized box-in-cell facilities, which may require only one to
three days.
There is no apparent practical limit to the number of times a
hot cell can be cleaned if it is suitably protected or lined with
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stainless steel. Decontamination, however, may become more difficult
each successive time because of the surface defects produced by
previous efforts.
Hot Cells in Which Solutions are Handled
The primary source of contamination in cells in which radioactive
solutions are used arises from spills and dried salts. Typical opera-
tions include the isolation and purification of radioisotopes, the
deve lopment of chemical processing methods for recovering spent nuclear
fuels, and radiation chemistry in general. The cell equipment is
usually not purely mechanical, consisting principally of tanks, piping,
pumps, valves, glassware, and instrument lines. Yet, decontamination
is similar in many respects to that for cells in which solids are
handled. The principal difference is that the interiors of tanks,
vessels, piping, pumps, instrument lines, etc., must be cleaned.
Therefore, much larger volumes of decontaminating solutions are
required. The procedure used in a typical cell consists of six steps,
the first two of which are:
1. The interior of the cell is surveyed with remotely operated
radiation-detection instruments, and a graphic chart of the radiation
levels associated with equipment, walls, floors, etc., is prepared.
2. Sequential flushing of piping, tanks, and external surfaces
are repeated until there is little or no change in radiation levels.
The cleaning solutions used are varied, but the usual approach includes
a general spray of jet washdown with water and detergent. This is
followed by an oxidation-reduction treatment with appropriate reagents.
Three examples of step 2 follow:
A. At the ORNL Fission Product Development Laboratory (29),
the normal sequence of solutions steam-jetted or pumped through the
vessels and lines is: water plus detergent; 5% HNO3; water; 5% NaOH;
water; 0.1 M Versene;* water; 5% NaOH; water. The sequence is repeated
until radioactivity measurements on the washings show no further decline.
After decontamination of vessels and piping, the cells are opened, and .
the exterior surfaces are spray-washed to remove soluble matter. The
normal sequence here is: water; Turco 4502 (8); 5% oxalic acid; water;
and sometimes, 5% NaOH washes. However, in FPDL cells contaminated
ORNI-MEC - OFFICIAL".
*Ethylenediamine tetraacetic acid
-10-
by insoluble fission product compounds (e.8., strontium-90 titanate,
cerium-144 oxide, cesium-137 glass), a different approach is used.
Here, most of the decontamination calls for the use of detergents,
water, and mechanical removal of insoluble particles. Acids and
alkalies are ineffective. Surfaces are cleaned by pressure spraying
with water, steam, and detergents. Manipulator held fiber brushes,
adhesive strips, sponges, polishing wheels with cloth or fiber pads,
and cellulose wipes are also used. Highly contaminated spots may be
cleaned with household abrasives.
B. The High Level Radiochemistry Facility at Hanford uses
a sequence of alkaline permanganate and oxalic acid or ammonium citrate
solutions containing inhibitors, and wetting agents. Turco solutions
of similar composition are also used. Solutions are not recirculated.
About two to three gallons of solution for each cubic foot of cell.
volume is used for each decontamination.
C. The Radiochemical Processing Pilot Plant at Oak Ridge (30)
used a sequence of solutions presented in Table 2 for cleaning equip-
ment contacted by mixed fission products and plutonium during processing
of spent nuclear fuels. About 5.25 gallons oë total liquid was used
per cubic foot of cell space.
After the level of radiation in a cell has been reduced to
reasonable levels (see steps 1 and 2 and examples A, B, and C above)
the following is done:
3. Equipment is dismantled remotely, encased and removed, if
necessary in shielded casks, for burial. A11 equipment is discarded,
with but few exceptions.
4. After preparation for cell entry by high-pressure steam
cleaning at the point of entry, the cell is entered, and equipment
dismantling is continued. Dismantling is done with long-handled bolt
cutters for cutting connections to stainless-steel tubing, piping,
etc. Sabre saws or abrasive cutoff wheels are used on angle iron
frames and piping.
5. Local decontamination, dismantling, and discarding, in that
order, are continued until all equipment is removed.
6. Local hot spots are then decontaminated, and the cell is
ready for installation of equipment.
Some typical radiation levels encountered during a decontamina-
tion cycle for mixed fission products are:
-11-
Table 2. Sequence of Decontamination Solutions Used to Remove
Plutonium and Mixed Fission Products and Plutonium
Solution
Conc.
(8/liter)
1.5
Commercial detergent: Fab, Tide, etc.
Laundry detergent: Turco 4324
Degreasing solution:
NaOH
Trisodium phosphate
Sodium carbonate
2.2
4.5
6.49
Detergent
Oxalic acid
1.0
2.2
9.7
1.5 M
0.02 M
Undiluted
360
27
100
Nitric acid
Sodium fluoride
Turco 4501 (8)
Tucco 4502
Turco 4306-B
Turco 4518
Sodium hydroxide
Sodium hydroxide
Oxalate-peroxide solution:
Sodium oxalate, 4%
Hydrogen peroxide, 3%
Oxalic acid, 0.7%
Water
.
.
:
-12-
General Level Local Level
Before contamination begins
400 rads/hr 3500 rads/hr
After flushing, washdown, chemi-
cal and physical treatment
1 rad/hr 100 rads/hr
During contact removal of equip-
ment, continued physical and
chemical attack
<1 rad/hr 50 rads/hr
After equipment removal
<25 millirads/hr (25 millirads/hr
Final (after removal of hot spots). <10 millirads/hr <10 millirads/hr
At the Savannah River Operations site, extremely-high-pressure jets
(31) are successfully used to decontaminate the exteriors of large ves-
sels and other equipment. Impact is so great that insulation and paint.
are removed, but the tightly held metal oxides are not.
Protective Surfaces
Experience has shown that the decontamination of hot cells can be
accomplished much easier if all surfaces are protected with a barrier
film or protective coating before contact with radioactive materials.
Parrott (30) concluded that decontamination of the ORNL Processing
Pilot Plant was made much more difficult in areas where there were no
protective surfaces. In general, all sites use anticontamination
barriers. These consist of plastic membranes and tapes such as poly-
ethylene, polyvinyl chloride, Saran, and protective coatings on walls
and other working surfaces. Tools and small pieces of equipment are
commonly coated with grease or oil, marking ink (32), plastic tape,
or corrosion resistant protective coatings. Strippable plastic coat-
ings also protect well but almost all sites report that they too are
difficult to maintain and to remove. Waler-soluble paints such as
billboard paint, polyvinyl acetate, etc., are worthwhile and effective
but deteriorate if the humidity is high.
In general, the more costly protective coatings, such as the
vinyls and epoxies, offer the most protection and are easiest to clean.
They are radiation resistant and can tolerate 5.0 x 109 r to 1010 r.
(33,34) yet are much easier to decontaminate by washing than stainless
steel, concrete, etc. However, in contact with volatile radioactive
elements, the vinyls fix more iodine than the epoxies and retallic
surfaces (35).
-13-
Nuclides
The uncontrolled release of radioactive materials from normal
confines is an uncommon event. Nevertheless, a few such instances
have occurred, resulting in very costly cleanups. For this reason, it
was felt proper to include a section dealing with this subject. When
up-to-curie amounts of radionuclides escape from hot cells (or reactors
or shipping cantainers) in uncontrolled and unexpected ways, the
interiors and exteriors of the supporting facilities (shops, offices,
etc.), surrounding grounds, and adjacent buildings are all likely to
become contaminated.' Such a release may contaminate an unprotected
area as large as several hundred to several thousand square meters.
Here, decontamination cannot be done by remote manipulation or accord-
ing to a standard procedure, as for hot cells. Some experience, however,
indicates a general plan, which consists of an emergency phase, ar.
operational recovery phase, and a final phase. The emergency phase
is the perico immediately following the uncontrolled release. During
this time, work areas are vacated. Then, the extent of the contaminated
area is measured, and the intensity and toxicity of the nuclides are
determined or estimated. An exclusion area is marked off, usually
as an area larger than the contaminated one because a buffer zone is
needed to prevent the transfer or migration of radioactivity outside
of the contaminated area. The outer perimeter of the buffer zone is
secured, and uncontrolled entrance is prevented by temporary fences
and by plant guards. The effort during the operational recovery phase
is directed toward the decontamination of the area to a point where
rea
recovery phase may extend over a period of months. During this period,
crews restore the area so normal safety precautions and control can
prevail.
After an uncontrolled release of plutonium (30,36), it was first
fixed to the roadways, paved areas, roofing, etc., with asphalt.
Also, structures, vehicles, and some lawn areas were spray painted.
The pavement and grounds were then excavated to a depth of about 3
inches, and the top soil was hauled away and buried. Decontamination
then proceeded (Table 3) at a cost of thousands of man hours and
dollars.
-14-
Table 3. Summary of Decontamination Treatments for Various
Types of Surfaces After an Uncontrolled Release
of Mixed Fission Products and Plutonium
--. AEC - OFFICIAL
Cleanup
Rate
(ft2/
man-hr).
Character of
Contamination
Primary
Treatment
Surface
Other
Treatment
.
•
27
A11
(walls,
floor,
ceiling)
Transferrable Scrubbed or
sponged with
detergent
Dusty areas
vacuumed
. Fixed
4
Painted
metal
(walls
and
ceiling)
Paint removed with
paint remover
and scrapers;
surface scrubbed
with soap and
water
Outer layer of
paint removed
with sandpaper
Fixed
5
Concrete
(floor)
Ground with
terrazzo-floor-
grinding machine
Hot spots chipped
out, and verti-
cal surfaces
washed with
dilute hydro-
chloric acid
Fixed :
Bare metal
(stainless
steel piping
and tanks )
Rinsed with dilute
nitric acid and
scrubbed with
steel wool
Surfaces abraded
with emery
paper
Fixed
Bare metal
(other than
stainless
steel)
Abraded with emery
paper or ground
to remove pits
Fixed
Lead
shielding
Rinsed with dilute
nitric acid
Fixed
-
Oil-coated
metal
(pumps )
Washed with "Gunk",
a commercial
solvent for de-
greasing
For the more general case, where the contamination need not be
fixed, decontamination may be done faster (Table 4).
The special characteristics of each incident will determine
which sequence and combination of wet, dry, or land reclamation
OBNL - AEC - OFFICIAL
OFFICIAL
-15 -
Table 4. Methods for Decontaminating Outdoor Surfaces
Where the Radioactivity Need Not Be Fixed (27 38)
ORNI ~ hi
Rate No.
(1000 ft2 of
man-hr) Men
Effectiveness
(fraction of
radiation
remaining)
Method
Surface
Firehosing
Roof
2.8
2
40
53
3
2-3
1.
1
0.02 to 0.08(39)
0.01 to 0.04(39)
0.02(40)
0.01 to 0.10(32)
1.2
1
0.05(39)
ing
7.2
'1
0.10 to 0.30(41)
Firehosing Pavement
Motorized Pavement
flushing
Motorized Horizontal concrete
sweeping or asphalt (e.g.,
streets)
Hand sweep - Horizontal concrete
or asphalt (e.g.,
streets)
Motorized Horizontal concrete
vacuum or asphalt (e.g.,
sweeping streets)
Motor
• Unplowed soil
grading
Motor
Lawn
grading
Tractor Unp lowed soil
scraping
Tractor Plowed soil
scraping
Tractor Lawn
scraping
Hand shovel Lawn
14.40
0.01
3.34
0
0.1
1.07
0.1
3.44
0.1
1.86
0.1
0.1
0.16
0.33
Hand shovel Flower beds
0.1
metoa
*Land reclamation methods usually call for the removal of the upper
1 to 3 in. (2 to 8 cm) of the soil and its burial at an approved
site.
Note: Sandblasting is effectively used on metallic or painted
surfaces, but its use is generally avoided because of the
radioactive aerosuls it generates.
***a
*
ORNL - AEC - OFFICIAL ...............
methods will be most effective. The general sequence of decontamina-
tion methods would be: (1) sweeping of large paved areas with a
motorized street sweeper or motorized vacuum sweeper; (2) sweeping of
-16.
Oai - AEC - OFFICIAL
sidewalks and small paved areas that are inaccessible to mechanized
equipment, by hand; (3) flushing of large paved areas with a motorized
street flusher or with manually held fire hoses; (4) firehosing of
roofs and sides of buildings and structures; (5) application of land
reclamation procedures to unpaved areas; (6) hand or motorized brushing
and scrubbing on surfaces with detergents, followed by rinsing; and
(7) surface -removal techniques as required, followed by resurfacing.
This entire sequence may be changed as required; also, several opera-
tions can be conducted concurrently.
There are several excellent plans for the recovery of contaminated
areas, the most comprehensive being "Fallout and Radiological Counter-
measures" (42). "Estimating Cost and Effectiveness of Land Targets",
(43) developed in 1959, is a theoretical model for planning the recovery
of a residential target complex that has been contaminated by fallout.
The plan, however, is useful in planning the recovery of any area
(industrial or residential) contaminated by radioactive material. The
basic concepts in ref (43) were verified, and an improved pre-recovery
planning procedure was developed as reported in "Radiological Recovery
of Land Target Components - Complex I an. Complex II" (21). Further
refinement of planning factors are reported in "Radiological Recovery
of Land Target Components - Complex III"
CONCLUSIONS
Hot-cells can be decontaminated and recovered for use an unlimited
number of times. However, each succeeding cleanup may be more diffi-
cult than the preceding one if protective films are not applied.
Decontamination is now recognized as playing a vital and important
role in the continued and economic operation of costly shielded facil-
ities, and this new recognition is being reflected in the improved
design of new facilities.
New chemical solutions have been developed which are superior to
nitric acid and sodium hydroxide for decontamination work. The oxalic
acid solutions of Table 1 are notable in this respect. Solutions of
this type are not only excellent decontaminants but offer the additional
advantage of being easily destroyed to simplify waste disposal.
To obtain best results, decontamination must be directed by trained
ORAL-AEC - OFFICIAL
workers.
-17-
ORNI ~ AEC - OFFICIAL
A protective film applied prior to contamination is one of the
best aids to decontamination.
There is a breakeven point beyond which it may be less costly to
discard equipment rather than to continue decontamination.
Areas around hot cells such as buildings, offices, lawns, roadways
can be decontaminated as satisfactorily as hot-cell facilities, but a
much greater effort (manpower, money) 18 required.
REFERENCES
ܪ _
ܩܶܙܩܺ
ܨܲܪ ܦ݁ܕ݁ܺܦܶܬ݁ ܦ݁ ;
1. M. D. Peterson, Equipment Decontamination-Survey Report, Clinton
Laboratories, CN-1617 (May 1944).
M. D. Peterson, 2. J. Reber, N. R. Glarum, and D. C. Overholt,
Equipment Decontamination - Progress Report, Clinton Laboratories,
CN-1869 (August 1944).
3. N. R. Glarum, D. C. Overholt, E. J. Reber, W. H. Baldwin, and
M. D. Peterson, Equipment Decontamination - Final Report, Clinton
Laboratories, CN-2208 (January 1945).
4. A. B. Meservey, "Progress in Nuclear Energy," Chap 5, Technology,
Engineering and Safety, Series IV, Vol 4, Pergamon Press (1961).
Reactor Technology, Vol 3, p. 189-210, Pergamon Press, 1962.
A. B. Meservey, "Decontamination and Film Removal," Chap 7, J. A.
Ayres, editor, Decontamination of Nuclear Reactors and Equipment
1965-1966, OTI, USAEC, in press.
D. C. Layman, and Gunnar Thornton, Remote Handling of Mobile
Nuclear Systems, Chap 5, OTI, USAEC, 1965 (in pre88).
Turco Products, Inc., Wilmington, Dealware.
Atomic Products Corp., Long Island, New York.
Wyandotte Chemical Co., Wyandotte, Michigan.
1. Penn Salt Chemical Co., Los Angeles, California.
Gray Co., Minneapolis, Minnesota.
3. Dow Chemical Co., Midland, Michigan.
D. G. Stevensor, "Detergency in the Atomic Energy Industry," pp 140-
56 in Surface Phenomena in Chemistry and Biology, ed. J. F. Danielli
et al., Pergamon Pre88, 1958.
D. G. Stevenson, "Radiological Decontamination," Research Applied
in Industry, vol XIII, pp 383-89, Butterworths, 1960.
W. D. Burch, personal conmunication, Oak Ridge National Laboratory,
Jan. 17, 1965.
0. M. Bízzeli, P. C. Tompkins, and C. D. Watson, "Practical Aspects
of Surface Decontamination," Nucleonics, 7(2), pp 42-54, 87 (1950).
P. J. Peterson, et al., A Recirculating wet Vacuum Cleaning and
Scrubbing System for Decontamination, Proceedings of the Eleventh
Conference on Hot Laboratories and Equipment, pp 281-84, American
Nuclear Society
19. C. C. Burwe 11 et al., The Los Alamos "Wing 9" Alpha-Gamma Box
System, Proceedings of the Twelfth Conference on Remote Systems
Technolygy, pp 329-35, American Nuclear Society (1964).
D. S. Irwin, and T. C. Johnson, Comparison of Solvents For Cleaning
Metal Surfaces, RFP-469 (November 1964).
W. B. Doe, personal communication, Argonne National Laboratory,
Feb. 4, 1965.
é ; ܟܲܕ ܝܼܲ

ORNI - AEC - OFFICIAL
-18-
.ORNL-ALCOLLCML

PL
2. Samel Spring, Metal cleaning, Reinhold,
A. B. Meservey, Peroxide-Inhibited Decontamination Solution for
Carbon Steel and Other Metals in the Gas-Cooled Reactor Program:
Progress Report, November 1959-July 1962, ORNL -3308.
M. R. Bennett, Evaluation of Reagent Decontamination, ORNL-CF-
51-11-123 (November 1951).
C. D. Watson, Decontaminable Surfaces and Procedures for Hot Cells,
Proceedings of the Fifth Hot Laboratories and Equipment Conference,
ORNL-CF-57-3-159.
Oakite Products, Inc., 19 Rector St., New York, N. Y.
C. J. MacFarlane and R. J. Beal, Special Equipment for Decontamina-
tion and Control of Radiation Hazards at Chalk River, CRRIS -1071
(March 1962).
Sellers Injector Corp., 1600 Hamilton St., Philadelphia, Pa.
F. N. Case, personal communication, Isotope Division, Oak Ridge
National Laboratory, Jan. 17, 1965.
J. R. Parrott, Decontamination of Ce11s 6 and 7 Building 3019
Following Plutonium-Release Incident, ORNL-3100, pp 28, 33-39
(Aug. 25, 1961).
A. J. Hill, Jr., personal communication, Savannah River Operations,
Jan. 27, 1965 (a report is in preparation).
2. J. W. Schulte, F. J. Fitzgibbon, and D. S. Shaffer, The Use of
Solvent-Soluble Films in Decontamination, Proceedings of the
Eighth Conference on Hot Laboratories and Equipment, OTI, USAEC,
(1960).
3. G. A. West, and C. D. Watson, Gamma Radiation Damage and Decontamina-
tion Evaluation of Protective Coatings and Other Materials for Hot
Laboratory and Fuel Processing Facilities, ORNL-3589 (January 1965).
34. G. A. West, and C. D. Watson, Decontamination Testing of Highly
Contaminated Protective Coatings, ORNL-2811 April 1960).
· W. B. Parsley, personal communication, Oak Ridge National Laboratory,
Nuclear Safety Pilot Plant, February 1965.
L. J. King, and W. T. McCarley, Plutonium Release Incident of
November 20, 1959, ORNL-2989 (Feb. 1, 1961).
W. L. Owen, and J. D. Sartor, Radiological Recovery of Land Target
Components - Complex I and Complex II, USNRDL-TR-570 (1962).
W. L. Owen, and J. D. Sartor, Radiological Recovery of Land Target
Components - Complex III, USNRDL-TR-700 (Nov. 20, 1963).
L. Minvielle, and W. H. Van Horn, Recovery of Petroleum Refineries
Contaminated by Fallout, USNRDL-TR-656 (June 24, 1963).
D. E. Clark, Jr., and W. C. Cobbin, Removal Effectiveness of
Simulated Dry Fallout From Paved Areas by Motorized Street Flusher,
USNRDL-TR-797 (1965).
D. E. Clark, Jr., and W. C. Cobbin, Removal Effectiveness of
Simulated Dry Fallout From Paved Areas by Motorized and Vacuumized
Street Sweepers, USNRDL-TR-746 (Aug. 8,
C. F. Miller, Fallout and Radiological Countermeasures, Vols I and
II, Standord Research Instutute, Menlo Park, California (January 1963)
H. Lee, "Estimating Cost and Effectiveness of Decontaminating Land
Targets," Vol 1, Estimating Procedure and Computational Techniques,
USNRDL-TR-435 (June 6, 1960).


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-- ORNL - AEC - OFFICIAL ..
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DATE FILMED
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24
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A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completeness, or usefulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
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use of any information, apparatus, method, or process disclosed in this report.
As used in the above, person acting on behalf of the Commission” includes any em-
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such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
END
NE
277
IV.