Newly Developed Gaseous Decontamination Technology
Katsuyoshi Tatenuma
President of KAKEN Inc. and Invited Prof. of Toyama University
Kaken, Inc. Mito-Institute; 1044 Hori-machi, Mito, Ibaraki 310-0903 Japan
Phone +81-29-227-4485, Fax +81-29-227-4082, e-mail: tatenuma@kakenlabo.co.jp
ABSTRACT

Decontamination and volume reduction of
the radioactive wastes generated by atomic power
plants, nuclear fuel reprocessing plants and nuclear
research institutes has proven to be extremely
difficult.
With regard to two cases of heavy metals
and hydrogen isotope (tritium), two kinds of newly
developed gas-phase decontamination technology
based on gaseous reactions are introduced. One isbased on utilizing volatile properties of carbonylcompounds and fluoric compounds of radioactive
transition elements and actinides (corrosion products:
CP, fission products: FP, trans-uranium: TRUs), andanother is based on the treatment by ozone gas todecontaminate the tritiated wastes.
If gas-phase decontamination technology
will be practicable, it will not only be convenient,but economically advantageous as well, since it iscurrently very difficult to decontaminate and treat
the large volume of nuclear wastes; especiallynon-incinerable radioactive wastes.
I. Gaseous Decontamination for radioactive heavy
metals1)
I-1. Introduction
The purpose of this study is to investigate
the feasibility of simultaneous decontamination bymeans of gaseous reactions. Many radioactive
transition elements (e.g. cobalt-60, cobalt-58,
nickel-63, manganese-54, chromium-51, etc) as
well as other neutron irradiated products and fission
products (e.g. molybdenum, technetium, ruthenium,etc.), and actinides (uranium, neptunium, plutonium,etc.) are troublesome at nuclear sites and waste
management facilities. The carbonyl and fluoric

compounds of radioactive transition elements areprobably volatile. Therefore, the objective ofgas-phase decontamination is to use CO gas forcarbonylation and fluoric gases for fluorination, inorder to convert nonvolatile radioactive transition
elements and actinides to volatile chemical species,
such that evaporation is possible. Carbonylcompounds of normal transition elements havevolatile properties. Some fluoric compounds of FP
and TRUs also have volatile properties. Because thecarbonyl and fluoric compounds have thermal
properties giving them low melting points, lowboiling points, and/or sublimation points, many ofthese compounds can become gaseous or volatile ata lower temperature, such as room temperature.
New decontamination technology introduced in thispaper is based on the utilization of these volatile
properties.
By the reaction of CO gas with transition
elements on a material's surface, carbonylcompounds are produced. When radioactive
transition elements (e.g. cobalt-60, cobalt-58,
nickel-63,
manganese-54,
chromium-51,
molybdenum-99, technetium-99, ruthenium-106,
etc.) exist on a material's surface, these radioactive
transition elements can be evaporated as gaseous
forms by converting them to their carbonylcompounds. In the case of actinides, volatile fluoric
compounds are formed by reacting them withfluoric gases (e.g. F2, HF, O2F2, ClF3, BrF5, etc.).
The related chemical reactions utilized are indicatedby Eqs. (1)-(3);(a) Carbonylation reaction;
Co,Ni,Cr,Mn,Fe,Mo,Tc,Ru,Rh + CO --->
Co2(CO)8,Ni(CO)4,Cr(CO)6,Mn2(CO)10,Fe(CO)5,Mo(CO)6,Tc2(CO)10,Ru(CO)5-6,Rh2(CO)8 [volatile]---- (1)(b) Fluorination reaction;
U,Np,Pu + F2,HF(O2F2,ClF3,KrF2) --->
UF6,NpF6,PuF6 [volatile] ---- (2)Mo,Re,Tc,W,Ru + F2,HF(O2F2,ClF3,KrF2) --->
MoF6,ReF6,TcF6,WF6,RuF5-6 [volatile] ---- (3)If both carbonylation and fluorination
reactions occur at the same time, the gaseouscodecontamination of many troublesome CP, FP,
and TRUs may be possible. The concept ofcodecontamination by using carbonylation andfluorination reactions is shown in Fig. 1.

I-2. Treatments to Generate Gaseous Compounds
Thechemical-formsofgenerally
troublesome nuclides after carbonylation andfluorination were predicted in Table-1. Radioactive
transition elements of CP and FP appear either ascarbonyl forms or fluoric forms, and actinides(TRUs) take on gaseous or volatile fluoric forms.
However, despite knowing the fundamental
chemical behaviors of elements, alkali and alkali
earth metal elements (e.g. cesium-134 and -137,
strontium-90), rare earth elements (e.g. cerium-144,
praseodymium-144, promethium-147, europium154), and two of the TRUs (americium and curium)
could neither be categorized as carbonyl compounds
nor fluoric compounds, and remain categorized as"unknown". Furthermore, it was not clear whether
or not the carbonyl or fluoric compounds for

Fig.1 Concept of gas-phase codecontamination tecnology
of corrosion and fission products and TRUs bysimultaneous carbonylation and fluorination underconditions of high temperature ,high pressure ,supercriticalfluid, chemical reactive plasma, and /or highly reactive
gases.

yttrium-90 and niobium-95, grouped with theradioactive transition elements, were transformed.
Four treatment methods to generate
gaseous metal compounds were investigated. The
characteristics, differences and assumed reactions of
the four treatment methods are described below.
1) Method-1: Carbonylation and fluorination
reactions under high pressure and hightemperature2) Method-2: Promotion of the carbonylation andfluorination reactions utilizing supercritical CO2
fluid3) Method-3: Carbonylation and fluorination
reactions utilizing chemically reactive plasma
In order to decontaminate under the mild
conditions without the hard treatment at a hightemperature and pressure, the treatment is carriedout by using plasma under the conditions of room
temperature and reduced pressure to generate theunstable and highly reactive carbonyl and fluoric
species. The concept of the chemically reactive
plasma treatment is shown in Fig. 2. It is assumed
that the chemically reactive species (radical, ion-F,CO) generated by the plasma reaction of Eq. (4)react with the target nuclides to yield the carbonyl
and fluoric compounds as shown by Eq. (5);Fig.2 Codecontamination concept of chemically reactive
plasmaF2/CF4,C2F6/CF4+O2 ---> plasma---> radical, ion-F, CO [F*, F-, F+ & CO*, CO-,CO+]---- (4)radical, ion-F, CO + Co, Ru, U(CP, FP, TRUs)metal or oxide --->
Co2(CO)8, Ru(CO)5, RuF5-6, UF6 [volatile] ---- (5)4) Method-4. Fluorination reaction utilizing highly
reactive gas without plasma treatment
Furthermore, for decontamination under the more
simple treatment conditions without using plasma,some fluoric reagents such as O2F2, ClF3, BrF5,
KrF2, etc. which naturally generate theradical-fluoric species even under the conditions ofroom temperature and reduced pressure were used.
The chemical reaction of the fluoric reagents ispredicted as follows;
ClF3, O2F2, BrF5, KrF2, etc. + U, Pu, Np, Tc, Ru,
etc. --->UF6, PuF6, NpF6, TcF6, RuF5-6, etc.
[volatile] ---- (6)Carbonyl reagents which can naturally generateradical carbonyl species at ambient temperature havenot been known.
Therefore, the carbonylation
reaction using highly reactive gas was notinvestigated in this study.

Table 1 Properties of gaseous compounds of primary troublesome nuclides of corrosion and fission products and TRUs

Fig.3 Effect of F gas pressure on the removal efficiencyof U by plasma treatment.

Fig.5 Removal efficiency of U compared with treatment
time of plasmaI-3. Gaseous Decontamination utilizing thechemically reactive plasma and the fluorination
reaction utilizing highly reactive gas
In this paper, the outline of carbonylationand fluorination reactions utilizing chemicallyreactive plasma (as Method-3), and the fluorination
reaction utilizing highly reactive gas without plasma
treatment (as Method-4) are shown.

uranium).
The results of the feasibility tests areshown in Figs. 3-5, indicating that uranium wasremoved by plasma treatment using F2 gas. The
removal efficiency of uranium was sensitive to F2pressure (Fig. 3), and also depended on the
discharged voltage (Fig. 4). The effect of thetreatment time (discharged time) was not so large
for any period exceeding 2 min. (Fig. 5). Uranium
was decontaminated with a high efficiency for ashort time, and that fluorination-utilized plasma
treatment is feasible in decontaminating TRUs andsome FPs.
Next,
using
non-toxic
gases,
codecontamination of two or more elements bysimultaneous carbonyl and fluoric reactions under
the plasma treatment was investigated. The CF4 andO2 gas mixture was used as the plasma gas-reactant.
Fig. 6 shows the result on codecontamination ofradioactive cobalt (Co-60: 12.5 kBq) and uranium(2.1 Bq). Taking note of Fig. 6, the removal
efficiency of uranium was high at 100 % with aflow rate of 50 cc/min., while that of cobalt-60 wascomparably high (about 80 %). Thus, it was
confirmed that the plasma treatment ofcarbonylation and fluorination utilizing non-toxic
gases is feasible for the simultaneous
decontamination of many nuclides (CP, FP and
TRUs). The effect of the mixed gas plasma of CF4

I-3.1 Chemically Reactive Plasma (as Method-3)
Tests were performed varying the pressureof reaction gases, treatment time, the kinds of gases,
the pretreatment conditions of mounting-sample
materials, and the type of nuclides (cobalt-60 and

Fig.4 Removal efficiency of U compared with voltage
discharged by plasma treatment.

Fig.6 Removal efficiency of 60Co and U comparedwith flow rate of plasma gas of CF4 + O2(12%)

and O2 to remove the thick uranium layer (U3O8) on
stainless steel is shown in Fig. 7, which shows
pictures before treatment and after one-time shortplasma treatment. As shown, the thick uranium
layer was removed by the treatment ofchemically-reactive plasma using the gas-mixture.
The gaseous uranium fluoride and excess unreacted
fluorine gas were completely trapped by the
Halogen-filter. It was concluded, therefore, thateven in the case of thick contamination, it ispossible to remove the contaminated surface layer.
Furthermore, plasma treatments using
other non-toxic gases such as CO2+H2, CH4+O2 andCF4 only were investigated to generate reactive
Table 2 Removal efficiency of 60Co and U by mixed-gas plasma

Fig.7 Removal of thick U layer(U3O8) by plasma of
CF4 + O2(cross sections of SUS304 surface).

carbonyl and fluoric species. Tests using cobalt-60
and uranium were conducted to examine thepretreatment effect of H2 gas for reduction thechemical forms of target nuclides, thereby reducing
the valency of the uranium. The results are shownin Table-2. Judging from the removal data of
cobalt-60 in Table-2, the plasma treatment using a
mixture of gas [containing carbon but not fluorine:e.g. CH4, CO2, etc.] and oxygen has the ability togenerate the carbonyl species. Also, only CF4 has
the ability to remove cobalt-60 by itself from theFig.8 Effect of ClF3 pressure on the removal efficiencyof U.

oxidized metal surface. As the most likely reason,cobalt-60 pretreated by oxidization might be
attacked by a radical carbon atom generated by theplasma treatment of CF4; the reaction between
radical carbon atoms and oxygen from the oxide
layer or from the cobalt compound on the pretreatedstainless steel sample. Eqs. (7)-(8) indicate thepresumptive behavior. The effects of the H2
pretreatment, on the other hand, was not as obvious.
CF4 ---> plasma ---> radical, ion-C [C*, C-, C+]--- (7)
radical, ion-C [C*, C-, C+] + Co
(Fe,Cr,Ni)-oxide --->Co-metal + radical-CO --->
Co2(CO)8 [volatile] ---- (8)I-3.2 Fluorination Reaction Utilizing Highly ReactiveGas (as Method-4)
In this case, only the fluoric reaction wasinvestigated, since chemical reagents which can naturally
generate radical carbonyl species at ambient temperature
Table 3 Effect of chemical forms of U on removal efficiency.

Fig.9 Effect of reaction time on the efficiency of U
with ClF3
have not been known.

To
determinethefeasibilityofdecontamination at ambient temperature by a highly
chemical fluoric reaction, tests using glass-plate as
the sample for pre-mounted uranium wereconducted in the varying conditions of pressure andreaction time with the ClF3 treatment. Increasing thepressure of ClF3 effected a gradually higher removal
efficiency of uranium, as shown in Fig. 8. The
removal efficiency shows a linear relationship withpressures in the range of 10 to 100 Torr; at apressure of over 100 Torr, removal efficiency was
more than 90 %. The effect of treatment time also
has a linear relationship with removal efficiency forthe time between 5 and 30 min. While the slope of
this relationship tapers off for the reaction time
between 30 and 90 min., removal efficiency
continues to increase during this period, to over
95 % (Fig. 9). From the results, it was verified that a

Fig.10 Treatment of power-form U3O8 with ClF3 at 400 Torr and 18℃ for 30min.This treatment was repeated twice

fluoric reaction at ambient temperature can beattained for the purpose of removing thesolid-deposits of uranium by converting them togaseous uranium compounds.
To observe the effects of differingchemical formations of uranium (U3O8, UO2, orother ?), stainless steel samples with pre-mounted
uranium were dried up at 150 °C, and heated in airfor 1 h at 500 °C. Results showed that the chemical
form of uranium might be transformed into U3O8 by
the pretreatment at 500 °C. As shown in Table-3, theremoval efficiency may be indeed affected by thevalency of uranium.

As showing in Fig. 10, fluorination
reactivity of ClF3 toward powder-form U3O8
accumlated was reconfirmed. By the treatmentusing 0.105 g (0.124 mmol) of U3O8, thedecreased ratio of alpha activity and gravity of
U3O8 after the reaction were obserbed to benearly identical each other. By ClF3 treatment
at 400 Torr for 30 min., and twice again atroom temperature (18 °C), 90 % of U3O8 wasremoved in gaseous form, and dark green
powder-form U3O8 became white color. The
gaseous fluoric compound and unreacted excess
ClF3 were completely trapped by the

Table 4 Technical comparison of decontamination by wet method and proposed dry method.

Halogen-filter.

I-4. Applications
The primary characteristics of gas-phasedecontamination and conventional wet-methods areshown in Table-4. The gas-phase decontamination
technology has many advantages over conventional
wet-methods; in particular, its simple control
processes and small secondary waste.
Using
the
gas-phasetreatment
concurrently with existing chemical, mechanical,
and physical treatments, high-efficiency waste
management will be attained in the not-so-distantfuture. Gas-phase decontamination will become apractical technology as soon as optimum treatment
methods and conditions have been determined. This
proposed decontamination technology based on
gaseous reaction has the ability and potential to
drastically decrease the large volumes of the large
volumes of wastes created each year or
non-incinerable radioactive wastes, which include
burned-ash, many kinds of used-metals, anddiscarded equipment.
I-5. Conclusion
In regard to a surface contamination, thenewly developed concept and technology ofgas-phase decontamination, which is an advanced
waste management technology, was proposed.

The results obtained in this study are summarized
below;(1) By the treatment of CO gas under a hightemperature and pressure using non-radioactive
elements and radioactive nuclides of transition
elements, they were evaporated with highefficiency as gaseous forms.
(2) By the simultaneous carbonylation andfluorination reactions, the co-decontamination ofcobalt-60, ruthenium-103 and uranium wasverified.
(3) In the case of stainless steel coated by a oxide
layer containing radioactive nuclides, theremoval treatment of the oxide layer by utilizing
the pretreatment with chemically reactive
supercritical
CO2
fluid
promotedthecarbonylation and fluorination reactions. It is
anticipated that the treatment by chemicallyreactive supercritical treatment will be practicaland applicable in not only decontamination ofwastes but also many other fields.
(4) From the results of tests to determine the ability
to generate radical fluoric species by the plasma
treatment of fluorine gas, uranium was removed
with high efficiency. In the case of generating
carbonyl and fluoric species using a non-toxic
gas mixture, it was verified that uranium andcobalt-60 were removed simultaneously with thehigh removal efficiencies.

Table 5 Outline of characteristics and avilability of developed gas-phase decontamination technology.

(5) Finally, from the results of the test to reconfirm
the feasibility of decontamination using highly
chemical fluoric reaction without the use ofplasma, ClF3 at ambient temperature has thepotential to remove the solid-deposits ofuranium.
By the experimental results using
non-radioactive and radioactive nuclides indicatedabove, the feasibility of this new idea was asserted.
The outline of characteristics and capabilities of the
newly-developed
technologyofgas-phasedecontamination technology is shown in Table-5.

time, dangerous working and others. The
development of an effective and usefuldecontamination technology has been expected
because the satisfying methods for tritium
decontamination have not been formerly. By thereason, in the nuclear fields, it is an important
subject to develop an effective and usefuldecontamination
technology
fortritiated
contaminants. The aim of this study is to develop
an available decontamination technology byapplying gaseous method using ozone gas.

II-1. Introduction
Until now, as the decontamination oftritiated contaminants, swiping method using wet
paper or cloth, brushing or polishing surface
contaminated, heating method to remove by
evaporation, blowing by highly compressed water,
blowing by hot water vapor, and others have beendeveloped and a part of them is being used inpractice. However, the use of them has sometimes
caused many problems such as the generation oflarge secondary wastes, high cost, long working

II-2. Experiment
In order to develop a gaseous
decontamination technology for tritium, the tests ofozone gas treatment were performed using tritiatedcontaminants. For the tests, the specimen sheets
sized 20mm x 20mm x 1mmt of non-treated (NT)SS-304 rolled, electrolytic polished (EP) SS-304
rolled and aluminum (A-5052) contaminated bytritium were prepared. After cleaning thespecimens by heating in a vacuum, they were
contaminated by exposure to tritium gas (T2) ofpurity 40.4 % and pressure of 2.5 Torr at 300 K for
6 hours.

Fig.11 XPS C 1s levels for SS-304 after sputtering of
60 sec and no sputtering for ozone treated and notreated.

Fig. 12 XPS Cr 2p levels for SS-304 after sputteringof 60 sec and 600 sec for ozone treated and notreated. (M-Metalic chromium, O-Chromiumoxide)

II. Dry Decontamination for Tritiated Wastes2)

Fig.13 XPS O 1s sputter profile of SS-304 for anozonized air and no treated.

Using the specimens contained tritium, thedecontamination tests of tritium were performed
under the conditions of heating temperature of 400
K, exposure time of 1 hour or 3 hours, ozone gas
concentration of 0 ppmv (as a reference) and 400
ppmv, and gas flow rate of 150 ml/min. Ozone gas
was produced by ozone gas generator
manufactured by Masuda laboratory Inc. In the test,
the discharged tritium from specimen wasrecovered and trapped in water bubbler by flowing
air through Hopcalite (as oxidant) heated at 823 K.
In order to evaluate the treatment effect anddetermine the temperature effect of tritium

decontaminated, the reference test was performedin the same condition using the air without ozone.
The specimens before and after treatment
were measured by imaging plate autoradiography(ARG; made by Fuji Film Co., model BAS-2000)
toevaluatetheefficiency
oftritium
decontamination by comparing the activities oftritium existed on the surface. The contact time of
specimen to ARG was for 1 hour, and the detection
sensitivity of beta ray of tritium was about 6.7
Bq/PSL(Photo-Stimulated
Luminescence).
Furthermore, in order to observe the chemical statechanges on the surface and in inside of it by theozone treatment, the analysis using XPS(Photoelectron X-ray spectroscopy; made by
Physical Electronic, model PHI-1600) was
conducted.
II-3. Result and Discussion
Tritium contained in the specimens wasdischarged by heating (1073 K) in argon gas flow,
and the discharged tritium was converted to waterby Hopcalite, then it was trapped in H2O bubbler.
From the analytical result measured by liquid
scintillation counter, the total amount of tritiumcontained in the specimen was average about
1x104 Bq, and the absorbed activity of tritium on
the surface was about 2,000 Bq each side. It wasdetermined that tritium on the surface was mostly
existed as the form of tritiated water.
The experimental results of the ozone gas
treatment are shown in Fig. 11-13 and Table-6.

Fig.14 Decontamination system of robot

From the results, the efficiency of tritium
decontamination treated with ozone gas was higher
than that without ozone, and the higher efficiencies
were obtained at the longer treatment. In the casesof stainless steel (NT and EP SS-304), thedecontamination efficiencies of over 99 % (lessthan 5 Bq/cm2 of surface contamination density)
were obtained for over 1 hour, and the effect of
surface conditions of SS-304 was not much

Fig.15 Appearance of completed robot

different. On the other hand, the decontamination
efficiencies of aluminum (A-5052) were 80-86 %.
By compared the results of SS-304 and A-5052, it
was assumed that H2O and HTO (T: tritium) may
be more strongly adsorbed to the hydroxide layeron the aluminum surface than that of stainlesssteel.
The analytical result using XPS of the
carbon atom on the metal surface with and withoutozone gas treatment is shown in Fig. 11. From theresult, C-1S peak of SS-304 in the case withoutozone treatment (dotted line) was very high, but
the C-1S peak decreased to about 1/5 with ozone
treatment (continuous line). From the result of Ar
sputtering treatment (etching rate for 60 seconds:
3.9 nm depth as SiO2), it was observed that thequantity of the carbon atom in inside of surface
layer decreased by ozone treatment, as well. The
result indicates that an organic substance combinedwith tritium may be removed by ozone treatment.
The change of Cr-2P chemical shift by theozone treatment is shown in Fig.12. After Ar
sputtering treatment for 60 s to remove the effectof the organic substance on metal surface, theCr-2P peaks of both oxide and metal wereobserved. By the ozone gas treatment, the peak ofmetal decreased and the peak of oxide became
dominant. The oxide peak of Cr-2P after Ar
etching for 600 s increased largely. The result wasproven that the oxidation was proceeded in inside,and it was also confirmed from the sputter profileof the oxygen shown in Fig. 13. By the ozone
treatment, the thickness of oxide layer grew several
times, and it is assumed that the adsorbed tritium

Fig.16 Principle of dry decontamination for tritiatedwastes.

was consequentially removed.
II-4. Application: Decontamination Robot for
Tritiated Contaminants3)
For a routine cleaning and a primarydecontaminationofdecommissioning,adecontamination robot based on dry method ofozone gas treatment was developed for tritiatedcontaminants.
The
robot
sized
of
720(W)x850(D)x1,050(H) mm with a remote andautomatic system consists mainly of a flat
decontamination vessel of about 1,000 cm2 forozone exposure with a heater and surrounding
rubber curtain for preventing suction of outer air,ozone gas generator of surface discharge typemade by Masuda Institute Co., a cooling vessel for
hot air with ozone, a moisture trap packed
molecular-sieves for dryer, and circulation pump.
The characteristic of the robot is non-exhaustion
type for preventing tritium scatter, and a hot air(120 ℃) of 20-30 L/min with ozone about 400
ppmv controlled is continuously circulated in thesystem of the robot with trapping tritium
decontaminated. The decontamination system andthe appearance of robot with self-driving loaded
battery are shown in Fig. 14 and Fig. 15.
The robot is suitable for using as a routine
cleaning and a primary decontamination of
decommissioning. In the future, the robot must be
advanced to be useful in a practical site.
II-5. Conclusion
With regard to tritiated contaminants, a
newly developed concept and technology ofgas-phase decontamination, which is an advanced
waste-management technology, were proposed.
This study obtained the following results;
1. By the treatment of exposure ozone gas of 400
ppmv at 400 K, in the cases of stainless steel,the decontamination efficiencies of over 99 %were obtained for over 1 hour.
2. By the treatment in the same condition, thedecontamination efficiencies of aluminum were

80-86 %.
3. By the treatment of ozone gas, the quantity of
the carbon atom on the surface and in insidelayer were decreased, and the oxidation on
surface and in inside was proceeded.
An assumed principle of the tritium
decontamination by the ozone gas treatment isshown in Fig. 16. It is considered that the tritium
exists in 3 places that (1) in the organic substanceadsorbed on metal surface, (2) the metal atom (notoxide) existed on the surface by chemical
adsorption, (3) the metal phase in inside bydiffusion. By the ozone gas treatment, it may be
assumed and expected that (a) the oxidation oforganic substance on the surface combined tritium
is proceeded and tritium is easily released as aform of water, and (b) the recombination, releaseand diffusion to the surface of tritium areprevented by a rigid oxide layer generated.
The ozone gas treatment is easy to use andapply in practice with a simple and safe operation.
Furthermore,gas-phasedecontamination
technology
hasmany
advantages
overconventional wet methods, in particular, its simple
control processes and small secondary waste. The
proposed decontamination technology has thesufficient ability and potential to simplify adecontamination operation and reduce the large
volumes waste.
References
1. Katsuyoshi Tatenuma, Yukio Hishinuma, Satoshi
Tomatsuri, Kousaburo Ohashi and Yoshiharu
Usui, "Newly Developed Decontamination
Technology based on Gaseous Reactions
Convertingto
CarbonylandFluoric
Compounds" NUCLEAR TECHNOLOGY, vol.
124, pp.147-164 (1998).
2. Takeshi Itoh, Tetsuji Ueda, Katsuyoshi Tatenuma,
Yuji Torikai, Masao Matsuyama and Kuniaki
Watanabe, “Dry Decontamination for TritiatedWastes” 6th International Conference on Tritium

Science and Technology; TRITIUM 2001 (Nov.
2001) in printing.
3. Hajime Aoyama, Tetsutaro Seki, Kazuyoshi
Ishikawa, Shunsuke Hosokawa, Takeshi Itoh,
Katsuyoshi Tatenuma, Masao Matsuyama andKuniaki Watanabe, “Decontamination Robot for
Tritiated Contaminants” 6th International
Conference on Tritium Science and Technology;
TRITIUM 2001 (Nov. 2001) in printing.