富山大学水素同位体科学研究センター研究報告29 ･ 30 : 89‑96, 2010.

Present State and Future Subjects of Tritium Measurlng Techniques
Masao Matsuyama

Hydrogen Isotope Research Center, UniversiO) ofToyama
GojTuku 31 90, Toyama 930‑8555, Japan

Abstract
A tritium measuring technique is one of key technologies for the precise control and safe handling of fuelparticles in the fusion systems. A variety of techniques have been already established so far formeasurements of low‑level tritium such as a tracer of chemical reactions and environmental tritium.

However, high‑level and hugeamount of tritium is applied to the fusion reactors･ Some techniquesdeveloped so far are applicable for fusion environment, but new techniques will be also required forestablishment of a tritium plant in future fusion reactors. From this viewpoint, application of P‑ray‑induced

X‑ray spectrometer (BIXS) for highly tritiated waters is describeqwith the conventional devices, where the
BIXS was newly developed by author to measure high‑level tritium in‑situ･ Present state and future

subjects oftritium measurlng teChniqueswiIl be discussed in this paper･

Key words: tritium, high concentration, measurement technique, BIXS, fusion reactor

tritium over a long period. Stability of the

Ⅰ. Introduction

lt is indispensable to establish themeasurlng devices is very important totechniques fわr precise control of tritium

control the concentration and/or amount ofspecies fTrom view points of safb handlingand economy of high‑level tritium in the
futurefusion reactors. For this reason,

applicability of a variety of the present

measurlng techniques has been examined

Table 1. Major physical properties of a tritium
atom.

PhysicaIProperties 蒜
DecayScheme

ふ4Massof3日

Rｸ<

耳

ﾈ

C

ｦr

ﾖ

c

MaximumEnergyofβイaySfor high‑level tritium in gaseous

ﾇVW2

ﾂ

ゅS霧Ub

and/orAverageEnergyofβ‑rays 迭縱

ｶUb

ModeEnergyofβ‑rays經ｶUbdevelopment of new measurlng techniques

TotaはnergyofβイayS2繙ﾕrhave been conducted so far to determine

Half‑一ife"

DecayConstant縱

liquid state. Furthemore, research andprecisely the amount or concentration oftritium.

Most of these techniques, however, haveno examination exposed to high‑level

6

'茶CS

ﾓ

B

ﾓ

SpecificActivity

Ce'

MaximUmRangeofβ‑raysゅdﾄﾆﾖ也v

RecoilEnergyof3He紮UblonizationEnergyof3H

R綏Ub

ﾖ

ﾂ

FW"

89

Masao Matsuyama

tritium in afusion reactor. In addition, highdurability as well as high perfbmance is

3H一一一>3He+e一十V一十Q

MaximumEnergy:18.59keV･JN‑^tESUaluPaZ!leuJLON

AverageEnergy:5.70keV

0▲UOO .8 6 4 2

required to the measurlng devices underMaxhtensity:2,50keV

TotatEnergy:33.8LIW/Ci

the severe conditions in afusion reactor.
From these viewpoints, present state andfuture subjects of tritium measurlng
techniques toward establishment of afusion reactor will be discussed in this

0

2

4

6

8

10

12

14

16

18

Energy of β‑partlCles, E / keV

paper･

Fig. 1 Energy spectrum ortritium β‑rays.

II. Basic Properties of Tritiumthe β‑rays emitted fTrom tritium atoms is

Physical properties of a tritium atom

have been clarifled as shownin Table 1.

shown in Fig. 1. No electromagnetic
radiation comes fTrom nucleus. AlthoughWhentritium

atoms

decay,

β‑raysareemitted丘om nuclei. The energy spectrum ofpenetration power of the P‑rays is very weak,a part of kinetic energy ofβ‑rays is

Table 2. Summary ofhalf‑life oftritium nuclei.

Year
1940

陪

紊

ﾆbﾖﾆ貿Rﾅ坊
ﾓ貳ﾂ

1940 薙
ﾓ"

氏,D.0'NealandM.Goldhaber,Phys.Rev.,58(1940ー574.

ﾓ

絣

A.Novick,Phys.Rev.,72(1947ー972,

1947

繆

1949

"紊h

ﾓ

G.H.Jenks,∫.A.GhomleyandF.H.Sweeton,Phys.Rev.,75(1949)701.

1950

"紊h

ﾓ

G.H.Jenks,F.H.SweetonandJ.A.Ghormley,Phys.Rev.,80(1950ー990.

ﾓ"

M.Goldblatt,E.S.RobinsonandR.W.Spence,Phys.Rev.,72(1947)973.

1951

"紊

ﾓ

1955

"

ﾓ

1958

"經

1963 " SX ﾓ∫.F.Eichelberger,G.R.GroVeandLV.Jones,USAECReportMLM‑1160,MoundLaboratory, (1963).

ー963 " SX ﾓ

J.F.Eichelberger,G.R.GroveandL.V.Jones,USAECReportMLM‑1176,MoundLaboratory, (1963).

1966

"

1967

"

Ch

1967

"

X

1977

"

1980 "紊8 ﾓ

c(

B

W.M.Jones,Phys.Rev.,$3(1951)537.

B

ﾓ

W.M.Jones,Phys.Rev"100(1955日24.

M.M.Povov,I.V.Gagarinskii,M.D.Senin,I.P.Mikhalenkoandl.M.MorozoV,Atomnaya
Energiva.4(1958ー296.

ﾓ

2∫.S.Me汀ittandJ.G.V.Taylor,ReportAECL2510,ChalkRiverLab.,1966.

ﾓ

"

ﾓ

K,C.Jordan,B,C.BlankeandW.A.Dudley,J.lnorg.Nucl.Chem.,29(1967)2129.

P.M.S.Jones,∫.Nuc1.Mater.,21(1967)239.

#8

ﾓ

B

C.R.RudyandK.C.Jordan,ProgressReportMLM‑2458,USDOE,MoundLab.,1977

R M.P.UnterwegerB.M,Coursey,F.J.Schima,andW.B.Mann,Tnt.J.App1,Radiat.Isot.,31 r1980ー611ー

1987

"

ﾓ

1987

"

ﾓ

1987

"

(

ﾓ

2

J.J.Simpson,Phys.Rev.C,35(1987)752.

1988

"

s

ﾓ

32

Y.A.Akulov,B.A.Mamyrin,LV.Khabarin,V.S.YudenichandN.N,Ryazantseva,Pis'maZhJ
Tekh.Fiz‥14r1988ー940.

8

ﾓ

1991

"

2000

"

2000

"

2004
2006

90

References

LW.AlvarezandR.Comog,Phys.Rev.,58(1940)197.

1940
1947

'2

L.W.AlvarezandR.Comog,RadioactivehydrogenPhys.Rev..,57(1940ー248.

"

ﾓ

(

"

B.BudicandH.Lin,Bull.Am.Phys.Soc.,32(1987日063.
2

ﾓ

cH
ﾓ

2

2

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ﾓ

B.M.Oliver,H.FarrarIVandM.M.Bretscher,Appl.Radiat.Isot.,38(1987)959.

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イS

ﾓ

ｳ
イC度

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Present State and Future Subjects of Tritium Measunng Techniquesconverted into electromagnetic radiations

basic handling technologleS fわr high‑levelsuch as characteristic and/or bremsstrahlung

tritium infusion environment, there are five

X‑rays when the β‑rays plow through the

major teclmologies: namely, (1) basic

nearby matter. Since the penetration power

technologleS fわr supply,of these X‑rays is much stronger than that of

purification, separation and storage in athe β‑rays, they can be used as a probe of

mainfuel circulation system, (2) breeding

tritium detection as described later.

and recoverlng teChnologleS Or tritium

recovery,

The half‑life of tritium nuclei is one ofin伯om the blanket system, (3) enclosing

very lmpOrtant physical constants, and it has

technologleS by multi‑enclosure andbeen.examined by many researchers since

establishment of high permeation barrier, (4)discovery oftritium as shownin Table 2 [1].

decontamination technologleS fわr various

Several methods have been applied tocontaminated materials and fわr liquid waste

determine the half‑life of tritium nuclei.

Measurements of changes in theradioactivity of tritium by an ionizationchamber and a proportional counter wereapplied to determination of the half‑life. In
addition, calorimetric method and3Hemeasurement had been also applied to thispurpose. At the present time, most reliablehalf‑lifTe of tritium nuclei is 4500±8 days
(12･32±0.02 years)･ However, if the present

halfllifTe is applied to the amount of tritiumin afusion reactor, a fairly large amount oftritium shall be unknown aRer a long period.
For example, when initial loading amount oftritium is 10,000 g, it decreases to 5697±5 gafter 10 years by decay only. Namely,

Fig. 2 Schematic diagram of the fuel circulation
system for fusion reactor.

such as tritiated water, and (5) Common
technologleS related with tritium measurlng

uncertainty or the amount of tritium willtechniques fわr measurement of tritium

reach to ±5g.

partial pressure (or concentration), analysesof chemical fbm of tritium species,

Ill. Main Fuel Circulation System in a

Fusion Reactor and Related TechnologiesA

fuel

circulation

systemis

indispensable to operate continuously afusion reactor by supplying and recoverlng

fuel particles. Schematic diagram of the fuelcirculation system is shown in Fig. 2. As f♭restimation of a partial inventory in a

sub‑system ofthefueling system, and so on.

To satisfy the fifth teclmology
mentioned above, a variety of devices andtechniques must be provided in advance toanalyze tritium species in various physicaland chemical states as shown later. Most

91

Masao Matsuyama

important functions of these devices

arehigh reliability and durability over a long

period.

IV. Techniques for Tritium･Measurements
lt is necessary to measure tritium
concentration in a remarkably wide range
fTrom environmental level to fusion

fuellevel as shown in Fig. 3. In addition to therange of tritium concentration, not only
elemental tritium but also different chemicalfTormof tritium species such as oxidized
tritium and tritiated hydrocarbon increase

with the operation time of afusion reactor.
Tb evaluate such tritium concentration, mostsuitable device fわr each tritium species willFig.

have to be prepared.

3

Tritium

concentrationinfusionenvironment.

Various devices have been developed so

autoradiography, window‑less G‑M counter,far f♭r tritium measurements as shownin

electret dosimeter,and P‑ray‑induced X‑ray

Table 3. Upper three methods in the table

spectrometer (BIXS). The last one is a neware categorized asanabsolute measurement
method.

Theothersarere1

method that was recently developed by

alive

Matsuyama et al. as a nondestmctive

measurement methods and widely used fわrmeasuring method l2].Anexample applied

tritium measurements. In addition to thesethis technique will be described in the next

methods and devices, some techliques are

SeSSIOn.

applicable: for example, imaging plate (IP),

Table 3. List of the measuring devices for tritium.

CommonWorkingR∈lnge

6

gas 免
Volumetry凵̀abOVe370MBq

Gravimetry凵̀above3.7GBq

Calorimeterｲ
辻

GasChromatographyｲｲ凵̀aboVelPa

LaserRamanSpectrometer
ElectronML川iplier

ｲ
ｲ

‑
‑

37mBq/cm3‑carrier
ProportionalCounter
lno

Liq

凵̀below370kBq

貞66也F剃6〜belOw370kBq

辻

W

"

△

&vV

△

‑

&ｲ

"

W&宥芳

g

W&宥芳

V蹤

△
△

W

F

遊ﾒ

W7Fv

fVdfﾇVV蹤v

柳fﾆ

芳W

F

gG)

fW

6W76ﾆ誥

‑

‑

○

Vﾖ

g

&免宥柳f匁g&

&緬
&

ｲ

ﾖ

6W76匁v
F

F

‑
辻

VﾖV蹤

6W76匁v

ｲ

○

V

&

A

free

VﾖV蹤

免

"

"

ｲ

V

&

○

儚eal‑time

ｲ

ｲ

V蹤W"

〜below370kBq

92

"

△

凵̀below37GBq

BnfraredAbsorpLSpectrom.

W

0

FR

solid

辻

△

凵̀aboVe3̲7GBq

MassSpectrometer

‑

ﾇ7F

V烹

&VF&V

ﾖ也FV

6W&&V

Vﾇ&VﾖV蹤

g

U7Fv

6W2

ﾖ&W%f

ﾖR

VV

匁vv

A

&

6W76匁v
△

fﾆ

宥

ﾖ也FV

fW

V襷匁v

6W2

6W2

V萌v

7FR

2

Present State and Future Subjects of Tritium Measuring Techniques

V. New Device for In‑Situ Measurement￠50.5lof Highly Tritiated Water

￠41.5

鳴

Generation of highly tritiated water isinevitable in the fuel circulation systemand
tritium breeding blanket system of a且lSion

reactor. It is well known that a liquid

scintillation counter (LSC) is widely used
NaⅠ(Tl)ScintillationProbe

fTor determination of tritiumconcentration in
the water. Measurements by a conventional

Fig. 4 A cross‑sectional view of a new
device to measure highly tritiated water.

LSC, however, are limited below about a

few hundred kBq/cm3 due to saturation of aphoto‑multiplier. To measure highly
tritiated water above this level it is requiredN(cpm)=(6.94±0,01)X10ー2C‑(9.43±5.31)X10 2｣･ul∈SlunOD/〜■aleJ6ul unO3

to dilute the tritiated water with nomal
water up to the suitable tritium

concentration. This process is dangerous
procedures as well as enlargement of error.

TherefTore, development of a new device
100

which is able to measure in‑situ highly

1

01

102

103

104

105

TTitlum COnCentratl0n determlned by LSC, C / kBq cm‑3

tritiated water had been desired.
Fig. 5 Calibration cuⅣe of the new device fわr

Figure 4 shows a schematic diagram of ahighly tritiated water･

new device, which is based on the method
figure, a good linear relation appears in aor BIXS mentioned above. A part of energy
higher reg10n than 4 kBq/cm3 0f tritiumof β‑rays emitted in the tritiated water isconcentration [3].

converted into bremsstrahlung andcharacteristic X‑rays in the water. These
ⅤⅠ. Material Dependence or Tritium

X‑rays penetrate through a thin beryllium
lnventoIY
window, and enter the specially designed

A serious problem is still remained in

X‑ray detector. The beryllium surface
the development of a detector tTor high‑levelcontactlng With water was covered with aelemental tritium. When a tritium detector isthin gold film to avoid the erosion of
exposed to elemental tritium, a part of theberyllium surfTace. The present device istritium gas adsorbs on the surface and thenapplicable to not only a batch system but
it dissolves into the bulk through surface

also aflow system of tritiated water. Figure

layers. A background level of the detector

5 describes the calibration cuⅣe preparedbecomes high owlng tO the residence ofby uslng the conventional LSC which wastritium on the surface and in surface layers
previously calibrated uslng the standardof detector materials, which is so‑called

tritiated water. As seen clearly from thememory effect. This phenomenon disturbs

93

Masao Matsuyama
T(JC)precise measurements and gives rise to
1600

10‑0

increase in the lower detection limit. It is

800

400

200

100

indispensable to research and develop new
11111 0 To o ePo o

RlnCtional materials available to theatmosphere or high‑level tritium.

(soedrJ .te)卓二qn10S

Figure 6 shows the solubility of tritium

infusion r.eactor materials l4]. Both ofendothemic and exothemic reactions withtritium are described in the figure. As seenclearly fTrom the figure, solubility of tritium

0in W, Al, Mo and Cu at lower temperatures
is less than that in stainless steel which is

widely used as a structural material infusion
related devices. Although these materials are
0.0

advantageous fわr tritium handling devices

0.5

1.0

1.5

2.0

2.5

3.0

1000rT (Kll)on account of low solubility, it is hard tomachine W and Mo materials owlng tO low

Fig.ー6 Solubility of tritium in various materials.

ductility and high hardness. On the other
hand,

Al

and

Cu

materials

0. o a 4 3 2

are(uV)L u!∈Stun8＼N‑aleJ6u!lunO3

disadvantageous because of lack ofmechanical properties. However, it ispossible to make up weak polntS by alloylng
and surface modification of these materials.

For example, hardness of Cu‑Be alloys is

0

0. 1

0

almost same as that of stainless steel, andsurface hardness of AI can be improved by02

surface coatlng With a thin TiN film.
It is known that the tritium concentration

4

6

8

10

12

14

16

18

Energy of Xrays, E/ keV
Fig･ 7 Ⅹ‑ray spectrum induced by β‑rays emitted&om tritium.

in surface layers of stainless steels isremarkably enriched in comparison withsolubility of tritium in Cu‑Be(2 mass %)that in the bulk l5]. Surface concentration ofalloy was examined at low temperatures.

tritium gradually increased agaln by

Figure 7 describes an example of X‑ray

diffusion fTrom the bulk, if tritium atoms

spectra measured by ド‑ray‑induced X‑ray

trapped in the surface layers could be

spectrometry (BIXS), a氏er the Cu‑Be alloy

removed by a special decontamination

samples were exposed to tritium gas at

method. Namely, it is very lmpOrtant tO

623K fTor ll hours. The total pressure of

reduce the tritium concentration in the bulk

tritiumgas was 1.3 kPa,and the tritium

as well as the surface. From this viewpolnt,

concentration was 0.4%. The details of

94

Present State and Future Subjects of Tritium Measurlng Techniques

BIXS are shown in elsewhere [6]. A sharp
and intense peak is the characteristic X‑ray?∈obg/o■ag･nou!uo!)taJIuaDu8∈n!Pト

111 0 0 0 0 0 0

Trltl um E耶ure Cordtl耶● ● ● ●●tpeak of Ar, which is mainly induced by

SarrTde. CLトBe dlcy

Terrp 350

tritium adsorbed on the surface. On the0cTlrne ll hTS
TntIUmPressure 1 3炉aother hand, broad and weak peak is the

Tritium Cα芯 0 4%

bremsstrahlung X‑rays, which is caused by

27X10 4Bq/cm 3●

theinteractions

betweenβ‑raysflt1‑I‑ll‑+‑I.‑.‑‑I

andconstituent atoms of the sample･ The shapeof this peak depends on a depth profile of

50

1

∝)

1

50

200

250

Distance from su什ace. d / pm

tritium in the bulk･ The observed spectmm
Fig･ 8 Depth profile oftritium in Cu‑Be alloy･

indicates that a large ftaction of tritium isrelatively trapped on the surface and inproperties of the Cu‑Be alloys.

surface layers in comparison with the bulk.
Figure 8 shows the tritium depth profile

measured by a chemical etching methodVII. Important Issues toward Future

Fusion Reactors

after measurement of the X‑ray spectrum

SafTe and precise control of a hugementioned above･ Although high tritium

amount. of tritium will be required fわr aconcentration appeared in surface layers

future fusion reactor･ Additionally, lt is notwithin a fTewトlm aS Suggested fTrom analyses

clear whether the present measurlng devicesof the X‑ray spectrum, tritiumConcentration

are durable enough fわr a continuously longin the bulk was almost constant as 2.7Ⅹ104

run･ For these reasons it is necessary to

Bq/cm3, which corresponds to 3･8xlO15

improve the existlng methods andatoms/cm3. The number of metallic atoms intechniques and to develop new measurlng

cu‑Be alloy is 8･76xlO22 atoms/cm3, which

methods and techniques applicable to a

was evaluated uslng lattice constant of thefusion reactor･ Therefわre, the fTollowlng

alloy estimated fTrom an X‑ray di軌action

issues must be examined to establish thepattern･ Atomic fiaction of tritium in alloy

tritium plant in the fusion reactor.

was as low as 4.33Ⅹ10 8. From this atomic

斤action, solubility of tritium at 623K was[lHmprovement of existing methods andtechniques :

estimated as 1 ･2xl0‑9 at･fr･/paOl5, Considering(1) Reduction of memory effTects: to reduce

the total pressure of tritium gas. It was seen,

the amount of tritium adsorbed on thetherefわre, that the solubility of tritium insurface and that absorbed in surface

Cu‑Be alloy was below around 1/400 inlayers of the detector materials.

comparison with that in SS316 described in(2) Increase in durability: to be long‑lifTe

Fig･ 6･ The result indicates that Cu‑Be alloyand maintenance fTree (or easy maintenance)is one of promlSlng materials f♭r tritium(3) Increase in sensitivity: to extend a

handling devices. However, more studies

working range, especially improvlng

will be required to improve surface

lower detection limit.

95

Masao Matsuyama(4) Increase in precision and accuracy: toReferences

increase in stability of the detectors.
and simpliflCation: toll] L.L. Lucasand M.P. Unterweger, J. Res.

lower tritium inventory and trouble

Natl. Inst. Stand. Teclm01., 105 (2000)

frequency.

541‑548.

(5) Compactness[2] M. Matsuyama, K. Watanabeand T.
[2】

Development

of

new

measuring

Yamazaki, Fusion Eng. Teclm01., 28 (1995)

methods and techniques:

1045‑1049.

Various kinds of chemical formand physical[3] M. Matsuyama, Y. Torikaiand K･state of tritium exist in the fusion system. In

Watanabe, Fusion Sci. Techno1., 48 (2005)

addition to this, many kinds of radioactive

324‑331.

nucleus produced by neutron irradiations[4] F. Reiter, K.S. Forcey and a GeⅣasini,also coexist in the fusion system. The best

EUR 15217EN, (1993).

method should be applied to each system[5]

and purpose. Various methodsand teclmiqueMatsuyama and K. Watanabe, J. Nucl.

have to be provided fTrom viewpoint ofMater., 3291333 (2004) 1624‑1628.

precise control and evaluation of high‑level[6] M..Matsuyama, K. Watanabeand K.

tritium.

Hasegawa, Fusion Eng. Design, 39/40

Y

Tbrikai,(1998) 929‑936.

96

良.‑D.

Penzhom,M.