Fujita Technical Research
ReportNo.43 2007

Low-Activation Reinforced Concrete Design Methodology-Fundamental Investigation for various Types of Low-Activation ConcreteKen-ichi Kimura, Masaharu Kinno, Hirokazu Nishida, Noritcika Katayose,
Mikihiro Nakata2), Katsumi Hayashi3), Mikio Uematsu4) and Akira Hasegawa1)

Abstract
Concrete is very useful and inexpensive material. However after long-term use in a nuclear powerplant
it can become both expensive and difficult. One possible solution to this problem is the use of low-activation
concrete, which has much less residual radioactivity even after many years of operation. In this paper, weevaluated fifty raw materials by radiochemical analyses, which assessed the quantities of dominant traceelements for the activation under specific conditions. From these investigations, three kinds of aggregates(fused alumina ceramics, silica sand and limestone) and two kinds of cements (high alumina cement andwhite cement) were selected as raw materials for the low–activation concrete. Finally, six types of
low-activation concrete and two mortars were proposed and their mix proportions described so as to makethem suitable for different areas within nuclear plants. Areas of investigation for further improvements
were also identified.

§1. Introduction
to the decommissioning of nuclear power plants. The
Concrete enveloping a nuclear reactor retains

key areas of programme include; investigation ofresidual radioactivity after decommissioning. Disposal

residual radionuclides in construction materialsof such radioactive concrete is very costly and requires

around a reactor, improvement and development ofstrict supervision. From this point of view, we have

low-activation

developed a new concrete that retains little residual

low-activation design method for the reduction of theradioactivity – i.e. “low-activation” concrete [1].

radioactive waste below clearance level.

materials,

andestablishmentofA nationally-funded project for comprehensive

To achieve the above comprehensive project, adevelopment of the low-activation concrete has

feasibility study [3] was performed for four tasks

recently started in Japan[2]. The goal of this project isincluding two basic investigation into low-activation

to reduce radioactive concrete by half and ensure theconcrete as follows.

whole structure remains below the clearance level on

Proportioning of low-activation raw materials

decommissioning. This will contribute significantly

and improvements to low-activation cement: We

towards solving safety and economic problems relating

proposed six kinds of mixes for the low-activation raw

Keyword：

Low-Activation Concrete,
Reactor, Clearance Level, rawmaterials

1) Tohoku University, Sendai, Japan
2) Mitsubishi Heavy Industries, Ltd., Kobe, Japan
3) Hitachi, Ltd., Hitachi, Japan
4) Isogo Engineering Center, Toshiba Corporation,
Yokohama, Japan－19－

Fujita Technical Research Report No.43

Table 1. Estimated waste of the typical nuclear plants after operation[Unit: 107 kg]

Criteria for waste

BWR (1.1GW level)

PWR (1.1GW level)

GCR (1.1GW level)

meta

meta

meta

concrete

total

l
Low

level

concretetotallconcretetotallradioactive 0.9

0.4

1.3

0.4

0.2

0.6

0.3

1.8

2.2

Not necessary to treat as 2.1

0.7

2.8

0.3

0.8

1.2

0.6

3.6

4.2

0.8

48.7

49.5

3.4

44.3

47.7

1.0

11.9

12.9

3.8

49.8

53.6

4.1

45.4

49.5

1.9

17.3

19.2

waste
radioactive waste
Not radioactive waste
totalmaterials to make low-activation concrete, which§2.

Criteria of clearance level for radioactive

reduction ratios to the andesite concrete were fromconcrete waste

1/300 to 1/10 in Di/Ci unit, where Di is theconcentration of the radionuclide i and Ci was the

As well known, concrete is a very useful andclearance level of the radionuclide i. Three kinds ofinexpensive material, and is used in variety of

improvement plans for low-activation cement wereapplications, including buildings and infrastructure.

also proposed.

Concrete is also used in nuclear plants as a

Investigation of method for development of
low-activation

concrete:Themethods

structural member and shielding wall againstforradiation and radioactivity. Certain radiation,

development of low-activation concrete and mortal

typically neutron radiation, may make concrete

which reduction ratio to the andesite concrete wereradioactivefrom 1/300 to 1/10, were investigated to apply to thephenomenon is called “activation”, and which

reactor shielding wall of the boiling water reactor

concrete subjected to it can be called “activated(BWR) and to the shielding wall of the pressurized

concrete” [4].

undercertainconditions.

Thiswater reactor(PWR). The results indicated thatIn this case, the concrete can become

application of low-activation concrete was economic,

expensive and hard to deal with. Activated concrete

greater construction costs being more than

may need to be treated as radioactive waste at theoutweighed by reduced quantity of radioactiveend of the operation. In this case, there are major

waste requiring costly disposal

cost

implications

associatedwithspecialist

From the results of the feasibility study, we

demolition, and underground storage. The costs ofdescribe outline of the results relating to both thedealing with radioactive waste are estimated asconcrete itself the raw. Fundamental technicalbetween 65 times and 2800 times greater thanissues are discussed first, followed by investigation

construction costs for ordinary concrete (based onof the potential low-activation. Finally, six types ofthree differing levels of radioactivity for two type of

low-activation concrete are proposed. Their mix

reactors, as outlined in an intermediate report byproportions

Ministry of International Trade and Industry) [5].

areassessedagainsttargetcharacteristics, considering the application of the

However, most of the concrete used in the

proposed concrete to the certain portion of thenuclear plant is not highly radioactive waste

member in nuclear plants.

requiring strict supervision. Table 1 gives an idea ofthe quantity of the waste for the typical nuclear
plant [5]. This table shows that most of the waste－20－

Low-Activation Reinforced Concrete Design Methodology-Fundamental Investigation for various Types of Low-Activation Concrete-from nuclear plants is concrete and most of thematerials for concrete were selected as candidates

concrete

waste.

for low-activation materials for low-activation

Nevertheless, concrete radioactive waste is stillconcrete. Aggregates (30 kinds of limestone, 6 kinds

4000 ton for the BWR (1.1GW level). The remainingof fused alumina aggregates, and 4 kinds of quartz

7000 ton is categorized as the waste which is notaggregates including silica sand) and cements (anecessary to treat as the radioactive waste. This

white cement and 5 kinds of high alumina cements)

waste is termed as “below clearance level”. So thewere investigated. Geo standard samples (JR-1,

possibility exists, if sufficiently low-activation

JA-1 and JB-1), standard ordinary concrete, andconcrete could be developed, that all concrete usedordinary Portland cement were also selected asin the structure could be below clearance level oncomparison samples for the above materials.

decommissioning.

Standard ordinary concrete was made from

waste

is

not

radioactive

Clearance level has been discussed toandesite aggregates, which was is the mostdetermine the line between regular waste andcommon aggregate for the concrete in Japan, andlow-level radioactive waste (LLW). International

ordinary Portland cement.

Atomic Energy Agency (IAEA) has provided

The term “low-activation” can have several

international guidelines for the LLW, specifying

meanings. For the purposes of this report, we take“basic safety standard” for LLW in the report

the term low-activation concrete to mean concrete“TECDOC-855” [6] in 1996, based on the principlethat remains is below clearance level, even afterof basic safety for the protection against the ionizing

long-term use in most portions of nuclear plants.

radiation and for the safety of radiation sources[7].

We consider “long-term use” to comprise 40 years

TECDOC-855 defines criteria to define trivial

operation and 6 years cooling (maintaining afterradiation level which poses negligible risk based onstop of the operation for 6 years).

increased cancer risk of one per million per year,

Based on above conditions, radioactive nuclides inwhich translates to 100 Sv/y, comparing to 1000

the concrete should be limited (typically 60Co, 134Cs

Sv/yallowanceand 152Eu), and therefore trace elements for therecommended by International Committee forinvestigation were selected Co, Cs, Sc, Fe and Eu

Radiation

which is are representive of rare earth elements.

forindividualProtection.

radiationSo,

TECDOC-855

recommended 10 Sv/y as clearance level criteria.

3.1 Radiochemical analysis

Japan Nuclear Safety Commission (JNSC)

The trace elements predominantly

reported clearance level from exposure estimation

responsible for the activation of concrete materials

performed using food-chain scenarios localized towere evaluated by radiochemical analyses [4], as

the Japanese lifestyle [8], based on above IAEA 10

follows,

Sv/y criteria (describing “CL-Japan1999”). On the

1. Collecting certain concrete materials

other hand, after above first report from IAEA, theyreevaluated TECDOC-855 and issued RS-G-1.7 forclearance level ([9], describing “CL-IAEA2004”).
JNSC also reevaluated exposure estimation using
RS-G-1.7

andregulatedin

2004(describing“CL-Japan2004”).
§3. Investigation for low-activation materials
Based on previous works [10], [11], [12], 45 raw
Figure 1 Configuration of the JRR-4 core－21－

Fujita Technical Research Report No.43

Table 2 Σ5Di/Ci ratio for evaluated aggregates

2. Crushing materials to certain size (typically
3. Packing above crushed samples for 0.1 to 1g
with special treatment for irradiation
4. Irradiation by thermal neutron in the reactor
core of JRR-4 (shown in Figure 1)
Thermal neutron flux:

5.3E13 cm-2sec-1

Irradiation time:

20 minutes

5. Cooling for 66 to 87 days
6. Measurement of gamma spectrum forirradiated samples by a Ge detector
7. Evaluation of quantity of the trace elements
for each sample.
3.2 Results for aggregates
From the above radiochemical analyses,
quantities of the Co, Cs, Eu, Fe and Sc for 50
samples were evaluated. Figure 2 shows the
distribution of the measured quantities of Eu and
Co in typical aggregate samples (limestone*

The ratios is to the average of JR-1, JB-1, and JA-1,
which is assumed the average aggregate.
and Co compared to those in ordinary aggregatesaggregates, fused alumina aggregates and quartz
aggregates) with those of other aggregates from(the distribution of Eu and Co for ordinary

previous works [10],[12]. This figure indicates above

aggregates is located around the center of figure,selected samples for this work have low levels of Eu

10000
10,0005D/C ratio*
0.00068
0.00260.00210.00140.00050
0.00570.65
0.00490.00076
0.014
0.038
0.020
0.00670.023
0.00850.00540.011
0.011

Aggregate
Fused alumina aggregate CA
Fused alumina aggregate JA
Fused alumina aggregate JB
Fused alumina aggregate CF
Fused alumina aggregate EA
Quartz sand JT
Quartz sand JA
Quartz sand AF
Quartz aggregate IA
Limestone aggregate FO
Limestone aggregate OK
Limestone aggregate HK
Limestone aggregate FA
Limestone aggregate FK
Limestone aggregate TH
Limestone aggregate AH
Limestone aggregate SB
Limestone aggregate KT

under 1mm)

 Di / Ci = 1.0
3

Di /Ci = 0.1

1000
1,000

Ferro-manganese(3)Ordinary aggregates

Co (ppm)

100
101

Quartzite(5)

0.1
0.01

(enlarged data shown in Figure 3)

Serpentite(9)Magnetite(2)High purity Limestone(2)Dunite(1)Bauxite(1)Syenite(1)Apatite(1)Colemanite(1) Mullite(1) Phosphate(1)Baryte(2)Limestone(12)Silica sand(1)Fused alumina(4)0.001
0.0001

0.001

0.01

0.1

Aggregate

1

10

100

Eu (ppm)
Figure 2 Distribution of quantities for Eu and Co in aggregates with enlargement of ordinary
aggregates （Numbers in parentheses indicate the number of specimens ）

－22－

1,000
1000

Low-Activation Reinforced Concrete Design Methodology-Fundamental Investigation for various Types of Low-Activation Concrete-Co(ppm)50

10neutrons, 40 years of operation, 6 years of cooling.

Andesite(34) Basalt(14)Porphyrite(5)Gravel(35)Diorite(9)Sand(20)
Crushed stone(120)
Granite(5)Sandstone(38)Ci:Clearance level referring CL-Japan2004 for thiscalculation, which are 0.1 for 152Eu, 154Eu and 60Co.
Measured limestone samples in the figure are

Porphyry(4)Silica stone(5)3Di/Cilocated within=1.0 line, and fusedalumina ceramics are located within

3Di/Ci =0.1,

inaggregatescomparison

with

other

against3Di/Ci curve. Therefore limestone, quartz,

Trachyte(4)and fused alumina were selected as low-activation

Rhyolite(2)materials.
Table 2 shows the 5Di/Ci ratio of the1

0.3

measured aggregates to the ordinary aggregate,2

11which is average ofEu(ppm)the Geo-standard samples JR-1 (Rhyolite), JB-1

Figure 3 Enlargement of the distribution(Basalt) and JA-1 (Andesite).

for Ordinary aggregates from Figure 2

5Di/Ciand isdefined by equation (2), as follows,(Numbers in parentheses indicate the number of specimens)

5Di/Ciand enlarged figure is also shown in Figure 3).

=

D55Fe/C55Fe+

D60Co/C60Co+

D134Cs/C134Cs + D152Eu/C152Eu +Figure 2 also has index curves of 3Di/Ci=0.1

D154Eu/C154Eu (2)and 3Di/Ci=0.1 for the activation. The 3Di/Ci in

Di: Concentration of radionuclide of 55Fe, 60Co, 134Cs,

this figure is defined by equation (1) as follows,

152Eu, and 154Eu induced under 2.0×105 n cm-2sec-1

3Di/Ci = D152Eu/C152Eu + D154Eu/C154Eu

thermal neutrons, 40 years of operation, 6 years of+D60Co/C60Co(1)cooling.

Di:Concentration of radionuclide of 152Eu, 154Eu andCi:Clearance level referring CL-Japan2004 for this60Co induced under 2.0×105 n cm-2sec-1 thermal

calculation, which are 0.1 for 152Eu, 154Eu, 60Co,

10000
10,0001000
1,000

3Di / Ci = 1.0
5
 3Di / Ci = 0.1

Co (ppm)

100
10
1
0.1
0.01
0.001
0.0001

Fly-ash Type B cement(av.)
Moderate-heat Portland cement(12) Low-alkali cement(av.)
Fly-ash(5)Low-heat Portland cement(6)Silica cement(1)Silica fume(5)Gypsum(5)Blast-furnace Type B cement(av.)
Low-alumina cement(av.)
Ordinary Portland cement(27)High-alumina cement(12)White cement(18)Cement
0.001

0.01

0.1

1

10

100

Eu (ppm)
Figure 4 Distribution of quantities for Eu and Co in cement
(

)

－23－

1,000
1000

Fujita Technical Research Report No.43

Table 3Σ5Di/Ci ratio for evaluated cements

Table 3 shows the ratio of 5 Di/Ci, which is5D/C ratio*

calculated by equation (2), for the evaluated some

CementHigh alumina cement FR

0.045

High alumina cement EA

0.045

High alumina cement JA

0.0040High alumina cement JB

0.056

High alumina cement JC

0.021

White cement S

0.35

Low heated Portland cement T

1.0

cements compared to the ordinary Portland cement
manufactured by A factory in Japan.
Figure 4 and Table 3 indicate that the
selected aggregates in this work are very useful forthe low-activation materials (the5Di/Ci ratio ofhigh alumina cement, and white cement to theordinary Portland cement are about 1/20 - 1/50 and
1/3, respectively).

*

The ratio is to the ordinary Portland cement, which isassumed the average cement

134Cs, and 1000 for 55Fe.

§4. Proposal of low-activation concrete

Figure 2 and Table 2 shows that aggregates

The investigation in the last section is introduced

selected in this work are very useful forpossible

low-activation materials (theDi/Ci ratio of fused

low-activation concrete. Based on that investigation,

alumina, quartz sand and limestone to the ordinary

various types of low-activation concrete are

aggregates are about 1/1000, 1/200, and 1/20,

described below.

respectively).

4..1 Supplement conditions for the low-activation

3.3 Results for cements

aggregates and cements

low-activationmaterials

for

the

Figure 4 compares the distribution of Eu and

The investigation assessed three aggregates

Co in the cements selected for this work withand two cements as potential low-activation

cements examined in previous works[10],[12]. materials for low-activation concrete from the

3Di/Ci curves, which can be calculated by equation

points of view of the activation by radiochemical(1), are also set for the index of the activation in theanalyses. Obviously, it is also very important tofigure.

investigate other conditions in actual use of theTable 4 Supplement condition for low-activation materials

Material

Di/Ci* ratio

Fused alumina

1/400 –

aggregate

1/1500Quartzite (Silica)

1/200 -

aggregate

1/1200Limestone
aggregate
High alumina
cementWhite cement

Relative cost**

Ability for

20- 40Good

5 - 10Good

Hardness

1/30 – 1/200

1.5 – 3

Good (partially N.G)

Require washing

1/20 – 1/50

30

Good

1/3

3

Good

*

Point characteristic
High density andhardness

Long term durability,
thixotropy
Heat generation

Di: Concentration of radionuclide i, Ci: Clearance level of radionuclide i, cited from IAEA-RS-G1.7, assuming the thermal neutron 2.0×105 n th
cm-2s-1, 40 years of operation, and 6 years of cooling.
**The average aggregate is assumed 1.0 for aggregates, and the ordinary Portland cement is assumed 1.0 for cements.

－24－

Low-Activation Reinforced Concrete Design Methodology-Fundamental Investigation for various Types of Low-Activation Concrete-

low-activation concrete is relative to that for theabove materials for concrete.

Andesite concrete (Andesite aggregate and ordinary

Table 4 shows the results of the investigation

Portland cement) In order to apply low-activation

related to the supplement for the above materials
such as relative cost, ability of the supplement

concrete to certain portions of the nuclear plants

and so on. This investigation was performed to theeffectively, the aspects of concrete examined for thiscompany for each of the aggregates and cements

study, such as compressive strength, shrinkages,

investigated in the previous last section, by means

and fresh concrete properties are not on their own

of enquiries, site visits and orders of a specificsufficientquantity. The Di/Ci ratios of the above materials

conditions, such as cost, durability, low-activation,

to compared with the assumed average materials

and so on, should be taken into account. Therefore(the average of the geo standard samples for

low-activation design could be very complex andaggregates and ordinary Portland cement fordifficult. Table 6 summarizes six types of proposed

cements) are also shown in the table. The Di/Ci for

concrete including two types of mortar andeach material in this table is recalculated under thecompares their characteristics, target applications

new clearance level (CL-Japan2004) focusing on

and assignments for improvement.

actual nuclear plants. The point characteristics for

Based on above mix proportions, dozens of trial

each material are also addressed in the table.

mixing and execution experiments have been

Relative cost compares the price of low-activation

performed for various types of concrete and mortarmaterials to the ordinary materials (average[13],[14]. Figure 5 shows typical results for Di/Ci ofaggregate and Portland cement).

concrete A, concrete C, and concrete D in table 5

determinantsofsuitability.

Other

This investigation confirmed realization of theand table 6 with the comparisons to of ordinary

use of low-activation aggregates and cements listed

concrete (OC: Andesite concrete). The values ofabove for the low-activation concrete.

Di/Ci were calculated under the conditions of 2.0

4.2 Mix proportion design
The

above

×105 n th cm-2s-1, only thermal neutron, 40 years ofinvestigation

reveals

operation and 6 years of cooling, and assumingsome5

BSW in BWR and a clearance level as defined insummarizes the mix designs for the six types of the

CL-Japan2004. This figure shows the results for

proposed low-activation concrete together with the

only four radionuclides, which occupied comprised

target of characteristics. In this table, Di/Ci ratio,

more than 98 % to of the total Di/Ci except

which is the ratio of Di/Ci for each designed

concrete A, for which the four radionuclides

potential

low-activation

concretes.

Table

Table 5 Mix proportion design for proposed six low-activation concrete

Coarseaggregate

CementTarget of characteristics
Di/Ci ratio*

Density (g/cm3)

High alumina cement

1/300 – 1/400

3.0

Fused alumina

Fused alumina

ceramics

ceramics

B

Quartzite

Silica sandHigh alumina cement

1/150 -1/200

2.3

CLimestone

Limestone

White cement

1/30-1/50

2.3

DLimestone

Limestone

Low heated cement

1/10-1/30

2.3High alumina cement

1/150

2.3

White cement

1/25

2.1

A

E
*

Fine aggregate

Silica sandF
Silica sand + Limestone powder
Andesite concrete is assumed 1.0.

－25－

Fujita Technical Research Report No.43

Table 6 Characteristics of six types of Low-activation ConcreteA

B

Characteristics

Target application

Assignment Areas for improvement

Ultra low-activation (Di/Ci ratio is
expected 1/300), high density, good
property for heat resistance and highthermal conductivity

Reactor shielding wall for BWR, inner portionof shielding wall for PWR, and partial spot forhigh neutron yield

Expensive, high drying shrinkage, Long term
durability, thixotropy, heat generation anddifficulty for execution work

Reactor shielding wall for BWR, inner portionof shielding wall for PWR, and partial spot forhigh neutron yield

Expensive, high drying shrinkage, Long term
durability, thixotropy, heat generation, difficultyfor execution work and not for use in hightemperature

Very low-activation (Di/Ci ratio is
expected 1/150)

C

Low-activation (Di/Ci ratio is expected
1/30 to 1/50) and could be moderate typeas balance of cost and performance.

Biological shielding wall for BWR, and outerportion of shielding wall for PWR

Further improvement of white cement for
low-activation, and heat generation duringexecution work

D

Relatively low-activation (Di/Ci ratio is
expected 1/10 to 1/30), and inexpensive
Limestone

Biological shielding wall for BWR, and outerportion of shielding wall for PWR

Further improvement of low heated cement for
low-activation

E

Very low-activation (Di/Ci ratio is
expected 1/300) and good property offilling

Reactor shielding wall for BWR, inner portionof shielding wall for PWR, partial spot forhigh neutron yield and infilled mortar

Expensive, high drying shrinkage, Long term
durability, thixotropy, heat generation, difficultyfor execution work and not for use in hightemperatureF

Low-activation (Di/Ci ratio is expected1/25), and good property of filling

Biological shielding wall for BWR, outerportion of shielding wall for PWR, and infilledmortarFurther improvement of white cement for
low-activation, and heat generation duringexecution work

comprised is about 90 %. By From the results ofshould be carefully selected, especially Co and Eu

these calculations, the Di/Ci ratio of concrete A tocontent of in the cement. As mentioned in section 3,

OC is 1/323, that of concrete C to OC is 1/31 andEu and Co are dominant materials for activationthat of concrete D to OC is 1/10, respectively.

under the conditions described in this paper.
Heat generation during execution work may

4.3 Areas for further improvement

cause unacceptable cracks [15], so it is also very

Most of the problems described in table 6 forimportant for the decreasing the heat generation.

the six proposed low-activation concretes are caused

We have developed a method to reduce the heatby the cements. The problems for the concrete

generation for the concrete with white cement by

where high alumina cement is used are typicallyadding a low-activation admixture. This could behigh drying shrinkage, long term durability,

one of the ways to improve heat generation for thethixotropy, and heat generation. Those for theconcrete with white cements and alumina cements.

concrete where white cement is used are heatLong term durability is another problem forfor

use of high alumina cements, and may improve by

low-activation and the assignment for the concrete

the using a mix proportion with low W/C (the ratio

in use of low heated cement is further improvementof water to cement) under 40% [16].

generationandfurther

improvementof low-activation.
§5. Conclusion

In order to achieve further low-activation
cement for white cement and low heated cement,In

raw materials used in the manufacturing stage

－26－

2004,

a

projectbegan

todesignLow-Activation Reinforced Concrete Design Methodology-Fundamental Investigation for various Types of Low-Activation Concrete-

low-activation

concrete,

in

order

to

reduceimprovement for cements, which were discussed inradioactivity of nuclear plant decommissioning

this paper.

waste below clearance level The feasibility project
has four main aims:

investigation of major

construction materials and low-activation materials,
determinationofrepresentativepart

establishmentofcalculation

evaluation

and

and

methods, proportioning of low-activation raw

Acknowledgments

materials to make low-activation concrete, andThis work is supported by a grant-in-aid of
Innovative and Viable Nuclear Technology(IVNET) development project of Ministry of
Economy, Trade and Industry, Japan. All of theauthors are grateful to Mr. M. Saito of Tohoku
Electric Power Co., Inc., Dr. T. Tanosaki of
Taiheiyo Cement Co., Mr. R. Yoshino of Denki
Kagaku Kogyo K.K. and Mr. M. Sato of Nippon
Steel Techno research Co. for discussions andcomments.

investigation of methods for low-activation concreteand mortar. In this paper, the results of thefeasibility studies related to concrete and its raw
materials were mainly discussed.
As fundamental issues, criteria of theclearance level for radioactive concrete waste wereaddressed as a background of the comprehensive
development.

Fifty

kinds

of

raw

materials

potentially for the low-activation concrete were
investigated by radiochemical analyses, in order toestimatethequantities

of

trace

elements

dominated to the activation in radioactive concrete[1]waste in certain condition. Limestone aggregates,
quartz including silica sand, and fused alumina[2]ceramics were selected as low-activation aggregates,
and high alumina cements and a white cement
were selected as low-activation cements, whichwere similar results as previous works.

[3]

Based on the above investigations, six types of
low-activation concrete were proposed, which were

[4]

Concrete A (fused alumina ceramics aggregates andhighaluminacement),ConcreteB[5](quartzaggregates including silica sand and high alumina
cement), Concrete C (limestone aggregates and[6]

white cement), Concrete D (limestone aggregates[7]

and low heated cement), Mortal E (fused alumina
ceramics aggregates including silica sand and highalumina cement) and Mortal F (silica sandincluding limestone powder and white cement).
The mix proportion designs were listed withcharacteristics, assignments, and target applicationin the nuclear plants for each proposed concrete.

[8]

These assignments of the proposed concrete also
conducted to the necessary points of further

[9]

－27－

References
Kinno, M. “The Present Activities on
Low-activation.” Japan Concrete Institute, Concrete
Journal, Vol.42, No.6, pp.3-10,2002 (in Japanese).
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Design Method for Reduction of Radioactive Waste
below Clearance Level”, Innovative and Viable
Nuclear Energy Technology (IVNET) Development
Project, Ministry of Economy, Trade and Industry,
Japan, 2006 (in Japanese).
Kinno,M. et al. “Development of Low-activation
Design Method for Reduction of Radioactive Waste
below Clearance Level (1) –General–. ” Atomic
Energy Society of Japan, 2005 (in Japanese)
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York, McGraw-Hill Book Company, Inc, 1958.
MITI, “Intermediate report for the decommissioningof commercial nuclear reactor”, General energy
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short comment
Low-Activation
Concrete is originated for more thantwenty years, and recently we started
national funded project with Tohoku
University and seven companies, aiming
to future replacement of nuclear reactor.

Ken-ichiKimura－28－