JAERI nuclear analyses for IFMIF

T. Umetsu, M. Yamauchi and M. SugimotoPresented by Takeo NISHITANI

Japan Atomic Energy Agency (JAEA)

IAEA Technical Meeting on „Nuclear Data for the International Fusion Materials Irradiation Facility (IFMIF)“,

Forschungszentrum Karlsruhe (FZK), Institut für Reaktorsicherheit, Germany, October 4-6, 2005

Neutronics analysis for the concrete wall

PURPOSE: replacing heavy concrete (baseline design) at the front wall to stainless steel + normal concrete or water cooling layer for surveying optimal combination

METHOD: MCNPX2.4.0 + LA150 + energy- & angular-dependent d-Li(thick) source term

Effectiveness of heavy concrete as a radiation shielding of Test Cell wall

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

1.0E+11

1.0E+12

1.0E+13

0 50 100 150 200 250 300 350 400 450 500

n重量コンクリートSS316 n＋重量コンクリート

n普通コンクリートSS316+普通コンクリートｎ

+ n鉄 重量コンクリート+鉄 普通コンクリートｎ

γ重量コンクリート

SS316+ γ重量コンクリートγ普通コンクリート

+ γ鉄 重量コンクリートSS316+ γ普通コンクリート

+ γ鉄 普通コンクリート

Heavy concrete (n) – baseline

SS316 (20cm) + heavy concrete (n)Normal concrete (n)

SS 316 (20cm) + normal concrete (n)Fe (20cm) + heavy concrete (n)Fe (20cm) + heavy concrete (n)Heavy concrete () – baseline

SS316 (20cm) + heavy concrete ()Normal concrete ()

Fe (20cm) + heavy concrete ()SS316 (20cm) + normal concrete ()Fe (20cm) + normal concrete ()

(cm)

(S

v/h)

Neutron dose for normal concrete ~ 10 (@2m) to 100 (@4m) times higher

1.0E- 03

1.0E- 02

1.0E- 01

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

1.0E+11

1.0E+12

1.0E+13

0 50 100 150 200 250 300 350 400 450 500

n重量コンクリート

5%+ n水冷 重量コンクリート

10%+ n水冷 重量コンクリート

SS316+ n重量コンクリート

γ重量コンクリート

5%+ γ水冷 重量コンクリート

10%+ γ水冷 重量コンクリート

SS316+ γ重量コンクリート

Effect of water cooling channel at surface layer

(cm)

(S

v/h)

No liner (heavy concrete only) (n)

Water(5%) in liner (n)

Water(10%) in liner (n)

No water in liner (n)

Liner 20cm(SS316 10cm + SS316/water 10cm, water content:0, 5,10%)

No liner (heavy concrete only) ()

Water(5%) in liner ()

Water(10%) in liner ()

No water in liner ()

Marginal effect of dose decrease at deep positions

Summary

When replacing heavy concrete at the front wall to normal concrete, neutron doses become ~ 10 (at 2m depth) to 100 (4m depth) times higher.

Introducing steel layer at the surface partly remedies this situation.

Replacing steel layer to water channel results in marginal reduction of estimated doses.

Future directions: Selection of materials combination at surface layer to control the nuclear heating and dose due to residual activities at maintenance.

Estimation of Radioactivity in the IFMIF Liquid Lithium Loop due to the Erosion and Corrosion of

Target Back-wall

Surrounding structural materials are extremely activated. Activated compositions of the target back-wall suffer erosion and corrosion, and move into liquid lithium. They are transported by lithium flow and accumulate in the loop.

Radioactive nuclides in the lithium loop of IFMIF produced by erosion and corrosion effects of the target back wall were estimated by a design code ACT-4 developed in JAERI.

Method of Analysis

The IFMIF neutron spectrum in the back-wall was calculated by McDeLicious code.

The activation build-up in the back wall during the operation and the decay after shutdown were calculated by the ACT-4 code.

Original activation cross sections for ACT4 were combined with cross sections in the IEAF-2001 library from 13.72 MeV to 56 MeV for 7 nuclides.

Preliminary activation calc. and selection of important radioactive nuclides (ACT4 code)

Calculation of neutron spectrum on the IFMIF back wall (McDeLicious)

Compilation of activation cross sections

Activation cross section for fusion facility (ACT4 Library)

Activation cross section for accelerator (IEAF2001)

Revised Activation cross section for IFMIF

Activation calculation of the IFMIF back wall (ACT4 code)

Neutron spectrum on the IFMIF back wall

Radioactivity in the IFMIF back wall

: Flow of Preliminary Process

: Flow of Main Process

Decay curves of radioactivities produced in IFMIF Li target back wall of SS316 Stainless steel

The total amount of radioactivity in the back-wall made of SS 316 was calculated to be 21018 Bq/m3 one month after the shutdown

Rad

ioac

tivity

(B

q/cc

)

108

109

1010

1011

1012

1013

1014

1015

0.01 0.1 1 10 100 1000

,Bqkg_データ、誘導放射能 修正

TotalCR-51MN-54FE-59CO-56CO-57CO-58CO-60NI-57Y-88

Total

Time(day)Time after operation stop (days)

Rad

ioac

tivity

(B

q/cc

)

108

109

1010

1011

1012

1013

1014

1015

0.01 0.1 1 10 100 1000

,Bqkg_データ、誘導放射能 修正

TotalCR-51MN-54FE-59CO-56CO-57CO-58CO-60NI-57Y-88

Total

Time(day)Time after operation stop (days)

Dose rate distributions around the IFMIF Li loop for several cooling times.

0.1

1

10

100

0 1 2 3 4 5

1 day1 week1 month3 month1 year

Dos

e R

ate

(mic

ro S

v/hr

)

Distance from surface (m)

Do

se r

ate

(µ

Sv/

h)

0.1

1

10

100

0 1 2 3 4 5

1 day1 week1 month3 month1 year

Dos

e R

ate

(mic

ro S

v/hr

)

Distance from surface (m)

Do

se r

ate

(µ

Sv/

h)

10 m

0.25 m

Radioactive corrosion product

10 m

0.25 m

Radioactive corrosion product

The 100% amount of the corrosion products was supposed to uniformly accumulate on the inner surface of lithium loop (100% plate-out) of which total inner surface area is 572 m2.

Hands-on limit

Dose rate decay curves around the IFMIF Li loop as a function of cooling time.

0.1

1

10

100

1 10 100 1000

Surface0.3 m1.0 m2.5 m5.0 m

Do

se R

ate

(m

icro

Sv/

hr)

Day after operation stop (day)

Dos

e ra

te (

µS

v/h)

Time after operation stop (days)

According to the results, hands-on maintenance cannot be accepted until the end of one year cooling in the case of 100% plate-out.However, if the deposit of the corrosion products is 10% (10% plate-out), hands-on maintenance becomes possible (the cold trap efficiency is required to be more than 90 %).

Hands-on limit

Summary

■ The total amount of radioactivity in the back-wall made of stainless steel type 316 was calculated to be 21018 Bq/m3 (several tens Ci/cc) one month after the shutdown (Erosion/Corrosion rate : 1 mm/y).

■ The concentration of the activity in lithium is not large compared with the amount of the deuteron-lithium reaction remnant 7

Be.

■ However, the data such as the accumulation on piping and removal efficiencies in cold trap are not sufficient at present.

■ The radiation dose rate around the lithium pipe turned out large owing to the corrosion products produced by one-year IFMIF operation, when 100 % plate-out was supposed. Therefore, the cold trap is required to be highly efficient so that more than 90 % corrosion products can be removed.