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RRFM 2009 Transactions - European Nuclear Society

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2<br />

Demensional change (%)<br />

1.5<br />

1<br />

0.5<br />

0<br />

0 1 2 3 4 5 6<br />

Fast neutron fluence(×10 24 n/m 2 )<br />

Fig.5. Dimensional change of the graphite under the JRR-4 operation condition as a function of<br />

the fast neutron fluence.<br />

4. Conclusion<br />

We found that a large irradiation growth happened to the graphite reflectors under JRR-4<br />

operation condition, of which temperature was lower than 200 ˚C. The survey on the reflector<br />

elements confirmed that the crack was caused by irradiation growth of the graphite material by<br />

fast neutrons. The irradiation growth ratio was 7.13x10 -25 %m 2 /n in the range of fast neutron<br />

fluence below 2.5x10 24 n/m 2 . We will take this result into account in the future reflector design.<br />

5. References<br />

[1] H. Matsuo: “Effects of High Temperature Neutron Irradiation on Dimensional Changes and<br />

Physical Properties of <strong>Nuclear</strong> Graphites for HTGR”, JAERI-M 87-207 (1987) [in<br />

Japanese].<br />

[2] H. Bridge, B.T. Kelly and P.T. Nettley: “Effect of High-Flux Fast-Neutron Irradiation on the<br />

Physical Properties of Graphite”, Carbon 2, 83-93 (1964).<br />

[3] K. Okumura, T. Kugo, K. Kaneko and K. Tsuchihashi: “SRAC2006: A Comprehensive<br />

Neutronics Calculation Code System”, JAEA-Data/Code 2007-004 (2007).<br />

[4] X-5 Monte Carlo Team: “MCNP-A General Monte Carlo N-Particle Transport Code,<br />

Version 5”, LA-UR-03-1987 (2003).<br />

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