RRFM 2009 Transactions - European Nuclear Society

Recently, fuel relocation induced by creep has been observed at the fuel transverse edge region
close to the rail [15]. Because of fuel accumulation at the ‘hot side’ of the transverse cross
sections where the micrographs were obtained, a tensile stress in the thickness direction builds
up and is thought to adversely enhance pore formation. This also contributes to the discrepancy
between observation and estimation.
The high U-loading of the RERTR-9A and -9B restricts the absolute amount of Si available for
diffusion. This is considered the reason why RERTR-9A plates showed thicker ILs and earlier
pore-formation than RERTR-7A plates (see Fig. 3). High U-loading and particle size distribution
have a significant effect that limits the full use of the advantage of Si addition. Therefore,
increasing the as-fabrication Si content must accompany a method to provide Si where it is
needed most. The observation in R6R018 from the RERTR-9B indicates that the addition of
3.5% Si is locally insufficient, suggesting that the addition of at least ~4% as-fabrication Si
content is necessary for U-loading greater than 8 gU/cm 3 and irradiation conditions similar to
RERTR-9B.
5. Conclusions
The side-by-side irradiations of plates with various Si contents showed the efficacy of Si addition
in the Al matrix to reduce IL growth and suppression of the formation of pores in the ILs. Plates
with 2% Si addition have IL thicknesses a factor of three smaller than those without Si. An
analysis shows that 2% Si addition in the matrix is sufficient to sustain the Si effect during
irradiation under typical conditions. However, in a plate with 3.5% Si addition from the RERTR-
9B that had high U-loading (8.5 gU/cm 3 ) and extremely high burnup (119% LEU equiv.), IL grew
thicker than normal and pore started to form because of the insufficient Si content in ILs.
Therefore, for a practical purpose, the addition of at least ~4% as-fabrication Si content appears
to be necessary for U-loading greater than 8 gU/cm 3 and irradiation conditions similar to
RERTR-9B.
6. References
[1] M. Mirandou, S. Arico, L. Gribaudo, S. Balart, RERTR Meeting, 2005.
[2] J.M. Park, H.J. Ryu, S.J. Oh, D.B. Lee, C.K. Kim, Y.S. Kim, G. L. Hofman, RERTR
Meeting, 2006.
[3] G.L. Hofman, Y.S. Kim, J. Rest, M.R. Finlay, RRFM Meeting, 2006.
[4] G.L. Hofman, Y.S. Kim, H.J. Ryu, D. Wachs, M.R. Finlay, RERTR Meeting, 2006.
[5] Y.S. Kim, H.J. Ryu, G.L. Hofman, S.L. Hayes, M.R. Finlay, D. Wachs, G. Chang RERTR
Meeting, 2006.
[6] G.L. Hofman, M.R. Finlay, Y.S. Kim, RERTR Meeting, 2004.
[7] Y.S. Kim, G.L. Hofman, H.J. Ryu, J. Rest, RERTR Meeting, 2005.
[8] J. Garces, G. Bozzolo, G. Hofman, J. Rest, RERTR Meeting, 2005.
[9] J.M. Park, H.J. Ryu, C.K. Kim, Y.S. Kim, RRFM Meeting, 2008.
[10] D.D Keiser, J.F. Jue, RERTR Meeting, 2008.
[11] H.J. Ryu, J.M. Park, C.K. Kim, Y.S. Kim, RERTR Meeting, 2008.
[12] M. Ugajin, M. Akabori, A. Itoh, H. Someya, T. Nakagawa, K. Ohsawa, RERTR Meeting,
1992.
[13] H.J. Ryu, Y.S. Kim, G.L. Hofman, J.M. Park, C.K. Kim, J. Nucl. Mater., 358 (2006) 52.
[14] W.C. Thurber and R.J. Beaver, ORNL-2602, Oak Ridge National Laboratory, 1959.
[15] G.L. Hofman, Y.S. Kim, A.B. Robinson, RRFM Meeting, 2009.
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