RRFM 2009 Transactions - European Nuclear Society

It has been proposed that the efficiency of the “thermal rods” along the fission fragment
tracks is greatly reduced in high conductivity fuels [8]. The thermal-mechanical effect of the
“thermal rods” on the defect structure that controls creep is therefore more pronounced in
UO 2 .
The most important conclusion of the present study is that the fission enhanced creep rate of
U-10Mo provides for a crucial stress relaxation mechanism. Without this, the isotropic
swelling of the fuel would result in large lateral stresses in the thin fuel plates, and could lead
to buckling of the plates when restrained in a fuel element.
Another outcome of the present analysis is a revision of the U-Mo swelling correlation. Many
of the high fission density data were obtained from fuel plate thickness measurements taken
in areas of the plates where fuel relocation by creep had occurred. A new correlation shown
in Fig. 8 was developed by selecting swelling data from areas in the plates that were not
affected by lateral creep.
(ΔV/ V 0 ) f
(%)
100
80
60
40
Open symbols: literature data
RERTR-6 (monolithic)
RERTR-7 (monolithic)
RERTR-9 (monolithic)
2002 model-dispersion plate data [10]
2007 model-high BU monolithic plate data [11]
2009 model-monolithic plate center on metallographs
Recrystalization
begins
20
SFP=3.5%/10 21 f/cm 3
0
0 2 4 6 8
Fission density (10 21 f/cm 3 )
Fig. 8 Comparison of fuel swelling correlations with measured data.
4. References
[1] S.T. Konobeevsky, N.E. Pravdyuk, V.I. Kutaitsev, UN Int’l Conf. Peaceful Use of
Atomic Energy, Geneva, Switzerland, Paper no. 681, 1955.
[2] A.C. Roberts, A.H. Cottrell, Phil. Mag., 1, 711, 1956.
[3] A.S. Zaimovsky, UN Int’l Conf. Peaceful Use of Atomic Energy, 1958.
[4] M. Hesketh, Discussion in paper: M. Englander, C. T. Montpreville, 11th Colloque de
Metallurgie, Creep, June 1967, p.28, Centre D’Etudes Nucleaires de Saclay, 1968.
[5] W. Dienst, J. Nucl. Mater., 65, 1, 1977.
[6] A.A. Solomon, J. Am. Ceram. Soc., 56, 164, 1973.
[7] D.J. Clough, J. Nucl. Mater., 65, 24, 1977.
[8] D. Brucklacher, W. Dienst, Am. Ceram. Soc., Anaheim, California, USA, Nov. 1971.
[9] P. Zeisser, G. Maraniello, P. Combette, J. Nucl. Mater., 65, 48, 1977.
[10] S.L. Hayes, G.L. Hofman, M.K. Meyer, J. Rest, J.L. Snelgrove, RERTR Meeting,
2002.
[11] Y.S. Kim, G.L. Hofman, P. Medvedev, G. Shevlyakov, A.B. Robinson, H.J. Ryu,
RERTR Meeting, 2007.
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