RRFM 2009 Transactions - European Nuclear Society

Fig. 4:
Evolution of the
temperature profile of the
hot fluid element at a width
in the channel of 5.0 cm
(compare Fig. 3) at the
surface of the typical fuel plate
of FRM II over the extended
cycle of 60 days (full power
operation at 20 MW).
At BOC the power in the inner
core region is shoved down with
the CR being present above
-7 cm. At EOC the CR is
nearly totally removed and the
power density is rather
symmetrically around the CMP,
although the temperatures
remain higher at the bottom
side, since the coolant water
comes from the top.
SUMMARY / OUTLOOK
This work establishes the evolution with time of the surface temperatures of FRM II fuel plates over a full
operation cycle. One can derive a time averaged maximum temperature that is clearly lower than established
for cycle start. The maximum value in time average is not higher than 85°C even when taking some conservative
values for the coolant conditions. For the conversion of FRM II those studies will be repeated for any
option of future high density fuel element design.
The results presented here can be helpful in case the fuel of final selection exhibits an obvious temperature
dependence at irradiation tests. The latest UMo test irradiations of TUM [2] covered already the
maximum wall temperature range up to about 100°C.
REFERENCES
[1] Proceedings of “International Meetings on Reduced Enrichment for Research and Test Reactors RERTR-
2006”, Cape Town, South Africa, several contributions therein.
[2] “Reduced enrichment program for FRM II, status of 2006”, 11th International Topical Meeting on Research
Reactor Fuel Management, RRFM 2007, Lyon, A. Röhrmoser, W. Petry
[3] “Reduced enrichment program for FRM II, actual status & a principal study of monolithic fuel for FRM II”,
10th International Topical Meeting on Research Reactor Fuel Management, A. Röhrmoser, W. Petry, RRFM
2006, Sofia
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