Fast Reactor Data Research Articles

Enhancements along with application of the Asymptotic Progressing nuclear data Incremental Adjustment (APIA) methodology by individual assimilations of fast reactor data

In view of precise fast reactor analyses, we find that the Asymptotic Progressing Incremental nuclear data Adjustment (APIA) methodology described in previous papers is able providing particularly useful, consistent adjustments by assimilating the integral experimental data in an individual manner. The outcome of dedicated APIA simulations, largely resulting independent of experimental and postulated analytical modeling uncertainties including cross-correlations, supports this conclusion. Clearly, the fully decoupled approach allows identifying and thus best separating effects coming from the different integral experiments considered in the assimilation process; we thus propose a criterion for considering or rejecting additional, individual experiments to enlarge an existing database. We may advise considering further a new experiment under the condition that after completion of the corresponding incremental step the posterior ratios of computed to experimental values for all experiments whose assimilation has occurred in the preceding steps remain unchanged, coinciding with one. Only in this case, the reduced χ2 of a larger number of representative target experiments covering the database may decrease, improving the quality of the data; otherwise, we recommend rejecting the experiment. We illustrate this general result based on representative APIA sequences involving assimilations of central spectral indices measured in the critical configurations Godiva, ZPPR-9, Big Ten, Pu239 Jezebel and SNEAK 7A.

05/00651 The IAEA initiative on fast reactor data retrieval and knowledge preservation

05/00651 The IAEA initiative on fast reactor data retrieval and knowledge preservation

The IAEA initiative on fast reactor data retrieval and knowledge preservation

The paper introduces the IAEA initiative on fast reactor data retrieval and knowledge preservation. Apart from giving the rationale for the initiative and describing it, the paper outlines the road map of the initiative and explains IAEA's role in its implementation. The status of the initiative is summarised, and a concrete work plan for the future activities proposed.

Contribution to irradiation creep arising from gas-driven bubble growth

Although the majority of the irradiation creep data have been developed in fast reactors where the helium generation rates are rather low, many applications of such data involve neutron or charged particle spectra where the helium generation rates are much larger. It also appears that hydrogen can accumulate in austenitic steels when large amounts of cogenerated helium are also present. In such spectra it has been recently predicted that large gas generation rates can lead to an acceleration of the irradiation creep rate under some conditions often found or expected in some fusion designs, near-core components of light water reactors, and in some accelerator-driven spallation devices. In the present paper, this possibility is theoretically explored and shown to be feasible. As a result, an additional degree of conservatism should be included when fast reactor data are applied to spectral environments where large gas generation rates are expected.

A third stage of irradiation creep involving its cessation at high neutron exposures

As swelling approaches 5–10% in AISI 316, the creep rate appears to rapidly decline and eventually vanish. There may be some correlation between this phenomenon and concurrent changes in failure mode that also appear to be related to void swelling. For some fusion-relevant applications, creep correlations derived from fast reactor data may lead to an overprediction of the creep strain.

Application of high fluence fast reactor data to fusion-relevant materials problems

In three recent comparative studies in HFIR and EBR-II where the effect of helium and solid transmutants could be assessed, it was found that in each case there was no significant perturbation of the macroscopic property change under consideration. These findings reinforce the belief that fast reactors can serve as a major tool for fusion materials studies and that the effects of helium and other transmutants can be treated as second-order perturbations to be studied by other methods. A number of new fusion-relevant insights derived from fast reactor studies are presented.

The effects of temperature and dose-rate variations on the creep of austenitic stainless steels in the dounreay fast reactor

Loaded helices of cold-worked, austenitic stainless steels (En58B, E, J, FV548 and type 316) have been irradiated in DFR at damage rates ranging over an order of magnitude at temperatures between 513 and 633 K. Creep rates varied between steels but a common pattern emerged where strain per unit dose appeared to increase with decreasing dose-rate. Comparison with experiments at 773 K on three of the steels reveals creep rate increases by factors ranging from 1.2 to 5. The results are discussed in the context of other fast reactor data and possible explanations of the findings are considered.