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Validation of Neutron Data of Structural Materials

#3544


Validation of Files of Estimated Neutron Data of Structural Materials (Stainless Steel, Iron, Nickel, Chromium and Zirconium) based on Integral Experiments

Tech Area / Field

  • FIR-NOT/Nuclear and Other Technical Data/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

Status
3 Approved without Funding

Registration date
19.06.2006

Leading Institute
FEI (IPPE), Russia, Kaluga reg., Obninsk

Collaborators

  • International Atomic Energy Agency / Nuclear Power Technology Development Section, Austria, Vienna\nCEA Commissariat a l'Energia Atomique, Cadarache, France, Saint-Paul-lez-Durance

Project summary

At present the neutron cross-section uncertainties of structural materials, derived on the bases of micro experiments in the range from tens keV up to several MeV, are still too big. That is why it is not possible to calculate with required accuracy such important for safety characteristics of reactors as for example accumulation of fluence in irremovable constructions far from core.

Earlier in Russia, USA and France some experiments were performed directed on structural neutron data cross-sections validation. By this time only part of those experiments has been analyzed carefully. It enables to specify the influence of structural materials on criticality. As for neutron transfer through thick metal constructions, it has been found that calculational-experimental discrepancies in reaction rates for thick reflectors from structural materials are 30% and more. The reason of such discrepancies are not specified – may be because the joint analysis all integral experiments of neutron transfer through structural materials is still not performed.

The necessity of specification of neutron data for the basic components of steel constructions (shielding, reactor vessel, irremovable constructions) is established international community because of investigations of reactors of fourth generation (Generation-IV). It may be as example the organization of collaboration effort between the Nuclear Data and the Nuclear Power Technology Development Sections of the IAEA for applied library of neutron data creation for analysis of reactors, for transmutation and accelerator driving systems (ADS).

Improvement of accuracy of neutron data for the main structural materials is very important in view of support an adequate accuracy of calculation prediction of nuclear safety parameters in the spent nuclear fuel reprocessing plants (especially in connection with development of new technologies), for estimation of reliability of the radiation shield in the emergency situations, for optimization of the transport container and the spent nuclear fuel (SNF) storage designs.

There is no doubt that development of recommended neutron data that guarantee acceptable fluence prediction accuracy in constructions far from core impossible without validation and, perhaps, without adjustment of using at present data of results of total integral experiments analysis.

The execution of such analysis is the objective of this Project. Results of experiments on spherical transmission trough different structural materials and experiments on neutron transmission in the “good geometry” conditions (broomstick-experiments) performed in different years in Russia and outside will be evaluated and benchmark-models will be developed. Evaluation of the results of several sets of experiments that were performed on the KOBRA (Circular Oscillatory Fast Reactor) and BFS (Big Physical Facility) facilities at IPPE (Obninsk, Russia) will be performed. The critical configurations that were investigated are characterized by extremely high concentration of structural materials in the core (Fe, Ni, Cr, etc.) or presence of thick reflectors from these materials. Also it is planning to perform control experiments on BFS facility on neutron transmission through thick layers of steel constructions and boron shielding. The investigation will be performed using small fission chambers (with layers of 239Pu, 235U, and 238U etc.) and activation detectors.

In the framework of this Project the analysis of modern files of evaluated neutron data for main structural materials (Fe, Cr, Ni, etc.) contained in main native and foreign libraries will be performed. The conclusion of neutron data uncertainties, based only on micro experiments will be done.

Also the analysis of measured sensitivities of functionals to neutron data, their accuracy, and informativity of experiment of the offered Project will be performed. The conclusion of necessity of adjustment of capture for main structural materials will be done.


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