Nuclear Data for Vanadium
Execution of the Complex of Benchmark-Experiments for Testing the Nuclear Data of Vanadium - Main Component of Low-Activation Structural Materials for Advanced Nuclear Energy
Tech Area / Field
- FIR-NOT/Nuclear and Other Technical Data/Fission Reactors
8 Project completed
Senior Project Manager
Tocheny L V
Kurchatov Research Center / Institute of Nuclear Fusion, Russia, Moscow
- FEI (IPPE), Russia, Kaluga reg., Obninsk\nVNIIEF, Russia, N. Novgorod reg., Sarov
- Forschungszentrum Karlsruhe Technik und Umwelt / Institut für Neutronenphysik und Reaktortechnik, Germany, Karlsruhe\nJAERI, Japan, Tokyo\nInternational Atomic Energy Agency, Austria, Vienna
Project summaryThe purpose of the Project is a complex of experimental and calculational researches, oriented on creation of benchmark-experiments set for verification of nuclear data of Vanadium, relevant to formation of neutron and -ray spectra and activation in low-activation structural Vanadium-containing materials of potential fusion reactors and other nuclear-power-generating installations of advanced nuclear energy.
From estimations it follows that more than 90% of fusion reactor induced radioactivity is generated in area of intense 14-MeV neutron flux - in the first wall and blanket. In case of use in these elements of stainless steel the masses of high-activated wastes after reactor shutdown will be comparable with ones generated in fission reactors (~1 Ci/W(th)). If the wastes after initial cooling are disposed of, in the long-term this results in disappearance of valuable reserves of materials and creates a disposal problem. The alternative is recycling of materials executed remotely or by "hand-on" processing. In the latter for conventional materials the waiting time to required doze rate 25 mSv/h might be approximately 1000 years. The perspective of creation of low-activation structural materials for recycling in fusion reactors at present is mainly connected with the use of alloys on Vanadium basis (for example, V-5Cr-5Ti), as far as Vanadium does not give significant concentration of long-lived -emitters.
The use of Vanadium in fusion reactor is accompanied with high demands to accuracy of its nuclear data, relevant to transport of radiation, induced by 14-MeV neutrons in reactor blanket and shield, nuclear heating and activation. The most advanced nuclear data library for fusion reactor application (in the first place, ITER design) at present is FENDL-2 library, containing the best versions of evaluated data, tested on available integral neutronics benchmark-experiments. However, for reliable verification of available and new created evaluated data of Vanadium the data of integral benchmark-experiments are still necessary.
Initially the project proposal assumed within three years carrying out the complete complex of experiments on vanadium spheres ensuring reliable testing the created in the project elementary and isotopic evaluated data files of vanadium in the neutron energy range from zero up to 14 MeV. The program of experiments included a cycle of "outer" measurements (neutrons and gamma-ray leakage spectra) from three vanadium spheres of outer diameter 10, 24 and 34 cm with a 14 MeV neutron source, and also "inner" measurements in the largest sphere with neutron sources of 14 MeV and of fission spectrum. This proposal was approved on 40 %. Therefore working plan was to be reduced up to the first phase and included carrying out only the cycle of the mentioned "outer" measurements at project duration of two years.
This work plan of the project (first phase) has been executed completely: the new experimental spherical sample from vanadium of outer diameter 34 cm is manufactured, the measurements of neutron and gamma-ray leakage spectra, and also of total neutron leakage multiplication, for three experimental spherical samples are carried out with a 14-MeV neutron source, the created new evaluated data files of vanadium are tested on the experiments, held in the project.
As agreed with the project collaborator, within the third year of the project the completion of a set of benchmark-experiments, foreseen by the primal project proposal is proposed, that will allow to test the created evaluated data files of vanadium not only at 14 MeV, as it is done on the first phase of the project, but also in all neutron energy range. The corresponding project activities, agreed with the project collaborator, include the time-of-flight measurements with low registration threshold of neutrons leakage spectra from the large vanadium sphere in IPPE, local measurements of neutron field parameters in this sphere with a 14-MeV neutron source in RRC KI, and the experiments with vanadium spheres on fast spherical critical assemblies from high-enriched metal uranium in VNIIEF. After completion of experiments the testing of evaluated data files of vanadium on the held experiments and final correction of created in the project elementary and isotopic evaluated data files of vanadium will be done in all the neutron energy range up to 14 MeV.
The components of this work are:
1. Measurement of neutron leakage spectrum from Vanadium sphere 34 cm in diameter by the time-of-flight method with low registration threshold.
2. Creating of experimental channel in the large vanadium sphere for local measurements of neutron and gamma-ray parameters (threshold detectors and TLDs) along the sphere radius.
3. Threshold detector- and TLD-measurements along the large sphere radius and on a surface of smaller spheres with a 14-MeV neutron source.
4. Measurements of reactivity (keff) for multiplying assembly containing layers from V, 235U (90%), 235U (36%), 238U and polyethylene or beryllium.
5. Measurements of activation and fission integrals of standard detectors in center of vanadium sphere placed in center of critical assembly for determination of neutron energy distribution.
6. Calculational verification of available versions of evaluated data of Vanadium in the held integral experiments.
7. Final correction of the created evaluated data files of vanadium in the energy range up to 14 MeV.
Expected Results and Their Application:
– experimental data on neutron leakage spectrum with a 14-MeV neutron source from large vanadium sphere in TOF-measurements with low registration threshold (50 keV);
– the experimental data on local neutron and gamma-ray characteristics in large vanadium sphere and on a surface of two small spheres with a 14-MeV neutron source;
– the benchmark-characteristics of critical assembly containing in its center vanadium sphere 24 cm in diameter;
– the neutron energy spectrum in the center of vanadium sphere 24 cm in diameter placed in the center of critical assembly;
– neutronics analysis for setting the experiments and verification of the vanadium evaluated data;
– analysis of available experimental and evaluated data in connection with project activities;
– complete verification of created in the project evaluated data files of vanadium in full neutron energy range up to 14 MeV;
– recommendations on evaluation of vanadium nuclear data.