Validation of zirconium isotopes (n,g) and (n,2n) cross sections in a comprehensive LR-0 reactor operative parameters set

- Determination of 89Zr reaction rate in irradiated ZrO2 sample.
- Experimental spectral average cross section of 90Zr (n,2n) reaction.
- Calculation of reaction rate 90Zr (n,2n) reaction.
- Calculation and measurement of 94Zr(n,g) and 96Zr(n,g) reaction rates.
- Discrepancies between calculation and experiment.
- Hafnium contamination of ZrO2 sample.

Zirconium is an important material used in most of reactor concepts for fuel cladding. Thus the knowledge of its cross section is important for reliable prediction of fuel operation. Also 90Zr(n,2n) reaction, is included in IRDFF files as dosimetry cross section standard. Due to its very high threshold, 12.1 MeV, it is suitable for measurement of high energy neutrons. One of possible interesting applications is also evaluation of prompt fission neutron spectra in 235U and 238U what is under auspices of the International Atomic Energy Agency in CIELO project. The experimental values - obtained with the LR-0 nuclear reactor - of various zirconium cross sections were compared with calculations with the MCNP6 code using IAEA CIELO, ENDF/B-VII.0, JEFF-3.1, JEFF-3.2, JENDL-3.3, JENDL-4, ROSFOND- 2010, and CENDL-3.1 transport libraries combined with the dosimetry cross sections extracted from the IRDFF library.Generally, the best C/E agreement for 90Zr(n,2n) cross section, was found with the IAEA CIELO 235U evaluation that includes an updated prompt fission neutron spectra in the evaluated data file. The cross section of this reaction averaged over LR-0 spectra was determined being  28.9 ± 1.2 µb, corrected to spectral shift, spectral averaged cross section in 235U was determined to be 0.107 ± 0.005 mb. Notable discrepancies were reported in both 94Zr(n,g) and 96Zr(n,g).