Validation of gadolinium burnout using PWR benchmark specification

• We present methodology for validation of gadolinium burnout in PWR.
• We model 17 × 17 PWR fuel assembly using MCB code.
• We demonstrate C/E ratios of measured and calculated concentrations of Gd isotopes.
• The C/E for Gd154, Gd156, Gd157, Gd158 and Gd160 shows good agreement of ±10%.
• The C/E for Gd152 and Gd155 shows poor agreement below ±10%.

The paper presents comparative analysis of measured and calculated concentrations of gadolinium isotopes in spent nuclear fuel from the Japanese Ohi-2 PWR. The irradiation of the 17 × 17 fuel assembly containing pure uranium and gadolinia bearing fuel pins was numerically reconstructed using the Monte Carlo Continuous Energy Burnup Code – MCB. The reference concentrations of gadolinium isotopes were measured in early 1990s at Japan Atomic Energy Research Institute. It seems that the measured concentrations were never used for validation of gadolinium burnout. In our study we fill this gap and assess quality of both: applied numerical methodology and experimental data. Additionally we show time evolutions of infinite neutron multiplication factor Kinf, FIMA burnup, U235 and Gd155–Gd158. Gadolinium-based materials are commonly used in thermal reactors as burnable absorbers due to large neutron absorption cross-section of Gd155 and Gd157.

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