Impact of the thermal scattering law of H in H₂O on the isothermal temperature reactivity coefficients for UOX and MOX fuel lattices in cold operating conditions

Abstract

Abstract. The contribution of the thermal scattering law of hydrogen in light water to isothermal temperature reactivity coefficients for UOX and MOX lattices was studied in the frame of the MISTRAL critical experiments carried out in the zero power reactor EOLE of CEA Cadarache (France). The interpretation of the core residual reactivity measured between 6°C to 80°C (by step of 5°C) was performed with the Monte-Carlo code TRIPOLI4 ® . The nuclear data from the JEFF-3.1.1 library were used in the calculations. Three different thermal scattering laws of hydrogen in light water were tested in order to evaluate their impact on the MISTRAL calculations. The thermal scattering laws of interest were firstly those recommended in JEFF-3.1.1 and ENDF/B-VII.1 and also that recently produced at the atomic center of Bariloche (CAB, Argentina) with molecular dynamic simulations. The present work indicates that the calculation-to-experimental bias is À0.4 ± 0.3 pcm/°C in the UOX core and À1.0 ± 0.3 pcm/°C in the MOX cores, when the JEFF-3.1.1 library is used. An improvement is observed over the whole temperature range with the CAB model. The calculation-to-experimental bias vanishes for the UOX core (À0.02 pcm/°C) and becomes close to À0.7 pcm/°C for the MOX cores. The magnitude of these bias have to be connected to the typical value of the temperature reactivity coefficient that ranges from À5 pcm/°C at Begining Of Cycle (BOC) up to À50 pcm/°C at End Of Cycle (EOC), in PWR conditions.

Impact of H in H2O thermal scattering data on criticality calculation: uncertainty and adjustment

“…The nominal (not perturbed) parameters of this model can be found in reference [41] and as mentioned, such TSL were included in some of the modern nuclear data libraries. The variations of the model parameters are derived from reference [42], with a number of modification, following the recommendations of the authors. Such variations are as follows:…”

A Comparison of Advanced Boiling Water Reactor Simulations between Serpent/CTF and Polaris/DYN3D: Steady State Operational Characteristics and Burnup Evolution

“…The criticality of the system (k eff ) provides an insight into the behaviour of the neutronic solver and is often used as a method of validation. Within this case two tests were performed using Serpent, one with and one without the thermal scattering libraries linked to the coolant material, these libraries increase the accuracy when bound atoms such as water [43] are used. In the case of the industrial method, the thermal scattering libraries are already applied within SP when the cross-sections are produced.…”

Generation of the1H in H2O neutron thermal scattering law covariance matrix of the CAB model

“…® [29] was used to calculate the reactivity of MISTRAL-1 and -2, as a function of the temperature [30].…”