Regular Article

Transposition studies with a hybrid experimental database combining ZPR and PWR measurements

¹ EDF Lab Paris-Saclay, 7 Boulevard Gaspard Monge, 91120 Palaiseau, France
² Framatome, DTIPDM-F, 2 rue Pr Jean Bernard, 69007 Lyon, France
³ EDF Lab Chatou, 6 Quai Watier, 78400 Chatou, France
⁴ Université Grenoble Alpes, 621 Avenue Centrale, 38400 Saint-Martin-d’Hères, France

^* e-mail: eric-karson.njayou-tsepeng@edf.fr

Received: 31 March 2025
Received in final form: 18 May 2025
Accepted: 9 July 2025
Published online: 19 August 2025

Abstract

Transposition offers the possibility of extending the conclusions of the validation of a scientific calculation tool to a wider field of use by integrating the experimental information in the calculation process. It generally results in bias adjustment and posterior uncertainty reduction. The aim of this paper is to apply a transposition method on main neutronics parameters to a Gen-III PWR benchmark core, based on a combination of measurements from both critical mock-ups and industrial reactors, thus distinguishing ourselves from most of the studies carried out on the subject. The studies carried out focus mainly on highlighting the main nuclear data requirements for reducing the uncertainties propagated in the EDF and Framatome industrial core code COCAGNE. Two observables are analyzed in this context, one is global: the critical boron concentration, rarely studied in the literature. The second is local: the center/periphery fission rate ratio. It is an indicative measure of the center/periphery power bulge inside a reactor core and has received particular attention. A general overview of the advantages of using transposition for integral quantities requiring significant improvements in nuclear data is also given. As a result, it is shown that the hybrid experimental database enables a wide range of sensitivity profiles to be covered and thus a very large number of nuclear data to be constrained, which ultimately leads to significant reductions in the uncertainties after assimilation (about 70% in the case of the fission rate ratio and 80% in the case of the critical boron concentration). The main nuclear data contributors are identified in each case and some recommendations are given to improve them.