http://hdl.handle.net/11422/93 Wed, 08 Apr 2026 04:50:25 GMT 2026-04-08T04:50:25Z http://hdl.handle.net/11422/27671 Title: An approach for the site selection of an interim storage facility for the reactor compartment of the decommissioned brazilian nuclear submarines Author(s)/Inventor(s): Maia, Yran Leite Advisor: Frutuoso e Melo, Paulo Fernando Ferreira Abstract: The construction of the first Brazilian Nuclear-Powered Submarine (SN-BR) is scheduled to begin in 2022. At the end of its operational life, the submarine will be defueled and decommissioned. During the decommissioning process the reactor compartment (RC) is separated from the rest of the hull and sent to a temporary storage facility. Thus, Brazilian Navy (MB) has to design and build a facility capable of safe storing the RC for about 50 years to allow the decay of the activation radionuclides existing within this compartment. The site selection for the construction of the interim storage facility is one of the first step required to be performed. The purpose of this thesis is to propose a site selection process for the RC interim storage facility in Brazil. This site selection process is based on an Analytic Hierarchy Process methodology that takes into account nuclear and environmental national regulations, naval and shipyard specificities, and logistics constraints. The validation of the proposed site selection process was carried out by a case study that was able to identify six candidate sites that meet the established criteria and to rank them according to their degree of compliance with these criteria. Publisher: Universidade Federal do Rio de Janeiro Type: Tese Sat, 01 Oct 2022 00:00:00 GMT http://hdl.handle.net/11422/27671 2022-10-01T00:00:00Z http://hdl.handle.net/11422/27659 Title: Modelo de cinética inversa para o cálculo da reatividade de reatores a sal fundido Author(s)/Inventor(s): Diniz, Rodrigo Costa Advisor: Gonçalves, Alessandro da Cruz Abstract: Most molten salt reactor designs present a liquid fuel that, mixed with the coolant composed of molten salts, circulates through the reactor. This circulation introduces important phenomena in the study of reactor physics, thus requiring changes in the existing physical models applied in conventional reactors with solid fuel. One of the main influences of the fuel flow in the reactor is in the delayed neutron precursors’ concentration, which partially decay outside the core, not contributing to the fission chain reaction. In this thesis, we investigate the physical models used for this type of reactor, especially the neutron point kinetics, in order to develop an inverse kinetics model, which has practical applications such as core reactivity monitoring and control rod calibration. The developed model has analytical, semi-analytical and numerical solutions. After verifying this model through consistency tests, which demonstrate a satisfactory agreement between the inverse and the point kinetics, two applications in transients are proposed: a linear variation between power levels, and the determination of criticality regions of the reactor during a decrease in flow velocity. The results obtained show that the proposed inverse kinetics model is capable of accurately determine the reactivity both for the execution of power variation, in the first scenario, and to maintain the reactor subcriticality in case of accidents, in the second scenario. Publisher: Universidade Federal do Rio de Janeiro Type: Tese Tue, 01 Mar 2022 00:00:00 GMT http://hdl.handle.net/11422/27659 2022-03-01T00:00:00Z http://hdl.handle.net/11422/27658 Title: Temperatura efetiva do meio para cálculo da função de alargamento Doppler usando distribuição estatística de Kaniadakis Author(s)/Inventor(s): Silva, Marcelo Vilela da Advisor: Martinez, Aquilino Senra Abstract: This work presents a method that establishes a relation of equivalence between the Doppler broadening function ψ(x, ξ) using the Maxwell-Boltzmann distribution and the deformed Doppler broadening function ψκ(x, ξ), according to the generalised Kaniadakis distribution, through the effective temperature of the medium Tef . The generation of nuclear data is a very complex task and requires a huge effort of computer systems. To overcome this hurdle, the main objective of this paper is to present a simple methodology that allows calculation of the deformed Doppler broadening function ψκ(x, ξ), with the Kaniadakis distribution based on the idea of a mapping of the deformed Doppler broadening function, ψ(x, ξ) via a polynomial multidimensional parametrization. Deformed Doppler broadening function ψκ(x, ξ) is approximated by the Doppler broadening function ψ(x, ˜ξ), where ξ is associated to the temperature of medium T and ˜ξ relates to the effective temperature of medium Tef . That is, in calculation systems aimed at determining multigroup cross sections, it will only be necessary to replace T with Tef . Publisher: Universidade Federal do Rio de Janeiro Type: Tese Mon, 01 Aug 2022 00:00:00 GMT http://hdl.handle.net/11422/27658 2022-08-01T00:00:00Z http://hdl.handle.net/11422/27657 Title: Uma proposta de um sistema de indicadores para avaliar a efetividade da gestão de um órgão regulador nuclear Author(s)/Inventor(s): Carvalho, José Antonio Barretto de Advisor: Melo, Paulo Fernando Ferreira Frutuoso e Abstract: While primary responsibility for safety is assigned to the operator of a nuclear facility, the regulatory body must ensure that the level of safety is adequate. It is the regulators' role, through the performance of technical and administrative functions, to develop safety requirements, monitor compliance with them and, if necessary, adopt appropriate measures so that corrective actions are taken. This is done through the implementation of core and support regulatory functions; therefore, it is important to monitor and evaluate them, as their performance can affect nuclear safety. This paper presents a proposal for a set of indicators to monitor and assess the effectiveness of the management of the main regulatory functions (strategic indicators), which will compose a Regulatory Management Effectiveness Index. Supporting functions, which can have direct impact on the main functions, were also considered to be monitored by indicators (cross-cutting indicators), but unlike traditional indicator systems, they were not considered just as another indicator to be aggregated. The dissertation introduces the use of a penalty factor, in which the performance of a crosscutting indicator below an acceptable range is used to penalize the associated strategic indicator. The use of indicators gives to top management a broad and agile view of the organization's performance and trends, essential information for a process of continuous improvement and decision-making. Expert elicitation was used to choose the indicators, weigh the relative importance between them and establish performance criteria. The method can be adapted for use in other regulatory areas. Publisher: Universidade Federal do Rio de Janeiro Type: Tese Thu, 01 Sep 2022 00:00:00 GMT http://hdl.handle.net/11422/27657 2022-09-01T00:00:00Z