Alfredo Luce

Monte Carlo-based assessment of the safety performance of a radioactive waste repository

The present paper illustrates a Monte Carlo simulation-based compartment model for evaluating the expected dose to the critical group from direct intake of contaminated water. An application to a realistic case study is presented to demonstrate the feasibility of the approach.

Monte Carlo Simulation of a Compartment Model of Radionuclide Migration at a Radioactive Waste Repository

Prediction of radionuclides release is a central issue in the performance assessment of nuclear waste repositories. To this aim a model of radionuclides migration through the repository barriers must be set up, accounting for the uncertainties affecting the process. In this context, the present paper presents the application of Monte Carlo simulation to a Markovian modeling framework proposed in the literature; two cases are presented to highlight the value added by the flexibility of the Monte Carlo simulation approach.Copyright

The SPES3 Facility for Testing an Integral Layout SMR: BDBE Simulation Analysis

The SPES3 facility is being built at the SIET laboratories, in the frame of an R&D program on Nuclear Fission, led by ENEA and funded by the Italian Ministry of Economic Development. The facility is based on the IRIS reactor design, an advanced medium size, integral layout, pressurized water reactor, based on the proven technology of PWR with an innovative configuration and safety features suitable to cope with Loss of Coolant Accidents through a dynamic coupling of the primary and containment systems. SPES3 is suitable to test the plant response to postulated Design and Beyond Design Basis Events, providing experimental data for code validation and plant safety analysis. It reproduces the primary, secondary and containment systems of the reactor with 1:100 volume scale, full elevation, prototypical fluid and thermal-hydraulic conditions. A design-calculation feedback process, based on the comparison between IRIS and SPES3 simulations, performed respectively by FER, with GOTHIC and RELAP5 coupled codes, and by SIET, with RELAP5 code, led to reduce the differences in the two plants behaviour, versus a 2-inch equivalent DVI line DEG break, considered the most challenging LOCA for the IRIS plant. Once available the final design of SPES3, further calculations were performed to investigate Beyond Design Basis Events, where the intervention of the Passive Containment Condenser is fundamental for the accident recovery. Sensitivity analyses showed the importance of the PCC actuation time, to limit the containment pressure, to reach an early pressure equalization between the primary and containment systems and to allow passive water transfer from the containment to the RPV, enhanced by the ADS Stage-II opening.Copyright

Preliminary evaluation of a radioactive waste repository safety performance by a Monte Carlo simulation-based reliability model

Abstract Disposal facilities are designed to provide long-term isolation of the wastes from the human environment by means of a system of barriers, both engineered and natural. In this regard, it is required that the containment function of the multi-barrier system be evaluated by a quantitative risk analysis procedure, also called performance assessment. This entails the implementation of a Probabilistic Safety Assessment model for representing the stochastic failure behavior of the repository barriers, estimating the release rates of radionuclides into the groundwater stream and the doses from subsequent ingestion of drinking water. To this aim, a Monte Carlo simulation scheme is provided within a reliability modelling approach for the safety performance analysis of a repository, accounting also for barrier degradation processes. An application to a case study of the literature is presented to validate the approach and demonstrate its simplicity and flexibility.