The chemical stability of spent fuel will be greatly influenced by the redox potential of the near field. Presence of reductants such as iron is likely to be an important factor to maintain the original integrity of spent fuel. In this work experimental data about the influence of metallic iron (container base material) on SIMFUEL leaching behavior under simulated granite and saline repository conditions is presented. In the presence of iron uranium concentration undergoes a sharp decrease. This is much more noticeable in the experiments performed under initial oxic conditions. The effect of iron on simulated fission products of SIMFUEL is very important for the elements with high redox sensitivity such us molybdenum. On the contrary, strontium remains stable during the entire tests and it seems not be affected by changes in redox potential.

The methodology developed provides guidance on the use of Probabilistic Safety Assessment (PSA) for the risk-informed evaluation of Guides which ensure the compliment of Outage Key Safety Functions (OKSFs) in Nuclear Power Plants. The methodology has been applied to the 3rd and 13th Plant Operational States (POSs) as a Pilot experience. These POSs are within the operating mode 4 (Hot Shutdown) of a 3 loops Westinghouse Pressurized Water Reactor. The addressed Guide requires the operability of just one charge pump as boric acid supply source. PSA gives a Core Damage Frequency increase (∆CDF) of 1.19•10 -6 year -1 for the unavailability of the charge pump in standby, consequently, the maximum exposure time (time for the increase of Core Damage Probability of the configuration to reach 1.0E-06) for this situation is T= 53.6 hours. Given an average time for the POSs of 40 hours, it is concluded that the charge pumps requirement is correct. However, it could be improved with the inclusion of an additional inventory replacement function. This would limit the effect on Risk of the charge pump unavailability. Furthermore, the need for the external electrical sources to be available during mode 4 is ratified. The procedure requires the operability of both supply sources during the POSs. The unavailability of one of supply sources them involves a ∆CDF equal to 1.64•10 -5 year -1 and a maximum exposure time of T= 3.89 hours. This requirement is considered appropriate from the risk-informed regulation point of view.

Two methods are presented which serve to incorporate the fire-related risk into the current practices in nuclear power plants with respect to the assessment of configurations. The development of these methods is restricted to the compulsory use of fire probabilistic safety assessment (PSA) models. The first method is a fire protection systems and key safety functions unavailability matrix which is developed to identify structures, systems, and components significant for fire-related risk. The second method is a fire zones and key safety functions (KSFs) fire risk matrix which is useful to identify fire zones which are candidates for risk management actions. Specific selection and quantification methodologies have been developed to obtain the matrices. The Monte Carlo method has been used to assess the uncertainty of the unavailability matrix. The analysis shows that the uncertainty is sufficiently bounded. The significant fire-related risk is localized in six KSF representative components and one fire protection system which should be included in the maintenance rule. The unavailability of fire protection systems does not significantly affect the risk. The fire risk matrix identifies the fire zones that contribute the most to the fire-related risk. These zones belong to the control building and electric penetrations building.Peer ReviewedPostprint (published version

Abstract-This paper presents a new code for the analy-7 sis of gamma spectra generated by an equipment for con-

Abstract-This paper describes an equipment for continuous measurement and identification of gamma radioactivity in aerosols developed by the Nuclear Engineering Research Group (NERG) at the Technical University of Catalonia (UPC) and Raditel Serveis i Subministraments Tecnològics, Ltd. A spectrometric analysis code has been specially designed for it. Spectrum analysis identifies and determines activity concentration of aerosol emitters captured by a fiberglass paper filter. This new equipment is currently operating in three radioactivity monitoring stations of the Environmental Radiological Surveillance Network of the Generalitat of Catalunya (local Catalan government): two near Ascó and Vandellòs Nuclear Power Plants in the province of Tarragona and one in the city of Barcelona. Two more monitors are expected to be deployed at Roses (province of Girona) and Puigcerdà (province of Barcelona). Measurements and evolution analysis results of emitters identified at these stations were also provided.