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[en] The last few years have seen a growing concern with the decreasing number of suitably qualified engineers and university graduates in the field of Nuclear Technology. The gap between supply and demand is now a fact in several countries, and for the reason the international community has prepared several reports on the issue that are summarized here. (Author) 4 refs
[en] Emergency Operating Procedures (EOP) of US PWRs establish that reactor coolant pumps (RCP) should be tripped during a Small-Break Loss of Coolant Accident (SBLOCA) by the operating crew, provided that the subcooling margin has been lost at the core outlet and the High-Pressure Safety Injection (HPSI) is available. On the other hand, it HPSI is unavailable, RCPs must remain in operation. In this work, it is analyzed human actions in SBLOCA sequences with PHSI failure (and therefore without RCP trip), but with a subsequent HPSI recovery (and therefore with a subsequent RCP trip). The analysis was performed with the TRACE code by means of a model with conservative assumptions. The results show that the HPSI recovery and the subsequent RCP trip can lead the plant to damage conditions it recovery occur when the vessel level is lower. Results also show that such damage can be avoided if only 2 out of 3 RCPs are tripped. (Author)
[en] The main result of this paper is the proposal for the addition of new ingredients in the safety analysis methodologies for Generation-IV reactors that integrates the features of probabilistic safety analysis within deterministic. This ensures a higher degree of integration between the classical deterministic and probabilistic methodologies.
[en] – The AP1000® is an advanced Pressurized Water Reactor (PWR) design developed by Westinghouse Electric Company which implements passive safety systems to provide core cooling in case of accident. Within the different accidental sequences Large Break LOCAs are one of the most important sequences in the deterministic and probabilistic AP1000 safety analyses. The UPM group has performed a best-estimate and conservative LBLOCA analysis with TRACE5 patch 4. For this, a best-estimate first cycle core-model with realistic power distributions has been developed using open literature information. Thermomechanical TRACE options have also been activated and detailed fuel geometry and material properties data has been included in order to be able to analyze not only the PCT and ECR, but also other phenomena like ballooning, channel blockage and rod burst. Results show large safety margins with respect to the LOCA acceptance criteria. The analyses have been done for the actual and for the proposal of the 10CFR50.46c rule, the AP1000 passive safety systems have demonstrated a good behavior keeping the core cooled and within the acceptance criteria.
[en] The AP 1000 PRA thermal hydraulic simulations were performed with MAAP code, which allows simulating sequences with low computational efforts. On the other hand, the use of best estimate codes allows verifying PRA results as well as obtaining a greater knowledge of the phenomenology and such sequences. The initiating event with the greatest contribution to core damage is Direct Vessel Injection LIne Break (DVILB). This paper presents a review of DVILB sequences of AP 1000 with TRACE code for verifying sequences previously analyzed by Westinghouse with MAAP code. The sequences which configure the DVILB event tree during short term have been simulated. The results obtained confirm the ones obtained in AP 1000 PRA. (Author)
[en] The objective of the study is the analysis of the appropriateness of the firing of the pumps of the primary and the time available for the beginning of the manual depressurization through steam generators.
[en] Application to the safety function of residual heat removal As part of the project Safety Assessment for Reactor of GEN-IV (SARGEN IV) has been implemented the methodology ISAM from the IAEA to the safety assessment of new sodium reactor designs. Within the ISAM, a new tool to facilitate this assessment is the Objective Provision Tree (OPT) which documents the provisions necessary for each of the levels of defense in depth, as well as for each critical function of security. Due to the design innovations that have sodium reactors, the evaluation of safety and licensing of these reactors requires special considerations. In this work we have analyzed the mechanisms of failure of the safety function concerning the evacuation of waste heat, and have been proposed different provisions for each of the first three levels of defense in depth. The main result of this work is reflected in the elaboration of the OPTs, one for each of the first three levels of defense in depth for the safety of evacuation of residual heat function. These trees represent in a schematic way the provisions necessary to comply with the objectives of each level which are respectively: 1) deviations from normal operation, 2) control of abnormal operation and fault detection and 3) incidental control.
[en] Both the experiment as in the simulation were observed difficulties of inundate the vessel to have the break at the bottom of the same, making key the accident management of the accident by the operator part.
[en] The AP1000 PRA thermal hydraulic simulations were performed with MAAP code, which allows simulating sequences with low computational efforts. On the other hand, the use of best estimate codes allows verifying PRA results as well as obtaining a greater knowledge of the phenomenology of such sequences. The initiating event with the greatest contribution to core damage is Direct Vessel Injection Line Break (DVILB). This paper presents a review of DVILB sequences of AP1000 with TRACE code for verifying sequences previously analyzed by Westinghouse with MAAP code. The sequences which configure the DVILB event tree during short term have been simulated. The results obtained confirm the ones obtained in AP1000 PRA.