No abstract

Complementary ventilation is a new and energy-saving mode put forward recently. In order to address safety concerns under fire situation, the fire simulation software FDS has been adopted to build a tunnel model with two tubes. The fire smoke spread rule, temperature field and visibility distribution in two tubes after fire are analysed. Results show that before closing the air valve in connect duct, a small volume of smoke spreads to the adjacent tube. Judging from temperature and visibility, the influence is limited; after closing the air valve, the adjacent tube is no longer affected by the fire tube. According to the personnel safety standards stated in the PIARC2005 Research Report, the complementary ventilation system can meet the requirements of tunnel safety operation in case of fire. Finally, a wet resonance grille dust removal device is proposed to prevent smoke from flowing into the adjacent tube.

To ensure the structure integrity of the RPV, the main challenge is the embrittlement of beltline material. However, the stress of inlet or outlet nozzles of the RPV which are in general reinforced in comparison with the beltline, is more complex especially under the thermal loads. In recently studies, a lot of works have been done to show that the nozzle region may be more challenging under some conditions. In this paper, a fracture assessment for the RPV nozzles subjected to pressure and thermal loading is discussed using the software ABAQUS 6.12 and Zen Crack 7.9-3. It includes: SIF calculation based on 3D finite element method; structural integrity assessment under a typical LOCA transient; and the fatigue crack growth evaluation under cyclic loading situations. The results show that the SIF along the crack front is obviously asymmetric, and only to assess the safety of the deepest point along the crack front in the ASME and RCC-MR codes may be reconsider. If the KIa criteria is applied, under a typical LOCA transient, it is difficult to obtain an effective fracture safety margin for a 1/4 thickness crack, while based on the KIC criteria, the nozzle is shown to be safe in the case study. The shape of the surface elongated crack (which is often easily produced in the nozzle area) tends to be circle under the cyclic pressure loading situation which shows the crack shape assumed in the ASME and RCC-MR codes is reasonable.

A method for forming a simplified model of steam generator which will be used in reactor coolant loop analysis has been shown here, as well as the modal analysis to this simplified SG model. This modal analysis results and the results of the SG provided by NPP designer are compared together in order to prove the design correctness. The comparison shows that the two are basically consistent.

It is required that the fatigue analysis be done for nuclear reactor components consisting of the reactor pressure boundary. Currently, it is certified that the fatigue design curves currently used in the analysis weren’t conservative enough for not considering reactor coolant environment. The article gives some general information related with the regulatory requirements and research work conducted abroad. It introduces coolant environment assisted fatigue experiment based on the domestic austenitic stainless steels and provides the data comparison with the code design fatigue curves. It concludes and recommends the methodology for the nuclear component fatigue design.