Author/Authors :
Shahabeddin Kamyab School of Engineering - S hiraz University , Mohammadreza Nematollahi Safety Research Center of Shiraz University , Faramarz Yousefpour Nuclear Science & Technology Research Center, Tehran , Kaveh Karimi Young Researchers and Elite Club, East Tehran Branch - Islamic Azad University, Tehran
كليدواژه :
Grid Configuration , Passive Design , Core Damage Frequency , PSA , Loss of Offsite Power
چكيده لاتين :
Probabilistic Safety Analyses (PSA) of NPPs reveal Loss of Offsite Power (LOOP) as a significant contributor to the Core Damage Frequency (CDF). In this regard, robust and reliable arrangement of offsite power connections, which externally supply essential power from the grid to the required loads in NPPs, are of major concern.
This study intends to survey GDC 17 of 10CFR50 on offsite power sources to the NPPs, using risk analysis approach. The main idea is to investigate the effect of passive design and reliability of internal safety features on the relief of the plant from the GDC. For this, LOOP induced CDF is evaluated and compared for three Advanced Pressurized Water Reactors (APWR, EPR and AP1000), of which two of them employ mainly active safety systems and one benefits from the passive features. Five sensitivity cases are defined on LOOP frequency for various grid configurations.
The results show large increase in the value of CDF for plants with active safety systems, upon decrease in grid reliability. Although all meet NRC’s safety goal of CDF, this study shows that the robustness of NPPs against LOOP are better for AP1000, EPR, and APWR, respectively.
Low LOOP-CDF and its small contribution in total CDF of passive designed PWR (less than 5%), in comparison to that of active ones (more than 86%), a fortiori, support the concept of preserving the redundancy and reliability of connected grid, on one hand, for plants with active safety systems. On the other hand, it relieves passive plants of rigorous requirements of the GDC 17. In other words, devising house-loading capability and reserving connection to grid in order to have a more reliable plant, is as vital and remedial in active power plants, while there is no such sensitivity in passive ones. In addition, if it is an issue of selecting an NPP type and technology to be introduced in the electrical grid network of the country, it is the passive designed feature, such as AP1000, that is more preferable, especially in small electrical networks of low reliability and capacity.
