شبيه سازي حادثه ي از دست دادن كامل آب تغذيه ي مولد بخار در نيروگاه بوشهر

Simulation of complete loss of steam generator feed water in bushehr power plant

عوامل انساني و نقش آن در بهره برداري از سيستم هاي توليد قدرت در كنار تنظيم نقاط كاركرد مي تواند تاثيرگذارترين فاكتور در خصوص حوادث متداول مانند حادثه ي از دست دادن كامل آب تغذيه براي مولد بخار در مبحث ايمني نيروگاه هاي هسته اي باشد. در اين پژوهش علاوه بر شبيه سازي كامل سيكل نيروگاهي، صحت سنجي داده هاي به دست آمده از حادثه ي از دست دادن كامل آب تغذيه به مولد بخار در مقايسه با داده هاي موجود در FSAR صورت پذيرفته كه نتايج بدست آمده تطبيق خوبي را در شرايط زماني و نقاط عملكردي نشان مي دهد. در ادامه نقش عملكرد اپراتور در طول فرآيند حادثه با انجام عمليات Feed Bleed مورد ارزيابي قرار گرفت. مشاهده گرديد كه مهمترين عملكردي كه به طور موثر بايد در دوره كوتاه از وقوع حادثه انجام شود باز كردن مناسب شيرهاي اطمينان و فعال سازي سيستم خنك كننده ي اضطراري نيروگاه مي باشد به گونه اي كه كاهش معنادار ميزان پارامتر هاي هيدروليكي ميدان جريان اعم از فشار و دما را در بر خواهد داشت. نتايج اين تحقيق مي تواند در تهيه و تنظيم عملكرد مناسب توسط اپراتور در كنترل وضعيت حادثه مورد استفاده قرار گيرد.

Nuclear safety has been one of the main issues to be considered since the basis of the nuclear engineering. Regulatory the power, establishing and upholding core cooling and restraining the radioactive material are three main goals that which should ensure safety system. A total loss of feedwater could occur due to either Main Feed Water pump trip, provided that the failure of both the Auxiliary Feed Water and Emergency Feed Water systems simultaneously takes place and brings the plant to a situation where no water is supplied to the SGs. This accident is categorized as the loss of heat sink accident. If the SGs’ function fails, this blocks the orderly transport and dissipation of energy, the energy produced by the reactor will be stored in the primary system, and will be sensed in the reactor core as a rising inlet temperature. Heat sink losses also lead in general to rising primary system temperatures and therefore to thermal expansion of the reactor coolant. If the primary system pressure control system is not adequate to cope with this coolant expansion, excessive pressures may result and place undue stress on the primary system envelope which jeopardizes primary system integrity. The response of the VVER-1000/V446 nuclear reactor to the TLFW initiating event is analyzed to identify the behavior of important VVER process variables. In order to mitigate the BDBA accident consequences, primary side feed bleed strategy is employed. The use of PRZ safety valves is specially provided for the primary feed bleed procedure by the forced opening of them by the operator. It results in primary coolant pressure decrease and possibility of cooling water supply from the emergency core cooling systems. Thus the main acceptance criterion for the BDBA specified is bringing the reactor plant into the controlled conditions. Moreover, a sensitivity analysis is performed in order to determine the maximum delay time in which operator can fully open SVs to initiate feed bleed strategy in order to prevent core damage. This study shows operation of these safety systems ensures the primary side cool-down and possibility of change-over to the further cool-down stage using the residual heat removal system. During the entire emergency process the temperature of the hottest fuel rod cladding does not exceed the initial value. Thus, the RP is changed over to the controlled state at which the fuel rods are continuously cooled and the radioactive products are kept within the boundaries and limits established and, hence, the acceptance criterion is met.