The results of system analysis for the following systems are discussed in this Section:
The Deaerating and Feedwater System is used first of all for normal operation. Secondly, its safety function under various accidental conditions is to provide water with suitable subcooling to the main and auxiliary feed water pumps. After a large or medium break-LOCA it provides water to the main feedwater pumps for the first two minutes, as MFWS is used as the third 50 % train of short term ECCS. After any LOCA it provides water to the emergency feedwater pumps if those are demanded to supplement the ECCS pumps in the long term mode. After any transient it provides water to the auxiliary feed water pumps as preferred providers of long-term makeup.
The main SAR finding are:
The Auxiliary Deaerator Makeup System is a safety system with two main safety functions - to provide makeup water to the deaerator after a reactor trip to supply the auxiliary feedwater pumps and to provide makeup water to the ACS after LOCA to supply ECCS pumps. The main SAR system analysis findings on this system are as following:
The main steam pipelines downstream of the drum separator divide pipelines to two parts: live steam pipelines and hot steam pipelines. Live steam pipelines form closed loops which are the pressure relief devices - MSVs and SDV-A valves. Hot steam pipelines go ultimately to the turbines, but contain the SDV-D valves for normal operation and the main steam isolation valves. The SDV-D bleed steam to heat the cold deaerator makeup water when the turbines are tripped. The main SAR findings are:
Summarizing this Section, it is necessary to notice that the system analysis for the Deaerating and Feedwater System and Auxiliary Deaerator Makeup System show the weaknesses in system capabilities. The limit of operation of the Deaerating and Feedwater System with regard to break sizes in the primary circuit is not assessed. The Auxiliary Deaerator Makeup System can be disabled by single failure or manual interaction. The safety case for the steam lines concludes that there are sufficient relief valves to keep over-pressure after transients to within 15 % of the nominal pressure. System analysis does not cover the main steam isolation valves nor dynamic loads in the case of overfilling of the drum separators.