IEC 62118:2000 pdf download

IEC 62118:2000 pdf download.Nuclear reactor instrumentation – Pressurized water reactor (PWR) of VVER design – Monitoring adequate cooling within the core during shutdown.
3.6
ECCS
emergency core cooling system
3.7
IOCA
loss of coolant accident
3.8
monitoring
means provided to indicate continuously the state or condition of a system, sub-system. equipment or assembly
[IV 393-08-481
3.9
PAMS
post-accident monitoring system
3.10
pressurized water reactor (PWR)
a nuclear steam supply system in which the pressurized coolant is heated by the reactor
core, and process steam is generated in the steam generator by heat transfer from the
coolant
3.11
reactor containment
the structure that encloses the reactor coolant system and parts of specific associated systems, including the pressure containment structures that enclose individual components En some nuclear power plant designs
3.12
RCS
reactor coolant system
3.13
reactor pressure vessel (RPV)
the vessel which contains the reactor core
3.14
RPS
reactor protection system
3.15
reduced inventory condition
an intentional condition that exists during specific maintenance operations whenever water level In the RPV is lower than the top of the RPV hot leg piping nozzle elevation, plus an allowance I or water level measurement uncertainty
3.16
redundancy
provision of alternative (identical or diverse) elements or systems, so that any one can perform the required function regardless of the state of operation or failure of any other
[IAEA 50-SG-D8]
3.17
RHRS
residual heat removal system
3.18
single failure criterion
criterion applied to a system so that it is capable of perlorming its safety task in the presence of any single failure
[1EV 393-08.291
3.19
SLBA
steam line break accident
3.20
subcooled water
water at a temperature lower than the saturation temperature corresponding to the existing pressure
[IEC 61343)
3.21
superheated steam
steam at a temperature higher than the saturation temperature corresponding to the existing pressure
(IEC 61343)
3.22
VVER: water to water power reactor
a PWR design originating from Russian design agencies. Notable features include a
subcooled reactor coolant system and many designs have horizontal steam generators
4 OperatIng condItions
4.1 General
The need for adequate core cooling exists for all plant operating modes and states, including normal power operation, operational transients, abnormal conditions and hot and cold shutdown operations. Annex B contains definitions of the various operating modes and plant operating states applied in VVERs. Adequate core cooling is confirmed by measurements of coolant circulation through the RPV at an appropriate temperature, pressure and flow to remove heat from the core.
This standard covets instrumentation considerations for monitoring core cooling in PWRs of VVER design with configurations similar those shown on figures 1 and 2. These configurations are similar relative to core cooling monitoring requirements except for the following differences:
• FIgure 1 (VVER-440): Loop lsoatlen valves allow loops to be isolated from the reactor for maintenance. Core residual heat (VVER.440 first generation) is removed by natural circulation to the steam generators during shutdown operations after the rundown of the pumps in the reactor coolant system. The steam generators are cooled by the secondary auxiliary RHRS.
• Figure 2 (VVER-1000): Core residual heat is removed by the primary residual heat removal (RHRS) system during cold shutdown operations. RHRS suction lines are connected either to the top of the RPV outlet pipes (hot leg) or the bottom of the RPV inlet pipes (cold leg). Reverse core flow enables the reactor coolant level to be reduced during maintenance operation to the level lower than the top of the RPV inlet (cold leg) piping nozzle elevation.
Subclauses 4.2 through 4.5 describe the normal, abnormal, and accident conditions that depend on the monitoring of adequate core cooling In the reactor.
4.2 Normal power operation
During normal power operation, with reactor power >2 %. core cooling is monitored by the reactor pcotection system (RPS). In the event of an abnormal transient or an accident condition such as a loss of coolant accident (LOCA) or steam line break accident (SLBA), the RPS Initiates a reactor trip, resulting In transition to hot shutdown operation. The RPS therefore meets the normal power operation monitoring requirements these requirements are not addressed in this standard.