SUB-CHAPTER E.4 DESIGN OF COMPONENTS AND SUB-SYSTEMS

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1 PAGE : 1 / 11 SUB-CHAPTER E.4 DESIGN OF COMPONENTS AND SUB-SYSTEMS 1. REACTOR COOLANT PUMPS 1.1. DESCRIPTION OF REACTOR COOLANT PUMPS The reactor coolant pumps (GMPP) [RCP] are assigned at RCC-M level 1 (see sub-chapter B.6). The detailed list of level 1 GMPP [RCP] assembly components is shown in table E.4.1 TAB 2. The design of EPR reactor coolant pumps is based on the N4 reactor coolant pumps. Each GMPP [RCP] consists of a mixed flow single-stage vertical pump, designed to pump large volumes of reactor coolant at high pressure and temperature. It comprises three major elements: the pump, the shaft seals and the motor. - The hydraulic unit is made up of the casing, an impeller, a diffuser and a suction adapter. The other elements of the pump are the shaft, the main bearing and its auxiliary bearing, the thermal barrier flange and exchanger, the thermal barrier cover fitted with thermal shields, the main flange, the coupling, the spool piece and the motor support. - The shaft line sealing system is made up of three seals arranged in series and a standstill seal system. The first shaft seal is a controlled leakoff seal, which is a film riding face seal; the second and third seals are rubbing face seals. The standstill seal system creates a sealed surface with metal on metal contact ensuring the shaft is leaktight once the pump is shut down and all the leak-off lines are closed. - The motor is a squirrel cage induction motor, protected from water spray, with a solid shaft, a double thrust bearing of the Kingsbury oil-lubricated type, upper and lower oil film radial guide bearings and a flywheel. All parts in the reactor coolant pump can be replaced, with the exception of the casing, which is welded to the reactor coolant loop (see section E.4.3). The reactor coolant pump is supported vertically by three support columns fixed to the three casing support lugs, and horizontally by two snubbers fixed to the upper flange of the motor support (see section E.4.9), a restraint is fitted in front of the casing support foot opposite the cold leg.

2 PAGE : 2 / Pump Reactor coolant passes into the suction nozzle of the casing, is directed towards the impeller by the suction adapter, is pumped across the impeller and exits through the diffuser and the discharge nozzle. All parts of the pump in contact with reactor coolant are manufactured from stainless steel, except for the seals, bearings and special parts. The casing is an integral casting made from stainless steel (austeno-ferritic casting). The impeller is fixed to the pump shaft by a Hirth-type tooth gearing and studs (around the perimeter and in the centre). The diffuser is bolted to the base of the thermal barrier flange. An injection flow at the seals, supplied by the chemical and volume control (RCV) [CVCS] system at a pressure slightly above that of the reactor coolant, enters the pump through a pipe on the thermal barrier flange, and is directed into the cavity located between the thermal barrier and the shaft seals. This flow separates, with one part going back up the shaft through the seals, the other going down the shaft through the thermal barrier heat exchanger and the auxiliary bearing, to ultimately mix with the reactor coolant. The Component Cooling Water System (RRI) [CCWS] supplies cold water to the thermal barrier heat exchanger. Under normal operation, the thermal barrier heat exchanger limits the heat transfer between the hot reactor coolant and the auxiliary bearing and the seals. Moreover, if a loss of injection flow at the seals occurs, the thermal barrier heat exchanger re-cools the reactor coolant to an acceptable level before it comes into contact with the seals. The GMPP [RCP] main radial bearing, located on the diffuser, is a hydrostatic bearing and is supplied by existing pressure in the casing. An auxiliary bearing, which is hydrodynamic, located on the thermal barrier heat exchanger, takes over from the main radial bearing if pressure and temperature transients in the primary circuit impair its operation. The GMPP [RCP] internal components can easily be removed from the casing. The spool piece, located between the pump shaft and the motor shaft, enables maintenance work on the shaft seals system without removing the motor, such work can therefore be carried out quickly (the oil injection method is used to assemble the coupling on the pump shaft). The studs and nuts for the casing and seal no. 1 housing are designed for tightening by hydraulic tensioning or by a heating technique Shaft sealing system The shaft line sealing system generates a pressure drop from the reactor coolant pressure to ambient conditions. Seal n 1 provides the majority of the pressure drop, with a controlled leakoff to the RCV [CVCS]. Seals n 2 and 3 provide the residual pressure drop, with a small leak to the draining and venting circuit (RPE) [NVDS]. In the event of a failure of seal N 1, seal N 2 takes over for a limited period enabling the GMPP [RCP] to be stopped and the reactor to be shut down or the standstill seal system to be activated.

3 PAGE : 3 / 11 Seal N 3 makes a minor contribution to the pressure drop with a negligible leakage; a flushing flow downstream of this seal is provided by the demineralised water system (DWDS). The very minor leak from seal N 3 is purged with the flushing flow to the nuclear vents and drains system (RPE) [NVDS]. The standstill seal system ensures the leak tightness along the shaft when the reactor coolant pump is stopped, in the following cases: - simultaneous loss of water supply from the RCV [CVCS] and the RRI [CCWS] used to cool the shaft line sealing system (for example, during a total loss of the electrical power supply) - cascading failure of all stages in the shaft line sealing system. The design of the sealing system ensures that seals n 2 and 3 and the shutdown sealing mechanism can be installed or removed at the same time (cartridge design) Motor The motor is an air-cooled squirrel cage induction motor, with class F thermo-elastic epoxy insulation. A flywheel and anti-rotation device are fitted in the upper section of the motor. The bearings are of standard design. The radial bearings are pad type bearings, and the thrust bearing comprises a Kingsbury-type double thrust bearing. All bearings are oil lubricated. Water from the RRI [CCWS] feeds the external oil cooler of the upper guide bearing and the integrated oil cooler of the lower guide bearing. A high pressure injection system provides a film of oil in the thrust bearing, before and during startup and shutdown. It also sprays oil into the upper guide bearing. The motor s internal components are air-cooled. Integrated fans at each end of the rotor draw air in through cooling air inlets in the frame of the motor. This air circulates within the motor and in particular to the stator end windings. It is then routed to the outer water/air heat exchangers fed by the RCV [CVCS]. Each motor is fitted with two heat exchangers, installed each side of the motor frame. Air circulates from the motor to the heat exchangers, and then to the pump cell. The heat exchangers are designed to maintain the discharged air at an optimal temperature. Residual heat, discharged by the motor into the containment area, is extracted by the containment continuous ventilation system EVR [CCVS]. The flywheel can be inspected by removing its cover Instrumentation and control Each reactor coolant pump is fitted with the following instrumentation for monitoring the main operational parameters: - 2 temperature sensors at the inlet of shaft seal n 1-2 position sensors for the standstill seal system - 2 temperature sensors for the motor s lower radial bearing pads

4 PAGE : 4 / 11-2 temperature sensors for the motor s upper radial bearing pads - 2 temperature sensors for the lower pads of the motor s axial thrust bearing - 2 temperature sensors for the upper pads of the motor s axial thrust bearing - 2 temperature sensors for each phase of the motor s stator - a pressure gauge and a pressure switch on the motor s double axial thrust bearing oil injection mechanism - 2 shaft displacement sensors at the level of the motor coupling - 2 vibration sensors on the motor lower flange - 2 rotary speed displacement detectors (tachometer) at the level of the motor s coupling - on each oil chamber: 1 low level detector 1 high level detector DESIGN BASES - The main design parameters for reactor coolant pumps are given in E.4.1 TAB 1. - Design of the hydraulic cell is extrapolated from N4 design. It will be able, if necessary, to absorb additional variations of head drop of the RCP [RCS] loop leading the manometric head, at nominal flow rate, to be within the design limits indicated in E.4.1 TAB 1. - Design of the EPR GMPP [RCP] hydraulic cell is defined by an advanced flow computation code and confirmed by many tests on a hydraulic model on the GMPP [RCP] supplier s test loop. During the plant commissioning phase, initial tests of the RCP [RCS] will be carried out in order to verify the hydraulic performance of the GMPP [RCP]. - A tolerance range for the GMPP [RCP] characteristics, combined with uncertainty about the hydraulic pressure drop of the RCP [RCS] loop, results in a defined range of GMPP [RCP] performance encompassing the nominal flow rate; the minimum (thermo-hydraulic) and maximum (mechanical) design flow rates for the RCP [RCS]. - The GMPP [RCP] rotor provides sufficient inertia: to ensure that the house load operation threshold signal is not activated for at least one second in the event of loss of motor power supply. Furthermore, the period between reaching this house load operation signal and the automatic reactor shutdown signal (GMPP [RCP] low speed) must be greater than 0.3 sec

5 PAGE : 5 / 11 to ensure appropriate flow rate, and therefore sufficient Departure from Nucleate Boiling (DNB) before the automatic shutdown of the reactor (triggered by the GMPP [RCP] on low speed) in the event of a GMPP [RCP] coastdown transient condition. Inertia is primarily provided by a flywheel located at the top of the motor shaft. - The casing is designed for a 60-year life. The intended lifespan of the other components is also 60 years, with the exception of certain wear parts which will be replaced periodically (bearings, shaft seals, 0-rings). - The reactor coolant pumps are designed to operate in the following conditions: when the plant is operating with three GMPP [RCPs] in service, and for the start-up of the shutdown GMPP [RCPs]with the other three in service under cold and hot shutdown conditions with one to four reactor coolant pumps in service, and for the start-up of the GMPP [RCP] when the other three are in service; when cooling the reactor between hot shutdown and switching into residual heat removal mode in the event of increase in reactor coolant pressure up to the design RCP [RCS] pressure (corresponding to cold leg pressure of around 160 bar abs). - The coastdown capacity of the GMPP [RCP] is maintained in the event of power loss coinciding with an earthquake. - In the event of APRP [LOCA], a GMPP [RCP] automatic shutdown signal is initiated. The shutdown signal is Low ΔP across the GMPP [RCP] and SI signal. The combination with the SI signal is intended to avoid spurious GMPP [RCP] trip. The ΔP relates to the pressure difference between the GMPP [RCP] inlet (crossover leg pressure) and the GMPP [RCP] outlet (cold leg pressure). - The reactor coolant pumps are designed to withstand without damage: loss of water injection from the RCV [CVCS] at seal No 1, with the pump in continuous operation or at shutdown loss of water from the RRI [CCWS] cooling the thermal barrier heat exchanger with the GMPP [RCP] pump operating or at shutdown simultaneous loss of injection at seal n 1 and of thermal barrier cooling, if one of these two functions is re-established in less than two minutes SEALING SYSTEM SAFETY EVALUATION The standstill seal system is a F1B system and hence the single failure criterion can be considered at the level of its function (see C.2.1 TAB 2). The corresponding functional redundancy is provided by the thermal barrier cooling RRI [CCWS], also classified F1B. The shaft sealing system is comprised of three seals arranged in series and a standstill seal system.

6 PAGE : 6 / 11 The design of seals n 1 and n 2 is identical to that used with good operational experience on the N4 and CP 1300 plants GMPP [RCP] assemblies; the design of seal n 3 is very close to that used on 900 MW plants reactor coolant pumps. Some improvements have however been adopted for the EPR: - pump operation at low pressure when the SIS/RHRS is connected to the RCP [RCS] and is operating in residual heat removal mode - absence of a back-up system for rapid injection at the shaft seals in the event of total loss of electrical power - standstill seal system which can be activated when the pump is shutdown. Consequently, the shaft line sealing system and the standstill seal system are fitted with O rings manufactured with a grade of material qualified for high pressures and temperatures. The seal n 1 faces are made from silicon nitride. Seal n 1 makes the major contribution to the pressure drop with a controlled leakoff (controlled leakoff seal, water film type), directed to the RCV [CVCS]. Under normal operation, this seal is fed from the RCV [CVCS], via the injection line at seal n 1, or, in the event of loss of water injection from the RCV [CVCS], from reactor coolant cooled by the thermal barrier heat exchanger. Seals n 2 and 3 (rubbing face seals) provide the residual pressure drop, with a negligible leakoff directed to to the RPE [NVDS]. Seal n 2 acts as a back up to seal n 1 in the event that the latter fails, and is designed to provide seal function for at least thirty minutes with the pump rotating and for 24 hours once the pump is shut down. A failure in seal n 1 is detected by the flow meter located on the leak-off line. The leak-off line is automatically isolated, the plant power is reduced to an acceptable level allowing the GMPP [RCP] to be shut down; once the GMPP [RCP] is shut down, the plant is shut down or the standstill seal system is activated and all the other leakoff lines are closed. The standstill seal system is located on the upper section of the shaft line sealing system, above seal n 3. Once the pump is shut down, a piston ring, driven by a low pressure nitrogen supply, closes the air gap between the shaft and this ring, and creates a leaktight surface metal on metal contact; ensuring the shaft is leak-tight once the pump is shut down and all the leak off lines closed (these lines are closed off in the following order: seal n 3, seal n 2 and lastly seal n 1). The standstill seal system is designed to be leak-tight in the event of: - simultaneous loss of water supply from the RCV [CVCS] and the RRI [CCWS] used to cool the shaft line sealing system during a Station Black Out (MDTG) [SBO] - cascade failure of all stages in the shaft line sealing system. In the event of Station Black Out MDTG [SBO], the standstill seal system and the leak off line isolating valve for the three shaft seals are automatically closed once the GMPP [RCP] is shut down (see sub-chapter E.1). The standstill seal system is designed to:

7 PAGE : 7 / 11 - reach its closed position, once activated, in the event of pressure and temperature loads resulting from Station Black Out MDTG [SBO] - isolate the significant leak which would result from a cascade failure of the shaft seals - prevent damage to the shaft sealing system in the event of inadvertent closure of the standstill seal when the pump is running - prevent auto-closure in the event of a cascade failure of the shaft seal sealing system - remain leak-tight once operated until a very low reactor coolant pressure is reached, even if nitrogen supply pressure is lost MECHANICAL INTEGRITY IN ACCIDENT CONDITIONS Rotor overspeed The three main transient conditions that may lead to overspeed are: - grid over-frequency - disconnection of the plant from the grid - RCP [RCS] break combined with a loss of power supply. The most disadvantageous APRP [LOCA] for the GMPP [RCPs] is a break in the surge line where it is connected to the RCP [RCS] loop. With a break on such a scale, the overspeed of the GMPP [RCPs] remains below the design value. The GMPP [RCPs] are designed for an overspeed of 25% relative to normal speed. The motor in the GMPP [RCP] (including the flywheel) is tested at this 25% overspeed. The flywheel is made up of two thick plates bolted together. It is lightly shrunk onto the shaft, and three special keys provide transmission to the coupling. Six holes in the flywheel allow periodic in-service ultrasound inspection of the most stressed areas, located in the keyway corners, without removal of the flywheel. All these provisions reduce the risk of a missile within the containment area caused by a flywheel fault. Analysis of the mechanical performance of the casing The RCP [RCS] casing is very similar to the already proven N4 design: - the inner diameter is slightly increased, which results in a slight increase in the wall thickness - the suction and discharge nozzle diameters have been adapted to the diameter of the RCP [RCS] loop, principally resulting in a slight alteration to the dimensions of the discharge cone.

8 PAGE : 8 / 11 - the radial thickness of the upper flange has been increased, so has the diameter of the casing studs. An elastic analysis of the casing has been carried out in accordance with the B3230 RCC-M rules (see subchapter B.6), using the finite element method applied to a three-dimensional model of the casing, in order to verify the design: - under the design conditions (level 0 criterion) - under normal operating conditions (fatigue analysis).

9 SUB-CHAP : E.4 TABLE : 1 PAGE : 9 /11 STANDARD TAB 1 - DESIGN PARAMETERS FOR REACTOR COOLANT PUMPS REACTOR COOLANT PUMP ASSEMBLY Design pressure (bar) 176 Design temperature ( C) 351 PUMP Best estimate flow rate (m 3 /h) 28,330 Thermo-hydraulic flow rate (m 3 /h) 27,195 Mechanical design flow rate (m 3 /h) 30,595 Suction temperature ( C) Mass without water (including motor support) (kg) 50,520 MOTOR Type Air cooled squirrel cage induction motor Power rating (kw) 9,000 Design input power, RCP [RCS] under normal conditions (kw) 8,000 Design input power, RCP [RCS] under cold conditions (kw) 10,850 Voltage (volts) 10,000 Phase 3 Frequency (Hz) 50 Insulation class Class F thermoelastic epoxy insulation Mass (without water or oil) (kg) 60,700 Total inertia (pump and motor) of the rotor (kg.m²) 5210

10 SUB- CHAP : E.4 TABLE : 3 PAGE : 10/ 11 STANDARD TAB 2 LIST OF CLASS 1 COMPONENTS FOR REACTOR COOLANT PUMPS - Casing - Casing nuts and studs - Thermal barrier flange - Main flange - Seal n 1 housing - Seal n 1 housing nuts and studs - Seal n 1 injection line - Seal n 1 injection line boss - Seal n 1 injection line boss and associated flange - Seal n 1 injection line boss and associated flange bolting - Seal n 1 ring support - Seal n 1 housing insert - Seal n 1 housing insert bolting - Seal n 2 and 3 and SS housing bolting - Seal n 1 housing thermowell - Seal n 1 leak off line flange (seal housing side) - Seal n 1 leak off line flange bolting (seal housing side)

11 SUB- CHAP : E.4 FIGURE : 1 PAGE 11/11 STANDARD E.4.1 FIG 1 - REACTOR COOLANT PUMP ASSEMBLIES GENERAL ASSEMBLY Flywheel Thrust and upper guide bearing Oil coolant Motor Rotor Motor Stator Lower guide bearing Shrink fit coupling by oil pressure Shaft seals Thermal barrier Diffuser Impeller DISCHARGE Hydrodynamic bearing SUCTION

FUNDAMENTAL SAFETY OVERVIEW VOLUME 2: DESIGN AND SAFETY CHAPTER E: THE REACTOR COOLANT SYSTEM AND RELATED SYSTEMS

FUNDAMENTAL SAFETY OVERVIEW VOLUME 2: DESIGN AND SAFETY CHAPTER E: THE REACTOR COOLANT SYSTEM AND RELATED SYSTEMS PAGE : 1 / 13 4. PRESSURISER 4.1. DESCRIPTION The pressuriser (PZR) is a pressurised vessel forming part of the reactor coolant pressure boundary (CPP) [RCPB]. It comprises a vertical cylindrical shell,