sub-chapter: c.5 fundamental safety overview …epr-reactor.co.uk/ssmod/liblocal/docs/v3/volume 2 -...

SUB-CHAPTER: C.5

SECTION : C.5.2

PAGE : 1 / 23 UK-EPR

FUNDAMENTAL SAFETY OVERVIEW VOLUME 2: DESIGN AND SAFETY

CHAPTER C: DESIGN BASIS AND GENERAL LAYOUT

2. CONTAINMENT PENETRATIONS There are several types of containment penetrations in the reactor building:

- Equipment hatch,

- Personnel airlocks,

- Emergency hatch

- Site access,

- Fuel transfer tube,

- Mechanical (fluid) penetrations,

- Electrical penetrations.

This section considers the description, design basis and measures taken in order to ensure leaktightness of the penetrations.

Note that all penetrations are horizontal and are located radially in the reactor building, with the exception of the fuel transfer tube.

2.0. SAFETY REQUIREMENTS

The safety requirements for category 1 seismic structures are given in Chapter C.5.0.

The safety requirements for containment and isolation are specified in F.2.1 Containment and F.2.3 Containment Isolation.

2.1. EQUIPMENT ACCESS

2.1.1. Quantity

The reactor building has one equipment access penetration.

2.1.2. General design requirements

The equipment access is designed to maintain its mechanical integrity and fulfil its basic functions (notably, preservation of inner containment leak-tightness) in all normal or accident, conditions, as defined in the ETC-C. The buffer design takes into consideration the experience feedback gained from earlier plants.

The equipment access components are designed with a life expectancy of 60 years, excluding replaceable parts e.g. seals, buffer guiding system bearings, lifting hoists, etc.

All of the control and supply cables, as well as all of the hydraulic and/or pneumatic circuit pipework, are protected against mechanical damage.

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SECTION : C.5.2




2.1.3. Safety classification

The equipment access is safety classified in accordance with Chapter C.2 – Classification of structures, equipment and systems.

2.1.4. Design and production criteria

The design of the equipment access component parts takes into consideration the following loads:

- Normal pressure and temperature conditions inside the containment;

- Accident pressure and temperature conditions inside the containment;

- Containment test conditions (see paragraph 1.13 within this chapter);

- Negative pressure in the space between the containments in relation to the inside of the reactor building;

- Deadweight of the structures and equipment;

- Presence of handling equipment;

- Presence of operational loads;

- Presence of loads caused by the pre-stressing of the inner containment;

- Design basis earthquake;

- Differential movements between containments;

- An external explosion;

- Other external loads (such as an aircraft crash).

The combinations of the above loads are defined in Chapter B of the ETC-C.

The design and construction of the buffer equipment also takes into consideration the following characteristics:

- Positioning tolerance for the shells in the inner and outer containment;

- Differential movements between the inner and outer containments caused by the pre-stressing of the inner containment and those movements caused by the pressure during the containment and earthquake tests;

- Thermal effects;

- Expected ovalization of the shells ;

- Expected warping of the shell and buffer clamps;

- Assembly principles and the power plants operational restrictions.

SUB-CHAPTER: C.5

SECTION : C.5.2




The equipment items and manufacturing processes for welded structures that comprise the equipment access pressurised containment (buffer, shells and clamps) are manufactured in accordance with the ETC-C requirements.

The buffer clamps are RCC-M code level 2 classified (see Chapter B.6).

Accessory components which are not part of the airlock pressure boundary or critical to the buffer closure process are not subject to the ETC-C requirements or RCC-M classified (small equipment).

2.1.5. General description of the equipment access

The equipment access is comprised of the following main components (see C.5.2 FIG 1):

- Two cylindrical shells anchored using collars embedded in the inner and outer containment concrete, connected by a differential movement compensator (leaktight under all operational conditions, including accidents);

- Buffers coupled to the inner shell using clamps and permanently connected to the buffers lifting devices;

- A heavy mobile platform which ensures continuity between the reactor building and the fuel building when the buffer is in the stored position;

- A twin seal system located between the buffer clamp and the shell clamp which enables the collection and control of leaks;

- Pipework, valves and fittings which enable the:

- buffers leak-tightness to be controlled;

- collection of potential leaks in the inter-seal space through the external seal of the buffers twin seal, via the EPP system.

- Handling equipment:

- Clamp line-up device (horizontal travel of buffer);

- Clamp coupling device;

- Buffer lifting devices required for opening, storing and closing the equipment access buffer;

- Locking device held in an elevated position using retaining hooks;

- Specific devices for disconnecting the buffer from its rails after the clamps have been tightened.

2.1.6. Clamp coupling device

The coupling device consists of 40 hydraulic cylinder clamps evenly distributed around the clamps. These clamps are the same type as used on the P4 or N4 series plants. The clamps are semi-automatic, requiring manual intervention to correctly position the clamps before they are tightened.

The clamps are fitted with an integrated tensioning device, which uses a hydraulic cylinder connected to an annular control, supplied by one or two moveable hydraulic units. Clamp tightening is performed simultaneously in order to ensure that the clamps are tightened uniformly.

SUB-CHAPTER: C.5

SECTION : C.5.2




During unit operation, the tightening force is mechanically transferred to an operator installed mechanical deadstop. This enables the tightening force to be maintained after the hydraulic pressure has been released in the cylinder. No residual pressure is present in the hydraulic circuit.

The tightening and un-tightening time enables the buffer to be opened and closed in less than 2 hours, apart from during a leaktightness test.

The design of these clamps is such that:

- in an emergency situation, the compression forces transferred by the shell clamps external lug are enough to enable recovery of the deadweight and the transversal seismic forces through friction;

- the clamps fulfil their tightening function regardless of how the geometry of the clamps changes over time (e.g. appearance of ovalization errors and warping caused by concrete creep in the inner containment). During the design of the buffer clamp geometry changes are calculated at the end of unit life for all operational conditions;

- metal to metal contact is guaranteed under all normal and accident conditions around the whole of the clamps periphery.

2.1.7. Clamp coupling device

The coupling device enables horizontal travel of the buffer between the contact position without applying force to the seal on the buffer clamp in the closure phase (or on the shell clamp if the seal is mounted on the buffer clamp), and the return position in the opening phase before the buffer is lifted.

Travel is powered by two gear driven electrical screw cylinders fixed to the buffer guide carriages.

A mechanical twin locking pin (one per carriage), is installed using an electrical screw cylinder in a hole made in the buffer guide structure. This locking device stops the buffer travel during lifting and lowering.

2.1.8. Buffer guide and lifting device

The buffer vertical travel guide device is comprised of two guide carriages and guide rails. Each guide rail is fixed at the top and bottom to welded structures. These structures are fixed to plates anchored in the inner containment concrete structure.

Two redundant hoists ensure vertical movement of the buffer. Lifting and lowering of the buffer is possible with only one hoist.

An electrical interlock only allows lifting of the buffer when it has arrived at the end of its horizontal travel and the mechanical locking pins are in place, to ensure travel is stopped.

Two hooks integrated in the buffer guide rails, enable it to be safely maintained in the open “stored” position.

Carriage end limit sensors enable the operational sequences to be monitored by the instrumentation and control system, ensuring safe operation of the device. Mechanical safety dead-stops limit the carriage rising travel.

SUB-CHAPTER: C.5

SECTION : C.5.2




2.1.9. Heavy mobile platform

The heavy platform is used to transfer heavy components across the equipment access hatch.

It consists of a hinged platform and a mobile platform:

- The hinged platform is linked to the edge of the fuel building platform, with its rotary movement resulting from the mobile platforms transfer movement;

- The mobile platform is guided in its horizontal direction on a roller track independent of the inner shell.

Transfer movement is ensured using a two way hydraulic cylinder.

2.1.10. Leaktightness provisions

Inner containment penetration leaktightness is ensured by welding the penetration shell to the containment steel liner. The connection is made using a variable thickness gusset welded to both the penetration shell periphery and the steel liner.

The leaktightness device located in the clamp area is comprised of two compressible concentric seals independent of the shell or buffer clamp. In order to enable leaktightness testing, the seals are separated by a space which can be pressurised.

On buffer closure, the twin seal is compressed between the flat surface of the mating clamp and the machined groove of the clamp to which the seal is attached. As a result, the seal is not in direct contact with the reactor building atmosphere. A device mounted on one of the clamps enables the seal to be fully protected from any contaminated deposits in case of a serious accident. This device also buffers the support plane.

The profile, material and location of the seals enable them to resist pressure, temperature and radiation. The seals are environmentally qualified in accordance with the requirements in Chapter C.7 Qualification of equipment under accident conditions. The seals are not inflatable.

The space between the two twin seals is maintained under sub-atmospheric pressure by the Annulus Ventilation System (EDE) [AVS] via a connection to a leak extraction system line (EPP).

The leak extraction system line is protected against random mechanical stresses (collapse or if the line becomes inaccessible).

2.1.11. Manual closure of the buffer

In case of an accident with a loss of electric power, the above buffer handling and clamping devices enable manual closure of the buffer in approximately four hours.

2.1.12. Instrumentation and control of the buffer

Consoles

A local instrumentation and control console is located inside the reactor building in close proximity to the buffer. All of the controls on the consoles are clearly marked, easy to understand, easily accessible, legible, and labelled so that they are durable and resistant to APRP [LOCA].

Each control button has a corresponding visual indicator which can be easily identified on the console schematic.

SUB-CHAPTER: C.5

SECTION : C.5.2




The control consoles are located to prevent the operator from being put at risk from the moving parts of the buffer or heavy mobile platform.

The control buttons dedicated to the buffer and the heavy mobile platform are clearly grouped and arranged on the console.

The buffer opening and closing procedures can only be applied when authorisation is granted from the control room.

Emergency stop

The buffer is fitted with an emergency stop button which immediately blocks all buffer and heavy platform movements if required. This emergency stop cuts the power supply to the hoist and heavy platform drivers and activates their brakes.

Connection to the control room

The control room instrumentation and local control console have the following characteristics:

- If the buffer or the mobile platform is moving, a visual indicator appears on the console and an audible alarm is sounded;

- A safety control button installed on the console in order to deactivate the instrumentation and control console in the containment when the unit is in operation;

- A protected control button (e.g. key interlock system) is installed on the console in order to return the buffer to the closed position;

- Each buffer and heavy mobile platform position and movement can be identified on the consoles schematic;

- The console is fitted with a safety control button for local control inside the containment.

2.1.13. Design conditions and leaktightness verification

The design conditions for pressure, temperature and radiation are defined in Chapter C.7 Qualification of equipment under accident conditions.

The design pressures, temperatures and containment leak-tightness verification test pressures are shown below.

Design Values Pre-operation test Leaktightness verification

Pressure (bar,abs.)

5.5 6.0 6.5

Temperature (0C)

170 20 170

SUB-CHAPTER: C.5

SECTION : C.5.2




2.2. PERSONNEL AIRLOCKS

2.2.1. Position, design and quantity

The reactor building has two personnel airlocks:

The first airlock enables access from the safeguard building. This airlock is joined to a steel shell anchored in the reactor building inner containment (level with a strengthening rib). The airlock penetrates the reactor building outer containment via a penetration fitted with a shell anchored into the concrete by the collars.

This airlock is joined to a steel shell anchored in the reactor building inner containment (level with a strengthening rib). The airlock penetrates the reactor building outer containment via a penetration anchored using collars embedded in the outer containment concrete.

The second airlock enables access to the service platform from the fuel building.

Both personnel airlocks are identical and are fixed to the inner containment in the same manner (level with a strengthening rib).

2.2.2. General design requirements

The airlock’s welded and pressure retaining components are designed to maintain their mechanical integrity and fulfil their basic functions (notably, preservation of inner containment leak-tightness) in all normal or accident, conditions, as defined in the ETC-C.

The airlock components are designed with a life expectancy of 60 years, excluding replaceable parts such as:

- Elastomer seals made with a minimum life expectancy of 10 years;

- Electrical components (outside the airlocks electrical penetrations).

All of the control and supply cables, as well as all of the hydraulic and/or pneumatic circuit pipework, are protected against mechanical damage.

After an accident the airlocks must be able to be opened manually.

2.2.3. Safety classification

The airlocks are safety classified in accordance with Chapter C.2 – Classification of structures, equipment and systems.

2.2.4. Design and production criteria

The following loads are taken into consideration for the design of the airlocks:

- Normal pressure and temperature conditions inside the containment;

- Negative (sub-atmospheric) pressure in the space between the containments i.e. a pressure less than the pressure inside the reactor building;

- Containment leaktightness test conditions;

SUB-CHAPTER: C.5

SECTION : C.5.2




- Accident pressure and temperature conditions inside and outside the containment;

- Deadweight of the structures and equipment;

- Handling of the reference package;

- Presence of operational loads;

- Presence of loads caused by prestressing of the inner containment;

- Design basis earthquake;

- Differential movements between containments;

- External explosion;

- Other external loads (such as an aircraft crash).

The combinations of the above loads are defined in chapter 1 of the ETC-C.

The design and construction of the airlocks also takes into consideration the following characteristics:

- Positioning tolerance required for the shells in the inner and outer containment;

- Differential movements between the inner and outer containments caused by pre-stressing the inner containment and movements caused by the pressure during the containment leaktightness and earthquake tests;

- Thermal effects;

- Ovalization and expected warping of the airlock buffer;

- Assembly principles and the power plants operational restrictions.

The airlock leak-tightness materials (e.g. buffer, doors, shell etc.) are designed and manufactured in accordance with the ETC-C requirements.

For the components which connect and secure the leaktightness materials (e.g. hinges, door support beams, locks) the following are taken into consideration:

- Where applicable the forces, factors of influence and load combinations.

- Admissible restrictions are calculated in accordance with standard DIN 19704.

Accessory components which are not part of the airlock pressure boundary or critical to the buffer closure process are not subject to the ETC-C requirements or RCC-M classified (small equipment).

SUB-CHAPTER: C.5

SECTION : C.5.2




2.2.5. General description

Personnel airlocks are designed to be used for the passage of personnel and small items of equipment, without affecting the containment leaktightness capability. The airlocks are designed and operated in the same manner and comprise the following components:

- A cylindrical shell anchored in the inner containment using collars which are welded to the shells outer surface;

- A cylindrical concentric shell anchored in the outer containment using collars which are welded to the shells outer surface;

- A cylindrical buffer which comprises the body of the airlock itself; this is fitted with a steel clamp which enables it to be welded to the inner shell;

- Differential movements compensator between the airlock buffer and the outer containment;

- Two door units which close the ends of the airlocks, each comprising a:

o Door frame connected to the airlock buffer in a leaktight and resistant manner;

o Motorised revolving door which closes in the direction of pressure if there is an over-pressure in the containment;

o Twin seals for the internal and external doors;

o Leak recovery and control system on the external door only.

- Internal circulation platform with a mobile section which maintains the continuity of the platform on the external door side;

- External crushable circulation platform linked to the reactor building platform and which maintains the continuity of the internal platform of the internal door side airlock;

- Penetrations through the airlocks (electric cable, telecommunication openings etc.) which are fitted with testable twin seal leaktight systems;

- Pipework and valves used to control airlock and penetration leaktightness, collection of external door seal leaks, operation of the airlocks in the compression/decompression vessel and for pressure balancing either side of the doors;

- Automatic or manual door control mechanisms;

- Instrumentation and control system (in addition to the logic operation processing undertaken by the units centralised control system) enabling the doors on the inside and outside of the airlocks to be moved (inner and outer containment side);

- Anti-crushing safety system to prevent injuries to personnel when the doors are moved.

Design features and administrative measures which prohibit unauthorised access to the reactor building containment.

SUB-CHAPTER: C.5

SECTION : C.5.2




Each of the personnel airlocks has a capacity of 48 people.

2.2.6. General operating principles

The installation is designed to enable automatic or manual movement of the airlock doors from the local control panel located close to its associated door.

Airlock movement is performed from the control room at the user’s request. Without control room actuation manual opening is not possible to enter the containment.

Containment entry authorisation is required from the control room for both doors; no control authorisation is required for exit. The duration of the entry authorisation is sufficient for a transfer to be performed.

A signalling system on the local consoles and in the control room advises the user on the condition of the airlock doors, operating mode, different incidents, and errors or false movements which occur during the completion of the operation. The signal system continues to function when the airlock is operated in manual control mode.

The installation also enables:

- entrance into the reactor building without intervention from the control room by using an “emergency entry” push button located on the containment external console when the airlock is shutdown. This push button operates in parallel with the control room authorisation;

- both airlock doors to be open in certain conditions (see the chapter on open doors); when these conditions are not fulfilled, an interlock device prohibits the simultaneous opening of the two airlock doors ;

- the use of airlocks as part of the compression and decompression vessel during the containment pressure testing;

- movement, except as described below, in both manual and automatic mode of any airlock doors, regardless of which console the operator is using. Note, this assumes that six manoeuvring wheels are present;

- passage of the design package with one door closed: the floor level is automatically raised when the doors open;

- the passage of a stretcher when one door is closed;

- the main airlock power supply is isolated on receipt of a containment isolation order: in this instance, the emergency power supply will prohibit the use of the airlock in manual and automatic mode in the direction of entry into the containment.

The reactor building can always be exited regardless of the circumstances.

Door interlocking

The door control mechanism includes an interlock device which ensures that each door cannot be opened when the opposite door and its associated pressure equalising device is closed. This is applicable to both manual and automatic operating modes.

This interlocking device is only over-ridden for the door opening operations described below.

SUB-CHAPTER: C.5

SECTION : C.5.2




Normal operation

When the airlock is in automatic mode, a reduced number of push buttons are required to be activated for the passage of personnel, with the different doors automatically controlled.

In automatic mode the current movement can be stopped at any time by activating the “stop sequence” button.

It is possible to change from automatic mode to manual mode at any time.

Passage from manual mode to automatic mode is only possible at the end of each of the basic sequences.

The passage of personnel is also possible in manual mode in the following instances:

- Operator selection of manual mode on the console. This is only possible from the consoles inside the airlock and reactor building. Control room authorisation is required when using the console on the outside of the containment building;

- In the event of an electrical fault or loss of supply, the installation switches to manual mode and the current movement may be terminated in this manual mode.

The airlock returns to automatic mode three minutes after manual mode selection.

Pressure balancing

Each door is fitted with balance pipework and two motorised valves either side of the door for pressure balancing. The pressure balancing is performed by opening the valves at the beginning of the unlocking phase.

An interlocking system prohibits the simultaneous opening of the balancing valves in each of the airlocks doors, except where the doors are already open.

The motorised pressure balancing valves are backed up electrically by the main diesel generators. They are fitted with end of travel sensors.

Adjustment of these valves must take into consideration the admissible physiological restrictions of the human body, notably when the airlock is being used as part of the compression and decompression vessel during containment pressure testing.

The movement of the airlock doors is connected to a differential pressure control device, to inhibit the sudden opening of the doors in the event of a large residual pressure difference. The residual ∆p threshold value is 10 mbar.

Doors open

This operation is only authorised when the unit is shutdown. The mechanical and electrical interlocks on the airlock doors are overridden from the console outside the reactor building, in accordance with a locally displayed control procedure. This uses a lever protected by a lockable hinged case. This lever is fitted with an electrical contact which ensures interlocking between the two doors.

The doors open operation is only possible when the pressures have been balanced either side of the compartment.

SUB-CHAPTER: C.5

SECTION : C.5.2




When the airlock is in “doors open” condition:

- Automatic control of the doors from the consoles inside the airlock and the containment is overridden, however it is still possible to control the doors in manual mode;

- Closure of any of the airlock doors causes the interlocking to restart. Re-opening this door can subsequently only be performed after the specific doors open operations have been renewed.

Use in the compression and decompression case

Connection pieces enable the installation of removable compressed air intake devices, and airlock air extraction devices, enabling the airlock to be used as a compression/decompression vessel.

When the airlocks are being used as compression-decompression vessels, the protection of personnel accessing the reactor building during the containment pressure test, is ensured by complying with the requirements described in decree 90-277 dated 28 March 1990 for the protection of workers in a hyperbaric environment.

From the entrance on the peripheral buildings side, the airlocks are also fitted with devices able to record reactor building pressure, airlock pressure, and the type of gases in the containment atmosphere.


The inner containment, penetration leaktightness is ensured by welding the shell to the containment liner. The connection is made using a variable thickness reinforcing plate, welded to both the shells periphery and the steel liner plate.

The internal and external personnel airlock doors are supplied with a twin seal fitted with a leaktightness test device.

The space between the twin seals in the external doors of each of the two airlocks is maintained under sub-atmospheric pressure relative to the inner containment by the Annulus Ventilation System (EDE) [AVS] via a connection to a leak extraction system line (EPP). The differential pressure compensator ensures that the annulus between containments is leak tight in relation to the outside of the reactor building.

The doors, glass windows and pressure equalizing systems are sealed using two concentric or parallel compressible seals, which are separated by a space which can be pressurised to enable the leaktightness test to be performed. A line enables this test to be performed and collects possible leaks.

The profile, material and location of the seals enable them to resist pressure, temperature and radiation. The seals are environmentally qualified in accordance with the requirements in Chapter C.7 Qualification of equipment under accident conditions. These seals are not inflatable.

2.2.8. Airlock instrumentation and control

Instrumentation and control consoles

SUB-CHAPTER: C.5

SECTION : C.5.2




Each airlock is fitted with three local instrumentation and control consoles, one outside the containment on the peripheral building side, one inside the airlock and one inside the reactor building.

All of the controls on the consoles are clearly marked, easy to understand, easily accessible, legible, and labelled so that they are durable and resistant to APRP [LOCA].

The control consoles are located to prevent the operator from being put at risk from movement of the airlock doors or retractable platforms.

Each control button has a corresponding visual indicator which can be easily identified on the console schematic.

Connection to the control room

The control console in the control room has the same functions as each of the above mentioned local consoles.

In addition, each instrumentation and control console in the control room has the following characteristics:

- If the two doors in the same airlock are opened simultaneously, an indicator light will appear on the corresponding console and an audible alarm is sounded;

- A safety control button is installed on each console in order to deactivate the instrumentation and control console outside the containment when the unit is in operation;

- a protected control button (e.g. key interlock system) is installed on each console in order to return the two doors of the same airlock to the doors closed position;

- The position of each of the doors can be identified on the corresponding consoles schematic;

- Each console is fitted with a safety control button to operate the corresponding airlock manually.

2.2.9. Design conditions and leaktightness verification

The design conditions for design pressure, temperature and radiation are defined in Chapter C.7 Qualification of equipment under accident conditions.

The design pressures, temperatures and containment leak-tightness verification test pressures are given in Chapter C.5.2 paragraph 1.13.

SUB-CHAPTER: C.5

SECTION : C.5.2




2.3. SITE ACCESS

2.3.1. Description

During the construction phase there is temporary access to the reactor building from the fuel building. The temporary access penetration consists of a 2.9m diameter opening in the inner containment, fitted with a steel shell. It is closed once the construction phase is complete, by a steel buffer welded to the shell. In the outer containment a temporary opening is left in the wall during the construction phase. To ensure the integrity of the outer containment this is concreted over before start-up.

2.3.2. Leaktightness measures

Penetration leaktightness is ensured by welding the shell to the containment liner. The connection is made using a variable thickness reinforcing plate welded to both the shells periphery and the steel liner plate.

In order to anchor the penetration to the internal wall, collars are welded to the shells periphery and embedded in concrete.

Measures are taken to provide a temporary access opening in the external wall, which is sealed once construction work has been completed.

2.3.3. Design basis

The design of the site access meets the same requirements as the design of the containment, for the internal and external walls (see Chapter C.5.1 and Chapter C.5.2).

2.4. FUEL TRANSFER TUBE

2.4.1. Description

The reactor building and the fuel building are connected by a fuel transfer tube which enables the horizontal transfer of fuel elements between the buildings using a fuel transfer device. The description and operation of this device is defined in Chapter I.1.4 fuel handling system (see C.5.2 FIG2).The fuel transfer tube successively travels through the:

- Reactor buildings transfer pool liner;

- Inner containment (fixed point);

- Outer containment;

- Fuel buildings transfer pool shell liner.


The containment’s inner and outer walls, as well as the reactor buildings transfer pool shell, penetrated by the fuel transfer tube, are fitted with a penetration.

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SECTION : C.5.2




For the inner containment, penetration leak-tightness is ensured by welding the penetrations to the containment liner. The connection is made using a variable thickness reinforcing plate welded to both the penetrations periphery and the steel liner plate.

In order to anchor the penetration to the walls, collars are welded to the penetration periphery and embedded in concrete.

The fuel transfer tube is mounted to the inner containment penetration via a welded clamp. A bellows unit connects the fuel transfer tube with the outer containment penetration on the internal wall side.

Two external buffers, which are concentric with the fuel transfer tube, are fitted with bellows units at both ends. These are welded to both the fuel transfer tube and the frames joined to the civil structures. A buffer is connected to the wall of the reactor building transfer pool, a second is connected to the fuel buildings transfer pool. Each buffer is welded to the fuel transfer tube by a clamp to ensure double leak-tightness.

Bellows compensate for differential movements between, the inner containment which is rigidly connected to the fuel transfer tube and the outer containment and transfer pool walls. Differential movement between the reactor building and the fuel building does not exist due to the common foundation raft. Whilst the reactor is in operation, the fuel transfer tube is isolated on the fuel building side by a manual valve operated from the service platform, and on the reactor building side by a bolted twin seal quick opening and closing plug. This is required to ensure containment integrity is maintained, (see Chapter F.2.1 containment).

N.B. once the design has been finalised, the plug may be replaced by an identical valve to that located in the fuel building. The full plug is fitted with a twin seal, the space between the seals is maintained under sub-atmospheric pressure by the Annulus Ventilation System (EDE) [AVS] via a connection to a leak extraction system line (EPP).

2.4.3. Design basis

The fuel transfer tube design meets the same requirements as those for the design of the containment internal and external walls (see Chapter C.5.1).

2.5. MECHANICAL (FLUID) PENETRATIONS

2.5.1. Introduction

There are several types of mechanical (fluid) penetrations which are basically differentiated by the type of fluid transported:

- Pipework penetrations carrying high energy fluid (H.E.) (fluid service pressure > 20 bar or fluid service temperature > 100°C);

- Steam line or water supply penetrations;

- Standard fluid pipework penetrations;

- Sump extraction penetrations RIS [SIS] and EVU [CHRS]);

- Spare penetrations;

SUB-CHAPTER: C.5

SECTION : C.5.2




- Ventilation penetrations.

A break in a high energy, steam line or water supply pipework penetration may cause the degradation of other systems or increase the pressure in the space between containments. The design of these penetrations is therefore different to that of the standard fluid penetrations.

2.5.2. Leaktightness description and provisions

2.5.2.1. STANDARD MECHANICAL (FLUID) PENETRATION

A standard mechanical (fluid) penetration comprises the following elements (see Chapter C.5.2 FIG 3 and note 1):

- A cylindrical ferritic steel penetration sleeve is embedded and anchored in the concrete of both of the reactor building containment walls;

- A connection clamp is welded between the through line(s) and the inner containment wall penetration (fixed point in the pipework);

- A steel expansion bellows is welded between the through line(s) and the outer containment walls penetration (leaktight seal). The role of the bellows is to enable differential movements and/or deformations to occur between the penetration, independently of the internal wall, and the external wall. For this reason a profile is made on the internal surface of the outer containment wall in order to perform the weld.

Inner containment penetration leaktightness is ensured by welding the penetration shell to the containment steel liner. The connection is made using a variable thickness gusset welded to both the penetration shell periphery and the steel liner.

In order to anchor the penetration to the containment wall, collars are welded to the penetration periphery and embedded in concrete.

2.5.2.2. HIGH ENERGY (H.E.) FLUID PENETRATION

A high energy fluid penetration comprises the following elements (see Chapter C.5.2 FIG 4):

- A cylindrical ferritic steel penetration sleeve is embedded and anchored in the concrete of both of the reactor building containment walls. The penetration sleeve increases the width of the space between containments to beyond the external face of the outer containment: it is referred to as a containment tube. Its role is to prevent pressurisation and/or an increase in temperature in the space between containments in case there is a pipework breakage in this area ;

- A connection clamp linking the pipework to the containment tube. This is installed at an offset inside the annulus between containments, in order to prevent the risk of a direct external leak resulting from failure of the weld between the clamp and the containment tube;

_____________________

SUB-CHAPTER: C.5

SECTION : C.5.2




1 Note: some standard penetrations are unique in that they comprise two lines which penetrate the same penetration (their diameter is therefore less than 50 mm).

- A steel expansion bellows is welded between the through line(s) and the outer containment wall penetration (leaktight seal). The role of bellows is to enable the differential movements and/or deformations between the penetration, independently of the internal wall, and the external wall. For this reason a profile is made on the internal surface of the outer containment wall in order to perform the weld.

- Heat insulation where necessary.

2.5.2.3. STEAM LINE OR WATER SUPPLY PENETRATIONS

In addition to the provisions taken for the H.E. fluid penetrations, the steam and water supply lines have a jet shield tube used to protect the inner containment penetration. This also prevents any adverse effects on the concrete in case the weld breaks between the line upstream of the penetration and the penetration connection clamp (limitation of temperature in contact with the concrete) (see Chapter C.5.2 FIG 5).

The welds between the clamp and the two sections of the containment tube must be at a sufficient distance from the clamp to enable them to be inspected by radiography or ultrasonic examination. The design of the jet shield tube must also make provision for this type of inspection.

2.5.2.4. RIS AND EVU PENETRATIONS

The sump extraction penetrations RIS [SIS] and EVU [CHRS]) are located at the reactor building internal structures foundation raft. The lines are used in case of a serious accident, including APRP [LOCA]. The clamp which connects the extract pipework to the foundation raft penetration is located at the end of the clamp, on the sump side. A containment tube is welded to both the foundation raft penetration on the safeguard auxiliaries building side, and the external buffer of the containment shut-off valve (see Chapter C.5.2 FIG 6).

2.5.2.5. VENTILATION PENETRATIONS (EBA)

For the ventilation ducts which penetrate the two containment walls, the internal walls penetration is used as a duct. The ducts are welded directly to the penetration either side of the internal wall (see Chapter C.5.2 FIG 7).

2.5.2.6. SPARE PENETRATIONS

The spare penetrations are comprised as follows:

- A cylindrical steel penetration through the inner containment wall, plugged/capped by a solid welded closure (see note 2);

__________________

2 Note: for a penetration only reserved for periodic use (for example, every ten years), the blind clamp is bolted and not welded.

-

SUB-CHAPTER: C.5

SECTION : C.5.2




- An opening in the outer containment wall temporarily plugged/capped by a cellular concrete type material.

2.5.3. Design basis

The design of the fluid penetrations meets the same requirements as the design of the containment, for the internal and external walls (see Chapter C.5.1).

2.6. ELECTRICAL PENETRATIONS

Please note that there is no direct relationship between the electrical penetrations in the inner and outer containment, as the cables are routed in the space between containments.

2.6.1. Inner containment electrical penetrations

2.6.1.1. GENERAL CONFIGURATION

The electrical penetrations in the inner containment consist of a pressurised housing welded to a steel clamp anchored in concrete.

The electrical cables (see note 3) pass through the housing (using components which ensure leaktightness and/or electrical isolation) and enable the transmission of electrical power or electrical signals.

2.6.1.2. LEAKTIGHTNESS PROVISIONS

Inner containment, penetration leaktightness is ensured by welding the penetration to the containment steel liner. The connection is made using a variable thickness reinforcing plate welded to both the penetration periphery and the steel liner plate.

In order to anchor the penetration to the containment internal wall, collars are welded to the penetrations periphery and embedded in concrete. The housings are fitted with a device which enables continuous monitoring of the condition of leaks through the inner containment electrical penetrations.

The components which ensure the passage of the electrical wires through the box girder are designed so that the condition of their longitudinal leaks are controlled using the same device that is used for the cases.

2.6.2. Outer containment electrical penetrations

The electrical penetrations installed in the outer containment preserve the electrical continuity of cables whilst ensuring leaktightness (in negative pressure or over-pressure conditions in the containment annulus).

__________________

3 Note: In some instances, fibre optics may be integrated next to the electrical wires in penetrations.

SUB-CHAPTER: C.5

SECTION : C.5.2




Depending on the technical solution used, a steel penetration must be installed which supports the items of equipment passing through the penetrations (e.g. multi-cable cable-gland MCT type systems).

2.7. DESIGN AND PRODUCTION CRITERIA

The design of the penetrations is mainly covered by the ETC-C, notably Chapters B.5 (Chapter B.5.2) and 2.7 dealing with steel components whose function is to support in containment leaktightness.

The scope of application of the ETC-C to containment penetrations is summarised below:

- The entire equipment buffer, including vessels, clamps and blind clamp;

- Site access;

- Penetrations in the mechanical and electrical penetrations (the penetrations themselves, up to the clamp/penetration weld or bellows/penetration inclusive are covered by the RCC-M);

- Personnel airlock penetrations (beyond RCC-M);

- Fuel transfer tube penetrations (beyond RCC-M).

Without losing any structural or leaktight integrity, the design of the penetrations must take into consideration all of the imposed loads and deformations, the containment enclosure design conditions and the design conditions of the systems passing through penetrations.

According to Chapter C.4.7 Internal hazards – Fire and ETC-F, the inner containment forms a fire zone limit (between the space between containments and the annulus) and the outer containment forms a fire sector limit (between the space between containments and the outside of the reactor building).

SUB-CHAPTER: C.5

SECTION : C.5.2




FIG 1: EQUIPMENT ACCESS (½ FRONT VIEW, ½ SIDE VIEW)

SUB-CHAPTER: C.5

SECTION : C.5.2




FIG 2: FUEL TRANSFER TUBE PENETRATION

commande de vanne

vanne

supportde vanne

piscine de transfertbâtiment combustibleenceinte externe

enceinte interne

piscine de transfertbâtiment réacteur

tube de transfertØN=500 mm

fourreauØ ext.=940 mm

peaumétalliquesupport

tapepleine

vanne

supportde vanne

FIG 3: STANDARD MECHANICAL (FLUID) PENETRATION

peau métallique

renfort

enceinte interne enceinte externe

flasque

tube de confinement

souffletd'expansion

SUB-CHAPTER: C.5

SECTION : C.5.2




FIG 4: HIGH ENERGY (H.E.) FLUID PENETRATION

peau métalliquesoufflet d'expansion

renfort

enceinte interne enceinte externe

flasque

calorifuge

tube de confinement

(si nécessaire)

FIG 5: STEAM LINE OR WATER SUPPLY PENETRATIONS

containment tubeSteel liner

b a cd

strengthener

Internal containment

clamp

expansion bellows

blocks

Jet shield tube

external containment

SUB-CHAPTER: C.5

SECTION : C.5.2




FIG 6: SUMP EXTRACTION PENETRATIONS (RIS [SIS] AND EVU [CHRS]);

intérieur enceinte

flasque

tube de confinement

extérieur enceinte

peau métallique enceinte

soufflets d'expansion

FIG 7: VENTILATION PENETRATION (EBA)

enceinte interne

soufflet d'expansion

enceinte externe

sub-chapter: c.5 fundamental safety overview …epr-reactor.co.uk/ssmod/liblocal/docs/v3/volume 2 -...

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