[0001 ] The invention relates to lightweight structures for the driver's cabin of
a rail vehicle.
BACKGROUND ART
[0002] The rail industry needs lightweight materials and structures for rail
vehicles in order to meet the challenges it faces in terms of capacity increases and
energy efficiency. Lightweighting also brings reductions in vehicle operating costs.
Furthermore, lighter vehicles cause less damage to track, thereby reducing
infrastructure renewal costs.
[0003] A railway vehicle defining a longitudinal direction and comprising: a
central section and a modular vehicle cabin is disclosed in WO 05/085032. The
vehicle cabin comprising a collapsible front section that undergoes controlled
collapse in case of collision and at least one rigid section located between the front
section and the central section. The front section has a lower resistance to
deformation than the rigid section. At least one dedicated repair interface is
provided for removably fixing the vehicle cabin to the central section. The
dedicated repair interface comprises a thick sheet metal plate extending in a
vertical plane perpendicular to the longitudinal direction over the whole crosssection
of the vehicle body with or without opening for allowing access from the
vehicle cabin to the central section of the vehicle. The vehicle cabin has a selfsupporting
and deformation-resistant modular structure providing a driver space
and a windshield opening. This cabin structure is composed of frame members
made of steel and comprises side pillars each having a lower end and an upper
end, and an undercarriage structure at the lower end of each of the side pillars.
Such rail vehicle cab structures based on welded steel assemblies including an
additional composite cover can weigh more than 1 tonne each. With two cabs per
train-set, this represents a significant weight saving opportunity. Furthermore,
current cab designs tend to be very complex, high part count assemblies with
fragmented material usage. This is because they must meet a wide range of
demands including proof loadings, crashworthiness, missile protection,
aerodynamics and insulation. Assembly costs are high, and there is little in the
way of functional integration.
[0004] A rail vehicle provided with a head module made of a fibre composite
material is known from US 6,431 ,083. The undercarriage of the vehicle supports
the coach body of the vehicle and extends beyond the coach body to support the
head module, which is joined to the undercarriage via a nearly horizontal interface.
The head module consists of at least one head module front wall, two head
module side walls, and one head module roof, which can be produced jointly as
one unit. While the assembly of the head module on the undercarriage is simple
and allows a certain degree of modularity in the design of the vehicle, its
replacement in case of a front collision is much more difficult, since the
undercarriage is not part of the head module and is likely to be damaged during
the crash. Moreover, only partial weight reduction is achieved since the
undercarriage is a conventional cast or welded metal structure. Last but not least,
the unitary structure of the head module is a uniform sandwich structure
composed of a core and laminated walls, which are not locally optimised for
selectively dissipating, i.e. absorbing, the impact energy that occurs during a crash
while preserving a survival space for the driver. A similar design with similar same
limitations is disclosed in EP 0 533 582, which relates to a modular driver's cabin
to be attached on the undercarriage of a rail vehicle. The walls of the cabin
constitute a one-piece assembly including a front wall a bottom, a roof, a rear wall
and two sidewalls. The wall of the cab and the framework of the cab console
constitute a one-piece composite material assembly. The integration of the
console framework stiffens the cab.
[0005] A vehicle front end module comprising both an undercarriage
structure and wholly composed of structural elements made from fibre composite
or fibre composite sandwich material is disclosed in US 201 0/0064931 . By using
different composite/fibre composite sandwich structures for the individual areas of
the vehicle front end module structure, it becomes conceivable to provide both a
substantially deformation-resistant, self-supporting structure composed of first
structural elements made of fibre-reinforced polymer (FRP), which does not
collapse upon collision thereby providing a survival space for the driver, and an
impact absorbing structure located in front of the deformation-resistant structure
and composed of second structural elements designed to at least partly absorb the
impact energy. The highly rigid first individual structural elements building the
deformation-resistant, self-supporting structure include A pillars, side struts, a
railing element to structurally connect the two A pillars and the two side struts, and
an undercarriage structure, which have to be connected together, preferably in a
material fit and more specifically an adhesive bond. The number of individual parts
of the front end assembly is therefore high, hence a high manufacturing cost. Due
to dimensional tolerances and manufacturing limits, the material fit between the
individual parts may be imprecise. Moreover, the interface between individual
structural elements is less than optimal in terms of mechanical behaviour,
reproducibility, additional weight and thermal and acoustic isolation.
SUMMARY OF THE INVENTION
[0006] The foregoing shortcomings of the prior art are addressed by the
present invention. According to one aspect of the invention, there is provided an
integrated self-supporting and deformation-resistant modular driver's cabin
structure for mounting to the front end of a rail vehicle body, the driver's cabin
structure having a front end and a longitudinal direction, the driver's cabin
structure providing a driver space and a windshield opening, the driver's cabin
structure consisting of a composite sandwich structure with a single, common,
continuous outer skin layer, a single, common, continuous inner skin layer and an
internal structure wholly covered with and bonded to the inner and outer skin
layers, the internal structure comprising a plurality of core elements, the composite
sandwich structure comprising a unitary matrix for bonding the internal structure,
the inner skin layer and outer skin layer, parts of the outer skin layer being directly
exposed to the outside, parts of the inner skin layer being directly used as inner
wall for the driver's cabin, the driver's cabin structure comprising at least:
side pillars each having a lower end and an upper end,
comprising a fibre-reinforced sandwich, and
a reactor structure located towards, and integrated with the
lower end of each of the side pillars, the reactor structure being
reinforced such as to transfer static and crash loads to the main
body structure of the rail vehicle and including a central cavity
open towards the front end of the driver's cabin to
accommodate a coupling element for the rail vehicle.
[0007] Thanks to continuous inner and outer skin layers, no boundary
effects are experienced within the structure, which is a true monocoque structure.
[0008] While the matrix material may not be exactly the same at different
locations of the driver's cabin structure, its modifications, if any, are substantially
continuous within the structure. It may in particular be a polymer matrix, in
particular a thermoset or thermoplastic matrix.
[0009] The inner and outer shell layers are preferably made of quasiisotropic
fibre composite material, preferably using glass, carbon, aramid or other
fibres as a reinforcement material embedded in a matrix as described above. The
reinforcing fibres may have a variety of forms including discrete fibres (long or
short, oriented or random) or textiles (woven, braided, stitched, etc.). In particular,
the inner and outer skin layers of the composite sandwich structure may include
fibre-reinforced polymers or FRPs, like carbonfibre-reinforced polymer (CFRP),
glass fibre-reinforced polymer (GFRP) or/and others.
[001 0] The internal structure may consist of a sandwich construction
produced from glass fibre reinforced polymer (GFRP) composite layers and core
elements made of polymer or aluminium foam, balsa or other lightweight wood or
any kind of honeycomb core material, including aluminium honeycomb, aramid
paper-based honeycomb, other paper-based honeycomb, or polymer-based
honeycomb.
[001 1] Advantageously, the sandwich structure is significantly reinforced in
the side pillars and reactor in order to provide sufficient stiffness and strength for
resisting energy absorber collapse forces without permanent deformation or
damage.
[0012] The composite sandwich structure at the side pillars is preferably
provided with several layers of fibres oriented to provide the desired high bending
stiffness. The pillar may include vertical columns of foam sandwiched between
continuous vertical layers of GFRP to produce a multi-layer sandwich construction.
[001 3] The composite sandwich structure of the reactor advantageously
comprises fibres oriented such as to transfer static and crash loads to the main
body structure of the rail vehicle without flexural buckling. It may consist of an
array of bonded foam cores wrapped in glass fibre reinforced polymer to produce
a macro-cellular structure to transfer loads without flexural buckling.
[0014] According to an embodiment, the driver's cabin structure further
comprises reinforcing roof beams each at the upper end of one of the side pillars.
Advantageously, the composite sandwich structure comprises an orientated fibre
lay-up in the roof beams to provide an anisotropic strength with higher strength in
the longitudinal direction of the roof beams. Alternatively, the fibre lay-up may
provide an isotropic strength performance. The roof beams may further provide
local reinforcement points for fixing the cab to the main car body structure. The
roof structure may further comprise a roof panel extending between the roof
beams and connecting the side pillars with one another.
[001 5] According to a preferred embodiment, the driver's cabin structure
provides a side door opening for accessing the driver space and/or a side window
opening.
[0016] According to another aspect of the invention, there is provided a
modular front end structure for a rail vehicle, including:
an integrated self-supporting and deformation-resistant driver's
cabin structure, as described hereinbefore,
a distributed upper energy absorber means consisting of a
crossbeam extending continuously from one of the side pillars
to the other.
[001 7] The modular front end structure will be integrated with an external
shell, provided with an opening for a windshield and a possible door or a possible
side window, as well as with a possible driver's control stand, to form a modular
front end.
[001 8] Preferably, the upper energy absorber means comprises a
collapsible structure extending from one of the side pillars to the other such as to
provide an energy absorption capability.
[001 9] The crossbeam may be composed of a sandwich of one or more
sheet materials and energy absorbing core materials. In particular, it may be
formed as a multi-layer aluminium honeycomb sandwich. The crossbeam may
comprise a metallic core (e.g. aluminium honeycomb material) with metal sheet
facings (e.g. steel or aluminium). The thicknesses of the metallic core and the
metal sheet facings are chosen according to the crash requirements. According to
one preferred embodiment, the crossbeam acts as both a lateral stiffening element
and an energy-absorbing element. The beam may also provide a contribution to
the missile protection of the driver. The crossbeam is separate from the
monocoque structure of the integrated self-supporting driver's cabin structure, to
allow for easy removal and replacement after an impact.
[0020] The modular front end structure may be provided with second energy
absorber elements. The second energy absorber elements are preferably located
substantially at buffer height or at the height of the reactor structure or close to this
height. Preferably, the second energy absorbers are attached to the lower side
pillars directly below the cross beam. In case of frontal impact, the second energy
absorber will collapse and dissipate energy, while the reactor structure of the
modular front end structure will withstand the longitudinal forces and transfer them
to the sole bars of the main body structure of the rail vehicle. The secondary
energy absorbers provide the primary interface with the colliding train.
[0021 ] The modular front end structure further comprises an interface for
joining to the front end of the main body structure of a rail vehicle.
[0022] According to another aspect of the invention, there is provided an
integrated self-supporting and deformation-resistant modular driver's cabin
structure for mounting to the front end of a rail vehicle body, the driver's cabin
structure having a front end and a longitudinal direction, the driver's cabin
structure providing a driver space and a windshield opening, the driver's cabin
structure including two side parts, each side part consisting of a composite
sandwich structure with a single, common, continuous outer skin layer, a single,
common, continuous inner skin layer and an internal structure covered with and
bonded to the inner and outer skin layers, the internal structure comprising a
plurality of core elements, the composite sandwich structure comprising a unitary
matrix for bonding the internal structure, the inner skin layer and outer skin layer,
parts of the outer skin layer being directly exposed to the outside, parts of the
inner skin layer being directly used as inner wall for the driver's cabin, each side
part comprising at least: one side pillar having a lower end and an upper end,
comprising a fibre-reinforced sandwich, and a reactor element extending from the
lower end of each of the side pillar in the longitudinal direction towards the rear
end of the driver's cabin structure, the reactor element being reinforced such as to
transfer static and crash loads to the main body structure of the rail vehicle, the
driver's cabin structure being provided with a central cavity between the reactor
elements of the two side parts, the central cavity being open towards the front end
of the driver's cabin to accommodate a coupling element for the rail vehicle.
[0023] The fibre-reinforced sandwich at the side pillars is preferably
reinforced such as to provide a high bending stiffness. The reactor elements are
preferably reinforced so as to transfer static and crash loads to the main body
structure of the rail vehicle without flexural buckling.
[0024] Each side part forms an integral monocoque structure, the internal
structure of which is preferably wholly covered by the outer and inner skin layers.
As a variant, the end faces of the reactor elements are not covered.
[0025] The internal structure in the side pillar and in the reactor element
comprises a plurality of core elements. Each core element is covered by a
composite material. As a variant, the end faces of the core elements are not
covered.
[0026] Each side part may further include a roof beam extending in the
longitudinal direction from the upper end of the side pillar towards the rear end of
the driver's cabin structure. In such a case, the single, common, continuous outer
skin layer and single, common, continuous inner skin layer and an internal
structure wholly covered with and bonded to the inner and outer skin layers.
[0027] The two side parts can be manufactured simultaneously in one
mould also including a roof panel, which extends from one roof beam to the other
to form a unitary structure. They can also, as a variant, be manufactured
separately and assembled to one another at a later stage.
[0028] According to a further aspect of the invention, there is provided a
process for manufacturing the integrated self-supporting and deformation-resistant
driver's cabin structure for a modular cabin of a rail vehicle or the modular front
end structure for a rail vehicle as described hereinbefore, wherein a unitary matrix
material is introduced to skin layer reinforcement fibres and to core materials
before or after the reinforcement fibres are placed into a mould cavity or onto a
mould surface of a mould and the matrix material subsequently experiences a
polymerisation or curing event to constitute the sandwich composite structure.
[0029] According to one embodiment, the fibres of the inner skin layer
and/or outer skin layer and the core materials are placed in the mould cavity or on
the mould surface before the unitary matrix material is introduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Other advantages and features of the invention will become more
clearly apparent from the following description of specific embodiments of the
invention given as non-restrictive example only and represented in the
accompanying drawings in which:
- figure 1 is a front view of a modular front-end structure including a driver's
cabin structure for a rail vehicle according to one embodiment of the invention;
- figure 2 is a longitudinal section through plane ll-ll of figure 1;
- figure 3 is a cross-section through plane Ill-Ill of figure 2 ;
- figure 4 a horizontal section through plane IV-IV of figure 2 ;
- figure 5 is a detail from figure 4 .
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0031 ] Referring to figure 1 and 2 , a modular front end structure 10 for a rail
vehicle, consists of three modules, namely a lower strength primary crush zone 12
or "nose" located at the front end of the structure, a higher strength secondary
crush zone 14, which is located behind the primary crush zone and contains the
majority of the cab's energy absorption capability, and a reaction zone 16 which is
able to resist the collapse loads of the two frontal crush zones 12, 14, whilst
protecting the driver and ensuring that any forces are properly transferred to the
main part of the coach body, which represents a hard zone providing a survival
cell for the passengers.
[0032] The nose 12 is designed to be easily detached and re-attached. This
is to facilitate repair or replacement following minor collisions. The nose 12 is
designed to contribute to the overall energy absorption capability of the cab.
Energy absorbing materials and structures are suitably deployed within the
available volumetric envelope of the nose.
[0033] The higher strength secondary crush zone 14 includes lower, bufferlevel
energy absorber means 18 and upper energy absorber means 20. The lower,
buffer-level energy absorber means 18 are two interchangeable discrete energy
absorbers 18A, 18B e.g. with an aluminium honeycomb sandwich construction
which provides excellent performance levels in terms of constant and continuous
absorbed energy during a crash or a more conventional welded-steel type.
[0034] The upper energy absorber means 20 consists of a distributed
energy absorbing zone, which runs across the width of the cab as illustrated in
Figure 4 . The main function of the upper energy absorber means 20 is to resist the
collision with a deformable obstacle. As the deformable obstacle provides a
distributed load input to the cab, the use of a distributed energy absorbing zone,
i.e. a zone that extends continuously from side to side of the front-end, is
preferable to the use of discrete energy absorbing elements. The upper energy
absorber means 20 can be formed as a multi-layer aluminium honeycomb
sandwich. In addition to providing an energy absorption capability, the resulting
sandwich crossbeam 20 also provides additional lateral rigidity to the cab, as well
as enhanced missile protection coverage for the driver.
[0035] The reaction zone 16 forms an integrated self-supporting and
deformation-resistant driver's cabin structure 22.
[0036] The driver's cabin structure 22 is composed of a sandwich composite
structure with a single, common, continuous outer skin layer 24, a single, common,
continuous inner skin layer 26 and an internal structure 28 wholly covered with and
bonded to the inner and outer skin layers 24, 26.
[0037] The driver's cabin structure 22 comprises side pillars 30A, 30B, each
having a lower end and an upper end, a reactor structure 32 at the lower end of
each of the side pillars, and can also be integral with a roof structure 34 including
roof beams 34A, 34B each at the upper end of one of the side pillars 30A, 30B and
a roof panel extending from one roof beam to the other.
[0038] As severe collisions occur less frequently than minor collisions, there
is no disassembly requirement for the interface between the secondary crush zone
14 and the reaction zone 16. Hence, while the upper energy absorbing means was
described in connection with the secondary crush zone rather than with the
reaction zone, due to its main function during a collision, it may structurally be
integrally formed with the driver's cabin structure, and share continuous inner and
outer layers with the side pillars and reactor structure. As the upper energy
absorbing means extends from one of the side pillars to the other, it provides a
crossbeam, which as stated before also provides additional lateral rigidity to the
cab.
[0039] The internal structure of the driver's cabin structure 22 consists of a
sandwich construction produced from glass fibre reinforced polymer (GFRP)
composite layers and polymer foam. The sandwich is significantly reinforced in the
pillar region 30A, 30B (where the upper energy absorber means attaches) and the
reactor structure 32 (where the buffer level energy absorbers attach) in order to
provide the necessary stiffness and strength for resisting the energy absorber
collapse forces without permanent deformation or damage. The reactor structure
32 in the lower buffer regions consists of an array of bonded square-section foam
cores wrapped in glass fibre reinforced polymer (GFRP) to produce a macrocellular
structure to transfer loads without flexural buckling. The pillar regions 30A,
30B, above the reactor structure 32, also consists of an assembly of GFRP and
foam cores. Each vertical column of foam in the pillars 30A, 30B is sandwiched
between continuous vertical layers of GFRP to produce a multi-layer sandwich
construction to provide a high bending stiffness to the side pillars 30A, 30B.
[0040] The roof beams 34A, 34B comprise a composite sandwich
construction made of optimised orientated layered fibres, providing an anisotropic
strength with higher strength in a longitudinal direction of the roof beams, or made
of composite material with isotropic strength performance.
[0041 ] A windshield opening 36 is provided between the side pillars 30A,
30B, roof structure 34 and crossbeam 20. A side door or window opening 38 is
provided on each side of the driver's cabin structure 22, between the reactor
structure 32, the corresponding side pillar 30A, 30B and the roof structure 34.
[0042] Some parts of the outer skin layer 26 may be directly exposed to the
outside, i.e. without interposition of a shell as shown in Figure 5 , while other parts
of the outer skin may be protected from the outside by an external shell, as e.g. in
the nose region.
[0043] Similarly, parts of the inner skin layer 24 may be directly used as
inner wall for the driver's cabin.
[0044] The driver's cabin structure as a whole provides a driver space, open
towards the rear of the structure, i.e. towards the main part of the coach body to
which the front-end structure is to be assembled.
[0045] The front-end structure is also provided with an interface for joining it
to a front end of the main body structure of a rail vehicle.
[0046] During the manufacturing process of the driver's cab structure, a
unitary matrix material is introduced to reinforcement fibres and core materials
before or after the reinforcement fibres and core materials are placed into a mould
cavity or onto a mould surface of a mould and the matrix material subsequently
experiences curing to constitute the sandwich composite structure with a unitary
matrix to which the inner skin layer and outer skin layer are also bonded.
[0047] While the invention has been described in connection with one
example, variations are possible.
[0048] While a crossbeam is necessary for rigidifying the structure of the
driver's cab, this crossbeam is not necessarily unitary with the first energy
absorbing means. It is therefore possible to include e.g. a crossbeam integral with
the structure of the driver's cabin structure, and separate energy absorbing
means, e.g. discrete energy absorber attached to the crossbeam or a continuous
energy absorbing element extending all the width of the driver's cabin.
[0049] The reactor structure of the integrated self-supporting and
deformation-resistant modular driver's cabin structure may include a central cavity
open towards the front end of the driver's cabin, to accommodate a coupling
element for the rail vehicle. Preferably, the reactor structure includes at least two
reactor elements extending in a longitudinal direction of the driver's cabin on each
side of the central cavity. While the lateral, upper and lower faces of the reactor
elements are covered with the skin layer, the end faces may not be covered.
These two reactor elements are connected with one another through the side
pillars and the roof structure.
The internal structure in the side pillars and in the reactor elements comprises a
plurality of core elements. Each core element is covered by a composite material.
As a variant, the end faces of the core elements are not covered.
[0050] Inner and outer skin layers may be united to form a shell completely
encapsulating the internal structure.
CLAIMS
1. An integrated self-supporting and deformation-resistant modular driver's
cabin structure (10) for mounting to the front end of a rail vehicle body, the driver's
cabin structure having a front end and a longitudinal direction, the driver's cabin
structure providing a driver space and a windshield opening, the driver's cabin
structure consisting of a composite sandwich structure with a single, common,
continuous outer skin layer (24), a single, common, continuous inner skin layer
(26) and an internal structure (28) wholly covered with and bonded to the inner
and outer skin layers (24, 26), the internal structure (28) comprising a plurality of
core elements, the composite sandwich structure comprising a unitary matrix for
bonding the internal structure, the inner skin layer and outer skin layer, parts of the
outer skin layer (24) being directly exposed to the outside, parts of the inner skin
layer (26) being directly used as inner wall for the driver's cabin, the driver's cabin
structure comprising at least:
side pillars (30A, 30B) each having a lower end and an upper end,
comprising a fibre-reinforced sandwich, and
a reactor structure (32) located towards, and integrated with, the
lower end of each of the side pillars (30A, 30B), the reactor
structure (32) being reinforced such as to transfer static and crash
loads to the main body structure of the rail vehicle and including a
central cavity open towards the front end of the driver's cabin to
accommodate a coupling element for the rail vehicle.
2 . The integrated self-supporting and deformation-resistant driver's cabin
structure of claim 1, wherein the internal structure consists of a sandwich
construction produced from glass fibre-reinforced polymer (GFRP) composite
layers and core elements made of polymer or aluminium foam, balsa or other
lightweight wood or any kind of honeycomb core material, including aluminium
honeycomb, aramid paper-based honeycomb, other paper-based honeycomb, or
polymer-based honeycomb.
3 . The integrated self-supporting and deformation-resistant driver's cabin
structure of claim 2 , wherein the sandwich structure is significantly reinforced in
the side pillars (30A, 30B) and reactor (32) in order to provide sufficient stiffness
and strength for resisting energy absorber collapse forces without permanent
deformation or damage.
4 . The integrated self-supporting and deformation-resistant driver's cabin
structure of claim 3 , wherein the internal structure in the side pillars (30A, 30B)
includes vertical columns of foam sandwiched between continuous vertical layers
of GFRP to produce a multi-layer sandwich construction.
5 . The integrated self-supporting and deformation-resistant driver's cabin
structure of claim 3 or claim 4 , wherein the internal structure in the side pillars is
reinforced to provide a high bending stiffness to the side pillars (30A, 30B).
6 . The integrated self-supporting and deformation-resistant driver's cabin
structure of any one of claims 3 to 5 , wherein the reactor structure (32) consists of
an array of bonded foam cores wrapped in glass fibre reinforced polymer (GFRP)
to produce a macro-cellular structure.
7 . The integrated self-supporting and deformation-resistant driver's cabin
structure of any one of claims 3 to 6 , wherein the reactor structure (32) is
reinforced so as such as to transfer static and crash loads to the main body
structure of the rail vehicle without flexural buckling.
8 . The integrated self-supporting and deformation-resistant driver's cabin
structure of any one of claims 1 to 7 , further comprising reinforcing roof beams
located towards the upper end of each of the side pillars, the composite sandwich
construction comprising an orientated fibre lay-up in the roof beams providing an
anisotropic strength with higher strength in a longitudinal direction of the roof
beams or providing an isotropic strength performance.
9 . The integrated self-supporting and deformation-resistant driver's cabin
structure of any one of claims 1 to 8 , further providing a side door and/or side
window opening.
10 . A modular front end structure (10) for a rail vehicle, including:
- the integrated self-supporting and deformation-resistant
driver's cabin structure (22) of any one of claim 1 to 9 ,
a distributed upper energy absorber means (20) consisting
of a crossbeam (20) extending continuously from one of
the side pillars to the other.
11. The modular front end structure of claim 10 , wherein the upper energy
absorber means comprises a collapsible structure extending from one of the side
pillars to the other such as to provide an energy absorption capability.
12 . The modular front end structure of claim 10 or claim 11, wherein the upper
energy absorber means (20) is formed as a multi-layer aluminium honeycomb
sandwich.
13 . The modular front end structure of any one of claims 10 to 12, wherein the
upper energy absorber means (20) is such as to provide lateral rigidity and
enhanced missile protection coverage for the driver.
14. The modular front end structure of any one of claims 10 to 13 , wherein the
crossbeam (20) is removably attached to the integrated self-supporting and
deformation-resistant driver's cabin structure.
15 . The modular front end structure of any one of claims 10 to 14, further
comprising lower, buffer-level energy absorber means.
16. The modular front end structure of claim 12, wherein the buffer-level energy
absorber means include individual second energy absorber elements located on
each side of the modular front end structure at the height of the reactor structure.
17 . The modular front end structure of claim 16, wherein the individual second
energy absorber elements are replaceable.