GB2075570A - Nuclear fall-out shelter - Google Patents

Abstract

An underground nuclear fall-out shelter has a plastics shell (1) which, apart from service and access openings, is waterproof and provided, if desired, with a concrete roof. The shelter has an access opening (4), an air system (9), (10), (11), (12), lighting, water storage, sanitation (13) and sewage facilities. <IMAGE>

Description

SPECIFICATION Nuclear fall-out shelter Background of the Invention The present invention relates to a nuclear fallout shelter. In recent years, particularly in Switzerland and the United States, much thought has been given to the design of nuclear fall-out shelters. At the present time, the intention is to give protection against nuclear weapons which maximize short-life destructive radiation but minimize biasting. Thus the general object of the shelter is not to resist intensive blast, but to hold the occupants in a protective environment for a relatively short period, say two weeks.

We believe that all recommended constructions are made of reinforced concrete. Reinforced concrete has a number of disadvantages when used in the construction of fall-out shelters, and these do not appear to have been fully appreciated. Thus reinforced concrete is expensive and the installation of a reinforced concrete shelter takes a long time, particularly due to the requirement for shuttering and the difficulty of working in an excavation. Furthermore, there is a danger that small cracks may appear in the reinforced concrete, either due to subsidence of differential contraction after the construction of the shelter or due to shock when a nuclear explosion occurs.It will be appreciated that the shelter may remain unused for many years, and if cracks occur before occupation, there may be water in the shelter when it is required for use; in the worst of circumstances, where there is a high water table, it may be full of water. If cracks occur when there is nuclear contamination, there is a danger that radioactive silt will be carried into the shelter by ground water or percolating water, and of course a large ingress of ground water would be disastrous. Reinforced concrete has a further disadvantage, which can only be avoided with the use of relatively expensive insulating materials, that it has a high thermal capacity but is not a very good insulant, so that it takes a long time to warm up when the shelter is occupied and causes condensation.In addition to this, reinforced concrete can itself have a large water content, and therefore require a considerable period to dry out and also cause mould growth, and also produces dust.

The Invention The present invention provides a nuclear fallout shelter, comprising a plastics material shell which, apart from service and access openings, is waterproof. The present invention also provides a nuclear fall-out shelter installation, comprising such a shell, buried in the ground.

The plastics material shell will keep water out and can keep the shelter completely dry between construction and eventual use. Furthermore, although the shelter is not intended to be blast proof, the slight flexibility of the plastic will enable the shell to deform slightly if it is subjected to light or medium shocks, without fracturing, so that even if say surrounding concrete is fractured, the shell will maintain a waterproof enclosure and prevent the ingress of any radioactive water-borne particles. Furthermore, plastics material is clean, in the sense that it does not give rise to dust, enabling the shelter of the invention to have a better appearance. The use of the plastics material shell enables very rapid installation to be performed, and it may be possible to install such a shelter in two days.This in itself can save cost, but it is believed that the plastics material as such and the associated fill materials will cost less than reinforced concrete. Further advantages are that plastics material is a relatively good insulator and does not have a very high thermal capacity (particularly in the thin sections that can be used), so that the internal face quickly attains the ambient temperature and there is low condensation, even in the high humidity environment that would be expected. Plastics material adsorbs very little moisture, and there is no drying out problem, and, with suitable choice of materials, no mould growth and no corrosion problems. The plastics material can be pre moulded to very fine tolerances, and this greatly assists in fitting out with pre-made furnishing kits.

When installing, the shell must be surrounded by sufficient soil or other material to give the necessary protection against radioactivity - for instance, it is recommended that there should be a ten inch (about 25cm) or even 40cm layer of concrete plus half a meter of soil above a buried shelter. It will be appreciated that in itself, plastics material is not normally a radioactive shield. With the present invention, it is preferred to place concrete (which may be of lean mix but is preferably strong mix) directly on top of the shell so that the shell act as shuttering for the concrete and, in the final construction, in effect acts as a slightly flexible waterproof liner to the concrete roof.The concrete is a very suitable material for absorbing the sort of radiation expected, but it also acts as a mass to hold the shell down should there be a flotation risk in high water-table areas and it helps spread loads such as those caused by vehicles passing overhead or the collapse of buildings. The concrete may also prevent crushing of the shelter due to a blast and also prevents all soil being stripped away from the shell by very high speed winds, and can form a good insuiator.

If the shell has a round top, it is preferred to place the concrete on top and to take the concrete to at least nearly the widest point of the shell as this gives good protection against loads and avoids any concentration of loads, as far as possible.

The basic requirements for a nuclear fall-out shelter have been published, and the shelter of the invention can include the following, which may be fitted before installation: a) An access opening, which can be in the form of a plastics material access shaft, preferably of cylindrical or rectangular shape, which is sealed to the main shell, the preferred maximum transverse dimension being from 750 to 900 millimetres. The access shaft is preferably on the central vertical plane of the main shell, though this need not necessarily be so. The access shaft can include two airtight, vertically-spaced closures, forming an air lock reducing the risk of radioactive particles falling into the shelter if anyone does have to enter or leave during the dangerous period.The top closure should be lockable (to prevent interference before the shelter is used), and the shaft can include a fixed ladder having an extensible portion which can be lowered down to the floor of the shell.

b) An air system. This will include an inlet duct, and outlet duct (or possibly a single two-way duct), a pump and a filter system. The pump will normally be a motor pump driven by batteries but may have an alternative facility for manual operation.

c) Lighting, which may be electricity with a power pack for two weeks at low wattage, with possibly a manual recharging device.

d) Water storage. Taint-free containers are now available.

e) Sanitation and sewage storage.

f) Radio contact.

g) Emergency exit tools, should the access opening be blocked.

h) Fire extinguisher.

i) Geiger counter.

j) Locker or shelf storage for items such as food and blankets.

The preferred shape of the shell is that of a horizontal axis cylinder. The use of a cylinder facilitates excavation if the cylinder is longer than it is wide, and a cylinder gives good resistance to ground, ground water and shock wave pressures.

Furthermore, the use of a cylinder enables a wide range of shelters, of different capacities, to be provided with the same cross-sectional dimensions so that the same range of furnishings can be used without difficulty. In this connection, it is possible to provide furnishing units (including items such as sanitation and kitchen equipment) which are dimensioned to fit properly within the cylinder and which can be slid in from the end during manufacture.

In general terms, there is preferably a floor within the shell which is raised above the bottom of the shell, leaving a space for storage of items such as fresh water and waste, and in the case of a shell with a round bottom, this enables a good width to be provided at floor level.

It should be noted that although the prime purpose of the shelter is that of protection against nuclear fall-out, the shelter could also be used for other purposes prior to a nuclear attack, such as a sauna, a general store, a wine cellar, a temporary bedroom, a small workshop, a playroom or an office, and for these purposes, can have mains supplies of electricity and even other services.

After an attack, the shelter may well be used as temporary accommodation.

Description of Preferred Embodiments The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a shelter in accordance with the invention, as it would be when installed below the ground, surrounding material not being shown; Figure 2 is a section along the line I1--I1 of Figure 1, showing the shelter and surrounding materials, details of the interior of the shelter being omitted; and Figures 3 to 6 are schematic perspective views showing arrangements making use of shells similar to that shown in Figures 1 and 2.

The shelter shown in Figures 1 and 2 has a main plastics material shell 1 which is in the form of a horizontal axis cylinder with domed ends. The shell is that already marketed by us as a cesspool.

The main part is a spirally-wound glass-reinforced plastics continuous tube, a preferred plastics material being glass-reinforced polyester resin.

The ends are vacuum formed from glassreinforced plastics (the preferred plastic being the same as that for the main part), half-lapped onto the ends of the tube with fibreglass applied over the joints so that it is completely waterproof.

However, the plastics material retains some flexibility in that it will bend somewhat without cracking. The preferred internal diameter is 2.5 metres; the preferred interior surface is a glass finish (very smooth), and it is possible to hold the tolerances to +1 mm. The length can be any suitable value, and can be as great as 7.7m or even greater. The preferred thickness of the plastics material of the main part and of the ends, is 14.5mm.

Inside the shell 1, on its bottom portion, are placed segment-shaped bearers 2 (see Figure 2) which can also be made of glass-reinforced plastics, which support a preferably timber floor 3.

The height of the floor 3 can be generally as indicated from the proportions in Figure 2, or the floor 3 can be even higher to allow more storage below it. The bearers 2, in addition to supporting the floor, contribute to the strength of the bottom of the shell 1 , the greatest ground water pressure occurring at the bottom.

A glass-reinforced plastics access shaft 4 is sealed to the top of the shell 1, after a suitable aperture has been cut. The shaft 4 can be made of the same plastics material as the shell 1, and the seal can be protected by winding glass-reinforced plastics around the join. The shaft is closed at the top by a lift-up hatch 5, which may for instance be made of 6mm steel, and is air and watertight. The bottom of the shaft is closed by a drop-down hatch 5, 6, which may be made of a lighter material than the top hatch 5, but should be air and watertight. There is a ladder 7 fixed inside the shaft 4, the ladder 7 having a slide-down extensible portion 8.

Internal equipment of the shelter has been referred to above, and the shelter is shown as having an air inlet pipe 9, a fan and filter box 10, a distribution duct 11 and an outlet pipe 12, as well as a lavatory 13, washbasins or sinks 14 and a fresh water supply 1 5. The various spaces are separated from one another by e.g. timber bulkheads 16, which do not go down below floor level.

A particularly convenient way of equipping and furnishing the shelter is to slide in the various units (bathroom pod, kitchen pod, living room pod and bedroom pod etc.) as pre-fabricated structures, from one end of the shell 1, before closing the end.

The units can include one bulkhead or even multiple bulkheads. The glass finish in the interior of the shell 1 and the close tolerances facilitate such a form of construction.

In practice, the shelter can be supplied just with the floor 3, or with the floor 3 and essential equipment (for instance for "do it yourself" completion) or fully equipped.

Installation can be performed as follows: a) Excavate a hole as indicated in Figure 2; the excavation should allow a space of at least 25cm on either side of the shell 1.

b) Place concrete (which may be lean mix concrete) 1 7 on the bottom of the hole; c) Before the concrete has set, lower the shelter into the hole so that it rests on the concrete 17; d) The hole is backfilled up to a level half-way up the shell 1; this backfilling can be done e.g.

with graded material or lean or strong mix concrete, but it is believed that graded backfill is satisfactory; by graded backfill is meant any suitable particulate material, whether soil on site or transported e.g. sand, gravel or chalk, which does not contain pieces above a certain size, e.g.

above 1 4mm maximum or mesh size; the concrete would be used if added protection was required or if there was a high water table; e) Lean or strong mix concrete is placed over the shoulders of the shell 1 and is taken up to such a level as to leave e.g. 25cm of concrete above the top of the shell 1; f) Half a meter of soil is then placed on top of the concrete, bringing the soil level up to the top of the shaft 4. In practice, this can be varied as desired, for instance filling completely with concrete dr putting in soil and then topping off with a concrete slab, so as to protect the top of the shaft 4.

Figures 3 to 6 show that the shell 1 can be coupled to other shells in any suitable or convenient way.

Claims (11)

1. A shelter, comprising a plastics material shell which, apart from service and access openings, is waterproof.

2. The shelter of Claim 1, wherein the shell is in the shape of a horizontal axis cylinder.

3. The shelter of Claim 2, wherein the shell contains at least one furnishing unit which is dimensioned to fit within the cylinder.

4. The shelter of any one of the preceding Claims, wherein there is a floor within the shell which is raised above the bottom of the shell.

5. The shelter of any one of the preceding Claims, and including items (a)-(j) set forth herein.

6. A shelter, substantially as herein described with reference to, and as shown in, Figures 1 and 2 or any one of Figures 3 to 6 of the accompanying drawings.

7. A shelter installation, comprising the shelter of any one of Claims 1 to 5 with the shell installed below the ground level.

8. The shelter installation of Claim 7, wherein concrete has been placed directly on top of the shell so that the shell acted as shuttering for the concrete and, in the installation, in effect acts as a slightly flexible waterproof liner to a concrete roof.

9. The shelter installation of Claim 8, wherein the shell has a round top and the concrete was taken down to at least nearly the widest point of the shell.

10. A shelter installation, substantially as herein described with reference to, and as shown in, Figures 1 and 2 or any one of Figures 3 to 6 of the accompanying drawings.

11. A method of installing a shelter, comprising providing the shelter of any one of Claims 1 to 6, excavating a suitable hole in the ground, placing the shell in the hole, and burying the shell.

1 2. A method of installing a shelter, substantially as herein described with reference to, and as shown in, Figures 1 and 2, or Figures 3 to 6, of the accompanying drawings.