GB2518952A

GB2518952A - Electrical power generation

Info

Publication number: GB2518952A
Application number: GB1413497.7A
Authority: GB
Inventors: Kurt Canfield
Original assignee: SAFETY CRITICAL ANALYSIS Ltd
Current assignee: SAFETY CRITICAL ANALYSIS Ltd
Priority date: 2013-08-31
Filing date: 2014-07-30
Publication date: 2015-04-08
Also published as: WO2015028795A1; GB2517797A; GB201315636D0; GB201413497D0

Abstract

Apparatus for generating electrical power from the decay heat of nuclear fuel elements and/or of nuclear fuel waste, or from another low temperature heat source using the principle of the Seebeck or other power generation effects. Also disclosed is a method of generating electrical power comprising: providing a nuclear fuel flask, crate or container 1 containing nuclear fuel or waste 9 generating heat, the flask separating the nuclear material from the external environment; placing the flask in a water-filled cooling pond or air-cooled repository; providing thermoelectric junction comprised of an n-type semiconductor 16 and a p-type semiconductor 17 connected by conducting members 15; and providing the electrical power from the thermoelectric junction for use. The thermoelectric junction/Seebeck Effect device may also comprise a junction of dissimilar metals/alloys. The thermoelectric junction may be one of a plurality of junctions which can be connected in either series or parallel. The thermoelectric junction may form part of the wall, lid and/or base of the flask.

Description

ELECTRICAL POWER GENERATOR

This specification relates to electrical power generation from items where there is a temperature difference. It is particularly relevant to utilising the decay heat from used fission fuel elements either immediately after they have been removed from a nuclear reactor or during long term storage in repositories but the principle of the invention is equally applicable to other examples where low temperature heat has to be removed or otherwise wasted, e.g. Combined Heat and Power (CHP) installations, air conditioning systems, etc. When fissile fuel elements are removed from a nuclear reactor, they usually emit considerable quantities of decay heat and harmful radiation. So, the elements are transferred from the reactor, via a special handling facility, into thick walled metal flasks, to storage ponds. Here, the flasks are kept under several metres depth of water for long periods of time, e.g. years or even decades, until the material in the elements is either reprocessed to extract fuel for further use in a reactor or decay products are separated for Indefinite storage, e.g. in a vitrified material. All the time the fuel elements are in the pond, decay heat is being produced, mostly on the nuclear half-life basis. The level of decay heat reduces over time following a basically exponential-type curve.

Nuclear fuel storage flasks may be sealed or have means to allow the cooling water in the ponds to flow through under the influence of natural convection. Even when water can flow through the flasks, a lid is usually fitted and provided with a means to collect any radioactive gases produced. This lid reduces the natural convective flow and so allows the temperature inside the flask to rise. The flow passages provided inside the flask are large enough to keep the water from boiling; this is important as heat transfer from fuel elements to a gas (steam) is much less efficient than directly to liquid water. The bulk water in the pond has to be cooled to maintain an appropriate temperature difference to drive the natural convection cooling process. (The engineering tern for a temperature difference is AT (Delta 1) and will be used henceforth in this specification.) Thus, a typical temperature inside a flask might be 70-80°C and the bulk temperature of the pond might be 40-50°C so that the AT could be between 20-40°C. This is a relatively small AT and the energy is 4low temperature heat'. In the case of high level, vitrified waste in containers in an air-cooled repository, the core temperature might be 200+°C and the container surface temperature, say, 40°C, giving a iT of around 160+°C. Though this is a more useful AT, it is still low temperature heat.

From an engineering (thermodynamic) point of view, this is not very useful heat. It could be S used to boll a refrigerant, to use as a working fluid, to generate electrical power but the relatively low quantity of heat available and capital cost of the installation make this uneconomic.

Another possible application could be to heat the water in a swimming bath or space heating, e.g. for greenhouses. An additional problem here is that the pond water is radioactive and so would have to be passed through a heat exchanger to give uncontaminated water for use in such a heating system. This would require additional capital equipment and be an additional heat loss, so further reducing the effective AT available. is

Thus, there is a need for an economic method of using the low temperature decay heat from nuclear fuel elements, and àther such sources, beneficially.

According to the invention, there is provided apparatus for generating electrical power from the decay heat of nuclear fuel elements or of nuclear fuel waste, or from another low temperature heat source, using the principle of the Seebeck or other power generation effects.

According to a first variation of the apparatus of the invention, the Seebeck Effect is provided by n-and p-semiconductors formed into an electrical power generating cell.

According to a second variation of the apparatus of the invention, the Seebeck Effect is provided by a pair of dissimilar metals or alloys formed into an electrical power generating cell.

According to a third variation of the apparatus of the invention, the means to provide the Seebeck Effect are formed into a plurality of separate cells.

According to a fourth variation of the apparatus of the invention, the cell(s) providing the Seebeck Effect is(are) located in between a source of heat and a heat sink or the external casing of a nuclear fuel flask and is(are) in thermal contact with both the source of heat and the heat sink or said external casing.

According to a fifth variation of the apparatus of the invention, the plurality of separate cells are formed to provide a part of the wall, and / or lid and / or base of the flask / crate containing the nuclear fuel elements.

S According to a sixth variation of the apparatus of the invention, the plurality of separate cells are formed to provide a part of the mechanical strength of the wall, and / or lid and / or base of the flask I crate containing the nuclear fuel elements.

According to a seventh variation of the apparatus of the invention, the separate cells, or groups of cells, are connected in series.

According to an eighth variation of the apparatus of the invention, the separate cells, or groups of cells, are connected in parallel.

is According to a ninth variation of the apparatus of the invention, the separate cells are arranged into a band(s) across, or up and down, the faces of the nuclear fuel containing flask I crate.

According to a tenth variation of the apparatus of the invention, electrical connections are provided to take the power output from the I each individual band(s) to a collection point(s) on the flask I crate or its lid.

According to an eleventh variation of the apparatus of the invention, the collection point(s) are provided with a connection(s) to which a power take off is attachable.

According to a twelfth variation of the apparatus of the invention, the power take off is attached to the flask connection before the flask is placed in the cooling pond.

According to a thirteenth variation of the apparatus of the invention, all the electrical collections, including the power take off, are waterproofed.

According to a fourteenth variation of the apparatus of the invention, electrical equipment is provided to convert the power generated by the apparatus of the invention into a usable form.

According to a fifteenth variation of the apparatus of the invention, the power generated is used replace a part of the mains power required to run the fuel element storage facility or another facility.

According to a sixteenth variation of the apparatus of the invention, the power generated is used to charge / recharge a battery.

According to a seventeenth variation of the apparatus of the invention, the nuclear fuel elements are in a cooling pond.

According to an eighteenth variation of the apparatus of the invention, the nuclear fuel waste is in a repository or other appropriate storage.

According to the invention, there is provided a method for generating electrical power from the decay heat of nuclear fuel elements or nuclear fuel waste using the principle of the Seebeck or other power generation effects comprising:-i) providing a nuclear fuel flask, crate or container, containing nuclear fuel elements emitting nuclear decay heat into a heat transfer medium, and having faces separating the contents of the flask from the external environment; ii) placing the flask! crate / container in a heat sink, such as a water-filled cooling pond, or air-cooled repository; iii) providing a pair of n-and p-type semiconducting elements in electrical contact with each other at one of their ends; iv) arranging the semiconductors so that the other end of the n-type semiconductor is adjacent to and in thermal contact with the hot internal side of a face of the flask / crate I container and that the other end of the p-type semiconductor is adjacent to and in thermal contact with the cold external face of the flask / crate / container; v) connecting an electrical circuit between the hot end of the n-type semiconductor and the cold end of the p-type semiconductor to form a cell and withdrawing electrical power from the circuit; and vi) providing the electrical power from the circuit for use, either directly as generated or in a converted and more usable form, as required.

According to a first variation of the method of the invention, the Seebeck Effect cell is formed by providing two dissimilar metals or alloys in electrical contact at one of their ends with their distal ends in thermal contact with the hot and cold members respectively.

According to a second variation of the method of the invention, a plurality(ies) of cells is(are) connected in series and I or in parallel.

According to a third variation of the method of the invention, the separate electrical power(s) from the I each plurality of cells are combined and connected to a take off point(s).

According to a fourth variation of the method of the invention, a connection(s) attachable to the power take off point(s) is I are provided.

According to a fifth variation of the method of the invention, the connection(s) is(are) attached to the power take off point(s) before the flask I crate is placed in the heat sink.

According to a sixth variation of the method of the invention, electrical equipment is provided to convert the power from the flask I crate to a usable form.

According to a seventh variation of the method of the invention, the usable power is provided to run equipment at the storage facility or stored in a battery.

According to an eighth variation of the method of the invention, the extraction of additional energy via the Seebeck Effect reduces the total time for which decay heat has to be extracted to reach the required radioactive level for further processing or indefinite storage.

In a preferred application of the apparatus of the invention, a plurality of n-and p-semiconductors are built into the walls and lid of a nuclear fission fuel element flask or crate so that, when the flask or crate is placed in a cooling pond, they form a series of individual Seebeck Effect cells using the temperature difference (AD due to the decay heat between the hot interior and the cold cooling pond to generate an electrical current. By connecting the cells in series and I or parallel, the output from individual cells is combined to form usable electrical power. The cells may be arranged in bands across, or up and down, the side walls, or across the lid and I or base, and connected together to combine the output of many cells and the combined output of many bands may be further combined so that all I most of the power generated can be accessed via one or more power take offs.

The power produced is processed by electrical means to convert it to a form suitable for operating conventional electrical equipment or storage in a battery.

An alternative preferred application uses pairs of dissimilar metals connected end to end S with the distal ends in thermal contact with the respective hot interior and cold exterior to form the Seebeck Effect cells.

The principle of the invention is applicable to all sources of low temperature waste hiat, e.g. nuclear waste both in flasks in cooling ponds and to vitrified, high level waste in air-cooled repositories, power generating facilities, air conditioning systems, etc. For a clearer understanding of the invention and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:-is Figure 1 is a perspective view of a nuclear fuel element flask, or crate, in a cooling pond; Figure 2 is a side elevation of the flask in Fig. 1; Figure 3 is a plan view of the base of the flask in Fig. 1; Figure 4 is a part perspective view of a corner of the flask of Fig. 1; Figure 5 is a perspective view of the lid for the flask of Fig. 1; Figure 6 is a diagrammatic representation of the principle of the Seebeck Effect

(Prior Art);

Figure 7 is part sectional plan view of one form of the apparatus of the invention incorporated into a wall of the flask / crate of Fig. 1; Figure 8 is an enlarged plan view of the apparatus shown in Fig. 7, explaining the operation of the Seebeck Effect, as taught in Fig. 6; Figure 9 is a part sectional plan view, or elevation, of another form of the apparatus of the invention incorporated into a wall of the flask I crate of Fig. 1; and Figure 10 is a diagrammatic side elevation of a decay fuel flask or crate, showing the heat flow from the interior outwards to the cooling pond.

In the following description, the same reference numeral is used for the same component in different Figures and I or for different components fulfilling identical functions.

Referring to Figs. 1-5, a fuel flask, or crate, I consists of four sides 2, a base 4 and a lid 7 and is placed under water 6 in cooling pond 6. Sides 2 and base 4 are provided with pins 3 or fins (not shown) to facilitate heat transfer from flask I to cooling water 6. Flask us filled with fuel elements 9, stacked in assemblies 10 (Figs. 1, 4 and 7-9); though elements 9 appear to be closely packed, considerable space is provided between adjacent elements 9 to allow cooling water 6A to circulate in both vertical and horizontal directions 6B.

Flask I stands on feet 4A, which allow water 6 to circulate around pins 3 on base 4 and enter flask I via coolant inlet holes 5 in base 4. Outlet 8 in lid 7 is provided to allow coolant 6 to flow freely 6A through the inside of flask 1. (Outlet 8 is adapted (not shown) to separate any gas produced as a result of fission decay reactions and duct it to an appropriate collection point (not shown).) Though coolant 6 can flow freely 6A through flask 1, natural convection 6B of coolant 6A inside flask I is the main means by which decay heat is passed via sides 2, base 4, lid 7 and pins 3 to pond coolant 6.

Fig. 6 is a prior art illustration of the principle of the Seebeck Effect, where an n-type 1 7A and a p-type 16A semi-conductors are placed between a heat source 19 and a cool heat sink 20. The electrical circuit is completed via conductors 1 5A, 1 SB and I SC, wiring 21 and resistor 22. As shown, heat source 19 drives electrons 23(S) towards sink 20 (shown by the un-numbered arrows), creating a potential difference and current 25, flowing in the direction shown by arrows 25A. This causes positive holes 24 (9) in the p-type member 1 6A to flow within that member (again towards sink 20, arrowed) in the direction 25A of the current 25. Current 25 flows via wiring 21 to generate power in resistor 22.

Members 16A and 17A can be dissimilar metals (Fig. 9) but p-type and n-type semiconductors are preferred (Fig. 7) as they have more free electrons and positive holes available to move and so can generate a greater current in resistor 22 than would be the case with dissimilar metals, where only the valency electrons are free to move.

Referring to Fig. 7, a part of the wall 2 (Fig. 2) of a flask 1 is shown separating fuel elements 9, in assemblies 101 from pond water 6. Wall 2 is a composite sandwich' structure consisting of inner and outer metal containment walls 12 and 11 respectively and inner and outer insulating membranes 13 and 14 respectively. Between membranes 13 and 14 is a castellated arrangement of conducting members 15, n-type semiconductors 16 and p-type semiconductors 17. Spaces 18 may be either empty voids, possibly partial vacuums, or filled with a material providing both electrical and thermal insulation; the key role of insulation 18 is to isolate electrically the n-and p-type semiconductors. a

Fig. 8 is an enlargement of the sandwich' wall 2 shown in Fig. 7 and also indicates the movement of electrons 23 () and positive holes 24 (@) creating current 25, shown by the sinusoidal dashed, arrowed line 25. Arrow 25 shows the flow of current generated by the plurality of n-and p-semiconductors 17 and 16 respectively linked in series by conductors 15 and separated by insulators 18. A Seebeck Cell generates a high voltage (V) but low current (I). As shown, separate Seebeck Cells are connected in series so that the output current is appropriately increased.

As shown (Figs. 7, 8 & 9) Seebeck Cells are arranged in a band across the flask wall 2.

Depending on the electrical parameters, the bands could extend for the whole width a wall 2, or of a lid 7, and a series of bands, one above another (not shown), could essentially fill the whole area of wall 2 from top to bottom, or across all the area of lid 7. As more heat is likely to be transferred by natural convection 6B (Fig. 2) via the upper and middle sections of walls 2, the bands of may be restricted to these parts of walls 2, where the AT will be greater, rather than towards the base of the wall 2.

Bands of cells could be arranged in vertical lines up and down the walls 2 of flasks 1, if required.

Figs. 1-4 show how the cooling pins (or fins) 3 on the flasks I cover the whole external surfaces of the sides and the base (excluding the area of feet 4A), i.e. to give the maximum cooling area to avoid creating any hot spots inside the flask. Similarly, in the preferred design here, the bands of Seebeck Effect cells would extend the maximum practical height and width (or crosswise) dimensions of all sides, bases and lids (subject to any structural considerations of the flasks, e.g. the scantlings of the corner posts, etc.), thus giving the maximum power generation potential, without jeopardising the heat transfer (cooling) properties of the flasks.

Japanese Patent Application No. 2006 13971 7A discloses a similar teaching but the thermo-elernents 13 taught are aligned only normally to (in way of) the radioactive waste G, and the rest of the containment flask 11 is formed of an insulating material 12. This will result in higher internal temperatures in the flask, or parts of it, as the main routes for heat loss is via therrno-elements 13, i.e. hot spots will occur away from these heat transfer routes. It is a general rule that the rate of a chemical reaction doubles with a 10°C rise in temperature so that this teaching could lead to significantly increased temperatures inside the flask and possibly a run-away condition. It is a feature of the present disclosure that the normal cooling regime is maintained over the whole flask surface area, thus ensuring safe operation. As shown in the Figs. 7 and 8 example, pins 3 are provided to discharge the heat as efficiently as practicable to the cool sink.

Practical considerations will determine construction details, e.g. the vertical height of a band of cells in wall 2 may depend on the electrical parameters of the semiconductors and the sizes in which they are available. Adjacent bands of cells would be separated by strips of electrically insulating material (not shown). It may be necessary to separate the bands with strips of resilient material (not shown) to connect inner 12 and outer 11 flask wall members together to give flask I crate I adequate mechanical strength to be handled in and out of pond 6 and within a pond 6, e.g. by a crane (not shown).

Appropriate electrical connections (not shown) will be provided at the ends of the bands of cells to connect together all those bands on one wall 2 and link the power outputs of all four walls, and the lid, and take them to one / more connection point(s) (not shown), to which a waterproof power take-off lead(s) would be fitted before flask 1 was placed in pond 6. As stated, the power output would be modest but could be changed, via solid state electronics, into usable power, e.g. to power electronic apparatus, or used to charge batteries (not shown), as required.

Fig. 9 shows another embodiment of the Seebeck Effect, where, in each cell, a first metal / alloy 28 is electrically connected to a second metal I alloy 29. A first electrically insulating plate 26, adjacent to inner wall 12 of sandwich' wall 2, forms the heat input member. Also included in plate 26 is an electrical conductor (not shown), which is electrically fast with all first members 28. A second electrically insulating plate 27 separates second metal / alloy members 29 from outer wall 11 of sandwich' wall 2 and is part of the cold sink 6, 20. As before, an electrical conductor (not shown) is electrically fast with all second members 29.

The individual Seebeck cells may be insulated from each other 39, if required.

Here, the Seebeck cells are connected in parallel and, as taught above with the Fig. 7 embodiment, the cells may be arranged in separate bands and the outputs from the conductors in plates 26 and 27 (not shown) taken to a collection point(s) Fig. 10 shows a simple diagrammatic representation of the heat flow, designated as Q, out of flask 1 into the water 6 of cooling pond 6. The general equation for heat transfer is: Q=U.A.AT where U is a coefficient defining the overall type of heat transfer, e.g. metal surface to a liquid, A is the surface area and AT is the temperature difference, i.e. T -T2.

There are two applications of heat transfer here, i.e. firstly from the insides of fuel elements 9 to the cooling water 6A inside flask I and secondly from internal water 6A via sandwich' walls 2 and pins! fins 3, lid 7 and base 4 to water 6 in.cooling pond 6. It is the second of these heat transfers that is important here.

Q is determined by the absolute level of decay heat being produced by fuel elements 9 and A is the area of walls 2, pins I fins 3, lid 7 and base 4. However, U is the critical factor here and defines the heat transfer resistance provided by the sandwich' of wall members, as shown in Fig. 7, i.e. two metal plates 11, 12, two insulating layers 13, 14 and the Seebeck section 15, 16, 17 and 18. (U also includes terms to include heat transfer from water 6A to the internal flask wall and from pins 3 to pond water 6.) U for the Seebeck sandwich will be smaller than for a single metal plate 11, as in the traditional decay heat flask! crate (not shown), i.e. there will be slightly more resistance to heat transfer. Thus, as A will be essentially the same for both the traditional and Seebeck flasks 1, AT will have to be greater to achieve the same heat transfer 0. Thus, as T2 is unlikely to be lower, T1 will have to be greater than that in a traditional flask. (N.B. It is important to ensure that the bulk water 6A does not boil, i.e. T remains below 100°C, as heat transfer from a metal to a gas is poorer than that from a metal to a liquid; however localised boiling on the surface of elements 9 followed by immediate condensation is acceptable and could enhance the overall U value.) The slightly greater AT across the Seebeck sandwich will work to the benefit of the Invention as a greater AT will act to generate more electrical power.

As previously stated, it is a general chemical rule that increasing the temperature at which a reaction occurs by 10°C doubles the reaction rate. Whether this applies to nuclear half life decay heat reactions is not clear but there are other decay heat reactions to which it probably does apply, so the slightly higher value ofT1 will be likely to reduce the total time that fuel elements have to be kept in ponds until they can be reprocessed. It will be noted that, as cooling is provided over essentially the whole of the flask surface, no hot spots can occur and, thus, the decay cooling will be fully controlled.

Thermodynamically, the total decay heat 0 is removed in two parts, i.e. an equivalent portion Q' in the form of electrical energy, via the Seebeck cells, and the balance 0" as conventional heat transferred to water 6, so that (as shown in Fig. 10): Q=Q,+Q,'.

The relative proportions of 0' and 0" will have to be detem,ined by experiment but, as there is less thermal resistance transferring heat 0 into the Seebeck section 15, 16, 17 and 18, than completely through sandwich' wall 2, it is logical to assume that the equivalent portion Q' converted to electrical energy could be greater than Q".

Thus, the principle of the invention and the introduction of the Seebeck section 15, 16, 17 and 18 to the walls of flasks I crates 1 will produce usable electrical energy from what would otherwise be waste heat and will probably reduce the overall time fuel elements have to be kept in cooling ponds 6 until they can be reprocessed. If, as surmised, the Seebeck equivalent heat Q' is significant this could also reduce the external cooling required to keep cooling ponds 6 at an acceptable temperature.

As stated earlier, the rate of radioactive decay follows an essentially exponential curve and after a certain period of time, the heat generated Q will drop to a level at which electrical power generation will no longer be economical. When this happens the fuel assemblies 10 may be removed from the Seebeck flask or crate 1, and placed in a traditional flask (not shown) for the rest of the decay period. The Seebeck flask I crate 1 may then be refilled with fuel elements 9 newly removed from the reactor.

The description heretofore has dealt with intermediate level radioactive decay of fuel elements in cooling ponds. The principle of the invention is equally applicable to high level radioactive waste, e.g. after vitrification and during long term storage in an air-cooled repository or other appropriate storage. Here the AT is likely to be higher than for the cooling pond case so more electricity should be generated per unit surface area than in the cooling pond case but, otherwise, the principle of the application is exactly the same as taught above.

The skilled man will appreciate other applications of the principle of the invention, e.g. the use of low temperature heat from cooling water in conventional power stations or from Combined Heat and Power stations or from air conditioning systems, etc.

Claims

Claims:- 1. Apparatus for generating electrical power from the decay heat of nuclear fuel elements or of nuclear fuel waste, or from another low temperature heat source, using the $ principle of the Seebeck or other power generation effects.
2. Apparatus for generating electrical power, as claimed in claim 1, wherein the Seebeck Effect is provided by n-and p-semiconductors formed into an electrical power generating cell.
3. Apparatus for generating electrical power, as claimed in claim 1, wherein the Seebeck Effect is provided by a pair of dissimilar metals or alloys formed into an electrical power generating cell.
4. Apparatus for generating electrical power, as claimed in claims 2 or 3, wherein the means to provide the Seebeck Effect are formed into a plurality of separate cells.
5. Apparatus for generating electrical power, as claimed in claim 4, wherein the cell(s) providing the Seebeck Effect is(are) located in between a source of heat and a heat sink or the external casing of a nuclear fuel flask and is(are) in thermal contact with both the source of heat and the heat sink or said external casing.
6. Apparatus for generating electrical power, as claimed in claim 5, wherein the plurality of separate cells are formed to provide a part of the wall, and I or lid and I or base of the flask / crate containing the nuclear fuel elements.
7. Apparatus for generating electrical power, as claimed in claim 6, wherein the plurality of separate cells are formed to provide a part of the mechanical strength of the wall, and I or lid and I or base of the flask / crate containing the nuclear fuel elements.
8. Apparatus for generating electrical power, as claimed in claims 6 or 7, wherein the separate cells, or groups of cells, are connected in series.
9. Apparatus for generating electrical power, as claimed in claim 6 or 7, wherein the separate cells, or groups of cells, are connected in parallel.
10. Apparatus for generating electrical power, as claimed in claims 8 or 9, wherein the separate cells are arranged into a band(s) across, or up and down, the faces of the nuclear fuel containing flask / crate.
11. Apparatus for generating electrical power, as claimed in claim 10, wherein electrical connections are provided to take the power output from the / each individual band(s) to a collection point(s) on the flask I crate or its lid.
12. Apparatus for generating electrical power, as claimed in claim 11, wherein the collection point(s) are provided with a connection(s) to which a power take off is attachable.
13. Apparatus for generating electrical power, as claimed in claim 12, wherein the power take off is attached to the flask connection before the flask is placed in the cooling pond.
14. Apparatus for generating electrical power, as claimed in claims 12 or 13, wherein all the electrical collections, including the power take off, are waterproofed.
15. Apparatus for generating electrical power, as claimed in claims 12-14, wherein electrical equipment is provided to convert the power generated by the apparatus of the invention into a usable form.
16. Apparatus for generating electrical power, as claimed in any preceding claim, wherein the power generated is used replace a part of the mains power required to run the fuel element storage facility or another facility.
17. Apparatus for generating electrical power, as claimed in any preceding claim, wherein the power generated is used to charge I recharge a battery.
18. Apparatus for generating electrical power, as claimed in any preceding claim, wherein the nuclear fuel elements are in a cooling pond.
19. Apparatus for generating electrical power, as claimed in any preceding claim, wherein the nuclear fuel waste is in a repository or other appropriate storage.
20. A method for generating electrical power from the decay heat of nuclear fuel elements or nuclear fuel waste using the principle of the Seebeck or other power generation effects comprising:-i) providing a nuclear fuel flask, crate or container, containing nuclear fuel elements or nuclear fuel waste emitting nuclear decay heat into a heat transfer medium, and having faces separating the contents of the flask from the external environment; ii) placing the flask / crate I container in a heat sink, such as a water-filled cooling pond, or air-cooled repository; iii) providing a pair of n-and p-type semiconducting elements in electrical contact with each other at one of their ends; iv) arranging the semiconductors so that the other end of the n-type semiconductor is adjacent to and in thermal contact with the hot internal side of a face of the flask / crate I container and that the other end of the p-type is semiconductor is adjacent to and in thermal contact with the cold external face of the flask / crate I container; v) connecting an electrical circuit between the hot end of the n-type semiconductor and the cold end of the p-type semiconductor to form a cell and withdrawing electrical power from the circuit; and vi) providing the electrical power from the circuit for use, either directly as generated or in a converted and more usable form, as required.
21. A method for generating electrical power as claimed in claim 20, wherein the Seebeck Effect cell is formed by providing two dissimilar metals or alloys in electrical contact at one of their ends with their distal ends in thermal contact with the hot and cold members respectively.
22. A method for generating electrical power as claimed in claims 20 or 21, wherein a plurality(ies) of cells is(are) connected in series and I or in parallel.
23. A method for generating electrical power as claimed in claim 22, wherein the separate electrical power(s) from the I each plurality of cells are combined and connected to a take off point(s).
24. A method for generating electrical power as claimed in claim 23, wherein a connection(s) attachable to the power take off point(s) is I are provided.
25. A method for generating electrical power as claimed in claim 24, wherein the connection(s) is(are) attached to the power take off point(s) before the flask / crate is placed in the heat sink.
26. A method for generating electrical power as claimed in claims 24 or 25, wherein electrical equipment is provided to convert the power from the flask I crate to a usable form.
27. A method for generating electrical power as claimed in claim 26, wherein the usable power is provided to run equipment at the storage facility or stored in a battery.
28. A method for generating electrical power as claimed in claims 20-27, wherein the extraction of additional energy via the Seebeck Effect reduces the total time for which decay heat has to be extracted to reach the required radioactive level for further processing or indefinite storage.
29. Apparatus and method for generating electrical power as described in and by the above description with reference to accompanying Figures 1-5 and 7-10.