A Seminar Report

On

NUCLEAR MICRO - BATTERY

Submitted by

VISHNU M T

in partial fulfilment for the award of the degree of

Bachelor of Technology (B. Tech)

in

INSTRUMENTATION TECHNOLOGY

DEPARTMENT OF INSTRUMENTATION

COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY

KOCHI-682022

OCTOBER 2015

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CERTIFICATE

This is to certify that the seminar report entitled

NUCLEAR MICRO-BATTERY

is a bonafide record of the work done by MR. VISHNU M T ,

Roll No: 90012068 under our supervision in partial fulfilment of

the requirements for the award of Degree of Bachelor of Technology

in Instrumentation Technology from Cochin University of Science and

Technology, Kochi for the year 2015-2016

OCTOBER 2015

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Dr. K.N Madhusoodanan

Professor, Dept. of Instrumentation

Seminar Co-coordinator

Dr. K Rajeev Kumar

Professor and Head of Department

Dept. of Instrumentation

ACKNOWLEDGEMENT

It is matter of great pleasure for me to submit this seminar report on

“NUCLEAR MICRO-BATTERY”, as a part of curriculum forward

of “Bachelor of Technology with specialization in Instrumentation

Technology” degree of Department Of Instrumentation, CUSAT.

I am extremely thankful to Dr. K. Rajeev Kumar, Head Of Department, Department of Instrumentation, CUSAT for permitting me to undertake this work.

I express my heartfelt gratitude to my respected Seminar guide Dr. K.N. Madhusoodanan for his kind and inspiring advice which helped me to understand the subject and its semantic significance. He enriched me with valuable suggestions regarding my topic and presentation issues. I am also very thankful to my colleagues who helped and co-operated with me in conducting the seminar by their active participation.

At the last but not least, I am thankful to my parents, who have encouraged & inspired me in every possible way.

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ABSTRACT

Nuclear batteries harvest energy from radioactive specks and supply power to micro electromechanical systems (MEMS). This paper describes the viability of nuclear batteries for powering realistic MEMS devices. Nuclear batteries are not nuclear reactors in miniatures, but the energy comes from high-energy particles spontaneously emitted by radioactive elements. Isotopes currently being used include alpha and low energy beta emitters. Gama emitters have not been considered because they would require a substantial amount of shielding. The sources are available in both solid and liquid form. Nuclear batteries use the incredible amount of energy released naturally by tiny bits of radioactive material without any fission or fusion taking place inside the battery. These devices use thin radioactive films that pack in energy at densities thousands of times greater than those of lithium-ion batteries. Because of the high energy density nuclear batteries are extremely small in size. Considering the small size and shape of the battery the scientists who developed that battery fancifully call it as "DAINTIEST DYNAMO". The word 'dainty' means pretty

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Table of ContentsChapter page no:

1. INTRODUCTION 62. HISTORICAL DEVELOPMENTS 8

3. ENERGY PRODUCTION MECHANISM 9

4. FUEL CONSIDERATIONS 19

5. ISOTOPE SELECTION 20

6. INCORPORATION OF SOURCE INTO DEVICE 22

7. ADVANTAGES 24

8. DISADVANTAGES 25

9. APPLICATIONS 26

10.CONCLUSION 30 11.REFERENCES 31

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INTRODUCTION

A burgeoning need exists today for small, compact, reliable, lightweight and self-contained

rugged power supplies to provide electrical power in such applications as electric

automobiles, homes, industrial, agricultural, recreational, remote monitoring systems,

spacecraft and deep-sea probes. Radar, advanced communication satellites and especially

high technology weapon platforms will require much larger power source than today’s power

systems can deliver. For the very high power applications, nuclear reactors appear to be the

answer. However, for intermediate power range, 10 to 100 kilowatts (kW), the nuclear reactor

presents formidable technical problems.

Because of the short and unpredictable lifespan of chemical batteries, however,

regular replacements would be required to keep these devices humming. Also, enough

chemical fuel to provide 100 kW for any significant period of time would be too heavy and

bulky for practical use. Fuel cells and solar cells require little maintenance, and the latter need

plenty of sun.

Thus the demand to exploit the radioactive energy has become inevitably high.

Several methods have been developed for conversion of radioactive energy released during

the decay of natural radioactive elements into electrical energy. A grapefruit-sized

radioisotope thermo- electric generator that utilized heat produced from alpha particles

emitted as plutonium-238 decay was developed during the early 1950’s.

Since then the nuclear has taken a significant consideration in the energy source of

future. Also, with the advancement of the technology the requirement for the lasting energy

sources has been increased to a great extent. The solution to the long term energy source is, of

course, the nuclear batteries with a life span measured in decades and has the potential to be

nearly 200 times more efficient than the currently used ordinary batteries. These incredibly

long-lasting batteries are still in the theoretical and developmental stage of existence, but they

promise to provide clean, safe, almost endless energy.

Unlike conventional nuclear power generating devices, these power cells do not rely on

a nuclear reaction or chemical process do not produce radioactive waste products. The nuclear

battery technology is geared towards applications where power is needed in inaccessible

places or under extreme conditions.

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.

Microelectromechanical Systems (MEMS) have not gained wide use because they lack the on device power required by many important applications. Several forms of energy could beConsidered to supply this needed power (solar, fossil fuels, etc.), but nuclear sources provide an intriguing option in terms of power density and lifetime. This paper describes several approaches for establishing the viability of nuclear sources for powering realistic MEMS devices. Isotopes currently being used include alpha and low-energy beta emitters. The sources are in both solid and liquid form, and a technique for plating a solid source from a liquid source has been investigated. Several approaches are being explored for the production of MEMS power sources. The first concept is a junction-type battery. The second concept involves a more direct use of the charged particles produced by the decay: the creation of a resonator by inducing movement due to attraction or repulsion resulting from the collection of charged particles. Performance results are provided for each of these concepts.

The researchers envision its uses in pacemakers and other medical devices that would otherwise require surgery to repair or replace. Additionally, deep-space probes and deep-sea sensors, which are beyond the reach of repair, would benefit from such technology. In the near future this technology is said to make its way into commonly used day to day products like mobile and laptops and even the smallest of the devices used at home. Surely these are the batteries of the near future

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HISTORICAL DEVELOPMENTS

The idea of nuclear battery was introduced in the beginning of 1950, and was patented on

March 3rd, 1959 to tracer lab. Even though the idea was given more than 30 years before, no

significant progress was made on the subject because the yield was very less.

A radio isotope electric power system developed by inventor Paul Brown was a

scientific breakthrough in nuclear power. Brown’s first prototype power cell produced

100,000 times as much energy per gram of strontium -90(the energy source) than the most

powerful thermal battery yet in existence. The magnetic energy emitted by the alpha and beta

particles inherent in nuclear material. Alpha and beta particles are produced by the radioactive

decay of certain naturally occurring and man –made nuclear material (radio nuclides). The

electric charges of the alpha and beta particles have been captured and converted to electricity

for existing nuclear batteries, but the amount of power generated from such batteries has been

very small.

Alpha and beta particles also possess kinetic energy, by successive collisions of the

particles with air molecules or other molecules. The bulk of the R &D of nuclear batteries in

the past has been concerned with this heat energy which is readily observable and

measurable. The magnetic energy given off by alpha and beta particles is several orders of

magnitude greater than the kinetic energy or the direct electric energy produced by these same

particles. However, the myriads of tiny magnetic fields existing at any time cannot be

individually recognized or measured. This energy is not captured locally in nature to produce

heat or mechanical effects, but instead the energy escapes undetected.

Brown invented an approach to “organize” these magnetic fields so that the great

amounts of otherwise unobservable energy could be harnessed. The first cell constructed (that

melted the wire components) employed the most powerful source known, radium-226, as the

energy source.

The main drawback of Mr. Brown’s prototype was its low efficiency, and the reason for that

was when the radioactive material decays, many of the electrons lost from the semiconductor

material. With the enhancement of more regular pitting and introduction better fuels the

nu0clear batteries are thought to be the next generation batteries and there is hardly

ny doubt that these batteries will be available in stores within another decade.

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ENERGY PRODUCTION MECHANISM

Betavoltaics

Betavoltaics is an alternative energy technology that promises vastly extended

battery life and power density over current technologies. Betavoltaics are generators of

electrical current, in effect a form of a battery, which use energy from a radioactive source

emitting beta particles (electrons). The functioning of a betavoltaics device is somewhat

similar to a solar panel, which converts photons (light) into electric current.

Betavoltaic technique uses a silicon wafer to capture electrons emitted by a

radioactive gas, such as tritium. It is similar to the mechanics of converting sunlight into

electricity in a solar panel. The flat silicon wafer is coated with a diode material to create a

potential barrier. The radiation absorbed in the vicinity of and potential barrier like a p-n

junction or a metal-semiconductor contact would generate separate electron-hole pairs which

in turn flow in an electric circuit due to the voltaic effect. Of course, this occurs to a varying

degree in different materials and geometries.

A pictorial representation of a basic Betavoltaic conversion as shown in figure 1.

Electrode A (P-region) has a positive potential while electrode B (N-region) is negative with

the potential difference provided by me conventional means.

Figure 1

The junction between the two electrodes is comprised of a suitably ionisable

medium exposed to decay particles emitted from a radioactive source.

The energy conversion mechanism for this arrangement involves energy flow in

different.

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in equilibrium and no energy comes out of the system. We shall call this ground state E0. stages:

Stage 1:- Before the radioactive source is introduced, a difference in potential between to

electrodes is provided by a conventional means. An electric load RL is connected across the

electrodes A and B. Although a potential difference exists, no current flows through the load

RL because the electrical forces are

Stage 2:- Next, we introduce the radioactive source, say a beta emitter, to the system. Now,

the energy of the beta particle Eb generates electron- hole pair in the junction by imparting

kinetic energy which knocks electrons out of the neutral atoms. This amount of energy E1, is

known as the ionization potential of the junction.

Stage 3:- Further the beta particle imparts an amount of energy in excess of ionization

potential. This additional energy raises the electron energy to an elevated level E2. Of course

the beta [particle dose not impart its energy to a single ion pair, but a single beta particle will

generate as many as thousands of electron- hole pairs. The total number of ions per unit

volume of the junction is dependent upon the junction material.

Stage 4:- next, the electric field present in the junction acts on the ions and drives the

electrons into electrode A. the electrons collected in electrode A together with the electron

deficiency of electrode B establishes Fermi voltage between the electrodes. Naturally, the

electrons in electrode A seek to give up their energy and go back to their ground state (law of

entropy).

Stage 5:- the Fermi voltage derives electrons from the electrode A through the load where

they give up their energy in accordance with conventional electrical theory. A voltage drop

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occurs across the load as the electrons give an amount of energy E3. Then the amount of

energy available to be removed from the system is

E3= Eb - E1 – L1-L2

Where L1 is the converter loss and L2 is the loss in the electrical circuit.

Stage 6:- the electrons, after passing to the load have an amount of energy E4.from the load,

the electrons are then driven into the electrode B where it is allowed to recombine with a

junction ion, releasing the recombination energy E4 in the form of heat this completes the

circuit and the electron has returned to its original ground state.

The end result is that the radioactive source acts as a constant current generator. Then

the energy balance equation can be written as

E0=Eb –E1 –E3-L1-L2

Diagram of micro machined pn junction

Until now betavoltaics has been unable to match solar-cell efficiency. The reason is

simple: when the gas decays, its electrons shoot out in all directions. Many of them are lost. A

new Betavoltaic device using porous silicone diodes was proposed to increase their

efficiency. The flat silicon surface, where the electrons are captured and converted to a

current, and turned into a 3- dimensional surface by adding deep pits. Each pit is about 1

micron wide. That is four hundred-thousandths of an inch. They are more than 40 microns

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deep. When the radioactive gas occupies these pits, it creates the maximum opportunity for

harnessing the reaction.

Direct charging generators

1) High Q LC TANK circuit

In this type, the primary generator consists of a high –Q LC tank circuit. The energy imparted to radioactive decay products during the spontaneous disintegrations of radioactive material is utilized to sustain and amplify the oscillations in the high-Q LC tank circuit the circuit inductance comprises a coil wound on a core composed of radioactive nuclides connected in series with the primary winding of a power transformer. The core is fabricated from a mixture of three radioactive materials which decay primarily by alpha emission and provides a greater flux of radioactive decay products than the equivalent amount of single radioactive nuclei.

Figure 3 is a schematic diagram of an LC equivalent resonant circuit

Equitant circuit of the direct charging generator as shown in the figure 3.An LCR

circuit 1 is comprised of a capacitor 3, inductor file, transformer T primary winding 9 and

resistance 11 connected in series. It is assumed that the electrical conductors connecting the

various circuit elements and forming the inductor file and primary winding 9 are perfect

conductors; i.e., no DC resistance. Resistor 11 is a lump resistance equivalent to total DC

resistance of the actual circuit components and conductors. The inductor 5 is wound on a core

7 which is composed of a mixture of radioactive elements decaying primarily by alpha

particle emission.

When the current flows in electrical circuit, energy is dissipated or lost in the form of heat.

Thus, when oscillations are induced in an LCR circuit, the oscillations will gradually damp

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out due to the loss of energy in the circuit unless energy is continuously added to the circuit to

sustain the oscillations. In the LCR circuit shown in figure 3, a portion of the energy imparted

to the decay products such as alpha particles. During the radioactive decay of the materials

inductor core 7 is introduced into the circuit 1, when the decay products are absorbed by the

conductor which forms inductor 5. Once oscillations have been induced in the LCR circuit 1,

the energy absorbed by the inductor 5 form the radioactive decay of the core7 material will

sustain the oscillations as long as the amount of energy absorbed is equal to the amount of

energy dissipated in the ohmic resistance of the circuit 1.If the absorbed energy is greater than

the amount of energy lost through ohmic heating, the oscillations will be amplified. This

excess energy can be delivered to a load 17 connected across the transformer T secondary

winding 13.

The process involved in the conversion of the energy released by the spontaneous

disintegration of a radioactive material into electrical energy are numerous and complex.

Materials that are naturally radioactive, decay by the emission of either an alpha particle or a

beta particle and gamma rays may accompany either process. Radioactive materials that

decay primarily by alpha particle emission are preferred as inductor core 7 materials. Alpha

particles are emitted a very high speeds, in the order of 1.6*107 meters per second (m/s) and

consequently have very high kinetic energy. Alpha particles emitted in radium, for example,

decays are found to consist of two groups, those with a kinetic energy of 48.79*105 electron

volts (eV) and those having energy of 46.95*105 electron volts. This kinetic energy must be

dissipated when the alpha particles are absorbed by the conductor forming inductor 5. During

the absorption process, each alpha particle will collide with one or more atoms in the

conductor knocking electron from their orbits and imparting some kinetic energy to the

electrons. This results in increase number of conduction electrons in the conductor there by

increasing its conductivity.

Since the alpha particle is a positively charged ion, while the alpha particle is moving it

will have an associated magnetic field. When the alpha particle is stopped by the conductor,

the magnetic field will collapse thereby inducing a pulse of current in the conductor

producing a net increase in the current flowing in the circuit 1. Also, there will be additional

electrons stripped from orbit due to ionization reduced by the positively charged alpha

particles.

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Figure 4 is a wiring diagram of a constructed nuclear battery

Referring to figure 4, the nuclear battery is constructed in a cylindrical configuration.

Inductor 5 is constructed of copper wire wound in a single layer around the radioactive core

7. Decay products, such as alpha particles, are emitted radially outward from the core 7 as

indicated by arrows 2 to be absorbed by the copper conductor forming inductor 5. Eight

transformers are arranged in a circular pattern to form a cylinder concentric with and

surrounding inductor 5. The transformers have primary windings 9a-9h connected in series

which are then connected in series with inductor 5 and capacitor 3 to form an LCR circuit.

The central core 7, inductor5 and the eight transformers 15 are positioned within a cylindrical

shaped container 19. Copper wire is wound in a single layer on the outside wall and the inside

wall of cylinder 19 to form windings 23 and21 respectively. The transformers 15, secondary

windings 13a-13h and windings 21 and 23 are connected in series to output terminals 25 and

27. The configuration of inductor 5 is designed to ensure maximum eradication of the copper

conductor by the radioactive core source 7. The cylindrical configuration of the power

transformer ensures maximum transformer efficiency with minimum magnetic flux leakages.

2) SELF-RECIPROCATING CANTILEVER

This concept involves a more direct use of the charged particles produced by the decay of the radioactive source: the creation of a resonator by inducing movement due to attraction or repulsion resulting from the collection of charged particles. As the charge is collected, the deflection of a cantilever beam increases until it contacts a grounded element, thus discharging the beam and causing it to return to its original position. This process will repeat as long as the source is active. This concept has been tested experimentally with

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positive results. Figure 5 shows the experimental setup, in which the charges emitted from the source are collected in the beam toGenerate the electrostatic force that drives it. The radioactive source used was 63Ni with an activity of 1 mCi. The beam is 5 cm 5 mm, made from 60 m thick copper. A probe tip is glued to the beam to better detect and measure the movement of the beam. Both the source and the beam are mounted on a glass base for electrical insulation. The glass base is clamped so that the beamItself can only move by bending. The measuring scale is a silicon beam with 3m spaced gridlines so that the movement can be measured with a precision of 1.5m. A CCD camera connected to a VCR is used to record the movement of the beam and its periodicity. As the radioactive beta source decays, it emits electrons. The copper beam collects these electrons from the source, and the source itself would become positively charged since it keeps losing electrons; therefore, in the ideal case, there would be an electrostatic force applied on the beam that would bend it. However, in atmospheric conditions, no movement of the beam is observed, due to the ionization of the surrounding air. For that reason, the experiment has beenUnder vacuum (typically from 30 mTorr to 50 mTorr), where there is no extraneousIonization and the bending of the beam can be observed.

Self-reciprocating cantilever experimental set up

In order to understand the behavior of the system we have developed an analytical model for both the charge collection and deflection of the cantilever. The charge collecting process is govern

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Where dQ is the amount of charge collected by the beam during a given time dt, α represents the current emitted by the radioactive source, V is the voltage across the source and the beam and R is the effective resistance between them. The second term on the right hand side represents the current leakage arising from the ionization of the air. Since V = Q / C, where C is the capacitance of the beam and the source, the previous equation can be rearranged to obtain:

Shows a typical experimental result, in which the initial distance is 3.5 mm and theVacuum is 50 mTorr .

Deflection vs. time at a pressure of 50 mTorr

This equation can be readily solved:

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In Figure we observe that the beam bends very slowly. Therefore, the electrostatic force on the beam can be taken as balanced by the elastic force from the beam itself. Since the electrostatic force is proportional to Q2 and the distance between the beam and the source can be taken as a constant, being the deflection of the beam, we have:

K is the elastic constant of the beam, α can be assumed to be constant since 63Ni has a half life of more than 100 years, R in the experiment is also a constant because the pressure is maintained and no breakdown of the air happened, otherwise the beam will bounce back. C can also be assumed to be constant because it has been observed experimentally that the deflection of the beam is very small compared to the initial distance between the beam and

the radioactive source. Therefore:Figure compares the deflection measured experimentally with the values obtainedanalytically according to the discussion shown above, by fitting R. We observe a very good match between them.

Comparison between the experimental and analytical values for the deflection

This model, however, does not include the periodic behavior of this device. Current

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experiments show a minimum period of about 30 minutes, at which time the electrostatic energy is released as electric current. Further studies are being done in this area, trying to identify the key characteristics of the system in order to be able to design the device with the period and energy release level appropriate for each particular application.

3) Optoelectrics

An optoelectric nuclear battery has been proposed by researchers of the kurchatov institute

in Moscow. A beta emitter such as technetium-99 are strontium-90 is suspended in a gas or

liquid containing luminescent gas molecules of the exciter type, constituting “dust plasma”.

This permits a nearly lossless emission of beta electrons from the emitting dust particles for

excitation of the gases whose exciter line is selected for the conversion of the radioactivity

into a surrounding photovoltaic layer such that a comparably light weight low pressure, high

efficiency battery can be realized. These nuclides are low cost radioactive of nuclear power

reactors. The diameter of the dust particles is so small (few micrometers) that the electrons

from the beta decay leave the dust particles nearly without loss. The surrounding weakly

ionized plasma consists of gases or gas mixtures (e.g. krypton, argon, xenon) with exciter

lines, such that a considerable amount of the energy of the beta electrons is converted into this

light the surrounding walls contain photovoltaic layers with wide forbidden zones as egg.

Diamond which converts the optical energy generated from the radiation into electric energy.

The battery would consist of an exciter of argon, xenon, or krypton (or a mixture of two or three of them) in a pressure vessel with an internal mirrored surface, finely-ground radioisotope and an intermittent ultrasonic stirrer, illuminating photocell with a band gap .

tuned for the exciter. When the electrons of the beta active nuclides (e.g. krypton-85 or argon-

39) are excited, in the narrow exciter band at a minimum thermal losses, the radiations so

obtained is converted into electricity in a high band gap photovoltaic layer (e.g. in a p-n

diode) very efficiently the electric power per weight compared with existing radionuclide

batteries can then be increased by a factor 10 to 50 and more. If the pressure-vessel is carbon

fiber / epoxy the weight to power ratio is said to be comparable to an air breathing engine

with fuel tanks. The advantage of this design is that precision electrode assemblies are not

needed and most beta particles escape the finely-divided bulk material to contribute to the

batteries net power. The disadvantage consists in the high price of the radionuclide and in the

high pressure of up to 10MPa (100bar) and more for the gas that requires an expensive and

heavy container.

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FUEL CONSIDERATIONS

The major criterions considered in the selection of fuels are:

Avoidance of gamma in the decay chain

Half life

Particle range

Watch out for (alpha, n)reactions

Any radioisotope in the form of a solid that gives off alpha or beta particles can

be utilized in the nuclear battery. The first cell constructed (that melted the wire

components) employed the most powerful source known, radium-226, as the energy

source. However, radium-226 gives rise through decay to the daughter product

bismuth-214, which gives off strong gamma radiation that requires shielding for

safety. This adds a weight penalty in mobile applications.

Radium-226 is a naturally occurring isotope which is formed very slowly by the

decay of uranium-238. Radium-226 in equilibrium is present at about 1 gram per 3

million grams of uranium in the earths crust. Uranium mill wastes are readily

available source of radium-226 in very abundant quantities. Uranium mill wastes

contain far more energy in the radium-226 than is represented by the fission energy

derived form the produced uranium.

Strontium-90 gives off no gamma radiation so it does not necessitate the use of

thick lead shielding for safety.strrrontium-90 does not exist in nature, but it is one of

the several radioactive waste products resulting from nuclear fission. The utilizable

energy from strontium-90 substantially exceeds the energy derived from the nuclear

fission which gave rise to this isotope.

Once the present stores of nuclear wastes have been mined, the future supplies of strontium-90 will depend on the amount of nuclear electricity generated hence strontium-90 decay may ultimately become a premium fuel for such special uses as for perpetually powered wheel chairs and portable computers. Plutonium-238 dioxide is used for space application. Half life

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of tantalum-180m is about 1015 years. In its ground state, tantalum-180 (180Ta) is very unstable and decays to other nuclei in about

8 hours but its isomeric state, 180m Ta, is found in natural samples. Tantalum 180m hence

can be used for switchable nuclear batteries.

ISOTOPE SELECTION

A critical aspect of the creation of microbatteries for MEMS devices is the choice of the isotope to be used as a power source. Some requirements for this isotope include safety, reliability, cost, and activity. Since the size of the device is an issue in this particular application, gamma emitters have not been considered because they would require a substantial amount of shielding. Both pure alpha and low energy beta emitters have been used. The alpha emitters have an advantage due to the short range of the alpha particles. This short range allows increased efficiency andthus provides more design flexibility, assuming that a sufficient activity can be achieved. The halflife of the isotopes must be high enough so that the useful life of the battery is sufficient for typical applications, and low enough to provide sufficient activity. In addition, the new isotope resulting after decay should be stable, or it should decay without emitting gamma radiation. The isotopes currently in use for this work are

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To explore the viability of the nuclear micro battery concept, some scoping calculations need to be carried out. Using 210Po as an example, one can analyze the best case scenario, assuming that the nuclear battery is created using pure 210Po. In this case, the activity would be approximately 4,500 Ci per gram or 43,000 Ci per cubic centimeter. Thus, for a characteristic source volume of 10-5 cubic centimeters (0.1 cm x 0.1cm x 10 microns), one obtains approximately 0.5 Ci. Based on the results of previous experimental studies, the available power would be on the order of 0.5 mW (about 1 mW/Ci). The power required for MEMS devices canrange from Nano watts to microwatts. A typical case is that of a low power CMOS driven mechanical cantilever forming an air-gap capacitor with the substrate. Typical MEMS capacitors have 10 femtoFarad capacitance and resonant frequencies of 10s of kHz. The power dissipated for charging such an electromechanical capacitor would be in the range of 10 to 100 nanowatts. Therefore, a pure source provides more than sufficient activity to power a practical device

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INCORPORATION OF SOURCES INTO THE DEVICE

Three methods of incorporating radioactive material into the MEMS devices are being studied. These are 1) activation of layers within the MEMS device, 2) addition of liquid radioactive material into fabricated devices, and 3) addition of solid radioactive material into fabricated devices. In the first approach, the parent material for the radioactive daughter or granddaughter would be manufactured as part of the MEMS device, most likely near the surface of the device. After fabrication of the device, the parent material would be exposed to the radiation field in our TRIGAreactor for a period of time until the desired radiation source strength is achieved. Highly absorbing neutron or charged particle materials would be used to mask other components of the device which are to remain non-radioactive. In addition, the material used for the activation would be chosen such that it has a high activation cross-section, thus maximizing the activation of the “source” and minimizing competing activity produced in surrounding structures. In the second and third approaches, radioactive sources are introduced into the MEMS device after fabrication. In the case of a liquid source, a reservoir must be created within the device, along with a channel providing access to the reservoir. The reservoir can then be filled, relying on capillary action to create the flow, and the channel can then be sealed off if needed. In the case of a solid source, the radioactive material will have to be deposited in selected sites on the device. We currently have two approaches to create this type of sources:

Electroless plating is the plating of nickel without the use of electrodes but by chemical reduction [1]. Metallic nickel is produced by the chemical reduction of nickel solutions with hypophosphite using an autocatalytic bath. The plating metal can be deposited in the pure form on to the plated surfaces. The bath is an aqueous solution of nickel salt and contains relatively low concentration of hypophosphite. This type of nickel plating can be used on a large group of metals, such as steel, iron, platinum, silver, nickel, gold, copper, cobalt, palladium and aluminum. Throughout the plating process, the bath needs to be heated to maintain it at a temperature in the range of 90 – 100 °C to promote the chemical reduction reaction. The boiling temperature ofthe bath is to be avoided. At lower temperatures the reaction proceeds slowly and at higher temperatures the bath evaporates. The important factor influencing the plating process is the pH. The pH needs to be maintained at 4.5-6 for plating to occur. A lower pH results in no plating at all. We have successfully plated gold-coated silicon pieces of dimensions 2mm by 2mm, following this procedure. Plating of nickel on gold was observed in about 15 minutes. These solid sources can then be incorporated into a MEMS device.

“

We have obtained glass microspheres (25 to 53 μm in diameter) that will emit low energy 3H beta radiation. These are obtained by irradiating 6Li glass silicate non-radioactive microspheres in the UW Nuclear Reactor. Using this procedure, we can produce activities of up to 12.8 mCi per gram and per hour of irradiation. Then, these

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radioactive microspheres can be introduced in the MEMS device in the appropriate cavity. These latter approaches will allow for higher power densities than the direct reactor activation approach, but will provide less flexibility with respect to device design. We are currently exploring the tradeoffs of the different options, and will shortly release all the data needed to assess the viability of all of these approaches.

Waste Disposal

Our analysis proves that the environmental impact of disposing of these micro-devices once their useful life has ended, as well as the associated costs are minimal. Since after three half-lives the activity of the isotope has decayed to about 10% of the original activity, the micro-batteries would be below background radiation level at the following times:

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ADVANTAGES

The most important feat of nuclear cells is the life span they offer, a minimum of

10years! This is whopping when considered that it provides nonstop electric energy for the

seconds spanning these 10long years, which may simply mean that we keep our laptop or any

hand held devices switched-on for 10 years nonstop. Contrary to fears associated with

conventional batteries nuclear cells offers reliable electricity, without any drop in the yield or

potential during its entire operational period. Thus the longevity and reliability coupled

together would suffice the small factored energy needs for at least a couple of decades.

The largest concern of nuclear batteries comes from the fact that it involves the use of

radioactive materials. This means throughout the process of making a nuclear battery to final

disposal, all radiation protection standards must be met. Balancing the safety measures such

as shielding and regulation while still keeping the size and power advantages will determine

the economic feasibility of nuclear batteries. Safeties with respect to the containers are also

adequately taken care as the battery cases are hermetically sealed. Thus the risk of safety

hazards involving radioactive material stands reduced.

As the energy associated with fissile material is several times higher than conventional

sources, the cells are comparatively much lighter and thus facilitates high energy densities to

be achieved. Similarly, the efficiency of such cells is much higher simply because radioactive

materials in little waste generation. Thus substituting the future energy needs with nuclear

cells and replacing the already existing ones with these, the world can be seen transformed by

reducing the green house effects and associated risks. This should come as a handy savior for

almost all developed and developing nations. Moreover the nuclear produced therein are

substances that don’t occur naturally. For example strontium does not exist in nature but it is

one of the several radioactive waste products resulting from nuclear fission.

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DISADVANTAGES

First and foremost, as is the case with most breathtaking technologies, the high

initial cost of production involved is a drawback but as the product goes operational and gets

into bulk production, the price is sure to drop. The size of nuclear batteries for certain specific

applications may cause problems, but can be done away with as time goes by. For example,

size of Xcell used for laptop battery is much more than the conventional battery used in the

laptops.

Though radioactive materials sport high efficiency, the conversion methodologies

used presently are not much of any wonder and at the best matches’ conventional energy

sources. However, laboratory results have yielded much higher efficiencies, but are yet to be

released into the alpha stage.

A minor blow may come in the way of existing regional and country specific laws

regarding the use and disposal of radioactive materials. As these are not unique worldwide

and are subject to political horrors and ideology prevalent in the country. The introduction

legally requires these to be scrapped or amended. It can be however be hoped that, given the

revolutionary importance of this substance, things would come in favor gradually.

Above all, to gain social acceptance, a new technology must be beneficial and

demonstrate enough trouble free operation that people begin to see it as a “normal”

phenomenon. Nuclear energy began to loose this status following a series of major accidents

in its formative years. Acceptance accorded to nuclear power should be trust-based rather

than technology based. In other words acceptance might be related to public trust of the

organizations and individuals utilizing the technology as opposed to based on understanding

of the available evidence regarding the technology.

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APPLICATIONS

Nuclear batteries find many fold applications due to its long life time and improved reliability. In the ensuing era, the replacing of conventional chemical batteries will be of enormous advantages. This innovative technology will surely bring break-through in the current technology which was muddled up in the power limitations. MEMS devices, with their integrated nuclear micro-battery will be used in large variety of applications, as sensors, actuators, resonators, etc. It will be ensured that their use does not resultin any unsafe exposure to radiation.

Space applications

In space applications, nuclear power units offer advantages over solar cells, fuel cells

and ordinary batteries because of the following circumstances:

1. When the satellite orbits pass through radiation belts such as the van-Allen

belts around the Earth that could destroy the solar cells

2. Operations on the Moon or Mars where long periods of darkness require

heavy batteries to supply power when solar cells would not have access to

sunlight

3. Space missions in the opaque atmospheres such as Jupiter, where solar cells

would be useless because of lack of light.

4. At a distance far from the sun for long duration missions where fuel cells,

batteries and solar arrays would be too large and heavy.

5. Heating the electronics and storage batteries in the deep cold of space at minus

245° F is a necessity.

So in the future it is ensured that these nuclear batteries will replace all the existing

power supplies due to its incredible advantages over the other. The applications which require

a high power, a high life time, a compact design over the density, an atmospheric conditions-

independent it is quite a sure shot that future will be of ‘Nuclear Batteries’. NASA is on the

hot pursuit of harnessing this technology in space applications.

Medical Applications

The medical field finds a lot of applications with the nuclear battery due to their

increased longevity and better reliability. It would be suited for medical devices like

pacemakers, implanted deep fibrillations or other implanted devices that would otherwise

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require surgery to replace or repair the best out of the box is use in ‘cardiac pacemakers’.

Batteries used in implantable cardiac pace makers-present unique challenges to their

developers and manufacturers in terms of high levels of safety and reliability and it often

poses threat to the end-customer. In addition, the batteries must have longevity to avoid

frequent replacement. The technological advances in leads/electrodes have reduced energy

requirements by two orders of magnitude. Microelectronics advances sharply reduce internal

current drain, concurrently decreasing size and increasing functionality, reliability and

longevity. It is reported that about 600,000 pacemakers are implanted each year worldwide

and the total number of people with various types of implanted pacemaker has already

crossed 3,000,000. A cardiac pacemaker uses half of its battery power for cardiac stimulation

and the other half for housekeeping tasks such as monitoring and data logging. The first

implanted cardiac pacemaker used nickel-cadmium rechargeable battery, later on zinc-

mercury battery was developed and used which lasted for over two years. Lithium iodide

battery, developed in 1972 made the real impact to implantable cardiac pacemakers and is on

the way. But it draws the serious threat lasts for about ten years and this is a serious problem.

The life time solution is nuclear battery.

Nuclear batteries are the best reliable and it lasts lifetime. The definitions for some of

the important parts of the battery and its performances are parameters like voltage, duty cycle,

temperature, shelf life, service life, safety and reliability, internal resistance, specific energy

(watt-hour/ kg), specific power (watts/kg), and in all that means nuclear batteries stands out.

The technical advantages of nuclear batteries are in terms of its longevity, adaptable shapes

and sizes, corrosion resistance, minimum weight, excellent current drain that suits to cardiac

pacemakers.

Mobile devices

Xcell-N is a nuclear powered laptop battery that can provide between seven and

eight thousand times the life of a normal laptop battery-that is more than five year’s worth of

continuous power.

Nuclear batteries are about forgetting things around the usual charging, battery

replacing and such bottlenecks. Since chemical batteries are just near the end of their life, we

can’t expect much more from them, in its lowest accounts, a nuclear battery can endure at

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least up to five years. The Xcell-N is in continuous working for the last eight months and has

not been turned off and has never been plugged into electrical power since. Nuclear batteries

are going to replace the conventional batteries and adaptors, so the future will be of exciting

innovative new approach to powering portable devices.

Automobiles

Although it is on the initial stages of development, it is highly promised that the

nuclear batteries will find a sure niche in the automobiles replacing the weary conventional

iconic fuels there will be no case such as running out of fuel and running short of time. ‘Fox

valley auto association, USA’ already conducted many seminars on the scopes and they are

on the way of implementing this. Although the risks associated the usage of nuclear battery,

even concerned with legal restrictions are of many, but its advantages over the usual gasoline

fuels are overcoming all the obstacles.

Military applications

The army is undertaking a transformation into a more responsive, deployable, and

sustainable force, while maintaining high levels of lethality, survivability and versatility.

In unveiling this strategy, the final resource that fit quite beneficial is ‘nuclear battery’.

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“TRACE photonics, U.S. Army Armaments Research, Development and Engineering Centre”

has harnessed radioisotope power sources to provide very high energy density battery power

to the men in action. Nuclear batteries are much lighter than chemical batteries and will last

years, even decades. No power cords or transformers will be needed for the next generation of

microelectronics in which voltage-matched supplies are built into components. Safe, long-

life, reliable and stable temperature is available from the direct conversion of radioactive

decay energy to electricity. This distributed energy source is well suited to active radio

frequency equipment tags, sensors and ultra wide-band communication chips used on the

modern battlefield.

Underwater sea probes and sea sensors

The recent flare up of Tsunami, Earthquakes and other underwater destructive

phenomenon has increased the demand for sensors that keeps working for a long time and

able to withstand any crude situations. Since these batteries are geared towards applications

where power is needed in inaccessible places or under extreme conditions, the researchers

envision its use as deep-sea probes and sensors, sub-surface, coal mines and polar sensor

application s, with a focus on the oil industry.

And the next step is to adapt the technology for use in very tiny batteries that could

power micro-electro-mechanical-systems (MEMS) devices, such as those used in the optical

switches or the free floating “smart-dust” sensors being developed by the military.

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CONCLUSION

The world of tomorrow that science fiction dreams of and technology manifests might be a very small one. It would reason that small devices would need small batteries to power them. The use of power as heat and electricity from radioisotope will continue to be indispensable. As the technology grows, the need for more power and more heat will undoubtedly grow along with it.

. Clearly the current research of nuclear batteries shows promise in future applications

for sure. With implementation of this new technology credibility and feasibility of the device

will be heightened. The principal concern of nuclear batteries comes from the fact that it

involves the use of radioactive materials. This means throughout the process of making a

nuclear battery to final disposal, all radiation protection standards must be met. The economic

feasibility of the nuclear batteries will be determined by its applications and advantages. With

several features being added to this little wonder and other parallel laboratory works going

on, nuclear cells are going to be the next best thing ever invented in the human history

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REFERENCES

“Power from radioisotopes,” USAEC, Division of Technical Information

“Nuclear and radiochemistry” , Gerhardt Friedlander, Joseph.W.Kennedy and Julian

Malcolm Miller,

“Particles and Nuclei, an Introduction to the Physical Concepts”. B.Povh, K.Rith, C.

Scolz and F.Zetche.

Brown, Paul: "Resonant Nuclear Battery Supply", Raum & Zeit, 1(3) (August-

September, 1989

Powerstream.com, “The Role of Chemical Power Sources in Modern Health Care”,

Curtis F. Holmes

Powerpaper.com

Technologyreview.com

Wikipedia.com/atomic_battery

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