nuclear microbattery seminar report

1

Roman family

NUCLEAR MICROBATTERIES

A SEMINAR REPORT

Submitted by

SUDHEESH.S Reg No:REAMEAE037

in partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGY

INAPPLIED ELECTRONICS AND INSTRUMENTATION

ENGINEERING

ROYAL COLLEGE OF ENGINEERING & TECHNOLOGYAKKIKKAVU.

UNIVERSITY OF CALICUTAPRIL 2016

ROYAL COLLEGE OF ENGINEERING &

TECHNOLOGY, AKKIKAVU

Department of Applied Electronics &Instrumentation Engineering

CERTIFICATE

This is to certify that the report entitled “NUCLEAR MICROBAT-TERIES ” submitted by SUDHEESH.S (REAMEAE037) to the Depart-ment of Applied Electronics & Instrumentation Engineering, Royal Collegeof Engineering & Technology, Akkikavu, in partial fulfillment of the re-quirements for the under graduation of Bachelor of Technology in AppliedElectronics and Instrumentation engineering from Calicut University, Thris-sur, Kerala is an authentic report of the seminar presented by him.

Guide Coordinator Head of the Department

Place:AkkikavuDate:

Acknowledgement

Every success stands as a testimony not only to the hardship but also to hearts behindit. Likewise, the present seminar work has been undertaken and completed with directand indirect help from many people and I would like to acknowledge the same.

First and foremost, I take immense pleasure in thanking the Management and respectedprincipal, Dr. B. Priestly Shan, for providing me with the wider facilities.

I express my sincere thanks to Prof. V. K. Sreehari, Head of Department of AppliedElectronics and Instrumentation Engineering for giving me opportunity to present thisseminar and for timely suggestions.

I wish to express my deep sense of gratitude to the seminar coordinators Ms.RemyaBharathy.K, Asst Professor, Department of Applied Electronics and InstrumentationEngineering and Ms.Nicy.V.B, Asst Professor, Department of Applied Electronics andInstrumentation Engineering, who coordinated in right path.

Words are inadequate in offering my thanks to Guide Ms.Remya Bharathy.K,Asst. Professor Department of Applied Electronics and Instrumentation Engineering, whocoordinated in right path.

Needless to mention that the teaching and the non-teaching faculty membershad been the source of inspiration and timely support in the conduct of my seminar. Iwould like to express my heartfelt thanks to my beloved parents for their blessings, myclassmates for their help and wishes for the successful completion of this seminar.

Above all I would like to thank the Almighty God for the blessings that helped meto complete the venture smoothly.

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Contents

Contents iv

Abstract vi

List of Figures vii

List of Tables viii

1 INTRODUCTION 1

2 HISTORICAL DEVELOPMENT 3

3 ENERGY PRODUCTION MECHANISM 53.1 Betavoltaics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 DIRECT CHARGING GENERATORS 94.1 LC Tank circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Self-reciprocating cantilever . . . . . . . . . . . . . . . . . . . . . . . . . . 124.3 Optoelectrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5 FUEL CONSIDERATIONS 18

6 ISOTOPE SELECTION 20

7 INCORPORATION OF SOURCES INTO THE DEVICE 227.1 Electrodeless plating of 63Ni . . . . . . . . . . . . . . . . . . . . . . . . . . 237.2 3H Microspheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

7.2.1 Waste Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

8 ADVANTAGES AND DISADVANTAGES 258.1 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258.2 Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

9 APPLICATIONS 289.1 Space applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

iv

CONTENTS v

9.2 Medical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299.3 Mobile devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309.4 Automobiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319.5 Military applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319.6 Underwater sea probes and sea sensors . . . . . . . . . . . . . . . . . . . . 32

10 CONCLUSION 33

Bibliography 34

Abstract

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 be considered to supply this needed power (solar, fossil fuels, etc), but nuclear

sources provide an intriguing option in terms of power density and lifetime. This report

describes several approaches for establishing the viability of nuclear sources for powering

realistic MEMS devices. Isotopes currently being used include low-energy beta emitters

(solid and liquid) and alpha emitters (solid). Several approaches are being explored for

the production of MEMS power sources. The first concept is a junction-type battery. In

this case, the charged particles emitted from the decay of the radioisotopes are absorbed

by a semiconductor and dissipate most of their energy as ionization of the atoms in the

solid. The carriers generated in this fashion are in excess of the number permitted by

thermodynamic equilibrium and, if they diffuse to the vicinity of a rectifying junction,

induce a voltage across the junction. 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.

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.

vi

List of Figures

3.1 Basic Beta voltaic conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.2 Ground state stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.3 Diagram of micro machined PN Junction . . . . . . . . . . . . . . . . . . . . . 8

4.1 L C Tank circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.2 Wiring diagram of constructed nuclar battery . . . . . . . . . . . . . . . . . . 12

4.3 Self-reciprocating cantilever experimental set up . . . . . . . . . . . . . . . . . 14

4.4 Deflection vs. time at a pressure of 50 mTorr . . . . . . . . . . . . . . . . . . 14

4.5 Comparison between the experimental and analytical values for the deflection 15

5.1 Fuel considerations of nuclear batteries compared to other batteries . . . . . . 19

vii

List of Tables

6.1 Radioisotope selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7.1 Time needed by different radioisotopes to decay under 10 percentage of their

local activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

viii

Chapter 1

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 radioiso-

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tope 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 inac-

cessible places or under extreme conditions.

Nuclear batteries harvest energy from radioactive specks and supply power to micro elec-

tromechanical 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.

Dept of AEIE - RCET Akkikavu 2

Chapter 2

HISTORICAL DEVELOPMENT

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

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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.


Chapter 3

ENERGY PRODUCTION

MECHANISM

3.1 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.

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A pictorial representation of a basic Betavoltaic conversion as shown in figure:3.1 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 3.1: Basic Beta voltaic conversion

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 mech-

anism for this arrangement involves energy flow in different, in equilibrium and no energy

comes out of the system. We shall call this ground state E0 stages:

Figure 3.2: Ground state 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 of the electrical force.

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

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



Figure 3.3: 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 deep. When the radioactive gas occupies these pits, it creates the maximum

opportunity for harnessing the reaction.


Chapter 4

DIRECT CHARGING

GENERATORS

4.1 LC Tank circuit

In this type, the primary generator consists of a LC tank circuit. The energy imparted

to radioactive decay products during the spontaneous disintegrations of radioactive ma-

terial is utilized to sustain and amplify the oscillations in the 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.

Equivalent circuit of the direct charging generator as shown in the figure 4.1. An LCR

circuit is comprised of a capacitor 3, inductor, 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

9


Figure 4.1: L C Tank circuit

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

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 4.1, 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 dis-

integration 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. Also, there will be additional electrons stripped from orbit due to ionization

reduced by the positively charged alpha particles.

Referring to figure 4.2, 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



Figure 4.2: Wiring diagram of constructed nuclar battery

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 and 21 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.

4.2 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 positive results. Figure 4.3 shows the experimental setup, in which

the charges emitted from the source are collected in the beam to generate the electrostatic

force that drives it. The radioactive source used was 63Ni with an activity of 1 mCi. The

beam is 5 cm to 5 m, made from 60 cm 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 beam itself can only move by bending. The measuring scale is a silicon beam with

30m spaced gridlines so that the movement can be measured with a precision of 1.5 cm.

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 been under vacuum (typically from 30 mTorr to

50 mTorr), where there is no extraneous ionization and the bending of the beam can be

observed.

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 by equation: |dQ = dt− (V/R)dt

Where dQ is the amount of charge collected by the beam during a given time dt,

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



Figure 4.3: Self-reciprocating cantilever experimental set up

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: dQ/dt+ (1/RC)Q = α

Figure 4.4: Deflection vs. time at a pressure of 50 mTorr

This equation can be readily solved:

Q = αRC(1− (e−t/RC))

In Figure 4.4 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:

Kδ ∝ α2R2C2(1− e( − t/RC)2)

K is the elastic constant of the beam, 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 4.5 compares the deflection measured

experimentally with the values obtained analytically according to the discussion shown

above, by fitting R. We observe a very good match between them.

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

Figure 4.5: Comparison between the experimental and analytical values for the deflection

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.

4.3 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 exist-



ing 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.


Chapter 5

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 uti-

lized 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

18


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 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.

Figure 5.1: Fuel considerations of nuclear batteries compared to other batteries


Chapter 6

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 appli-

cation, 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 and thus 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 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

20


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 can range 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.

Table 6.1: Radioisotope selection


Chapter 7

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 TRIGA reactor 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

22


activity produced in surrounding structures. In the second and third approaches, radioac-

tive 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:

7.1 Electrodeless plating of 63Ni

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 of the 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.



7.2 3H Microspheres

We have obtained glass microspheres (25 to 53 m in diameter) that will emit low en-

ergy 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 activ-

ities of up to 12.8 mCi per gram and per hour of irradiation. Then, these 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.

7.2.1 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 percent of the original

activity, the micro-batteries would be below background radiation level at the following

times:

Table 7.1: Time needed by different radioisotopes to decay under 10 percentage of theirlocal activity


Chapter 8

ADVANTAGES AND

DISADVANTAGES

8.1 Advantages

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

10years.This is whopping when considered that it provides non stop electric energy for the

seconds spanning these 10 long 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

25


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.

8.2 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. Nu-

clear 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.


Chapter 9

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 result in any

unsafe exposure to radiation.

9.1 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

28


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.

9.2 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

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.

9.3 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 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.

9.4 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.

9.5 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’.

“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.

9.6 Underwater sea probes and sea sensors

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

nomenon 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.


Chapter 10

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.

33

Bibliography

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TERY BASED ON SWNTS THIN FILM - SILICON HETROJUNCTION”, The In-

stitute of Electrical and Electronics Engineers(IEEE),(FEBRUARY 2012-MEMS con-

ference Paris), PP.1197-1200.

[2] H. Chen, L. Chiang ”Design optimisation of GaAs Betavoltaic Batteries”,The Institute

of Electrical and Electronics Engineers(IEEE), January-February 2011.

[3] Hang Guo, Hui Li, Amit Lal and James Blanchard ”Nuclear Microbatteries for Micro

and Nano Devices”, The Institute of Electrical and Electronics Engineers(IEEE),2008.

.

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nuclear microbattery seminar report

Education