report provides more detailed knowlodge of nuclear battery

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A Seminar Report
On
NUCLEAR MICRO - BATTERY
Submitted by
UTKARSH KUMAR
in partial fulfilment for
Bachelor of Technology (B. Tech)
In
ELECTRONICS & INSTRUMENTATION
ENGINEERING
DEPARTMENT OF ELECTRONICS & INSTRUMENTATION
AJAY KUMAR GARG ENGINEERING COLLEGE
GHAZIABAD-201009
JANUARY 2016
P.O. Adhyatmik Nagar Adhyatmik Nagar, Hapur Bypass Rd, Bulandshahr Road
Industrial Area, Ghaziabad, Uttar Pradesh 201009

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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. UTKARSH KUMAR,
ROLL NO. 1302732037 our supervision in partial fulfilment of the
requirements for Bachelor of Technology in electronics and
instrumentation from Ajay Kumar Garg Engineering college,
Ghaziabad, for the year 2015-16.
SUBMITTED TO : SUBMITTED BY :
MR. NARESH KUMAR UTKARSH KUMAR
Dept. of electronics & Instrumentation
Seminar Co-coordinator
JANUARY 2016

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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 Electronics & Instrumentation” Department Of
E&I , AKGEC.
I am extremely thankful to Prof. P K Chopra, Head Of Department, Department of
Eletronics & Instrumentation, AKGEC for permitting me to undertake this work.
I express my heartfelt gratitude to my respected Seminar guide
Mr. Naresh Kumar 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.
Last but not least, I am thankful to my parents, who have encouraged & inspired
me in every possible way.

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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. One final concept relies on temperature gradients
produced by the sources, along with appropriate insulation, to create power using a Peltier
device. The source is isolated in order to allow it to reach sufficient temperatures, and the
temperature difference between the source and the rest of the device is exploited using the Peltier
effect. Performance results will be provided for each of these concepts.

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Table of Contents
Chapter Page no.
1.Introduction 6
2.MEMS 7
3.Historical Developments 10
4.Energy Production Mechanism 11
5.Junction type nuclear battery 14
6.Self-reciprocating cantilever 17
7.Isotope selection 21
8. Incorporation Of Source Into Device 22
9.Safety assessment 23
10.Advantages 24
11.Disadvantages 25
12.Applications 26
13.Conclusion 27
14.Reference 28

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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):
Microelectromechanical system is the technology of very small devices. It merges at the nano-
scale into nanoelectromechanical systems (NEMS) and nanotechnology.
In general it can be defined as miniaturized mechanical and electro-mechanical elements (i.e.,
devices and structures) that are made using the techniques of microfabrication. The critical
physical dimensions of MEMS devices can vary from well below one micron on the lower end
of the dimensional spectrum, all the way to several millimeters. MEMS technology is based on
a number of tools and methodologies, which are used to form small structures with dimensions
in the micrometer scale (one millionth of a meter). Significant parts of the technology have
been adopted from integrated circuit (IC) technology. For instance, almost all devices are built
on wafers of silicon, like ICs. The structures are realized in thin films of materials, like ICs.
They are patterned using photolithographic methods, like ICs.
While the functional elements of MEMS are miniaturized structures, sensors, actuators, and
microelectronics, the most notable (and perhaps most interesting) elements are the micro
sensors and micro actuators. Micro sensors and micro actuators are appropriately categorized as
“transducers”, which are defined as devices that convert energy from one form to another. In
the case of micro sensors, the device typically converts a measured mechanical signal into an
electrical signal.

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MEMS basic processes
Deposition processes
One of the basic building blocks in MEMS processing is the ability to deposit thin films of
material with a thickness anywhere between a few nanometres to about 100 micrometres. There
are two types of deposition processes, as follows:
Physical deposition-
Physical vapor deposition ("PVD") consists of a process in which a material is removed from a
target, and deposited on a surface. Techniques to do this include the process of sputtering, in
which an ion beam liberates atoms from a target, allowing them to move through the intervening
space and deposit on the desired substrate, and evaporation, in which a material is evaporated
from a target using either heat (thermal evaporation) or an electron beam (e-beam evaporation) in
a vacuum system.
Chemical deposition-
Chemical deposition techniques include chemical vapor deposition ("CVD"), in which a stream
of source gas reacts on the substrate to grow the material desired. Oxide films can also be grown
by the technique of thermal oxidation, in which the (typically silicon) wafer is exposed to oxygen
and/or steam, to grow a thin surface layer of silicon dioxide.
Patterning:
Patterning in MEMS is the transfer of a pattern into a material.
Lithography-
Lithography in MEMS context is typically the transfer of a pattern into a photosensitive material
by selective exposure to a radiation source such as light. A photosensitive material is a material
that experiences a change in its physical properties when exposed to a radiation source. If a
photosensitive material is selectively exposed to radiation (e.g. by masking some of the
radiation) the pattern of the radiation on the material is transferred to the material exposed, as the
properties of the exposed and unexposed regions differs.
Diamond patterning-.
Diamond patterning is a method of forming diamond MEMS.
Etching processes
There are two basic categories of etching processes: wet etching and dry etching. In the former,
the material is dissolved when immersed in a chemical solution. In the latter, the material is

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sputtered or dissolved using reactive ions or a vapor phase etchant.[9][10] for a somewhat dated
overview of MEMS etching technologies.
Dye preparation:
After preparing a large number of MEMS devices on a silicon wafer, individual dies have to be
separated, which is called die preparation in semiconductor technology. For some applications,
the separation is preceded by wafer back grinding in order to reduce the wafer thickness.

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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.

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

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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 occurs

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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

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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.
JUNCTION TYPE NUCLEAR BATTERY:
The electron-voltaic effects were studied extensively in the 1950’s and it was found that beta
particles with energies below 250 keV do not cause substantial damage in silicon [4][5].
Therefore, liquid 63Ni was selected as the radioactive source for these tests, since its maximum
and average energies (66.9 keV and 17.4 keV respectively) are well below the threshold energy
where damage is observed in silicon. In addition, its long half-life (100 year) makes it very
attractive for remote long-life applications, such as power of spacecraft instrumentation.
Figure 1: Diagram of a micromachined pn-junction
Since it is not easy to microfabricate solid radioactive materials (etching and cutting), a liquid
source is used instead for our micromachined pn-junction battery. As shown in Figure 1, a
number of bulk-etched channels have been micromachined in our pn-junction. Compared with
conventional planar pn-junctions, the three dimensional structure of our device allows for a
substantial increase of the junction area, and the micromachined channels can be used to store
the liquid source. Our pn-junction has 13 micromachined channels and the total junction area is
15.894 mm2 (about 55.82% more than the planar pn-junction). This can be very important since
the current generated by the powered pn-junction, whether it is powered by light or by a nuclear
source, is proportional to the junction area. Figure 2 shows the I-V curve of our pn-junction due
only to the interaction of light, as measured by a semiconductor parameter analyzer.

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Figure 3. I-V curve of a micromachined pn-junction powered by the light.
In order to measure the performance of our three-dimensional pn-junction in the presence of a
radioactive source, we use a pipette to place 8 µl of liquid 63Ni source (64 µCi) inside the
channels micromachined on top of the pn-junction, and then we cover it with a black box to
shield it from the light. The electric circuit used for these experiments is shown in Figure 3. We
obtain the I-V curve by varying the resistance R and using the ammeter to measure the current
for each resistance value. It is worth noting that the voltage across the pn-juntion is equal to the
voltage across the adjustable resistance, which is equal to the product of the resistance R and the
current flowing through I.
Figure 3: Electric circuit for experiments with micromachined pn-junction and 63Ni.
Figure 4 displays the I-V curves measured at 30 minutes, 2 hours and 16 hours after pouring the
radioactive source on the microchannels of the pn-junction. As expected, the degradation of the
pn-junction due to the 63Ni is very small. However, to conclusively demonstrate this extreme
would require a longer testing time, comparable to the expected life of the nuclear micro-battery.

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In Figure 4, we observe that the maximum current generated in the micromachined pn-junction
by the 63Ni source, i.e. the short circuit current, is 1.31 nA. In silicon, the generation of one
Electron-Hole Pair (EHP) requires about 3.2 eV, even though its energy gap between the
conduction band and covalence band is just 1.12 eV. So the theoretical maximum current
generated by 64µCi can be calculated as:
Imax = 64 µCi * (3.7*1010 dps) * (17.4 keV) / (3.2 eV) * (1.6*10-19 C) = 2.06*10-9 A = 2.06
nA
According to this estimate, the measured current value is 64.07% of the theoretical maximum
value. This illustrates the effectiveness of making the boron diffused depth around 40µm during
microfabrication, which is approximately the traveling distance of 63Ni beta particles in silicon.
Normal pn-junctions, which have ultra shallow junctions (less than 1µm), would result in very
low currents since most of the beta particles would stop in the p or in the n regions, instead of the
depletion region. On the other hand, the open circuit voltage is very small, only 53 mV. This is
partly due to the large p and n contact resistances. In this particular device, the metal used for the
p contact is gold and for the n contact is aluminum alloy, and both the p and n regions are all
covered by metal (the open circuit voltage for a normal junction-type battery is in the range of
0.2 to 0.5 V). A very effective way of increasing the open circuit voltage in a junction-type
battery is by reducing the contact area. The maximum power can be approximately estimated by:
Pmax = Is * Vo= 1.31 nA * 0.053 V = 0.069 nW
Further research on improving the device design and its performance is still on the way and will
be released in the near future.

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Figure 4: I-V curves for a micromachined pn-junction with 63Ni at different times.
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 5
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 × 5 mm, made from 60 µm 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 3µm
spaced gridlines so that the movement can be measured with a precision of 1.5µm. 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,

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due to the ionization of the surrounding air. For that reason, the experiment has been performed
under vacuum (typically from 30 mTorr to 50 mTorr), where there is no extraneous ionization
and the bending of the beam can be observed.
Figure 5: 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
governed by:
𝑑𝑄 = 𝛼𝑑𝑡 −
𝑉
𝑅
𝑑𝑡
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:
𝑑𝑄
𝑑𝑡
+
1
𝑅𝐶
𝑄 = 𝛼

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Figure 6 shows a typical experimental result, in which the initial distance is 3.5 mm and the
vacuum is 50 mTorr.
Figure 6: Deflection vs. time at a pressure of 50 mTorr
This equation can be readily solved:
𝑄 = 𝛼𝑅𝐶(1 − 𝑒−𝑡 𝑅𝐶⁄
)
In Figure 6 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 δ the deflection of the beam, we have:
𝑘𝛿 ∝ 𝛼2
𝑅2
𝐶2
(1− 𝑒−𝑡 𝑅𝐶⁄
)2
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:
𝛼 ∝ (1 − 𝑒−𝑡 𝑅𝐶⁄
)2

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Figure 7 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.
Figure 7: Comparison between the experimental and analytical values for the deflection.
This model, however, does not include the periodic behavior of this device. Current 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.
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 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:

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Table 1: Isotopes used for this work.
To explore the viability of the nuclear microbattery 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 can
range from nanowatts 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.
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 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

22. 22
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 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.
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
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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SAFETY ASSESSMENT
Since this work involves the use of small amounts of radiation and radioactive materials, it is
necessary to comply with current Radiation Protection Standards [2][3]. The potential health and
environmental effects of fabricating, using and disposing of these nuclear micro-batteries have
been studied in detail. Current radiation protection regulations are based on the Linear Non-
Threshold model (LNT), which assumes that any amount of radiation exposure, no matter how
small, may have negative health effects. This model was derived by extrapolating known acute
(high dose and high dose rate) exposure data points in a linear or curvilinear fashion through the
origin. Lately, however, there has been a movement among the Medical and Health Physics
communities encouraging the review of the current regulations by using the Non-Linear
Threshold model (NLT), that establishes that there are no detectable harmful health effects to
humans at radiation levels below 100 mSv (10 rem). Therefore, even though we will prove that
our devices do comply with current regulations, the actual health effects may be even more
insignificant.

24. 24
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.

25. 25
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.

26. 26
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.
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. Space missions in the opaque atmospheres such as Jupiter, where solar cells
would be useless because of lack of light.
3. 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.
4. Heating the electronics and storage batteries in the deep cold of space at minus
245° F is a necessity.
5. At a distance far from the sun for long duration missions where fuel cells,
batteries and solar arrays would be too large and heavy.
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.

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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.

28. 28
REFERENCES
 https://en.wikipedia.org/wiki/Microelectromechanical_systems
 https://www.mems-exchange.org/MEMS/processes/
 https://en.wikipedia.org/wiki/Nuclear_micro-battery
 " Standards For Protection Against Radiation". Title 10, Code of Federal Regulations,
Part 20, Nuclear Regulatory Commission, Washington, D.C. Continuosly updated.
(http://www.nrc.gov/NRC/CFR/PART020/).
 https://www.mems-exchange.org/MEMS/what-is.html
 P.Rappaport, and J.J.Loferski, “Thresholds for Electron Bombardment Induced Lattice
Displacements in Si and Ge,” Phys. Rev., Vol.100,p.1261,November,1955