CAPT JT Elder, USN
Commanding Officer NSWC Crane
Betavoltaics: An Innovative Power Source Enabling Next Generation Low-Power Sensor and Communication Devices
Tom Adams, PhD
August 25, 2015
Dr. Adam Razavian, SES Technical Director NSWC Crane
- Longevity of sensors & battery powered devices are severely limited by temperature, chemical instability and integrity issues associated with
- High risks & cost in replacing device or battery.
- Interfacing betavoltaics with electronics not well understood.
- Betavoltaic powered devices have not been demonstrated.
- Defense Science Board recommended the vigorous investment of $25M / year over 5 ARPA-e solicitation betavoltaic development.
- Power sensors & devices with betavoltaic battery hybrid source
- Ultra low power electronics
- Long-operating lifetimes (>20 years)
- Wide temperature range (-60°C to 150°C)
- Many uses of radioisotopes
- Smoke detectors, exit signs, watches, gun sights, space exploration, paint, . . .
- New capabilities & applications never imagined
- Mitigate risks to Warfighter
- Increased situational awareness
- Significant cost savings
- Meeting power budget
- Betavoltaic manufacturers
- Regulatory handling and licensing
- Obtaining NRMP and approved facility
- Defer risk to off-site NRC facility at Purdue University
- Domestic radioisotope inventory
- Power requirements specific to batteries
- Perception of radioisotopes
Theory of Operation
Similar to a solar cell
- Radiation source
- P-N junction
- Charge collectors
- Two modes of operation: constant current or constant voltage
- Maximum Power, Vm & Im, is the optimal point of operation
- As temperature increases, voltage and power decreases
- 1953: Paul Rappaport
- First to develop betavoltaics
- Sr90-Y90 radioactive beta sources
- 1968-1974: Larry Olsen
- Betacel Model 400
- 400 µW, 4% efficient, 0.025 mW/cm3
- Pm-147 source, 2.6 year half-life
- No degradation
- Successfully implanted pacemakers in over 285 patients, 60 in US
- Lithium batteries eventually cornered
- Present: Two manufacturers
- Peter Cabauy, City Labs
- Chris Thomas, Widetronix
Status of Betavoltaic Technology
- Widetronix (www.widetronix.com)
- Firefli, Tritium and Nickel-63 versions
- SiC semiconductor
- Voc =2.0V
- NRC specific license
- No performance data available
- City Labs (www.citylabs.net)
- III-V semiconductor
- Voc = 8V
- NRC general license
- Some performance data available
Beta Source Considerations
- Betas are emitted isotropically in a spectrum
- The average is 30% of maximum
- Peak shifted to lower energy due to drag from the attraction between the positively charged nucleus and negatively charged beta particle
- Bremsstrahlung radiation
- Beta energy greater than 300 keV can damage p-n junction
- Tritium, 300 nm optimal in titanium
- MC-SET (Monte Carlo Simulation of Electron Trajectories)
Radioisotope Availability and Selection
|Specific Density Ci/g||
Power in 1 Ci
Power, 10% efficiency
|Tritium||5.7 keV/β||9,664||12.3||0.0338 mW||0.0034 mW||$ 4||295,942||$1,183,768|
|Ni-63||17.1 keV/β||59.2||100.1||0.1014 mW||0.0101 mW||$ 4,000||98,647||$394,589,414|
|Pm-147||65.0 keV/β||600||2.6||0.3853 mW||0.0385 mW||$ 1,000||25,952||$25,951,842|
- Beta energy <300 keV to prevent semiconductor lattice damage
- Tritium (H-3), Available from Canada and Potential US supply from SRNL
- No gammas, low shielding requirements
- Stored as a solid in metallic film (TiT2 and ScT2) on foil substrate
- Nickel-63, Only available from Russia, but can be produced in HFIR at ORNL
- Low flux and high gammas due to impurities and other nickel radioisotopes
- NiCl or NiNO deposited on foil
- Promethium-147, Only available from Russia
- Byproduct of spent of nuclear fuel, does not occur naturally
- Some high energy gammas from other Pm radioisotopes
- Pm2O3 deposited on a titanium foil
Tritium Beta Emitting Source
- Tritium is the only pure beta emitting isotope
- Solid form as tritide is over 1000 times more concentrated than as a gas
- Current loading process is limited and lacks control
- Films tend to buckle and delaminate
- Tritium pressure limited to 2 bar on actual system
- Tritium concentrations vary film to film
- Experiment using hydrogen and new loading system
Hydrogen Loading System (HLS)
- Load materials with hydrogen with accurate control and high-resolution measurements
- Resistivity measurements during loading
Hybrid Betavoltaic Design
- Betavoltaic in parallel with Li-SS rechargeable battery or capacitor; e. betavoltaic trickle charges a battery
- Li-SS for low self-discharge
- Teflon, Tantalum polymer or aluminum polymer
- Electrical coupling
- Impedance on betavoltaics much higher
- Betavoltaic voltage follows a diode I-V curve
- Diode protection needed?
Low-Power Evaluation System
- System designed for betavoltaic, Li-SS battery, and hybrid battery evaluations
- Thermal Chamber
- Digital Multimeter with Multiplexer 40-Ch, Differential
- Source Measurement Unit
- LabView test control console
- Uninterruptible Power Source (UPS)
Individual performance versus temperature
Connected 6 betavoltaics in series
- Recently, US Government agencies have identified betavoltaics as a disruptive technology that is needed and should be
- Defense Science Board (DSB) issued its report on Technology and Innovation Enablers in 2030. Project driven by DARPA
- Advanced Research Projects Agency-Energy (ARPA-E) is wanting proposals for nuclear to electrical conversion in the form of betavoltaics
- Defense Threat Reduction Agency (DTRA)and others want to investigate using betavoltaics to provide early warning of corona mass ejection events (CMEs) to protect satellites and space applications,
- Using direct program support provides best chance of success for the technology and for the student
- Successful operation of a betavoltaic / Li-SS hybrid battery will allow for significant extended operational mission life of existing platforms, as well as facilitate development of innovative applications not yet conceived.
- Data acquired from betavoltaic development and evaluation represents a first and will provide designers and program managers with needed information to insert into
- Compliance with regulations is a requirement and issue that will be investigated.
- Public perception will change by technology demonstrations and education.
- Technology is advancing by both Application specific funding is needed to maintain this momentum.
- NSWC Crane
- Purdue University, School of Nuclear Engineering and Burton D. Morgan Center for Entrepreneurship
- City Labs, Inc
- Savanna River National Labs
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