Energy and the Physical Sciences:Beta-enhanced thermionic energy converters and nuclear batteries employing nanostructured diamond electrodes

The waste management and disposal of irradiated graphite from decommissioned Magnox and AGR reactors is a major challenge for the UK nuclear industry. It is estimated that irradiated graphite (~90,000 tonnes) from the UK's decommissioned reactors represents about one third of the current Intermediate Level Waste (ILW) inventory, a significant financial liability. This classification arises from the predicted carbon 14 concentration of irradiated graphite which equates to approximately 40% of the national carbon 14 inventory. The UK nuclear industry is not alone with this irradiated graphite waste management challenge5. It is currently estimated that the global inventory is of the order 250,000 tonnes; with significant quantities in France, Russia, USA and smaller amounts in Japan, Italy, Germany and Spain.
This proposal seeks to address this waste problem and provide a cost effective solution for its disposal; re-cycling the material as a feedstock for a novel type of thermionic energy converter, termed a Beta-enhanced Thermionic Diamond Converter (BTDC).
This proposal will investigate how beta radiation can be used to improve the operating performance of diamond electrode materials and seek to demonstrate a disruptive technology for producing renewable energy at a lower unit cost and with improved efficiency. Concentrated thermal energy can be harvested from numerous sources including Solar, Geothermal and Nuclear. This energy may be converted into electricity by a device called a thermionic energy converter. Such devices were under intensive development in the 1950s and 1960s as a means to power space craft and extract power from nuclear reactors. The performance of these devices was primarily constrained by the lack of a material electrode surface that could exhibit a stable low work function of less than 1 eV. This limited applications of the technology to those that could supply heat at temperatures exceeding 1200 centigrade. Lithiated nanodiamond offers a key part of a potential solution to this technological barrier. It possesses a very large negative electron affinity due to a unique functionalisation of the diamond surface. This surface has a number of beneficial properties including, chemical, temperature stability, high photoelectric yield and low work function. The novel properties of this lithiated diamond surface also make it attractive for applications in radiation detectors, high brightness electron sources, current amplifiers and ion sources. This proposal seeks to maximise the benefits of this diamond material in a thermionic converter: combining it with plasmonic nanostructures to absorb thermal energy, incorporating a beta radiation source to enhance the conversion of heat to thermionic energy.

The potential beneficiaries of the Beta-enhanced Thermionic Diamond Converter (BTDC) Materials Research are Power Utility Companies, UK Industry in high added value manufacture and European households provided with low cost combined heat and power in an expanding $38b* worldwide solar market (*SolarBuzz website 2011). Highly efficient absorber materials coupled with large Negative Electron Affinity [NEA] diamond surfaces have the potential to provide economic, grid parity solar power. The project objectives and deliverables also have wide and varied applications in science and manufacturing; e.g. low noise electron emission and amplification, miniature high performance dynodes and electronic displays.

We have secured a number of interested industrial beneficiaries for the project that bring in kind value to the project. as project partner Magnox Ltd, has agreed to provide expert representation on the project steering committee in addition to the provision of operational data and sample graphite material. We attribute an in-kind value of £65,600 for their involvment, which covers 7 full man days at £800 per day (standard industry rate) and a value of £60,000 for provision of sample materials and data (including paperwork and shipment costs). Other associated stakeholders agreeing to provide steering input are the Nuclear Decommissioning Authority (NDA) and SEA Ltd, a leading international systems and engineering house for development of space nuclear power. The latter have significant links with the European Space Agency (ESA) and bring significant added value with regards to identifying and cultivating commercial opportunities for our arising technology.
We will maximise the impact of our technology by partnering with key strategic stakeholders (Magnox, NDA and SEA Ltd) to capitalise on expertise available from industry whilst also cultivating opportunities for commercialisation and follow-on funding.
The business opportunity is multifaceted:
- A long life, scalable nuclear battery technology using beta-emitting graphite waste to power a TDC
- Solar thermal power generation, utility scale >100MW with distributed solar dish concentrators with EON driving the device requirements at the early development stage
- High added value, UK manufacture of BTDC devices and complete power systems, potential system integrator for maximum exploitation in solar thermal microgeneration
- Low cost licensing of BTDC to Lower Economic Developed Countries with potential to yield carbon reduction benefits many times that which the same investment could yield in the Europe; with low cost, locally manufactured thermionic renewable energy replacing diesel generators
To maximise impact in the solar market an important technology goal is to differentiate the TDC from the many competing solar pow