For all sources of radioactivity, radiological risk assessments are essential for safeguarding human and environmental health. But assessments often have to rely upon simplistic assumptions, such as the use of simple ratios in risk calculations which combine many processes. This pragmatic approach has largely arisen due to the lack of scientific knowledge and/or data in key areas. The resultant uncertainty has been taken into account through conservative approaches to radiological risk assessment which may tend to overestimate risk. Uncertainty arises at all stages of the assessment process from the estimation of transfer to human foodstuffs and wildlife, exposure and risk. Reducing uncertainty is important as it relates directly to scientific credibility, which will always be open to challenge given the highly sensitive nature of radiological risk assessment in society. We propose an integrated, multi-disciplinary, programme to assess and reduce the uncertainty associated with radiological risk assessment to protect human health and the environment. At the same time we will contribute to building the capacity needed to ensure that the UK rebuilds and maintains expertise in environmental radioactivity into the future. Our project has four major and highly inter-related components to address the key goal of RATE to rebuild UK capacity and make a major contribution to enhancing environmental protection and safeguarding human health. The first component will study how the biological availability of radionuclides varies in soils over time. We will investigate if short-term measurements (collected in three year controlled experiments) can be used to predict the long-term availability of radionuclides in soils by testing our models in the Chernobyl exclusion zone. The second component will apply the concepts of 'phylogeny' and 'ionomics' to characterise radionuclide uptake by plants and other organisms. These approaches, and statistical modelling methods, are increasingly applied to describe uptake of a range of elements in plant nutrition, and we are pioneering their use for studying radionuclide uptake in other organisms and human foods. A particularly exciting aspect of the approach is the possibility to make predictions for any plant or animal. This is of great value as it is impossible to measure uptake for all wildlife, crops and farm animals. The third component of the work will extend our efforts to improve the quantification of radiation exposure and understanding of resultant biological effects by investigating the underlying mechanisms involved. A key aim is to see whether what we know from experiments on animals and plants in the laboratory is a good representation of what happens in the real world: some scientists believe that animals in the natural environment are more susceptible to radiation than laboratory animals: we need to test this to have confidence in our risk assessments. Together these studies will enable us to reduce and better quantify the uncertainties associated with radiological risk assessment. By training a cohort of PDRA and PhDs our fourth component will help to renew UK capacity in environmental radioactivity by providing trained, experienced researchers who are well networked within the UK and internationally through the contacts of the investigators. Our students will be trained in a wide range of essential skills through their controlled laboratory studies and working in contaminated environments. They will benefit from being a member of a multidisciplinary team and opportunities to take placements with our beneficiaries and extensive range of project partners. The outputs of the project will benefit governmental and non-governmental organisations with responsibility for assessing the risks to humans and wildlife posed by environmental radioactivity. It will also make a major contribution to improved scientific and public confidence in the outcomes of environmental safety assessments.

Seismic hazard assessment and understanding of continental deformation are hindered by unexplained slip-rate fluctuations on faults, associated with (a) temporal clusters of damaging earthquakes lasting 100s to 1000s of years, and (b) longer-term fault quiescence lasting tens to hundreds of millennia. We propose a new unified hypothesis explaining both (a) and (b), involving stress interactions between fault/shear-zones and neighbouring fault/shear-zones; however key data to test this are lacking. We propose measurements and modelling to test our hypothesis, which have the potential to quantify the processes that control continental faulting and fluctuations in the rates of expected earthquake occurrence, with high societal impact. Our aspiration is that cities and critical facilities worldwide will gain additional protection from seismic hazard through use of the calculations we pioneer herein. The background is that slip-rate fluctuations hinder understanding because they introduce uncertainty about whether specific faults are active or not. For example, a review in Japan of earthquake risk to critical facilities, such as the Tsuruga nuclear power plant (NPP), revealed a geological fault under a nuclear reactor (Chapman et al. 2014). The question that arose was whether the fault was active or not. Japan's Nuclear Regulatory Authority (NRA) has guidelines defining fault activity, and considered the fault under the reactor to be active, evidenced by faulting in sediments <~125,000 years in age. The Japan Atomic Energy Power Company (JPAC) disagreed, following study by an independent team of geoscientists. In 2014, the Tsuruga NPP remained closed due to ongoing debate between the NRA and JPAC, with similar debates ongoing for other NPPs. We suggest that defining fault activity as simply "active" or "inactive" is unsatisfactory because it is debatable even amongst experts. In fact a fault that has not slipped in many millennia may, in reality, not be inactive, but instead may simply have a low slip-rate, with the capability to host a damaging earthquake after a long recurrence interval. Our breakthrough is we think slip-rate fluctuations over both timescales (a and b) are a continuum, sharing a common cause involving interaction between fault/shear-zones. For the first time, we provide calculations that describe this interaction, quantifying slip-rate fluctuations and seismic hazard in terms of probabilities. We show that slip during an earthquake cluster on a brittle fault in the upper crust occurs in tandem with high strain-rate on the viscous shear-zone underlying the fault. This deformation of the crust produces changes in differential stress on neighbouring fault/shear-zones. Viscous strain-rate is known to be proportional to differential stress, so, given data on slip-rate fluctuations one can calculate changes in differential stress, and then calculate implied changes to viscous strain-rates on receiver shear zones and slip-rates on their overlying brittle faults. We provide a quantified example covering several millennia, but lack data allowing a test over tens to hundreds of millennia. If we can verify our hypothesis over both timescales, through successful replication of measurements via modelling, we will have identified and quantified a hitherto unknown fundamental geological process. We will study the Athens region, Greece, where a special set of geological attributes allows us to measure and model slip-rate fluctuation over both time scales (a and b), the key data combination never achieved to date. We know of no other quantified explanation that links slip-rate fluctuations over the two timescales; the significance and impact of accomplishing this is that it has the potential to change the way we mitigate hazard for cities and critical facilities. Chapman et al. 2014, Active faults and nuclear power plants, EOS, 95, 4