The development of the UK New Build Programme, intended to build 16 GW of new nuclear capacity by 2030 with at least 12 reactors at an estimated cost of £100 billion, is currently under way. However, the British nuclear industry faces a critical situation: the design of nuclear power plants is based on a 10,000 year return-period seismic event, for which moderate-to-strong (magnitude: 5.0-6.5) earthquakes have to be considered, while the database of British earthquakes is mainly composed of accelerograms recorded from small magnitude earthquakes (magnitude: 2.0-4.5). The use of such information, in prediction of the nature of larger earthquakes, can produce unreliable and unrealistic results.
Researchers at The University of Manchester have developed a stochastic ground motion accelerogram model for Northwest Europe – the first of its kind for the region. This model defines the earthquake input which allows seismic probabilistic risk analysis of structures such as nuclear power plants to be conducted. This study is based on the assumption that the nature of accelerograms (intensity, frequency content and time duration) of strong magnitude earthquakes in Britain would be similar to those of strong earthquakes that occur in the same Stable Continental Region (SCR) to which the UK belongs, namely Northwest Europe. This assumption avoids both the use of small-magnitude records to predict moderate-to-large accelerograms and the inclusion of earthquakes from other SCRs.
What is an accelerogram?
An accelerogram records the time history of the ground acceleration induced by an earthquake and reflects the magnitude and frequency components of the earthquake, which are also affected by the types of soil. Accelerograms provide a basis for seismic design of building structures.
- What challenges were faced by the researchers when developing a useable stochastic ground motion accelerogram model for the UK?
The scarcity of accelerograms in the UK has been widely reported in the literature. This is due to two facts: (i) strong earthquakes have rarely occurred and (ii) monitoring networks are not as developed as of those from active crustal regions. The developed model is applicable to Northwest Europe, including the UK.
- How could the new model be utilised within the structural engineering sector?
Before this model, seismic analyses in the UK were conducted using accelerograms from other regions far away from Britain. The new model uses data from neighbouring countries, which belong to the same stable continental regions, making them more realistic for structural engineering purposes.
- Are there any other sectors/industries which may also benefit from the model?
The model can also be used to define inputs for seismic risk analyses for mission-critical civil structures such as dams, large bridges, hospitals, power plants in general, military facilities, etc.