Looking Deep Into the Future for Nuclear Waste Repositories

Research Area:

Waste and Fuel Management

PI:

Dr Natalie Lord

Funders:

Posiva Oy, SKB

Contact details:

Natalie.Lord@bristol.ac.uk

Project website:

https://southwestnuclearhub.ac.uk/2017/12/04/looking-deep-into-the-future-for-radioactive-waste-disposal/

The Challenge

Researchers in Geographical Sciences at University of Bristol have looked deep into the future with their Earth system models to assess the state of the globe over the course of the next million years. When might the next ice age occur? What impact would this have on a high-latitude waste repository site? Such work is critical for the post-closure performance assessment for radioactive waste repositories.

The Solution

The impact of future CO2 emissions was investigated using an Earth system model of intermediate complexity (Figure 1), and the potential implications for nuclear waste disposal considered. A statistical emulator was developed, based on a large ensemble of future climate simulations carried out using a state-of-the-art atmosphere-ocean general circulation model.

Figure 1 - Atmospheric CO2 concentration for the next million years for CO2 scenarios with pulse emissions of 1000–20,000 Pg C (Lord et al., 2016).

The emulator can be used to rapidly project the future climate resulting from any combination of orbital and CO2 parameter values, and thus allows the ‘continuous’ evolution of global climate over hundreds of thousands of years to be modelled.

Due to the high resolution of the climate model (2.5o latitude x 3.75o longitude), climate changes for individual grid boxes can be projected, at a surface resolution of, for example, 295 x 278 km at 45o latitude (Figure 2). Downscaling techniques can then be applied to the climate data in order to increase its resolution to spatial scales of about 5-10 km.

Figure 2 - Emulation of surface air temperature for the next 200,000 years. a) Timeseries of orbital variations (Laskar et al., 2004), showing eccentricity (black) and precession (radians, blue) on the left axis, and obliquity (degrees, red) on the right axis. b) Time series of emulated grid box mean annual surface air temperature (oC), modelled every 1 kyr, for four CO2 emissions scenarios; 500 Pg C (black), 1000 Pg C (green), 2000 Pg C (red) and 5000 Pg C (blue).

The Impact

Further work, currently underway, includes: a commissioned review for National Cooperative for the Disposal of Radioactive Waste (Nagra) on long-term past and future climate modelling to consider geological evolution at timescales pertinent for waste repositories; (2) A combination of Earth system modelling efforts focussing on the Finnish and Swedish disposal sites of Olkiluoto and Forsmark (funded by Posiva Oy and the SKB).

 

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