Image above. Underground tunnel to nuclear repository laboratory.
Photo credit: SKB

Every year, global climate change becomes more pressing. Unlike coal-fueled power plants, nuclear power emits few greenhouse gases and could help counter the effects of global climate change. Nuclear waste disposal is the Achilles heel of the nuclear industry, however. Since 1954, over 70 nuclear power plants across 35 states have contributed to the growing pile of spent nuclear fuel in temporary storage facilities throughout the country. Combined with defense-related spent fuel, this pile amounts to about 70,000 tons of material.

The primary concern amongst experts and the public is where to put this waste.  But, climate change itself is a new factor in the waste storage dilemma. Unpredictable climatic activity suggests that the very problem that nuclear energy might help us reduce or resolve could complicate long-term waste storage.

If we continue to increase our reliance on nuclear power, we must prioritize safe disposal of spent fuel, not interim, short-term surface storage. Permanent underground storage facilities — what the industry refers to as geological repositories — may provide safer storage options, so long as the lasting effects of climate change on the landscape and water storage can be accounted for in the design.

These proposed geological repositories, are located half a mile underground in stable bedrock and are designed to last the lifetime of the nuclear waste, which for plutonium and uranium fuel end products are 24,000 years and 700 million years, respectively. Compared to many current temporary storage facilities near rivers or lakes and in highly populated areas, these engineered secure vaults would reduce the potential harm to the surrounding environment.

How do we know these facilities will be safe? New research suggests that climate is a new complicating factor in answering these already difficult questions.

Daunting timescales and unpredictability have always posed a challenge for waste engineers. Computer modeling can help test the performance standards and risks of proposed nuclear storage facilities. Will the encasement materials last long enough? Can natural systems provide safe barriers for nuclear waste? How could additional factors compromise the effectiveness of repository design? Nuclear engineers must answer these questions before completing their design.

Researchers at Svensk Karnbranslehantering AB (SKB), the nuclear waste management company for all of Sweden’s nuclear waste, recently proposed a geological repository in Sweden’s crystalline bedrock as the safest option for the country’s spent nuclear fuel. Before moving forward, they must ensure this plan will protect Sweden’s environmental and human health. What SKB’s new testing approach introduces, is the importance of considering the effects of climate change in risk assessment models.

The exact outcome of climate change cannot be predicted. However, the details of different climate scenarios can be hypothesized and accounted for in nuclear waste repository design. According to their results, the unpredictable effects of climate change requires nuclear engineers to account for such conditions as a wider range of temperatures, precipitation, and other environmental conditions that can affect factors half a mile underground when designing permanent nuclear waste repositories.

Starting with geological historical data, they changed one weather variable at a time to predict different outcomes. Raising the temperature would create a warmer and wetter climate with greater sea level rise. Over time, more ice sheet cover would increase ground water from glacier melt. If temperatures fell without insulation from ice formation, the soil would freeze at deeper levels. These varying possible outcomes require nuclear engineers to prepare for a wider range of outcomes.

United States regulators and waste engineers continue to develop long-term waste storage plans.  Construction of the controversial Yucca Mountain depository in Nevada was shut down when evidence suggested the radioactive waste could contaminate ground water. Currently, the Waste Isolation Pilot Plant (WIPP) in New Mexico is the most viable solution. This facility is deep underground, similar to those in Sweden, located below salt deposits that stabilize the waste within its crystalline structure. To assess the potential risk of future contamination, researchers at WIPP and other geological repository locations throughout the world, should consider climate change in their risk assessment models.

Näslund, Jens-Ove, et. Al. “Climate Considerations in Long-Term Safety Assessments for Nuclear Waste Repositories” The Royal Swedish Academy of Sciences (2013).  21

http://link.springer.com/article/10.1007/s13280-013-0406-6