Glowing nuclear waste barrels in a high-tech facility, symbolizing thermal stability and radiation.

Is Your Nuclear Waste Safe? The Truth About Thermal Stability and Irradiation

Soraya Malik in Science & Nature August 2025 • 3 min read.

"Uncover the impacts of irradiation on the thermal stability of nuclear waste solutions and what it means for safety."

Managing spent nuclear fuel involves using organic extractants to separate valuable materials. However, these extractants, mixed with nitric acid and metal salts, can undergo oxidation, releasing gas and heat. This process can escalate into a thermal explosion under certain conditions, posing significant risks in reprocessing plants.

The safety of nuclear facilities depends on understanding how these extraction systems behave under various stresses. Both radiation and chemical reactions can degrade extractants, leading to potential fires and explosions. Historical incidents highlight the urgent need to study these factors.

Researchers have focused on how ionizing irradiation impacts the thermal stability of tri-n-butyl phosphate (TBP) solutions in Isopar-M, a common system in nuclear reprocessing. By understanding these effects, better safety measures can be developed.

Dynamics of Gas Evolution

Glowing nuclear waste barrels in a high-tech facility, symbolizing thermal stability and radiation.

Scientists investigated the dynamics of gas evolution during the thermal oxidation of TBP solutions. They examined 30% TBP solutions in Isopar-M saturated with varying concentrations of nitric acid (4.3, 8.2, and 12.0 mol/L) across a temperature range of 70°C to 150°C. Experiments were conducted in open vessels, measuring the volume of released gases to determine how pre-irradiation affects thermolysis and the accumulation of liquid degradation products.

The experiment used a linear electron accelerator to pre-irradiate TBP samples, mimicking conditions found in nuclear facilities. The setup included precise control and monitoring of temperature and gas release. This meticulous approach allowed the researchers to gather detailed data on the thermal behavior of the TBP solutions.

Key experimental parameters included:

Concentrations of nitric acid
Temperature range (70°C - 150°C)
Pre-irradiation doses (up to 1 MGy)
Measurement of gas evolution rates

The study revealed that the gas evolution process includes an initial induction period, followed by a phase of increasing gas release until it reaches a maximum rate. The team observed that the duration of the induction period and the maximum gas evolution rate are highly dependent on temperature and nitric acid concentration. Pre-irradiation significantly influenced these parameters, altering the thermal stability of the TBP solutions.

What This Means for Nuclear Safety

This research underscores the importance of understanding the effects of irradiation on nuclear waste management. By identifying the conditions that lead to increased gas evolution and reduced thermal stability, facilities can implement better safety protocols. Further studies can build on these findings, leading to more robust and secure nuclear reprocessing methods.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.1557/adv.2017.17, Alternate LINK

Title: The Effect Of Irradiation On The Thermal Stability Of Tbp Solutions In Isopar-M

Subject: Mechanical Engineering

Journal: MRS Advances

Publisher: Springer Science and Business Media LLC

Authors: E. V. Belova, Z. V. Dzhivanova, A. V. Smirnov, M. I. Kadyko, S. V. Stefanovsky

Published: 2017-01-12

Everything You Need To Know

What risks are associated with using organic extractants like tri-n-butyl phosphate (TBP) in Isopar-M during spent nuclear fuel reprocessing?

Spent nuclear fuel reprocessing utilizes organic extractants, such as tri-n-butyl phosphate (TBP) in Isopar-M, to separate valuable materials. However, these organic solutions, when combined with nitric acid and metal salts, can undergo oxidation. This process can release both gas and heat, which under specific circumstances, could lead to a thermal explosion. This poses considerable dangers within nuclear reprocessing plants if not managed correctly, requiring a deep understanding of thermal stability and the effects of irradiation.

What factors influence the thermal stability of tri-n-butyl phosphate (TBP) solutions in Isopar-M during nuclear reprocessing?

The thermal stability of tri-n-butyl phosphate (TBP) solutions in Isopar-M is influenced by the concentration of nitric acid, the temperature, and the radiation dose. Pre-irradiation of TBP solutions can alter their thermal stability, leading to changes in gas evolution rates and the induction period before rapid gas release. Higher nitric acid concentrations and temperatures generally accelerate gas evolution, while pre-irradiation can either accelerate or decelerate the process depending on the specific conditions.

How did researchers investigate the effects of pre-irradiation on tri-n-butyl phosphate (TBP) solutions in Isopar-M?

Researchers pre-irradiated tri-n-butyl phosphate (TBP) samples in Isopar-M using a linear electron accelerator to simulate conditions in nuclear facilities. They meticulously monitored the volume of released gases at different temperatures and nitric acid concentrations. Key parameters measured included the duration of the induction period before gas release and the maximum rate of gas evolution. This allowed them to assess how pre-irradiation impacts the thermal behavior and stability of the TBP solutions.

Why is it important to understand the impact of irradiation on the thermal stability of tri-n-butyl phosphate (TBP) solutions in Isopar-M within nuclear waste management?

Understanding the impact of irradiation on the thermal stability of tri-n-butyl phosphate (TBP) solutions in Isopar-M is critical because it directly affects the safety protocols and procedures in nuclear waste management. If conditions leading to increased gas evolution and reduced thermal stability are identified, facilities can implement measures to prevent thermal explosions and other hazardous events. This knowledge informs the development of more robust and secure nuclear reprocessing methods, mitigating risks associated with the handling and storage of spent nuclear fuel.

Besides gas evolution, what other factors related to the degradation of tri-n-butyl phosphate (TBP) solutions in Isopar-M should be considered for comprehensive nuclear safety assessments?

The research primarily focuses on gas evolution resulting from the thermal oxidation of tri-n-butyl phosphate (TBP) solutions in Isopar-M under irradiation. However, the broader impacts of the degradation products formed during irradiation, such as their influence on extraction efficiency, waste disposal, or long-term storage behavior, require further investigation. Understanding these factors is crucial for developing a comprehensive safety strategy for nuclear waste management and ensuring the sustainability of reprocessing operations.