N15: Severe Accidents
This unit aims to:
- Contextualise severe accidents in the basic principles of a safety case and provide a history of how the field developed from the early Chicago Pile experiments.
- Establish a grounding in aspects of thermal-hydraulics, thermodynamics and material science that are relevant to severe accidents.
- Introduce the fields of fission product release mechanics, chemistry and aerosol physics.
- Provide an overview of the environmental consequences of a nuclear severe accident.
- Introduce some of the methods used in industrial analyses of severe accident transients.
- Provide an appreciation of the inherent uncertainties of a severe accident.
Brief description of the unit
This unit offers an introduction to nuclear severe accidents for light water reactors. The course begins by introducing basic safety principles and the history of severe accidents before providing a grounding in thermal-hydraulics and thermodynamics that will be relevant to understanding severe accident phenomenology. The physics and chemistry of a typical severe accident transient is then covered in detail following a chronological order, which extends from a core uncovery event, clad oxidation, core melt down to the breach of the Reactor Pressure Vessel. Ex-vessel severe accident phenomena are also covered in the course, which extends to environmental consequences. The unit will also include an overview of some of the tools and codes available and widely used within the nuclear sector and will enable the student to join industry with a solid background in severe accident phenomenology and safety approach.
Intended Learning Outcomes
| Apply concepts in fission product chemistry and aerosol physics to qualitatively assess radiological impact |
| Assess plant and fuel conditions to determine most credible direction for the transient |
| Compare and contrast positive and negative aspects of severe accident phenomena in terms of the credible risks outcomes |
| Describe the in-vessel phenomenology leading from accident initiation to total core melt-down, and the sequence of events |
| Critique severe accidents modelling approaches, recognising the need for simplicity, adequacy and appropriate validation. |
| Describe in detail an historical severe accident, reflecting on the lessons learnt for the nuclear industry and in the wider society |
| Describe the ex-vessel phenomenology leading RPV to the loss of radionuclides from the containment |
| Apply fundamental concepts of thermodynamics and thermal-hydraulics to explain the severe accident phenomenology so as too deduce likely diagnostics and prognoses |
| Apply fundamental concepts in metallurgy and material science in order to interpret phase diagrams to determine the behaviour of molten metals and oxides |
| Describe the fundamental safety principles of the nuclear industry and their context when applied to severe accident conditions |
| Solve practical problems through calculation and / or deduction in order to estimate or bound plant responses or consequences |
| Describe radionuclide dispersion phenomena in the environment and apply this knowledge to determine a breadth of radiological consequences and ethical considerations |