To ensure safe operation of nuclear fuel, certain performance criteria must be met both during normal operation, anticipated operational occurrences and during postulated accidents. Zr Alloy material properties impact some of the most important performance criteria such as:
- Pellet Cladding Interaction (PCI) Pellet Cladding Mechanical Interaction (PCMI) corrosion and hydriding properties which in turn, are dependent upon:
» Chemical composition.
» Crystallographic texture and cladding microstructure.
» Cladding strength/ductility/fracture toughness.
- Re-opening of the pellet-cladding gap, lift-off, which is partly related to the fuel cladding creep properties.
- Excessive dimensional changes (resulting in e.g. excessive Fuel Assembly (FA) bowing) of fuel components that are a function of creep (including oxide induced and residual stress relaxation creep), irradiation growth, and hydrogen pickup in the components.
- Loss of Coolant Accident (LOCA) performance that is related to hydrogen pickup both during the base irradiation, before the LOCA event, as well as during the high temperature LOCA oxidation.
- Maintaining fuel integrity and fuel retrievability under normal dry storage and transportation conditions.
- Maintaining sub-criticality and shielding requirements under transportation accidents.
The Zr-alloy properties are a function of the reactor environment (fast neutron flux, temperature, water chemistry, etc.) and the Zr-alloy microstructure. The microstructure is a function of material chemistry and manufacturing process. A better knowledge of the impact of manufacturing changes on the Zr alloy microstructure and in-pile material properties can lead to improved capabilities to respond to current fuel performance issues and to ensure that any changes in the current manufacturing processes of the Zr alloys does not impair fuel’s safety performance criteria. The overall objective of this Special Topic Report (STR) is to provide this knowledge. Below is the report content list.
- Reactor characteristics,
- Fuel Design+ material used
3.1 Effects of Irradiation on coolant, oxide and Zr alloy
3.2 Microstructure in Zr alloys (texture, Kearns factors, etc.)
3.3 LWR Normal operation, AOO, DBA
3.3.1 Corrosion and HPU, Irradiation growth and creep,
3.3.3 Seismic event, LOCA and RIA
3.4 Interim Dry Storage- Main regulatory requirements related to dry storage
3.5 CANDUs pressure tubes operation conditions
- Zr source material manufacturing (VanArkel, Electrolytic process, Kroll)
4.1 Effects on Zr alloy performance during LOCA
- Ingot melting process
5.1 Effects on microstructure (chemical composition and impurities from ingot melting) and in-pile performance, DBA
- Cladding tube (fuel rods, including liner) guide tube manufacturing
6.1 Effects on microstructure and in-pile performance, DBA
- Effects of microstructure on dry storage
- Strip and sheet manufacturing
8.1 Effects on microstructure and in-pile performance
- CANDU pressure tube manufacturing and effects on in-pile performance