SCIP phases

First phase (2004-2009)

Phase one started in July 2004 and was completed in June 2009. It utilised the hot cell facilities and expertise available at the Swedish Studsvik establishment in order to assess material properties and determine conditions that can lead to fuel failures.

Second phase (2009-2014)

A second phase (SCIP-2) of this project started in July 2009 and was completed in June 2014. It was built on the considerable knowledge generated in the previous SCIP programme. The goal of the second phase was to generate high quality experimental data to improve the understanding of the dominant failure mechanisms for water reactor fuels and to devise means for reducing fuel failures. The major focus had been on cladding failures that are caused by pellet-cladding mechanical interaction, especially stress corrosion and hydrogen-assisted fracture mechanisms, as well as on the propagation of cladding cracks.

The scope and objectives of the programme were established following extensive discussions within the SCIP community, including a dedicated workshop in June 2013.

Third phase (2014-2019)

Based on the results of the 2013 workshop and the current needs and interests of the SCIP community, the continuation of the third phase (SCIP-3) of the project had the following objectives:

• Determined and quantified parameters affecting fuel fragmentation and dispersal in loss-of-coolant accident (LOCA) – The mechanism behind the fine fragmentation and fuel dispersal observed in LOCA tests with very high burn-up fuel were studied to determine and quantify the parametric thresholds of fuel fragmentation and dispersal. The investigation included the effects of parameters, such as fuel burn-up and microstructure, cladding strain, temperature, internal gas pressure and gas flow at the time of rupture and the importance of transient fission gas release.
• Analysed consequences of off-normal temperature transients – Transients leading to cladding overheating even without large cladding strain or failure still affects cladding material properties. Depending on the severity of the transient fuel, it may be affected to an extent that might challenge continued operation or normal waste handling, transport and storage. The objective of this part was to define criteria and assess overheated fuel rods for classifying them as undamaged or damaged. Damaged fuel rods would require non-standard handling, transport and storage procedures which might have a large economic impact for the concerned utility.
• Observed effects of axial load on cladding failure – Large axial dimensional changes are induced in fuel rods by the temperature occurring during a LOCA. Restricting axial contraction during quenching, e.g. by mechanical interaction with spacer grids, might impact the extent of cladding damage and fragmentation. The objective here was to determine the impact of axial load on cladding performance under LOCA conditions.
• Studied the impact of power ramp rates on PCI failure risk – SCIP-3 studied the mitigating effect of low ramp rates on PCI fuel failure risk and created the basis for eliminating unnecessary conservatism during plant operation.
• Supported model development and verification – SCIP-3 contributed to the mechanistic understanding of fuel fragmentation and dispersal phenomena and thus supported model development. Modelling was also used to support the set-up of experimental parameters. Modelling workshops were an integral part of the SCIP-3 programme.
• Knowledge transfer: Knowledge transfer was integrated into the programme, using renowned experts. Expert contributions were an integral part of the workshops and programme review group meetings.

SCIP-3 began in July 2014 and aimed to study LOCA and off-normal temperature transients from a safety and operational point of view. There was also be a smaller part related to pellet cladding interaction (PCI) failures. Modelling was an essential and integral part of the project. LOCA-related matters consumed about 70% of the budget, PCI made use of about 15% and modelling used up about 5% of the budget  The remaining 10% of the budget was not be allocated at the start of the program. That part of the budget was reserved to cover changes and/or extensions to the scope of work during the project.

In phase three, members from the entire nuclear community from many countries met to share understanding, experience and knowledge. Representatives from regulatory bodies, utilities, vendors and research organizations established a common understanding, enabling a shared view on safety matters, operational concerns and mechanisms of different phenomena, thus facilitating a safer and more economical production of nuclear electricity.

Fourth phase (2019-2024)

The continuation of the fourth phase (SCIP-4) of the project has the following objectives:

• generate high-quality experimental data to improve the understanding of the dominant failure mechanisms for water reactor fuels and devise means for reducing fuel failures
• achieve results of general applicability (i.e.not restricted to a particular fuel design, fabrication specification or operating condition)
• achieve experimental efficiency through the judicious use of a combination of experimental and theoretical techniques and approaches.

Related external link

Studsvik nuclear