Nuclear Fuel Cycle and Materials

Advanced Nuclear Fuels and Fuel Cycles

Coordinated Research Project (CRP) on Reliability of Extended Burn up and Advanced PHWR Fuels (T12027)

There is increased interest among the Member States to introduce advanced fuels and extend the discharge burn up of fuel assemblies in PHWRs. Higher burn up and advanced fuels pose new challenges to fuel design, manufacturing techniques and may require new cladding materials. Fuel reliability issues include release of gaseous and volatile fission products, pellet-clad interaction, build-up of internal pressure, degradation of thermo-physical properties of fuel, stress corrosion cracking, etc. Attention is also required for the performance of fuels under off-normal and accident conditions. Similar issues have been addressed for LWR fuel and fuel assemblies. In most cases, PHWR conditions are different from LWR with respect to clad thickness, high linear power, high centre line temperature, absence of plenum volume, etc. which affect fuel performance. This CRP is intended to encourage the development and sharing of work on resolving these challenges.


Many advanced fuel cycles are under consideration for application in PHWR reactors. All of these fuel cycles involve higher burn-ups than those achieved with natural uranium. In order to achieve higher burn-ups, the fissile content of the fuel is increased compared to natural uranium and this may lead to higher power and consequently increases the defect probability unless the re-fuelling scheme is modified. .

Some of the Member States are working on SEU, REPU, thoria and MOX fuels for PHWRs. In India, fuel bundle assemblies using these materials were designed, fabricated using the materials available and loaded in commercial reactors. The Th bundles were loaded as a part of initial fuel charge for flux flattening for new units. The natural U- Pu MOX bundles and 0.9% SEU fuel bundles were loaded as lead assemblies in the operating units. Different MOX types were also loaded in Research reactors. In China, natural uranium equivalent assemblies made from REPU were loaded in commercial reactors as a first step. In Romania, experimental elements containing thorium and SEU were tested in a research reactor. Advanced fuels such as SEU, MOX, REPU and thoria were also tested in research reactors in Canada.

An application of an advanced cycle was performed in the Argentine Atucha-1 NPP where an increase of the U enrichment from natural uranium to Slightly Enriched Uranium with 0.85 % U-235 (SEU) allowed to increase the average burnup extraction of the fuel from 5900 MWd/tU to more than 11000 MWd/tU. The main consequence of this improvement is an important reduction of the fuel consumption and a positive impact on the reduction of the cost of generation.

CRP Overall Objectives
  1. Exchange of information and experience in the development of extended burn up and advanced fuels leading to their deployment in PHWRs.
  2. Scientific papers publication, presentations, final CRP report and TECDOC
Specific Research Objectives
  1. Exchange of information and experience in the development of extended burn up and advanced fuels leading to their deployment in PHWRs.
  2. Life limiting aspects of advanced fuels including Accident Tolerant Fuel
  3. Advanced fuels leading to improved Safety margins
The CRP findings will be consolidated in the form of Technical Document


Contact Point
Mr Uddaran Basak Phone: +43 2600 22771

About Coordinated Research Projects
For further information on CRPs, please see Coordinated Research Activites web page. To apply for a CRP, please use the forms here.

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