Optimization of refueling outage work in pandemic times

Due to the pandemic caused by the SARS-CoV-2 coronavirus, on March 14th, 2020, Spain government declared the national state of alarm. However the beginning of the 27th refueling outage of Ascó unit 1 (1R27) was scheduled for April 18th, so the challenge ANAV was facing was clear: How to reconcile the pandemic and the conditions that it entails with the complexity of a refueling outage?

After delaying the start of the refueling outage by ten days, it was proposed to execute the outage with the tasks needed to guarantee the safe and reliable operation in the next cycle, reducing the potential viral load at the site, in order to minimize the infection risk, taking into account travel restrictions and always complying with the applicable regulations and regulatory commitments.


The task analysis was structured in several areas of interest, involving a large number of engineering, maintenance and work management technicians. The development of the work involved additional challenges, especially in terms of coordination, as, in those days prior to the refueling outage, many of the staff were teleworking full time from home.

  • For the in-service inspection activities, all inspections with a frequency of once in the period could be carried over to the next refueling outage, as the current period extended to 1R28.
  • Valve actuation tests and leakage tests could not be optimized due to regulatory requirements.
  • However, both the motor operated and air operated valves programs included more diagnostics than strictly necessary, so non-essential diagnostics were postponed.
  • In the life management programs, the required activities were postponed before the entry into long-term operation, as there was margin. Something similar could be done for design life programs.
  • Non-regulatory inspection programs could be rolled over to 1R28 almost in their entirety.
  • For the emergency diesel generators (EDGs), the maximum frequencies set in the maintenance program, the impact of a postponement on reliability and the previous as found condition were taken into account.
  • The activities associated with the turboshaft and its auxiliary systems were screened using similar criteria to those used for the EDGs, with a significant reduction in activities.
  • The treatment of the steam generators was quite complex, however, given the historical results and the applicable regulations, it was possible to justify postponing almost all the activities.
  • The entire preventive maintenance program for critical and non-critical equipment, thousands of work orders, was analyzed taking into account about twenty criteria, focusing on the trend of past results, the as found condition and the maintenance references described in EPRI documents.
  • In contrast, activities classified as corrective maintenance were not screened.
  • In terms of design modifications, regulatory commitments were maintained, as well as those required to increase plant reliability.
  • In the medium voltage motor program, the availability of supply and the actual condition of the equipment were analyzed.
  • Finally, all the activities aimed at closing anomalous conditions and temporary changes were executed.


Safety and reliability were prioritized in the 1R27 outage tasks screening, complying with all regulatory and normative requirements and taking into account the actual condition of the equipment (as found condition). As a result, 53% of the total number of work orders initially planned in 1R27 (5 727 tasks) could be postponed.

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