Lessons learned

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Concise descriptions of knowledge derived from experiences that can be communicated through mechanisms such as storytelling, debriefing etc., or summarized in databases.

Purpose and benefit

Lessons learned from a certain action or event or incident have the benefit to help define an action plan how to improve the action to be more effective and avoid failures or incidents in the future. They are often considered a key component of, and ongoing precursor to, effective risk management.


Lessons learned often reflect on ‘what was done right’, ‘what should be done differently’, 'what didn't work as expected and why', and ‘how to improve the process or action to be more effective in the future’. In the nuclear industry, operating experience feedback is an example of an applied lessons learned programme. In many cases the lessons learned report is the outcome of the after action review, but also other procedures can be used (informal discussions, personal interviews, consulting external experts, peer assists etc.).


Because of the large variety of nuclear organizations and of the large variety of events and actions that may occur in them, no universal form of the lessons learned report can be given.

However, in all cases it is advisable that the findings are recorded in a written form and inserted in the knowledge base of the organization.

The reports should contain not only the failures but also the successes of the evaluated action, together with all relevant information available. Also, all opinion of the involved staff members should be recorded and included in the lessons learned report, even if they are partly contradictory.

The report should contain also an action plan how to use the lessons learned to improve the performance.

Implementation guidelines

  • Get the findings in writing, and record all successes and failures together with all important parameters and circumstances.
  • Include all opinion of all involved staff members in the report, even if they seem to contradict. People at different positions may see the same event from different points of view.
  • Create also an action plan. The idea is to learn from the successes and failures not only to document them. The action plan is critical and should not be overlooked/disregarded, the action plan helps to ensure that learning and improvement takes place.
  • See also the Implementation part of the after action review.

Success factors

  • Make the lessons learned report concise and concentrate on the most important findings.
  • Make the lessons learned report available to those who might profit from it. This is especially important in the nuclear industry, where the operators of NPPs (and also other nuclear organizations) should learn from each-others operating experiences.
  • Implementing the action plan and a follow-up to ensure that the action(s) have been implemented is critical.
  • See also the Success factors part of the after action review.

Common pitfalls

  • The lessons learned report is not taken seriously. Either there is no occasion at all to capture the lessons learned from an action or event, or it will not be prepared well.
  • The lessons learned report does not contain all the relevant informations, since the capturing event was organized only at a much later time than the relevant process or event was finished, and some of the information have already been lost.
  • Not all aspects of the case is contained in the report, since not all opinions could be expressed. This can occur because either the time allocated for the discussion was not sufficient, or not all involved members of the team were invited to the discussion. In both cases the lessons learned report is superficial or biased and is of little use.
  • The lessons learned report does not reflect the true feelings and thoughts of the involved team members, since they were concerned to express their personal opinion honestly, because of the general blaming attitude of the management.
  • The lessons learned are not recorded in written form. Therefore they cannot be included in the knowledge base of the organization, and cannot be communicated to other possibly interested partners.
  • No action plan will be designed and included in the lessons learned report, to improve the performance in the future.
  • Although lessons learned are written down and stored, but they are not communicated, and they are not made available to possible interested partners or staff members.
  • See also the Common pitfalls part of the after action review.

Related articles

After action review


Best practice

Learning between projects

Peer assist