An increasing number of countries are looking into the long-term operation of their nuclear power plants – extending their lifetime beyond what they had originally been designed for three or four decades ago. To support operators and regulators in the safe extension of the useful life of power plants, the IAEA offers a safety review service known as SALTO — Safety Aspects of Long Term Operation. With two thirds of nuclear power reactors in the world over 30 years of age, it is one of the most frequently requested review services of the IAEA.
SALTO, launched in 2005, consists of workshops and SALTO review missions complemented with support missions at nuclear power plants in preparation for the review. The evaluation of programmes and performance is made on the basis of the IAEA’s Safety Standards and other guidance documents. Ultimately, executive summaries of all SALTO missions are made available via the IAEA’s website.
Qinshan Unit 1 in China – An example
Unit 1 of Qinshan, China’s oldest nuclear power reactor, started operation in 1991 and will in 2021 reach its original design lifetime of 30 years. The operator, China National Nuclear Power Co., would like to extend its lifespan by 20 years. The operator therefore requested a SALTO review, and a mission to Qinshan took place in 2017, with a follow-up review mission in 2019.
“The IAEA Safety Standards recommend periodic safety reviews that are more comprehensive than what we had originally planned; we have adjusted this in line with the recommendations,” said Tao Jun, head of the Technical Support Department at the Qinshan Nuclear Power Plant, China’s biggest. “We are also improving the ageing management programmes to cover the entire period of the life extension.”
Safety officers and engineers at Qinshan Unit 1 have acted on all the 15 suggestions and recommendations made by the IAEA SALTO mission review team in 2017. While safety and licensing of nuclear power plants are a national responsibility, input from the SALTO mission have been helpful in further strengthening safety and strengthening the application for the lifetime extension, Jun explained.
The IAEA supported the team in Qinshan through a series of workshops and support missions that helped them put into place some of the recommendations. “The workshop on time-limited ageing analysis was particularly useful for us,” Jun said. “It is important to predict and analyse ageing in detail in the interest of safety, which is our priority.”
Qinshan is not alone. As of April 2020, 45 SALTO missions had been conducted at 21 nuclear power plants in 17 countries, with 11 SALTO follow-up missions conducted to review how the mission results have been addressed. Mission teams, led by the IAEA, are made up of senior experts from peer organizations. SALTO mission results have been summarized for the period 2005-2015 and 2015-2018 to enable operators worldwide to learn from these reviews.
Since 2007, the IAEA has significantly enhanced the methodology of the review service, trained a large pool of expert reviewers, performed many workshops related to ageing management and long-term operations and provided advisory support missions. The related IAEA Safety Standards have also been improved using lessons learned as well as experience gained from these reviews.
“We strive for continuous improvement: At the end of each mission, the team members complete a questionnaire on the SALTO peer review process and provide improvement proposals,” said Peter Tarren, Head of the Operational Safety Section at the IAEA. “Feedback is also collected from the hosts and from regular IAEA technical meetings with industry experts, who also provide suggestions and recommendations.”
From nuclear power plants to research reactors
Following the request from several countries, the IAEA is now expanding the scope of SALTO missions to also include research reactors, about 70% of which have operated for over 30 years. The IAEA has adapted the SALTO methodology to research reactors considering the specificities of these facilities.
“As most research reactors components can be refurbished and modernized without major difficulty, the service life of these reactors can be extended as long as they conform to the up-to-date safety requirements. SALTO is the most recent IAEA service to help Member States in achieving this goal,” said Amgad Shokr, Head of the IAEA’s Research Reactor Safety Section. “Following the success of the first such SALTO mission at the BR2 research reactor, Belgium in November 2017, other countries have already expressed interest in inviting SALTO. The next mission is planned for October 2020 at the HFR research reactor in the Netherlands.”
A new revision of SALTO guidelines and related working documents is currently in preparation with a target publication date later in 2020. The new revision will also cover research reactors.
The International Conference on Operational Safety of Nuclear Power Plants that is scheduled to take place in 2021 in Beijing, China will highlight enhancements in operational safety management at all stages of the operations of nuclear power plants, from new build to existing and extended life operations.