Advances of Generation III/III+ Reactor Designs
Containments for LWRs are constructed as part of engineered safeguards in assuming an important role in the safety of the NPP operation. Traditional containments are designed to be shell type of steel or reinforced concrete structures focusing on the dual functions of: (1) protection of NSSS and safety related systems and equipment and (2) leak-tight membrane to contain the postulated radiological release to the environment. The generation III/III+ reactors have incorporated design features such as adding a second reinforced concrete shield structure over the primary containment for protection against the effects of the potential use of large commercial aircraft as a weapon against a nuclear installation. In addition, the new reactor containment designs have increasingly utilized more reliable evolutionary and passive safety systems which can be actuated by gravity, convective natural circulations that use fewer or no active safety systems, therefore are less prone to human errors.
Compared to previous generations of reactor design, the advances in technologies utilized in generation III/III+ may be highlighted as follows:
- 1. Employ highly reliable, less complex safe shutdown systems, particularly ones which use inherent or passive safety features, and reduce the possibility of core melt accidents, resulting in an enhanced safety;
- 2. Incorporate simplified and better understood systems which allow more straightforward engineering analysis and design, operate with fewer operator actions to significantly reduce potential human errors, and increase operator comprehension of reactor conditions;
- 3. Use standardized designs to enable identification and resolution of safety issues related to design and constructions early and allow for concurrent resolution of safety and security requirements, resulting in an overall security systems that requires fewer human actions;
- 4. Include features which prevent a simultaneous breach of containment and loss of core cooling from an aircraft impact, or that inherently delay any radiological release;
- 5. Consist of features which maintain spent fuel pool integrity following an aircraft impact;
- 6. Design for higher availability and longer operating life — typically 60 years as opposed to 40 years for current operating reactors, and;
- 7. Incorporate features to allow the use of higher burn-up and burnable absorbers to extend fuel life resulting in increased fuel efficiency and reducing the amount of nuclear waste.