Dr. Satyen Baindur

Probabilistic Safety Assessment & Reliability Resources Page

Probabilistic Safety Assessment for NPPs - Useful Links
Ageing PSA
Recent and Upcoming Conferences: Probabilistic Safety Assessment

Probabilistic Safety Assessment (PSA) of nuclear power plants (NPPs) extends the original discipline of engineering reliability analysis, representing a method of modeling a plant's response to a set of initiating events - whether those arising from within the plant (internal events) or those arising from external causes (external events). A number of factors are considered, including random failure of components, common cause failures, human errors, as well as specific operating modes of the reactor.

3 Levels of PSA

By convention, 3 levels of PSAs are recognized:
1. Level 1 PSA identifies and quantifies the sequences of events that may lead to a loss of core structural integrity and massive fuel failures - an important risk statistic resulting from such analysis is the core damage frequency - CDF.
2. Level 2 PSA starts from the results of Level 1, and analyzes containment behaviour, evaluates the radionuclides released from the failed fuel, and quantifies the releases to the environment - an important measure of risk that emerges from this level of analysis is the large early release frequency - LERF.
3. Level 3 PSA starts from Level 2 results, and analyses the distribution of radionuclides in the environment and evaluates the resulting effect on public health.
(CNSC Regulatory Standard S-294, Probabilistic Safety Assessment (PSA) for Nuclear Power Plants, 2005)

Living PSA

After the initial results have been generated, the PSA needs to be continually updated in light of experience (for example, incorporating the most recent failure statistics on systems, structures and components (SSC), or the most recent information on the probable course of accident progression). This concept has come to be called the "living PSA".

Ageing PSA - Links

While PSAs have served to provide probabilistic estimates of and numerical limits on the likelihood of the worst possible accident consequences - such as the risk of core damage, they also provide valuable input on operational management and on assessment of plant status. As plant components age, incorporating ageing effects on the PSA analyses assumes greater importance, and very useful operational management insights can be gained from PSAs which incorporate ageing effects into reliability measures, failure rates or safety margins.

Probabilistic Safety Assessment for NPPs - Links

1. IAEA Probabilistic Safety Assessment Level 1 Page
2. IAEA Probabilistic Safety Assessment Level 2 Page
3. IAEA TecDoc 1511: Assessing the Quality of Probabilistic Safety Analysis for Nuclear Power Plants
4. US NRC Probabilistic Risk Assessment Explained
5. State of the Art Reactor Consequence Analysis (SOARCA) - US Nuclear Regulatory Commission.
6. Use and Development of Probabilistic Safety Assessment - NEA/CSNI/R(2007)12
7. Risk Monitors: The State of the Art NEA/CSNI/R(2004)20
8. International Association for Probabilistic Safety Assessment and Management
9. OECD Pipe Failure Data Exchange Project (OPDE)