WP1, titled “LTO improvements relevant for PTS analysis,” conducted an extensive literature survey and gathered experience to identify state-of-the-art LTO improvements (PTS analyses, NPP hardware, software, and operator actions) with potential impacts on PTS analysis results. WP1 consisted of five tasks:
- Residual stress distributions in welds (WRS) and in cladding
- Warm pre-stress (WPS) application in PTS analysis
- Improved thermal-hydraulic (TH) analysis
- Probabilistic PTS analysis
- Further potential LTO improvements for PTS mitigation
The state-of-the-art surveys included the collection of existing solutions, assessments, and identification of gaps for improvement. Technical questionnaires were completed by partners, and the results were summarized in a public report.
WP2, “Improved TH analysis,” quantified the impact of LTO improvements and human factors on TH boundary conditions. TH analyses were performed for the base case (SBLOCA with a 50 cm² break in the hot leg and loss of offsite power) and for six selected LTO improvements using various codes (RELAP5, ATHLET, TRACE, etc.), and for evaluations of three human interactions. TH data sets were exported for deterministic and probabilistic structural and fracture-mechanical analyses. Uncertainties related to TH models, plant parameters, and human factors were assessed. A Phenomena Identification and Ranking Table (PIRT) was created. A public summary report was issued.
WP3, “Deterministic margin assessment,” included calculations of temperature and stress fields for the base case and nine LTO improvements using 1D and 2D FE models. Results were published in Deliverables D3.1. In Task 3.3 fracture-mechanics benchmark calculations were conducted to determine stress intensity factors and maximum allowable reference temperatures, published in Deliverable D3.3. Further fracture-mechanics assessments of LTO improvements and TH uncertainties were carried out in Tasks 3.4 and 3.5 with results summarized in Deliverable D3.4. A public summary report was issued.
WP4, “Probabilistic margin assessment,” performed probabilistic analyses. Temperature and stress fields for 59 up to 130 TH data sets covering the TH uncertainties using Wilks approach were calculated using the 1D and 3D FE models. Probabilistic fracture-mechanics PTS analyses were performed in Tasks 4.3 - 4.5 for baseline benchmarks, LTO improvements and TH uncertainities. Results were published in Deliverables D4.3 - D4.5. Probabilistic margin assessments were performed in Task 4.6 with results published in Deliverable D4.6. A public summary report was issued.
WP5, “Definition of best-practice for advanced PTS analysis,” focused on gathering conclusions and recommendations from WP1 to WP4. Feedback from the Advisory Board and End-users was collected throughout the project, especially during the End-user workshop and Final seminar. The "Final report on guidance on best-practice for deterministic and probabilistic RPV integrity assessment" was published.
WP2-4 analyses and the preparation of best-practice guidance were supported by WP6, ensuring communication, visibility, and dissemination of project results. WP6 also contributed to strategic planning and operational support for the project’s exploitation.
