Reproducing and discussion of mechanisms in the contact area between metallic seals and flange during aging by finite element analysis (FEA)

  • When the first site-specific interim storage licenses for DPCs (dual purpose casks), loaded with spent nuclear fuel or vitrified high-level waste from reprocessing were issued, a duration of 40 years was considered for interim storage license application and the long-term safety assessment of casks. In the meantime, the availability of a final repository is further delayed by several decades and thus interim storage for more than a century becomes a necessity. To assess the long-term performance of the typically used metal seals (e.g. Helicoflex), consisting of a helical spring (Nimonic), an inner stainless steel liner and an outer liner made from silver or aluminum, several experimental programs were conducted and are still ongoing. The investigated metal seals are typically mounted in mock-up flange systems and stored at increased temperatures to accelerate the aging process. In certain intervals the remaining seal force, the useable resilience and the corresponding leakage rateWhen the first site-specific interim storage licenses for DPCs (dual purpose casks), loaded with spent nuclear fuel or vitrified high-level waste from reprocessing were issued, a duration of 40 years was considered for interim storage license application and the long-term safety assessment of casks. In the meantime, the availability of a final repository is further delayed by several decades and thus interim storage for more than a century becomes a necessity. To assess the long-term performance of the typically used metal seals (e.g. Helicoflex), consisting of a helical spring (Nimonic), an inner stainless steel liner and an outer liner made from silver or aluminum, several experimental programs were conducted and are still ongoing. The investigated metal seals are typically mounted in mock-up flange systems and stored at increased temperatures to accelerate the aging process. In certain intervals the remaining seal force, the useable resilience and the corresponding leakage rate are determined. BAM has accompanied such programs for many years and started independent investigations in 2009. Although the remaining seal force is often used as “…one of the key parameters regarding sealing performances over time…” the presented results so far have shown that the courses of the leakage rate and the remaining seal force do not always correlate as expected. In 2016 BAM firstly published results of seals with aluminum liners where the measured leakage rate started to rise after a quite short time period (< 1 year) at 150 °C, although the seal force decreased only slightly compared to the previous measurement. After exceeding the required leakage rate of 10-8 Pa*m3/s it decreased again to acceptable values in the further course of aging. With reference to already published works, BAM has developed a new detailed ABAQUS finite-element (FE) model to represent the behavior of the seal mounted in the mock-up flange during aging, mainly characterized by the creeping of the outer liner. The main goal of the numerical simulation is to reproduce and understand the changing distribution of contact stresses (outer liner/flange) during aging and to discuss if and how it could be causative for the observed early breach of the leak tightness criteria and its later recovery.zeige mehrzeige weniger

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Autor*innen:Mike Weber
Koautor*innen:Matthias JaunichORCiD, Milan Goral, Holger Völzke
Dokumenttyp:Posterpräsentation
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2025
Organisationseinheit der BAM:3 Gefahrgutumschließungen; Energiespeicher
3 Gefahrgutumschließungen; Energiespeicher / 3.4 Sicherheit von Lagerbehältern
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Angewandte Physik
Freie Schlagwörter:Aging; Contact area; Finite element analysis; Metallic seals
Themenfelder/Aktivitätsfelder der BAM:Energie
Energie / Kerntechnische Entsorgung
Veranstaltung:PATRAM 2025, 21st International Symposium on the Packaging and Transportation of Radioactive Materials
Veranstaltungsort:San Antonio, Texas, USA
Beginndatum der Veranstaltung:27.07.2025
Enddatum der Veranstaltung:01.08.2025
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:07.08.2025
Referierte Publikation:Nein
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