0

Full Content is available to subscribers

Subscribe/Learn More  >

Structural Analysis Approach for Risk Assessment Under BDBE

[+] Author Affiliations
Naoto Kasahara, Takuya Sato

University of Tokyo, Bunkyo, Japan

Izumi Nakamura

National Research Institute for Earth Science and Disaster Prevention, Tsukuba, Japan

Hideo Machida

TEPCO Systems Corporation, Koto, Japan

Koji Okamoto

University of Tokyo, Tokai, Japan

Paper No. PVP2016-63416, pp. V003T03A086; 8 pages
doi:10.1115/PVP2016-63416
From:
  • ASME 2016 Pressure Vessels and Piping Conference
  • Volume 3: Design and Analysis
  • Vancouver, British Columbia, Canada, July 17–21, 2016
  • Conference Sponsors: Pressure Vessels and Piping Division
  • ISBN: 978-0-7918-5039-8
  • Copyright © 2016 by ASME

abstract

Based on the lessons learned from the Fukushima nuclear power plant accident, it is recognized the importance of the risk assessment and mitigation for failure consequences to avoid catastrophic failure of pressure equipment during severe accidents (SA) and excessive earthquake.

The objectives of structural design (from the first layer to the third layer of the defense-in-depth) is strength confirmation under assumed loading conditions. On the other hand, ones of risk assessment and mitigation (the forth layer of the defense-in-depth) is prediction of realistic failure scenarios.

Through investigation of failure locations and modes of main components under both severe accident and excessive earthquake, different failure modes from DBE(Design Basis Events) were identified for BDBE(Beyond Design Basis Events). To clarify these modes, the failure mechanisms were studied with some strength experiments.

For most of failure modes, their dominant parameters are inelastic strain rather than stress. So that large scale inelastic analysis methods were studied and extended to very high temperature and large strain.

By using above results, this paper has proposed the new structural analysis approach for risk assessment under BDBE. This is the extension of “design by analysis” concept. However it is clearly different from design approach from next viewpoints.

(1) Additional failure modes to design condition

Such additional failure modes induced by excessive loadings are considered for as local failure, creep rupture, creep buckling, ratcheting collapse and so on.

(2) Identification of dominant failure modes

Design codes require conservative evaluation against all of assumed failure modes. On the other hand, risk assessment needs adequate failure scenarios, where failure locations, modes and their order are important. For that reason, dominant failure modes have to be identified. To identify dominant modes, failure mode map concept was proposed.

(3) Best estimation

To estimate realistic accident phenomena, the best estimation is required. Therefore, dominant strength parameters and criteria without safety margins should be adopted. Through strength mechanism investigations, plastic and creep strain are recognized as more dominant parameters than stress for many failure modes. So that realistic inelastic analyses are recommended for BDBE.

Copyright © 2016 by ASME

Figures

Tables

Interactive Graphics

Video

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In