Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Full-scale test of the Dome Plug for KBS-3V deposition tunnels – structural response of the concrete dome
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.ORCID iD: 0000-0003-3586-8988
Sweco.
Sweco / Lund University, Building Materials.
2019 (English)Report (Refereed)
Abstract [en]

A full-scale test of the concept for sealing deposition tunnels, intended for the future spent nuclear fuel repository, has been performed at Äspö Hard Rock Laboratory (HRL) since 2013. The planning, installation and the initial operation was previously described by Grahm et al. (2015). In the current project, the final tests of the dome plug have been performed before demolition. This phase of the project started where the filter was drained of water and a gas leakage test was conducted. After this, the filter was once again pressurized with a water pressure of 4 MPa and was held constant for about 1.5 months. After this, a strength test was performed were the water pressure was increased further so that a water pressure of about 8 MPa was reached. After the strength test was conducted, the pressure was reduced to 4 MPa again. About one month later, the filter was drained and the decommissioning of the plug started. The purpose with this report is to present the results of the measurements in the concrete dome during the leakage test and strength test that was conducted between 1st of June to 30th of August 2017. In addition, the corresponding results based on numerical simulations are also presented in this report. Finally, the general conclusions from the non-destructive testing (NDT) are presented. Four types of NDT were performed after the plug was unloaded: Ultra-sonic pulse-echo concrete tomography (MIRA), Ground Penetrating Radar (GPR), Impact Echo (IE), and Impulse Response (IR). Force Technology planned and executed all the non-destructive (ND) tests. The aim of these tests was to detect manufacturing defects such as cavities, honeycombing and material segregation. The ND tests did not reveal any manufacturing defects or cracks. However, it is not known whether the structure contained such defects or not, but no such defects where observed during core drilling and demolition. Therefore, it is not possible to conclude that any of the applied ND methods are able to reveal and locate the manufacturing defects. Although, there are indications that MIRA and GPR could reveal manufacturing defects, but it has not been proven that these are reliable methods for detection of manufacturing defects and cracks in this type of massive structure. A large cavity was detected when cores were drilled out from the upper part of the concrete plug. The cavity was not detected during the NDT, but the area of the plug containing the cavity was never targeted. It is deemed unlikely that the cavity could have been detected even if it was targeted due to the limited range of the NDT-methods. The concrete dome was instrumented with several sensors, most of them were embedded inside the concrete dome. The strain gauges, temperature sensors, and joint meters inside the concrete dome and the LVDT meters (measuring displacements) at the downstream surface was evaluated. One additional temperature sensor failed or malfunctioned during the strength test and that one of the joint meters was compressed to its limit. The measured results showed that the response of the concrete dome was in good agreement with the initial predictions with numerical analyses. Based on the measurements from the leakage and strength test, it could be seen that the sensors that measure the global behaviour, i.e. LVDT-sensors show differences before and after leakage or strength tests which indicates cracking in the dome. The sensors that measured the local behaviour varies to some extent before and after a variation in pressure, depending if they were close to areas with cracking or loss of bond. The strength test of the full-scale test was successful in proving that the dome concrete dome can withstand its theoretical design loads, without being subjected to significant cracking. As a part of the pressurization test, finite element simulations (FE-simulations) were performed and analysed. The simulations indicated that loss of bond or cracking could occur during the lowering of the pressure, primarily at the top of the plug. The pressure used during the strength test was according to the numerical analyses, far from resulting in a potential failure. However, the analyses showed that there was a risk of limited cracking close to the top of the dome near the abutment in one of the simulations. The results from the FE-simulations were also compared with the measurements from the full-scale test. In general, the structural behavior of the FE-model coresponds well with the measurements, even though the material models lack nonlinearities. The comparison of strain between the measurements and the simulations indicates that cracking or loss of bond toward the edge of the dome occurred during the pressure test.

Place, publisher, year, edition, pages
2019. , p. 73
Series
SKB P-18-14
Keywords [en]
spent nuclear fuel, deposition, concrete, dome plug
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering; Civil and Architectural Engineering, Concrete Structures
Identifiers
URN: urn:nbn:se:kth:diva-261154OAI: oai:DiVA.org:kth-261154DiVA, id: diva2:1356712
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-02

Open Access in DiVA

No full text in DiVA

Other links

SKB

Search in DiVA

By author/editor
Malm, Richard
By organisation
Concrete Structures
Civil Engineering

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf