Potential for Generation of Flammable Mixtures of Hydrogen from Aluminum-Grout Interaction in the K Basins During Basin Grouting
During the course of deactivation and decommissioning (D&D) of the K-Basins, the basins will be partially filled with grout so as to immobilize residual equipment and debris. Some of this residual debris, principally empty fuel canisters, identification tags, and long-handled tools, contain aluminum metal. The aluminum metal will corrode when contacted with the high pH grout, resulting in the generation of hydrogen. Pacific Northwest National Laboratory (PNNL) evaluated existing experimental and analytical studies of this issue to 1) determine whether sufficient hydrogen will be generated and collected during the K-Basins grouting activity to potentially create the conditions for hydrogen deflagration/explosion and 2) identify process constraints that will provide assurance that the conditions for hydrogen deflagration/explosion will not exist. Based on the review of available experimental and analytical studies, it was concluded that the likelihood of generating a flammable mixture of hydrogen from interaction of residual aluminum metal with grout is low but not zero. However, a flammable mixture of hydrogen will not be generated anywhere in the basin facility during grouting of the KE Basin as long as the following conditions are met: •The residual aluminum metal inventory in the basin, especially the fuel canisters, are not stacked on top of one another. This will prevent over-concentrating the aluminum metal inventory over a small surface area of the basin floor. •The temperature of the grout is maintained below 90ºC (194ºF) during pouring and at least three hours after the aluminum metal has been covered (lower grout temperatures result in lower hydrogen generation rates). After about three hours immersed in the grout, an oxide or corrosion layer has formed on the aluminum metal significantly reducing the corrosion/hydrogen generation rates assumed in this analysis. •The basin water temperature is maintained at less than 60ºC (140ºF) for at least three hours after interruption of the grout pour if the aluminum metal in the basin has not been completely covered (so as to minimize reaction of the uncovered aluminum metal with Ca(OH)2). This can effectively be done by ensuring that the basin water temperature is less than 70ºF (21ºC ) prior to initiating grouting of the basin and ensuring that the basin water level is at least 10 feet above the surface of the grout. •The basin water is not removed at the same time as grout is being poured (to avoid removing the hydrogen to another potential collection point). This condition is not necessary if the water removal system is appropriately vented to prevent accumulation of hydrogen in the system or after the aluminum metal has been covered with grout for at least three hours. These conclusions are supported as long as the amount and physical configuration of the residual aluminum inventory in the KE Basin is consistent with the assumptions described in Appendix A.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15016087
- Report Number(s):
- PNNL-15156; 830403000
- Country of Publication:
- United States
- Language:
- English
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