skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Creep consolidation of nuclear depository backfill materials

Abstract

Evaluation of the effects of backfilling nuclear waste repository rooms is an important aspect of waste repository design. Consolidation of the porous backfill takes place as the room closes with time, causing the supporting stress exerted by the backfill against the intact rock to increase. Estimation of the rate of backfill consolidation is required for closure rate predictions and should be possible if the creep law for the solid constituent is known. A simple theory describing consolidation with a spherical void model is derived to illustrate this relationship. Although the present form of the theory assumes a homogeneous isotropic incompressible material atypical of most rocks, it may be applicable to rock salt, which exhibits considerable plasticity under confined pressure. Application of the theory is illustrated assuming a simple steady-state creep law, to show that the consolidation rate depends on the externally applied stress, temperature, and porosity.

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (USA)
OSTI Identifier:
6992790
Report Number(s):
SAND-79-2212
TRN: 80-018562
DOE Contract Number:
AC04-76DP00789
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; POROUS MATERIALS; CREEP; RADIOACTIVE WASTE DISPOSAL; BACKFILLING; DESIGN; RADIOACTIVE WASTE FACILITIES; MANAGEMENT; MATERIALS; MECHANICAL PROPERTIES; NUCLEAR FACILITIES; WASTE DISPOSAL; WASTE MANAGEMENT; 052002* - Nuclear Fuels- Waste Disposal & Storage

Citation Formats

Butcher, B.M. Creep consolidation of nuclear depository backfill materials. United States: N. p., 1980. Web. doi:10.2172/6992790.
Copy to clipboard
Butcher, B.M. Creep consolidation of nuclear depository backfill materials. United States. doi:10.2172/6992790.
Copy to clipboard
Butcher, B.M. Wed . "Creep consolidation of nuclear depository backfill materials". United States. doi:10.2172/6992790. https://www.osti.gov/servlets/purl/6992790.
Copy to clipboard
@article{osti_6992790,
title = {Creep consolidation of nuclear depository backfill materials},
author = {Butcher, B.M.},
abstractNote = {Evaluation of the effects of backfilling nuclear waste repository rooms is an important aspect of waste repository design. Consolidation of the porous backfill takes place as the room closes with time, causing the supporting stress exerted by the backfill against the intact rock to increase. Estimation of the rate of backfill consolidation is required for closure rate predictions and should be possible if the creep law for the solid constituent is known. A simple theory describing consolidation with a spherical void model is derived to illustrate this relationship. Although the present form of the theory assumes a homogeneous isotropic incompressible material atypical of most rocks, it may be applicable to rock salt, which exhibits considerable plasticity under confined pressure. Application of the theory is illustrated assuming a simple steady-state creep law, to show that the consolidation rate depends on the externally applied stress, temperature, and porosity.},
doi = {10.2172/6992790},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Oct 01 00:00:00 EDT 1980},
month = {Wed Oct 01 00:00:00 EDT 1980}
}
Copy to clipboard
Technical Report:
View Technical Report (0.20 MB)
DOI:  10.2172/6992790
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • Thermomechanical properties of intact rock salt and the waste package materials have appeared in the literature. Only limited data is available, however, for the two backfill materials of interest in the analyses, crushed salt and 70/30 (by weight) bentonite/sand. A unique property of bentonite-based materials is the propensity for clay particles to swell as a result of water sorption. If volume expansion is prevented or partially restricted, pressures are built up within the bentonite materials. Therefore, the primary objective of this study is to supply appropriate data (not available in the literature) in support of the aforementioned detailed thermomechanical stressmore » analyses. The study consists of laboratory tests performed on samples of crushed salt and 70/30 bentonite/sand. The remainder of this report is organized into five chapters and four appendixes. Chapter 2 describes the specimens tested in this study. Chapter 3 describes the testing machines and test procedures used. Chapter 4 gives the results of the tests on crushed salt and 70/30 bentonite/sand. Chapter 5 gives conclusions of the test program and is followed by a list of cited references. Four appendixes conclude the report. The first and second give stress-strain curves for the unconfined compression tests on crushed salt and 70/30 bentonite/sand, respectively; the third gives details of the algorithm used to compute volumetric strains during hydrostatic compression tests which accounts for vessel volume change; while the final appendix gives mean stress-volumetric strain curves for the hydrostatic compression tests. 16 refs., 18 figs., 10 tabs.« less

  • ; ; ; ...
    A great deal of money and effort has been spent on environmental restoration during the past several decades. Significant progress has been made on improving air quality, cleaning up and preventing leaching from dumps and landfills, and improving surface water quality. However, significant challenges still exist in all of these areas. Among the more difficult and expensive environmental problems, and often the primary factor limiting closure of contaminated sites following surface restoration, is contamination of ground water. The most common technology used for remediating ground water is surface treatment where the water is pumped to the surface, treated and pumpedmore » back into the ground or released at a nearby river or lake. Although still useful for certain remediation scenarios, the limitations of pump-and-treat technologies have recently been recognized, along with the need for innovative solutions to ground-water contamination. Even with the current challenges we face there is a strong need to create geological repository systems for dispose of radioactive wastes containing long-lived radionuclides. The potential contamination of groundwater is a major factor in selection of a radioactive waste disposal site, design of the facility, future scenarios such as human intrusion into the repository and possible need for retrieving the radioactive material, and the use of backfills designed to keep the radionuclides immobile. One of the most promising technologies for remediation of contaminated sites and design of radioactive waste repositories is the use of permeable reactive barriers (PRBs). PRBs are constructed of reactive material(s) to intercept and remove the radionuclides from the water and decontaminate the plumes in situ. The concept of PRBs is relatively simple. The reactive material(s) is placed in the subsurface between the waste or contaminated area and the groundwater. Reactive materials used thus far in practice and research include zero valent iron, hydroxyapatite, magnesium oxide, and others. As the contaminant moves through the reactive material, the contaminant is either sorbed by the reactive material or chemically reacts with the material to form a less harmful substance. Because of the high risk associated with failure of a geological repository for nuclear waste, most nations favor a near-field multibarrier engineered system using backfill materials to prevent release of radionuclides into the surrounding groundwater.« less

  • A thermal analysis of a deep geologic depository for spent nuclear fuel is being conducted. The TRUMP finite difference heat transfer code is used to analyze a 3-dimensional model of the depository. The model uses a unit cell consisting of one spent fuel canister buried in salt beneath a ventilated room in the depository. A base case was studied along with several parametric variations. It is concluded that this method is appropriate for analyzing the thermal response of the system, and that the most important parameter in determining the maximum temperatures is the canister heat generation rate. The effects ofmore » room ventilation and different depository media are secondary.« less

  • ;
    UNDERDOG is a computer program that aids experimentalists in the process of data reduction. This software allows a user to reduce, extract, and generate displays of data collected at the WIPP site. UNDERDOG contains three major functional components: a Data Reduction package, a Data Analysis interface, and a Publication-Quality Output generator. It also maintains audit trails of all actions performed for quality assurance purposes and provides mechanisms which control an individual's access to the data. UNDERDOG was designed to run on a Digital Equipment Corporation VAX computer using the VMS operating system. 8 refs., 24 figs., 2 tabs.

  • ;
    Mechanical properties of granulated rock salt are of interest to the WIPP project because native salt from the excavations will probably be used as backfill around the waste packages and as void filler in storage rooms, shafts and other openings. Backfill properties will be an important factor in controlling room closure rates and local permeability. To fill the need for data on time dependent compaction of crushed salt, we have done a series of tests to measure the compaction as a function of time, temperature and pressure. Tests were done for a range of temperatures from 21 to 100/sup 0/Cmore » and pressures from 1.72 MPa to 21 MPa, under quasistatic and creep conditions. All tests were done under pure hydrostatic conditions. A rock crusher was used to produce crushed salt with a maximum particle size of 1 cm. All tests were done under nominally dry conditions which means the only water present was about 0.5% water content of the salt. The major conclusions are: (1) Creep consolidation under hydrostatic stresses proceeds at a rate of approximately 0.01/t, where t is the time in seconds. Total creep consolidation in a function of log(t) and is very slow. (2) Consolidation is not very temperature dependent in the range 21/sup 0/C to 100/sup 0/C. These conclusions are tested only for times up to 3 x 10/sup 5/ seconds. The major question is whether the creep consolidation rate will continue to decelerate rapidly. If rapid deceleration continues, then for the time periods of interest creep consolidation will be small compared to the consolidation produced by quasistatic pressurization.« less