In situ changes in the moisture content of heated, welded tuff based on thermal neutron measurements

Ramirez, Abelardo; Carlson, R.W.; Buscheck, T.A.

doi:10.2172/138189

Cited by 3 publications

(5 citation statements)

References 2 publications

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“…The models proposed below are, to a large extent, similm _to the starting conceptual model shown in the Introduction because the re,_ults described here and in Ramirez et al (1990) can be interpreted in a manner consistent with the conceptual model shown in the Introduction. The most significant modifications to the pretest conceptual understanding concerned the contribution of the gas phase to rewetting of the fractured rock mass.…”

Section: Conceptual Models For Drying and Rewetting Behaviormentioning

confidence: 67%

“…Other data in Ramirez et al (1990) show that relatively small changes occurred during the power rampdown phase. Figure 2-3 shows the changes in mnisture content measured 100 days after the heater was turned off (day 301) and the rock temperatures had recovered to within a few degrees of initial conditions.…”

Section: Sample Of Resultsmentioning

confidence: 96%

“…Data in Ramirez et al (1990) show that fractures served as flow paths for steam, served to increase the penetration of the drying front, served as condensation points where sufficiently cool temperatures existed, and also served as drainage flow paths for condensate forming in the cooler regions.…”

Section: Sample Of Resultsmentioning

confidence: 99%

“…The reader is referred to Ramirez et al (1990) where all of the supporting data is presented and described in detail. The neutron logging probe contains a source of high-energy neutrons and a slow (thermal) neutron detector.…”

Section: • -+mentioning

confidence: 99%

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Prototype Engineered Barrier System Field Test (PEBSFT); Final report

Ramirez¹,

Buscheck²,

Carlson³

et al. 1991

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Section: Conceptual Models For Drying and Rewetting Behaviormentioning

confidence: 67%

Section: Sample Of Resultsmentioning

confidence: 96%

Section: Sample Of Resultsmentioning

confidence: 99%

Section: • -+mentioning

confidence: 99%

See 2 more Smart Citations

Prototype Engineered Barrier System Field Test (PEBSFT); Final report

Ramirez¹,

Buscheck²,

Carlson³

et al. 1991

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“…Consequently, they did not have the same time resolution as the TCP data, which were measured every 30 minutes. These observed features could be explained by the gravity effect as described for neutron measurements at other locations (Ramirez and Carlson, 1990). Accordingly, as temperatures increased, the evaporation rate of pore water wouirf increase.…”

Section: Field-test Resultsmentioning

confidence: 59%

Thermocouple psychrometer measurements of in situ water potential changes in heated welded tuff

Mao¹,

Wang²

1991

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Ten thermocouple psychrometers (TCPs) to measure water potential (WP) were installed in three holes in G-Tunnel at the Nevada Test Site as part of the Prototype Engineered Barrier System Field Tests. These integrated tests measured several parameters as a function of location and time within a few meters of a heater emplaced in welded tuff. The primary goal of the TCP experiment was to find out whether the combination of laboratory calibration and field use of the TCP can provide useful data for determining the change of moisture condition in the field. We calibrated the TCPs in NaCl solutions up to 80°C (176 G F) in the laboratory. In two holes, we used rubber sleeves and packers to house TCPs, and in the third hole, we used foam. All three holes were grouted behind the TCP assemblages. Field results of the heater test showed that small temperature gradients were present for all measurements. Nevertheless, the WP calibration made die necessary correction for the nonisothermal condition. The initial moisture condition indicated by TCP data was about 99.5% relative humidity or a WP of about -5 bar. This corresponded to 15.4 g/m 3 of water in the air near the borehole wall, which was much wetter than we expected. A drying and re-wetting cycle peaked at about day 140 with a WP of-65 bar in borehole P3, located below the heater. A similar cycle but reduced in scale was found at about day 175 with a WP of-45 bar in borehole P2, above the heater. Tnis difference in drying behavior above and below the heater was also observed from neutron data and was explained as a gravity effect. As temperatures increased, the evaporation rate of pore water increased. In unfractured rock, the gas-phase flow was primarily outwej-d. Water condensed above the heater would drain back to keep the boiling region wet, but water condensed below the heater would drain away from die boiling region. This conceptual model explained both the time and magnitude differences for data from holes above and below the heater.

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Thermally driven moisture redistribution in partially saturated porous media

Green¹,

Dodge²,

Svedeman³

et al. 1995

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Portions of this document may be illegible in eledronic image products. Smages are produced from the best avaihble original dOCUIIlC!llL ABSTRACTExperimental and theoretical studies have been conducted to develop a quantitative understandig of the thennohydrologic phenomena induced by emplacement of high-level radioactive waste (HLW) in an unsaturated fractured porous media. A series of laboratory experiments was conducted in a variety of media to study the physics of thermally driven moisture redistribution. Principles of similarity theory were applied to develop dimensionless parameters to be used to predict thennohydrologic behavior at the field and repository scales from that observed at the laboratory scale. Numerical modeling of two-phase flow phenomena was used to evaluate the scaling theories and interpret the experimental results.Eleven laboratory-scale experiments were conducted which are categorized according to: (i) the fluid phase that is the focus of study, (ii) temperature regime, (iii) geometry, and (iv) test medium. These experiments centered on nonisothermal liquid flow and considered sub-boiling and boiling regimes in both unconsolidated and consolidated porous media A conceptual model was identified based on experimental results in which the thermal regime was characterized as having three distinct periods: (i) an initial heating period in which moisture is transported mostly as vapor, (ii) a transitional period when water moves as both liquid and vapor, and (iii) a cooling period during which water moves mostly as liquid only.Specific heat and mass transfer mechanisms and phenomena were identified using experimental results. Three different expressions of dryoutkondensation proximal to the heat source were observed in the experiments: (i) media with low permeability and a low air-entry value experienced a relatively narrow zone of moisture buildup immediately outside of the dryout zone, (ii) media with a relatively low permeability but with a large air-entry valuer experienced condensation over a broad area beyond the dryout zone. and (iii) media with a sufficiently high permeability did not experience a complete dryout zone nor an area of condensate buildup, even for heater temperatures as high as 170 "C. Resaturation rates measured in consolidated media during the cooling period were at least 10 times slower than drying rates measured during the heating period. Gas pressure buildup was observed in heated porous media, supporting the premise of the conceptual model that gas advection, and not buoyancy, will be the prominent water transport mechanism in media with sufficiently low permeability and with sufficiently high heat source tempemtures.The V-TOUGH computer code was used to simulate the heating, transitional, and cooling periods for three spatial scales: (i) laboratory (-cm); (ii) field (-m); and (iii) repository (-km). Calculations of the temperature, pressure, and saturation fields were used to evaluate the proposed scaling theories. The model simulations indicated that fluid...

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In situ changes in the moisture content of heated, welded tuff based on thermal neutron measurements

Cited by 3 publications

References 2 publications

Prototype Engineered Barrier System Field Test (PEBSFT); Final report

Prototype Engineered Barrier System Field Test (PEBSFT); Final report

Thermocouple psychrometer measurements of in situ water potential changes in heated welded tuff

Thermally driven moisture redistribution in partially saturated porous media

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