Bruce Letellier

Mesoscale Carbon Sequestration Site Screening and CCS Infrastructure Analysis

We explore carbon capture and sequestration (CCS) at the meso-scale, a level of study between regional carbon accounting and highly detailed reservoir models for individual sites. We develop an approach to CO(2) sequestration site screening for industries or energy development policies that involves identification of appropriate sequestration basin, analysis of geologic formations, definition of surface sites, design of infrastructure, and analysis of CO(2) transport and storage costs. Our case study involves carbon management for potential oil shale development in the Piceance-Uinta Basin, CO and UT. This study uses new capabilities of the CO(2)-PENS model for site screening, including reservoir capacity, injectivity, and cost calculations for simple reservoirs at multiple sites. We couple this with a model of optimized source-sink-network infrastructure (SimCCS) to design pipeline networks and minimize CCS cost for a given industry or region. The CLEAR(uff) dynamical assessment model calculates the CO(2) source term for various oil production levels. Nine sites in a 13,300 km(2) area have the capacity to store 6.5 GtCO(2), corresponding to shale-oil production of 1.3 Mbbl/day for 50 years (about 1/4 of U.S. crude oil production). Our results highlight the complex, nonlinear relationship between the spatial deployment of CCS infrastructure and the oil-shale production rate.

RoverD: Use of test data in GSI-191 risk assessment

Abstract An approach is described that would use test data to evaluate the risk associated with the concerns raised in Generic Safety Issue 191 (GSI-191). The relationship to the elements of quantitative risk-informed regulation for addressing the concerns raised in GSI-191 in pressurized water reactor (PWR) plant licensing is described. Use of experimental data from a deterministic sump performance test to establish scenario success for tested debris loads is summarized and compared to the licensing requirements in the regulations. Generation and transport of debris to the emergency core cooling system sump from a loss-of-coolant accident is described, and data are shown for a particular PWR. Application of the analysis results to a license amendment for an operating PWR is summarized.

Head loss characteristics of a fibrous bed in a pwr chemical environment

This paper examines the generation and effect of secondary materials created by chemical reactions between dislodged fiberglass insulation debris and simulated cooling system water that would be present within the containment of a pressurized water reactor following a loss-of-coolant accident (LOCA). Corrosion and subsequent precipitation of metals (aluminum, iron, zinc, and calcium) pose an important safety concern because the surface area of exposed metal inside containment represents a large potential source term of chemical debris products that may be capable of blocking the recirculation sump. The Advisory Committee on Reactor Safeguards (ACRS) cited the presence of gelatinous material recovered from the Three Mile Island containment pool after its 1979 accident and noted that the formation of adverse chemical products had not been previously examined under Generic Safety Issue 191 (GSI-191) research program. Based on small-scale tests, the following key issues related to corrosion and precipitation were investigated: 1. Do credible corrosion mechanisms exist for leaching metal ions from bulk solid surfaces, and if so, what are the typical reaction rate constants?2. Can corrosion products accumulate in the containment pool water to the extent that they might precipitate as new chemical species at pH and temperature levels that are relevant to the LOCA accident sequence?3. How do chemical precipitants affect the head loss across an existing fibrous debris bed? Findings from these tests confirmed that corrosion of metal can occur and that artificially induced metallic precipitants can cause substantial additional head loss.

Experimental Validation of CFD Analyses for Estimating the Transport Fraction of LOCA-Generated Insulation Debris to ECCS Sump Screens

Abstract This paper presents a comparison between computational fluid dynamics (CFD) analysis and experiments in order to help pressurized water reactor (PWR) plants develop a methodology for estimating the amount of insulation debris that may transport to the sump screens of an emergency core cooling system (ECCS). This information is essential for the resolution of Generic Safety Issue-191 on the safety margins of the ECCS systems subsequent to debris accumulation and head loss at the screen. Tests were carried out on a simulated containment floor in the laboratory to determine the flow velocities in which different types of objects including insulation debris would move along the floor. CFD analyses were independently carried out to determine the flow velocities in the containment under different flow rates and break locations. It was shown that the flow regimes predicted by the CFD analyses compare well with the experimentally observed movement along the floor. Based on this observation the transport fraction of different types of insulation debris can be estimated specific to any PWR plant.

Transport characteristics of selected pressurized water reactor loca-generated debris

Abstract In the unlikely event of a loss-of-coolant accident (LOCA) in a pressurized water reactor, break jet impingement would dislodge thermal insulation from nearby piping, as well as other materials within the containment, such as paint chips, concrete dust, and fire barrier materials. Steam/water flows induced by the break and by the containment sprays would transport debris to the containment floor. Subsequently, debris would likely transport to and accumulate on the suction sump screens of the emergency core cooling system (ECCS) pumps, thereby potentially degrading ECCS performance and possibly even failing the ECCS. A systematic study was conducted on various types of fibrous and metallic foil debris to determine their transport in water. Test results reported include incipient movement, bulk movement, accumulation on a screen, the ability of debris to jump over 5-cm (2-in.) and 15-cm (6-in.) curbs, and the effects of accelerating flow and turbulence. These data are currently being used in conjunction with computational fluid dynamics modeling to determine the potential for each debris type to reach the suction screen.

The Benefits of Using a Risk-Informed Approach to Resolving GSI-191

The emergency core cooling system (ECCS) and containment spray system (CSS) in a pressurized water reactor (PWR) are designed to safely shutdown the plant following a loss of coolant accident (LOCA). The assurance of long term core cooling in PWRs following a LOCA has a long history dating back to the NRC studies of the mid 1980s associated with Unresolved Safety Issue (USI) A-43. Results of the NRC research on boiling water reactor (BWR) ECCS suction strainer blockage of the early 1990s identified new phenomena and failure modes that were not considered in the resolution of USI A-43. As a result of these concerns, Generic Safety Issue (GSI) 191 was identified in September 1996 related to debris clogging of the ECCS sump suction strainers at PWRs. Although plants have taken steps to prevent strainer clogging (by increasing the screen area, for example), satisfactory closure of this issue has proved elusive due to long term cooling issues and the effect of chemical precipitates on head loss. Previous investigators have identified bounding scenarios using conservative inputs, methods, and acceptance criteria. The acceptance criteria are applied in a “pass/fail” fashion that ignores risk. That is, if the results are acceptable, the issue has been resolved. Otherwise, it is necessary to either redo the analysis with partial relaxation of analytical conservatisms or perform additional plant modifications to ensure that the acceptance criteria are met. This article describes a new approach to close out the GSI-191 issue by evaluating the risk associated with ECCS performance on post-LOCA core cooling as a basis to change the plant license. The approach includes an assessment of LOCA frequencies as a function of break size at locations along the reactor coolant system, as well as a full quantification of the uncertainties associated with LOCA frequencies and the generation, transport, accumulation, and subsequent impact of debris on ECCS performance. The overall frameworks for the deterministic and risk-informed approaches are summarized with emphasis on the risk-informed method. The differences between the deterministic approach taken in the past and the new risk-informed approach are described. Advantages and disadvantages between the two methods are described and contrasted for the GSI-191 issue. The South Texas Project (STP) GSI-191 risk-informed closure efforts are presented.Copyright

Accumulation and head-loss characteristics of selected pressurized water reactor loca-generated debris

Abstract In the event of a loss-of-coolant accident within the containment of a pressurized water reactor (PWR), piping thermal insulation and other materials in the vicinity of the break will be dislodged by break jet impingement. A series of tests was conducted on two different closed-loop test setups that were specifically designed to study the accumulation of debris and the consequent head loss across sump screens in PWRs. This paper addresses issues related to accumulation of transported debris on the sump screen and the consequent head loss. New test data that provide insights on head loss across a debris bed consisting of fragments of calcium silicate were generated.