Modeling approaches for concrete barriers used in low-level waste disposal

Abstract

A seriesof threeNUREGsand severalpapersaddressingdifferentaspectsof modelingperformanceof concretebarriersfor low-level radioactivewaste disposal havebeen preparedpreviouslyfor the Concrete BarriersResearch Project.This documentintegratesthe information fromthe previous documentsinto a generalsummaryof modelsand approachesthatcan beused in performanceassessmentsof concretebarriers. Models for concretedegradation,flow,and transport throughcrackedconcretebarriersare discussed. The modelsfor flow andtransportassumethatcracks have occurredand thusshouldonly be used forlater times in simulationsafterfully penetratingcracksareformed.Most of the modelshave been implemented in a computercode, CEMENT,thatwas developed concurrentlywith this document.User documentation forCEMF_NT is providedseparatefromthisreport.To avoid duplication, the readeris referredto the three previousNUREGsfor detailed discussionsof each of the mathematical models. ,Someadditionalinformation that was notpresentedi_ the previousdocumentsis also included. Sectionsdiscussinglessons learned from applicationsto actual performanceassessmentsof low-level waste disposal facilities are provided. Sensitivedesignparametersare emphasizedto identify criticalareas of performanceforconcrete barriers, andpotentialproblems in performanceassessments are also identifiedand discussed.

Hydraulic Properties Data Package for the E-Area Soils, Cementitious Materials, and Waste Zones - Update

“…However, the nomenclature utilized within the literature is inconsistent. Therefore the following definitions of diffusion coefficient have been made in order to classify the various values of diffusion coefficient found within the literature (Seitz and Walton, 1993;Walton et al, 1990):…”

User`s guide for simplified computer models for the estimation of long-term performance of cement-based materials

“…One-hundred values of ton et al (1990), Equation (7), page 16, and the deterioration depth x versus time can be hydrogen evolution (passive) corrosion model of computed in this routine. Seitz and Walton (1993), Equation (4), page 8. The corrosion rate is assumed to be controlled by 2.1.8 SATTK2.…”

“…The model is executed by a the oxygen diffusion degradation model of Wal-FORTRAN subroutine call: ton et al 1990, Equation 7, page 16, and the hydrogen evolution (passive) corrosion model of Seitz and Walton (1993), Equation 4, page 8.…”

“…Appendix A also models developed or investigated are described in includes example interactive screens for the main the NUREG documents referenced in this report driver. Example interactive screens for each of (Seitz and Walton 1993;Walton 1992;Walton the drivers for the individual subroutines are proand Seitz 1991;Walton et al 1990).…”