The committee is confident that the WIPP can meet its general performance objectives as requested by the certification process. However, uncertainties remain in the long-term performance of the repository. Some of the recommendations in this report were released in the committee's interim report (Appendix A1) to which the DOE has responded with a number of actions taken (see Appendix A2). The committee encourages implementation of the improvements suggested by the DOE to address its recommendations. In Chapter 2 and Chapter 3, the committee addresses some new issues concerning the operation and long-term safety of the WIPP and reiterates for emphasis some of the recommendations of the interim report. This chapter closes the study with an overarching finding and recommendation.
The committee finds that the monitoring of selected performance indicators during the estimated 35-year or longer pre-closure phase of the WIPP is needed to possibly enhance confidence in the long-term safety performance of the repository. Although 35 to possibly 100 years is a short time compared to the 10,000-year period of compliance, the committee believes that it is long enough to reduce the uncertainties in many critical performance parameters. The rates of important processes such as salt creep, brine inflow (if any), and gas generation are predicted to be highest during this period; therefore, monitoring during the pre-closure phase is particularly important. Moreover, the committee finds that there are a number of specific actions that can be taken in the National TRU Program to facilitate operation of the WIPP while increasing safety and reducing costs.
The committee recommends that the DOE develop and implement a program during the pre-closure phase to monitor selected performance indicators that specifically relate to the creation of a radionuclide source term and to pathways for radionuclide transport. Monitoring should continue throughout the preclosure phase and longer, if possible. Emphasis in the monitoring should be on waste mobilization and
transport mechanisms, including brine inflow, gas generation, geochemical reactions, room sealing, and surface and subsurface hydrology. The committee recommends that the results of the on-site monitoring program be used to improve the performance assessment for recertification purposes. These results will determine whether the need for a new performance assessment is warranted. Given the uncertainties, it is impossible to predict if the results of the monitoring program will be different than those modeled by the performance assessment. However, it is important to ensure that, if there are changes, these will be detected.1 Moreover, actions should be taken to improve and better define the National TRU Program for issues related to waste characterization and packaging requirements, total inventory of organic materials, communication and notification system, emergency response training, and gas generation during transportation.
The committee did not have all of the information necessary to prioritize the issues mentioned in this report. However, it has provided a selected number of recommendations that are believed to improve the operation and long-term safety of the WIPP. The committee recognizes that the recommendations in this report will have some economic impact on the transuranic waste management program. The DOE needs to balance costs against the improved assurance of facility performance in the longer term.
1Only measurable changes are important to verify the performance of the repository; for instance, a few drops of brine do not imply that the repository is not in compliance with containment requirements.