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Introduction
The National Research Council, at the request of the U.S. Department of Energy-Carlsbad Field Office (DOE-CBFO), appointed a committee1 to provide an independent review of DOE’s proposed characterization plan for defense-related remote-handled (RH) transuranic (TRU) waste.2 The committee’s statement of task is reported in Sidebar 1. About 3,600 m3 of defense-related RH-TRU waste are currently stored across DOE’s weapons complex. DOE is seeking authorization to dispose of this waste at the Waste Isolation Pilot Plant (WIPP) in New Mexico as part of the effort to clean up its nuclear weapons complex.
The WIPP, briefly described in Sidebar 2, currently holds a certification issued by the United States Environmental Protection Agency (EPA) and a Resource Conservation and Recovery Act (RCRA) Permit issued by the New Mexico Environment Department (NMED). The WIPP’s certification and the RCRA Permit allow the shipment and disposal of contact-handled (CH) TRU waste but exclude RH-TRU waste. When DOE first applied for certification of WIPP, it proposed a characterization plan for both RH-TRU and CH-TRU waste (DOE-CAO, 1996a). However, in their final decision, both EPA and NMED declared that DOE did not provide an adequate waste characterization method for RH-TRU waste and prohibited this waste from being shipped or emplaced in the repository. Both agencies also stated that DOE did not adequately describe its full RH-TRU waste inventory. However, both EPA and NMED acknowledged that DOE proposed an adequate characterization plan for CH-TRU waste. The main condition that must be met for the removal of the prohibition on emplacing RH-TRU waste in WIPP is for DOE to provide a characterization plan for RH-TRU waste that is approved by EPA and NMED.
DOE is now proposing a characterization plan for RH-TRU waste that relies mainly on pre-existing knowledge of waste characteristics, called acceptable knowledge (AK),3 and reduces the use of confirmatory measurements. The characterization plan is described in more detail in Chapter 4. DOE is concerned with the potential exposure of workers to radiation during the characterization of RH-TRU waste and with the costs associated with handling and characterization activities.4 DOE is now preparing a new characterization plan for RH-TRU waste that is described in the following two documents to be submitted to EPA and NMED in the next few months:
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Document 1: Notification of proposed change to the EPA Title 40 CFR Part 194 certification of the WIPP (DOE-CBFO, 2001a).
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Document 2: Request for RCRA Class 3 permit modification to the NMED (DOE-CBFO, 2001b).
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The Committee on the Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant. Biographical sketches of committee members can be found in Appendix C. |
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Transuranic waste is radioactive waste containing alpha-emitting radionuclides of atomic number greater than 92, half-life greater than 20 years, and activity greater than 100 nanocuries per gram of waste. Transuranic waste is classified as remote-handled or contact-handled waste according to the radiation dose rate at the surface of the package. A more detailed definition is given at the beginning of Chapter 2. |
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For the definition of AK see the glossary (Appendix D) and Chapter 4. |
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Remote-handled TRU waste requires the use of remote-handling tools and/or heavy shielding for the protection of workers. |
In this report, Documents 1 and 2 will often be referred to as the characterization plan’s “supporting documents.” EPA will review Document 1 to consider a change in the certification of WIPP, and NMED will review Document 2 to consider a modification in the RCRA Permit affecting mixed (see definition in Chapter 2) TRU waste. If EPA and NMED agree to modify certification and RCRA permit to allow RH-TRU waste in WIPP, final characterization requirements for RH-TRU waste will be established by these two regulatory agencies on the basis of DOE’s proposed plan.
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SIDEBAR 1 Statement of Task The objective of this study is to review and evaluate DOE’s plan to characterize remote-handled transuranic waste to be disposed of at WIPP. The committee will provide recommendations, as necessary, for improving the plan’s technical soundness, protection of worker safety, and compliance with applicable regulatory requirements. This study does not address transportation issues related to RH-TRU waste. Examples of criteria that could be used by the committee to review DOE’s characterization plan for RH-TRU waste are the following: validity of assumptions used for the proposed plan; quality of information available on RH-TRU waste; uncertainties on process knowledge data and consequences if wrong; appropriateness and sensitivity of overall system safety to uncertainties in the waste specifications; limitations of the methodologies and procedures to characterize RH-TRU waste; and validity of DOE’s conclusions concerning its characterization plan. |
Committee’s Task
This committee’s task is to provide recommendations to determine the RH-TRU characterization plan’s technical soundness, compatibility with worker safety, and compliance with applicable regulatory requirements. The committee reviewed only a draft version of Documents 1 and 2, dated July 2001. Findings and recommendations in this interim report apply only to this draft. DOE indicated that its characterization plan is evolving in response to discussions with the committee and to the recommendations by the Institute for Regulatory Sciences (RSI, 2001), which also reviewed Documents 1 and 2. DOE provided the committee with additional and updated information on its plan through briefings and correspondence exchanges. The committee did not verify data provided by DOE on RH-TRU waste inventories or cost estimates.
Also, the committee also did not assess the validity of supplementary information supporting the characterization plan, such as the Sandia Inventory Impact Assessment Reports in Document 1 (Attachment B) and Document 2 (Appendix 1). The committee did, however, assess how DOE interpreted and used the results of these reports in supporting its characterization plan. The initial assumption for this study is that all the RH-TRU waste to be characterized is identified as defense-related and hence can be sent to WIPP, once a characterization plan is approved by EPA and NMED. The statement of task directs the committee to evaluate compliance of DOE’s characterization plan with regulatory requirements. These requirements are not yet
specified for the characterization of RH-TRU waste. The characterization plan for RH-TRU waste, which will be the basis of characterization requirements, is currently being developed and is the object of this report. Therefore, the committee can only address compliance with the existing legal requirements, stated in the Land Withdrawal Act (Congress, 1992) and in Title 40 of the Code of Federal Regulations Part 194 (40 CFR 194).
The committee offers in this interim report its initial findings and recommendations to draw DOE’s attention to issues that emerged during the initial phase of the study. In the final report, scheduled for release in the summer 2002, the committee will provide a final set of findings and recommendations to address fully its task statement reported in Sidebar 1. This interim report has been reviewed in accordance with the procedures of the National Research Council and reflects the consensus of the committee.
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SIDEBAR 2 The Waste Isolation Pilot Plant The WIPP, located near Carlsbad in southeastern New Mexico, is an underground facility mined within a 600-meter-thick salt bed lying 660 meters below the surface. The salt bed, called the Salado Formation, originated approximately 250 million years ago. Large salt beds such as this are found only in geologic regions that lack significant flows of groundwater. The WIPP is located in the Carlsbad area because this deep, relatively dry, underground environment greatly reduces the possibility of waste releases from the repository by natural processes. Moreover, waste containment relies on an important property of salt beds: salt tends to “heal” itself after being mined. Therefore, after several hundred years, the mined salt at WIPP will creep back around the waste and encapsulate it, thereby permanently locking it deep beneath the surface. The WIPP has been under study since the mid-1970s and under construction since January 1981. EPA certified WIPP for emplacement of CH-TRU waste in May 1998. In 1999, NMED granted to WIPP a permit (the RCRA Permit) to emplace mixed CH-TRU waste. The first CH-TRU waste shipment was received from the Los Alamos National Laboratory in March 1999. The first out-of-state shipment was received in June 1999, from the Rocky Flats Environmental Technology Site, and in September 2000 the first mixed CH-TRU waste shipment was received from the Idaho National Engineering and Environmental Laboratory. The WIPP and a performance assessment tool A performance assessment is a risk-based assessment of the safety performance of a nuclear waste facility. The purpose of the performance assessment for WIPP is to evaluate the ability of the repository to isolate radioactive waste from the accessible environment. The performance assessment organizes information relevant to long-term (i.e., over a 10,000-year period) repository behavior by assessing the probabilities and consequences of major scenarios by which radionuclides can be released into |
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the environment surrounding the WIPP site. Important scenarios include those due to human activities, whether deliberate or unintentional, that might occur near the WIPP site and potentially compromise the integrity of the repository. The performance assessment process consists of:
The final analysis of WIPP’s certification of compliance consisted of a qualitative assessment of the quantitative results of the performance assessment (National Research Council, 2001, 1996). DOE identified ten radionuclides important to the long-term performance of WIPP: americium-241, curium-244, cesium-137, plutonium-238, plutonium-239, plutonium-240, plutonium-241, strontium-90, uranium-233, and uranium-234. Of these ten, strontium-90, uranium-233, and cesium-137 are important to RH- but not CH-TRU waste streams. Containment requirements for these radionuclides and others are promulgated in Title 40 CFR 191, Appendix A. The performance assessment tool was peer reviewed and validated by EPA in its final decision to certify WIPP. |
