Time of Compliance Reduced To 1000 Years; New Three-Tiered Approach

Jeremy L. Dillon
RW Monitor
2/21/2014

The Nuclear Regulatory Commission is moving to implement a three-tiered approach for performing a performance analysis for a low-level waste disposal site, including an initial time of compliance of 1,000 years—down significantly from previous proposals, according to the 10 CFR Part 61 Staff Requirements Memorandum issued by the NRC Commissioners this week. Previously, NRC staff had proposed requiring low-level waste disposal sites to perform a site-specific analysis to prove their site was protective of public health and safety for 10,000 years, down from a period of compliance of 20,000 years of previous drafts, with a two-tier analysis: the first period covering 10,000 years and the second period covering long-lived isotopes. The approach outlined in this week’s SRM, though, would have an initial tier cover the 1,000-year time of compliance followed by a further performance assessment including a protective assurance analysis from the end of compliance period through 10,000 years and a qualitative analysis stretching beyond 10,000 years to “evaluate the ability of the disposal system to mitigate long-term risks.”

The Commissioners’ votes favored reducing the time of compliance 4-1, with NRC Chair Allison Macfarlane being the lone vote in favor of keeping the staff’s recommendation of 10,000 years. All four Commissioners voting for the reduced period cited the uncertainty of having such an extended time frame. “Looking back 10,000 years in human history, we would find early farmers planting barley along the Nile, never dreaming of the great Egyptian civilization their descendants would establish thousands of years later,” Commissioner William Magwood said in his voting comments. “These farmers would have been unlikely to anticipate the environmental issues facing Egypt in 2013 B.C., let alone 2013 A.D. Despite our advances in technology, I doubt that our ability to predict the world 10,000 years from today is much improved over those Nile valley barley famers. It provides false comfort to insist on an analysis based on guesswork and subjective speculation.”

Chair Backed 10,000 Years on Basis of Consistency

Macfarlane argued for consistency as her reasoning for voting for a time of compliance of 10,000 years. She noted that 10,000 years would align with international standards, NRC staff practice in the past decade, and federal standards for the disposal of high-level nuclear waste and defense-related transuranic wastes. “We should strive to apply consistent evaluation standards for future generations that could be exposed to long-lived radioactive waste—whether it is radionuclides from depleted uranium wastes that were used to make nuclear fuel or the actual waste products that resulted from the use of that same fuel,” Macfarlane said in her voting comments. “In short, it is important to understand the ability of the natural system in impeding doses in potential periods after engineering barriers have deteriorated, the groundwater pathway is more dominant, sorption is likely higher, and long-lived radionuclides continue to present a hazard from in-growth of radium and lead daughter products.”

New Middle Tier

To ensure that long-term performance of a site is still considered, the Commissioners implemented a new middle tier between the time of compliance and the qualitative review beyond 10,000 years. The SRM explained this new middle tier by saying, “Given the significant uncertainties inherent in these long timeframes, and to ensure a reasonable analysis, this performance assessment should reflect changes in features, events, and processes of the natural environment such as climatology, geology, and geomorphology only if scientific information compelling such changes from the compliance period is available. In general, this analysis should strive to minimize radiation dose with the goal of keeping doses below a 500 mrem/year analytical threshold,” the SRM said.

Commissioner Kristine Svinicki’s voting comments reiterated the need for the middle tier. “A further analysis should be performed for the period from the end of the compliance period through 10,000 years,” Svinicki said. “To address the significant uncertainties inherent in these long timeframes, this analysis should assume a constancy of features, events, and processes unless scientific information compelling variation in these parameters is available. In general, this analysis should be guided by ALARA principles. Unacceptable consequences (i.e., those requiring the applicant to propose changes in the disposal site design or inventory limits, or alternative methods of disposal) should be represented by doses to future generations of the public in excess of 500 millirem per year.”

Time of Compliance a Policy Decision

From the NRC Staff perspective, the time of compliance came down to a policy decision, according to NRC Director of the Division of Waste Management and Environmental Protection Larry Camper. The Staff had recommended a time of compliance of 10,000 years with a performance assessment looking qualitatively beyond 10,000 years, but Camper said this new direction from the Commission falls in line with the holistic view of the process. “With the period of compliance, whether it’s 1,000 years or 10,000 years, you have to look at the whole analysis approach,” Camper told RW Monitor this week. “In other words, this approach is a three-tier approach so you can’t look at it and say ‘is ‘1,000 years enough?’ or ‘is 10,000 years the right number?’ You have to look at it and say ‘what kind of process is being brought to bear over all?’ The period of compliance is one part of it. The Commission has now assigned this second level as well as the long term performance assessment. You need to look at it in the aggregate,” Camper said.

Compatibility Category ‘B’

The SRM also said that the proposed rule should be published with a compatibility category B applied to it, thus enforcing the Agreement States follow this new requirements, and thereby create a national standard. “Finally, with regard to the staffs proposed recommendation on compatibility, I believe that the obvious trans-boundary issues associated with this rule require consistent application between the various Agreement States,” Magwood said. “Therefore, I find clear cause to designate this rule to have a compatibility designation of "B" for the entire rule.” Four out of the five commissioners agreed with this compatibility category, with Macfarlane reserving judgment on it until she sees the final proposed ruling. 

10,000 Year Intruder Analysis

The SRM also included a 10,000 year intruder assessment analysis with a specific dose limit of 25 mrem/year.  However, it did include a provision to make sure intruder assessments were reasonable. “The proposed rule should clearly indicate that the intruder assessment should be based on intrusion scenarios that are realistic and consistent with expected activities in and around the disposal site at the time of site closure,” the SRM said.

Magwood reinforced this notion in his voting comments. “Further, I approve staff’s proposal to require a 10,000 year intruder assessment analysis so long as such an assessment is built upon the same assumptions as the compliance and protective assurance analyses discussed above,” Magwood said. “However, in order to avoid boundless speculation, I suggest that the rule clearly indicate that the intruder assessment should be based on intrusion scenarios that are realistic and consistent with activities in and around the disposal site at the time of site closure. These scenarios should be detailed in guidance documents.”