Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Transuranic Waste Inventories The first part of this chapter discusses different types of transuranic (TRW) waste in the U.S. Department of Energy (DOE) inventory. Transuranic waste is defined in Chapter 1, Sidebar 1.2. In the second part of this chapter, the committee identifies challenging waste streams that will have to be characterized prior to disposal in the Waste Isolation Pilot Plant (WIPP). Some waste streams without a clear path for disposal may become characterization challenges should they be sent to WIPP. 2~1 Existing Waste and To-Be-Generatec' Waste The Department of Energy classifies its TRU waste inventories as "legacy" (also callecl "retrievably stored") waste or "newly generated waste" according to its generation period. Legacy waste was produced after 19704 but prior to implementation of the acoroved contact-handed transuranic (CH-TRU) waste characterization program.2 According to DOE's definition, newly generated TRU waste is waste yet-to-be generated, sometimes referred to as "projected waste" (see Table2.~), curing ongoing production, research activities, or deactivation and decommissioning activities; or existing waste that has to be re-packaged in a suitable form for transportation and disposal. The Department of Energy's terminology is potentially confusing because newly generated waste refers to both waste that does not yet exist and existing waste (needing repackaging). In this report, the committee uses the terms "to-be-generated" and "existing" waste to distinguish between waste that will be generated in the future and stored waste (whether already packaged or to be re-packaged). The historical information associated with existing waste must be confirmed (or "qualified") according to procedures set forth by the U.S. Environmental Protection Agency (EPA) and the New Mexico Environment Department (NMED), as exp~ainecl in Chapter 4. For to-be-generated waste, characterization information is collected at the time of waste generation; therefore, if an approved quality assurance plan is in place, the Prior to 1970, most TRU waste was disposed of by burial in shallow earth trenches using operations similar to those used in low-level waste disposal facilities. In 1970, the Atomic Energy Commission, the predecessor of DOE, determined that radioactive waste contaminated with transuranic isotopes with a concentration of alpha emitters greater than 10 nanocuries per gram of waste should receive greater confinement from the environment. Since that time, TRU waste has been segregated from other types of waste and placed in interim (retrievable) storage until it can be shipped for final disposal in a geologic repository. In 1982, DOE raised the threshold concentration for defining TRU waste to 100 nanocuries per gram. This report does not specifically address pre-1970 buried TRU waste. 2EPA approved the waste characterization program for CH-TRU waste in 1998, and the New Mexico Environment Department approved that for mixed CH-TRU waste in 1999. 18
Transuranic Waste Inventories 19 characterization information should meet the requirements set forth by regulators and does not have to be confirmed. This distinction is important for the discussion about Acceptable Knowledge in Section 4.4. 2.2 Transuranic Waste Inventories According to DOE's latest inventory estimates, approximately ~ 90,000 cubic meters of CH-TRU waste and 3,800 cubic meters of remote-handled transuranic (RH- TRU) waste need to be removed from 27 DOE sites across the nation (DOE-NTP, 2002~. The TRU waste generator sites are listed in Table 2.~; the 5 largest sites (Hanford, Idaho National Engineering and Environmental Laboratory, Los Alamos National Laboratory, Savannah River, and Rocky Flats Environmental Technology Site3) are responsible for 96 percent of stored and projected volumes of CH-TRU waste. The inventory of legacy CH-TRU waste (labeled "stored waste" by DOE in Table 2. ~ ~ amounts to approximately ~ ~ 0,000 cubic meters, whereas the volume of to-be- generated waste (labeled "projected" waste) is estimated to be approximately 76,000 cubic meters. Of the 110,000 cubic meters of legacy CH-TRU waste, 15,000 cubic meters have already been emplaced in W! PP, leaving approximately 95,000 cubic meters of legacy waste to be characterized and disposed. Most of the to-be-generated waste will come from sites in Hanford, Idaho, Los Alamos, Savannah River, and Rocky Flats (DOE-TWBIR, 1996~. The total radioactivity estimated at the time of WIPP closure in 2035 from CH-TRU waste is approximately 6.4 million curies as shown in Table 2.2.4 DOE has programs for the characterization, shipment to, and disposal at WIPP of most existing TRU waste. However, in the future, some "challenging" waste streams may pose characterization difficulties, as described below. 2.3 Challenging Waste Streams Destined for WIPP Some of the CH-TRU waste yet to be characterized may present challenges because of a potential for generating flammable gas, oversize containers, fissile isotope content, possible presence of respirable aerosols, prohibited items, high dose rates, or the difficulty of retrieving buried waste. The following description of challenging waste streams was developed from material provided by DOE (Moody and Nelson, 2003) and information gathered in open meetings. 2.3.1 Waste with high potential for generating flammable gas Heat-generating CH-TRU waste in DOE's inventory presents a potential for generating flammable gas by radio~ysis. Heat generated within waste by radioactive decay is primarily an inclicator of the alpha-emitting radionuclide content of the waste and is used as a surrogate for actual measurements of flammable gas for transportation purposes. Alpha-emitting material in high concentrations and amounts of high specific radioactivity, such as plutonium-23S, can generate flammable gases (e.g., hycirogen) in the presence of a hydrogen source, such as water or plastic, by destroying the chemical boncis that hold the hydrogen atom.5 Therefore, the concentration of flammable gases generated during shipping must be predicted by calculation and maintained below flammable limits. 3The Rocky Flats Technology Environmental Site and the Idaho National Engineering and Environmental Laboratory have priority in shipping TRU waste for disposal at WIPP because of agreements between DOE and the States of Colorado and Idaho, respectively. 4DoE plans to release an update of waste inventories by the end of 2003. 5Corrosion of steel drums or other reactive metals in the presence of water can also release hydrogen gas over long periods of time.
20 Improving the Characterization Program for Contact-Handled Transuranic Waste In at_ ._ cn at_ a) a) en ._ In o ._ o in' o at_ > at_ In 2 - n ~ a) Q I) O {~ - .m a) E ._ n c' a) _' In O Q ·m o > In 2_ _ ~ .o 0 In cut n a) _ ~ ·_ ~ 2 I Q at_ o () ~ o cn o ._ _ Z at_ ._ cn ~ ~ CD ~ ~ ~ ~ · . . . . . . o o o ~ ~ oo C~ o ~ C5) o ~ o o o o ~ o o ~ o ~ o C~ ~ c~ r~ ~ cY) CD CO ~ C~ ~ CO CO C~ CO 0 0 0 0 0 0 0 0 0 C5) o 0 0 0 0 ~ 0 0 0 0 0 0 0 0 C~ ~ ~ CO ~ ~ ~ ~ ~ C~ CY) ~ CO ~ . . . . . . . · · . . . O ~ 00 00 ~ 00 C~l O lS-) N O C~ l U) ~) ~ ~ ~ ~) CY) ~t C~l ~) ~) ~ ~ C\l ~ ~) ~ a) O ~ d. O C~l ~) O C~J ~) O C~l CO ~ C~l ~ O ~ ~ _ _ ~ _ _ _ C~ ~ ~ O CO C~ C~ C~ cn O ~ CO O O O O O ~ O O C~ CO CN1 a) C~l 0~) _ _ ~ ' CO ~ ~ ~ CO CY) . . . . . . . O c0 0 00 ' ~ C~ O 00 ~ ~ CN _ _ ~ CO Ln C0 . . O ~ CO ~ O O ~ O O LD O ~ ~ ~ CO ~ 00 0 N ~ O C~ O _ ~ ~ ~ ~ C~ ~ ~ . · · . · - O O ~ ~ O O ' ~ ~ CY) ~ ~ c0 ~) a) C5) ~ O ~) ~) C~l C~ ~ ~ ~ ~ _ _ CD ~ ~ O ns ~ ~ ~ ~ ~ ~ ~ t S S ~ ~ ~ ~ ~ S S ~ ~ ~ ~ , 3 ~ m m m ~ ~ r ~ ~ Y Y cn ~ ~ ~ ~ ~ ~ z 0 ~ ~ cn
Transuranic Waste Inventories m. m~ 0 0 Hi 0 ~ 0 ° i ~ 0 . . 0 0 0 cat co ~ co us cot co . . . 0 cot co oo cc co oo a) :5 . - ~n O O CD 00 co ~ 1 ~ cot co co 0 Hi ~ up 0 0 21 ~ ~ ~ ~ ~ ~ 0 ~ g; (P ~ j: Al ~ ; O ~ C a) O <,~,o~ ~ A._ ~ Hi,- . j; ~ ~ ~~: i~ :E :~
22 ~ ~ . improving the Characterization Program for Contact-Handled Transuranic Waste Table 2.2 Estimated Inventory of Major Radionuclicles in Contact- HandIed Transuranic Waste for Disposal at the Waste Isolation Pilot Plant Radionuctide Curies (Ci) _ 442,000 31,500 2,61 O,000 785,000 210,000 1,170 Americium-241 Curium-244 Plutonium-238 Plutonium-239 Plutonium-240 Plutonium-242 Total alpha-emitting radionuclides Barium-137m Cesium-137 Plutonium-241 Strontium-90 Yttrium-90 Total beta-emihing radionuclides Uranium isotopes (232-238) Total CH-TRU waste curies SOU ROE: DOE-TWBI R. 1996. 4,080,000 7,630 8,060 2,310,000 6,850 6,850 2,340,000 2,400 6,420,000 To ensure safe transport of the payload containers in a TRUPACT-II package, the U.S. Nuclear Regulatory Commission (USNRC) has imposed a limit on the concentration of hydrogen within the innermost layer of confinement of a drum or a standard waste box.6 High-heat waste generally contains plutonium-238, which has a high specific alpha activity or large amounts of plutonium-239.7 Approximately 2,900 cubic meters, or 2 percent of the volume, of CH-TRU waste is not readily shippable to WIPP because it is calculated to exceed gas generation limits set by the USNRC (this waste is referred to as "high-heat" TRU waste). This includes drums containing plutonium-238 and plutonium-239 wastes that are located principally at four sites: Savannah River Site, loos Alamos National Laboratory, Idaho National Engineering and Environmental Laboratory, and Rocky Flats Environmental Technology Site. Prior to a recent revision, approximately 2,000 drums containing high concentrations of plutonium at the Los Alamos National Laboratory would have required repackaging into at least 20,000 drums to meet the current heat generation limits of the TRUPACT-~. A revision to the TRUPACT-~! Certificate of Compliance provided a means for reducing the shipping period from the loos Alamos National Laboratory to WIPP from 60 days to 5 days, thereby avoiding repackaging about 90 percent of this waste (see 6The limit set by the USNRC is 5 percent by volume of hydrogen generated in the drum air during the shipping period. High heat could also be produced by spontaneously fissioning radionuclides, such as californium-252, and by curium isotopes. However, these radionuclides are present only in trace amounts in CH-TRU waste.
Transuranic Waste Inventories 23 Chapter 3~. Inventory analyses at the Savannah River Site indicate that 3,122 drums (650 cubic meters) out of a population of 9,688 drums of debris waste contaminated with plutonium-238 exceed 0.8 grams of plutonium-238 per drum and therefore may exceed heat generation limits for TRUPACT-~! as currently packaged. A potential hydrogen generation issue may also impact the shipment of 4,469 cubic meters of plutonium-238 waste in oversized boxes at the Savannah River Site (see below). Large amounts of plutonium-239 or plutonium-238 in waste pose characterization challenges when waste containers must be opened and the contents visually inspected and repackaged. In particular, according to DOE, plutonium-238 waste poses a challenge because it is liable to form respirable aerosols, both of fine plutonium-238 oxide particles and of organic materials (e.g., plastic bags) that have been in contact with plutonium-238. Because of the processes used to produce them, plutonium-238 wastes tend to be fine particulates (probably less than 2.5-micrometers average diameter) that can spread by alpha recoil or drafts of air. At high concentrations, the high specific heat generation rate of plutonium-238 may cause charring of any organic material that it contacts. Thus, characterization activities that require breaching a waste container (e.g., headspace gas sampling or direct visual examination) may pose a threat of contamination at the generator's site and potential worker exposure even if secondary containment (gIovebox) is used. Airborne dispersal of plutonium-238 through the filters may also be possible. ~ I J ~ 2.3.2 Oversized containers Approximately 40,000 cubic meters of CH-TRU waste is estimated to exist in oversized containers (e.g., 3.7 x 2.1 x 5.5 meters or 12 x 7 x 18 feet boxes) that are not transportable in USNRC-approved shipping containers. Current technologies used for non-destructive examination and assay of waste in 55-gallon drums have not been validated on waste stored in oversize containers. This implies that these boxes may have to be opened and the contents handled manually for characterization if non- destructive assay and examination methods do not become available for oversized boxes.8 Approximately half of the volume of waste in oversize containers is at the Idaho National Engineering and Environmental Laboratory and is destined for on-site size reduction (primarily by compaction) and repackaging et the newly-constructed Advanced Mixed Waste Treatment Facility, when it becomes operational. The rest of the oversized boxes of TRU waste are stored primarily at Hanford, Savannah River Site, Los Alamos National Laboratory, Nevada Test Site, and Lawrence Livermore National Laboratory. Some wastes in oversized containers are also not shippable due to size and weight constraints on WIPP shipments. Because approximately 95 percent of the oversized waste inventory is packaged in rectangular boxes that are less than 1.5 x 1.5 x 2.4 meters (5 x 5 x ~ feet), DOE has initiated the design, testing, and licensing of the TRUPACT-~! transportation package in a configuration that could easily accommodate a box of this size without the need to repackage (see Chapter 3~. According to DOE, the TRUPACT-~! configuration will exceed the allowable highway shipping weights so that exemptions from USNRC requirements may be needed. 2.3.3 Fissile isotope content There are limits on the quantity of fissionable materials in shipping containers to prevent criticality. These limits may restrict the average fissile gram equivalent per payload container and result in additional shipments. This is the case for 56 drums WOE is also currently planning a request for proposals to develop and demonstrate non- destructive assay and examination methods for oversize containers.
24 Improving the Characterization Program for Contact-Handled Transuranic Waste (approximately 12 cubic meters) out of a population of 16,410 drums of debris waste at the Savannah River Site. This waste is contaminated with plutonium-239 and may require repackaging in order to meet current TRUPACT-~! limits (200 grams per drum). These characterization challenges are the same as those for high-heat waste, namely potential worker exposure to radiation or contamination during repackaging. 2.3.4 Legacy waste generated in research laboratories Although most of CH-TRU waste was generated at "production" sites, some waste streams originated from laboratories such as the Idaho National Engineering and Environmental Laboratory that processed spent fuel and conducted related research. Records of these small, specialized waste streams from research operations are not as complete as those kept at production sites, where the waste processes were well established and good-quality records were usually maintained. Moreover, some of this laboratory waste is potentially more hazardous than production waste because of its experimental nature. go. 2.3~5 Prohibitec! items Some wastes, such as of! and solvent immobilization system (OASIS) waste and other organic waste sludges, sealed sources, or heat-sealed bags greater than 4 liters in volume, cannot be shipped to WIPP due to the presence of prohibited items. 2.3. 5. ~ OASIS and other organic s/uc/ge wastes OASIS wastes are organic sludge wastes that resulted when spent cubing fluids and solvents from plutonium machining operations were solidified with gypsum cement. These wastes will be difficult to radiograph, and visual examination would be meaningless. Further, non-destructive assay may be rendered more difficult by the presence of cement. Part of the OASIS waste at the Rocky Flats Environmental Technology Site was solidified with gypsum cement and shipped to the Idaho National Engineering and Environmental Laboratory in the 1970s. Subsequently, the Rocky Flats Environmental Technology Site generated additional drums from the same process and stored the waste on site. There are approximately 2,200 cubic meters of organic sludge at the Rocky Flats Environmental Technology Site and Idaho National Engineering and Environmental Laboratory combined (Moody et al., 2003~. Headspace gas samples from these waste streams at the Rocky Flats Environmental Technology Site and the Idaho National Engineering and Environmental Laboratory show that most of this waste fails transportation requirements for flammable gases, mainly hycirogen, and/or fails gas generation testing due to total gas generated. 2.3.5.2 Sea/ec/ sources More than 5~000 sealed radioactive sources,9 with an eventual projection of 18,000 to be recovered, have been catalogued at Los Alamos National Laboratory. Los Alamos National Laboratory developed a packaging configuration for a variety of waste streams, including sealed sources, called the '~pipe component." This consists of a robust stainless steel inner cylinder overpacked with a standard 55-gallon drum, with a range of shielding options depending on the nature of the radioactive materials. Characterization requirements for these drums are not yet finalized. However, if headspace gas analysis must be performed on the pipe component, personnel exposure may result. The sealed sources themselves are not a source of flammable gases. Although not a characterization issue, a further challenge presented by this waste is that 9Some of the sealed sources could be classified as RH-TRU waste.
Transuranic Waste Inventories 25 only 5 percent (equivalent to approximately 100 drums of TRU waste) comes from defense applications. Hence, the remaining 95 percent cannot be disposed at WIPP without a change in federal law to permit the disposal of non-defense TRU waste. 2.3.5.3 Wastes containing heat-sea/ed bags Any sealed container greater than 4 liters inside a waste drum is considered a prohibited item and precluded from shipment to and disposal at WIPP. Real-time radiography, one of the characterization methods used to detect prohibited items in waste drums, cannot detect heat seals. Therefore, the safety concern is that, if the seated bag cannot be removed or breached before it is shipped to WIPP, hydrogen may accumulate. Several sites historically employed heat-sealed bags in plutonium operations. The Hanford Site identified 3,000 drums containing such bags. 2.3~6 Remote-hancllec! transuranic wasted Characterizing RH-TRU waste is challenging because of the higher surface dose rates of waste containers. When working with RH-TRU waste, additional radiation safely measures will be required to maintain worker doses as low as reasonably achievable (ALARA). Although RH-TRU comprises only 2 to 4 percent by volume of total TRU waste, it represents 13.5 percent by radioactivity at time of emplacement. Up to 5 percent by volume of RH-TRU waste is permitted to have a surface dose rate as high as 1,000 rem per hour, and 95 percent may have between 200 mrem and 100 mrem per hour. Remote-handIed TRU waste is currently not authorized for disposal at WIPP because EPA and NMED have not approved a characterization plan for this type of waste. EPA, NMED, the New Mexico Environmental Evaluation Group, and a previous National Research Council committee have expressed concerns that characterization methocis used for CH-TRU waste, such as real-time racliography, non-destructive assay, or non-destructive examination methods, may not be effective in the presence of the high-gamma, neutron, bremsstrahfung, or X-ray fields created by RH-TRU waste (EEG, 1994; EPA, 1998; NMED, 1999; NRC, 2002~. RH-TRU waste exists as a number of specialized, smalI-scale waste streams that may call for new equipment or for procedures that differ significantly from those used in the usual waste characterization processes. Remote-handIed TRU waste with a surface dose rate greater than 1,000 rem per hour may also become a challenge in the future. The WIPP Land Withdrawal Act established an upper limit for the surface dose rate for RH waste of 1,000 rem per hour; therefore, any TRU waste that produces more than 1,000 rem per hour cannot be sent to WIPP. To date, there has been no official inventory of the quantity of RH-TRU waste falling into this category. 4°AIthough RH-TRU waste characterization is outside this study's statement of task, it is briefly discussed in this section as a potential characterization challenge. SHOE is interacting with NMED and EPA to submit a new characterization plan for RH- TRU waste. In June 2002, DOE submitted a permit modification request to NMED to receive and dispose of RH-TRU waste in WIPP. In May 2003, DOE submitted a revised permit modification request in response to NMED's notice of deficiency (NMED, 2003a). NMED is currently reviewing the revised proposal. In April 2003, DOE submitted a formal proposal to EPA to modify WlPP's Certification and, in September 2003, a revised proposal was submitted in response to EPA's comments. EPA is currently reviewing the revised proposal.
:~. 26 Improving the Characterization Program for Contact-Handled Transuranic Waste 2~4 Challenging Waste Streams without a Clear Path for Disposal In its National TRU Waste Management Program, DOE recognizes that there are about 9,600 cubic meters of TRU waste without a current plan for disposal (DOE-NTP, 2002~. These are wastes contaminated with reactive or corrosive substances and TRU waste generated from non-defense activities. The committee also identifies TRU waste buried prior to ~ 970 as a challenging waste stream. DOE estimates that 126,000 cubic meters of TRU wastes were disposed by shallow-tand burial at various DOE sites, particularly at the Idaho National Engineering and Environmental Laboratory, prior to 1970. No decision has been made whether to exhume the wastes for deep geologic burial at WIPP or any other site (DOE-EM, 2000~. If so, characterization would be required before disposal.42 42The New Mexico Environmental Evaluation Group has recently released a report concerning buried TRU waste, including future characterization needs (EEG, 2003a).
