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OCR for page 18
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
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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.
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20 Improving the Characterization Program for Contact-Handled Transuranic Waste
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Transuranic Waste Inventories
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OCR for page 22
22
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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.
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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.
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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.
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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.
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:~.
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).
Representative terms from entire chapter:
cubic meters
