WIPP RH-TRU Waste Study - Summary
This study was prepared by the Department in fulfillment of a
congressional mandate specified in Public Law 102-579, referred
to as the Waste Isolation Pilot Plant Land Withdrawal Act.
In addition, the Department considers the preparation of the study
to be a prudent element in the compliance certification process
for the Waste Isolation Pilot Plant (WIPP). The study includes
an analysis of the impact of remote-handled Transuranic waste
on the performance assessment of the WIPP and a comparison of
remote-handled Transuranic waste with contact-handled Transuranic
waste on issues of gas generation, flammability, explosiveness,
solubility, and brine and geochemical interactions.
The "Department of Energy National Security and Military
Applications of Nuclear Energy Authorization Act of 1980"
(Public Law 96-164) authorized the Department of Energy (DOE)
to develop a research and development facility to demonstrate
the safe disposal of radioactive waste generated by national defense
activities. The WIPP is required to meet the statutory requirements
of Public Law 96-164.
TRU waste is waste that contains alpha particle-emitting radionuclides
with an atomic number greater than that of uranium (92), half-lives
greater than 20 years, and concentrations greater than 100 nanocuries
per gram of waste. TRU waste is classified according to the radiation
dose rate at a package surface. Contact-handled (CH) TRU waste
has a radiation dose rate at a package surface of 200 millirem
per hour or less; this waste can be safely handled directly by
personnel. Remote-handled (RH) TRU waste has a radiation dose
rate at a package surface of 200 millirem or greater per hour
but not more than 1,000 rem per hour; this waste must be handled
remotely (i.e., with machinery designed to shield the handler
from radiation). Alpha radiation is the primary factor in the
radiation health hazard associated with TRU waste. Alpha radiation
is not energetic enough to penetrate human skin but poses a health
hazard if it is taken into the body (e.g., inhaled or ingested).
In addition to alpha radiation, TRU waste also emits gamma and/or
beta radiation, which can penetrate the human body and requires
shielding during transport and handling. RH-TRU waste has gamma
and/or beta radiation emitting radionuclides in greater quantities
than exist in CH-TRU waste.
Before 1970, material that is now classified as contact-handled
TRU waste was not segregated from low-level waste and was buried
along with low-level waste. At the time of burial, the DOE did
not intend to retrieve that waste. Since the Atomic Energy Commission
(one of the DOE's predecessor agencies) adopted a policy requiring
retrievable storage of certain waste containing Transuranic radionuclides
in 1970, DOE TRU waste has been stored in containers so that it
could be easily retrieved when future decisions were made regarding
the management or disposition of this waste. About 55 percent
of the Department's current TRU waste inventory contains hazardous
substances regulated under the Resource Conservation and Recovery
Act. The fraction of TRU waste streams that contains hazardous
substances is expected to decrease in the future due to DOE pollution
In 1992, Congress passed Public Law 102-579, the "Waste Isolation
Pilot Plant Land Withdrawal Act" (LWA) which withdrew the
land on which the WIPP is situated from public use and transferred
jurisdiction over the site from the Secretary of Interior to the
Secretary of Energy.
Although the DOE is now conducting experiments in laboratories,
at the time the LWA was passed, DOE planned on performing experiments
with TRU waste in excavated rooms in the WIPP underground. The
LWA limited experiments in the underground to those with small
quantities of CH-TRU waste during the planned test phase. The
repository tests were abandoned in October 1993. Tests are currently
planned at INEL using actual TRU wastes to evaluate waste performance
under potential repository conditions.
The LWA prohibits RH-TRU waste at the facility until a decision
is made to use WIPP as a permanent repository. However, section
6(c)(2)(B) of the LWA requires a study to evaluate the effects
of RH-TRU waste on performance assessment of the WIPP. The LWA
also requires the study to compare the two waste types in the
areas of gas generation, flammability, explosiveness, solubility,
and brine and geochemical interactions. In addition, the LWA requires
the study to be completed within three years of the date of enactment
(October 30, 1992), be conducted in consultation with states affected
by WIPP and the Administrator of the EPA. Views were also solicited
from other interested parties. Review comments from the affected
states, the Administrator and other interested parties on the
RH-TRU waste study Implementation Plan and on a draft report of
the RH-TRU waste study helped improve the quality of the final
Scope of Study
The Remote-Handled Transuranic Waste Study has been conducted
in accordance with section 6(c)(2)(B) of the LWA. The study evaluates
the impact of RH-TRU waste on the performance assessment of the
WIPP baseline configuration. In addition, the study also compares
the characteristics of CH-TRU and RH-TRU waste as expected to
be received at WIPP as well as the potential affects of the wastes
on gas generation, flammability, explosiveness, solubility and,
brine and geochemical interactions after emplacement in the WIPP
underground. The Remote- Handled Transuranic Waste Study does not include an analysis of RH-TRU waste characteristics on
the transportation and operational aspects of the WIPP program.
The Remote-Handled Transuranic Waste Study has three main
sections: the Transuranic waste disposal strategy; comparison
of contact-handled and remote-handled Transuranic wastes; and
analysis of the impact of remote-handled waste on performance
In the section on the Transuranic waste disposal strategy, elements
of the WIPP baseline configuration considered to be important
for the study are described. These elements include: room configuration,
waste packaging, RH-TRU waste emplacement and shield plugs, and
the physical and radiological characteristics of the TRU inventory.
The comparison section of the study includes two areas of evaluation.
These include a comparison of CH-TRU and RH-TRU waste characteristics
as expected to be received at the WIPP and a comparison of CH-TRU
and RH-TRU waste after emplacement in and closure of the WIPP
underground. In the latter area of evaluation, the study specifically
addresses the issues required by the LWA: gas generation, flammability,
explosiveness, solubility, and brine and geochemical interactions.
In the last section of the study, the impact of RH-TRU waste on
performance assessment is evaluated. Four radionuclide release
scenarios are identified for evaluation: releases by gas generation,
groundwater transport, human intrusion and heat generation.
A summary of the important findings of the Remote-Handled Transuranic
Waste Study include the following:
The contribution of RH-TRU waste to the total radioactivity
in TRU waste will be insignificant after about 200 years following
emplacement in the WIPP. RH-TRU waste has a greater abundance
of those radionuclides that characteristically have more penetrating
radiation and more specific radioactivity, but these radionuclides
also have rapid decay rates and short half-lives reducing their
contribution to the radioactive component of TRU waste to a short
period of time (200 years). By contrast, the majority of the radionuclides
in CH-TRU waste have less specific radioactivity, but decay at
a much slower rates.
RH-TRU waste contributes only a small portion to the total
TRU waste inventory because the "Agreement for Consultation
and Cooperation with DOE and the State of New Mexico on WIPP"
(1981) restricts the quantity to only 5 percent by volume. In
addition, RH-TRU waste is composed of the same materials as CH-TRU
waste because they are derived from similar processes. Therefore,
the impact of RH-TRU waste on performance assessment is insignificant.
No significant accumulations of gas pressure, or flammable
or explosive gases are anticipated in "as-received"
waste at the WIPP for the following reasons:
WIPP Waste Acceptance Criteria requires containers to be vented
to allow pressure to be relieved from the containers during transportation;
The WIPP Waste Acceptance Criteria sets strict limits on the
amounts of liquids and flammable gasses allowed in WIPP waste,
WIPP Waste Acceptance Criteria prohibits any explosive materials
from being in the waste.
The presence of brine in the WIPP underground can impact the
total amount of gas generated by influencing the mechanisms that
cause waste decomposition. The degree to which gas generation
occurs depends on the amount of brine present in the WIPP underground
and the point in time in the decomposition process brine encounters
The decomposable materials in RH-TRU waste can contribute
up to about 31 percent of all potential gases that may be generated
in the WIPP underground.
RH-TRU waste contains about 13 percent of the portion of TRU
waste materials that can potentially generate flammable gases.
The additional curies of radioactivity introduced into the
repository by RH-TRU waste will not impact the overall TRU waste
inventory solubility. The reason for this is that the gamma emitters
in RH-TRU waste will decay to levels approximating those in CH-TRU
waste before the waste containers degrade and allow interactions
with brine (about 200 years following WIPP closure).
The effects of heat and radiation from RH-TRU waste on the
WIPP underground are expected to be minimal. Because the Waste
Acceptance Criteria restrict the radiation doses and heat allowed,
only a small portion of the WIPP underground will be irradiated
and any thermal gradients produced will be insignificant.
Long travel times, as predicted by modeling studies, are required
for brine to reach a regulatory boundary. Therefore, it is highly
unlikely that gamma-emitting radionuclides from RH-TRU waste would
be part of a release to the accessible environment due to groundwater
migration since the rapid decay rates of these radionuclides result
in much smaller quantities after a relatively short period of
time (200 years).
Gamma-emitting radionuclides in RH-TRU waste can have little
or no contribution to releases caused by human intrusion activities
because their rapid decay rates result in much smaller quantities
after a relatively short period of time (200 years).
Studies to evaluate the effects of heat on repository performance
have shown that at expected levels of waste package heat output,
insufficient heat will be available to influence WIPP performance.
Two major conclusions can be drawn from the findings of the Remote-Handled
Transuranic Waste Study: (1) RH-TRU waste has no significant
impact or influence on the outcome of performance assessment and
(2) RH-TRU waste is similar to CH-TRU waste in terms of its characteristics
as expected to be received at WIPP and in its behavior in the
Issued in Carlsbad, New Mexico, this 11 day of October, 1995,
for the United States Department of Energy.
ADDRESSES: To obtain a copy of the Remote-Handled Transuranic
Waste Study (Document Number DOE/CAO 95-1095) telephone the
WIPP Information Center at 1-800-336-9477. In addition, copies
of the Remote-Handled Transuranic Waste Study are available
for inspection at WIPP reading rooms.
FOR FURTHER INFORMATION CONTACT: Written questions and
comments should be directed to: George Basabilvazo, Carlsbad Field Office, U.S. Department of Energy, P.O. Box 2078, Carlsbad,
New Mexico 88220.
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