[DNFSB
LETTERHEAD]
March 10, 2005
The Honorable Samuel W. Bodman
Secretary of Energy
1000 Independence Avenue, SW
Washington, DC 20585-1000
Dear Secretary Bodman:
On March 10, 2005, the Defense
Nuclear Facilities Safety Board (Board), in accordance with 42 U.S.C. § 2286a(a)(5),
unanimously approved Recommendation 2005-1, Nuclear Material Packaging, which is enclosed for your
consideration. This recommendation
addresses issuance of a requirement that nuclear material packaging meet
technically justified criteria for safe storage and handling outside of
engineered contamination barriers.
After your receipt of this
recommendation and as required by 42 U.S.C. § 2286d(a), the Board will promptly make it available to the
public. The Board believes that the recommendation
contains no information that is classified or otherwise restricted. To the extent this recommendation does not
include information restricted by the Department of Energy (DOE) under the
Atomic Energy Act of 1954, 42
U.S.C. §§ 2161-68,
as amended, please arrange to have it promptly placed on file in your regional
public reading rooms. The Board will
also publish this recommendation in the Federal Register. The Board will evaluate DOE’s response to this
recommendation in accordance with Board Policy Statement 1, Criteria for Judging the Adequacy
of DOE Responses and
Implementation Plans for Board Recommendations.
Sincerely,
John T. Conway
Chairman
Enclosure
c: Mr. Mark B. Whitaker, Jr.
RECOMMENDATION
2005-1 TO THE SECRETARY OF ENERGY
Pursuant
to 42 U.S.C. §
2286a(a)(5),
Atomic
Energy Act of 1954, As Amended
Dated: March 10, 2005
Background
In Recommendation 94-1, Improved Schedule for Remediation in the
Defense Nuclear Facilities Complex, the Defense Nuclear Facilities Safety Board (Board) urged
the Department of Energy (DOE) to improve the packaging and storage conditions
of its large inventory of nuclear materials once used for weapons manufacture. In particular, the Board recommended that DOE
place plutonium metals and oxides in storage configurations meeting DOE’s
standard for long-term storage (DOE-STD-3013-2004, Stabilization, Packaging,
and Storage of Plutonium-Bearing Materials). Some sites applied Recommendation 94-1 to excess materials only.
The Board has continued to evaluate
whether other categories of nuclear materials are stored in a safe manner.
DOE has made progress in the
stabilization and storage of its excess nuclear materials. The storage requirements for
other categories of nuclear materials, however, are not as well defined and
controlled. Specifically, DOE Order 5660.1B,
Management
of Nuclear Materials, does
not address safe storage requirements. Other than two narrowly focused standards―DOE-STD-3013-2004 and
DOE-STD-3028-2000, Criteria
for Packaging
and Storing Uranium-233-Bearing Materials―there
are no explicit
DOE-wide requirement to ensure the safe storage of nuclear materials. Currently, the technical adequacy of
packaging-the combination of containers and other components providing a
contamination barrier-for nuclear materials, including liquids, is dependent on
the safety bases of individual facilities. Typically, facilities have credited engineered
features, such as the confinement structure and ventilation system, for protecting
offsite individuals and collocated workers. For facility workers, however, the controls are
generally administrative, such as continuous air monitors, personal protective
equipment, periodic contamination surveys, and other aspects of the
radiological control program, in conjunction with proper evacuation training. In accordance with DOE Standard 3009, Preparation Guide for U.S. Department of Energy Nonreactor Nuclear
Facility Documented Safety Analysis (DOE-STD-3009-94, Change Notice 02), accidents that pose the
risk of significant radiological exposure to workers, such as a breached
nuclear material storage package, should be prevented or mitigated using
safety-significant controls. The
preferred hierarchy of controls favors engineered, preventive features over
administrative controls.
Establishing packaging
requirements for nuclear materials within the DOE complex requires
consideration of a diverse population of material types for storage for
uncertain periods of time. From a safety
standpoint, nuclear material packaging must protect against a number of challenges
that could breach the container and release radioactive material. Many of the materials of concern generate
gases that result in container pressurization and may be pyrophoric or highly
reactive. The container design must take
into account corrosion, oxidative expansion of stored metal, effects of
radiolysis, diurnal pumping and damage due to impacts from drops and tooling
during handling. The Board’s recent
review of nuclear material packaging at Lawrence Livermore National Laboratory
(LLNL) revealed that many of these insults had not been fully considered when
packaging choices were made for nuclear materials not covered by Recommendation
94-1. In fact, many of these current
packaging configurations are similar to the inadequate configurations addressed
in Recommendation 94-1, and are documented as being susceptible to eventual
failure in the report of the Recommendation 94-1 Materials Identification and
Surveillance Working Group, entitled Summary of Plutonium Oxide and Metal Storage Package Failures (LA-UR-99-2896).
In general, the hazards posed by
nuclear materials covered under DOE’s Implementation Plan for Recommendation
94-1 are the same as those for nuclear materials not considered excess. When nonexcess materials are removed from
glovebox confinement for interim storage, relocation to another work station,
assay, or other purposes, the packages are susceptible to the same types of
failures as those addressed in Recommendation 94-1. The longer the materials are stored, the
greater are the chances that the packaging will fail, especially if the
packaging has not been designed appropriately for the actual duration of
storage. The Board found that approximately
15 percent of the nonexcess items at LLNL’s Plutonium Facility are stored in packaging
more than 5 years old. Some of
the older items, previously declared excess, remain in their existing packaging
while awaiting stabilization and packaging under DOE-STD-3013-2004. This situation emphasizes the need to
establish a technical basis for packaging, such as designating the time period
for which a particular container is confirmed to perform its function adequately,
in conjunction with tracking the age of containers in use.
Two recent events serve as further
reminders of the importance of using packaging that is properly designed for
its function:
State of Nuclear Material
Packaging
DOE-STD-3013-2004 sets forth
requirements for a robust storage configuration for long-term storage of
plutonium-bearing materials. The
requirements ensure containment through a combination of material form,
packaging design, and surveillance of containers. However, the robust, welded configurations in
the standard may not be desirable when a short storage period is anticipated
pending use of the material.
There are no equivalent
requirements for interim storage. As
part of its response to Recommendation 94-1, DOE finalized
guidance for the storage of plutonium-bearing materials not packaged for
long-term storage under DOE-STD-3013. This guidance, identified in a January 25,
1996, memorandum from Deputy Secretary of Energy Curtis entitled Criteria for Interim Safe
Storage of Plutonium-Bearing Solid
Materials, provides
a technically justified approach to safe packaging and storage of
plutonium-bearing materials for a period of up to 20 years. Although these Interim Safe Storage Criteria
(ISSC) were not intended to apply to materials in working inventory, much of
the guidance remains germane to storage of all nuclear materials outside of
approved engineered contamination barriers (e.g., gloveboxes or certified shipping
containers).
The ISSC were only implemented
for selected excess materials and were never formally issued as part of the DOE
Directives System. In practice, the
sites use a wide variety of packages, many of which do not meet the ISSC. According to the lessons learned from the DOE Type
B investigation of the worker uptakes at LANL, packages containing radioactive
material should be assumed unsafe until proven otherwise or the materials are
repackaged to current standards. Yet
sites continue to rely on container types that have been used historically, but
have no technically justified safety or design basis. These container types are generally forms of packaging
typically used in non-nuclear applications (e.g., paint cans, food pack cans). Thus, they are not designed to protect against
the hazards of the nuclear materials they contain for the duration of storage.
Several commonly used containers
and their potential inadequacies are briefly summarized in an attachment to
this Recommendation. Many other
containers are in use for specialized applications.
Remaining Problems
In response to the Board’s May
20, 2002, correspondence on safety of nuclear materials storage, the National
Nuclear Security Administration (NNSA) established the Inactive Actinide Working
Group (IAWG), with the goal of developing a comprehensive approach to the characterization,
packaging, and storage of a subset of nuclear materials. As presented in a February 7, 2003, letter
from NNSA to the Board, the IAWG was to meet this goal through the development
of three strategies for the following: acceptance
and retention of nuclear materials, material characterization and storage
adequacy, and disposition. The Board has
been observing the IAWG’s efforts and has made three observations.
First, a key product of the IAWG
effort will be the strategy for material characterization and storage adequacy.
Based on discussions with IAWG
participants, the delivery of this strategy has been delayed, in large part
because of disagreements among member sites on the requirements necessary for
justifying adequate storage. The Board
believes these requirements should provide for sufficient characterization
based on an appropriate combination of analysis and process knowledge to
determine the appropriate packaging. Characterization information should also be
used to develop a surveillance program prioritized according to expected
material and container risk (including, for example, material type, material
form, and the age and type of container).
Second, in a June 2000 report
entitled A
Strategic Approach to Integrating the Long-Term Management of Nuclear
Materials, DOE
recognized the need to update the existing DOE Order on nuclear materials
management. In particular, this report
urged improvements to the nuclear materials management process. However, neither the current Order nor the
report explicitly considers storage safety. The Board believes that DOE should require a
technical basis for nuclear material packaging and storage safety. Efforts to meet this requirement should take
advantage of the knowledge about storage adequacy being developed by the IAWG,
as well as existing guidance, such as the ISSC.
Third, the IAWG strategy does
not include other program offices in the defense nuclear complex, such as the
Nuclear Energy, Science, and Technology (DOE-NE) facilities involved in defense
nuclear activities. Currently, materials
and activities in transition between the facilities of different program
offices have the potential to be overlooked. For example, operators at the Savannah River
Site have begun converting the neptunium-237 solutions covered under Recommendation
94-1 to oxide and placing the oxide in packaging intended for 1 year of storage
at that site prior to offsite shipping. The long-term storage of large quantities of
neptunium oxide has not been performed previously in the complex, and the
technical basis for ensuring the safety of such storage is incomplete. Nonetheless, these materials will be
transferred to DOE-NE for use, where they may continue to be stored in their
existing packaging for a period of up to 20 years. In addition, the Board has learned that DOE-NE
intends to assume more direct control of activities involving plutonium-238,
which have to date been performed at NNSA sites. The significant radiological
hazards associated with this material necessitate appropriate storage containers
for the expected storage period. The
Board believes the requirement for a technical basis for nuclear material
packaging and storage should encompass all program offices in the defense
nuclear complex. DOE may wish to
consider implementing this requirement for all program offices, including those
outside of the defense nuclear complex.
The Board is encouraged by other
efforts currently under way to improve nuclear material packaging. As a result of discussions between the Board’s
staff and LLNL, the Livermore Site Office, in a December 3, 2004, letter,
directed LLNL to develop a technical basis for the adequacy of storage packages
as part of a Special Nuclear Materials Storage Plan covering “all packaging
activities”. LLNL replied in a letter of
January 31, 2005, outlining the required activities, milestones, and funding to
develop and implement an approved packaging and storage program. Implementation of the plan is contingent upon
the availability of key personnel and funding. Likewise, the proposed Documented Safety
Analysis (DSA) for the LANL Plutonium Facility requires the use of a proposed
facility packaging standard and designates material containers as a
safety-related component. However, the
new DSA has been awaiting NNSA approval. In general, these efforts represent an
improvement, but they do not represent a comprehensive DOE-wide effort, and
significant differences remain in the quality of the efforts at individual facilities.
Recommendation
Nuclear material packaging
provides the primary containment boundary to protect facility workers during
storage and handling activities. The
Board believes the development of technically justified criteria for packaging
systems for nuclear materials is necessary on a DOE-wide level. Therefore, the Board recommends that DOE:
Issue a requirement that nuclear
material packaging meet technically justified criteria for safe storage and
handling. Packaging should, in general,
provide a robust barrier between facility workers and the stored nuclear
materials once they are removed from an approved engineered contamination
barrier. It may be appropriate to
include this requirement in an updated nuclear materials management Order.
Identify which nuclear materials
should be included in the scope of the above requirement and then determine the
technically justified packaging criteria needed to ensure the safe storage and
handling of those materials. The scope
need not include waste materials, fully encapsulated forms, or de minimus
quantities such as analytical laboratory samples. The criteria should account for the nuclear
material form and properties, expected future use, and duration of storage. It may be appropriate for this information to
be included in a packaging Manual.
The ISSC may provide the
beginning of a sound technical foundation for developing such criteria. Although some modifications may be necessary
to make the ISSC more applicable to short-term storage, the Board believes the
basic ISSC principles―for
example, the requirement for a minimum of two contamination boundaries for
high-hazard materials such as plutonium, assurance that leak-tightness is
maintained for materials requiring a sealed environment, ability of the
containers to withstand maximum expected internal pressures, and protection
against common insults such as drops―should be maintained. The criteria should also include provisions
for surveillance programs to verify that the container and any limited-life
components are performing in a manner consistent with the duration of storage.
Prioritize implementation of the
improved nuclear material packaging requirement consistent with the hazards of
the different material types and the risk posed by the existing package
configurations and conditions.
John T. Conway, Chairman
Attachment
ATTACHMENT
Selection
of Commonly Used Nuclear Material Packaging
Food-Pack Cans
Food-pack cans are thin-walled
tinned carbon steel containers used in the food industry. No additional manufacturing or structural
requirements have been specified for application with nuclear materials. These cans typically rely on a double-crimped
metal-to-metal closure with a thin layer of sealing compound to provide
leak-tightness. Historically, many sites
have reported failures of food-pack cans. Lawrence Livermore National Laboratory (LLNL)
has reported anecdotal evidence suggesting that none of its food-pack cans have
failed to the point of detectable contamination outside the container
(UCRL-ID-11733). However, this same
report states further that some degree of oxidation was observed in all of the
examined food-pack cans containing plutonium metal, suggesting the lack of an
airtight seal. Leakage of oxygen through
nonairtight food-pack cans has been responsible for a number of container
failures reported at other sites, due to oxidative expansion of plutonium
metals (LA-UR-99-2896).
Improvements have been made to
the technology, including better sealing equipment, as discussed in a May 1984
report entitled The
Effectiveness of Corrective Actions Taken to Preclude Events Involving Tin Cans
and Plutonium (RHO-HS-SA-59
P). Some evidence suggests, however,
that these containers still may not be adequate for prolonged storage of nuclear
materials. Approximately half of the
sampled lot of food-pack cans sealed 10 to 14 years earlier at the Hanford
Plutonium Finishing Plant using the improved methodology failed leak testing,
and nearly all showed further indications of a potential lack of seal (LA-UR-99-3053).
Additional testing performed at
Pacific Northwest National Laboratory confirmed that the performance of
food-pack cans is highly dependent on the quality of the seal (PNL-5591). During
these tests, 33 industry-standard food-pack cans were sealed according to
federal specifications. The testing
revealed leak rates ranging from less than 10-5 cubic centimeters
per second (cc/sec) to more than 2 cc/sec. These findings should receive due
consideration when food-pack cans are used for storage applications in which a
hermetic seal is required. LLNL continues
to use food-pack cans as inner and outer containers for the storage of
plutonium metal and oxide, and other sites may be storing nuclear materials
previously packaged in food-pack cans.
Paint Cans
Paint cans are thin-walled cans
with a press-fit lid that are commonly used to store paint. They have been used as both
inner and outer containers for the storage of some nuclear materials, including
plutonium metal. The press-fit lid is
typically placed by hand using a mallet, which results in a
questionable seal lacking any evidence of quality control. According to a January 16, 1987, LLNL site
report entitled Incident
Analysis/Plutonium Burn in Storage Can, oxidation was found to be common for plutonium metal stored
in paint cans (memorandum from R. H. Condit to K. Ernst). The report goes on to calculate that a 4
micron gap integrated across the seal area would be sufficient to permit
complete oxidation of 100 grams of plutonium metal in 1 year. A leak of this size can reasonably be assumed
to be present in the press-fit closure; therefore, the adequacy of these cans
for nuclear material storage applications requiring a seal cannot be ensured. Although LLNL reports that ingress of air is
expected because the lid and rim of the can are not designed to be airtight
(UCRL-ID-117333), paint cans remain approved for use for certain applications
at the laboratory. Other sites may also
be storing nuclear materials that were previously packaged in paint cans.
Taped Slip-Lid Cans
Slip-lid cans are thin-walled
cans with a loose-fitting cover that is often taped. While convenient and inexpensive, the use of
these containers has resulted in several breached storage packages, including
the plutonium-238 package that led to the Type B event at Los Alamos National
Laboratory (LANL). Many nuclear material
packages consisting of nested taped slip-lid cans remain at the Department of
Energy’s defense nuclear facilities. By
design, these cans were never intended to serve a containment function. Furthermore, except for tape, a mechanical
closure is absent, resulting in a container that may not be able to provide
even gross retention of the materials within. The effectiveness of tape in performing this
sealing function over time and under high radiation conditions is poorly
understood. For this reason, the Interim
Safe Storage Criteria (ISSC) specifically prohibits crediting slip-lid cans as
one of the two required contamination barriers. Yet several sites continue to use this type of
packaging. For nonmetallic plutonium,
including items containing plutonium-238, LANL plans to rely on stainless steel
taped slip-lid cans only as an inner container; currently, however, a large
number of items remain at the laboratory in nested slip-lid cans. Moreover, several varieties of slip-lid cans
continue to be approved for use as inner and outer storage containers for
certain materials at LLNL.
Hagan Can
LANL’s Comprehensive Nuclear
Material Packaging and Stabilization Plan approves the use of a standard
container known as the Hagan can, a robust, screw-top container with an O-ring
seal and filtered vent. The Hagan can
generally meet the expectations of the ISSC and has undergone testing to
certify its performance (Wickland and Mataya, PATRAM 98, 1998). However, drop testing was performed at a
height lower than the expected maximum storage height; therefore, additional
analysis or testing is required. Under
the proposed Documented Safety Analysis for LANL’s Plutonium Facility, the
Hagan can is classified as a safety-significant engineered feature. The Hagan can appear to be an appropriate
outer package for nuclear material storage, although, as recognized by LANL,
the service life of the Viton (an organic fluorocarbon compound) O-ring
requires verification through a surveillance program. Currently, Hagan cans are widely used only at
LANL; however, their use may be under consideration at other sites.
Conflat Can
A
can fabricated
with a Varian-type Conflat flange results in a hermetically sealed, robust container
that can be used to store plutonium metal. A copper gasket on a bolted flange closure is designed to
maintain a long-term hermetic seal against oxidation of plutonium metal. This closure type has been standard in the
high-vacuum industry for many years and has been certified to maintain a
leak-tight seal under various temperature and pressure conditions. The Conflat can is identified in LANL’s
Comprehensive Nuclear Material Packaging and Stabilization Plan as the inner
container for the storage of plutonium metal. The use of Conflat cans for storage of other
nuclear materials requiring a sealed environment may also be appropriate. Conflat cans have been used periodically at
some sites for special storage applications, but their use is not widespread or
uniform.
Metal Drums
Several sites commonly use U. S.
Department of Transportation (DOT) Type A containers and similar types of
metal drums for overpacking of packages of nuclear materials for onsite
transportation and storage. These
containers have been certified as Type A radioactive material packages
per DOT specifications. For
transportation purposes, this certification usually is limited to a single year.
The use of these containers for interim
storage beyond the certification period appears appropriate, but consideration
should be given to periodic inspection and replacement for limited-life
components, such as lid gaskets. The Criteria for the Safe Storage
of Enriched Uranium at the Y-12 Plant (Y/ES-015/R2) allow interim storage of enriched uranium
materials for a period of up to 10 years in DOT Type A
or Type B
containers.
Y-12 Prolonged Storage
Container
The Y-12 Y/ES-015/R2 criteria
specify the use of stainless steel cans similar to food-pack cans for prolonged
low-maintenance storage for up to 50 years. While the reliance on a single robust barrier
for the storage of enriched uranium may be appropriate, it is unclear whether
the requirement to maintain mechanical and seal integrity during normal
handling includes protection against drops. In addition, a lid sealant compound is
specified in the appendix to Y/ES-015/R2, but no discussion of its longevity is
provided. While fewer radiological
hazards and less chemical reactivity are associated with enriched uranium than
with plutonium and some other nuclear materials, further testing of these
containers would better demonstrate their reliability for long-term storage. Currently, the Y-12 container specification is
planned for use only at the Y-12 National Security Complex.
Plastic Bags and Bottles
Historically, plastic bags have
been relied upon to provide contamination control for a limited period. Bag materials, which include polyethylene,
polyvinyl chloride, and related polymers, play an important role in the overall
packaging system. Their principal use is
for contamination control during the “bagout” operation, when the nuclear
material container is removed from the glovebox. Unfortunately, some types of bags have proven
to be detrimental to the integrity of packages left in storage for prolonged
periods of time. For example, the radiation-induced
degradation of polyvinyl chloride bag material led to the production of hydrochloric
acid, which in turn contributed to the corrosion and eventual failure of
containers that occurred during the Type B event at LANL. The choice of material also impacts the generation
of radiolytic gas and effectively defines the service life of a package when
the outer container is not leak-tight. In repackaging campaigns at LLNL, as well as
at other sites, such as Hanford, bags commonly have been found to be in a
discolored or otherwise degraded state (UCRL-ID-117333 and WHC-SD-TRP-067). While plastic bags have been in use for a long
time, little quantitative information exists on the effects of time,
temperature, and radiation field exposure on maintenance of an effective
contamination barrier. It is recognized
that plastic bags may be necessary for Contamination control, but they should
not be relied upon as a long-term contamination barrier.
In some cases, plastic bottles
(e.g., safe bottles) have been used for the storage of solutions containing
nuclear materials, especially enriched uranium, outside of processing equipment.
While bottles are constructed of thicker
plastics than are bags, they undergo the same chemical and radiolytic
degradation with time and must be compatible with the chemical properties of
the contained liquids. Furthermore,
whereas bags provide only contamination control, bottles are relied upon to
provide a complete contamination barrier, including structural integrity. Any reliance on plastic bags or plastic
bottles for extended periods of time should be informed by the available
knowledge of polymer degradation, in combination with information gleaned from
surveillance programs.