Lessons Learned HQ-EH-2004-01
Title: Degradation and Failure of Stored Radiological Material Containers and
Packages
Identifier: HQ-EH-2004-01
Date: 2004-01-01
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Summary: The failure of an irradiated test specimen canister on December 3, 2003 and the breaching of a plutonium-238 package and resulting in worker uptake exposures on August 5, 2003 demonstrate that long-term storage of radioactive material containers and packages continue to pose hazards. Corrosion and other degradation of radioactive material packages and their contents, in combination with the buildup of pressurized flammable gases from radiolysis and decomposition, can create the potential for accidents unless such conditions are considered in design and maintenance, and for the actual storage lives of the packages. |
Lesson Learned Statement:
Recent events demonstrate that long-term storage of radioactive
material containers and packages continue to pose hazards. Corrosion
and other degradation of radioactive material packages and their
contents, in combination with the buildup of pressurized flammable
gases from radiolysis and decomposition, can create the potential
for accidents unless such conditions are considered in design and
maintenance, and for the actual storage lives of the packages.
Discussion: On
December 3, 2003, at the Naval Reactors Facility on the Idaho National
Engineering and Environmental Laboratory, a canister containing
an irradiated non-fuel test specimen failed catastrophically while
stored in a water pool. The failure made a large noise, dislodged
the stainless steel canister (made from 4-inch diameter schedule
40 pipe, 18 inches long), ruptured its brass cap, and projected
part of the cap 10 feet away underwater. No injuries or other damage
occurred and there was no measurable release of radioactivity to
the environment.
The brass cap screwed
onto the canister, with two nitrile rubber o-rings providing a watertight
seal. Investigators found evidence of water leakage inside the canister.
Their preliminary conclusion is that during the 14 years the canister
was stored in the water pool, the nitrile rubber seals degraded
from exposure to high-flux gamma radiation emitted from the test
specimen. Water leaked into the canister and the canister subsequently
resealed tightly as a result of the brass cap's corrosion. Radiolysis
caused the captured water to break down into hydrogen and oxygen
gas, pressurizing the canister. (Decomposition of the nitrile rubber
could also generate flammable gases.) The investigators concluded
that the hydrogen detonated and caused the failure. Although the
ignition source is not now clear, it could have been thermal energy
from the specimen, reactions from radicals produced by the radiolysis,
sparking from interaction of metallic components, or static electricity
discharge.
Another recent case
involving hazards from degradation of a radioactive materials container
occurred on August 5, 2003, at Los Alamos National Laboratory (LANL)
Technical Area 55. A package containing residues from plutonium-238
operations breached while being handled by two workers performing
a pre-inventory check. The pressurized release of materials from
the package gave the workers uptake doses of two or three rems CEDE.
Slightly different release conditions could have increased the doses
by orders of magnitude.
The plutonium-238 package
had been in storage since 1996. A subsequent Type B investigation
concluded that chemical, radiolytic, and thermal decomposition of
the package and its contents produced significant corrosion and
gas in the package. The corrosion caused "breathable" seams in the
package to seal and resulted in the buildup of gas pressure. Handling
the package dislodged corrosion in the package and pressurized contaminated
gases vented into the room's atmosphere.
Analysis: In
DOE, the causes and potential consequences from aging and degradation
of radiological material packages have been well know since at least
the early 1990's. Then, many packaging configurations intended for
only temporary storage became subjected to much longer storage periods.
The increased frequencies and mechanisms of radioactive material
packaging failures were analyzed and disseminated in initiatives
such as the Plutonium and Highly Enriched Uranium Vulnerability
Studies. A considerable effort was made to process or repackage
the stored materials. Today, however, there are still radioactive
material packages poorly designed for extended storage, as evidenced
by recent events.
The report of the Type
B accident for the LANL occurrence noted that corrosion and degradation
of similar plutonium-238 residue packages had caused multiple near
miss events since 1994. In the prologue to this report, the Manager
of the Los Alamos Site Office stressed that the accident could have
been avoided if only the lessons learned from the near misses had
been addressed.
Recommended Actions:
- The design, evaluation,
and maintenance of radioactive material packages must address
aging and degradation of their contents and packaging components.
- The design, evaluation, and maintenance
of radioactive material packages should consider potential scenarios
involving combinations of component failures, particularly aging
mechanisms that open and seal containment and vents in combination
with those that generate flammable and pressurized gases.
- The packaging of radioactive materials
in long-term storage should be checked to see if they have design
specifications compatible with currently planned storage lives
and conditions.
- If such design specifications are not
met, or do not exist, then the packaging needs to be evaluated
for currently planned storage lives and conditions.
- Near misses from packaging failures need
be recognized and addressed to prevent future accidents.
- When dealing with radioactive material
packages that have not been designed to current standards (i.e.,
legacy materials), always assume that the package is unsafe until
it is proven safe or repackaged to current standards.
Originator: Dan
Guzy, EH-3
Validator: Jim
Mangeno, NA-1
Contact: Dan
Guzy, 301-903-2428
Name of Authorized
Derivative Classifier: Not required.
Name of Reviewing Official:
Frank Russo
Priority Descriptor:
Blue / Information
Keywords: Container,
canister, package, aging, degradation, corrosion, storage, radiolysis,
hydrogen.
References:
ALO-LA-LANL-TA55-2003-0017,
Two Employees Found Contaminated After CAM Alarmed During Work in
TA-55, Building 4, Room 201B
Type
B Accident Investigation of the August 5, 2003 Plutonium-238 Multiple
Uptake Event at the Plutonium Facility, Los Alamos National Laboratory,
New Mexico, December, 2003.
DOE/EH-0415,
Plutonium Working Group Report on Environmental, Safety and Health
Vulnerabilities Associated with the Department's Plutonium Storage,
November 1994.
DOE/EH-0525,
Highly Enriched Uranium Working Group Report on Environmental, Safety
and Health Vulnerabilities Associated with the Department's Storage
of Highly Enriched Uranium, December 1996.
Information
in this report is accurate to the best of our knowledge. As means
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DOE Function / Work
Categories: Storage Maintenance
ISM Category:
Analyze Hazards
Develop / Implement Controls
Hazard:
Fire and Explosion Over-pressurization Personal Injury Radiological
Exposure and Contamination
This page was last updated on January 05, 2007
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