Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6870
Accession No.:
8005050046
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
May 30, 1980
Information Notice No. 80-25
TRANSPORTATION OF PYROPHORIC URANIUM
Background
From time to time NRC has received reports of transportation incidents
involving the shipment of uranium in a pyrophoric form (capable of
spontaneous ignition). These forms generally include finely divided metallic
saw turnings and chips, sawdust, and abrasive saw sludge. Moisture in the
form of water or machining coolants is usually present on the finely divided
material, contributing to its reactivity due to the radiolytic decomposition
of the water reacting with the base metal to create hydrogen gas. Hydrogen
gas generation and reactivity will vary with the particle size (surface area
to volume ratio) of the fines, free moisture content, and age of the
material. Although the exact reaction kinetics of finely divided pyrophoric
metals is not well understood, past industry experience has indicated that
extreme care must be exercised in the proper storage and transportation of
such pyrophoric forms of uranium so as to preclude spontaneous ignition.
Fires resulting are extremely difficult to extinguish using such convential
fire extinguishing agents as CO2, foam, and dry chemical. Water, if used in
very large volumes or by total immersion can be effective. Water used as a
fine spray, however, can be extremely dangerous, actually causing a more
violent reaction due to the radiolytic breakdown of the water from the
extremely high temperatures. Further, such fires also create an inhalation
hazard due to the dispersion of airborne uranium as particulate matter.
Transportation Regulations
Although the Department of Transportation (DOT) regulations in 49CFR do not
provide specific provisions for packaging and shipment of pyrophoric
uranium, in 49 CFR 172.101, there does appear a proper shipping name:
"Uranium metal, pyrophoric", under the radioactive material hazard class.
This indicates that such materials are to be labelled as both a radioactive
material and a flammable solid. Under the column "packaging", SS172.101 then
makes reference to the requirements for low specific activity and fissile
radioactive materials. The only other relevant provision of 49CFR, albeit, a
very important one is 49 CFR 173.21(b): under "Prohibited packaging", which
reads:
"(b) the offering of any package or container of any liquid solid or gaseous
material which under conditions incident to transportation may polymerize
(combine or react with itself) or decompose so as to cause dangerous
evolution of heat or gas is prohibited. Such materials may be offered for
transportation when properly stabilized or inhibited. Refrigeration may be
used as a means
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Information Notice No. 80-25 May 30, 1980
Page 2 of 3
of stabilization only when approved by the Bureau of Explosives". However,
the DOT regulations require no specific methods of stabilization of
pyrophoric uranium prior to shipment.
Shipping Practices
In the earlier years of the nuclear industry many shippers offered
pyrophoric uranium for transportation in steel drums, in which the turnings,
chips or sludge was submerged under mineral oil. This method has the
distinct safety problem of allowing a pressure buildup of hydrogen gas
within the drum. This may cause a personnel hazard upon opening the drum,
and a possible explosive release and/or ignition of the hydrogen gas. In
some cases, venting devices have been used or holes have been drilled in
drum lids to allow continuous venting of hydrogen gas. However, this poses
problems also, especially in confined or closed spaces, such as a closed
highway van.
Currently, most shippers of pyrophoric uranium have elected not to transport
such materials submerged under oil. Instead, one the following alternatives
is used:
1. Conversion of the material to a non-pyrophoric material in a oxide form
by incineration prior to shipment.
2. Mixing of the pyrophoric material in a hardened matrix of concrete,
with a high concrete to turnings ratio. Such mixing appears to
stabilize the material so as to preclude any significant gas
generation.
3. Mixing of the pyrophoric material in a solidified plaster-of-paris type
matrix. (This method may not eliminate gas generation and may not
sufficiently "stabilize" the material. A shipment of such material was
involved in a May 14, 1979 incident at the Beatty, Nevada waste burial
facility. During this incident fire destroyed a vehicle containing such
uranium wastes, along with other wastes containing flammable
scintillation fluids. The exact cause of the fire is uncertain,
however, the extremely reactive nature of the pyrophoric materials
present undoubtedly contributed to the severity of the fire).
Proposed DOT Regulations
In order to more clearly specify safety provisions for packaging and
transport of pyrophoric materials, DOT has recently proposed (Jan 8, 1979 44
F.R. 1852, Part II) new criteria for description, classification and
packaging of "pyrophoric radioactive materials". These proposed criteria are
quoted in Enclosures 1 & 2.
Summary
In view of the above, NRC licensees who generate pyrophoric forms of uranium
in their licensed operations are cautioned to carefully consider the
requirements of 49 CFR 173.21(b) to properly "stabilize" such materials
prior to
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Information Notice No. 80-25 May 30, 1980
Page 3 of 3
offering them for transport. The methods which have apparently been the most
satisfactory are:
1. Incineration to a non-pyrophoric oxide (will require specific approval
pursuant to 10 CFR 20.305); or
2. Mixing and solidifying in a large matrix of concrete.
Questions about this Information Notice can be directed to NRC Headquarters,
Office of Inspection and Enforcement, Division of Fuel Facilities and
Materials Safety Inspection, Washington, D.C. 20555 (Attn: Sr.
Transportation Specialist) 301-492-8188.
