Information Notice 1999-03, Rev. 1: Exothermic Reactions Involving Dried Uranium Oxide Powder (Yellowcake): Difference between revisions

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{{Adams
#REDIRECT [[Information Notice 1999-03, Exothermic Reactors Involving Dried Uranium Oxide Powder (Yellowcake)]]
| number = ML14028A175
| issue date = 03/04/2014
| title = Rev. 1: Exothermic Reactions Involving Dried Uranium Oxide Powder (Yellowcake)
| author name = Camper L
| author affiliation = NRC/FSME/DWMEP
| addressee name =
| addressee affiliation =
| docket =
| license number =
| contact person = Evans R
| document report number = IN-99-003, Rev 1
| document type = NRC Information Notice
| page count = 18
}}
{{#Wiki_filter:UNITED STATES
 
NUCLEAR REGULATORY COMMISSION
 
OFFICE OF FEDERAL AND STATE MATERIALS
 
AND ENVIRONMENTAL MANAGEMENT PROGRAMS
 
WASHINGTON, D.C. 20555 March 4, 2014 NRC INFORMATION NOTICE 1999-03, REV. 1:                  EXOTHERMIC REACTIONS INVOLVING
 
DRIED URANIUM OXIDE POWDER
 
(YELLOWCAKE)
 
==ADDRESSEES==
All operating uranium recovery facilities that produce uranium oxide powder (yellowcake). All
 
Agreement States with the authority to regulate uranium mills (i.e., Utah, Colorado, Texas, Ohio, Illinois, and Washington).
 
==PURPOSE==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this Information Notice (IN) to alert
 
licensees to recent events involving pressurized drums of dried uranium oxide powder
 
(yellowcake). This IN is a revision to IN 99-03 which previously discussed industry experience
 
with pressurized 208-liter (55-gallon) metal drums (hereafter referred to as drums) and related
 
exothermic reactions involving yellowcake material. It is expected that recipients will review this
 
information for applicability to their licensed activities and consider actions, as appropriate, to
 
avoid similar problems. However, suggestions contained in this IN are not NRC requirements;
therefore, no specific action or written response is required.
 
==DESCRIPTION OF CIRCUMSTANCES==
The NRC is aware of at least nine different sites that have encountered problems with
 
pressurized drums. A brief description of two events is provided below. Both events resulted in
 
uptakes of uranium by workers, and both have similar root causes.
 
In 2006 at a conventional mill, a worker attempted to open a drum filled with yellowcake that
 
exhibited bulging. Unbeknownst to the worker, the sealed drum was pressurized. The pressure
 
was apparently caused by the generation of oxygen gas within the drum from the decomposition
 
of hydrogen peroxide precipitated yellowcake product. When the drum sealing bolt was
 
loosened, the pressure in the drum caused the lid to blow off the drum and strike the worker.
 
The worker received an uptake of uranium, although the uptake was less than regulatory limits.
 
Records indicate that the drum lid had remained unsealed for three hours after the drum had
 
been filled with yellowcake product, as required by site procedures.
 
ML14028A175
 
IN 1999-03, Rev. 1 The facility operator conducted an investigation and identified the root cause as less than
 
adequate procedures. The facility operator concluded that the product did not completely cool, or off-gas, within the three-hour time interval. Corrective actions included revising the
 
applicable procedure to extend the drum sealing interval from three to four hours and providing
 
additional training to site workers.
 
The second incident occurred in 2012 at a uranium refinery in Canada while workers were
 
opening a drum of yellowcake supplied by an in-situ uranium recovery facility. When a refinery
 
worker loosened the ring clamp on the drum lid, the pressure in the drum (produced by an
 
unexpected build-up of oxygen gas) caused the lid to buckle. The escaping gas ejected
 
approximately 20 kilograms (44 pounds) of dried, powder-like yellowcake material from the
 
drum. The incident resulted in three refinery workers receiving uptakes of uranium. The
 
refinery operator subsequently identified several other drums, supplied by the same uranium
 
recovery facility, which also showed signs of internal pressurization. The uranium recovery
 
facility operator conducted an investigation to determine the causes of the pressure buildup in
 
the drums. The facility operator concluded that the drums became pressurized due to:
(1) inadequate cooling and venting of the dried yellowcake product prior to sealing the drum lid;
and (2) inadequate drying of the yellowcake product (i.e., inadequate dryer residence time).
 
The NRC later determined that inadequate procedures were contributing causes of the event.
 
==BACKGROUND==
The NRC issued IN 99-03 on January 29, 1999, to alert licensees to incidents involving
 
exothermic reactions that occurred after packaging hydrogen peroxide precipitated yellowcake
 
powder into drums. The original IN discussed two types of exothermic reactionsoxygen
 
generation as a byproduct of the drying process and hydrocarbon contaminants reacting with
 
the yellowcake product. At that time, industry took corrective actions which included leaving the
 
drums unsealed for a minimum of three hours and preventing oil and grease from being
 
introduced into the precipitation and drying circuits.
 
Since 1999, the uranium recovery industry has experienced several more pressurized drum
 
events. Because these events continued to occur, the causes may not be well understood by
 
the industry. Further, past actions taken by industry to prevent pressurized drums may not have
 
been fully effective.
 
The IN 99-03 also advised facility operators about exothermic reactions of yellowcake with
 
organic materials. These reactions can cause spontaneous combustion of flammable materials
 
such as oil that may enter the process circuit. Refer to Enclosure 1 for an expanded discussion
 
of this hazard.
 
==DISCUSSION==
In both the 2006 and 2012 instances, the fundamental cause of the pressurized drums was
 
attributed to the build-up of oxygen gas in sealed containers. The oxygen gas apparently
 
originated from the decomposition of residual uranyl peroxide hydrates or hydrogen peroxide in
 
the dried yellowcake product. Both incidents indicate that the drum lids may have been sealed
 
onto the drums prior to the completion of the uranyl peroxide hydrate decomposition process.
 
Both sites used a minimum three-hour time delay as mentioned in IN 99-03; however, this time
 
delay must have been insufficient based on site-specific operational parameters.
 
IN 1999-03, Rev. 1 In early 2013, the NRC established a working group to: (1) review the generic implications of the
 
most recent pressurized drum incident including the reasons why drums continue to become
 
pressurized; (2) identify industry experience with pressurized drums; and (3) ascertain whether
 
there were any related trends across the industry. The working group consisted of NRC staff, industry representatives, and subject-matter experts. The NRC used the findings of the working
 
group, as well as information solicited from 14 current and former uranium recovery facilities, in
 
the development of this revision to IN 99-03. As part of the revision process, the NRC is also
 
correcting some of the chemical nomenclature used to describe the thermal decomposition
 
process provided in the original IN. More importantly, as a result of industry experience gained
 
since the NRC issued IN 99-03, this revised IN recognizes a broader range of relevant factors
 
that could result in pressurized drums.
 
The working group developed a questionnaire that was submitted to various national and
 
international companies having direct experience processing or handling yellowcake. The
 
working group received 14 responses from various entities. The responses were subdivided
 
into two basic categoriessites using ammonia precipitation circuits and sites using hydrogen
 
peroxide precipitation circuits. The survey responses provided the working group with detailed
 
information about dryer and packaging operations at each site as well as industry experience
 
with pressurized drums. If the facilities had experienced pressurized drum problems, the survey
 
asked the respondents to explain the possible causes for the pressurizations. As discussed in
 
Enclosure 1, sites using the ammonia precipitation process with high-temperature calciners
 
have not experienced pressurized drums. Only sites using the hydrogen peroxide precipitation
 
circuits have experienced pressurized drums. Enclosure 3 provides a matrix of the operating
 
parameters for the 11 sites using hydrogen peroxide precipitation circuits and the suspect
 
causes of past drum pressurizations.
 
The working group concluded that many drum pressurizations were apparently caused by
 
changes in the chemical composition of the yellowcake product after it had been placed into a
 
sealed container. The level of pressurization appears to be related to the cooling and venting
 
time of the product prior to sealing of the drum. The working group determined that the
 
minimum required cooling and venting time for recently dried yellowcake in an unsealed drum
 
depends on the type of dryer, drying temperature, residence time (time product remains in
 
dryer), hold-up time (time interval between completion of drying cycle and when product is
 
placed into drum), dryer feed rate, and product moisture content. These various operational
 
parameters may ultimately contribute to oxygen gas buildup in yellowcake drums.
 
As noted earlier, multiple operators reported that they had experienced pressurized drum
 
problems, but the specific chemical reactions causing the pressurizations were not always clear.
 
In their survey responses, facility operators provided two general corrective actions to address
 
the pressurized drum issueincreasing the cooling/venting time before the lid is sealed onto the
 
drum and conducting visual inspections of the drums for signs of pressurization prior to
 
shipment. These operators found that increasing the cooling and venting time before sealing
 
the drums and inspecting the drums before shipment appear to have resolved the problem. A
 
range of cooling and venting times was reported, from 4 to 24 hours (see Enclosure 3). In
 
several instances, facility operators chose to extend the cooling and venting times in response
 
to past experiences with pressurized drums. Each facility operator should evaluate their
 
operations and decide how to implement site-specific corrective actions as necessary to prevent
 
pressurized drums.
 
IN 1999-03, Rev. 1 The working group found that many operators did not measure their product temperature
 
directly, and that discrepancies existed between the maximum dryer temperature and the
 
chemical composition of their final product. It is product temperature, not dryer temperature, which ultimately drives the thermal decomposition process. The working group concluded that, for typical U.S. facilities utilizing hydrogen peroxide precipitation and drying temperatures below
 
800 degrees Celsius (°C) [1472 degrees Fahrenheit (°F)], a cooling and venting period of 12 to
 
24 hours appears sufficient to prevent oxygen gas buildup in yellowcake drums. Above dryer
 
temperatures of approximately 800 °C (1472 °F), it is expected that the uranyl peroxide product
 
will be converted to UO3 (uranium trioxide) product. Oxygen production is not expected to occur
 
after the uranyl peroxide product has been completely converted to UO3 product. For dryers
 
operating below 800 °C (1472 °F), shorter periods of yellowcake cooling and venting prior to
 
securing the drum lid may be ineffective to prevent oxygen buildup in sealed drums.
 
CONCLUSION
 
Based on its working group findings and questionnaire responses, NRC concludes that:
    The most likely cause for the drum pressurization events was attributed to continued
 
decomposition of dried uranium product and the production of oxygen after the drums have
 
been filled and sealed.
 
For facilities utilizing hydrogen peroxide precipitation and drying temperatures below 800°C
 
(1472°F), a cooling and venting period of at least 12 hours appears to be necessary to
 
prevent oxygen gas build-up in yellowcake drums. Shorter periods may be ineffective.
 
Many operators have elected to implement a cooling and venting time of 24 hours.
 
To prevent drum pressurizations, facility operators have implemented two basic corrective
 
actionsincreasing the cooling/venting time before the lid is sealed and conducting visual
 
inspections of the drums for signs of pressurization prior to shipment.
 
Facility operators should evaluate the potential for organic-based exothermic reactions, as
 
discussed in Enclosure 1. Facility operators should develop protocols to minimize the
 
potential for organics, including oils and greases, to enter into yellowcake process circuits.
 
In addition to being industrial and radiological hazards to workers, shipments of uranium
 
yellowcake in packages with internal pressures that reduce the effectiveness of the
 
packages are prohibited by U.S. Department of Transportation regulations. Enclosure 1 provides additional information about these regulations.
 
IN 1999-03, Rev. 1
 
==CONTACT==
This information notice requires no specific action or written response. If you have any
 
questions about the information in this notice, please contact one of the technical contacts listed
 
below.
 
/RA Aby Mohseni for/
                                      Larry W. Camper, Director
 
Division of Waste Management
 
and Environmental Protection
 
Office of Federal and State Materials
 
and Environmental Management Programs
 
Contacts:      Robert Evans, Region IV
 
(817) 200-1234 Robert.Evans@nrc.gov
 
Ronald Burrows, FSME
 
(301) 415-6443 Ronald.Burrows@nrc.gov
 
Thomas McLaughlin, FSME
 
(301) 415-5869 Thomas.Mclaughlin@nrc.gov
 
Enclosures:
1. Detailed Technical Discussion
 
2. Bibliography
 
3. Survey Results for Facilities Using Hydrogen Peroxide Precipitation
 
4. FSME Recently Issued Generic Communications
 
IN 1999-03, Rev. 1
 
==CONTACT==
This information notice requires no specific action or written response. If you have any
 
questions about the information in this notice, please contact one of the technical contacts listed
 
below.
 
/RA Aby Mohseni for/
                                        Larry W. Camper, Director
 
Division of Waste Management
 
and Environmental Protection
 
Office of Federal and State Materials
 
and Environmental Management Programs
 
Contacts:        Robert Evans, Region IV
 
(817) 200-1234 Robert.Evans@nrc.gov
 
Ronald Burrows, FSME
 
(301) 415-6443 Ronald.Burrows@nrc.gov
 
Thomas McLaughlin, FSME
 
(301) 415-5869 Thomas.Mclaughlin@nrc.gov
 
Enclosures:
1. Detailed Technical Discussion
 
2. Bibliography
 
3. Survey Results for Facilities Using Hydrogen Peroxide Precipitation
 
4. FSME Recently Issued Generic Communications
 
ML14028A175 RIV:DNMS/RSFS            C:DNMS/RSFS                DD:DNMS                D:DNMS
 
RJEvans              DBSpitzberg              VHCampbell                AVegal
 
/RA/                  Via email                Via email              Via email
 
10/24/13                11/06/13                  01/02/14              12/31/13 FSME:DMSSA              FSME:DWMEP              DWMEP/DURLD            C:DWMEP/DURLD
 
ARMcIntosh              RABurrows              TGMcLaughlin                BvonTill
 
Via email                Via email                Via email              Via email
 
10/24/13                10/28/13                  10/28/13              10/29/13 NSIR                FSME:DMSSA                FSME:DILR            OGC/GCLR/RMR
 
CGrigsby                DWhite                    JCai                TLStokes
 
Via email                Via email                Via email              Via email
 
10/28/13                10/24/13                  11/05/13              12/17/13 OE/EB                  NMSS              DD:DWMEP/DURLD              D: MSSA
 
TMarenchin              HJGonzalez                                      JMoses for
 
DPersinko
 
LDudes
 
Via email                Via email                  /RA/                  /RA/
          11/14/13                11/08/13                  01/24/14              02/28/14 D:DWMEP
 
AMohseni for
 
LWCamper
 
/RA/
          03/04/14 OFFICIAL RECORD COPY
 
IN 1999-03, Rev. 1 Enclosure 1 Detailed Technical Discussion
 
At least nine uranium recovery facilities have experienced pressurized drum events. The
 
reasons for these pressurization events varied from facility to facility (see Enclosure 3 for a
 
complete list of suspected causes for the drum pressurizations). The actual causes of previous
 
drum pressurization events are still in question. The causes may include the decomposition of
 
free hydrogen peroxide (H2O2) carried over with the dried yellowcake, decomposition of uranyl
 
peroxide product, production of steam from residual water, reaction of uranium compounds with
 
inorganics, or perhaps a combination of these causes. In addition, a reliable and accurate
 
chemical test for free hydrogen peroxide in yellowcake has not been validated which would
 
allow facilities to precisely determine the actual causes for these types of incidents.
 
The NRCs working group identified several topics that are discussed in detail below. The
 
working groups findings are based on the information that was identified or made available to
 
the group, in part, through uranium recovery facility responses to surveys. Two of the 14 surveys were conducted for sites that are no longer in service, meaning that some of the
 
information presented in the survey may be based on individual recollections versus formal
 
documentation.
 
Precipitation with Ammonia and Use of a Calciner to Dry Yellowcake
 
Three facility operators out of 14 reported using ammonia precipitation instead of hydrogen
 
peroxide precipitation. These operators also dried their precipitated product at high
 
temperatures in a calciner. There was no evidence that the ammonia precipitation process, in
 
combination with a calciner, had ever resulted in pressurized drums. Therefore, these types of
 
facilities are excluded from the current discussion about H2O2 precipitated product.
 
The Chemistry of Hydrogen Peroxide Precipitated Yellowcake
 
Facilities using the hydrogen peroxide precipitation process may create pressurized drums if
 
their operational processes are not appropriately controlled. The chemical product of
 
precipitation depends on the temperature of the solution undergoing precipitation. Based on the
 
survey results, hydrogen peroxide precipitation typically occurs under ambient conditions. At
 
temperatures below 50°C (122°F), the precipitate is generally of the form UO4
* 4H2O (uranyl
 
peroxide tetrahydrate). The final desired product is UO4
* 2H2O (uranyl peroxide dihydrate).
 
Converting the tetrahydrate form (UO4
* 4H2O) of uranyl peroxide to the desired dihydrate form
 
(UO4
* 2H2O) occurs quickly under typical drying conditions. For example, laboratory samples
 
of UO4
* 4H2O will dehydrate to UO4
* 2H2O in about one hour when dried at 100°C (212°F)
(product temperature, not dryer temperature). Typical maximum dryer temperatures at facilities
 
using hydrogen peroxide precipitation range from 130°C (266°F) to 649°C (1200°F), with most
 
facilities operating well below 300°C (572°F). Of course, laboratory studies do not take into
 
account industrial scale production issues such as difficulty in ensuring uniform drying
 
temperature of the product and desired moisture content. The composition of the final product
 
will depend on a variety of drying conditions including dryer temperature, heating time, heating
 
rate, feed rate, product temperature, water content, hydrogen peroxide content, pressure, etc.
 
As a result of all of these variables affecting the final product, it is likely that other chemical
 
species are forming. The compound UO4
* 2H2O does not undergo dehydration like UO4 *
 
IN 1999-03, Rev. 1 Enclosure 1 4H2O, but rather loses oxygen and water simultaneously (i.e., it decomposes to another
 
compound). Uranium trioxide (UO3) will form at around 500°C (932°F) (product temperature),
so for most facilities this reaction is not expected to occur. However, a range of uranium
 
compounds between UO4
* 2H2O and UO3, are likely to form under current typical drying
 
temperatures and drying times. As a group, these intermediate compounds are referred to as
 
amorphous UOX, where (3x3.5). While UO4
* 2H2O is considered the most stable form of
 
uranyl peroxide, amorphous UOX is considered unstable with respect to the decomposition to
 
UO3 even at room temperature. Table 1 demonstrates one example of dryer temperature
 
versus product formation.
 
Table 1 Drying Temperature and product composition: Phases identified in hydrogen peroxide
 
precipitated yellowcake dryer product by X-ray diffractometry1 Dryer
 
Sample          Discharge                    Amorphous
 
UO4*2H2O                  UO3      U3O8 ID        Temperature                        UOx
 
(°C)
                001              as-is              X
 
015              125              X
 
002              131              X
 
022              145              X
 
016              150              X
 
003              175              X
 
017              175              X
 
004              225            Trace          X
 
005              275                            X
 
006              325                            X
 
018              375                            X
 
019              400                            X
 
008              425                            X
 
020              425                            X
 
021              450                            X
 
023              475                            X
 
010              525                            X        4.30%
                011              575                                      X
 
012              625                                      X
 
014              769                                                X
 
1 empty cells indicate not detected
 
In addition, amorphous UOX has been reported to react with free water to liberate oxygen gas.
 
It is not clear whether this is a reaction resulting in UO3, or some other type of reaction.
 
Experiments to date have demonstrated this effect by mixing relatively large amounts of water
 
with amorphous UOX. Figure 1 demonstrates this phenomenon. It is unknown what effect
 
residual moisture at levels typical of uranium recovery facilities has on amorphous UOX. It has
 
also been found that neither UO4
* 2H2O nor UO3 react with water in this manner.
 
IN 1999-03, Rev. 1 Enclosure 1 Figure 1 Product chemistry: Dried hydrogen peroxide precipitated yellowcake reactivity with water
 
Addition of Excess Hydrogen Peroxide During Precipitation Process
 
A stoichiometric excess of hydrogen peroxide is required to optimize precipitation of uranyl
 
peroxide yellow cake. The degree of excess is determined by the composition of the uranium
 
bearing solution (feed stock for precipitation). Molybdenum, vanadium, and other reactive
 
metals contained in the feed stock react with hydrogen peroxide to form soluble complexes. In
 
addition, some fraction of hydrogen peroxide may decompose during the precipitation process.
 
Facility operators should be aware that some of this excess hydrogen peroxide may be carried
 
over into the drying process. The working group understands that an effective drying cycle
 
should eliminate this excess hydrogen peroxide.
 
Stability of Hydrogen Peroxide in the Presence of Uranyl Peroxide Solids
 
Precipitation of dissolved uranium by the addition of hydrogen peroxide is a well-known and
 
common process within the uranium recovery industry. It has been demonstrated that this
 
precipitation process is a reversible chemical reaction. One consequence is that an excess of
 
dissolved hydrogen peroxide must be maintained in solution to drive the precipitation reaction to
 
completion and, hence, to minimize dissolved uranium losses in resulting waste streams. The
 
use of excess hydrogen peroxide is a common practice in the uranium industry where the
 
maintenance of low uranium tails in the precipitation process is desired. The filtrate fluids
 
associated with the resulting uranyl peroxide slurry must also contain a modest but finite
 
concentration of dissolved hydrogen peroxide to avoid dissolution of uranyl peroxide solids. As
 
a result, moist uranyl peroxide slurries entering any drying equipment may contain a small but
 
finite concentration of dissolved hydrogen peroxide.
 
IN 1999-03, Rev. 1 Enclosure 1 Industrial hydrogen peroxide solutions are relatively stable as long as they are properly stored at
 
moderate temperatures, maintained at a pH below 5, and do not come into contact with
 
impurities, especially metals. Uranyl peroxide solids are typically precipitated at low pH (2-4)
under ambient conditions in the presence of small amounts of excess hydrogen peroxide. The
 
resulting slurries are usually pressed and washed at ambient conditions in a filter press
 
operation to remove soluble filtrate impurities from the filter cake. The acidity of the wet cake
 
will likely remain low keeping any residual free hydrogen peroxide relatively stable. This free
 
hydrogen peroxide will, however, begin to decompose over time to oxygen gas and water as it
 
remains in contact with the uranyl peroxide solids. The rate of this decomposition is unknown
 
and, if a test were to be performed to measure residual free hydrogen peroxide, it would have to
 
be performed on fresh uranyl peroxide solids to minimize the subsequent decomposition of
 
hydrogen peroxide. This may explain why it has been difficult to measure free hydrogen
 
peroxide in filter cake samples as the time to perform the tests might be too long for the
 
hydrogen peroxide to remain stable and not decompose.
 
The other condition under which hydrogen peroxide can decompose is elevated temperature.
 
Hydrogen peroxide will slowly decompose at room temperature. The rate of decomposition will
 
increase as temperature increases. If any free hydrogen peroxide enters the dryer it will likely
 
decompose as the temperature of the uranyl solids increases. However, if the free hydrogen
 
peroxide fails to instantly decompose upon entry into the drying chamber, the residual hydrogen
 
peroxide may be captured in the uranyl peroxide crystalline structure during the drying process.
 
Facility operators should try to minimize the amount of residual free hydrogen peroxide in the
 
product prior to the drying process.
 
Drying Temperature of Uranyl Peroxide in Rotary Vacuum Dryers
 
While different dryer types and precipitation processes are utilized in the industry, the majority of
 
facility operators uses hydrogen peroxide precipitation and employs some type of rotary vacuum
 
dryer that operates at a relatively low temperature. These systems are typically batch
 
operations with ambient temperature yellowcake slurry introduced into a pre-heated chamber at
 
atmospheric pressure. The chamber is then sealed and depressurized. The sub-atmospheric
 
pressure within the chamber (i.e., the vacuum) does not remain constant during the drying
 
cycle. Rather, the pressure continuously decreases as water vapor is liberated and evacuated
 
from the chamber via the vacuum pump circuit. The vapor capacity of the vacuum pump limits
 
the operational vacuum (pressure) within the chamber. During the period in which boiling of
 
free moisture is the principle process within the drying chamber, the temperature of the
 
yellowcake solids is tied to the boiling point of water at that pressure. Near the end of the drying
 
cycle, sufficient free moisture has been removed and the pressure within the chamber
 
decreases and approaches a steady state. As this condition is reached, the yellowcake
 
temperature rapidly rises toward the temperature of the heating surfaces within the drying
 
chamber. Essentially, there are two phases to the batch vacuum drying cycle. The first is
 
controlled by the temperature-pressure relationship of boiling water and the capacity of the
 
vacuum pump to remove water vapor. In the second phase, the vacuum pump vapor capacity
 
is no longer limiting and the temperature of the solids is controlled by heat transfer between the
 
vessel surfaces and the yellowcake solids.
 
Regardless of the temperature of the dryer, there is still a minimum time necessary where
 
moisture is driven off before the yellowcake is heated to above 100°C (212°F), the point where
 
UO4
* 2H2O starts to be created. Continued heating of the product can therefore lead to
 
IN 1999-03, Rev. 1 Enclosure 1 conversion to hydrated UO4 (uranyl peroxide); however, there is likely limited time for conversion
 
of UO4 to UO3 (uranium trioxide). As such, any remaining UO4 that does not convert to the
 
more stable UO3 could lead to drum pressurization. Therefore, it is important for facility
 
operators to control the drying process parameters, including temperature, to control product
 
chemistry.
 
Potential Reactions for Uranyl Peroxide Yellowcake in the Presence of Organic Matter
 
Five of 11 respondents that used hydrogen peroxide (H2O2) precipitation process reported that
 
they have experienced exothermic reactions in yellowcake due to organic contamination, and
 
five of 11 reported that they pay special attention to hydrocarbon contamination.
 
The reaction of H2O2 with organics is a well-known but complex reaction. When H2O2 is in the
 
presence of most organic matter, the hydrogen peroxide can react with the organic to form
 
organic peroxide compounds which are usually unstable or can cause the organic to be
 
oxidized, i.e., chemically burned. When organic peroxide compounds are formed they have
 
been known to detonate, i.e., cause spontaneous combustion or cause oxidation reactions to
 
occur. These latter reactions result in the evolution of heat (from the burning of the organics)
and the evolution of CO2 (carbon dioxide), CO (carbon monoxide), and H2O (water) depending
 
upon the completion of the reaction. When hydrogen peroxide reacts in this way with organics
 
there is always a signature gas evolution which will be indicative of the reaction taking place.
 
Under certain conditions of temperature, metal catalysts, and reactant concentrations, organics
 
can react with the hydrogen peroxide. This interaction results in a complex, multi-step reaction
 
which typically forms many intermediate hydroxyl radicals as the oxidation reaction is on-going.
 
This process can be simplified as follows:
        H2O2 + Organics (CxHy) A B C. CO2 + CO + H2O + Heat
 
Where A, B, C, etc. are the intermediate compounds that form prior to full oxidation (compounds
 
that contain OOH- or OH- radicals). The end result of this chain of reactions is that the organic is
 
chemically burned and the signature off-gases of this reaction are CO2 + CO + H2O plus heat.
 
When these intermediate compounds form, they combine unstably bound oxygen together with
 
hydrogen and carbon in the same molecule, and these organic peroxides can ignite easily and
 
burn rapidly and intensely. When organic peroxide begins to decompose, the heat produced by
 
its decomposition may not dissipate as quickly as it is generated which can result in increasing
 
temperatures which further intensifies the rate of exothermic decomposition. This can create a
 
dangerous situation known as a self-accelerating decomposition.
 
When wet yellowcake is introduced into a dryer system it is important that the product not
 
contain organic matter as the reactions of any residual H2O2 or decomposed uranyl peroxide
 
hydrate can occur. For trace amounts of organics, this will likely not be an issue as the dryer
 
can dissipate any heat that is formed by these reactions, or the organic will be driven off by the
 
heat of the drying operation. If, however, larger amounts of organics were to be introduced into
 
the dryer, a self-accelerating reaction can occur where the heat cannot be dissipated, high
 
temperatures are generated, and a violent reaction is possible. This has occurred in some dryer
 
facilities when there was a mechanical failure in the dryer which caused large quantities of
 
organics such as oil to be introduced into the dried yellowcake at elevated temperatures.
 
IN 1999-03, Rev. 1 Enclosure 1 If the yellowcake is dried at high temperatures as in a calciner, the problem of organic reactions
 
is less likely since the higher temperatures encountered in the dryer will drive off the volatile
 
organics and decompose any organic peroxides that might have been formed. In a low
 
temperature dryer, some organics can remain with the dried uranyl peroxide hydrates and
 
become unstable in the dryer or when removed from the dryer. This could have consequences
 
for drummed material as the decomposition of any organic peroxide can generate heat plus
 
CO2, CO, and H2O. The consequence of this could be the slow generation of combustion gases
 
(for small amounts of organics) or a more violent reaction if large amounts of organic peroxides
 
begin to decompose and generate heat which can cause a self-accelerating reaction to occur.
 
In summary, facility operators should be aware that organic reactions are possible with
 
yellowcake product, and operators should try to locate and eliminate potential sources of
 
organic matter from entering into the precipitation and drying circuits.
 
Packaging (Drumming) of Yellowcake
 
Dried yellowcake is almost exclusively stored and shipped in 208-liter (55 gallon) steel drums.
 
In the U.S., the drums must meet U.S. Department of Transportation specifications if the facility
 
operator plans to ship yellowcake material in the drums. Facilities use new drums, reconditioned (used) drums, or a combination of both, depending on drum availability and/or
 
cost. It is critical that operators ensure that drums used to ship yellowcake do not have any
 
organic material (such as oil or grease) in them. Employees must be trained and informed
 
about the serious complications of organic material in drums to ensure that drums used for
 
shipment are received from the suppliers in acceptable condition and the facility does not
 
inadvertently use such drums for another purpose that could result in organic material
 
contamination prior to filling with yellowcake.
 
Information Notice 99-03 cautioned that new drums and lids could be a potential causal factor in
 
drum pressurization incidents due to the tighter seal of such drums compared to reconditioned
 
drums and lids. The tighter seal could prevent the off gassing from escaping the drum, thereby
 
leading to pressurization. Although this condition is still possible with new drums or
 
reconditioned drums that happen to have better seals, the working group believes that
 
appropriate controls, such as adequate cooling and venting times, will prevent any significant
 
potential for gas build up and drum pressurization.
 
To limit the potential of shipping a drum of yellowcake that has been pressurized due to an
 
unexpected cause, including a human factor, it is strongly suggested that operators include as
 
part of their final pre-shipment inspection a procedure to check each drum for pressurization.
 
This can be accomplished by a visual inspection of drum lids and a physical check by pushing
 
on the lid and checking for deflection and/or tapping the lid with a rubber mallet to assess
 
deflection and the tone resulting from the tapping. Any drums suspected of pressurization
 
should be returned to the drumming area and carefully depressurized and opened to confirm
 
conditions and causes, if appropriate. Operators should also develop controls to manage the
 
risk of the addition of excess free moisture/water to open drums of product. The working group
 
is aware that one study indicated that pressure is generated from the addition of water into
 
amorphous product. For example, operators should avoid spraying unsealed drums with water
 
to avoid the possibility of adding free water to the dried product.
 
IN 1999-03, Rev. 1 Enclosure 1 Shipment of Pressurized Drums
 
A facility operator who ships pressurized drums may be in violation of U.S. Department of
 
Transportation regulations. In particular, the shipment of pressurized drums may violate
 
regulations 49 CFR 173.24(b)(3) and 49 CFR 173.475(a). Regulation 173.24(b)(3) states that
 
there will be no mixture of gases or vapors in the package which could, through any credible
 
spontaneous increase of heat or pressure, significantly reduce the effectiveness of the
 
packaging. Regulation 173.475(a) states that, before each shipment of any Class 7 (radioactive) materials package, the offeror (the facility operator who offers the drum for
 
shipment) must ensure, by examination or appropriate tests, that the packaging is proper for the
 
contents to be shipped. Based on these two regulations, a standard metal drum may not be the
 
proper package for pressurized uranium product because the pressurization reduces the
 
effectiveness of the packaging. Further, the packaging process may be inadequate if it allows
 
gases and vapors to increase the internal pressure of the package (the drum), resulting in rapid
 
and uncontrolled depressurization when the package is opened.
 
Facility operators should also be aware of regulation 49 CFR 173.22(a)(4). This regulation
 
requires persons who offer hazardous material for transportation to comply with the
 
manufacturers instructions for packaging. This regulation applies to drums that have been
 
certified by the Department of Transportation and marked or stenciled accordingly. Many drum
 
manufacturers provide specific instructions for proper closure of the drum, including a
 
requirement to torque the drum seals. Facility operators should be aware of any specific
 
closure instructions provided by the manufacturer or distributer of their certified drums, if these
 
drums are used to transport yellowcake material.
 
===Suggestions for the Uranium Recovery Industry===
The working group suggests that the information presented in this IN be supplemented by the
 
uranium recovery industry. The working group suggests that the industry consider expanding
 
the information by determining the chemical species of their product, product temperature
 
versus holding time prior to sealing, impact of excess hydrogen peroxide on the decomposition
 
process, rate of moisture reduction in the dryer, optimum drying parameters (feed rate, temperature, and residence time), and development of procedures and training program to alert
 
workers of the potential risks. For example, facility workers should be made aware that drying is
 
a dynamic process and the change of any process parameter, such as feed rate or dryer
 
temperature, may result in a product that is incompletely dried. Facility operators should use
 
this information to establish site-specific parameters to assure that drum pressurizations do not
 
occur.
 
Facility operators should consider establishing procedures or other protocols to identify and
 
manage pressurized drums. These procedures should include inspections of the drums for both
 
pressurization and integrity prior to transport. This inspection should be complete even if the
 
drum is stored for an extended period of time prior to actual shipment. Finally, the receiver of
 
shipped drums should also inspect drums for pressurization upon receipt and before opening a
 
sealed drum.
 
IN 1999-03, Rev. 1 Enclosure 2 Bibliography
 
Boggs, J. E., & El-Chehabi, M. (1957). The thermal decomposition of uranium peroxide, UO4 *
        2H2O. Journal of the American Chemical Society, 79(16), 4258-4260.
 
Brady, L. J., Susano, C. D., & Lawson, C. E. (1948). Chemical and physical properties of
 
uranium peroxide. Report AECD-2366. Oak Ridge, TN: U.S. Atomic Energy
 
Commission, Technical Information Branch.
 
Cordfunke, E. H. P. (1961). -UO3: Its preparation and thermal stability. Journal of Inorganic
 
and Nuclear Chemistry 23(3-4), 23, 285-286.
 
Cordfunke, E. H. P., & Aling, P. (1963). Thermal decomposition of hydrated uranium peroxides.
 
Journal of the Royal Netherlands Chemical Society, 82, 257-263.
 
Cordfunke, E. H. P., & Van Der Giessen, A. A. (1963). Pseudomorphic decomposition of
 
uranium peroxide into UO3. Journal of Inorganic and Nuclear Chemistry 25(5), 553-554.
 
El-Chehabi, M. (1957). Decomposition of uranium peroxide. (Masters Thesis). The University
 
of Texas.
 
Gayer, K. H., & Thompson, L. C. (1958). The solubility of uranium peroxide in acidic and basic
 
media at 25 °C. Canadian Journal of Chemistry 36(12), 1649-1652.
 
Gupta, C. K., & Singh, H. (2003). Uranium resource processing: Secondary resources. Berlin:
        Springer-Verlag.
 
Harrington, C. D., & Ruehle, A. E. (Eds.). (1959). Uranium production technology. Princeton, N.J.:Van Nostrand.
 
Hausen, D. M. (1998). Characterizing and classifying uranium yellow cakes: A background.
 
JOM 50(12), 45-47.
 
Katz, J. J., & Rabinowitch, E. (1951). The chemistry of uranium: The element, its binary and
 
related compounds (Part I). New York, NY: McGraw-Hill Book Company, Inc.
 
Leininger, R. F., Hunt, J. P., & Koshland, D. E. (1958). Composition and thermal decomposition
 
of uranyl peroxide (Paper 69). Chemistry of uranium: Collected papers, TID-5290,
        Book 2 (704-721). Oak Ridge, TN: U.S. Atomic Energy Commission Technical
 
Information Service Extension
 
Merritt, R.C. (1971). The extractive metallurgy of uranium. Golden, CO: Colorado School of
 
Mines Research Institute.
 
Metzger, R., et al. (1997). Solubility characterization of airborne uranium from an in-situ
 
uranium processing plant. Health Physics 72(3), 418-422.
 
Moore, R. L., & Watts Jr., R. A. (1952). Production of UO3 by calcination of uranyl peroxide, Document No. HW-26531. Richland, WA: Hanford Works.
 
IN 1999-03, Rev. 1 Enclosure 2 Patton, F. S. (1963). Enriched uranium processing. New York, NY: Macmillan Co.
 
Rich, R. L. (2007). Inorganic reactions in water. Berlin: Springer-Verlag.
 
Rodgers, C., & Dyck, B. (2012). Uranium peroxide precipitate drying temperature relationships.
 
CIM Journal 3(3), 149-156.
 
Sato, T. (1961). Uranium peroxide hydrates. Die Naturwissenschaften 48(21), 668.
 
Sato, T. (1963). Preparation of uranium peroxide hydrates. Journal of Applied Chemistry 13(8),
      361-365.
 
Sato, T. (1976). Thermal decomposition of uranium peroxide hydrates. Journal of Applied
 
Chemistry and Biotechnology 26(4), 207-213.
 
Silverman, L. & Sallach, R. A. (1961). Two uranyl peroxides. Journal of Physical Chemistry
 
65(2), 370-371.
 
Thein, S. M., & Bereolos, P. J. (2000). Thermal stabilization of 233UO2, 233UO3, and 233U3O8, Report ORNL/TM-2000/82. Oak Ridge, TN: Oak Ridge National Laboratory.
 
Walenta, K. (1974). On studtite and its composition. American Mineralogist 59, 166-171.
 
The data for Table 1 comes from Laboratory Characterization of Dryer Test Products, Cameco
 
Corporation, Gerhard Heinrich, John Krause, Mike Murchie, November 2009.
 
The data for Figure 1 comes from Laboratory Characterization of Dryer Test Products, Cameco Corporation, Gerhard Heinrich, John Krause, Mike Murchie, November, 2009 but was
 
adapted and updated for a presentation to the CNSC: Rabbit Lake UOC Drying Process, Cameco Corporation, Kirk Lamont, November 2012.
 
IN 1999-03, Rev. 1 Enclosure 3 Survey Results for Facilities Using Hydrogen Peroxide Precipitation
 
Time in Dryer      Dryer      Yellowcake Temp        Cooling and        Percent (%)          Have You Experienced        Suspected Causes of
 
(hours)      Temp (oC)        (oC) When            Venting      Moisture in Dried              Any Drum            Drum Pressurizations
 
Barreled        Time (hours)*      Yellowcake               Pressurizations?
 
12-16          232        Not measured              >12              0 - 1.5                      No
 
Limit of 2
    18-20          164              130                24-72                <1                        Yes              Decay of residual H2O2
    36-48          160              160                  24                  <1                        Yes                  Not determined
 
21-22          163              138                  24                1-8,                      Yes                Moisture vaporizing
 
Typically                                                (steam)
                                                                              3-5
      6            130              <80            Described as              <2                        No
 
minimal
 
16-20          235        Not measured              >12              0.5-1.5                      Yes                Decay of H2O2 and
 
Limit of 2                                      sealing drums too soon
 
4.5-6          649              66            Previously 3,            1-4                        Yes              Cooling time and drying
 
changed to 24                                                              time too short
 
6            371            < 371                  4          no moisture                    Yes                  Decay of H2O2 Unknown        Not given        Unknown          a number of      Not measured                      Yes                Excess H2O2 added
 
hours                                                              during precipitation
 
20-30          150              <90                  12              1-4 w/w                      Yes              Hot yellowcake added
 
to moist drum
 
1.5            245              80                >3                0.5-2.0                      Yes                      Unknown
 
* Cooling and venting times are current times, or the most recent times for facilities that are no longer in operation. Several sites increased their
 
cooling and venting times in response to previous pressurized drum events or in response to IN 1999-03.
 
IN 1999-03, Rev. 1 Enclosure 4 List of Recently Issued Office of Federal and State Materials
 
and Environmental Management Programs Generic Communications
 
Date        GC No.                Subject
 
==Addressees==
11/15/2013  IN-2013-22  Recent Licensing            All materials licensees, certificate
 
Submittals Containing        holders, applicants, and other
 
Personally Identifiable      entities subject to regulation by the
 
Information                  U.S. Nuclear Regulatory
 
Commission for the use of source, byproduct, and special nuclear
 
material. All Radiation Control
 
Program Directors and State
 
Liaison Officers.
 
10/17/2013  RIS-2013-17 Resuming Normal                All U.S. Nuclear Regulatory
 
Interactions Between the    Commission (NRC) licensees, NRC and NRC                  certificate holders, permit holders, Stakeholders Following an    and applicants; all Agreement and
 
Agency Shutdown              Non-Agreement States, and State
 
Liaison Officers; and other
 
interested stakeholders.
 
10/09/2013  RIS-2013-16, Interactions Between the      All U.S. Nuclear Regulatory
 
Supp. 1    NRC and NRC                  Commission (NRC) licensees, Stakeholders During a        certificate holders, permit holders, Lapse of Agency              and applicants; all Agreement and
 
Appropriations              Non-Agreement States, and State
 
Liaison Officers; and other
 
interested stakeholders.
 
10/01/2013  RIS-2013-16 Interactions Between the      All U.S. Nuclear Regulatory
 
NRC and NRC                  Commission (NRC) licensees, Stakeholders During a        certificate holders, permit holders, Lapse of Agency              and applicants; all Agreement and
 
Appropriations              Non-Agreement States, and State
 
Liaison Officers; and other
 
interested stakeholders.
 
09/16/2013    IA-03-02    Criteria for Reporting      All Radiation Control Program
 
Cybersecurity Incidents      Directors and State Liaison
 
Officers. All Increased Controls
 
(IC) materials licensees. All
 
licensees possessing Category 2 and higher materials.
 
IN 1999-03, Rev. 1 Enclosure 4 List of Recently Issued Office of Federal and State Materials
 
and Environmental Management Programs Generic Communications
 
Date        GC No.                Subject
 
==Addressees==
09/11/2013 RIS-2013-14 Reporting Transactions              All industrial radiography and well
 
Involving Temporary            logging licensees, and all Radiation
 
Jobsites to the National      Control Program Directors and
 
Source Tracking System        State Liaison Officers
 
Note: This list contains the six most recently issued generic communications, issued by the
 
Office of Federal and State Materials and Environmental Management Programs. A full listing
 
of all generic communications may be viewed at the NRC public Web site at the following
 
address: http://www.nrc.gov/reading-rm/doc-collections/gen-comm/index.html}}
 
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