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OCR for page 5
2
Occurrences and Origins of Anomalies
OVERVIEW OF ORIGINS OF ANOMALIES
The Army is progressing with CSDP demilitariza-
t~on activities with the goal of completing disposal
activities by 2012 in accordance with an extended dead-
line provided for by the Chemical Weapons Conven-
tion. The U.S. unitary chemical agent and munitions
stockpile contains a variety of agent storage containers
and weapons types, some of which are configured with
bursters, fuzes, and/or propellant charges. Figure 2-1
shows the locations of the eight stockpile storage sites
in the continental United States.
Munitions in the stockpile were last manufactured
in 1968, and some are now almost 60 years old. Con-
cerns about the potential consequences of leakages and
accidents involving degrading stockpile munitions and
containers pending their disposal have been reinforced
by continuing observations of deterioration, corrosion,
and, occasionally, leaks. Leakages have been most fre-
quently encountered in GB M55 rockets, as noted in a
report issued by the Government Accounting Office
(GAO) in December 1994 (see Box 2-1 for the relevant
excerpt). Leaks have continued to occur, with a total of
4,789 leakers reported from 1973 through June 2002
out of more than 3 million munitions (Studdert, 2002~.
iThe small portion of the stockpile that originally existed at
Johnston Atoll in the Pacific Ocean has been destroyed, and
JACADS is undergoing final closure operations.
s
A number of chemical and mechanical anomalies
have frequently led to leaks or have otherwise pre-
sented difficulties during operations at baseline incin-
eration system disposal facilities (Denison et al., 2002;
Thomas, 2002a):
· gelled agent (GB)
· crystallized agent (GB)
· sludged agent (HD)
· randomly occurring heavy metals, which create
problems in meeting stack emission limits during
processing
· foaming mustard agent
· internal pressurization of munitions from hydro-
gen gas generation
· various mechanical anomalies such as fabrication
discontinuities (cracks and scratches) and unex-
pected obstacles to disassembly (such as diffi-
culty in loosening screw threads)
A promising approach for developing a predictive
method to help assess the formation and future fre-
quency of leaks is to combine an understanding of
the chemistry of agent manufacture and degradation
processes (including those associated with stabiliz-
ers added to the agents) with a statistical analysis of
data accumulated to date on stockpile leaks. This
chapter discusses the stockpile in terms of what is
known about the original manufacturing processes,
OCR for page 6
6 EFFECTS OF DEGRADED AGENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
Um villa Chemical ~ ZJ TO ~ -
HD -P°TC ~ ~ f:' = —
~ ~ ~ 1 1 1 ~ _ ~
De:~3ret ChDmical ~ ,~ In_
GB - C9 P' R. B. TC
VX-P,R,M'ST
GA-TC
(44.5°/0)
-
\: /7 ~ L
Pueblo Chemical /
Depot /
MD-C, P
HT-C
(8.5%)
GA, GB, VX, H. HD, HT = Chemical agent
TC = Ton container B = Bombs
R = Rockets C = Cartridges
M = Mines P = Projectiles
ST = Spray tanks
Newpori
Chemical
Depot
VX -TC
(4.2%)
Edgewood
Chemical
Activity
HD -TC
(5.3%)
Blue Grass
Chemical
ACtMtY
HD- P
GB- P. R
VX - P. R
(1.7%)
~ \-
Chemical
ACtM1Y
MD-C, PITC
HT - C
GB- C, P. R
FIGURE 2-1 Location and size (percentage of original stockpile) of eight continental U.S. storage sites. Source: OTA (1992~.
the chemistry of the agents, the configurations of mu-
nitions containing agents, and applicable corrosion
mechanisms.
DESCRIPTION OF MUNITIONS AND CONTAINERS
A detailed description of the original stockpile is
given in Chemical Stockpile Disposal Program Final
Programmatic Environmental Impact Statement
(FPEIS) (U.S. Army, 1988a) and can also be found in
the NRC report Disposal of Chemical Munitions and
Agents (NRC, 1984~. Both reports and a later NRC re-
port, Recommendations for the Disposal of Chemical
Agents and Munitions, address earlier expressions of
concern about the potential impacts of a degrading
stockpile on disposal operations (NRC, 1994a).
As noted in Chapter 1, the stockpile contains three
main agent types:
· GB (sarin),2 a fairly volatile (2.9 mm Hg at 25°C),
2Methylphosphonofluoridate isopropyl ester.
highly toxic (LD50= 24 mg/kg) nerve agent
(NRC, 1993, 1997a)
VX,3 a much less volatile (0.001 mm Hg at 25°C)
but more toxic (LD50= 0.14 mg/kg) nerve agent
(NRC, 1993, 1997a)
H,4 HD,5 and HT6 (sulfur mustards), blister
agents with moderate volatility (vapor pressures
0.08 to 0.11 mm Hg at 25°C) and moderate toxic-
ity (LD50= 100 mglkg) (Munro et al., 1994; NRC,
1997a).
The stockpile also included some nerve agent GA
(tabun),7 which is similar to GB. However, all GA was
stored at DCD in Utah and has been destroyed along
with all of the GB that was stored there. A small amount
3a nerve agent, O-ethyl S-~2-diisopropylaminoethyl) methyl-
phosphonothiolate.
4Bis(2-chloroethyl) sulfide.
Distilled H.
660 percent HD and 40 percent T. which is bis[2~2-chloro-
ethylthiojethyl] ether.
7Ethyl-N,N-dimethylpho sphoramidocyanidate.
OCR for page 7
OCCURRENCES AND ORIGINS OF ANOMALIES
of lewisite,8 an organic arsenical blister agent, remains
in the stockpile.
A variety of containers and munitions compose the
chemical stockpile, some of which are depicted in
~Dichloro(2-chlorovinyl~arsine.
7
Figure 2-2. Containers include bombs that are stored
without explosives, aerial spray tanks, and bulk stor-
age tanks known as ton containers. Munitions include
land mines, M55 rockets, artillery projectiles, and mor-
tar projectiles. Munitions typically contain some com-
bination of fuze, booster, burster, and propellant col-
lectively referred to as "energetics."
Table 2-1 indicates which munitions incorporate
energetics. The fuze is a small, highly sensitive ex-
plosive charge that initiates an explosive chain by
detonating a booster. The booster is a medium-size
charge that can be detonated by the fuze and is large
enough to detonate a much larger burster charge. The
burster charge is large enough to rupture the muni-
tion and to disperse the agent contained within. The
M55 rocket also incorporates a section of solid
rocket propellant. Dunnage refers to munition pack-
ing materials, which also may be destroyed by com-
bustion.
Most of the munitions in the stockpile have been
stored inside igloos that provide protection from the
elements. The enclosed space of the igloo facilitates
the monitoring performed to detect leaks and limits the
quantities of agents and energetics that are likely to be
involved in any single accident. Some bulk ton con-
tainers had been stored outdoors but were more recently
moved into enclosed shelters to enhance their security.
When leaking items are found, they are overpacked
(placed inside another container and sealed) and re-
turned to storage. Some leakers have been overpacked
several times.
Problems with degraded items in the stockpile affect
the safety of workers engaged in the maintenance of
the stockpile and the transport of stockpile items from
storage areas as well as that of workers involved in
disposal operations. For example, workers in protec-
tive clothing perform the overpacking procedure and
also decontaminate any area that has been affected by a
leak. In general, hazards to workers may arise from
conditions such as the following:
agent leakage
· potential ignition of energetics by a spurious elec-
tric discharge
instabilities of stabilizers used in energetics-
especially the stabilizer in the M55 rocket
propellant
interactions between agent, energetics, and/or
structural materials
undetected manufacturing flaws
OCR for page 8
8 EFFECTS OF DEGRADED A GENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
(a)
Fumed
Fins ~ Rocket
Motor
f Cavity
Douglass Shipping
and Fire -
at"
~°'
Aluminum ~ -.'
(at each End)—~ ~ /
/
/
/
/
~ Agent Fill
I—Bonnet
r valve
| ~ Eduction Tube
(C)
~ 1~117f
Agent Fill ~
FIGURE 2-2 (a) MSS rocket; (b) 105-mm projectile; (c) ton container. Source: U.S. Army (2002a).
OCR for page 9
OCCURRENCES AND ORIGINS OF ANOMALIES
TABLE 2-1 Composition of Munitions in the U.S. Chemical Stockpile
Munition Type Agent Fuze Burster Propellant Dunnage
MSS 115-mm rocketsa GB, VX Yes Yes Yes Yes
M23 land mines VX Yesb Yes No Yes
4.2-inch mortars Mustard Yes Yes Yes Yes
105-mm projectiles GB, mustard yesc yesc No Yes
155-mm projectiles GB, VX, mustard No YesC No Yes
8-inch projectiles GB, VX No Yes No Yes
Bombs (500-750 lb) GB No No No Yes
Weteye bombs GB No No No No
Spray tanks VX No No No No
Ton containers GB, VX, GA,4 No No No No
mustard, lewisitee
aMSS rockets are processed in individual fiberglass shipping containers.
bFuzes and land mines are stored together but not assembled.
CSome projectiles have not been put into explosive configuration.
dGA (tabun), or ethyl-N,N-dimethyl phosphoramidocyanidate, is a nerve agent.
eLewisite, or dichloro(2-chlorovinyl) arsine, is a volatile arsenic-based blister agent.
Source: U.S. Army (1988a).
Chapter 4 describes some specific risks to work-
ers that have been encountered during disposal op-
erations.
MANUFACTURING PROCESS ORIGINS OF
ANOMALIES
The manufacture of the agents in the stockpile and
munition components took place at several locations over
a long period of time. This section provides a brief over-
view of how manufacturing processes and specifications
have contributed to anomalous items in the stockpile.
Agent Characteristics
GB
GB was manufactured at Rocky Mountain Arsenal
(RMA) from 1953 to 1957 and stored by manufactur-
ing lot in bulk tanks before being loaded into muni-
tions or, in the 1960s, into the current storage contain-
ers. The purity of GB agent was originally specified at
92 percent, and tributylamine ETBA, (C4Hg)3N] was
used as the stabilizer (U.S. Army, 1986a). During the
first 2 years of GB production, between 1953 and 1955,
the Army produced GB by a two-step distillation pro-
cess that met the 92 percent purity specification. How-
ever, from 1955 to 1957, the Army eliminated the sec-
9
ond distillation step, which reduced agent purity to
about 88 percent.
Each batch of GB manufactured in 1953-1957 at the
RMA was assigned an agent lot number. Differences in
the production methods and the subsequent treatment
of these lots are documented in Army records. In the
1960s, the bulk agent was loaded into a variety of con-
tainers and munitions that are identified by a munitions
lot number. Thus, each item in the stockpile is identi-
fied by both an agent lot number and a munitions lot
number. Since the decomposition products of GB were
known to be acidic, stabilizers were added to scavenge
acidic decomposition products and water as they
formed.
There are currently four main subtypes of GB agent:
PRO, PR-RS, RO-RS, and RD-RS. These subtypes
arise from combinations of the following designations,
because agents of different initial purity were treated in
different ways:
PRO (preroundout agent) was manufactured
from 1953 to 1955 to meet a 92 percent purity
specification. TBA was added as a stabilizer.
Subsequent testing of these stored agent lots
showed purities ranging from 81 to 94 percent,
indicating a widely varying degree of decom-
position (U.S. Army, 1985~. The TBA was
mostly in the form of (C4Hg)3NH+F-, possibly
OCR for page 10
10 EFFECTS OF DEGRADED A GENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
indicating the formation of HF. Varying
amounts of diisopropyl methyl phosphonate
(DIMP) and methylphosphonofluoridic acid
(MPFA) were also found in the agent: 2 to 6
percent by weight DIMP and 2.7 to 10 percent
by weight MPFA.
RO (roundout agent) was manufactured from
1955 to 1957 to meet a modified purity goal
of 88 percent. The Army continued to test the
agent lots over the next few years and found
that the RO lots were showing significant
acidity. Since some of the agent was intended
for use in aluminum M55 rockets, there was
concern that acidity would cause corrosion
problems. For this reason, over the next 6
years, some RO lots were redistilled to im-
prove purity.
RD (redistilled RO). In addition to the redistil-
lation of some RO lots, the TEA stabilizer was
replaced by DICDI (diisopropylcarbodiimide)
to reduce the acidity problems and allow the
placement of GB into aluminum casings.
RS. Lots restabilized with DICDI were des~g-
nated by the addition of RS to the basic agent
category. M55 rockets were loaded with GB
from various agent lots during the 1960s.
.
.
.
VX Nerve Agent
VX was originally manufactured from 1961 to 1968
at Newport, Indiana. It was 92 to 95 percent pure and
had approximately 2 percent added stabilizer (usually
DICDI, less frequently dicyclohexyl carbodiimide).
When the agent fills were sampled in 1975, the VX
content had decreased by 2 to 7 percent, and in some of
the lots, about half the DICDI stabilizer had decom-
posed (U.S. Army, 1995a). Unlike GB, the VX was
never redistilled or restabilized. The fact that a large
fraction of the stabilizer had decomposed within 15
years of manufacture and that the VX has not been re-
distilled or restabilized suggests that little stabilizer
may remain after the 28 additional years that have
elapsed since 1975.
Mustard Agent
Mustard agent was produced at RMA from 1942 to
1945 by the Levinstein process. This produced the form
of mustard that is designated H along with sulfur, which
was removed by washing. From 1945 to 1946, most of
this product was then vacuum-distilled at RMA to pro-
duce HD. HD was also manufactured at Aberdeen
Proving Ground, in Maryland, using a 500-gallon
vacuum distillation still and five vertical reflux con-
densers. The initial HD content of mustard agent manu-
factured circa 1945 was reported to be 94 percent, with
less than 0.005 percent (50 ppm) HC1 content. When
sampled in 1982, the HD content had decreased to be-
tween 50 and 89 percent, with most analyses indicating
less than 85 percent. The agent fills also contained ap-
proximately 0.2 percent Fe++ ion, indicating partial dis-
solution of the steel container material by acidic impu-
rities or by HC1 that came from hydrolysis of the agent
(U.S. Army, 1995a).
Munition Assembly, Quality Control, and Component
Compatibility
In the 1960s, when the bulk agents were introduced
into the various stockpile munitions and containers,
the specification and manufacturing procedures for
the assembly of munitions was controlled to a level of
quality that ensured the requisite functionality and a
reasonably stable storage life. These specifications
covered agent purity, energetics type and configura-
tion, and component metal parts, along with assembly
sequences and joining and sealing procedures. Ranges
of acceptable variability in properties were also pro-
vided. Agent and munitions lots were systematically
identified by type and numbered to allow future trace-
ability. However, the possibility that disassembly and
deactivation might be necessary at a future date was
not considered in the design of the munitions. More-
over, when these munitions were manufactured 30 to
60 years ago, chemical analysis and mechanical as-
sembly techniques were less sophisticated than they
are now, making it possible for anomalies to have
been introduced into the munitions during the initial
manufacturing.
Some anomalies were discovered early in the disposal
program for example, the brass valves and plugs that
were used on GB ton containers were found to have been
attacked by the acidic products of GB decomposition,
which leached the zinc from the brass alloy in the plug
material. These fittings were subsequently replaced with
steel fittings on all the ton containers.
One common type of anomaly munitions contain-
ing either GB or mustard agent that has gelled has con-
sequences for the conduct of disposal operations. This
phenomenon occurs with age. In the case of GB, gelling
OCR for page 11
OCCURRENCES AND ORIGINS OF ANOMALIES
is probably related to reactions between GB degradation
products and aluminum. For mustard agent, sludging is
associated with the formation of dithianium ion. Another
anomaly that became apparent during the disposal of
mustard munitions, specifically projectiles, has been at-
tributed to impurities that may lead to a slow, gas-pro-
ducing reaction. During demilitarization operations at
JACADS, some projectiles with mustard agent foamed
when the burster well was extracted; this was due to the
buildup of internal pressure.
A more pressing concern in terms of the risks asso-
ciated with continued storage of the stockpile is the
stability of the M28 propellant used in M55 rockets.
This propellant includes nitrocellulose, which is un-
stable, decays exothermically, and is autocatalyzed by
its own acidic nitrate products. During manufacture, a
stabilizer that reacts with the acidic nitrate products
to prevent autocatalysis was added, although nitrocel-
lulose decay itself is not inhibited. M55 rockets were
manufactured from 1959 to 1965, with stabilizer con-
tent averaging about 1.8 percent (U.S. Army, 1985~.
Initial stabilizer decays continuously over time. The
Army has set a level of 0.5 percent stabilizer as the
"increased surveillance threshold" and has observed
autoignition at levels of 0.2 percent under controlled
conditions (NRC, 1994a). Sampling of stabilizer lev-
els over time has not shown variability beyond what
might be expected from degradation alone. In 1985,
393 M55 rockets were randomly selected from
478,000 rockets in the stockpile, and stabilizer levels
were found to be between 1.6 and 2.2 percent. Since
the precise starting concentrations for individual lots
were unknown (there was considerable variability
around the 1.8 percent initial nominal concentra-
tion),9 rates of degradation could not be inferred
9According to the 1985 study by the Army Materiel Systems
Analysis Activity, the first evaluation of M28 propellant stockpiled
since production, the original stabilizer content at the time of manu-
facture ranged from 1.57 to 2.17 percent of total weight (U.S. Army,
1985~. In that study, lots stored at Johnston Island had an average
stabilizer content of 1.63 percent (95 percent confidence interval of
1.60 to 1.66 percent). These lots exhibited the largest stabilizer loss
of all locations. Four lots produced in 1960 and stored at Pine Bluff
had low original stabilizer content (1.62 percent), and the report
noted the current assay average was 1.45 percent (95 percent confi-
dence interval of 1.45 to 1.53 percent) [sic]. The remaining lot seg-
ments for all locations (except Johnston Island) were found to be
homogeneous. The average stabilizer for these lots was 1.76 per-
cent (95 percent confidence interval of 1.75 to 1.77 percent).
11
(OTA, 1992~. Similarly, too little stabilizer might
have been added during manufacture in some cases.
The degradation of M28 propellant is discussed in
more detail later in this chapter.
Another problem is the corrosive effect of GB agent
degradation products on the aluminum of which M55
rockets are constructed. This corrosion has been re-
sponsible for the majority of leakage problems with
these rockets. Aluminum was used in these rockets to
achieve certain aerodynamic characteristics.
Among the manufacturing flaws that might acceler-
ate corrosion in chemical munitions and containers are
(1) the use of dissimilar metals for junctions, leading to
electrochemical reactions, and (2) the improper clean-
ing of welded parts. However, subsequent observations
of leakage sources suggest that these are not important
causes of corrosion problems.
While anomalies that arose during manufacturing
and initial filling can present unique operational issues
during disposal, the long history of storage to date sug-
gests that most manufacturing causes have already been
identified from an examination of stockpile items that
have leaked. For example, lead, cadmium, and mer-
cury are occasionally identified in ton containers that
were reused by the Army, and it is possible that these
heavy metals were residual contaminants, even though
the containers were presumably cleaned before refill-
ing. In munitions, the presence of lead may have come
from lead-based solder, lead compounds in energetic
materials, or lead components in fuze assemblies. The
presence of mercury, which has been found in ton con-
tainers, may be the result of pressure gauge breakage
and splashback during filling operations or residual
contamination.
DETERIORATION PROCESSES FOR AGENTS
Surveillance of Agent Deterioration
As noted above, the chemical agents stored in the U.S.
stockpile were originally manufactured 30 to 60 years
ago. The purity of the agent contained in various muni-
tions and bulk containers was sporadically checked dur-
ing the 1960s and 1970s (U.S. Army, 1985, 1995a). Fol-
lowing recommendations from a blue ribbon panel
convened in March 1983 to review the chemical retalia-
tory surveillance and sampling program, the Surveil-
lance Program for Lethal Chemical Agents and Muni-
tions (SUPLECAM) was established for purposes that
included the following (U.S. Army, 1988b):
OCR for page 12
12 EFFECTS OF DEGRADED AGENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
· determining the rate of agent decomposition
.
~7 ~7 1
gaining an improved understanding of the mecha-
nisms of decomposition and stabilization of
agents, specifically GB and VX.
The SUPLECAM studies, carried out by the U.S.
Army Chemical Research, Development, and Engi-
neering Center (CRDEC), developed a substantial
quantity of data on degradation kinetics and mecha-
nisms for GB and VX. This blue ribbon panel offered
recommendations on seven items:
1. Are surveillance plans and procedures good
enough to determine the current condition of the
stockpile?
2. How can the surveillance plans be improved?
3. What further tests or analyses can be performed
to provide useful information?
4. Is field testing necessary or desirable?
5. What will be the condition of the munitions by
1990? (The assumption then was that binary muni-
tions would be available and the existing stockpile
would be available for demilitarization.)
6. What additional data analysis or studies are
needed to improve predictions about the condi-
tion of these munitions?
7. Can anything be done to prolong the life of the
stockpile?
The panel recommended the immediate funding of
SUPLECAM "to study VX decomposition as a func-
tion of time, temperature, inhibitors, and impurities"
(U.S. Army, 1988b). Accelerated aging tests were con-
ducted with and without inhibitors. Also, viscosity
measurements were taken on pure and partially decom-
posed agent to determine if thickening or precipitation
of the agent had occurred (U.S. Army, 1988b). This
work led to intrusive sampling to obtain the necessary
VX samples from the stockpile. The samples were
stored in glass containers and sent back to the Army' s
Edgewood, Maryland, facilities for kinetic and mecha-
nistic studies. An important finding was that the DICDI
inhibitor decomposes in the presence of water to form
urea crystals but does not readily decompose in the
absence of water. The SUPLECAM program extended
through the 1980s, but similar sampling efforts have
not been conducted since that time.
Mechanisms and Products of Agent Deterioration
Over time, mustard and nerve agents can undergo
chemical decomposition. In this section, the mecha-
nisms and products of such decomposition are dis-
cussed in greater detail. Table 2-2 shows the products
resulting from the degradation of nerve and mustard
agents. Details of the decomposition pathways for in-
dividual agents have been discussed extensively
(Munro et al., 1999; NRC, 2001a) and are summarized
below.
GB
Three pathways, shown below, have been identified
for the degradation of GB in storage (U.S Army, 1986b,
1988c, 1999a). GB can reversibly form DIMP and DF
(Pathway I). The P CH3 bond is the most resistant to
TABLE 2-2 Expected Products from Chemical Agent Decomposition Due to Age
Agent
Decomposition Products
VX
GB
Mustard (HD)
Thiolamine; ethylmethylphosphonic acid; ethanol; bis(2-diisopropylaminoethyl) thioether; bis(2-
diisopropylaminoethyl) disulfide; o,o'-diethylmethyl phosphonolate; o,o'-diethylmethyl phosphonothiolate;
diisopropylaminoethyl mercaptan; o,S-diethyl methyl phosphonothiolate; diisopropylaminoethylethyl
sulfide; o,S-diethyl methyl phosphonate; N,N'-diisopropylamino ethyl methyl phosphonate; S-ethyl, S-
diisopropyl amino ethyl methyl phosphonothiolate; o-ethyl, S-diisopropyl amino ethyl methyl
phosphonothiolate; S'-diisopropyl amino ethyl methyl phosphonothiolate; diisopropylamine
HF; isopropyl methylphosphonic acid (IMP); isopropanol; propene; methyl phosphono fluoridate;
diisopropyl methyl phosphonate (DIMP); methylphosphonic acid (MPA)
HC1; H2S; ethylene; ethylene dichloride; vinyl chloride; 2,2'-dichlorodiethyl disulfide
Source: U.S. Army (1988a).
OCR for page 13
OCCURRENCES AND ORIGINS OF ANOMALIES
hydrolysis. The P F bond is hydrolyzed (Pathway III)
more rapidly than the P OC3H7 bond (Pathway II).
(I) Reversible disproportionation of GB to form
diisopropyl methyl phosphonate (DIMP):
O O O
2 CH3P F CH3P OC3H7 + CH3P F
OC3H7 OC3H7 F
GB DIMP DF
(II) Acid-catalyzed hydrolysis to form methyl phospho-
nofluoridic acid (MPFA):
O H+ O
CH3P F > CH3P F + C3H6 (g)
OC3H7 OH
GB MPFA
(III) Neutral hydrolysis to form isopropyl methyl
phosphoric acid (IMPA):
1I H2O 11
CH3P F > CH3P OH + HF
1 1
OC3H7 OC3H7
GB IMPA
The DIMP product of the disproportionation reac-
tion can be further hydrolyzed to form IMPA, which
can undergo a slow further hydrolysis to form methyl
phosphoric acid (MPA):
1I H+ 11
CH3P OC3H7 > CH3P OH + C3H6 (g)
OC3H7 OC3H7
DIMP IMPA
1I H+ 11
CH3P OH > CH3P OH + C3H6 (g)
OC3H7 OH
IMPA MPA
MPFA, IMPA, and MPA are all acidic and thus
may be expected to further accelerate GB decomposi-
tion by the autocatalytic process described below. In
experiments in which small amounts of these com-
pounds were added to GB, the acceleration effect was
in the order MPA > IMP ~ MPFA ~ water. In the
presence of ferrous metals such as those used in many
munitions, and if not inactivated by a stabilizer com-
pound, these acidic compounds would be expected to
react at the inner metal surface of the munition to lib-
erate hydrogen:
Steel + 2 HA > Fe++ + 2 A- + H2 (9)
where HA is an acidic compound. Aluminum will react
with the HF produced in Pathway III (above) to form
A1F3 and liberate hydrogen gas:
Aluminum + 3 HF ~ A1F3 + 3/2 H2
The A1F3 can complex with additional fluoride ion
to form A1F4- or the highly stable A1F63- anion.
Two factors that could affect GB decomposition
rates need to be considered: autocatalytic processes and
rate acceleration at higher temperatures. Since the prod-
ucts of GB decomposition are themselves acidic and
several of the decomposition pathways noted above are
acid-catalyzed, it is possible that the decomposition
process could proceed by an autocatalytic mechanism
once the added stabilizer has been exhausted (Munro et
al., 1999). One characteristic of an autocatalytic pro-
cess is a lengthy induction period during which little or
no reaction occurs, followed by a sudden rapid increase
in the overall reaction rate (Steinfeld et al., 1999) (see
Figure 2-3). An autocatalysis rate law for GB decom-
position has been suggested:
[GB] = [GB] jnjtja, (ks + ku [GB]initial )
t ku [GB]initia' + ks exp{(ks + ku [GB]initial )(t - tI )}
where EGB]initial is the concentration at time tI, when all
of the stabilizer is consumed, and [GB]t is the concen-
tration of GB remaining at time t. The GB loss rate
coefficients are ks and ku, in the presence and absence
of stabilizer, respectively (U.S. Army, 1985, 1986a).
On the basis of very limited data, it has been suggested
that loss of GB could begin to accelerate at t 2 30 years
(U.S Army, 1986a).
Many reaction rates increase at higher temperatures
according to the Arrhenius rate law (Steinfeld et al.,
1999)
k(l) = A exp (-Eac,/RT)
OCR for page 14
14
o
AL
o
o
. _
cat
o
FIGURE 2-3 Autocatalysis rate profile, product concen-
tration versus time; t* is the inflection time, i.e., the time at
which product formation occurs most rapidly. Source:
Adapted from Steinfeld et al. (19991.
where A is a preexponential factor, Earl is the activa-
tion energy, R is the gas constant, and T is the tempera-
ture in kelvins (°C + 273.16~. Measurements at elevated
temperatures give Arrhenius activation energies for
Pathways I and II above as 28.3 kcal/mole and 25.4
kcal/mole, respectively (U.S. Army, 1999a). Analysis
of SUPLECAM results on overall decomposition rates
suggests an effective activation energy of 31 kcal/mole,
which is within 20 percent of an earlier result reported
in the United Kingdom (U.S. Army, 1999a) but based
on only two data points. While Arrhenius behavior
would suggest an accelerated decomposition rate for
GB at higher temperatures, the data presented in Chap-
ter 3 do not show any clear dependence of munition
leak rate on ambient temperature.
As previously noted, all of the GB that was stored
on Johnston Island and at DCD has been destroyed at
JACADS and TOCDF, respectively. Gelling of the
agent was encountered in about 12 percent of the GB
munitions in the DCD stockpile (EG&G, 2002~. GB
gelling had previously been encountered in only a few
155-mm GB-filled projectiles during processing at
JACADS. The degree of gelling ranges from increased
viscosity that slows the draining process to a semisolid
state or to a crystallized state, either of which makes it
impossible to drain agent after the agent cavity of the
rocket has been punched open.
EFFECTS OF DEGRADED AGENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
Gel formation has been attributed to the formation
of aluminum phosphonate complexes.l° The A13+ ions,
formed during the acidic corrosion of aluminum muni-
tion parts, can react with the IMPA- ions formed in
Pathway III to form a trig-isopropyl methyl phospho-
natoaluminate complex:
o
3CH3P O + Al3+ ~ Al[OP(0)CH3OCH(CH3)2]3
OC3H7
GB
which has the following suggested structure:
H3C,...,
Ol','n'\~
H3C\ `\\\'o BALI j
(CH3)2 CHO (CH3)2 CHO
The complexes, which are mostly viscous liquids, can
form either a solid that is sparingly soluble in GB or
oligomeric or polymeric phosphorus compounds.l2
Complexes can also form as a result of reaction with
nickel or copper ions produced from the corrosion of
other metal parts, such as brass fittings.
Another mechanism that has been suggested for the
formation of crystalline solids in stored GB is the for-
mation of 1,3-diisopropyl urea when DICDI (the stabi-
lizer added to -RS lots) reacts with water in the pres-
ence of acid.l3
Cl H3 Cl H3 H+ 1 3H 11 H 1 3
HC N = C=N CH + H:,O > HC N C N CH
CH3 CH3
1 - 1 1
CH3 CH3
diisopropyl carbodiimide (DICDI) 1,3-diisopropyl urea
10Yu-Chu Yang, Chief Scientist PMACWA, personal communica-
tion to the committee on June 27, 2003. Also see Wagner et al. (2001).
1lYu-Chu Yang, Chief Scientist PMACWA, personal communica-
tion to the committee on June 27, 2003. Also see Wagner et al. (2001).
12Yu-Chu Yang, Chief Scientist PMACWA, personal communica-
tion to the committee on June 27, 2003.
13Yu-Chu Yang, Chief Scientist PMACWA, personal communica-
tion to the committee June 27, 2003. See also U.S. Army (2002b).
OCR for page 15
OCCURRENCES AND ORIGINS OF ANOMALIES
This hypothesis is supported by the fact that urea crys-
tals were observed during the filling of rockets and pro-
jectiles when GB agent RS lots were used (U.S. Army,
2002b).
VX Nerve Agent
Hydrolysis of VX agent occurs by cleavage of the
P S bond under acidic or alkaline conditions or by
cleavage of the P ethoxy bond under near-neutral
conditions (Munro et al., 1999; NRC, 2001a):
/CH(CH3~2 ~~
HS-CH2CH2-N + C2H5O-P-OH
CH(CH3~2 C ~ 3
,~` diisopropyl ethyl ethyl methyl-
~,~ mercaptoamine phosphoric acid
O /CH(CH3~2
C2HsO- P-SCH2CH2-N
~ H3 \ CH(CH3~2
Agent VX ~~ ~~ CH(CH3~2
to HO-~-SCH2CH2-N + C2H5OH
CH3 CH(CH3~2
S-~2-diisopropylaminoethyI) ethanol
methyl phosphonothioate
(EA-21 92)
The latter pathway yields the toxic degradation prod-
uct EA-2192. Other reaction products are listed in
Table 2-2. Since the electron-donating tertiary amine
group present in VX makes this agent a Lewis base, the
hydrolysis rates are slow (Wojciechowski and Goetz,
2002~. As a consequence, VX is expected to have a
long storage lifetime, with little or no acidic attack on
steel containers and little or no bimetallic electrochemi-
cal reaction at metal junctions. But since VX is a highly
toxic material, these assumptions may need to be veri-
fied, as a precaution. Note that at least one of the de-
composition products above (ethyl methylphosphonic
acid) is acidic. An Arrhenius activation energy of 23
kcal/mole has been estimated for VX decomposition
(Evans, 1999~.
15
OCR for page 16
16 EFFECTS OF DEGRADED AGENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPE^TIONS
Mustard Agent
Mustard agent H (bis-2-chloroethyl sulfide) under-
goes the complex sequence of hydrolysis reactions
Cl-CH2-CH2-S-CH2-CH2-CI
Suffur mustard (HD)
1 H2O
r -Cl-
+yCH2
Cl-CH2-CH2-S\ CH
2
sulfonium ion
thiodiglycol
r
H2O
> S;
/ CH2-CH2-S-(CH2-CH2-OH)2
\ CH2-CH2-CI
sulfur mustard-
thiodiglycol aggregate
~ thiodiglycol /~
J~-CI- /
/ H2O
CH2-CH2-S-(CH2-CH2-OH)2
CH2-CH2-S-(CH2-CH2-OH)2
sulfur mustard-thiodiglycol-
thiodiglycol aggregate
shown below (Bizzigotti et al., 1998; Munro et al.,
1994; NRC, 2001a).
/ CH2-CH2-CI H2O S / CH2-CH2-OH
'CH2-CH2{)H
hemimustarcl
\ CH2-CH2-OH
thiodiglycol
thiodiglycol ~ H2O
-CI- ~
H2O S / CH2-CH2-S-(CH2-CH2-oH)2
\ CH2-CH2-OH
hemimustard-
thiodiglycol aggregate
OCR for page 17
OCCURRENCES AND ORIGINS OF ANOMALIES
A further degradation mechanism is responsible for
the formation of the solid or semisolid residues
("heels") that are present at 20-30 percent of the total
volume of HD in stored ton containers. Recent tests on
mustard-filled projectiles stored at DCD found that up
to 70 percent of the agent fill was present as heels
(Novad, 2003~. The main constituents of these heels
have been identified as a cyclic six-membered ring sul-
fonium ion, S-~2-chloroethyl)- 1,4-dithianium chloride,
entrained HD, and dissolved iron (Yang et al., 1997~.
The mechanism responsible for the formation of the
dithianium ion is as follows:
2/~1 - H rich \= HI - H AH = - H AH =+/ - H AH - 1\
` - ~ 2 - 2)~ > ~ ~ 2 - 2~ - 2 - 2~ ` - 2 - 2 - )2
Cl-
CICH2CH2SCH2CH2SCH2CH2CI + C2H4CI2
S/:S
—Cl
The dithianium ion has been identified and charac-
terized by 13C cross polarization magic angle spinning
nuclear magnetic resonance and by liquid chromatog-
raphy/electrospray mass spectrometry (Rohrbaugh and
Yang, 1997; Wagner and Yang, 1999~. Both the hy-
drolysis and heel-forming reactions can lead to corro-
sion of the steel container materials as well as the brass
valves and fittings that were used originally in the bulk
(ton) containers. Hydrochloric acid reacts with iron to
produce ferrous chloride and liberate hydrogen gas; the
latter is responsible for the frothing ("champagning")
encountered when some mustard rounds are opened.
Thiouronium salts absorbed on steel surfaces can also
lead to corrosion via a dehydrohalogenation-like
mechanism, giving Fe++ ion, vinyl chloride, dithiane,
and hydrogen. All of these products of mustard decom-
position have been observed during sampling and
analysis programs conducted by the Army, including
SUPLECAM.
In recent tests, mustard-filled projectiles stored at
DCD were opened and drained at CAMDS in prepara-
tion for agent destruction at PUCDF. It was found that
i4"Champagning" is sometimes used by the Army to describe this
reaction and its manifestation during projectile opening operations.
17
in many cases only 3 to 4 lb of the 11 lb of agent fill
could be drained; the rest of the material remained so-
lidified in the munition casing (Novad, 2003~.
DETERIORATION PROCESSES FOR ENERGETIC
MATERIALS
At the time this report was prepared, the chemical
stockpile included 367,000 M55 rockets (276,000
GB; 91,000 VX), each filled with 10.7 lb of GB or
10.1 lb of VX, respectively. To date, more than 80,000
M55 rockets have been destroyed in the campaigns at
JACADS and TOCDF. Since these rockets were
manufactured in the early to mid-1960s, the average
age of the remaining rockets is now about 40 years.
Deterioration of energetic materials has been recog-
nized as a potential source of autoignition in these
rockets. A series of studies and reports has investi-
gated this issue (e.g., GAO, 1994; NRC, 1994b; U.S.
Army, 1988d,1994~. More recently, a comprehensive
and substantive evaluation of the autoignition poten-
tial, drawing on past theoretical and empirical stud-
ies, concluded that risk of autoignition is small com-
pared with risk of ignition from external sources such
as lightning strikes (U.S. Army, 2002c). See Table
4-3 for details.
Nevertheless, because GB M55 rockets have been
identified as posing increased risk and because of the
uncertainties inherent in the risk estimates, the
Army's decision to expedite their destruction early in
the disposal schedule for each site is certainly pru-
dent. Although M55 rockets containing VX are less
likely to autoignite than those containing GB, the dis-
posal of rockets in general remains a priority.
OBSERVED LEAK FACTORS AND OCCURRENCES
BY MUNITION TYPE
A memorandum dated April 10, 1996, from Donald
E. Brooke summarizing postmortem investigations
conducted on chemical munitions was used as a frame-
work for the information on leakers and factors con-
tributing to such occurrences that is presented in Ap-
pendix B (U.S. Army, 1996b).
SUMMARY
This chapter, with Appendixes A and B. provides a
fairly detailed description of the degradation processes
affecting chemical agents and (to a lesser degree) pro-
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18 EFFECTS OF DEGRADED A GENT AND MUNITIONS ANOMALIES ON CHEMICAL STOCKPILE DISPOSAL OPERATIONS
pellants in stored munitions. While stabilizers were
added to GB and VX at the time of manufacture to
retard decomposition, these stabilizers have degraded
over time. The resulting acidic decomposition prod-
ucts may corrode metal containment vessels, leading
to agent leakage (particularly for GB ). The decompo-
sition mechanism is such that agent degradation may
be expected to accelerate at elevated temperatures and
longer storage times; these hypotheses are explored in
Chapter 3.
Additional anomalies were identified that may af-
fect subsequent processing of munitions in demilitari-
zation activities. These include mechanical defects,
improperly assembled munitions, gelling or solidifica-
tion of agent fills, pressurization, and contamination
by substances such as lead or mercury. The processing
consequences of these anomalies are explored further
in Chapter 4.
Representative terms from entire chapter:
chemical stockpile
