[DNFSB
LETTERHEAD]
September 7, 2005
Mr. James A. Rispoli
Assistant Secretary for
Environmental Management
U.S. Department of Energy
1000 Independence Avenue, SW
Washington, DC 20585-0113
Dear Mr. Rispoli:
The Defense Nuclear Facilities
Safety Board (Board) is aware that the Office of River Protection (ORP) has
embarked on the design and construction of a pilot plant at the Hanford Site to
demonstrate bulk vitrification of low-activity waste, a method that may be used
to supplement the Waste Treatment Plant. The Board understands the limited operational
life of this pilot plant and its potential benefits. However, the Board is also interested in
ensuring that this facility is built with appropriate features to prevent
escape of radioactive materials and to protect the workers.
The enclosed report presents
observations of the Board’s staff resulting from a review of the Demonstration
Bulk Vitrification Project and is provided for your information and use as appropriate.
The report notes potential weaknesses in
such areas as the confinement of materials and worker protection that need to
be considered in finalizing the design of the facility. The Board is aware of and is encouraged by the
fact that ORP and its contractor have already taken steps to evaluate some of
the issues raised in this report.
Therefore, pursuant to 42 U.S.C.
§ 2286b(d), the Board requests, at
a time consistent with the maturity of the design for the Demonstration Bulk
Vitrification Project, a briefing on the resolution of the issues identified in
the enclosed report. The Board expects
this briefing to occur no later than January 2006. In addition, the Board requests, within 60
days of receipt of this letter, a briefing on ORP’s technical and programmatic
oversight of this project.
Sincerely,
A. J. Eggenberger
Chairman
c: Mr. Mark B. Whitaker, Jr.
Mr.
Roy J. Schepens
Enclosure
DEFENSE
NUCLEAR FACILITIES SAFETY BOARD
Staff
Issue Report
August
9, 2005
MEMORANDUM FOR: J. K. Fortenberry, Technical Director
COPIES: Board Members
FROM: J. W. Troan
SUBJECT: Demonstration Bulk Vitrification
Project, Hanford Tank Farms
The purpose of this report is to
document reviews of the Demonstration Bulk Vitrification Project conducted by
the staff of the Defense Nuclear Facilities Safety Board (Board); these reviews
included site visits during May 24-26 and July 12-14,
2005. Members of the Board’s staff M.
Feldman, A. Matteucci, J. Shackelford, J. Troan, and R. Zavadoski participated
in the reviews. The staff met with
personnel from the Department of Energy (DOE) Office of River Protection (ORP),
CH2M Hill Hanford Group, Inc. (CHG), and the demonstration bulk vitrification
system subcontractor, AMEC, to discuss the design, preliminary safety analyses,
and controls for the project.
Background. The
project consists of a full-scale facility for research, development, and demonstration
of the bulk vitrification
process. The facility will be used to
vitrify waste from single-shell tank S-109 to demonstrate the
effectiveness of the process as means of supplementing the low-activity waste
capacity of the Waste Treatment Plant (WTP). Supplementing the WTP is considered necessary
to meet the milestones of the Tri-Party Agreement for completing retrieval of
waste from Hanford single-shell tanks by 2018 and treatment of tank waste by
2028.
The design and construction of
the demonstration bulk vitrification facility are expected to be completed by
early 2006. The first campaign using
radioactive waste is expected to start in mid-2006. In December 2004, the Washington State
Department of Ecology issued a permit to ORP and CHG to operate the
demonstration bulk vitrification
facility. The permit remains in effect
for a maximum of 400 “operating” days or 3 years, whichever comes first. Closure activities will follow operations, and
the facility is then expected to be decontaminated and decommissioned.
Several aspects of the facility
design, operation, and testing are not fully developed. Many elements of the
design are new and unproven and will require testing. Because of the status of the project, many
issues and questions identified by the Board’s staff remain unresolved, and
much work must be completed before operations begin. The following observations highlight some
issues noted by the staff.
Design. The
current design has a number of major vulnerabilities with respect to overall confinement
of radioactive and hazardous materials. Contrary to DOE’s design requirements to use
successive physical barriers for protection against the release of
radioactivity,[1]
the current design uses only one barrier to confine material in portions of the
plant. The project’s confinement
strategy also relies on a mix of active and passive safety-significant systems,
non-safety-related design features, and administrative controls.
Safety-significant confinement
boundaries include double-walled (hose-in-hose transfer line) piping,
double-walled tanks, and piping designed to the requirements of American
Society of Mechanical Engineers B31.3, Process Piping. Non-safety-related
design features include the In-Container VitrificationTM container,
which includes connections to the off-gas treatment system and dried waste
transfer system. Because these design
features are not classified as safety-significant, they may lack reliability
and availability commensurate with their safety functions.
The confinement strategy also
relies on the implementation of a specific administrative control to ensure the
closure of three non-safety-related cone valves (from the clean soil impingement
tanks). These three valves are
collocated with the safety-significant dryer outlet cone valves on top of the
vitrification container and form a portion of the overall confinement boundary.
As a result of these
vulnerabilities, the potential exists for the failure of a single non-safety-related
barrier that could lead to the unfiltered release of radioactive or toxic
materials and unacceptable consequences to workers. For example, failure of the integrity of the
non-safety related vitrification container could result in an unfiltered and
untreated release of radioactive and toxic material.
Guidance and requirements
establish that structures, systems, and components serving a safety-significant
confinement function be classified as safety-significant, that successive physical
barriers be used to protect against the release of radioactivity, and that the
number and arrangement of confinement barriers and their required
characteristics be determined on a case-by-case basis. This approach leads to a minimum of two
physical barriers for the protection against the release of radioactivity, with
at least one barrier designated as safety-significant. The Board’s staff observed that in some
portions of the demonstration bulk vitrification facility the confinement
barrier is not designated safety-significant and successive physical barriers
are not used. The justification for the
demonstration bulk vitrification facility’s confinement strategy is not
adequate. The staff needs additional
information to better understand the reason for not designating some physical
barriers as safety-significant and not using successive physical barriers. This justification ought to include more
complete hazard assessments, engineering evaluations, alternatives that were
considered, and compensatory measures.
Since the facility’s design
predates the Board’s Recommendation 2004-2, Active Confinement Systems,
the overall
confinement strategy does not incorporate considerations set forth therein
regarding an active confinement system. As
a result, the
proposed design does not align well with the expectations and guidance being
developed in the Implementation Plan for Recommendation 2004-2.
Safety
Analyses. The staff observed weaknesses in
the analysis of anticipated events and in source term assumptions. As noted earlier, since the design is not
complete, many issues and questions identified by the staff remain unresolved.
For example, an anticipated
system upset condition, such as the loss of power during vitrification, was
initially viewed by the contractor as an abnormal event that would result in a focused
decision at the time of occurrence as to whether to recover by restarting the
melt. The Board’s staff believes that,
given the expected nature of this occurrence, further analysis of the restarting
of the process and the hazardous conditions that could result is warranted. Confirming the behavior of the postulated
upset and the recovery procedures for this and other abnormal operating
scenarios may be appropriate as part of the project’s test program prior to the
introduction of radioactive material.
Experience has shown that
certain fission products from vitrified waste will volatalize,
migrate, and collect in various portions of the off-gas treatment system. The possibility of undesirable accumulation of
radioactive materials in this system has not been adequately considered in the
current design. As
a result, some of
the hazards associated with operations, upsets, and maintenance may not be
appropriately anticipated. As part of
the project’s test program, it may be advisable to evaluate actual performance
characteristics relative to the carryover and hold-up of fission products in
the off-gas treatment system.
Safety
of Facility Workers. The contractor’s approach to
identifying safety-significant controls to protect facility workers does not
appear to be consistent with the expectations contained in DOE directives. ORP and the contractor have drawn a
distinction between facility workers and collocated workers such that in
general, scenarios with significant consequences to collocated workers have
safety-significant controls, while scenarios with significant consequences only
to facility workers rely on safety management programs. In the Preliminary Documented Safety Analysis,
no safety-related structures, systems, and components are identified as
exclusively protecting the facility workers. However, several non-safety-related engineered
features are included in the demonstration bulk vitrification system design to
reduce the hazards to these workers (e.g., shield walls, enclosures, ammonia
sensor/alarm). While hazards to facility
workers are typically addressed through safety management programs, the Board’s
staff believes it would be advisable to consider the use of safety-significant
controls to address exposure of facility workers to significant radiological
and chemical hazards.
For example, ammonia is
identified in the Preliminary Documented Safety Analysis as a hazardous
material that is stored and used at the demonstration bulk vitrification
facility. Approximately 9,000 lb of
ammonia will be delivered and stored in a tank for use in the off-gas treatment
system. The Preliminary Document Safety
Analysis states that nonradiological hazards, such as chemical hazards, are
addressed by safety management programs (e.g., industrial safety and industrial
hygiene programs), and lists non-safety-related engineered features that
mitigate the ammonia hazard (e.g., vehicle barriers, sensor and alarm, and a standard
for building and testing the pressure vessel). The Board’s staff is concerned that ammonia
poses a significant hazard to workers, and that the ammonia hazard is not being
appropriately recognized and controlled. The staff believes it would be advisable to
protect workers from this hazard through safety-significant structures,
systems, and components and Technical Safety Requirements, such as Limiting
Conditions of Operation and Specific Administrative Controls.