[DNFSB LETTERHEAD]
June 22, 2005
Mr. Thomas P. D’Agostino
Acting Deputy Administrator for
Defense Programs
National Nuclear Security
Administration
U.S. Department of Energy
1000 Independence Avenue, SW
Washington, DC 20585-0104
Dear Mr. D’Agostino:
The staff of the Defense Nuclear
Facilities Safety Board (Board) conducted a review of electrical systems at the
Y-12 National Security Complex. Observations made in the enclosed report are
based on document reviews and discussions with representatives of the National Nuclear
Security Administration Y-12 Site Office and BWXT Y-12.
As noted in the enclosed report,
a small electrical fire occurred in Building 9212 in November 2003. Although the corrective actions identified as
a result of this event (e.g., thermal imaging and panel evaluations) were
appropriate to identify other susceptible panels requiring additional
inspections, it appears that the inspections have been delayed by other
priorities. The Board believes it would
be prudent to complete these inspections and corrective actions, as appropriate,
in a timely manner to ensure these aging electrical panels do not represent an
undue fire hazard for Y-12 defense nuclear facilities. The enclosed report also describes concerns related
to other electrical issues.
The enclosed report is forwarded
for your information and use as appropriate.
Sincerely,
A.
J. Eggenberger
Acting Chairman
c: Mr. Mark B. Whitaker, Jr.
Mr.
William J. Brumley
Enclosure
DEFENSE
NUCLEAR FACILITIES SAFETY BOARD
Staff
Issue Report
June
9, 2005
MEMORANDUM FOR: J. K. Fortenberry, Technical Director
FROM: A. K. Gwal
SUBJECT: Electrical Systems at the Y-12
National Security Complex
This report documents a review
by the staff of the Defense Nuclear Facilities Safety Board (Board) of the
electrical systems at the Y-12 National Security Complex. Staff members A. Gwal, T. Davis, and D. Owen
met with representatives of the National Nuclear Security Administration (NNSA)
Y-12 Site Office (YSO) and its contractor, BWXT Y-12, on April 27-28, 2005. The staff reviewed the following: 1) inspection results and inspection activities
for electrical panels, 2) high-voltage cable splice installations in manholes,
3) scope of the electrical upgrade project, and 4) open electrical issues at the proposed Highly Enriched Uranium
Materials Facility (HEUMF).
Y-12 Electrical Panels. On November 13, 2003, an electrical fire occurred in a panel
in Building 9212 due to overheating. Numerous electrical issues were identified
including multiple loads connected to a circuit and loose fuses and connectors.
In response to the event, BWXT initiated
a corrective action plan that included thermal imaging and evaluation of all
Y-12 electrical panels. The initial
thermal evaluation was complete in October 2004. Based on this evaluation, BWXT identified 133
panels in major nuclear facilities that required further intrusive inspections.
Even though these inspections were
planned to be completed by September 2005, BWXT has only recently done planning
for the work and has not completed any of the inspections. As part of its recovery plan, BWXT indicated
that 28 panels will be inspected in the next three months and a schedule for
inspecting the remaining panels will be established.
Because of the age of these
panels and facilities, the staff believes it would be prudent to complete these
additional inspections in a timely manner. BWXT personnel also noted that they were
considering additional thermal evaluations to identify degrading panel
conditions. The staff believes that such
an on-going process for evaluating panels at Y-12 facilities would be appropriate.
High-Voltage Cable Splices
in Manholes. In the late-l990s, there were
four significant 13,800-volt cable faults resulting in explosions in the Area 5
distribution system at cable splice locations in manholes. The last failure occurred in May 1998. Investigation revealed that the failure of
splices was due to the degradation of the splice mechanical structure and
introduction of moisture to the splice insulation system. Because of improper installation, such as
improper alignment and bolt torquing, and inadequate cable/splice support,
moisture entered the splice insulation system. Another factor in the splice failure was the
copper cable rigidity that exerted mechanical forces on the splice structure. All of the Area 5 cable splices were
identified and replaced with another type of splice (Raychem Heat Shrinkable)
in April 1999, and no failures have occurred since.
During a walkdown of these splices
in several manholes, the staff noted that a number of the cables and the
splices were underwater. These cables
supply power to defense nuclear facilities in the area (e.g., Buildings 9212
and 9215). After reviewing the type of
jacket and insulation material for the cables, the staff questioned their
long-term ability to function underwater. Typically, cables will lose dielectric
strength underwater which can allow short circuits to occur, potentially
resulting in an explosion. In response
to these observations, BWXT personnel noted they are planning to survey
manholes for water, to pump manholes as necessary to keep cables dry, to add
supports to keep the looped cables above the water, and investigate other means
to keep cables and splices dry.
Y-12 Electrical
Distribution System Upgrade Project. The Electrical Distribution System
Upgrade project corrects deficiencies in the 161-kV/13.8-kV
power system serving Y-12 to enhance the system’s reliability, operability, and
maintainability. This project will
replace the existing main transformer with another transformer having twice the
rating, switchgear, and other equipment, such as batteries. Additionally, the project will reconfigure
161-kV distribution lines as well as reconfigure and rehabilitate the ELZA 2
switch yard. Currently, this project has
been deferred as a result of recent budget cuts and re-prioritization. The staff observed that replacing a
transformer with a higher rated transformer will result in higher short circuit
current. The staff considers it
appropriate for BWXT to evaluate the design modification to confirm that the
interrupting capability of all the electric equipment will withstand the higher
short circuit current.
Highly Enriched Uranium
Materials Facility. On March 1, 2004, the Board issued a letter to NNSA containing the
observations of the staff. The following
is a summary of the electrical issues yet to be fully resolved concerning the
design of the electrical system for HEUMF.
Emergency
Lighting―The
staff had observed that emergency lighting is not seismically qualified and a
design basis earthquake could cause total blackout in the building. BWXT has now proposed the installation of 47
seismically supported supplementary emergency lightning units along major exit
paths to reduce the risk of a total blackout. The design for this upgrade is in progress.
Raceway
Penetration Seals―The
staff had requested information regarding the ampacity-derating effect
(reduction in the rated current of the cable) of the penetration seals containing
safety-significant circuits in accordance with IEEE STD-848, IEEE Standard Procedure for the
Determination of the Ampacity Derating of
Fire-Protected Cables.
B WXT has issued a report concluding
that there are no safety-significant current-carrying circuits that penetrate
the confinement boundary. However, the
staff considers it appropriate to evaluate all the penetration seals and the
contained cables for the determination of ampacity derating to confirm the
safety of the installation related to fire or overheating of the cables.
Rating
of the Safety-Significant Diesel Generator―The staff had observed that the current
rating of the diesel generator may not be adequate to handle the starting
transients of the connected safety-significant motors. BWXT plans to perform additional verification
of generator capabilities after vendor data becomes available. Additionally, acceptance tests will be
performed by the vendor prior to shipment to the construction site.
Electrical
Calculations―BWXT
has now evaluated the electrical calculations and found two issues related to
equipment rating. Discrepancies exist
between the parameters calculated by the SKM Systems Analysis Software and the
equipment ratings applied in the design package. BWXT plans to revise the design to correct the
discrepancies.