**\[DNFSB LETTERHEAD\]**

November 3, 2004

The Honorable Linton Brooks

Administrator

National Nuclear Security Administration

U.S. Department of Energy

1000 Independence Avenue, SW

Washington, DC 20585-0701

Dear Ambassador Brooks:

The staff of the Defense Nuclear Facilities Safety Board (Board)
recently reviewed a number of issues at the Pantex Plant related to
electrical and lightning protection systems. Many of these issues were
raised initially in an August 6, 2002, letter from the Board.

The Board is pleased to note the progress made in addressing many of the
issues raised in that letter. In particular, the Pantex Plant
contractor, BWXT Pantex, has completed activities to protect
safety-class electrical equipment from spurious sprinkler activation and
repair leaking roofs in electrical equipment areas. The Board is also
pleased to note that progress has been made in publishing initial
reports on low-voltage testing of nuclear explosive facilities. However,
not all of these are as yet final, and efforts to repeat the results of
these initial tests have not been successful. In addition, a number of
significant issues related to lightning protection identified in BWXT
project plans remain unresolved. The Board encourages the National
Nuclear Security Administration (NNSA) and its contractors to finalize
the outstanding items from these project plans expeditiously.

The Board is also encouraged that NNSA has decided to take the
opportunity to address known deficiencies in the electrical distribution
systems for Buildings 12-44 and 12-64 as part of the ongoing projects to
upgrade these facilities. It would appear reasonable to address these
known inadequacies in the surge suppression system while completing
other significant upgrade work related to the electrical distribution
systems for these facilities.

The enclosed report prepared by the Board's staff contains a number of
observations concerning electrical and lightning protection systems at
the Pantex Plant. This report is provided for your information and use
as appropriate.

Sincerely,

***John T. Conway***

***Chairman***

c: The Honorable Everett Beckner

Mr. Daniel E. Glenn

Mr. Mark B. Whitaker, Jr.

Enclosure

**DEFENSE NUCLEAR FACILITIES SAFETY BOARD**

**Staff Issue Report**

October 22, 2004

**MEMORANDUM FOR:** J. K. Fortenberry, Technical Director

**COPIES:** Board Members

**FROM:** W. White

**SUBJECT:** Electrical and Lightning Protection Systems at the Pantex
Plant

This report documents a review performed by the staff of the Defense
Nuclear Facilities Safety Board (Board) of electrical and lightning
protection systems at the Pantex Plant. Staff members A. Gwal and W.
White, with outside expert R. Collier, participated in this review
during August 24-26, 2004. The report also documents follow-up
discussions with the National Nuclear Security Administration's (NNSA's)
Pantex Site Office (PXSO) in October 2004.

**Lightning Protection Systems.** In September 1997, the Board issued a
reporting requirement to the Department of Energy (DOE) regarding the
controls necessary to address the hazard posed by lightning to nuclear
explosive operations. Following DOE's initial response to this reporting
requirement, the Board reviewed this issue periodically at the Pantex
Plant to monitor progress in addressing open and emerging issues related
to lightning protection.

*Low-Voltage Testing*---In a letter dated August 6, 2002, the Board
encouraged NNSA and its contractors to complete documentation of the
low-voltage testing done to validate analytical models of the maximum
facility voltages possible as a result of a lightning strike. The
documentation of the initial testing has now been completed, although
some of the reports have not been finalized. In addition, BWXT has
worked to develop an internal capability to perform the required
periodic low-voltage testing of facilities, reducing its reliance on the
limited resources available through Sandia National Laboratories.

The periodic surveillance testing conducted thus far by BWXT has been
problematic, however. The Technical Safety Requirements (TSRs) for
Pantex facilities mandate that low-voltage testing be conducted on each
facility type every 5 years to validate the facilities' Faraday cage
characteristics. For Building 12-44, the initial testing, accomplished
by Sandia in 1998, indicated certain facility characteristics that
allowed the maximum potential voltage threat to be lowered from 141 kV
to 25 kV. This testing should have been repeated in 2003. For a number
of reasons, however, BWXT was unable to perform the testing until May
2004, taking advantage of a 25 percent grace period allowed in the TSRs.

BWXT was unable to correlate the results of its retest of Building 12-44
with the original test results documented by Sandia: the electric fields
measured by BWXT were significantly lower than those measured by Sandia.
Since it is unlikely that the Faraday cage characteristics of the
facility have improved significantly with age, BWXT considered the test
results invalid. A Justification for Continued Operation (JCO) was
written, which raised the facility voltage back to 141 kV. The BWXT JCO
points to a number of differences between the BWXT and Sandia
tests-including different equipment used, lower excitation levels,
different drive points, and new facility weatherproofing-that may have
contributed to the different results obtained.

In discussions with the Board's staff, PXSO and BWXT agreed that the
low-voltage testing done for facilities needs to be repeatable and must
be able to indicate significant changes in those facility
characteristics credited for lightning protection in the safety basis.
PXSO and BWXT were considering options that included creating a
permanent test attachment point for each facility once such a point can
be identified that provides credible information on the structure's
response to a lightning strike. Care would need to be taken, however, to
prevent such a test attachment point from becoming a preferential
attachment point for real lightning strikes.

*Facilities without Adequate Surge Suppression*---In December 2003, a B
WXT engineer questioned whether, in the event of a lightning strike to
nuclear explosive facilities, alternative pathways exist that could
bypass the surge suppression credited in the safety basis for mitigating
the impact of a lightning strike. These alternative pathways include
telephone circuits, exposed electrical outlets, heat trace elements, and
other circuits that have the potential to provide a pathway to the
electrical distribution system on the facility side of the existing
surge suppression. In late February, BWXT determined that these circuits
exist and could circumvent the surge suppression as designed.

Following this determination, a JCO was approved to address the issue.
The JCO established several compensatory measures, including raising the
maximum facility voltage considered possible in a lightning strike to 60
kV where the bonded voltage was less than 60 kV. The basis for this
voltage limit was an analysis by BWXT concluding that voltages higher
than 60 kV would cause arcing between conductors in electrical circuits,
effectively limiting the maximum potential voltage.

A nuclear explosive safety review team suggested additional work to
verify the dominant mechanism for voltage breakdown in these alternative
pathways. During the staffs review, the Board's outside expert suggested
that BWXT consider the potential time lag of any arc formation in the
testing being planned to verify the dominant voltage breakdown
mechanisms. It is possible that the voltage rise from a lightning strike
could occur more quickly than the credited insulation breakdown and arc
formation. Should this be the case, it is possible that the maximum
voltage could be much higher than 60 kV. BWXT agreed to evaluate this
scenario during the planned testing activity.

*Lightning Detection and Warning System*---In May 2004, one of the four
lightning sensors (located in Pampa, Texas) for the lightning detection
and warning system (LDWS) at the Pantex Plant began to experience
frequent failures. These failures were identified by the Pantex
Operations Center, and personnel appropriately entered a limiting
condition of operation (LCO) in the Technical Safety Requirements for
Pantex Facilities (LCO 3.5.1). This LCO allows up to 14 days to return a
failed sensor to operable status.

The sensor would typically recover from such failures within hours, but
would fail again

within a day. These spontaneous recoveries allowed BWXT to exit the LCO
without addressing the cause of the failures-the telephone
communications circuit between the sensor and the Pantex Operations
Center.

BWXT has communicated with the vendor for telephone service to obtain a
commitment to pursue the repair of the circuit diligently. BWXT is also
working to obtain alternative sources of data from sensors that are part
of the National Lightning Detection Network. BWXT hopes to integrate the
data from four new sensors into the LDWS software without having to
purchase or maintain the sensor hardware. This appears to be a
reasonable, cost-effective approach to increasing the reliability of the
LDWS.

*Lightning Protection Project Plans*---Open issues and areas for
improvement are tracked at the Pantex Plant through the *Lightning
Protection Authorization Basis Project Plan*. This plan contains key
actions that remain open. Among these are an investigation into the
potential for spalling of interior concrete surfaces as a result of a
lightning strike and an evaluation of the impact of added inductance
from facility bond wires. These issues were originally raised during a
nuclear explosive safety study conducted in August 2000. The latest
schedule for resolution of these issues is late 2004 or early 2005. The
need to resolve these issues was noted in the report attached to the
Board's letter of August 6, 2002, but progress toward addressing them
has been limited.

The report forwarded by the Board also noted the need to address the
potential for indirect coupling mechanisms from a lightning strike to
impact nuclear explosive operations. Following receipt of the Board's
letter, NNSA and its contractors developed a project plan,
*Investigation of Lightning Initiated Indirect Effects at Pantex*. The
progress made to date, however, has been limited. Sandia recently
completed an analysis of the worst-case threats that could be posed by
such mechanisms. This analysis indicated that the potential threat is
marginal for main charge detonators, but may be problematic for other
explosive initiators that pose hazards to worker safety. BWXT has
transmitted this analysis to the design laboratories for weapon
response.

**Electrical Systems.** The Board's staff reviewed several issues
related to electrical distribution systems at the Pantex Plant. These
issues related to a range of topics, from proposed facility upgrades to
existing electrical distribution equipment.

*Upgrade Projects for Buildings 12-44 and 12-64*---The staff reviewed
proposed modifications to the electrical systems for Buildings 12-44 and
12-64. At the time of the staff review in August 2004, the modifications
to the electrical systems for these facilities did not address the known
deficiencies discussed above in the surge suppression of electrical
systems. However, on October 7, 2004, NNSA directed BWXT to resolve the
surge suppression issues for those facilities as part of the ongoing
upgrade projects.

The staff also suggested that BWXT consider instituting a cable
monitoring program as part of the upgrades for Buildings 12-44 and
12-64. Many of the electrical cables used in these buildings are
approaching or past their intended service life. Replacement of aged and
deteriorated cables should be considered at the time of a design
modification of the distribution system. As cables age, their electrical
characteristics may degrade to an unacceptable level, decreasing the
reliability of both the cables and the systems they support. Because
these cables supply power to a number of important facility systems
(including radiation monitoring equipment and emergency lights), it may
be prudent to establish a baseline for the remaining life of the cables
and to incorporate a capability to monitor the condition of cables into
the existing preventive maintenance regime.

*Electrical Equipment Rooms*---The staff walked down several facilities
and equipment areas and noted significant progress in addressing
electrical system issues raised by the Board in its letter of August 6,
2002. Vulnerable electrical equipment has been provided with raised
covers to protect against fire suppression systems, nonrated electrical
equipment has been screened and reviewed, and leaking roofs over
equipment areas have been repaired.

During a walkdown of the electrical room in Building 12-99, however, the
Board's staff observed an air-conditioning unit above the batteries
supplying a safety-related uninterruptible power supply (UPS). The
condensate water from the air-conditioning unit could leak on the
batteries and disable the UPS. Additionally, PXSO senior staff expressed
concern regarding the provision for load testing of a UPS in Building
12-116. Institute of Electrical and Electronics Engineers (IEEE)
Standard 446- 1995, *Recommended Practice for Emergency and Standby
Power Systems for Industrial and Commercial Applications*, requires that
a complete operational test of the UPS, including operation at full
load, be performed biannually. BWXT has agreed to evaluate this issue.

**Electrical Safety.** The staff discussed the new draft version of the
DOE Handbook on Electrical Safety with BWXT personnel. The electrical
safety committee at the Pantex Plant appeared to have become less than
fully functional since the staffs last review, apparently as a result of
the reassignment of personnel on the committee. During the August 2004
discussions, BWXT identified two personnel responsible for
reconstituting the committee and committed to recommence monthly
meetings. One of the committee's functions will be to monitor electrical
safety occurrences. There have been several significant occurrences
recently, particularly for subcontractor work.

**Loss of Power.** In May 2004, the Pantex Plant suffered a significant
power outage that impacted most plant operations. The outage resulted
from activation of a protective relay at the south substation that
occurred when the north substation was offline. All safety-class and
safety-significant systems appeared to function as designed. However, a
number of problems did occur during the outage that provided BWXT with
valuable information on areas for improvement. These problems included a
lack of paper procedures should electronic ones become unavailable, the
loss of backup power to emergency lighting, and the absence of
formalized recovery procedures.

On a positive note, BWXT had initiated an effort well before the
loss-of-power incident to develop and implement a procedure for such
events. Draft checklists resulting from this effort were available to B
WXT facility personnel during this occurrence. BWXT representatives
discussed this continuing effort with the Board's staff during the
review. The staff encouraged BWXT to finalize the procedures and
checklists and to provide as much specific detail as possible.