[DNFSB
LETTERHEAD]
August 24, 2004
Mr. Paul M. Golan
Acting Assistant Secretary for
Environmental Management
U.S. Department of Energy
1000 Independence Avenue, SW
Washington, DC 20585-0113
Dear Mr. Golan:
The Defense Nuclear Facilities
Safety Board (Board) has received your letter of August 3, 2004, forwarding a
report entitled Office
of River Protection, Waste Treatment Plant (WTP) Low Activity Waste (LAW)—Facility-Independent
Structural Design Peer Review. This report was one of three
requested by the Board during a May 22-23, 2002, review, as reiterated in its
letter of November 14, 2002.
The Board has completed its
initial review of the report and concluded that it satisfies the requirements
of the original request. The Board is
pleased with the effort of the Office of River Protection Peer Review Team, a
team of structural experts empaneled by the project
to review the structural design of the WTP buildings. The Board believes the team’s involvement and rigorous
review have resulted in significant design improvements to the LAW building. Given that this summary structural report is
envisioned as providing a historical basis for design, the Board believes it
should be updated to reflect resolution of the Peer Review Team’s comments after
they have reviewed the completed building design.
Since the Board made its
original request for these summary structural reports, significant effort has
been expended on reviewing and resolving issues regarding the design adequacy
of the High-Level Waste Facility structure. The layout of the building is highly complex,
which makes the design challenging and underscores the need for the summary structural
report for this facility to describe the structure’s behavior to validate
overall design adequacy. Several
significant issues remain to be resolved to facilitate completion of the report
and confirm that the building is adequately designed. These issues are described in the enclosure to
this letter. The Board believes these
issues are sufficiently significant that they could result in the need to
modify the building design. Given the
close-coupled design and construction process being employed by the project and
the fact that the building basemat and most of the
walls to grade have already been constructed, these issues need to be resolved
as expeditiously as practicable.
Sincerely,
John T. Conway
Chairman
c: Mr. Mark B. Whitaker, Jr.
Mr.
Roy J. Schepens
Enclosure
ENCLOSURE
Waste
Treatment Plant High-Level Waste Facility:
Issues
Unresolved in Summary Structural Report
·
Effect
of Finite Element Mesh Size on Wall and Slab Design. Force
and moment analysis results are used directly by the project to select
reinforcing steel areas. Given the
complexity of the building wall and slab arrangement, the finite element
spacing used in analyzing the building may not be sufficiently refined to
produce analysis results representative of actual behavior. The result could be failure to provide
sufficient reinforcing steel to safely resist the applied loads.
·
Redistribution
of Loads Associated with Concrete Cracking. Given
the unique arrangement of walls used to resist east-west seismic load, the
stiffness reduction and resulting load redistribution associated with concrete
cracking may be significant. The project
needs to determine whether this phenomenon is significant enough to warrant inclusion
in the building analysis.
·
Determination
of the Potential Impact of Ground Motion Attenuation. This
issue is outlined in the Defense Nuclear Facilities Safety Board’s letter of
July 29, 2004.
·
Description
of East-West Load Distribution Mechanisms. Based
on analysis results, a significant percentage of the inertial load in the
east-west direction is resisted by building elements that are somewhat removed
from the origin of the load. Load
transfer occurs through the connecting floor slabs. An explanation, on the basis of relative
stiffness of the affected building elements, needs to be provided to confirm
the computational results.