[DOE LETTERHEAD]
December 11, 2002
The Honorable John T. Conway
Chairman
Defense Nuclear Facilities Safety Board
625 Indiana Avenue, NW, Suite 700
Washington, DC. 20004
Reference:
HQ letter from C. L. Huntoon to J.
T. Conway, DNFSB, Regarding Tank Integrity, dated November 30, 2000.
Dear Mr. Chairman:
The purpose of this letter is to provide the
status of the Department of Energy (DOE) commitments on Hanford Tank Integrity
as documented in the subject letter.
The Hanford Tank Farms now have programs in place to verify and maintain
Double-Shell Tank (DST) integrity. Tank
waste chemistry limits for corrosion mitigation are part of the safety basis
and tank waste chemistry is proactively evaluated to facilitate timely chemical
adjustments prior to exceeding these specifications.
The original actions selected to assure
issue resolution have been completed with the exception of Action 3.l to
“Adjust chemistry within specification for four DSTs.” Sodium hydroxide solution has been added to
three DSTs to bring them into
specification. Their status is as
follows:
| 241-AY-101 | Supernate specification/Sludge in specification | |
| 241-AY-102 | Supernate in specification/Sludge in specification | |
| 241-AN-102 | Supernate in specification/Sludge is expected to come into specification through natural mixing |
In addition, 42,000 gallons of sodium
hydroxide solution were added to Tank 241-AN-107 in February 2002 and the tank
supernate has been confirmed to be within chemistry specifications. However, Tank 241-AN-107 sludge is not
expected to reach the required specifications as a result of this addition, and
recent laboratory evaluations have concluded that additional data will be
required prior to further chemical addition.
Detailed caustic demand laboratory testing
was recently performed for Tank 241-AN-107 waste. Results of these tests showed a tendency for solids precipitation
with the addition of sodium hydroxide.
Based on these laboratory results, further addition of caustic to
achieve chemistry specifications in the bulk waste would exceed the Technical
Safety Requirements (TSR) Recovery Plan precipitation criterion, which could
create the potential for gas release events in the tank.
Core sampling has been completed and
laboratory analysis of Tank 241-AN-107 waste is currently underway to provide
additional information. Laboratory
results are expected by the end of this month.
The results will be used to develop an updated plan to bring tank waste
chemistry into specification. A careful
evaluation and sound technical basis for further actions are required due to
the waste characteristics and susceptibility for solids precipitation. The TSR Recovery Plan will be revised to
reflect the new technical approach in January 2003.
The DOE remains committed to maintaining the
integrity of the Hanford DSTs. DOE
believes that actions completed to date, and management of the few remaining
activities under the authorization basis Administration Control 5.15 Chemistry
Control Program, satisfy Issue 3 to “Implement or revise tank chemistry
controls.” Therefore, DOE recommends
that Issue 3 be closed and that only Action 3.1 remains open as a formal means
for communicating status to the DNFSB.
The ORP will keep your staff apprised of our ongoing progress.
Sincerely,
Jessie Hill Roberson
Assistant Secretary
for Environmental Management