TRANSMITTED TO M. WHITAKER 02/08/96

DEFENSE NUCLEAR FACILITIES SAFETY BOARD

                                             September 28, 1995

MEMORANDUM FOR:          G.W. Cunningham, Technical Director

COPIES:             Board Members

FROM:                    Lisa Stiles

SUBJECT:            Review of Spent Nuclear Fuel Activities at Idaho
                    National Engineering Laboratory


1.   Purpose:  This report documents a review of spent nuclear fuel (SNF)
     activities at the Idaho National Engineering Laboratory (INEL) conducted
     on September 12-14, 1995 by L. Stiles and K. Fortenberry.

2.   Summary:  The Defense Nuclear Facilities Safety Board's (Board's) staff
     notes that SNF activities at INEL are on or ahead of schedule for all
     major commitments.  Preparations for interim wet and dry storage are
     underway and plans for future transition to permanent or long-term storage
     are being developed.  A current problem in basin CPP-666 is the presence
     of microbially induced corrosion (MIC).  This problem could significantly
     impact wet storage of aluminum material in the basin. 

3.   Background:  In response to environmental questions raised by the State of
     Idaho concerning the shipment and storage of Fort St. Vrain SNF at the
     Idaho Chemical Processing Plant (ICPP), a court order was issued June 28,
     1993, which mandated that all spent fuel be removed from basin CPP-603 by
     December 31, 2000.  In addition, in response to Board's Recommendation 94-1, DOE has committed to (1) removing SNF from aging storage facilities
     with no future mission, (2) eliminating SNF facility safety
     vulnerabilities, and (3) placing INEL SNF in cost effective and regulatory
     compliant dry storage facilities until the SNF can be moved to the final
     national repository.  To accomplish these objectives, future interim
     storage of SNF at INEL will primarily consist of wet storage at CPP-666,
     and storage in dry, vented, canisters placed at the Irradiated Fuel
     Storage Facility (IFSF) or at other dry storage locations, such as CPP-749.  As the date (most likely the year 2036) for removing all SNF from
     INEL approaches, fuel will be transitioned to sealed "road ready" casks
     awaiting removal from the site to permanent or long-term disposition.

     Currently, INEL stores SNF of the following types: (1) zirconium-clad Navy
     and commercial fuel, (2) aluminum-clad fuel, (3) stainless steel-clad
     fuel, (4) irradiated and unirradiated graphite fuel, and (5) miscellaneous
     inactive nuclear materials (MINM).  These fuels are stored wet, dry, or in
     experimental casks.

4.   Discussion:

     To date, court order and Recommendation 94-1 milestones have been
     completed before or as scheduled.  The most recent milestone, to complete
     the second set of 189 fuel transfers from the North and Middle CPP-603
     basins, due by December 31, 1995, was completed September 11, 1995. 
     Transfer of the remaining 244 fuel canisters from the North and Middle
     basins has been initiated and completion is due by December 31, 1995.  The
     complete transfer of all fuels from the South basin is scheduled to begin
     in August 1996, and is to be completed by December 31, 2000.  

     Though less than optimal, water chemistry in basin CPP-603 is stable. 
     Values for conductivity hover around 560 ęS/cm, total activity
     concentration is about 3E-5 ęCi/mL, and pH levels fluctuate between 7.6
     and 8.0.   In contrast, water chemistry values at CPP-666 are comparable
     to those at commercial SNF storage pools.  Conductivity values are below
     2 ęS/cm, the composite activity concentration is 5.4E-7 ęCi/mL, and pH is
     between 5.0 and 6.0.

     Of greater concern in the CPP-666 basin is the occurrence of microbially
     influenced corrosion.  Microorganisms tend to form biofilms on surfaces
     that lead to the formation of separated cathodic and anodic areas.  These
     microorganisms break down a protective oxide layer which leaves areas
     anodic in relation to the remaining part of the element.  The nature of
     MIC and the resulting local water chemistry promote pit growth along grain
     boundaries and matrix defects.  Though the ultraviolet system at CPP-666
     appears to remove microorganisms from the water, it has been ineffective
     for decreasing microbial presence on fuel surfaces.

     As an example of problems experienced with MIC, a sealed aluminum dummy
     canister was inspected and basin water was found inside.  The outside
     surface pits were very small and were not visible with an underwater
     camera.  Even visual inspection at arms length revealed nothing more than
     minor corrosion pits.  However, a nondestructive examination technique
     developed at INEL using ultrasonic transducers revealed that substantial
     subsurface corrosion originating from MIC had caused the breach of the 1/8
     inch thick canister.  INEL personnel are working in conjunction with the
     University of Montana to address this problem.