DEFENSE NUCLEAR FACILITIES SAFETY BOARD

                              
                                             February 8, l994
               
MEMORANDUM FOR:          Technical Director

COPIES:                  Board Members

FROM:                    Richard E. Tontodonato

SUBJECT:                 Trip to Review Feed Characterization for
                         Rocky Flats Plant Building 707 Thermal
                         Stabilization Process, January 20, 1994

1.   Purpose:  This memorandum is a report by the DNFSB staff
     (Richard Tontodonato and Davis Hurt) on a visit to the Rocky
     Flats Plant on January 20, 1994 to review the
     characterization of feed materials for the Building 707
     thermal stabilization process.

2.   Summary:  EG&G has completed characterization of the
     brushings and other ordinary plutonium oxide materials
     currently identified as feed for thermal stabilization, and
     has characterized some of the duct residues planned to be
     stabilized.  Results from testing oxides indicate, as
     expected, that these materials will be safe to process in
     the Building 707 calciners.  Plutonium-bearing duct
     residues, however, undergo large weight losses when heated
     and may not be adequately stabilized if only heated to
     500C.  Reduced batch sizes, slower heat-up rates, and a
     higher stabilization temperature may be required to safely
     stabilize them.  The Stabilization Technical Review Group, a
     group of EG&G plutonium experts assigned to evaluate the
     characterization results, has not yet decided what testing
     or analysis is needed to determine how to process the duct
     residues.

3.   Background:  The Department of Energy plans to restart two
     calcining furnaces in Building 707 for the purpose of
     converting potentially unstable plutonium materials to
     stable plutonium dioxide, PuO2.  DOE-Rocky Flats Office
     (DOE-RFO) and EG&G-Rocky Flats (EG&G) personnel did not
     originally plan to perform any chemical analysis or other
     objective characterization of the feed materials.  However,
     the Board believed it would be risky to process some of the
     materials, particularly the oily duct residues, without
     understanding more about their compositions.  After
     significant discussion, DOE-Office of Defense Programs (DOE-
     DP) management agreed that feed characterization was
     warranted.  Subsequently, at the Board's February 1993
     public meeting in Boulder, Colorado, DOE representatives
     stated that they had developed a plan to sample each can of
     duct residue and perform selected chemical analyses to
     ensure these materials could be safely stabilized.  In March
     1993, the DNFSB staff reviewed the characterization program
     and concluded that it adequately addressed potential
     calcination safety issues. (documented in a trip report
     forwarded by the Board to DOE-DP on March 19, 1993)

4.   Discussion:  EG&G has completed characterization of the
     brushings and other ordinary plutonium oxide materials
     currently identified as feed for thermal stabilization, and
     has characterized some of the duct residues planned to be
     stabilized.  Twelve containers of duct residues have been
     sampled and analyzed, and another 16 containers are
     scheduled to be sampled once thermal stabilization begins. 
     EG&G does not plan to sample the remaining 59 containers of
     duct residues in FY 1994 because they are not scheduled to
     be stabilized in FY 1994.  Test methods and results to date
     are described below:

     a.   Test Methods:  EG&G uses thermogravimetric analysis
          (TGA) and infrared spectroscopy (IR) to characterize
          two samples from each can of feed material.  In TGA, a
          15-30 milligram sample is heated in air to about 900C,
          and weight changes are monitored as a function of
          temperature.  Weight losses can be caused by
          evaporation of absorbed water or other volatile
          materials or by chemical reactions evolving gaseous
          products.  Weight gains are typically due to oxidation
          of plutonium metal.  This test can be used to estimate
          how much plutonium metal is in a sample, and whether
          significant chemical reactions occur when it is heated.

          In IR, a two milligram sample is mixed with 300
          milligrams of an infrared-inert material, formed into a
          one millimeter thick pellet, and illuminated with an
          infrared source.  Absorption is measured as a function
          of infrared wavelength.  Organic species and some
          inorganic materials can often be identified using this
          process.

     b.   Test Results:

          (1)  Oxides:  Oxide materials showed a small (1-2% )
               change in weight in TGA, and contained essentially
               no IR-active constituents.  These materials should
               be safe to calcine.  EG&G is also using the TGA
               results to estimate the plutonium metal fines
               content of the samples.  EG&G is considering
               removing containers with sufficiently low
               plutonium metal fines content from heat detectors,
               to make room for storing uncharacterized scrapings
               that will be generated in the upcoming plutonium
               metal repackaging effort.

          (2)  Duct residues:  Duct residues experienced up to 80
               percent weight loss in TGA, indicating they are
               vastly different from the oxide materials.  Most
               of the weight loss occurs below 500C, but some
               samples showed noticeable weight losses up to
               about 800C.  EG&G plutonium experts consider it
               likely that the weight loss is due to organic
               material in the residues burning in the test, but
               suspect that inorganic coatings used in molds may
               also be involved.  IR revealed little about the
               nature of the duct residues, the only conclusion
               being that some of the samples may contain
               hydrocarbon oils.

                    Discussions with members of the Stabilization
                    Technical Review Group revealed that they
                    have not yet decided what additional testing,
                    if any, will be done to define how to safely
                    stabilize the duct residues.  Their opinion
                    was that the duct materials could probably be
                    safely stabilized either by limiting the
                    batch size or by heating to a relatively low
                    temperature (perhaps 200C), holding there to
                    allow gases to evolve at a manageable rate,
                    then heating up to the stabilization
                    temperature, possibly above 500C. 
                    Additional TGA testing, using reduced heating
                    rates and hold times at different
                    temperatures, will be needed to define this
                    modified process.  The members of the
                    Stabilization Technical Review Group did not
                    envision performing other laboratory analyses
                    to more precisely determine the constituents
                    of the residues.  From a safety perspective,
                    this is acceptable, but it does not address
                    the potential for RCRA-regulated constituents
                    in the residues.

5.   Conclusions:

     a.   As expected, characterization of plutonium oxide feed
          materials indicates that they can be safely stabilized
          in the Building 707 calciners.

     b.   Characterization results for the plutonium-bearing duct
          residues indicate that procedural or process changes
          will be needed before they can be safely stabilized in
          the Building 707 calciners.  Continued DNFSB staff
          attention is warranted to ensure DOE-RFO and EG&G
          adequately resolve this problem.