DEFENSE NUCLEAR FACILITIES SAFETY BOARD

                                                                                            September 30, 1994

MEMORANDUM FOR:             G. W. Cunningham, Technical Director

COPIES:                     Board Members

FROM:                       David C.  Lowe

SUBJECT:                    Savannah River Site (SRS) - FB-Line Safety Envelope Review
                            Trip Report (September 19-21, 1994)

1.    Purpose:  This trip report documents the Defense Nuclear Facilities Safety
      Board (DNFSB) technical staff (D. Lowe, J. Roarty, A. De La Paz, and D.
      Moyle) September 19-21, 1994, review of the FB-Line safety envelope.

2.    Summary:  The FB-Line Basis for Interim Operation (BIO) identified a
      propagated fire as the highest risk accident.  In the discussions with
      Westinghouse Savannah River Company (WSRC), it was concluded that a
      reasonable uncertainty band attached to the results of the accident analysis
      (but no uncertainty analysis was conducted) would include a region extending
      above the WSRC risk acceptance curve.  The major contributor to the
      consequences is that the 3rd and 4th level room exhaust does not go to the
      sand filter so an unmitigated release can result.  The DNFSB staff believes
      that the high risk associated with this accident suggests that additional
      preventive and mitigative actions might be considered.  

3.    Background:  The FB-Line receives plutonium nitrate solutions from F-Canyon
      for processing into plutonium metal buttons.  FB-Line also recovers
      plutonium residues and transfers them to F-Canyon for further processing. 
      FB-Line is scheduled to restart in March 1995.  This review was based on
      discussions with Department of Energy - Savannah River Operations Office
      (DOE-SR) and WSRC personnel.

4.    Discussion:

      a.    Authorization Basis:  The BIO has been submitted to DOE-SR for approval. 
            The BIO includes additional accident analyses and updates the
            authorization basis documents.  WSRC is developing a FB-Line safety
            envelope management database that will link the authorization basis to
            operating procedures, surveillances, and calibrations.  This database is
            based on the F-Canyon database and will incorporate similar verification
            and validation procedures.  This is a very important tool for managing
            the safety envelope for a facility, and the DNFSB staff suggests that it
            would be advisable for WSRC to develop a site-wide safety envelope
            management procedure that incorporates the lessons-learned from F-Canyon
            and other appropriate facilities.

      b.    Propagated Fire: The FB-Line BIO identified a propagated fire as the
            highest risk accident.  A reasonable estimate of the uncertainty
            inherent in the accident analysis (but no uncertainty analysis was
            conducted) would lead to error bands whose upper bounds would lie above
            the WSRC risk acceptance curve.  The major contributor to the
            consequences is the possibility of fire, inasmuch as the atmospheric
            exhaust from the 3rd and 4th level rooms does not go to the sand filter,
            and so an unmitigated release could result.  The 3rd and 4th level room
            exhaust normally goes through two high efficiency particulate airborne
            (HEPA) filter banks prior to release, but the HEPA filters are assumed
            to be consumed in a propagated fire.  A major assumption in the accident
            analysis is that the fire will not propagate to the storage vaults.

            The high risk associated with this accident suggests that additional
            preventive and mitigative actions may be appropriate.  WSRC stated that
            there is a planned modification to redirect the 3rd and 4th level room
            exhaust to the sand filter with a planned completion date of December
            1995.  The DNFSB staff believes that acceleration of this project should
            be seriously considered if such is possible without severely delaying
            the intended use of FB-Line.  Additionally, a reduction in the amount of
            material allowed in the 3rd and 4th levels would reduce the accident
            consequences.  WSRC stated that there is a storage location (i.e.,
            outside and above the vault) that was included in the source term
            calculations, but there is no need to use this storage location.  WSRC
            indicated that it would be a minor administrative change to the
            Technical Standards to eliminate this potential source term.  The DNFSB
            staff believes that these and/or other appropriate actions should be
            considered in order to reduce the risk from a propagated fire.

      c.    Ion Exchange Column Uncontrolled Reactions:  The BIO identifies the
            potential for ion exchange highly energetic uncontrolled reactions and
            identifies measures to prevent these accidents.  One preventive measure
            identified in the BIO, but not identified as a safety-related component,
            is the column vent.  Additionally, WSRC stated that they were not aware
            of the technical basis for the vent size, but they would follow up on
            this issue.

      d.    Hydrogen Deflagration:  The potential for hydrogen production by
            radiolysis and buildup in process vessels has been identified, but it
            was not considered in the Safety Analysis Report.  Thus, an unreviewed
            safety question evaluation (USQE) is underway for this event.  The
            potential exists for buildup to flammable concentrations within a few
            days since these vessels are not continuously ventilated.  WSRC is
            proposing the manual purging of 21 process vessels by opening a fill
            line which will purge any flammable gases via the vessel vent system. 
            This will require manually purging each of the 21 process vessels
            approximately every 8 hours for several minutes.  The operating
            procedures are being developed, and the vessel vent purge system has
            been designated a safety-related system.  A functional test of the
            purging procedure and a determination of adequacy will be conducted
            prior to startup.  The major hazard from a hydrogen deflagration is the
            potential for changing the geometry of a geometrically-favorable process
            vessel and the resultant risk of a criticality.  WSRC stated that about
            75% of the criticality risk is associated with hydrogen deflagration.

      e.    Criticality Safety:  WSRC has implemented a program to reduce the risk
            of an inadvertent criticality by assigning a Criticality Safety
            Specialist to each shift.  The Criticality Safety Specialist is a senior
            operator with additional training on criticality safety.  The
            Criticality Safety Specialist conducts a facility walkdown each shift
            looking for criticality safety infractions, such as incorrectly sized
            containers in a glovebox, and documents these walkdowns by completing a
            procedure checklist.  WSRC management stated that they normally observe
            significant operations, but that depends on the individuals initiative
            and knowledge of ongoing operations.

            This situation is comparable to the standard nuclear industry practice
            of incorporating quality assurance and radiological protection hold
            points in procedures which require these oversight functions to observe
            critical procedural steps to ensure compliance.  Considering the
            consequences of a criticality accident and that credit is taken in the
            accident analysis for the Criticality Safety Specialist as a preventive
            measure, the DNFSB staff suggests that additional procedural
            implementation of this program be considered to ensure that the safety
            envelope is maintained.  For example, inserting hold points at critical
            steps (e.g., line breaks, material transfers) in an operational or
            maintenance procedure would ensure that the Criticality Safety
            Specialist observes the activity.

      f.    Dissolving Operations:  The current startup plan does not include
            dissolving operations, but they are included in the BIO.  The Technical
            Standards that are applicable to dissolving operations do not comply
            with ANSI/NFPA 69 (American National Standard Institute/National Fire
            Protection Association), Explosion Prevention Systems.  The DNFSB staff
            believes that the Technical Standards should be revised prior to startup
            of dissolving operations.

5.    Future Actions:  The staff will perform follow-up reviews when DOE/WSRC
      actions are complete which is expected in early 1995.