DEFENSE NUCLEAR FACILITIES SAFETY BOARD

                                                   April 28, 1994

MEMORANDUM FOR: G. W. Cunningham, Technical Director

COPIES:             Board Members

FROM:               Roger Zavadoski

SUBJECT:            Trip Report on Ventilation/Filtration Systems
                    in Buildings 559 and 707 at the Rocky Flats
                    Plant

1. Purpose:  This report documents the results of a DNFSB staff
   visit to the Rocky Flats Plant to conduct a review of the
   ventilation/filtration systems in Buildings 559 and 707.  This
   review was conducted by R. Kasdorf and R. Zavadoski of the DNFSB
   staff during the period of March 21-23, 1994.

2. Summary:

   a. The scope of this review included the ventilation/filtration
      systems at Buildings 559 and 707.

   b. Recent failures to meet operational safety requirements
      (OSR) at Buildings 559 and 707 were reviewed.  These
      failures are more important considering the unreviewed
      safety question determination for other buildings at Rocky
      Flats where all stages of filtration are not required to be
      periodically ascertained.
   
3. Background:

   a. The DNFSB staff had previously reviewed the
      ventilation/filtration systems at the Rocky Flats Plant
      during the period October 18-20, 1993.  At the time and
      through subsequent correspondence (letter, Conway to
      Grumbly, February 1, 1994) the staff pointed out that the
      filter testing being conducted was inconsistent in that some
      facilities (e.g. Buildings 707 and 559) required filter
      testing of each stage of filtration while others (e.g.
      Buildings 371 and 771) required testing of only the final
      stage.  All facilities assume full credit for all stages in
      their Safety Analysis Reports.  

4. Discussion/Observations:

   a. The staff reviewed testing results from tests of the
      filtration systems in Buildings 559 and 707.  The acceptance
      criteria and removal efficiency assumed in the SAR is
      99.95%.  Several stages were reported to have failed this
      criteria.

      1.  For Building 707, plenum 102:  

          (a)   On December 12, 1993, the third stage had a
                reported efficiency of 99.31417%.

          (b)   On December 6, 1993, the fourth stage had a
                reported efficiency of 97.927%. 

          (c)   On January 12, 1994, the second stage had a
                reported efficiency of 99.604%.

      2.  Building 559: 

          (a)   Plenum 302, November 11, 1993, the first stage
                reported efficiency was 99.88%. 

          (b)   Plenum 301, November 16, 1993, the first stage
                reported efficiency of 99.56375%. 

   b. The failures reported are not catastrophic and are
      exacerbated by the test method employed.  Presently the
      Rocky Flats Plant determines filter efficiency by
      determining penetration of Dioctylphthalate (DOP) particles
      as they traverse the downstream face of each High Efficiency
      Particulate Air (HEPA) filter during a test.  The highest
      penetration observed on a particular filter is recorded for
      the entire filter.  This method was once endorsed by the
      ANSI N510 standard, "Testing of Nuclear Air Treatment
      Systems."  The current method in ANSI N510 floods the entire
      stage and measures DOP concentration downstream of the
      entire stage.

      Facility personnel described the changes being incorporated
      into the test procedure to minimize the effect of the
      current scanning method.  A shroud will be utilized over
      each filter (as allowed by current standards) which will
      minimize the effect of minute local penetrations.  Current
      flooding techniques, which are more efficient and test the
      stage as a whole, are difficult to backfit into plenums
      which were not designed for them.  The current standards
      apply only to a single mounted stage; several plenums at the
      Rocky Flats Plant have back to back mounting of HEPA
      filters.

   c. The Rocky Flats Plant is formally considering the
      applicability of an unreviewed safety question to those
      plutonium facilities that do not test all stages of HEPA
      filtered exhausts.  The compensatory actions for the
      facilities affected by this determination is still under
      review.

   d. Filter test personnel stated that the filtration systems in
      buildings where work with uranium was performed are not
      currently tested.  There are currently no approved SARs for
      these buildings.  The filter test personnel were not aware
      of whether the safety bases for these buildings relied on
      HEPA filtration.

   e. During a tour of Building 707, building personnel indicated
      that the dehumidification systems for Zone II supply air had
      been disabled.  The building personnel were not aware of
      whether an engineering evaluation had been done.  Since
      plutonium is stored in some Zone II area vaults, humidity
      may be of concern.

   f. Facility personnel also mentioned that they are:

      1.  Continuing their shelf-life studies for HEPA filters; and

      2.  Increasing the sealing gasket thickness from 1/4" to 3/8"
          on all future orders of HEPA filters.

   g. The DNFSB staff walked down the ventilation/filtration
      systems in Buildings 559 and 707.  In general, the
      housekeeping appeared acceptable and improved over past
      observations.
  
5. Future Staff Actions:  The DNFSB Staff will continue to review
   the ventilation/filtration systems at the Rocky Flats Plant. 
   When available, the USQ determination and related compensatory
   measures will be reviewed by the DNFSB staff.  The staff will
   follow-up on the question of testing filtration systems in the
   uranium building and the need for dehumidification in the
   Building 707, Zone II air supply.