DEFENSE NUCLEAR FACILITIES SAFETY BOARD

August 17, 1994


MEMORANDUM FOR:       G. W. Cunningham, Technical Director

FROM:                 Richard E. Tontodonato, Technical Staff

SUBJECT:              Trip Report on DNFSB Staff Review of Methods for Emplacing
                      Nuclear Devices for Underground Testing

1.   Purpose:  This report documents a DNFSB Staff review of methods for 
     emplacing nuclear devices for underground testing at the Nevada Test Site
     (NTS).  The first portion of this review was a May 2-5, 1994, trip by C.
     Martin, J. Preston, D. Winters, R. Zavadoski, and R. Tontodonato to the
     Lawrence Livermore National Laboratory (LLNL) and Los Alamos National
     Laboratory (LANL) to review methods for emplacing nuclear devices for
     underground testing at NTS.  The second portion of this review was a June
     15-16, 1994, trip by R. Tontodonato, C. Martin, and H. Massie to NTS to
     observe Exercise SHORTCAKE, which included emplacement of a simulated
     nuclear device in a vertical test shaft.

2.   Summary:  Based on this initial review, the emplacement methods, design
     criteria, and quality assurance provisions used by LLNL and LANL appear to
     provide adequate assurance that nuclear devices can be safely emplaced in
     deep vertical shafts for underground testing.  Observation of Exercise
     SHORTCAKE confirmed that the laboratories' designs were adequately
     translated into action at NTS.  However, there was no evidence that
     procedures were used during some portions of the exercise, and
     housekeeping was poor in the device installation tower and near the test
     shaft.

3.   Background:  Since nuclear testing was resumed in 1961, after a three year
     moratorium, almost all testing at NTS has been done underground.  Lowering
     the test device and associated instrumentation down a shaft for
     underground testing is called "emplacement."  Integrity of the structures
     used in emplacement is vital, since recovering a nuclear test device
     inadvertently dropped down a shaft that is potentially thousands of feet
     deep would be a difficult task.  When such an accident occurred in October
     1975, the Department of Energy  (DOE) chose to destroy the dropped weapon
     by conducting an adjacent nuclear test, rather than attempting to recover
     it.

4.   Discussion:

     a.     Emplacement methods:  The emplacement process takes two to three
            weeks depending on the depth of the hole, which is selected to
            accommodate the projected device yield.

              1.  LLNL and LANL both use NTS cranes for lifting and lowering
                  test devices, but use different approaches to suspending the
                  device from the lifting fixtures.  LLNL uses a single string
                  of heavy pipe sections threaded together to suspend test
                  devices.  LANL uses either two or four harnesses made of wire
                  rope to suspend test devices.

              2.  Both LLNL and LANL lower the device in steps, adding a length
                  of pipe or wire rope harness at each step.  The pipe or wire
                  rope must support the weight of the test device and its
                  instrumentation, as well as the loading caused by the addition
                  of the stemming materials (added to the hole to contain the
                  hot radioactive gases created by the test).  The high
                  confidence the labs place in this process is based on a mature
                  design methodology, quality assurance, and training and
                  qualification of personnel.

              3.  It is not obvious that either emplacement method is inherently
                  superior.  The difference in approach is related to the
                  generally heavier experimental apparatus used by LLNL.  The
                  pipes used by LLNL are made of fracture-resistant steel and
                  are easily inspected, but there is no redundant load path
                  should the emplacement pipe fail.  LANL uses two or four load-
                  bearing harnesses, but the wire ropes are difficult to inspect
                  and are not made from fracture-resistant materials.  Past
                  incidents during emplacement operations were caused by
                  problems with cranes and other ancillary hardware and did not
                  reveal fundamental flaws with either laboratory's approach to
                  emplacement.

       b.     Design criteria:

              1.  LLNL and LANL use conservative design criteria for load-
                  bearing equipment and hardware used in emplacement, including
                  NTS cranes, and pull test all load-bearing items before each
                  emplacement.  LLNL designs all components to carry at least
                  two times the emplaced load, and at least 1.5 times the load
                  resulting after the stemming materials are poured onto the
                  emplaced device.  LANL designs all components to carry at
                  least two times the emplaced load, and limits the emplaced
                  load on wire rope harnesses to no more than 25% of their
                  breaking strength.

              2.  LANL pull tests all load-bearing items to two times the actual
                  emplaced load, whereas LLNL pull tests at 1.13 to 1.5 times
                  the emplaced load, or the stemmed load, whichever is larger. 
                  LANL personnel consider that the factors of safety (applied to
                  the unstemmed, emplaced load) they use in design and pull
                  testing are large enough that the actual stemmed load will be
                  accommodated.  LANL believes that the adequacy of this
                  approach has been proven by their long history of successful
                  emplacements.

              3.  Seismic loadings have not been explicitly addressed.  Both
                  laboratories assume that the probability of a seismic event
                  occurring during emplacement or between emplacement and
                  detonation is negligible.  This assumption may be appropriate
                  for a notional test schedule of two to five tests per year (as
                  allowed by the Hatfield amendment).  However, the validity of
                  this assumption during past, aggressive test schedules of more
                  than 20 tests per year might be questioned.  It appears that
                  a documented analysis of the likelihood of a seismic event
                  initiating a significant failure during emplacement would be
                  valuable.
       
       c.     Quality assurance:  The LANL and LLNL quality assurance programs
              include inspection, testing, and certification of procured
              materials and hardware, pull testing of each load-bearing item
              before each use, traceability and control of items used in     
              emplacement, and annual recertification (through pull tests and 
              inspections) of reusable equipment such as cranes, platforms,  
              and lifting gear.  Items which are difficult to inspect        
              thoroughly, such as wire rope and threaded fasteners, are      
              subject to larger factors of safety than items which can be    
              adequately inspected.

       d.     Exercise SHORTCAKE:

              1.  Background:  During the current nuclear testing moratorium,
                  NTS is attempting to maintain nuclear testing proficiency by
                  conducting exercises.  Exercise SHORTCAKE featured the
                  delivery of a simulated device to the device installation
                  tower, installation of the device in the test canister,
                  auxiliary system testing, and emplacement of the canister and
                  instrumentation about 500 feet deep in a test shaft.  Neither
                  pre-stemming of the canister nor stemming of the hole were
                  included in the exercise.  The DNFSB Staff observed activities
                  from the beginning of the exercise through initial insertion
                  of the device canister in the hole, including activities in
                  the LLNL CP-9 control room.

              2.  Although the arming and firing portions of the exercise were
                  controlled by detailed checklists, other activities did not
                  appear to be adequately controlled:

                  (a)    The process of moving the device canister from the tower
                         into the hole was controlled by verbal instructions from
                         a foreman, who used no procedures or checklist.  The
                         Staff review team had been briefed that the crane
                         operator would raise the canister slightly before
                         lowering it each time the canister was allowed to move
                         down-hole.  The reason the canister is normally raised
                         before lowering is to assure the operator that there is
                         enough torque in the motor to control the down-hole
                         motion during descent.  This is an administrative
                         procedure that was adopted after a test device was
                         almost dropped during a prior emplacement.  This
                         practice was not observed by the review team to be
                         implemented during SHORTCAKE.  The only time the
                         canister was raised was when it was initially brought
                         out of the event site tower.

                  (b)    Workers installing the side panels on the canister used
                         power tools which sheared the heads off several bolts
                         (which they did not replace).  In addition, the workers
                         neglected to install several other bolts.

              3.  Housekeeping practices were poor, in violation of 29 CFR
                  1926.25 as invoked by DOE Orders 5480.4 and 5483.1A.  The
                  device installation tower appeared to be unnecessarily crowded
                  due to extraneous tools, equipment and garbage, which should
                  have been removed according to the event mechanical engineer's
                  checklist.  Numerous items were observed to be dropped into
                  the hole during the exercise, including bolts, bolt heads
                  inadvertently sheared off by power tools, and bolt ends
                  trimmed off using hand tools.

              4.  Construction and anchoring of the tower did not appear
                  adequate to withstand earthquake shock or other severe natural
                  phenomena.  This is consistent with the statements by LANL and
                  LLNL engineers that seismic events were not considered in the
                  design of the emplacement process.

              5.  The laboratory nuclear testing organizations were clearly
                  using this exercise as a training opportunity.  Several key
                  positions were staffed by two people, to maximize the training
                  benefit.  However, SHORTCAKE was not a high fidelity,
                  integrated exercise.  The Staff understands that DOE has
                  developed plans for two integrated exercises in early 1995.

5.     Future Staff Actions:

       a.     Conduct a detailed technical review of the standards and
              specifications governing design, inspection, testing, and
              certification for LLNL and LANL emplacements.

       b.     Further examine the laboratories'  rationale for neglecting seismic
              effects and LANL's basis for not explicitly accounting for loads
              caused by the addition of stemming materials.