United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for April 21, 2000

                       Headquarters Daily Report

                         APRIL 21, 2000

                    REPORT             NEGATIVE            NO INPUT
                    ATTACHED           INPUT RECEIVED      RECEIVED

REGION I                               X
REGION II                              X
REGION III                             X
REGION IV                              X

Licensee/Facility:                     Notification:

                                       MR Number: H-00-0029
University Of Missouri At Columbia     Date: 04/21/00

Subject: Unplanned High Radiation Field


On April 12, 2000, the University of Missouri at Columbia reported an
event with the potential to cause an overexposure to members of the staff
of the university's research reactor.  The licensee had been performing
inspections of the reactor's pool liner to determine its condition.  A
portion of the biological shield next to the Z basket area - a fuel
storage area in the pool - consists of blocks that can be removed.  These
blocks were removed on April 6, 2000, to facilitate an inspection of the
outer side of the pool wall, which was completed on April 12, 2000.  All
fuel had been removed from the Z basket area to the main part of the pool
near the reactor prior to the block removal.

The reactor experienced an unscheduled shut down on April 12, 2000, that
required the reactor to be refueled.  All fuel storage locations near the
reactor were filled with fuel.  To expedite the fuel movements necessary
to replace the core, a change was made to the refueling procedure to put
a fuel element in the rack in the Z basket.  When the element was placed
in the Z basket, a radiation monitor alarmed.  A heath physicist (HP)
investigated and found elevated radiation levels as she approached the
beam floor (an area administratively controlled as a locked high
radiation area).  The HP apparently realized that the fuel element in the
Z basket was the cause of the elevated radiation levels and alerted the
operating crew.  They recognized the cause independently and had already
moved the fuel element to a different position within the Z basket.  The
HP then returned to the beam port floor and measured a radiation field of
200 R/hr at the edge of the area where the shielding had been removed.
The operators then moved the fuel from the Z basket back to the reactor
which ended the event.  The licensee estimates that the elevated
radiation field existed for about three minutes.  No one was on the beam
floor when this happened and no overexposures occurred.  Based on the
reading of an area film badge on the beam floor wall the licensee
preliminarily calculated a dose rate of 312 R/hr where the shielding was

Reactor operations were placed on hold from about 2:30 pm until 8:30 pm
to evaluate and understand the event.  The incident was discussed with
reactor operations crews and others who were involved.  The shielding was
replaced and the Z basket area is currently tagged out to prevent fuel
from being placed in the area.  All non-routine work at the facility has
been suspended.  The licensee has established a team of managers to
determine root causes.

A team of three inspectors (from NRC Headquarters) conducted an
inspection on site on April 14, 2000. The inspection team investigated
the details of the event, and reviewed the licensee's response, root
cause investigation and corrective actions.  The NRC inspectors
determined that the event had no potential to affect members of the
public.  The NRC inspectors also reviewed the licensee identified
HEADQUARTERS      MORNING REPORT     PAGE  2          APRIL 21, 2000
MR Number: H-00-0029 (cont.)

weaknesses in development of the procedure for conducting the pool liner
inspection and in communications among the reactor staff regarding
facility status.  The NRC staff will continue to assess the event and
issue an inspection report.

Contact:  Marvin Mendonca, NRR       (301)415-1128
          Alexander Adams, NRR       (301)415-1127
Page Last Reviewed/Updated Thursday, March 29, 2012