United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-66: Incomplete Draining and Drying of Shipping Casks

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                              October 25, 1990


Information Notice No. 90-66:  INCOMPLETE DRAINING AND DRYING OF 
                                   SHIPPING CASKS


Addressees:

All holders of operating licenses for nuclear power reactors and all 
registered users of NRC approved waste shipping packages.

Purpose:

This information notice is intended to alert addressees to a possible safety 
problem resulting from incomplete draining and drying of shipping casks.  It 
is expected that recipients will review the information for applicability to 
their facilities and consider actions, as appropriate, to avoid similar 
problems.  However, suggestions contained in this information notice do not 
constitute NRC requirements; therefore, no specific action or written 
response is required.

Description of Circumstances:

On May 9, 1990, a Chem-Nuclear System (CNSI) operator opened a Transnuclear, 
TN-RAM shipping cask (USA/9233/B(U)) containing approximately 16,000 curies 
of waste-irradiated hardware (sheared control rod blades and local power 
range monitors) at the Low-Level Radioactive Waste Disposal Site operated by 
CNSI at Barnwell, South Carolina.  The irradiated hardware was to be placed 
in the Class C waste trench.  When the CNSI operator opened the shipping 
cask, approximately 75 gallons of water, having a near contact dose rate of 
5 mr/hr, spilled from the cask, contaminating the off-loading equipment and 
the surrounding ground area.  CNSI personnel immediately closed the cask, 
removed it from the trench area, and placed it in a secure parking area 
within the burial site.  Subsequently, when the cask was completely 
dewatered at the waste facility, an additional 121 gallons of contaminated 
water was removed from the cask.  The total volume of water found in this 
event was approximately 40 percent of the total cask volume.  

Discussion:

The shipment originated at Millstone Nuclear Power Station, Unit 1.  The 
irradiated hardware was in a waste liner which was stored in the spent fuel 
pool.  The waste liner and cask were to be drained and dried before 
shipment. 

The main cause of this event was an inadequate procedure used for draining 
and drying the cask and liner.  This procedure failed to incorporate any 
method for quantifying the amount of water drained from the cask.  
Additionally, this procedure failed to specify an accurate reference value 
for the pressure of the 

9010190004 
.

                                                            IN 90-66
                                                            October 25, 1990
                                                            Page 2 of 2


cask cavity with which to conduct the "dryness verification" test.  The 
procedure specified that the test be conducted at any pressure above a 
"minimum" pressure of 10 mbar, while the safety analysis report (SAR) called 
for the test to be conducted at a pressure of 10 mbar (+2, -0 mbar).  As a 
result, the test was actually conducted at 27 mbar, which was the vapor 
pressure for water at the ambient temperature.  Because the pressure in the 
cask cavity was not sufficiently below the vapor pressure of water, the test 
results were incorrectly interpreted, which allowed water to remain 
undetected in the cask.  

Since this event the license holder has corrected these deficiencies in the 
test procedure.  The revised test procedure requires that the water drained 
from the cask be quantified and compared to the volume of the container and 
that the dryness test be consistent with the SAR by specifying that the 
dryness test be performed at 10 mbar (+2, -0 mbar).

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
one of the technical contacts listed below or the appropriate NRC project 
manager.




                              Charles E. Rossi, Director
                              Division of Operational Events Assessment
                              Office of Nuclear Reactor Regulation


Technical Contacts:  George H. Gardes, NMSS
                     (301) 492-0495

                     Joseph T. Furia, RI
                     (215) 337-5373


Attachment:  List of Recently Issued NRC Information Notices 
.ENDEND
Page Last Reviewed/Updated Tuesday, November 12, 2013