United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-63: Management Attention to the Establishment and Maintenance of a Nuclear Criticality Safety Program

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
              OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
                           WASHINGTON, D.C.  20555

                               October 3, 1990


Information Notice No. 90-63:  MANAGEMENT ATTENTION TO THE ESTABLISHMENT 
                                   AND MAINTENANCE OF A NUCLEAR CRITICALITY 
                                   SAFETY PROGRAM 


Addressees: 

All fuel cycle licensees and other licensees possessing more than critical 
mass quantities of special nuclear material. 

Purpose: 

This information notice is provided to alert addressees to an incident 
resulting from inadequate management attention to the establishment and 
maintenance of a nuclear criticality safety program.  The licensee's 
inattention to Information Notice No. 89-24, Nuclear Criticality Safety, 
dated March 6, 1989, may have been a contributing factor in the incident.  
It is expected that licensees will review this information and the 1989 
Information Notice for applicability to their facilities and consider 
actions, as appropriate, to avoid similar problems.  However, suggestions 
contained in this Information Notice do not constitute U.S. Nuclear 
Regulatory Commission (NRC) requirements; therefore, no specific action or 
written response is required. 

Description of Circumstances: 

In March 1990, a licensee's routine sample analysis for a Raschig-ring 
filled waste collection tank (a non-favorable geometry vessel) yielded a 
concentration of approximately 2 grams of highly enriched uranium per liter 
of solution.  Contents of the tank are normally transferred to a second 
larger tank (a non-favorable geometry vessel without Raschig rings) at a 
release limit of 0.01 grams uranium per liter.  The analysis of a second 
sample confirmed that a major upset had occurred in the waste collection 
system.  Consequently, the waste processing area was shutdown, and the waste 
collection tank was isolated.  Corrective actions were taken to recover the 
uranium (in excess of 4 kilograms).  

The licensee's investigation team concluded that the contents of two 
favorable diameter 11-liter cylinders, one or both containing high 
concentration solution, had been dumped into a sump used to pump solution to 
the waste collection tank.  By procedure, operators were allowed to dump low 
concentration uranium solutions into the sump after receiving authorization 
and key access from supervisors.  Findings which supported the team's 
conclusion are:  (1) the quantity of uranium in the tank, (2) an operator's 
statement that two 11-liter cylinders of process 



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solution were poured into the sump, (3) traces of yellow uranium solids in 
the sump and filter, and (4) ineffective isolation of the sump caused by 
failure to perform maintenance and to conduct access control.  The 
investigation team also speculated that one or both of the 11-liter 
cylinders had been mislabelled based on an operator's statement that 
11-liter cylinders were mislabelled in the past and the team's observation 
of an 11-liter cylinder of high concentration solution that was improperly 
labelled.

The failure of the licensee's management control systems resulted in an 
unsafe transfer of the uranium solution through the sump into the collection 
tank.  Both the sump and the collection tank had risks of a criticality 
event and no controls remained.  Even though the administrative control led 
to the detection of the high concentration of uranium and precluded its 
transfer to the second larger tank, an additional unsafe transfer could have 
occurred with only one unlikely, independent, and concurrent change in 
process conditions (viz., recording the wrong analysis or using the wrong 
sample analysis, etc.).  In both the actual incident and the postulated case 
of transfer of concentrated solution to the second larger tank, controls to 
satisfy the double contingency principle were not implemented. 

Discussion: 

This event and those events described in the 1989 Information Notice 
emphasize the need for continuing vigilance in providing a sound nuclear 
safety program.  Although the licensee had a copy of the 1989 Information 
Notice on file, no action was taken to avoid similar events.  Some of the 
recommendations made by the licensee's investigation team are listed below.  
Licensees are encouraged to review these recommendations, the 1989 
Information Notice, and their own programs to ensure nuclear criticality 
safety. 

-    Eliminate sumps and install piping to transfer waste solutions, 
     thereby, eliminating the use of the 11-liter cylinders in this 
     application.

-    Evaluate the procedures and practices for affixing labels to 11-liter 
     cylinders in all process areas.

-    Install in-line detectors and totalizers on all streams to waste 
     collection tanks containing Raschig rings.  Consider automatic shutoff 
     of the flow when a detected uranium concentration exceeds an acceptable 
     nuclear criticality control limit.

-    Install additional controls on all streams to the collection tank 
     without Raschig rings.  This should include an evaluation of 
     interlocked valves, as well as valves controlled by in-line detectors 
     or conductivity meters connected to an alarm system.

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-    Develop training material for, and train, first responders to unusual 
     events.

-    Retrain supervisory personnel on issues important to safety, labor 
     relations, training, and emergency response.

-    Evaluate the existing training program to ensure that personnel are 
     trained and knowledgeable of assigned tasks in waste processing areas 
     and of nuclear criticality safety issues, including selected 
     criticality accident histories.

-    Reevaluate all nuclear criticality safety analyses to ensure proper 
     application of the double contingency principle, with emphasis on 
     unsafe geometry vessels.

-    Reevaluate the audit and inspection programs to ensure that management 
     control systems are being properly implemented.

-    Review operating procedures for accuracy and completeness.

-    Retrain personnel with procedural requirements with emphasis on 
     mandatory compliance.

No specific action or written response is required by this Information 
Notice.  If you have any questions, please contact the technical contacts 
listed below or the Regional Administrator of the appropriate regional 
office. 




                                   Richard E. Cunningham, Director
                                   Division of Industrial and 
                                     Medical Nuclear Safety
                                   Office of Nuclear Material Safety
                                     and Safeguards

Technical Contacts:  Edward McAlpine, Region II
                     (404) 331-5547

                     W. Scott Pennington, NMSS
                     (301) 492-0693

Attachments:
1.   Information Notice No. 89-24,
       Nuclear Criticality Safety,
       dtd March 6, 1989
2.   List of Recently Issued
       NMSS Information Notices
3.   List of Recently Issued
       NRC Information Notices
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