United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 94-73: Clarification of Criticality Reporting Criteria

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

October 12, 1994


NRC INFORMATION NOTICE 94-73:  CLARIFICATION OF CRITICALITY REPORTING CRITERIA


Addressees

All fuel fabrication facilities.

Purpose

The U.S. Nuclear Regulatory Commission is issuing this information notice to
alert addressees to a clarification of the criticality reporting criteria
previously provided in Bulletin 91-01, Supplement 1.  It is expected that
recipients will review the information for applicability to their facilities
and consider actions, as appropriate, to ensure proper reporting.  However,
suggestions contained in this information notice are not NRC requirements;
therefore, no specific action nor written response is required.

Background

On October 18, 1991, Bulletin 91-01, "Reporting Loss of Criticality Safety
Controls," was issued.  It requested that addressees inform NRC of their
criteria and procedures that ensure the prompt evaluation and reporting of
conditions and events involving criticality safety.  The NRC staff reviewed
each licensee's response to the bulletin.  Most responses reflected a
commitment to promptly evaluate events with criticality safety implications,
report the most significant events immediately to NRC, and report less
significant events within 24 hours.  Also, we received numerous comments on
the bulletin through correspondence and various meetings and workshops.  A
major concern was the bulletin's statement that loss or lack of a controlled
parameter related to criticality safety should be reported to NRC immediately. 
Several persons noted that further clarification regarding the definition of
"a loss of a controlled parameter" is needed.  Others noted that a loss of a
controlled parameter is not always a significant event warranting an immediate
report (e.g., if the event involves only a small amount of special nuclear
material).  Some licensees maintained that they should report events
immediately, to NRC, only if there were a significant threat of a criticality
accident or if the severity of the threat could not be readily determined.

As a follow-up to Bulletin 91-01, Supplement 1 was issued on July 27, 1993. 
The supplement was issued to (1) provide addressees clearer reporting
criteria; (2) request that addressees take certain actions; (3) require that
all addressees report to NRC whether, and to what extent, the requested
actions would be taken; and (4) notify NRC when actions associated with this
bulletin were completed.


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Bulletin 91-01, Supplement 1, was not intended to affect license requirements
nor licensee actions involving accident mitigation, emergency response, nor
long-term corrective measures.  Such actions should be performed in accordance
with the license and established regulations.

Description of Circumstances

Subsequent to the issuance of Bulletin 91-01, Supplement 1, NRC received
significant comments.  In response to those comments, we are clarifying
Criterion 1 for reporting events immediately.

Discussion

Bulletin 91-01, Supplement 1 was issued to clarify the events NRC wanted
reported immediately.  It limited immediate reporting to those cases where
(1) moderation was used as the primary criticality control, or (2) more than a
safe mass of fissionable material was involved (regardless of the type of
controls used to satisfy the double contingency principle).  In addition, the
cases had to meet one or more of the four immediate reporting criteria that
were listed in the supplement.  For further clarification, definitions were
provided for the four terms used in the immediate reporting criteria.

As noted, NRC received significant comments after the issuance of
Bulletin 91-01, Supplement 1,  In response, we are rephrasing Criterion 1
of the Supplement by expressing it as two separate criteria.  As a result,
there are now five criteria.  We are also making it clear that we expect the
reporting individual to be one who is knowledgeable about the plant's
operations, such as an operator or a manager.

The resulting criteria, and the accompanying definitions of terms, are
presented in their entirety below.

Immediate Reporting Criteria

NRC requests that the following situations should be identified and reported
within 4 hours of the initial observation of the incident by a knowledgeable
individual, such as an operator or a manager.  These include situations where
(1) moderation is used as the primary criticality control, or (2) more than a
safe mass of fissionable material is involved (regardless of the type of
controls used to satisfy the double contingency principle).  In addition, the
situation must meet one or more of the five immediate reporting criteria
listed below: 

1.  When, for a given criticality pathway, the controls, control systems, or
    controlled parameters that provide for double contingency cannot be
    reestablished within 4 hours.

2.  When, if double contingency has been reestablished within 4 hours, and

    a.  only one controlled parameter is used for a given criticality pathway,
        and more than one control system has been replaced or modified; or,.                                                      IN 94-73
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    b.  more than one controlled parameter is used for a given criticality
        pathway, and the control systems for more than one controlled
        parameter have been replaced or modified.

3.  The occurrence of any unanticipated or unanalyzed event for which the
    safety significance of the event or corrective actions to re-establish the
    double contingency principle are not readily identifiable.

4.  Any case where it is determined that a criticality safety analysis was
    deficient and where the necessary controlled parameters were not
    established or maintained. 

5.  Any event involving a controlled parameter previously identified by NRC or
    the licensee as requiring immediate reporting to NRC, and where the double
    contingency principle cannot be re-established within 4 hours after the
    initial observation of the event.

Definitions

    Control means a restriction established to limit: (1) the behavior of
    individuals to prescribed actions, or (2) the behavior of a variable or
    the operation of a component, a process, a portion of a process, or a
    system to performance within defined limits, to prevent an accident.

    Controlled parameter means a measurable variable whose value is maintained
    within established limits, to ensure the safety of an operation.

    Control system means a collection of restrictions that effectively
    functions as a single control.

    Double contingency means, for each criticality pathway, the use of control
    systems in such a way that two unlikely, concurrent, independent control
    system failures would have to occur before an inadvertent criticality
    would be possible.

Events and/or conditions that satisfy the above criteria should be reported
within 4 hours from the initial observation, in accordance with 10 CFR 20.2202
and 10 CFR 70.50.

All other criticality safety events that do not meet the aforementioned
criteria, but still result in a violation of the double contingency principle,
such as events where the double contingency principle is violated but control
is immediately re-established, should be reported to NRC within 24 hours, in
accordance with the commitments in the responses to Bulletin 91-01, and
Bulletin 91-01, Supplement 1. 

It is expected that criticality safety events will be promptly evaluated and
that appropriate management and technical personnel will be available 24 hours
a day to perform such evaluations.
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It should be emphasized that it is important that NRC be notified of events
related to criticality safety and that if there is any doubt as to whether an
event should be reported, the NRC should be contacted.

Information Notice Treatment

Addressees may wish to review their criticality safety reporting procedures to
ensure that they meet or exceed the reporting criteria described in this
information notice.  If you have any questions about the information in this
notice, please contact the technical contact listed below or the appropriate
regional office.


                                    original signed by

                              Robert F. Burnett, Director
                              Division of Fuel Cycle Safety
                                and Safeguards
                              Office of Nuclear Material Safety 
                                and Safeguards

Technical contact:  Jerry Roth, NMSS 
                    (301) 415-7156

Attachments:
1. List of Recently Issued NMSS Information Notices
2. List of Recently Issued NRC information Notices                      

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