`[Federal Register Volume 69, Number 216 (Tuesday, November 9, 2004)]
[Notices]
[Pages 64996-64998]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-24890]


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NUCLEAR REGULATORY COMMISSION


Notice of Availability of Interim Staff Guidance Documents For 
Fuel Cycle Facilities

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of availability.

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FOR FURTHER INFORMATION CONTACT: Wilkins Smith, Project Manager, 
Technical Support Group, Division of Fuel Cycle Safety and Safeguards, 
Office of Nuclear Material Safety and Safeguards, U.S. Nuclear 
Regulatory Commission, Washington, DC 20005-0001. Telephone: (301) 415-
5788; fax number: (301) 415-5370; e-mail: [email protected].

SUPPLEMENTARY INFORMATION:

I. Introduction

    The Nuclear Regulatory Commission (NRC) plans to issue Interim 
Staff Guidance (ISG) documents for fuel cycle facilities. These ISG 
documents provide clarifying guidance to the NRC staff when reviewing 
either a license application or a license amendment request for a fuel 
cycle facility under 10 CFR part 70. The NRC is soliciting public 
comments on the ISG documents which will be considered in the final 
versions or subsequent revisions.

II. Summary

    The purpose of this notice is to provide the public an opportunity 
to review and comment on a draft Interim Staff Guidance document for 
fuel cycle facilities. Interim Staff Guidance-09 provides guidance to 
NRC staff relative the requirements associated with the use of 
Initiating Event Frequencies (IEFs) for demonstrating compliance with 
the performance requirements of 10 CFR 70.61.

III. Interim Staff Guidance-09, Initiating Event Frequency, Draft 
October 20, 2004 Issue

    This guidance addresses the measures needed to assure the validity 
and maintenance of initiating event frequencies (IEFs) used to 
demonstrate compliance with the performance requirements for 10 CFR 
70.61.

Introduction

    The purpose of this Interim Staff Guidance (ISG) is to clarify the 
use of IEFs for demonstrating compliance with the performance 
requirements of 10 CFR 70.61. NUREG-1718, ``Standard Review Plan for 
the Review of an Application for a Mixed Oxide (MOX) Fuel Fabrication 
Facility,'' and NUREG-1520, ``Standard Review Plan for the Review of a 
License Application for a Fuel Cycle Facility,'' provide methods for 
reviewing integrated safety analyses (ISAs), employing a semi-
quantitative risk index method. While one of these methods is used 
below to illustrate the use of IEFs, applicants and licensees may use 
other methods which would produce similar results. There is no 
particular method explicitly mandated, and sequences that are risk 
significant or marginally acceptable are candidates for more detailed 
evaluation by the applicant or licensee and reviewer.

Discussion

    Each licensee or applicant is required to perform an ISA to 
identify all credible high-consequence and intermediate-consequence 
events. The risk of each such credible event is to be limited through 
the use of appropriate engineered and/or administrative controls to 
meet the performance requirements of 10 CFR 70.61. Such a control is 
referred to as an item relied on for safety (IROFS). In turn, a safety 
program must be established and maintained to assure that each IROFS is 
available and reliable to perform its intended function when needed. 
The safety program may be graded such that management measures applied 
are graded commensurate with the reduction of risk attributable to that 
item. In addition, a configuration management system must be 
established pursuant to Sec.  70.72, to evaluate changes, to assure, in 
part, that the IROFS are not removed without at least equivalent 
replacement of the safety function.
    The risk of each credible event is determined by cross-referencing 
the severity of the consequence of the unmitigated accident sequence 
with the likelihood of occurrence in a risk matrix with risk index 
values. The likelihood of occurrence risk index values can be 
determined by considering the criteria in NUREG-1520, Tables A-9 
through A-11. Accident sequences result from initiating events which 
are followed by the failure of one or more IROFS. Initiating events can 
be (1) an external event such as a hurricane or earthquake, (2) a 
facility event external to the process being analyzed (e.g., fires, 
explosions, failures of other equipment, flooding from facility water 
sources), (3) deviations from normal operations of the process 
(credible abnormal events), or (4) failures of an IROFS in the process. 
Additional guidance regarding initiating probabilities from natural 
phenomena hazards are addressed in ISG-08, Natural Phenomena Hazards.
    An initiating event does not have to be an IROFS failure. An item 
only becomes an IROFS if it is credited in the ISA for mitigation or 
prevention per the definition in Sec.  70.4. If an item, whose failure 
initiates an event, has strictly an operational function, it does not 
have to be an IROFS. This applies to external events and can apply to 
internal events. If the item whose failure initiates an event, has 
solely a safety function that is credited in the ISA, then it should be 
an IROFS. If the item has both an operational and a safety function, 
the safety function should make it an IROFS (for its ISA credited 
safety features only).
    IEFs can play a significant role in determining whether the 
performance requirements of Sec.  70.61 are met for a particular 
accident sequence. Whether an initiating event is due to an IROFS or a 
non-IROFS failure, licensees should take appropriate action to assure 
that any change to the basis for assigning an IEF value to that event 
is evaluated on a continuing basis to ensure continued compliance with 
the performance requirements. For example, a non-IROFS component may 
not be subject to the same QA program controls and other management 
measures that an IROFS

[[Page 64997]]

would receive (i.e., surveillance, testing, procurement, etc.). 
However, appropriate management controls should be considered, in a 
graded manner, to provide assurance that performance requirements are 
met over time. The ability to identify a non-IROFS component failure, 
similar to that for IROFS, may be needed to provide feedback on failure 
rates and IEFs to the ISA process. Changes to the IEF values may result 
from changes to a component's design, procurement, operation, or 
maintenance history, as well as new or increased external plant 
hazards, and should be considered in a graded approach.

Regulatory Basis

    10 CFR 70.61, Performance Requirements.
    10 CFR 70.62, Safety Program and Integrated Safety Analysis.
    10 CFR 70.65, Additional Content of Applications.
    10 CFR 70.72, Facility Changes and Change Process.

Applicability

    This guidance is for use in those cases where an applicant or 
licensee chooses to use an IROFS or non-IROFS failure IEF for risk 
determination.

Technical Review Guidance

1. IEF and Identification of an IROFS
    Example. A licensee uses a heater/blower unit to heat a 
UF6 cylinder in a hot box to liquify the contents prior to 
sampling. The unmitigated accident sequence involves the failure of the 
controller for the heater/blower resulting in overheating the cylinder. 
This results in the cylinder becoming overpressurized and rupturing, 
releasing the UF6 to the surrounding process area. Such a 
release is analyzed to exceed the performance requirements of Sec.  
70.61. The licensee has two basic choices: (1) Assume the initiating 
event probability =1 and provide an appropriate level of mitigation or 
prevention solely through one or more IROFS, or (2) assign a value to 
the initiating event (blower/heater controller failure) and provide one 
or more preventive or mitigative IROFS to bring the accident sequence 
risk within the performance requirements.
    If the licensee chooses (2) above and assigns an appropriate value 
to the IEF, the indices of NUREG-1520, Table A-9, Failure Frequency 
Index Number, may be used. The controller for the heater/blower unit 
would be assigned an appropriate Frequency Index Number. The licensee 
would then analyze the accident sequence and determine whether 
additional IROFS are necessary to meet the performance requirements. 
There are now two variables that feed into the risk determination: one 
or more IROFS failure frequencies and the IEF of the non-IROFS 
controller for the heater/blower unit. Changes to the initiating event 
that impact the IEF of the non-IROFS controller for the heater/blower 
unit in a manner that changes the licensee's previous determination of 
compliance with the performance requirements must be evaluated per 
Sec.  70.72(a).
2. IEF Index Use
    Indices may be used to determine the overall likelihood of an 
accident sequence. NUREG-1520, Table A-9, Failure Frequency Index 
Numbers, identifies frequency index numbers based on specified 
evidence. The evidence used by applicants and licensees should be 
supportable and documented in the ISA summary as required by Sec.  
70.65(b)(4). The evidence cited in the ISA documentation should not be 
limited to anecdotal accounts and must demonstrate compliance with the 
descriptive definitions of unlikely, highly unlikely, and credible, as 
required by Sec.  70.65(b)(9). The rigor and specificity of the 
documented evidence should be commensurate with the item's importance 
to safety, and the data should support the frequency chosen (e.g., data 
from 30 years of plant operating experience based on a single component 
typically could not be expected to support a 10 E-2 failure 
probability).
    An item's failure rate should be determined from actual data for 
that specific component or safety function in the current system design 
under the current environmental conditions. When specific failure data 
is limited or not available, the applicant or licensee may use more 
``generic'' data with appropriate substantiation. However, when less 
specific failure data is available, appropriate conservatism should be 
exercised in assigning frequency indices. The footnote to Table A-9 
that states ``indices less than (more negative than) -1 should not be 
assigned to IROFS unless the configuration management, auditing and 
other management measures are of high quality, because without those 
measures, the IROFS may be changed or not maintained,'' should also be 
applied to non-IROFS IEFs. In this case, appropriate management 
controls should be provided to assure that any changes to the evidence 
supporting IEF indices will be identified and promptly evaluated to 
ensure that the performance requirements of Sec.  70.61 are met. A 
graded approach may be used in applying management controls based on 
the IEF values; however, how this will be done should be identified in 
the ISA Summary.
    Possible changes to IEFs, failure rates, and the assumptions they 
are based on should be periodically evaluated by the licensee to assure 
that any change to an IEF has been accounted for in the ISA process. 
Over time an IEF may change because of component aging or 
deterioration. Maintenance and performance experience should be fed 
back into the IEF evaluation. IEF changes could involve, for example, 
the introduction of new or hazards from nearby processes or new 
materials, changes in design, maintenance, or operation activities, 
etc. The applicant or licensee should establish management measures, 
which may be graded, to periodically confirm that there have been no 
changes to the ISA assumptions. For example, an applicant or licensee 
may choose to verify that there have been no changes to hazards from 
maintenance activities during a certain period of time based on an 
appropriate documented technical review or audit under the QA program.
    Whatever strategy the applicant or licensee chooses to employ 
should have an outcome of timely identification, and periodic 
evaluation, of failure rates followed by a prompt evaluation of the 
failure rate change on the ISA assumptions. This can be accomplished in 
accordance with the corrective maintenance program and/or the Quality 
Assurance (QA) problem identification and corrective action system.
    Indices particularly relied upon (i.e., <-1) for overall likelihood 
will be reviewed during the ISA review process.
3. External IEFs
    Possible changes to non-natural phenomena external events should be 
periodically evaluated by the licensee to assure that any change to an 
IEF has been accounted for in the ISA process. Such changes could 
involve, for example, the introduction of new hazards from an adjoining 
industrial site, changes in adjoining transportation activities, etc. 
The applicant or licensee should establish management measures, which 
may be graded, to periodically confirm that there have been no changes 
to the ISA assumptions. For example, an applicant or licensee may 
choose to verify that there have been no changes to outside hazards 
based on a two- to three-year review under the QA program.

[[Page 64998]]

4. Assurance
    The Safety Program required by Sec.  70.62(a) should have 
provisions for implementing the appropriate management controls to 
maintain the validity of the IEFs. Consideration should also be given 
to commitments in the QA program or a specific license condition.

References

U.S. Code of Federal Regulations, title 10, part 70, ``Domestic 
Licensing of Special Nuclear Material,'' U.S. Government Printing 
Office, January 1, 2003.
NUREG-1520, ``Standard Review Plan for the Review of a License 
Application for a Fuel Cycle Facility,'' U.S. Nuclear Regulatory 
Commission, Office of Nuclear Material Safety and Safeguards, March 
2002.
NUREG-1718, ``Standard Review Plan for the Review of an Application 
for a Mixed Oxide (MOX) Fuel Fabrication Facility,'' U.S. Nuclear 
Regulatory Commission, Office of Nuclear Material Safety and 
Safeguards, August 2000.

IV. Further Information

    Comments and questions should be directed to the NRC contact listed 
above by December 9, 2004. Comments received after this date will be 
considered if it is practical to do so, but assurance of consideration 
cannot be given to comments received after this date.

    Dated in Rockville, Maryland, this 3rd day of November, 2004.
For the Nuclear Regulatory Commission.
Melanie A. Galloway,
Chief, Technical Support Group, Division of Fuel Cycle Safety and 
Safeguards, Office of Nuclear Material Safety and Safeguards.
[FR Doc. 04-24890 Filed 11-8-04; 8:45 am]
BILLING CODE 7590-01-P`