January 14, 2011 

MEMORANDUM TO: Thomas G. Hiltz, Chief 

 Advanced Fuel Cycle, Enrichment 

 and Uranium Conversion Branch 

 Division of Fuel Cycle Safety 

 and Safeguards 

 Office of Nuclear Material Safety 

 and Safeguards 

FROM: Matthew A. Bartlett, Project Manager /RA/ 

 Advanced Fuel Cycle, Enrichment 

 and Uranium Conversion Branch 

 Division of Fuel Cycle Safety 

 and Safeguards 

 Office of Nuclear Material Safety 

 and Safeguards 

SUBJECT: NOVEMBER 15-16, 2010, TELEPHONE CALL TO DISCUSS 

THE USE OF PASSIVE ENGINEERED ITEMS RELIED ON FOR 

SAFETY FOR EXTERNALLY INITIATED EVENTS AND 

NATURAL PHENOMENON (TAC NO. L32739) 

On November 15-16, 2010, the staff conducted two conference calls with International Isotopes, 

Inc. (INIS) and its contractor. The purpose of the calls was to discuss implementation of the 

guidance in NUREG-1520, Revision 1, for the use of passive engineered items relied on for 

safety (IROFS). The discussion centered on identifying the appropriate likelihood index for 

externally initiated events which may cause system failure. The U.S. Nuclear Regulatory 

Commission’s staff and INIS agreed that under certain circumstances, the default value for 

passive engineered IROFS (i.e., 10-3) listed in Table A-10 of the NUREG is not appropriate. As 

a result of the discussion, the staff will update the request for additional information which 

addresses passive engineered IROFS; and INIS will review and modify applicable portions of 

their Integrated Safety Analysis. 

 

Enclosed is the telephone summary for your use. The summary contains no proprietary or 

classified information. 

Enclosure: 

As stated 

Docket No. 40-9086 

cc: Mr. John J. Miller, CHP 

 International Isotopes, Inc. 

 4137 Commerce Circle 

 Idaho Falls, ID 83401 
MEMORANDUM TO: Thomas G. Hiltz, Chief 

 Advanced Fuel Cycle, Enrichment 

 and Uranium Conversion Branch 

 Division of Fuel Cycle Safety 

 and Safeguards 

 Office of Nuclear Material Safety 

 and Safeguards 

FROM: Matthew A. Bartlett, Project Manager /RA/ 

 Advanced Fuel Cycle, Enrichment 

 and Uranium Conversion Branch 

 Division of Fuel Cycle Safety 

 and Safeguards 

 Office of Nuclear Material Safety 

 and Safeguards 

SUBJECT: NOVEMBER 15-16, 2010, TELEPHONE CALL TO DISCUSS 

THE USE OF PASSIVE ENGINEERED ITEMS RELIED ON FOR 

SAFETY FOR EXTERNALLY INITIATED EVENTS AND NATURAL 

PHENOMENON (TAC NO. L32739) 

On November 15-16, 2010, the staff conducted two conference calls with International Isotopes, Inc. 

(INIS) and its contractor. The purpose of the calls was to discuss implementation of the guidance in 

NUREG-1520, Revision 1, for the use of passive engineered items relied on for safety (IROFS). The 

discussion centered on identifying the appropriate likelihood index for externally initiated events which 

may cause system failure. The U.S. Nuclear Regulatory Commission’s staff and INIS agreed that under 

certain circumstances, the default value for passive engineered IROFS (i.e., 10-3) listed in Table A-10 of 

the NUREG is not appropriate. As a result of the discussion, the staff will update the request for 

additional information which addresses passive engineered IROFS; and INIS will review and modify 

applicable portions of their Integrated Safety Analysis. 

 

Enclosed is the telephone summary for your use. The summary contains no proprietary or classified 

information. 

Enclosure: 

As stated 

Docket No. 40-9086 

cc: Mr. John J. Miller, CHP 

 International Isotopes, Inc. 

 4137 Commerce Circle 

 Idaho Falls, ID 83401 

DISTRIBUTION: 

FCSS r/f Y. Faraz, NMSS R. Wescott, NMSS D. Damon, NMSS 

ML103230080 

OFFICE AFCB AFCB AFCB 

NAME MBartlett LAllen THiltz 

DATE 12/1/10 12/1/10 1/14/11 

OFFICIAL RECORD COPY
Telephone Conference Call Summary 

International Isotopes, Inc. License Application Schedule 

Dates and Times: 1:00 pm - 2:00 pm, November 15, 2010 

 1:00 pm - 2:00 pm, November 16, 2010 

Call Participants: NRC Applicant

 Thomas Hiltz, NMSS Steve Laflin, INIS 

 Yawar Faraz, NMSS John Miller, INIS 

 Matthew Bartlett, NMSS Jim Thomas, INIS 

 Rex Wescott, NMSS Ron Green, INIS 

 Dennis Damon, NMSS et. al. 

Background

The Integrated Safety Analysis (ISA) presented by International Isotopes, Inc (INIS) uses 

passive engineered items relied on for safety (IROFS) to reduce the likelihood index for multiple 

events listed in the ISA Summary. In general this methodology is consistent with guidance in 

NUREG-1520, Revision 1, Chapter 3, Appendix A, Table A-4 (Table A-4). However, the NRC 

staff identified several instances where passive engineered IROFS did not appear to be applied 

correctly to certain accident sequences. These accident sequences involve initiating events that 

are external to the facility or the system. The examples discussed during the call involved 

seismic events and rupture of a process vessel during maintenance. 

In both of the examples discussed, the applicant sought to apply a likelihood index of 10-3, 

derived from Table A-4 to the sequence. This likelihood value cannot necessarily be applied to 

events that are initiated external to the facility or the system, since the default value assumes 

failure during designed operations. 

For natural phenomena-initiated events, the NRC staff indicated that the applicant should apply 

the guidance in the NUREG-1520, Revision 1, Chapter 3, Annex to Appendix D (Annex). INIS 

noted that the guidance for seismic events only results in a 10-4, and the ISA methodology 

requires a 10-5 for highly unlikely. INIS proposed using the building as passive engineered 

IROFS with a likelihood of 10-3, drawn from Table A-4, to reach highly unlikely. However, 

building features such as design, internal containers, emergency response, and other features 

listed in the Annex are considered by the NRC to provide an additional likelihood index of 10-1

for natural phenomena-initiated events, providing a basis for determining that the consequences 

are highly unlikely. 

A secondary example discussed, involved a passive engineered IROFS being assigned for an 

externally-initiated event, associated with a surge vessel. INIS indicated there were 

administrative procedures which would ensure the vessel was evacuated during maintenance 

and limit the type of equipment lifted over the vessel. The NRC staff noted that such 

administrative procedures were generally assigned as IROFS to comply with the performance 

requirements. 
The NRC recommended that INIS review the accident sequences, which involve initiating 

events that are external to the facility or the system; yet take credit for passive engineered 

IROFS that can fail as a result of the initiating event. 

PRINCIPAL CONTRIBUTOR

Matthew Bartlett 

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