United States Nuclear Regulatory Commission - Protecting People and the Environment

Criteria for Unique Purpose Exemption from Conversion from the Use of HEU Fuel (Generic Letter No. 86-12)


                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 

                                July 3, 1986

TO:            ALL NON-POWER REACTOR LICENSEES AUTHORIZED TO USE HEU FUEL 

SUBJECT:       CRITERIA FOR UNIQUE PURPOSE EXEMPTION FROM CONVERSION FROM 
               THE USE OF HEU FUEL (GENERIC LETTER 86-12) 

10 CFR 50.64 (51 FR 6514) provides for a "unique purpose" exemption from the
requirement to convert from the use of high enriched uranium (HEU) fuel, 
provided the licensee presents a justification that is accepted by the 
Commission. Amended 10 CFR 50.2 gives broad definitions for acceptable 
unique purposes. This letter provides more specific guidance for those 
licensees who believe they might qualify for such an exemption. 

The definition states that a unique purpose means a project, program, or 
commercial activity that cannot be reasonably accomplished without the use 
of HEU fuel, and may include one or more of the following four purposes: 

1)   A specific experiment, program, or commercial activity (typically 
     long-term) that significantly serves the U.S. national interest and 
     cannot be accomplished without the use of HEU fuel; 

2)   Reactor physics or reactor development based explicitly on the use of 
     HEU fuels; 

3)   Research projects based on neutron flux levels or spectra attainable 
     only with HEU fuel; or 

4)   A reactor core of special design that could not perform its intended 
     function without using HEU fuel. 

The definition provides guidance to licensees who believe they might qualify
for a unique purpose exemption to develop a basis for exemption that best 
fits each unique situation, and which would provide a justification that the
Commission could find acceptable. These four purposes are not necessarily 
the only ones that might form the basis for a unique purpose exemption. 
However, the following discussion relates to the four given in the 10 CFR 
50.2 definition. 

Purpose number 1 is intended to relate primarily to technical activities 
closely coupled to the national interest, which might include preeminence in
a specific field of research or assurance of a domestic supply of some 
essential product of reactor operation. This was included in the definition 
of "unique purpose" to help provide the Nuclear Regulatory Commission (NRC) 
wide latitude of discretion like the standards in 10 CFR 50.41. 



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Of the four purposes identified, it is intended that numbers (2) and (4) 
provide opportunity to perform new reactor projects whose objectives were to
learn about or develop reactor concepts for which parameters of HEU were a 
necessary component. Examples might be a unique compact reactor heat source,
a compact pulsing reactor with minimal distortion of fast neutron spectra, 
or a comparison of HEU and low enriched uranium (LEU) operating cores for 
assessing the potential for conversions of non-power reactor cores. 

Purpose number 3 is intended to provide the opportunity to continue using 
HEU fuel if converting to available LEU fuel would change neutron flux 
densities or spectra, or other essential radiation parameters, so that the 
fundamental reason for conducting the reactor-based program would be lost, 
or irreparably compromised. 

Purpose number 4 might also pertain to a non-power reactor that was designed
and is operated to take maximum advantage of the unique characteristics of 
HEU fuel and where the substitution of any available LEU fuel could not be 
made without major facility modification to accommodate such things as a 
larger core, different coolant systems, or major changes in its primary mode
of operation. An example would be a core with specific physical size limits 
that currently uses near-maximum uranium density in its fuel. 

An application for exemption from conversion from HEU fuel must be submitted
to the Director, Office of Nuclear Reactor Regulation, in accordance with 
the schedule given in the published regulation. The application should 
specify the date when acceptable LEU or medium enriched uranium (MEU) fuel 
is expected to be available, and a conversion schedule provided where 
appropriate. The NRC expects that only very few licensees will qualify for 
exemption. The following are examples of items which should be considered 
and developed in detail, as appropriate, in any application for exemption: 

     (1)  Identification and outline of the program 

     (2)  Explanation of the value of the program and any special 
          experiments to the U.S. national interests 

     (3)  Discussion of how the achievement of significant and competitive 
          results is dependent on such factors as the following: 

          (a)  neutron fluence (e.g., power level and operating schedule) 
          (b)  neutron flux density e.g., power level, core size) 
          (c)  neutron spectra 
          (d)  signal-to-noise ratio in the experimental results 
          (e)  operating and refueling schedule for the reactor 
          (f)  operating costs 
          (g)  waste management 

     (4)  Discussion of program accomplishment with available LEU fuels, and
          specification of LEU fuel characteristics required to permit 
          continuation of the programs with no significant decrement in 
          accomplishment. 


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This letter is for guidance only in interpreting 10 CFR 50.64. No response 
or action is necessary other than that required by the regulation to apply 
for a unique purpose exemption. 

Questions should be addressed to Mr. Robert E. Carter at (301) 492-8206. 


                                   Frank J. Miraglia, Director  
                                   Division of PWR Licensing-B 
Page Last Reviewed/Updated Thursday, June 27, 2013