United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-20: Low-Level Radioactive Waste Scaling Factors, 10 CFR Part 61

                                                           SSINS No: 6835 
                                                           IN 86-20       

                                UNITED STATES
                           WASHINGTON, D C 20555

                               March 28, 1986

                                   FACTORS, 10 CFR PART 61 


All nuclear power plant facilities and fuel facilities holding an operating 
license (OL) or a construction permit (CP) 


This notice is provided to alert licensees to a problem in the methodologies 
used to determine facility scaling factors for low-level radioactive waste 
classification This notice is intended to assist licensees in properly 
determining waste classification scaling factors 

It is expected that recipients will review the information provided for 
applicability, if appropriate, to their waste classification programs 
However, suggestions contained in this notice do not constitute NRC 
requirements,; therefore, no specific action or written response is 

Description of Circumstances: 

Recent NRC inspections have identified poor correlation between generic 
radionuclide concentration data used to classify waste and actual 
radionuclide sample data at some nuclear power plants Similarly, these 
inspections determined that some plants with multiple waste streams have 
been using one set of scaling factors to classify waste from all their waste 
streams despite significant differences (greater than a factor of 10) in 
radionuclide concentrations Such practices may lead to significant 
underestimation of certain radionuclides with direct health and safety 
consequences The practices may also lead to significant over estimates 
which limit disposal capacity and increase costs 


Any licensee who transfers radioactive waste to a land disposal facility or 
to a licensed waste collector or processor is required by 10 CFR 
20311(d)(1) to classify the waste according to 10 CFR 6155 The three 
low-level waste classes (A, B, and C) as defined in 10 CFR 
6155(a)(2)-(a)(7) describe the manner in which the classification is to be 
computed, based on concentrations of certain radionuclides within the waste 
Recognizing that some of these radionuclides may be difficult to routinely 
measure using counting equipment normally found at power reactor facilities, 
10 CFR 6155(a)(8) permits use of 


                                                            IN 86-20      
                                                            March 28, 1986 
                                                            Page 2 of 2   

indirect methods, such as scaling factors Such methods can be used to 
determine concentrations of difficult-to-measure radionuclides provided 
there is reasonable assurance that the indirect methods can be correlated 
with actual measurements 

On May 11, 1983, the NRC Division of Waste Management forwarded to all 
licensees a technical position (TP) paper on waste classification 
describing, procedures acceptable to the regulatory staff which may be used 
by licensees to determine the presence and concentration of radionuclides 
listed in 10 CFR 6155 That position paper is affirmed to represent the 
current regulatory staff position on this matter 

Since 10 CFR 61 became effective in January 1984, licensees have had varying
experiences in attempting to develop scaling factors specific to their 
facility and waste streams Initially, the staff exercised flexibility in 
determining compliance with 10 CFR 61 and permitted licensees to use generic 
scaling factors to determine waste classification, provided that the 
licensee was actively developing specific scaling factors for its facility 
and waste streams 

The attachment describes problems which have been observed by the NRC 
relative to inappropriate methodologies sometimes used by licensees on the 
application of waste stream scaling factors and provides guidance to avoid 
those problems No specific action or written response is required by this 
information notice If you have any questions about this matter, please 
contact the Regional Administrator of the appropriate regional office or 
this office 

                                   Edward L Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  A Grella, IE
                    (301) 492-7746

1   Discussion of Scaling Factor Methodology Problem
2    List of Recently Issued IE Information Notices

                                                            Attachment 1  
                                                            IN 86-20      
                                                            March 28, 1986 
                                                            Page 1 of 2   


The TP paper states that scaling factors should be developed on a facility 
and waste stream specific basis The staff also considers that in 
determining measured or inferred radionuclide concentrations, the 
concentrations are to be accurate to within a factor of 10 Scaling factors 
based on a single set of detailed sample analysis results are acceptable, 
provided that there is reasonable assurance as to the representativeness of 
the samples 

Inspections have indicated that several licensees have continued to use 
generic data, (ie, data from similar waste streams from several other 
facilities), combined with actual plant sample data to derive facility 
scaling factors This approach was taken because of a limited number of 
facility waste stream samples The difficulty arises when scaling factors 
derived from the mix of generic and facility-specific data are 
under-conservative and differ from the actual facility samples by generally 
greater than a factor of 10 Some differences as high as a factor of 10,000 
have been observed, yet some licensees have continued to use the scaling 
factors containing generic sample data Continued use of scaling factors 
which produce estimates of radionuclide concentrations that differ from the 
most recent actual measurement of that radionuclide concentration by 
generally more than a factor of 10 may constitute noncompliance with 10 CFR 
6155(a)(8) since the reasonable assurance of correlation standard cannot be 
met When discrepancies are observed, either the scaling factors need to be 
adjusted to agree with the most recent analysis of that waste stream or the 
waste stream needs to be resampled, if there is some question as to the 
validity of the sample analysis result causing the disagreement Questions 
also may arise as to the correct classification of the waste, if 
classification based on the most recent sample analysis would result in a 
higher classification from that calculated by using the generic scaling 

As a sample analysis history of facility waste streams is compiled, 
licensees may choose to determine new scaling factors based on the most 
recent sample analysis results or may combine the latest analysis with those 
previously obtained to refine the scaling factors currently in use Because 
large differences may have been caused by changes in plant operating 
conditions (eg, increased fuel leakage, crud burst, etc), the previous 
sample analysis results may not be representative of the waste stream and 
new scaling factors may need to be considered 

Inspections also have disclosed questions in licensee identification and 
determination of scaling factors for each facility waste stream Several 
licensees have used only one set of scaling factors to determine the 
classifications of wastes from all of their waste streams For some 
licensees this has resulted in underestimates of selected radionuclide 
concentrations However, the majority of licensees that use only a single 
set of scaling factors overestimate some of the radionuclide concentrations 
in the wastes, because the most conservative ratio for a radionuclide from 
the various waste stream samples is chosen as the scaling factor for that 

                                                            Attachment 1  
                                                            IN 86-20      
                                                            March 28, 1986 
                                                            Page 2 of 2   

While using scaling factors which underestimate the radionuclide 
concentrations is clearly a problem, gross overestimation of the 
concentrations also is of concern To ensure that 10 CFR 61 performance 
objectives are met, inventory restrictions may be established at a disposal 
facility for specific radionuclides such as Tc-99 or C-14 Because an 
overestimate in radionuclide inventory results in a corresponding 
overestimate in potential environmental releases, systematic gross 
overestimates in waste radionuclide concentrations may result in 
underutilization of the disposal fachlity This could result in limited 
disposal capacity and higher disposal costs Therefore, licensees  on the 
assembly and maintenance of the fittings and have enacted stricter controls 
on when maintenance can be conducted (eg, restricting maintenance on 
fittings used in hot, pressurized systems) Additionally, Westinghouse is 
developing fitting inspection guidelines and detailed acceptance criteria 

Page Last Reviewed/Updated Friday, May 22, 2015