Information Notice No. 86-20: Low-Level Radioactive Waste Scaling Factors, 10 CFR Part 61
SSINS No: 6835
IN 86-20
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D C 20555
March 28, 1986
Information Notice No. NO 86-20: LOW-LEVEL RADIOACTIVE WASTE SCALING
FACTORS, 10 CFR PART 61
Addressees:
All nuclear power plant facilities and fuel facilities holding an operating
license (OL) or a construction permit (CP)
Purpose:
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
required
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
Discussion:
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
8603250359
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
Attachments:
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
DISCUSSION OF SCALING FACTOR METHODOLOGY PROBLEM
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
factors
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
radionuclide
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 Tuesday, March 09, 2021