DOCKET NO: A-98-49; II-A4-119 

WASTE CHARACTERIZATION REPORT 

TIER 1 CHANGE: 

DESKTOP EVALUATION OF THE RECALIBRATION OF THE HIGH EFFICIENCY 

NEUTRON COUNTER (HENC) NON DESTRUCTIVE ASSAY (NDA) SYSTEM AT THE 

CENTRAL CHARACTERIZATION PROJECT (CCP) 

AT IDAHO NATIONAL LABORATORY (INL) 

U.S. Environmental Protection Agency 

Office of Radiation and Indoor Air 

Center for Waste Management and Regulations 

1200 Pennsylvania Avenue, NW

Washington, DC 20460 

September 2009
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TABLE OF CONTENTS 

Section Page

1.0 Executive Summary ............................................................................................................ 1 

2.0 Purpose of Inspections ........................................................................................................ 1 

3.0 Purpose of This Report........................................................................................................ 2 

4.0 Scope of Review.................................................................................................................. 2 

5.0 Evaluation of the HENC ..................................................................................................... 2 

6.0 Findings and Concerns........................................................................................................ 6 

7.0 Summary of Results and Conclusions................................................................................. 6 
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1.0 EXECUTIVE SUMMARY 

This report approves a Tier 1 (T1) change to the contact-handled (CH) transuranic (TRU) waste 

characterization (WC) program implemented by the Central Characterization Project (CCP) at 

the Idaho National Laboratory (INL). 

In accordance with 40 CFR 194.8(b), in 2005, the U.S. Environmental Protection Agency (EPA) 

conducted a baseline inspection and approved the INL-CCP CH TRU WC program (see EPA 

Docket No. A-98-49; IIA4-59). This approval included three nondestructive assay (NDA) 

systems but excluded the INL-CCP High Efficiency Neutron Counter (HENC) because it was 

out of service. Subsequent to the baseline approval, INL-CCP returned the HENC to operation 

and EPA conducted a desktop review of the INL-CCP HENC and approved it in November 2005 

(see EPA Docket No. A-98-49; II-A4-60). 

On July 1, 2009, the Carlsbad Field Office (CBFO) requested EPA approval of a T1 change to 

the HENC in the form of a recalibration of the gamma component, due to the replacement of a 

germanium detector. This action was identified as a T1 change in the INL baseline inspection 

report and EPA conducted a T1 evaluation of the requested change using a desktop review of 

documents provided by INL-CCP. The INL-CCP HENC is a combined gamma and neutron 

measurement system, and the recalibration involved only the gamma component, there were no 

changes to the passive neutron portion. Based on EPA’s evaluation, EPA approves the gamma 

recalibration of the INL-CCP HENC for assaying CH TRU wastes in 55-gallon (208-liter) 

drums, consistent with the system’s operational ranges and limitations discussed in this report. 

No changes to the passive neutron portion of the INL-CCP HENC are approved at this time. 

2.0 PURPOSE OF INSPECTIONS 

Certain changes to the WC activities from the date of the site’s baseline inspection must be 

reported to and, if applicable, approved by EPA according to the tiering requirements set forth in 

40 CFR 194.8 regulations and incorporated in the INL Baseline Final Report cited above. 

Under the changes to 40 CFR 194.8 promulgated in the July 16, 2004, Federal Register notice, 

EPA must perform a single baseline inspection of a TRU waste generator site’s WC program 

(Vol. 69, No.136, pages 42571–42583, July 16, 2004). The purpose of EPA’s baseline 

inspection is to approve the site’s waste characterization program, based on the demonstration 

that the program’s components, with applicable conditions and limitations, can adequately 

characterize TRU wastes and comply with the regulatory requirements imposed on TRU wastes 

destined for disposal at the WIPP. 

Following EPA’s baseline approval, EPA is authorized to evaluate and approve changes, if 

necessary, to the site’s approved waste characterization program by conducting additional 

inspections under the authority of 40 CFR 194.24(h). Changes requiring EPA notification and 

approval prior to implementation (T1) and those requiring post-implementation (Tier 2 or T2) 

notification are identified in the site-specific baseline inspection reports. When evaluating 

proposed T1 changes for approval, EPA may conduct a site inspection to observe first-hand the 

implementation of the change, or can opt to conduct a “desktop” review of information provided 
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specific to a change. DOE may choose to characterize and dispose of, at risk of subsequent EPA 

disapproval, any previously-approved TRU waste using processes/procedures/equipment 

implemented as T2 changes. EPA reviews T2 changes on a quarterly basis. EPA may conduct a 

continued compliance inspections to evaluate implemented T2 changes to verify adequacy 

3.0 PURPOSE OF THIS REPORT 

This report presents the results of the EPA’s evaluation of a T1 change of the recalibration of the 

INL-CCP HENC NDA system for assaying CH TRU wastes. This report documents the basis 

for EPA’s approval decision, and explains the results of the technical evaluation of the system’s 

gamma recalibration. 

EPA’s approval decision regarding the INL-CCP HENC has been conveyed to DOE separately 

by letter. As discussed previously, EPA will also announce the decision on its website at 

www.epa.gov/radiation/WIPP, in accordance with 40 CFR 194.8(b)(3). 

4.0 SCOPE OF REVIEW

The gamma detector is one component of the INL-CCP HENC NDA system located at WMF628 at the INL. While both neutron and gamma aspects of the NDA system are typically used in 

tandem to produce results from a separate gamma assay and passive neutron assay, each 

component can be used as an independent, stand-alone, assay system for CH TRU waste. This 

T1 evaluation focuses solely on the recalibration of the gamma portion of the INL-CCP HENC; 

the passive neutron component remains unchanged from the configuration that was approved 

previously. 

The INL-CCP HENC’s recalibration was evaluated with respect to its ability to identify and 

quantify the activities of the 10 WIPP-tracked radionuclides and their uncertainty, determine a 

technically appropriate lower limit of detection (LLD), and provide technical support for the 

changes to the system’s Total Measurement Uncertainty (TMU), as appropriate. This was 

evaluated by comparing the system’s components that were changed against those that were 

approved during the baseline inspection. Upon confirming that specific components were 

unchanged, these components were not assessed during this T1 evaluation. The aspects that 

were changed by the proposed T1 change are evaluated in detail, and these are discussed in the 

Section 5 of this report. 

 

5.0 EVALUATION OF THE HENC 

EPA evaluated the documentation that INL-CCP had prepared to support the recalibration of the 

gamma detector that is part of the HENC used to characterize CH TRU wastes at INL-CCP. The 

inspection consisted of a desktop evaluation of technical records, primarily a revision of the 

calibration report. EPA had inspected this system initially at INL in 2005, and EPA deemed it 

unnecessary to conduct an on-site inspection of the HENC at INL to evaluate this change. 

However, during a subsequent continued compliance inspection that EPA conducted of the INLCCP CH WC program on September 9–10, 2009, EPA personnel did visually inspect the HENC 
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and associated records at INL. As part of the T1 evaluation, EPA assessed the following 

elements of the INL-CCP HENC’s recalibration: 

• Capability of the recalibration to perform the required analyses 

• Technical adequacy of the documents and procedures to support the HENC’s operation 

with the new calibration 

• Knowledge and understanding of the personnel involved in the INL-CCP NDA program 

During this T1 change evaluation; EPA examined the HENC’s recalibration, as documented in 

the following INL-CCP procedures and reports: 

• CCP-TP-107, Operating the CCP High Efficiency Neutron Counter Using NDA 2000, 

Revision 10, February 8, 2008 (revised since baseline) 

• CCP-TP-108, Calibrating the CCP High Efficiency Neutron Counter Using NDA 2000, 

Revision 6, April 11, 2007 (revised since baseline)

• CCP-TP-109, Data Reviewing, Validating, and Reporting Procedure for the CCP High 

Efficiency Neutron Counter Using NDA 2000, Revision 6, March 16, 2009 (revised since 

baseline) 

• CCP-INL-HENC-001b, CCP HENC Supplemental Calibration, Confirmation and 

Verification Report, Revision 0, May 21, 2009 (revised since baseline) 

• CCP-INL-HENC-002, Total Measurement Uncertainty for the CCP High Efficiency 

Neutron Counter (HENC), Revision 0, dated April 21, 2005 (not revised since baseline) 

(1) The design and operational range of the INL-CCP HENC were assessed and found to be 

unchanged from the baseline approval. 

The INL-CCP HENC is housed in a trailer that is located in Building WMF-628 at INL and had 

not been relocated since the EPA baseline inspection. The system is a combination that 

incorporates both a passive neutron counter and an integral gamma-ray spectrometer running 

NDA 2000, Version 4.0. By interviewing INL-CCP HENC personnel and reviewing the revised 

calibration report, EPA determined that no aspects of the passive neutron counter or its 

calibration were changed. 

The HENC gamma component measures photon-emitting radionuclides, and provides 

quantitative results and the relative composition of major plutonium isotopes (238Pu, 239Pu, 240Pu, 

and 241Pu), 241Am, 237Np, and 235U. In the HENC, the isotopic ratios are normally determined by 

Multi-Group Analysis (MGA) of the gamma-ray spectrum, and when plutonium isotopes are not 

detected, the software attempts to compute isotopic distributions for uranium isotopes using the 

Multi-Group Analysis Uranium (MGA-U) program. If measurement-based isotopics are not 

available, default acceptable knowledge (AK) values are used. None of these aspects of the INLCCP HENC had changed. 
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(2) The INL-CCP HENC had been recalibrated and all aspects were appropriately 

documented. 

The initial gamma and neutron calibrations of the INL-CCP HENC were performed at the 

Canberra Industries in Meriden, Connecticut, and were verified in 2004, when the system was 

located at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. These 

are documented in CCP-LLNL-NDA-001, “CCP HENC Calibration and Validation Plan and 

Report,” Revision 2, dated May 4, 2004. These calibrations were applicable to S5400 

heterogeneous debris waste packaged in 55-gallon (208-liter) drums. 

Neutron Calibration: The neutron calibration verification and confirmation were performed in 

2004, using combinations of weapons grade (WG) Pu sources and surrogate drums containing 

non-interfering and combustibles matrices. The operating range of the passive neutron system 

was stated as from the lower limit of detection (LLD) to 12 g 240Pu-effective, the equivalent of 

approximately 200 g WG Pu, or 195 g of 239Pu. The calibration was verified upon the system’s

relocation to INL, as required by DOE/WIPP-02-3122, and is documented in CCP-INL-HENC001, “CCP HENC Supplemental Calibration, Confirmation and Verification Report,” Revision 0, 

dated April 28, 2005. The HENC’s current operational parameters are essentially identical to 

those observed during the baseline approval and are not affected by the gamma recalibration, 

and, therefore, are not part of this T1 evaluation.

Gamma Calibration: A single integral gamma-ray detector is used for both quantitative and 

isotopic (relative) determination. It was recalibrated using six 241Am/152Eu line sources 

dispersed in epoxy and clad in aluminum tubes, and all calibration sources were of the 

appropriate pedigree. Even though 241Am is part of each of the calibration sources, this

radionuclide was not used for calibration. The gamma detector is fitted with a 0.81-mm thick 

cadmium filter, which attenuates the 59 kiloelectron-volt (keV) peaks, and the higher energy 

peaks are too low in transition probability (gamma abundance) to provide useful data. The 

sources were appropriately decay corrected to the measurement date, and were also corrected for 

self-absorption (using Micro Shield®). These sources were assayed in four surrogate waste 

drums, with waste matrix densities of 0.02 g/cm3

, 0.44 g/cm3, 0.66 g/cm3, and 1.62 g/cm3. 

Calibrations for energy and peak shape were performed, and the system’s responses at 121.8 keV 

and 1408 keV were compared with the original specifications; these apply to both quantitative 

and isotopic analyses. For quantitative analyses, the efficiency of the detector was measured as a 

function of gamma-ray energy between 59 and 1,408 keV, as documented in CCP-INL-HENC001b, Attachment 4. Although CCP-INL-HENC-001b presents an operating range of the gamma 

system LLD to 165 g of 239Pu, in theory, the gamma component’s calibration has no upper limit 

in terms of mass. Specifically, this means that any assay value based on measured photon 

emission within the energy range of 59 to 1,408 keV, where all operational parameters such as 

system deadtime and resolution (peak shape) are acceptable, could be considered within the 

calibration range, i.e., technically valid, irrespective of 239Pu mass. For isotopic determinations, 

the same energy range applies, although the required calibrations are energy versus channel and 

peak shape only. The gamma recalibration was acceptable and appropriately documented. 
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(3) Recalibration of the INL-CCP HENC was confirmed and documented, as required. 

The gamma calibrations were confirmed using NTP Pu sources that were combined to produce 

mass loading of 41.738 g, 106.731 g, and 160.050 g of WG Pu. With respect to matrix, the 

calibrated range for photons covers materials with a density from 0.02 to 1.62 g/ cm3

. This was 

derived using drums of four different matrices—plastic foam (0.02 g/ cm3

), soft board (0.44 g/ 

cm

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), particle board (0.66 g/ cm3), and sand (1.62 g/ cm3). These are summarized in CCP-INLHENC-001b, Table 6, and are reproduced as Table 1 below. This calibrated density range 

corresponds to three matrix types—debris (S5000), homogeneous solids (S3000 sludge), and 

soil/gravel (S4000)—and is synonymous with the system’s operational range. All calibration 

confirmation measurements were acceptable. 

Table 1. Gamma Calibration Confirmation Using WG Pu Sources

41.738 g WG Pu 106.731 g WG Pu 160.050 g WG Pu 

Run Measured Pu Run Measured Pu Run Measured Pu 

1 45.60 1 111 1 182 

2 47.60 2 110 2 180 

3 46.70 3 111 3 180 

4 46.40 4 111 4 181 

5 45.80 5 112 5 181 

6 46.50 6 112 6 179 

Average 46.50 Average 111.17 Average 180.50 

Standard 

Deviation 0.72 

Standard 

Deviation 0.75 

Standard 

Deviation 1.05 

Precision 

(%RSD) 1.55 

Precision 

(%RSD) 0.68 

Precision 

(%RSD) 0.58 

Accuracy (%R) 111.41 Accuracy (%R) 104.16 Accuracy (%R) 112.78 

(4) The efficiency of the recalibrated system was verified over the range of operation in 

terms of activity and matrix. 

Using the same 241Am/152Eu line sources that were used for recalibration and the four matrix 

drums listed above, the multi-curve efficiency of the recalibrated system was assessed. Six 

assays were performed with each matrix drum, and the results were evaluated at the six 152Eu 

energies of 121.78 keV, 344.27 keV, 778.90 keV, 964.70 keV, 1,112.06 keV, and 1,408.00 keV. 

This combination provided thorough coverage of the system’s range in terms of matrix and 

energy. All data were evaluated for accuracy (percent recovery or %R) and precision (percent 

relative standard deviation or %RSD) using a Z test statistic, as documented in CCP-INL-HENC001b, Tables 7–10. All efficiency verifications were acceptable. 

(5) The TMU of assays performed on the INL-CCP HENC that had been determined and 

documented previously was evaluated and found to have not changed. 

(6) The LLD, including the minimum detectable concentration (MDC) of the INL-CCP 

HENC that had been determined and documented previously, was evaluated and was 

found to have not changed.
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6.0 FINDINGS AND CONCERNS 

The EPA evaluation team did not identify any findings or concerns relative to the recalibration of 

the INL-CCP HENC during this T1 change evaluation. 

7.0 SUMMARY OF RESULTS AND CONCLUSIONS 

This T1 evaluation focused on the recalibration of the gamma component of the INL-CCP 

HENC. The HENC is a combined gamma and neutron measurement system, and the 

recalibration involved only the gamma component. Based on this evaluation, the EPA approves 

the recalibration of the gamma component of the INL-CCP HENC for assaying CH TRU wastes 

in 55-gallon (208-liter) drums, consistent with the system’s operational ranges and limitations 

discussed in this report and documented in CCP-INL-HENC-001b. No changes to the passive 

neutron portion of the INL-CCP HENC are approved at this time.