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 2009i 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.............

................................................... ................. 61

1.0 EXECUTIVE SUMMARY

This report approves a Tier 1 (T1) change to the co ntact-handled (CH) transuranic (TRU) waste characterization (WC) program implemented by the Ce ntral 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 IN L-CCP CH TRU WC program (see EPA Docket No. A-98-49; IIA4-59). This approval include d three nondestructive assay (NDA) systems but excluded the INL-CCP High Efficiency Ne utron Counter (HENC) because it was out of service. Subsequent to the baseline approva l, INL-CCP returned the HENC to operation and EPA conducted a desktop review of the INL-CCP H ENC 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) r equested 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 req uested 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 EP A’s evaluation, EPA approves the gamma recalibration of the INL-CCP HENC for assaying CH T RU wastes in 55-gallon (208-liter) drums, consistent with the system’s operational ran ges 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 acc ording to the tiering requirements set forth in 40 CFR 194.8 regulations and incorporated in the IN L Baseline Final Report cited above.

Under the changes to 40 CFR 194.8 promulgated in th e 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 character ization program, based on the demonstration that the program’s components, with applicable cond itions and limitations, can adequately characterize TRU wastes and comply with the regulat ory requirements imposed on TRU wastes destined for disposal at the WIPP.

Following EPA’s baseline approval, EPA is authorize d to evaluate and approve changes, if necessary, to the site’s approved waste characteriz ation 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 req uiring post-implementation (Tier 2 or T2) notification are identified in the site-specific ba seline 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 provided2

specific to a change. DOE may choose to characteri ze and dispose of, at risk of subsequent EPA disapproval, any previously-approved TRU waste usin g processes/procedures/equipment implemented as T2 changes. EPA reviews T2 changes on a quarterly basis. EPA may conduct a continued compliance inspections to evaluate implem ented T2 changes to verify adequacy

3.0 PURPOSE OF THIS REPORT

This report presents the results of the EPA’s evalu ation 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 resul ts of the technical evaluation of the system’s gamma recalibration.

EPA’s approval decision regarding the INL-CCP HENC h as 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 aspec ts of the NDA system are typically used in tandem to produce results from a separate gamma ass ay and passive neutron assay, each component can be used as an independent, stand-alon e, assay system for CH TRU waste. This T1 evaluation focuses solely on the recalibration o f the gamma portion of the INL-CCP HENC; the passive neutron component remains unchanged fro m 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 radi onuclides and their uncertainty, determine a technically appropriate lower limit of detection (L LD), and provide technical support for the changes to the system’s Total Measurement Uncertain ty (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 conf irming that specific components were unchanged, these components were not assessed durin g this T1 evaluation. The aspects that were changed by the proposed T1 change are evaluate d 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 pr epared to support the recalibration of the gamma detector that is part of the HENC used to char acterize CH TRU wastes at INL-CCP. The inspection consisted of a desktop evaluation of tec hnical 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 i nspection that EPA conducted of the INLCCP CH WC program on September 9–10, 2009, EPA pers onnel did visually inspect the HENC3

and associated records at INL. As part of the T1 e valuation, EPA assessed the following

elements of the INL-CCP HENC’s recalibration:

• Capability of the recalibration to perform the requ ired analyses

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

with the new calibration

• Knowledge and understanding of the personnel involv ed 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 Neutro n Counter Using NDA 2000, Revision 10, February 8, 2008 (revised since baseli ne)

• CCP-TP-108, Calibrating the CCP High Efficiency Neu tron Counter Using NDA 2000, Revision 6, April 11, 2007 (revised since baseline)

• CCP-TP-109, Data Reviewing, Validating, and Reporti ng 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 (revi sed 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 HEN C were assessed and found to be unchanged from the baseline approval.

The INL-CCP HENC is housed in a trailer that is loc ated in Building WMF-628 at INL and had not been relocated since the EPA baseline inspectio n. 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 ra dionuclides, and provides quantitative results and the relative composition o f major plutonium isotopes ( 238 Pu, 239 Pu, 240 Pu,

and 241 Pu), 241 Am, 237 Np, and 235 U. In the HENC, the isotopic ratios are normally de termined by Multi-Group Analysis (MGA) of the gamma-ray spectru m, 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 m easurement-based isotopics are not available, default acceptable knowledge (AK) values are used. None of these aspects of the INLCCP HENC had changed.4

(2) The INL-CCP HENC had been recalibrated and all aspe cts were appropriately

documented.

The initial gamma and neutron calibrations of the I NL-CCP HENC were performed at the Canberra Industries in Meriden, Connecticut, and we re 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 Calibr ation and Validation Plan and Report,” Revision 2, dated May 4, 2004. These cali brations were applicable to S5400 heterogeneous debris waste packaged in 55-gallon (2 08-liter) drums.

Neutron Calibration : The neutron calibration verification and confirma tion were performed in 2004, using combinations of weapons grade (WG) Pu s ources and surrogate drums containing non-interfering and combustibles matrices. The ope rating range of the passive neutron system was stated as from the lower limit of detection (LL D) to 12 g 240 Pu-effective, the equivalent of approximately 200 g WG Pu, or 195 g of 239 Pu. 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, Confirmati on and Verification Report,” Revision 0, dated April 28, 2005. The HENC’s current operation al 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 recalibr ated using six 241 Am/ 152 Eu line sources dispersed in epoxy and clad in aluminum tubes, and all calibration sources were of the appropriate pedigree. Even though 241 Am is part of each of the calibration sources, this radionuclide was not used for calibration. The gam ma detector is fitted with a 0.81-mm thick cadmium filter, which attenuates the 59 kiloelectro n-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 m easurement date, and were also corrected for self-absorption (using Micro Shield®). These sourc es were assayed in four surrogate waste drums, with waste matrix densities of 0.02 g/cm 3 , 0.44 g/cm 3 , 0.66 g/cm 3 , and 1.62 g/cm 3

. Calibrations for energy and peak shape were perform ed, and the system’s responses at 121.8 keV and 1408 keV were compared with the original specif ications; 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 k eV, as documented in CCP-INL-HENC001b, Attachment 4. Although CCP-INL-HENC-001b pre sents an operating range of the gamma system LLD to 165 g of 239 Pu, in theory, the gamma component’s calibration ha s no upper limit in terms of mass. Specifically, this means that an y 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 acc eptable, could be considered within the calibration range, i.e., technically valid, irrespe ctive of 239 Pu mass. For isotopic determinations, the same energy range applies, although the require d calibrations are energy versus channel and peak shape only. The gamma recalibration was accep table and appropriately documented.5

(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/ cm 3 . This was derived using drums of four different matrices—plas tic foam (0.02 g/ cm 3 ), soft board (0.44 g/

cm 3 ), particle board (0.66 g/ cm 3 ), and sand (1.62 g/ cm 3 ). These are summarized in CCP-INLHENC-001b, Table 6, and are reproduced as Table 1 b elow. This calibrated density range corresponds to three matrix types—debris (S5000), h omogeneous solids (S3000 sludge), and soil/gravel (S4000)—and is synonymous with the syst em’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 verif ied over the range of operation in terms of activity and matrix.

Using the same 241 Am/ 152 Eu line sources that were used for recalibration an d the four matrix drums listed above, the multi-curve efficiency of t he recalibrated system was assessed. Six assays were performed with each matrix drum, and th e results were evaluated at the six 152 Eu 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 (perc ent recovery or %R) and precision (percent relative standard deviation or %RSD) using a Z teststatistic, as documented in CCP-INL-HENC001b, Tables 7–10. All efficiency verifications we re acceptable.

(5) The TMU of assays performed on the INL-CCP HENC tha t had been determined and documented previously was evaluated and found to ha ve not changed.

(6) The LLD, including the minimum detectable concentra tion (MDC) of the INL-CCP HENC that had been determined and documented previo usly, was evaluated and was found to have not changed.6

6.0 FINDINGS AND CONCERNS

The EPA evaluation team did not identify any findin gs 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 mea surement system, and the recalibration involved only the gamma component. B ased 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.