RFI_SOW_Iodine-129_AMS_Analyses_1.pdf

Statement of Work for Accelerator Mass Spectrometric (AMS) Analysis for Iodine-129 in Groundwater Samples Collected at the Idaho National Laboratory (INL)

U.S. Geological Survey INL Project Office

GENERAL INFORMATION

This statement of work describes an important continuation of a long-term Iodine-129 (129I) study produced by the INL Project Office. There is an extensive time series data set of 129I activities in groundwater from the INL (Treinen and others, 2024; and references therein).

The current understanding is that the background activity of 129I is approximately 5.4 x 10-6 picocuries per liter (pCi/L) (Cecil and others, 2003) and that the main source of 129I at the INL is from historical releases at the INTEC facility.

Recent sampling efforts conducted between 2021 and 2022 (see Treinen and others, 2024) have revealed a previously under-recognized source of 129I at the Advanced Test Reactor (ATR) complex during historical wastewater releases. This discovery has prompted renewed focus on sampling efforts and the quantification of a low-level plume emanating from the ATR complex. To further monitor the migration of 129I at the INL, we propose a targeted sampling campaign that will involve:

1. Collecting data at the ATR to establish a long-term dataset from wells located near the facility.

2. Gathering data from the perched groundwater network at ATR to assess the migration potential from perched groundwater to the aquifer.

3. Collecting data from multi-level monitoring wells situated near the southern boundary of the INL to evaluate the vertical extent of 129I migration.

Ongoing groundwater sampling from wells monitored since 1990 will facilitate the characterization of 129I concentrations and support statistical evaluations of trends across as many as 15+ wells with long-term monitoring records. In addition to standard 129I activity determination in samples (measured in pCi/L), we will also explore determining native 127I/129I ratios, if applicable. Establishing a database of 127I/129I ratios will facilitate cross-matrix comparisons, such as sediment samples, to evaluate the potential contribution of 129I from atmospheric sources in future studies. We anticipate commencing the collection of 129I samples in the spring, summer, and fall of 2026, with results expected to be published in FY 2028.

WORK REQUIREMENTS AND SUPPORTING INFORMATION

To provide a spatially distributed suite of 129I concentrations in groundwater we propose determining 129I concentrations in water samples collected from 60 wells (and two field blanks for a total of 62 samples) (Table 1). The vendor laboratory shall analyze these groundwater samples by Accelerator Mass Spectrometry (AMS) methods. The concentration of 129I shall be calculated from the measured 129I/127I ratio and measurement of the concentration of iodide in the subject water sample.

USGS will provide approximately 60 samples for analyses. In addition, the vendor laboratory shall analyze six quality control samples (six replicates we collect, sequentially in-field) at their own cost, along with laboratory blanks for every ten samples. They will also document the use and results of an NIST-traceable reference standard. The AMS sensitivity for ¹²⁹I is at the attocurie (10⁻¹⁸ curies per liter) level, with a ±5% concentration uncertainty.

Acceptance criteria require 95% confidence that the analyses fall within this error tolerance.

Replicate samples will be used to assess the confidence level of the analytical results using a normalized absolute difference approach.

Sample collection is scheduled between April 1, 2026 to October 30, 2026, with collection events occurring in April (2026), June (2026), and October (2026). Samples will be shipped to the vendor lab at the end of each collection event. The vendor laboratory shall submit the analytical results to the USGS technical liaison by email within 180 days of receiving samples. The data generated from this proposal will be available to the Earth Science community at the INL for interpretation and reporting, will provide public information regarding the distribution of 129I in the aquifer, and will provide important data for future contaminant transport modeling.

Sample site details, sampling months and bottle counts can be found in Table 1 and Table 2.

PERIOD OF PERFORMANCE

The contract has an expected duration between April 1, 2026 through April 30, 2027. This performance period is needed to encompass three different sample collection periods: April 2026 (Routine Sampling), June 2026 (Westbay Sampling), October 2026 and subsequent potential reanalysis, data retrieval, correspondence with the vendor laboratory, and publication preparation.

EXPECTED DELIVERABLES

The minimum expected deliverables after the completion of analyses by the vendor will be a report in the format of an electronic data file, i.e., excel file, with all appropriate sample information including but not limited to final, reduced sample data with uncertainties reported; data for quality control samples including blanks and replicates; and sample analysis metadata. Vendor will submit report to the USGS technical liaison by email.

Table 1. Projected wells for 129I collection in 2026 Well name

CFA-1 USGS 47 USGS 113

CFA-2 USGS 51 USGS 114

CFA LF 2-10 USGS 52 USGS 115

Cross Road USGS 57 USGS 116 Highway 3 USGS 58 USGS 120 Middle 2050A zone 15 USGS 63 USGS 123 Middle 2051 zone 3 USGS 65 USGS 124 Middle 2051 zone 9 USGS 66 USGS 125 Rifle Range well USGS 67 USGS 128

RWMC M14S USGS 71 USGS 130

RWMC prod. USGS 76 USGS 131 zone 8 PW-9 USGS 77 USGS 131 zone 12 TRA Disposal USGS 82 USGS 132 zone 14 USGS 1 USGS 84 USGS 133 zone 10

USGS 11 USGS 85 USGS 136

USGS 14 USGS 87 USGS 140

USGS 20 USGS 103 zone 1 USGS 144

USGS 37 USGS 104 USGS 147

USGS 38 USGS 106

USGS 42 USGS 111 *6 QA's USGS 43 USGS 112 *10% Laboratory blanks

*2 Field blanks

Table 2. List of wells with sample month and total bottle counts Well Name Location Sample Month Count

USGS 58 ATRC April 1 USGS 65 ATRC April 2 USGS 76 ATRC April 3

CFA-1 CFA April 4 CFA LF 2-10 CFA April 5 USGS 113 INTEC April 6 USGS 116 INTEC April 7 USGS 20 INTEC April 8 USGS 38 INTEC April 9 USGS 42 INTEC April 10 USGS 51 INTEC April 11 USGS 82 INTEC April 12

USGS 85 INTEC April 13 USGS 87 INTEC April 14

USGS 111 INTEC April 15 USGS 11 Southern Boundary April 16

Cross Road Southern Boundary April 17 USGS 124 Southern Boundary April 18 USGS 144 Southern Boundary April 19 USGS 147 Southern Boundary April 20

Replicate 1 TBD April 21 Replicate 2 TBD April 22 Field Blank TBD April 23

Middle 2050A zone 15 MLMS June 1 Middle 2051 zone 3 MLMS June 2 Middle 2051 zone 9 MLMS June 3

USGS 103 zone 1 MLMS June 4 USGS 131 zone 8 MLMS June 5

USGS 131 zone 12 MLMS June 6 USGS 132 zone 14 MLMS June 7 USGS 133 zone 10 MLMS June 8

Replicate 1 TBD June 9 PW-9 (P) ATRC October 1

USGS 63 (P) ATRC October 2 USGS 66 (P) ATRC October 3 USGS 71 (P) ATRC October 4 USGS 136 ATRC October 5 USGS 140 ATRC October 6

Rifle Range well ATRC October 7 TRA Disposal ATRC October 8 RWMC M14S RWMC October 9 RWMC prod. RWMC October 10

USGS 120 RWMC October 11 Highway 3 RWMC October 12 USGS 106 RWMC October 13

CFA-2 CFA October 14 USGS 104 CFA October 15 USGS 130 CFA October 16 USGS 112 INTEC October 17 USGS 114 INTEC October 18 USGS 115 INTEC October 19 USGS 37 INTEC October 20 USGS 43 INTEC October 21

USGS 47 INTEC October 22 USGS 52 INTEC October 23 USGS 57 INTEC October 24 USGS 67 INTEC October 25 USGS 77 INTEC October 26 USGS 84 INTEC October 27

USGS 123 INTEC October 28 USGS 1 Southern Boundary October 29

USGS 14 Southern Boundary October 30 USGS 128 Southern Boundary October 31 USGS 125 Southern Boundary TBD 32

Replicate 1 TBD October 33 Replicate 2 TBD October 34 Replicate 3 TBD October 35 Field Blank TBD October 36

PLACE OF PERFORMANCE: Vendor laboratory facility

U.S. Geological Survey INL Project Office