ML18107A800

Tuba City Disposal Site Visit April 2018 (WM-00073)

ML18107A800
Person / Time
Site:	WM-00073
Issue date:	04/26/2018
From:	Robert Evans Division of Nuclear Materials Safety IV
To:	Division of Nuclear Materials Safety IV
R. Evans
References
Download: ML18107A800 (10)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION REGION IV 1600 E LAMAR BLVD ARLINGTON, TX 76011-4511 April 26, 2018 MEMORANDUM TO: Docket File WM-00073 THROUGH: Ray L. Kellar, PE, Chief/RA/

Fuel Cycle and Decommissioning Branch Division of Nuclear Materials Safety FROM: Robert Evans, PhD, PE, CHP, Senior Health Physicist/RA/

Fuel Cycle and Decommissioning Branch Division of Nuclear Materials Safety

SUBJECT:

NRC OBSERVATIONAL SITE VISIT AT THE TUBA CITY, ARIZONA DISPOSAL SITE 2018-001 On April 10, 2018, the U.S. Nuclear Regulatory Commission (NRC), Region IV Office, conducted an observational site visit at the U.S. Department of Energys (DOE) Tuba City Disposal Site in Tuba City, Arizona. This observational site visit was conducted in accordance with NRC guidance dated September 7, 2012 (Agencywide Documents Access and Management System [ADAMS] Accession No. ML12213A418). The purpose of the Tuba City site visit was to observe DOEs representatives conducting the annual inspection of the site in accordance with the instructions provided in the NRC-accepted Long-Term Surveillance Plan (LTSP) dated October 1996 (ADAMS Accession No. ML071300017). Enclosed to this memorandum is the NRCs trip report for this observational site visit.

In summary, the DOE representatives conducted the annual inspection in accordance with the guidance provided in the LTSP. No significant regulatory issues or safety concerns were identified during the site visit.

Docket: WM-00073

Enclosure:

NRC Trip Report WM-00073/2018-001 cc: B. Tsosie, Site Manager, DOE CONTACT: Robert Evans, DNMS/FCDB 817-200-1234

U.S. NUCLEAR REGULATORY COMMISSION REGION IV Docket: WM-00073 Report: WM-00073/2018-001 Licensee: U.S. Department of Energy Facility: Tuba City Disposal Site Location: Tuba City, Arizona Date: April 10, 2018 Inspectors: Robert Evans, PhD, PE, CHP, Senior Health Physicist Fuel Cycle and Decommissioning Branch Division of Nuclear Materials Safety Martha Poston, Health Physicist Fuel Cycle and Decommissioning Branch Division of Nuclear Materials Safety Approved by: Ray L. Kellar, PE, Chief Fuel Cycle and Decommissioning Branch Division of Nuclear Materials Safety

Attachment:

Photographs Taken at the Tuba City Disposal Site Enclosure

NRC Trip Report

1 Background

The Rare Metals Corporation and its successor, El Paso Natural Gas Company, constructed and operated a uranium mill at the Tuba City site from 1956-1966. The mill processed about 800,000 tons of ore during this 10-year period. The U.S. Department of Energy (DOE) conducted cleanup activities at the site from 1988-1990. The mill tailings, mill debris, and windblown material were placed in an onsite engineered disposal cell. Approximately 1.4 million cubic yards of contaminated material were placed in the 50-acre disposal cell. The disposal cell contains an estimated 940 curies of radium-226.

The 145-acre disposal site is held in trust by the U.S. Bureau of Indian Affairs, and the Navajo Nation retains title to the land. Pursuant to the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978, the DOE is the licensee and is responsible for the custody and long-term care of the site. The DOE and the Navajo Nation executed a Custodial Access Agreement that conveys to the Federal government title to the residual radioactive materials at the site. The agreement also ensures that the DOE has perpetual access to the site.

The DOE prepared a Long-Term Surveillance Plan (LTSP) for controlling site surveillance activities (ADAMS Accession No. ML071300017). The DOE submitted the LTSP to the U.S. Nuclear Regulatory Commission (NRC) for review and acceptance in 1996. The current LTSP is dated October 1996. The NRC subsequently accepted the disposal site as a Title I site under the general license provisions of 10 CFR 40.27.

Site operations resulted in contamination of the upper-most aquifer. Site-related contamination has been detected up to 2,500 feet downgradient from the site. Some of the groundwater contaminants that exceed the standards provided in 40 CFR Part 192 include molybdenum, nitrate, selenium, and uranium. In response to the contaminated groundwater, the DOE developed and issued a groundwater compliance action plan (GCAP) in June 1999. (The GCAP can be downloaded from the DOEs web site at https://www.lm.doe.gov/Tuba/Documents.aspx). The NRC accepted the CGAP in March 2000 (ADAMS Accession Nos. ML003685824, ML003685887).

As part of the corrective action program, the DOE established a groundwater remediation network that included 37 extraction wells. The extracted water was pumped to an onsite distillation treatment system. The original treatment system had a nominal design flow rate of 150 gallons per minute. The treated water was pumped to an infiltration trench for return to the aquifer, while the liquid wastes (brine) was transferred by gravity to a solar evaporation pond. In addition, the GCAP provides instructions for groundwater monitoring. The DOE sampled monitoring wells, extraction wells, and surface water locations. The results of the sampling events were presented in semi-annual Data Validation Packages. The DOE implemented the distillation treatment system from 2002-2014.

By letter dated November 5, 2014 (ADAMS Accession No. ML14314A858), the DOE notified the NRC that it had discontinued treatment plant operations, in part, because the pump and treat system was ineffective at achieving the desired remediation goals. By letter dated January 7, 2015 (ADAMS Accession No. ML15030A034), the DOE 2

committed to develop an action plan for interim groundwater treatment, until a long-term plan has been formulated by the DOE and accepted by the NRC.

The DOE developed an interim treatment plan while the distillation system was shut down. The April 2015 plan included operation of several extraction wells, evaporation of the extracted water in the onsite evaporation pond, and continued groundwater monitoring. (The interim treatment plan can be found on the DOEs web page at:

https://www.lm.doe.gov/Tuba/Documents.aspx). The interim treatment program consisted of three extraction pumps operating at approximately 10 gallons per minute.

The DOE submitted an updated and expanded interim treatment evaluation plan to the NRC by letter dated January 12, 2017 (ADAMS Accession No. ML17018A118). The plan included expanded discussion of field trials for enhanced evaporation, geochemical analyses, and testing of aquifer response to groundwater extraction strategies. Based in part on the information gained from interim treatment operations and the field trials, the DOE plans to update the associated groundwater model, decide which treatment option will be used to remediate the groundwater, and update the GCAP.

During the previous observational site visit, conducted in February 2016 (ADAMS Accession No. ML16092A158), the NRC inspector noted that the DOE was analyzing the groundwater samples using the list of analytes provided in the 1996 LTSP, and not the list of analytes provided in the 1999 GCAP. This inspection finding was presented to the DOE in the NRCs letter dated August 28, 2017 (ADAMS Accession No. ML17229B248).

During this observational site visit, the inspector discussed the status of the NRCs finding with DOE representatives. The DOE representatives speculated that the original intent was to sample the monitoring wells listed in the LTSP and analyze these samples using the list of analytes provided in the LTSP and sample the remainder of the monitoring wells and analyze these samples using the list of analytes provided in the GCAP. At the time of the site visit, the DOE was preparing a response letter to the NRC which is expected to clarify the required analytes for both the LTSP and GCAP monitoring wells.

2 Site Status At the time of the NRC observational site visit, the site staff had suspended interim treatment operations, to allow for field tests of aquifer response to extraction strategies.

These field tests were being conducted using the procedure described in the DOEs letter dated January 12, 2017. Site staff was operating individual extraction pumps, one at a time, to observe how the aquifer responded to intermittent operation of each pump.

Groundwater samples were collected to further understand the effectiveness of the extraction strategies. The pump tests began in November 2017 and was nearing completion at the time of the site visit. The information gained during extraction pump testing will be used to update and validate the model and may be used to identify areas where additional pumps may be necessary.

Prior to 2017, DOE staff sampled 104 wells on an annual or semi-annual basis. During 2017, the DOE installed 27 new wells to support modeling efforts and to sample areas of the aquifer where data gaps existed. As noted in the most recent Data Validation 3

Package dated February 2017 (ADAMS Accession No. ML17170A137), two of the wells were dry in 2017 and could not be sampled.

The last annual inspection of the Tuba City disposal cell was conducted on April 10, 2017 (ADAMS Accession Nos. ML18067A214, ML18067A216). The purposes of the inspection were to confirm the integrity of the visible features at the site, to identify changes in conditions that might affect conformance with the LTSP, and to determine the need, if any, for maintenance or additional inspection and monitoring. In summary, several routine maintenance needs were found but nothing was identified that was detrimental to the integrity of the disposal cell.

3 Site Observations and Findings To conduct the annual inspection, the DOE created an inspection checklist. The checklist included requirements for inspecting the fences, boundary monuments, site markers, perimeter signs, and entrance gates. Also, the DOE inspectors were required to check the integrity of the disposal cell top, side slopes, diversion ditches, area between the cell and site boundary, and outlying areas.

During the inspection, the DOE staff observed that site fences, gates, markers, monuments, and signs were in place, but a number of boundary signs had been vandalized by gunfire. Deep-rooted shrubs were identified including several saltbushs on the disposal cell cover and one tamarisk in the diversion channel. The DOE planned to eradicate these plants in the near future. Sand buildup was observed in the diversion channel, primarily from erosion of land areas adjacent to the diversion channel.

Although the DOE staff concluded that the diversion channel was still functional, the staff may attempt to remove some of the sediment from the channel. The disposal cell appeared to be in excellent condition. The erosion barrier was in place and no settlement was observed. Four settlement plates had been installed on the disposal cell, if needed to measure settlement.

The NRC inspectors measured the ambient gamma exposure rates using a hand-held survey meter (Ludlum Model 19, NRC No. 016331, calibrated to radium-226, calibration due date of 10/28/18). With a background of about 10-12 microRoentgens per hour (R/hr) in the parking lot, the gamma exposure rates on top of the tailings cell were approximately 7-8 R/hr. The exposure rates were slightly reduced due to the installation of the radon barrier and rock cover on the disposal cell. Overall, the survey results indicate that the disposal cell exposure rates were comparable to background levels.

4 Conclusions The NRC inspectors concluded that the DOE inspectors conducted the site inspection in accordance with LTSP and 10 CFR 40.27 requirements. The condition of the site was nearly identical to the condition that was reported during the previous years the DOE inspection, as documented in the 2017 annual report. The disposal cell was found to be in excellent condition. In the near future, the DOE staff planned to conduct a few minor maintenance activities, including removal of several deep-rooted plants.

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5 Meeting Summary The NRC inspectors participated in a safety meeting with the DOEs site manager and contractors prior to the site inspection. During this meeting, the participants discussed topics such as site status, inspection plan, and potential hazards.

6 Persons Contacted D. Johnson, Site Lead, Navarro Research and Engineering, Inc.

P. Lemke, Site Lead, Navarro Research and Engineering, Inc.

J. Tallbull, Senior Environmental Specialist, Navajo Nation, Division of Natural Resources J. Towers, Facility Lead, Navarro Research and Engineering, Inc.

B. Tsosie, Site Manager, DOE Office of Legacy Management E. Tyrrell, Site Lead, Navarro Research and Engineering, Inc.

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Figure 1: Site marker on top of Tuba City disposal cell Figure 2: Top of disposal cell (high point) adjacent to eastern side slope (looking south)

Attachment

Figure 3: Sediment buildup in north channel (looking northeast)

Figure 4: Meteorological monitoring station near evaporation pond 2

Figure 5: Evaporation pond with low water level due to aquifer tests in progress Figure 6: Inactive evaporation pond located west of disposal cell 3

ML18107A800 SUNSI Review ADAMS Publicly Available Non-Sensitive Keyword:

By: RJE Yes No Non-Publicly Available Sensitive NRC-002 OFFICE RIV:DNMS/FCDB FCDB C:FCDB NAME RJEvans MRPoston RLKellar SIGNATURE /RA/ /RA/ /RA/

DATE 04/23/18 04/23/18 04/26/18