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DOE OSTI2021

Quantum many-body calculations using body-centered cubic lattices

It is often computationally advantageous to model space as a discrete set of points forming a lattice grid. This technique is particularly useful for computationally difficult problems such as quantum many-body systems. For reasons of simplicity and familiarity, nearly all quantum many-body calculations have been performed on simple cubic lattices. Since the removal of lattice artifacts is often an important concern, it would be useful to perform calculations using more than one lattice geometry. In this paper we show how to perform quantum many-body calculations using auxiliary-field Monte Carlo simulations on a three-dimensional body-centered cubic (BCC) lattice. As a benchmark test we compute the ground state energy of 33 spin-up and 33 spin-down neutrons in the unitary limit, which is an idealized limit where the interaction range is zero and scattering length is infinite. As a fraction of the free Fermi gas energy E FG , we find that the ground state energy is E 0 /E FG =0.369(2),0.371(2), using two different definitions of the finite-system energy ratio. This is in excellent agreement with recent results obtained on a cubic lattice [He et al., Phys. Rev. A 101, 063615 (2020)]. We find that the computational effort and performance on a BCC lattice is approximately the same as that for a cubic lattice with the same number of lattice points. We discuss how the lattice simulations with different geometries can be used to constrain the size of lattice artifacts in simulations of continuum quantum many-body systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Emergence of 4 H $J^π$ = 1 - resonance in contact theories

We obtain the s- and p-wave low-energy scattering parameters for n 3 H elastic scattering and the position of the 4 H J π = 1 - resonance using the pionless effective field theory at leading order. Results are extracted with three numerical techniques: confining the system in a harmonic oscillator trap, solving the Faddeev-Yakubovsky equations in configuration space, and using an effective two-body cluster approach. The renormalization of the theory for the relevant amplitudes is assessed in a cutoff-regulator range between 1 fm -1 and 10 fm -1 . Most remarkably, we find a cutoff-stable/RG-invariant resonance in the 4 H J π = 1 - system. This p-wave resonance is a universal consequence of a shallow two-body state and the introduction of a three-body s-wave scale set by the triton binding energy. The stabilization of a resonant state in a few-fermion system through pure contact interactions has a significant consequence for the powercounting of the pionless theory. Specifically, it suggests the appearance of similar resonant states also in larger nuclei, like 16-oxygen, in which the theory’s leading order does not predict stable states. Those resonances would provide a starting state to be moved to the correct physical position by the perturbative insertion of sub-leading orders, possibly resolving the discrepancy between data and contact EFT.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Chiral three-nucleon force and continuum for dripline nuclei and beyond

Three-nucleon force and continuum play important roles in reproducing the properties of atomic nuclei around driplines. Therefore it is valuable to build up a theoretical framework where both effects can be taken into account to solve the nuclear Schrödinger equation. To this end, in this letter, we have expressed the chiral three-nucleon force within the continuum Berggren representation, so that bound, resonant and continuum states can be treated on an equal footing in the complex-momentum space. To reduce the model dimension and computational cost, the three-nucleon force is truncated at the normal-ordered two-body level and limited in the sd-shell model space, with the residual three-body term being neglected. We choose neutron-rich oxygen isotopes as the test ground because they have been well studied experimentally, with the neutron dripline determined. The calculations have been carried out within the Gamow shell model. The quality of our results in reproducing the properties of oxygen isotopes around the neutron dripline shows the relevance of the interplay between three-nucleon force and the coupling to continuum states. We also analyze the role played by the chiral three-nucleon force, by dissecting the contributions of the 2π exchange, 1π exchange and contact terms.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Materials Data on MnCr(Ni2Sn)2 by Materials Project

CrMn(Ni2Sn)2 is Tungsten-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Cr is bonded in a distorted body-centered cubic geometry to eight Ni and six equivalent Sn atoms. There are six shorter (2.63 Å) and two longer (2.64 Å) Cr–Ni bond lengths. All Cr–Sn bond lengths are 3.03 Å. Mn is bonded in a distorted body-centered cubic geometry to eight Ni and six equivalent Sn atoms. There are two shorter (2.62 Å) and six longer (2.63 Å) Mn–Ni bond lengths. All Mn–Sn bond lengths are 3.04 Å. There are five inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent Cr, one Mn, and four equivalent Sn atoms. There are three shorter (2.62 Å) and one longer (2.63 Å) Ni–Sn bond lengths. In the second Ni site, Ni is bonded in a distorted body-centered cubic geometry to one Cr, three equivalent Mn, and four equivalent Sn atoms. The Ni–Cr bond length is 2.64 Å. There are one shorter (2.63 Å) and three longer (2.64 Å) Ni–Sn bond lengths. In the third Ni site, Ni is bonded in a distorted body-centered cubic geometry to one Cr, three equivalent Mn, and four equivalent Sn atoms. There are one shorter (2.63 Å) and three longer (2.64 Å) Ni–Sn bond lengths. In the fourth Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent Cr, one Mn, and four equivalent Sn atoms. There are three shorter (2.62 Å) and one longer (2.63 Å) Ni–Sn bond lengths. In the fifth Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent Cr, one Mn, and four equivalent Sn atoms. All Ni–Cr bond lengths are 2.63 Å. The Ni–Mn bond length is 2.62 Å. There are three shorter (2.62 Å) and one longer (2.63 Å) Ni–Sn bond lengths. Sn is bonded in a 8-coordinate geometry to three equivalent Cr, three equivalent Mn, and eight Ni atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on VGa2FeCo4 by Materials Project

VFeCo4Ga2 is Tungsten-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. V is bonded in a body-centered cubic geometry to eight Co atoms. There are two shorter (2.47 Å) and six longer (2.48 Å) V–Co bond lengths. Fe is bonded in a body-centered cubic geometry to eight Co atoms. There are six shorter (2.49 Å) and two longer (2.50 Å) Fe–Co bond lengths. There are six inequivalent Co sites. In the first Co site, Co is bonded in a body-centered cubic geometry to one V, three equivalent Fe, and four equivalent Ga atoms. There are three shorter (2.48 Å) and one longer (2.49 Å) Co–Ga bond lengths. In the second Co site, Co is bonded in a distorted body-centered cubic geometry to three equivalent V, one Fe, and four equivalent Ga atoms. The Co–Fe bond length is 2.50 Å. There are one shorter (2.47 Å) and three longer (2.50 Å) Co–Ga bond lengths. In the third Co site, Co is bonded in a distorted body-centered cubic geometry to three equivalent V, one Fe, and four equivalent Ga atoms. There are one shorter (2.47 Å) and three longer (2.50 Å) Co–Ga bond lengths. In the fourth Co site, Co is bonded in a body-centered cubic geometry to one V, three equivalent Fe, and four equivalent Ga atoms. All Co–Fe bond lengths are 2.49 Å. There are three shorter (2.48 Å) and one longer (2.49 Å) Co–Ga bond lengths. In the fifth Co site, Co is bonded in a distorted body-centered cubic geometry to three equivalent V, one Fe, and four equivalent Ga atoms. All Co–V bond lengths are 2.48 Å. There are one shorter (2.47 Å) and three longer (2.50 Å) Co–Ga bond lengths. In the sixth Co site, Co is bonded in a body-centered cubic geometry to one V, three equivalent Fe, and four equivalent Ga atoms. The Co–V bond length is 2.47 Å. There are three shorter (2.48 Å) and one longer (2.49 Å) Co–Ga bond lengths. Ga is bonded in a distorted body-centered cubic geometry to eight Co atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Topology optimization of multiple deformable bodies in contact with large deformations

Previous works in topology optimization of structures with contact boundary conditions have concentrated on the two-dimensional rigid obstacle problem. This is because the contact analysis of multiple three-dimensional deformable bodies with meshes that are non-matching across the contact interface requires computationally complex contact algorithms beyond the scope of previous optimization investigations. Here, our research is devoted to addressing topology design problems with multiple deformable three-dimensional components in contact using state-of-the-art contact algorithms.

42 ENGINEERING↗

DOE OSTI2020

Materials Data on HfZrCoSb2Rh by Materials Project

HfZrRhCoSb2 is half-Heusler-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Hf is bonded in a body-centered cubic geometry to three equivalent Rh, one Co, and four Sb atoms. All Hf–Rh bond lengths are 2.80 Å. The Hf–Co bond length is 2.79 Å. There are three shorter (2.80 Å) and one longer (2.82 Å) Hf–Sb bond lengths. Zr is bonded in a body-centered cubic geometry to one Rh, three equivalent Co, and four Sb atoms. The Zr–Rh bond length is 2.83 Å. All Zr–Co bond lengths are 2.80 Å. There are one shorter (2.80 Å) and three longer (2.81 Å) Zr–Sb bond lengths. Rh is bonded to three equivalent Hf and one Zr atom to form distorted RhHf3Zr tetrahedra that share corners with four equivalent SbHf3Zr tetrahedra, corners with six equivalent RhHf3Zr tetrahedra, corners with six equivalent CoHfZr3 tetrahedra, and edges with six SbHf3Zr tetrahedra. Co is bonded to one Hf and three equivalent Zr atoms to form distorted CoHfZr3 tetrahedra that share corners with four equivalent SbHfZr3 tetrahedra, corners with six equivalent RhHf3Zr tetrahedra, corners with six equivalent CoHfZr3 tetrahedra, and edges with six SbHf3Zr tetrahedra. There are two inequivalent Sb sites. In the first Sb site, Sb is bonded to three equivalent Hf and one Zr atom to form distorted SbHf3Zr tetrahedra that share corners with four equivalent RhHf3Zr tetrahedra, corners with twelve SbHf3Zr tetrahedra, edges with three equivalent RhHf3Zr tetrahedra, and edges with three equivalent CoHfZr3 tetrahedra. In the second Sb site, Sb is bonded to one Hf and three equivalent Zr atoms to form distorted SbHfZr3 tetrahedra that share corners with four equivalent CoHfZr3 tetrahedra, corners with twelve SbHf3Zr tetrahedra, edges with three equivalent RhHf3Zr tetrahedra, and edges with three equivalent CoHfZr3 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Three-dimensional continuum point cloud method for large deformation and its verification

This study presents a strong form based meshfree collocation method, which is named Continuum Point Cloud Method, to solve nonlinear field equations derived from classical mechanics for deformed bodies in three-dimensional Euclidean space. The method and its implementation are benchmarked against a nonlinear vector field using manufactured solutions. The analysis of mechanical fields firstly focuses on the study of St. Venant Kirchhoff and compressible neo-Hookean materials. Results for various initial boundary value problems are presented, including benchmark cases involving unidirectional tension and simple shear. Subsequently, the study concludes with an analysis of a displacement-controlled simulation of a compressible neo-Hookean material, specifically a bar that is pulled to 50% of its original length and rotated 90°. The pure tension case yields a 1.5% error in displacement between computed and expected values and a combined tension and torsion loading case provides further insight into material behavior under complex loading conditions. The resulting normal axial and transverse stress-strain curves are also presented. Lastly, the consistency and robustness of the proposed nonlinear numerical schemes are successfully demonstrated through various numerical experiments.

Compressible neo-Hookean materials↗

DOE OSTI2020

Materials Data on TiMn(Ni2Sn)2 by Materials Project

TiMn(Ni2Sn)2 is Tungsten-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ti is bonded in a body-centered cubic geometry to eight Ni and six equivalent Sn atoms. There are two shorter (2.58 Å) and six longer (2.62 Å) Ti–Ni bond lengths. All Ti–Sn bond lengths are 3.06 Å. Mn is bonded in a distorted body-centered cubic geometry to eight Ni and six equivalent Sn atoms. There are six shorter (2.65 Å) and two longer (2.67 Å) Mn–Ni bond lengths. All Mn–Sn bond lengths are 3.02 Å. There are four inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted body-centered cubic geometry to one Ti, three equivalent Mn, and four equivalent Sn atoms. There are three shorter (2.61 Å) and one longer (2.63 Å) Ni–Sn bond lengths. In the second Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent Ti, one Mn, and four equivalent Sn atoms. There are one shorter (2.62 Å) and three longer (2.66 Å) Ni–Sn bond lengths. In the third Ni site, Ni is bonded in a distorted body-centered cubic geometry to one Ti, three equivalent Mn, and four equivalent Sn atoms. There are three shorter (2.61 Å) and one longer (2.63 Å) Ni–Sn bond lengths. In the fourth Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent Ti, one Mn, and four equivalent Sn atoms. All Ni–Ti bond lengths are 2.62 Å. There are one shorter (2.62 Å) and three longer (2.66 Å) Ni–Sn bond lengths. Sn is bonded in a 8-coordinate geometry to three equivalent Ti, three equivalent Mn, and eight Ni atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MnV(Ni2Sn)2 by Materials Project

VMn(Ni2Sn)2 is Tungsten-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. V is bonded in a distorted body-centered cubic geometry to eight Ni and six equivalent Sn atoms. There are two shorter (2.62 Å) and six longer (2.63 Å) V–Ni bond lengths. All V–Sn bond lengths are 3.03 Å. Mn is bonded in a distorted body-centered cubic geometry to eight Ni and six equivalent Sn atoms. All Mn–Ni bond lengths are 2.63 Å. All Mn–Sn bond lengths are 3.04 Å. There are four inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted body-centered cubic geometry to one V, three equivalent Mn, and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.63 Å. In the second Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent V, one Mn, and four equivalent Sn atoms. There are one shorter (2.62 Å) and three longer (2.63 Å) Ni–Sn bond lengths. In the third Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent V, one Mn, and four equivalent Sn atoms. All Ni–V bond lengths are 2.63 Å. The Ni–Mn bond length is 2.63 Å. There are one shorter (2.62 Å) and three longer (2.63 Å) Ni–Sn bond lengths. In the fourth Ni site, Ni is bonded in a distorted body-centered cubic geometry to three equivalent V, one Mn, and four equivalent Sn atoms. All Ni–V bond lengths are 2.63 Å. There are one shorter (2.62 Å) and three longer (2.63 Å) Ni–Sn bond lengths. Sn is bonded in a 8-coordinate geometry to three equivalent V, three equivalent Mn, and eight Ni atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Towards understanding particle rigid-body motion during solid-state sintering

A quantitative understanding of particle rigid body (RB) motion that inherently accompanies grain boundary (GB) diffusion is highly desirable to understand and control the dynamic interplay between coarsening and densification during solid state sintering. In this work, by computer simulation using a multi-phase-field approach, we analyze systematically the roles played by each of these processes at different stages of the shrinkage of the internal pore in a three-particle green body as a function of particle size as well as thermodynamic and kinetic factors of interfaces. We demonstrate that particle RB translation promotes both neck growth, and pore rounding and shrinkage. Moreover, the forces acting at GBs and pulling neighboring particles towards one another dynamically evolve as particles fuse. In contrast, particle RB rotation has no contribution to pore shrinkage. The translational force acting on an individual particle varies with not only its size, but also the number and sizes of its neighboring particles.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Numerical simulation of vortex-induced vibration response of a single IEA 10-MW wind turbine blade

Three-dimensional simulation of vortex-induced vibration (VIV) of a single International Energy Agency (IEA) 10-MW reference wind turbine blade with a length of 97.325 m is performed using the ExaWind stack, an open-source suite of codes. This study aims to illustrate the spanwise VIV response characteristics and cross-validate the results with an existing commercial framework. Five near-body meshes and three time steps are selected for the convergence study. To improve computational efficiency, several VIV triggering methods are also compared to shorten the VIV development period. The ExaWind-based VIV simulation strategy for a single IEA 10-MW blade is determined. First, the modal shape is validated against published results. Then, spanwise VIV responses of four blade configurations under a fixed and varied incoming flow velocity are analyzed. Results show that the VIV response is dominated by the first edgewise (second overall) mode. Little first-mode contributions appear near the second-mode node, producing a pi phase jump, and a higher harmonics response occurs near the blade root. Rotational degrees of freedom are minor compared with translational motion. The response versus reduced velocity is analyzed, showing a two-branch behavior similar to that of VIV for a bluff cylinder. Across all tested cases, the dominant frequency remains locked to the natural frequency of the second mode with no observed desynchronization. A mild deviation is observed for the case of 90-degree pitch and 310-degree azimuth rotation near a reduced velocity of 6, which will be examined with additional cases in future work. These findings indicate that severe VIV responses can arise under specific configurations and flow conditions, thereby increasing the potential for VIV fatigue damage and requiring greater attention during operation.

17 WIND ENERGY↗

DOE OSTI2020

Computational modelling and experimental tank testing of the multi float WaveSub under regular wave forcing

A submerged wave device generates energy from the relative motion of floating bodies. In WaveSub, three floats are joined to a reactor; each connected to a spring and generator. Electricity generated damps the orbital movements of the floats. The forces are non-linear and each float interacts with the others. Tuning to the wave climate is achieved by changing the line lengths, so there is a need to understand the performance trade-offs for a large number of configurations. This requires an efficient, large displacement, multidirectional, multi-body numerical scheme. Results from a 1/25 scale wave basin experiment are described. Here, we show that a time domain linear potential flow formulation (Nemoh, WEC-Sim) can match the tank testing provided that suitably tuned drag coefficients are employed. Inviscid linear potential models can match some wave device experiments; however, additional viscous terms generally provide better accuracy. Scale experiments are also prone to mechanical friction, and we estimate friction terms to improve the correlation further. The resulting error in mean power between numerical and physical models is approximately 10%. Predicted device movement shows a good match. Overall, drag terms in time domain wave energy modelling will improve simulation accuracy in wave renewable energy device design. to understand the performance trade-offs for a large number of configurations. This requires an efficient, large displacement, multidirectional, multi-body numerical scheme. Results from a 1/25 scale wave basin experiment are described. Here, we show that a time domain linear potential flow formulation (Nemoh, WEC-Sim) can match the tank testing provided that suitably tuned drag coefficients are employed. Inviscid linear potential models can match some wave device experiments; however, additional viscous terms generally provide better accuracy. Scale experiments are also prone to mechanical friction, and we estimate friction terms to improve the correlation further. The resulting error in mean power between numerical and physical models is approximately 10%. Predicted device movement shows a good match. Overall, drag terms in time domain wave energy modelling will improve simulation accuracy in wave renewable energy device design.

16 TIDAL AND WAVE POWER↗

DOE OSTI2020

Benchmark calculations of pure neutron matter with realistic nucleon-nucleon interactions

Here, we report benchmark calculations of the energy per particle of pure neutron matter as a function of the baryon density using three independent many-body methods: Brueckner–Bethe–Goldstone, Fermi hypernetted chain/single-operator chain, and auxiliary-field diffusion Monte Carlo. Significant technical improvements are implemented in the latter two methods. The calculations are made for two distinct families of realistic coordinate-space nucleon-nucleon potentials fit to scattering data, including the standard Argonne v 18 interaction and two of its simplified versions, and four of the new Norfolk Δ -full chiral effective field theory potentials. Primarily because of the advancements in the auxiliary-field diffusion Monte Carlo, we observe good agreement among the three many-body techniques up to nuclear saturation density—the maximum difference in the energy per particle is within 1.5 MeV for all the potentials we consider. At higher densities, the divergences become more important, and are mainly driven by the Fermi hypernetted chain/single-operator calculations. We also study the connection between nucleon-nucleon scattering data and the energy per particle of pure neutron matter. Our results suggest that fitting to higher-energy nucleon-nucleon scattering helps reduce the spread of energies among the models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Search for Rare Decays of D s + to Final States π + e + e − , ρ + e + e − , π + π 0 e + e − , K + π 0 e + e − , and K S 0 π + e + e −

Using 7.33 fb − 1 of e + e − collision data collected by the BESIII detector at center-of-mass energies in the range of s = 4.128 – 4.226 GeV , we search for the rare decays D s + → h + ( h 0 ) e + e − , where h represents a kaon or pion. By requiring the e + e − invariant mass to be consistent with a ϕ ( 1020 ) , 0.98 < M ( e + e − ) < 1.04 GeV / c 2 , the decay D s + → π + ϕ , ϕ → e + e − is observed with a statistical significance of 7.8 σ , and evidence for the decay D s + → ρ + ϕ , ϕ → e + e − is found for the first time with a statistical significance of 4.4 σ . The decay branching fractions are measured to be B ( D s + → π + ϕ , ϕ → e + e − ) = ( 1.1 7 − 0.21 + 0.23 ± 0.03 ) × 10 − 5 , and B ( D s + → ρ + ϕ , ϕ → e + e − ) = ( 2.4 4 − 0.62 + 0.67 ± 0.16 ) × 10 − 5 , where the first uncertainties are statistical and the second systematic. No significant signals for the three four-body decays of D s + → π + π 0 e + e − , D s + → K + π 0 e + e − , and D s + → K S 0 π + e + e − are observed. For D s + → π + π 0 e + e − , the ϕ mass region is vetoed to minimize the long-distance effects. The 90% confidence level upper limits set on the branching fractions of these decays are in the range of ( 7.0 – 8.1 ) × 10 − 5 . Published by the American Physical Society 2024

Physics↗

DOE OSTI2023

Operational and Performance Monitoring of East Tennessee Technology Park Ponds—2023 Results

Performance and operational monitoring are regulatory requirements associated with a non–time-critical removal action for three surface water bodies at the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee: the K-1007-P1 Pond, the K-901-A Pond, and the K-720 Slough. This progress report summarizes the monitoring activities and results from fiscal year (FY) 2023. The goal of ecological enhancement of the K-1007-P1 and K-901-A Ponds is to reduce risk from polychlorinated biphenyl (PCB) contamination in fish to humans and wildlife. Lowering PCB concentrations in the water column and in the food that fish eat is expected to decrease PCB bioaccumulation in fish. Performance monitoring of the K-1007-P1 Pond focuses on annual PCB trends in water, clams, and fish. PCBs in fish also are sampled annually at the K-720 Slough. Operational monitoring ensures that ecological enhancement measures—including water quality, plant community, fish community, and wildlife actions—have been implemented as intended. Monitoring provides the information necessary to determine whether modifications are needed to attain the design end state (i.e., a heavily vegetated, clearwater pond dominated by sunfish with significantly diminished or at least downwardly trending PCB levels in fish). In FY 2023, fish removal efforts and vegetation planting primarily focused on the K-901-A Pond. These actions were implemented to help push the systems toward the desired end state. Descriptions of the various monitoring activities and preliminary 2023 results are provided in the following sections. An update on fish and plant management actions in FY 2023 is also included in this report. A summary of the more detailed information in this report will be presented as required in the upcoming Remediation Effectiveness Report.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2024

Operational and Performance Monitoring of East Tennessee Technology Park Ponds - 2024 Results

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Operational and Performance Monitoring of East Tennessee Technology Park Ponds—2025 Results

Performance and operational monitoring are regulatory requirements associated with a non–time-critical removal action for three surface water bodies at the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee (Figure 1): the K-1007-P1 Pond, the K-901-A Pond, and the K-720 Slough. This progress report summarizes the monitoring activities and results from FY 2025. The goal of ecological enhancement of the K-1007-P1 and K-901-A Ponds is to reduce risk from polychlorinated biphenyl (PCB) contamination in fish to humans and wildlife. Lowering PCB concentrations in the water column and in the food that fish eat is expected to decrease PCB bioaccumulation in fish. Performance monitoring of the K-1007-P1 Pond focuses on annual PCB trends in water, clams, and fish. PCBs in fish also are sampled annually at the K-720 Slough. Operational monitoring ensures that ecological enhancement measures—including water quality, plant community, fish community, and wildlife actions—have been implemented as intended. Monitoring provides the information necessary to determine whether modifications are needed to attain the design end state (i.e., a heavily vegetated, clearwater pond dominated by sunfish with significantly diminished or at least downwardly trending PCB levels in fish). In FY 2025, fish removal efforts and vegetation planting primarily focused on the K-901-A Pond. These actions were implemented to help push the systems toward the desired end state. Descriptions of the various monitoring activities and preliminary 2025 results are provided in the following sections. An update on fish and plant management actions in FY 2025 is also included in this report. A summary of the more detailed information in this report will be presented as required in the upcoming Remediation Effectiveness Report.

54 ENVIRONMENTAL SCIENCES↗