Field Notes: GPRS Visualizes Infrastructure of Three Mile Island

Project Managers Help Ensure Safety at Site of One of the Worst Accidents in History of U.S. Nuclear Power Industry

Field Notes: GPRS Visualizes Infrastructure of Three Mile Island

Project Managers Help Ensure Safety at Site of One of the Worst Accidents in History of U.S. Nuclear Power Industry

Three Mile Island is the site of one of the worst accidents in the history of the U.S. nuclear power industry.

It also frequently serves as Jesse Whitman’s office.

Over the past few years, Whitman and his fellow GPRS Project Managers have conducted utility locating and precision concrete scanning and imaging services all over the island located on Pennsylvania’s Susquehanna River. 

“We’ve been through every part of the facility, more or less, over the past few years,” Whitman said. “It’s pretty wild infrastructure.” 

Three Mile Island had been in operation for about five years when, at 4 a.m. on March 28, 1979, a pressure valve in the Unit 2 reactor failed to close.

 A nuclear facility is pictured.
Three Mile Island is the site of one of the worst accidents in the history of the U.S. nuclear power industry.

Irradiated cooling water drained from the open valve into adjoining buildings, and the reactor’s core began to overheat. Emergency cooling pumps automatically kicked in, and it is believed that they could have prevented the situation from escalating had they been left alone. However, human operators in the control room reportedly misread confusing and contradictory readings and shut off the emergency system.

The reactor was also shut down, but temperatures and pressure within its core continued to rise due to the residual heat released by the fission process. In a few short hours, the core had heated to over 4,000 degrees – within 1,000 degrees of meltdown temperature.

Operators were able to get the emergency pumps restarted around 8 p.m., and temperatures and pressure within the reactor slowly dropped through the night. It’s believed the reactor came within an hour of a complete meltdown, which would have exposed the surrounding community to harmful levels of radiation. While plant workers were exposed to unhealthy levels of radiation during the height of the crisis, no injuries, deaths, or direct health effects were caused by the incident.

Cleanup efforts at Unit 2 continued until 1990, but the reactor was too damaged to ever resume operation. Utah-based EnergySolutions acquired the unit from FirstEnergy in December 2020. Recently, the decades-long decommissioning project of the reactor moved into a new phase as crews were able to begin removing core debris. EnergySolutions says it will take about six years to remove these components, and then another seven or eight years to completely dismantle the structure.   

The unharmed Unit 1 reactor was shut down during the crisis, and it did not resume operation until 1985. At noon on September 20, 2019, the reactor was taken offline for the final time. Unit 1’s owner, energy company Exelon, expects decommissioning of the structure to be completed by 2079. 

GPRS has worked around both reactors, helping to find utilities and evaluate the integrity of concrete before groundbreaking and other construction activities. 

Whitman says one of his main tasks has been to locate the massive cooling pipes that used to pull water from the Susquehanna to feed the station’s cooling towers. 

“There were a couple different large crane projects where we had to mark everything, especially those giant river pipes, for this large crane to come in, because obviously they couldn’t have it collapse on them and whatnot,” he said. “Prior to that, we were doing little projects here and there, just helping with the upkeep of the plant itself just to make sure everything is running properly, doing all the utility locating for that end of it all.”

Whitman said the underground infrastructure on Three Mile Island “is one of a kind, for sure.” For security and safety reasons, he has limited access to many of the features of the island’s infrastructure, including manholes and the interiors of buildings. This means he has less information about where utilities should be buried prior to him performing a locate.

“We’re kind of going in blind when we go in to locate,” he said. “…We work at a ton of different nuclear facilities, but it’s its own kind of bear in a sense.”

Whitman relies on a combination of factors to overcome the obstacles presented by Three Mile Island. He consults existing CAD drawings, and references surface features that may indicate the presence of a nearby, buried utility. 

Then there is Whitman’s experience and training. 

A worker scans a concrete slab with ground penetrating radar.
GPRS Project Managers utilize ground penetrating radar (GPR) and other state-of-the-art technologies to visualize what's within and under concrete slabs.

Every GPRS Project Manager is required to complete the industry-leading Subsurface Investigation Methodology (SIM) program. This standard operating procedure includes specifications for underground utility locating and concrete scanning. 

SIM focuses on a three-step approach to achieve the most accurate results when performing non-destructive subsurface testing:

  • The need for experienced technicians
  • The understanding and proper utilization of applicable technology
  • The adherence to proven methodologies

SIM establishes the industry standard that the concrete scanning and utility locating industries currently lack. The use of SIM ensures site safety, and limits damage to subsurface and structural elements.

The SIM logo.
The use of SIM, or Subsurface Investigation Methodology ensures site safety and limits damage to subsurface and structural elements.

Whitman said the SIM process has played a major role in GPRS’ projects at Three Mile Island, as it provides a blueprint for how he and his fellow Project Managers should conduct utility locates and concrete scans.

“We do our SIM process, we mark everything found with the radar,” he said. “The majority of those river pipes show up really well with radar. So, a combination of our SIM process, existing drawings, working with our site contact… and then just doing our due diligence.” 

GPRS has a long history of serving the power generation, transmission, and distribution industries. 

Our suite of infrastructure visualization services includes utility locating, concrete scanning, video pipe inspections, leak detection, 3D laser scanning, and mapping & modeling. We pride ourselves on our experience and expertise. Our elite Project Managers provide an immediate and accurate report of subsurface utilities, allowing you to complete your projects safely and successfully. We help you Intelligently Visualize The Built World™ to protect your time, your budget, and most importantly, your people. 

What can we help you visualize? Schedule a service today.