ABSTRACT DECOMMISSIONING OF THE GEORGIA TECH RESEARCH REACTOR Steve Marske, Robert Eby, Lark Lundberg CH2M HILL Nolan Hertel, Rod Ice Georgia Institute of Technology On July 1, 1997, the Georgia Institute of Technology (Georgia Tech) administration notified the U.S. Nuclear Regulatory Commission (NRC) of their intent to decommission the Georgia Tech Research Reactor (GTRR). The GTRR is a 5-megawatt (MW) heavy-water-cooled nuclear reactor located in downtown Atlanta, Georgia. In the summer of 1999, the NRC issued a license amendment to decommission the GTRR in accordance with NRC s Regulatory Guide 1.86. In the spring of 1999, Georgia Tech and the State of Georgia contracted the services of CH2M HILL to serve as the Executive Engineer to manage the decommissioning project. Later in the summer of 1999, the IT Corporation was selected as the decommissioning contractor. IT subcontracted the waste management activities to GTS/Duratek, and the contractor mobilized on the Georgia Tech site in November 1999 to begin the dismantlement process. By February 2000, the reactor support systems, such as the primary and secondary cooling water systems, and the bismuth cooling system, were removed and packaged for off-site disposal. The reactor internals were removed in April 2000. The bioshield removal occurred in the May to November 2000 time frame. Various levels of effort were spent throughout January 2001 decontaminating concrete structures, including the Spent Fuel Storage Hole. The Final Survey report is anticipated to be submitted to the NRC in March 2001, and the final license termination is expected from the NRC August of 2001. Original Approach During the process, Georgia Tech took a unique approach to "as low as reasonably achievable" (ALARA), setting as an unrestricted release goal of 20 percent of the Regulatory Guide 1.86 contamination limits. This unique ALARA approach involves State of Georgia funding set aside to decontaminate the facility below the Regulatory Guide 1.86 limits. Because Georgia Tech is a premier institute of higher education, one of the de-commissioning objectives was to use the project as a learning tool for the institute's students. This paper will cover the project's status, describe the approach to decommission the reactor, and presents photographs and data from the work. DESCRIPTION OF THE REACTOR When in operation, the GTRR was a 5-MW thermal, heavy-water-moderated and-cooled reactor, fueled with plates of aluminum and highly enriched uranium alloy. The reactor core was approximately 2-feet in diameter and 2-feet high. When it was fully loaded, it contained 19 fuel elements, spaced 6 inches apart. Each element contained 16 fuel plates per assembly, each plate was 0.05 inches thick, 23.5 inches long, and 2.85 inches wide. Each element also contained 11.7 grams of 93 percent enriched uranium. The fuel elements were centrally located within a 6-foot diameter aluminum reactor vessel that provided a 2-foot thick D 2 O reflector that completely
surrounded the core. The reactor was controlled with four cadmium shim-safety blades and one cadmium regulating rod. The reactor vessel was mounted on a steel support structure and suspended within a thick-walled graphite cup. The graphite provided an additional 2 feet of reflector, both radially and beneath the vessel. The core and reflector system was completely enclosed by a lead and concrete biological shield (Figure 1). The bioshield was housed inside a cylindrical containment building made of steel and concrete. The containment building is approximately 82-feet in diameter and 50-feet tall. Fig. 1. Georgia Tech Research Reactor The reactor components included a heat removal system, a D 2 O storage system, a radiolytic gas recombiner system, and a ventilating system. The heat removal system was composed of a primary heavy-water system and a secondary light-water system. All components in contact with the D 2 O were fabricated of stainless steel or aluminum. Because the GTRR was intended for research application, it was equipped with a variety of experimental facilities that allowed for a wide range of investigations. Experiments that required high-intensity neutron or gamma-ray beams could be accommodated, as well as those that required a uniform thermal neutron flux throughout a large volume. The reactor was designed to produce a thermal flux of greater than 10 14 neutrons/cm 2 /sec at a power of 5 MW. Irradiation of short duration and irradiation that required rapid sample recovery could also be accomplished. In addition, the reactor face contained a thermal column and a biomedical irradiation facility, although no biomedical experiments were ever performed. The containment building has three levels. The basement contained process and ventilating equipment and space for experimental systems. The main floor provided space for the reactor bioshield and the installation of experiments. The control room was located at the level of the top
of the biological shield. During operation, access was restricted via an air lock connected to the adjoining laboratory building, along with an air lock leading to the outside. DECISION TO DECOMMISSION The reactor was licensed in 1964 with an engineered lifetime of 30 years. It operated through November 17, 1995 and generated 40,204 MW-hours (hr) of thermal energy over its lifetime. After 30 years of operations, Georgia Tech applied for a license renewal. As a part of the license renewal, the conversion of the reactor from high-enriched fuel to low-enriched fuel was planned. Because Georgia Tech was to serve as the Olympic Village and the venue for several sporting events during the summer of 1996, the Georgia Tech Administration had the fuel removed and shipped to the Savannah River Site in February 1996. In May 1997, the NRC renewed the GTRR operating license. However, shortly thereafter, the Georgia Tech Administration decided not to receive the low-enriched fuel, but to decommission the reactor instead. The administration cited several reasons for this decision: (1) approximately $2 million in renovations would be required to bring the reactor up to present-day standards; (2) under utilization of the reactor for the previous 10 years; (3) major public and political attention during the Olympics, and (4) the cost of continued operation. The decision to decommission was announced on July 1, 1997. PATH FORWARD With decommissioning in mind, Georgia Tech's intent was to remove all NRC-licensable materials from the site, terminate the license, and release the site for unrestricted use. The site release guideline for the facility was grandfathered under NRC Regulatory Guide 1.86 with guideline values of 5,000 disintegrations per minute (dpm)/100 cm 2 for total contamination and 1,000 dpm/100 cm 2 for removable contamination, instead of the new Code of Federal Regulations 10 CFR 20 Subpart E "Decommissioning Criteria." Georgia Tech selected the DECON alternative, which is the removal of all fuel assemblies, source material, radioactive fission and corrosion products, and all other radioactive and contaminated materials that have activity levels above the unrestricted release values. The Decommissioning Plan (DP) was approved by NRC on July 22, 1999, as an amendment to the existing license (Amendment 14 to Facility Operating License No. R- 97). One advantage to issuing the DP as an amendment to the license as opposed to a stand-alone document was that minor changes to the DP could then be approved by the licensee (in this case, Georgia Tech) through an established 10 CFR 50.59, "Changes, tests or experiments" safety screening and evaluation process, as opposed to sending all changes back to the NRC for its action. The project has successfully used this 10 CFR 50.59 process to change the: sequence of the decommissioning tasks means of radioactive material control method of plug storage vault removal method of graphite retaining sleeve removal method of spent fuel storage hole removal reactor bioshield demolition approach.
In addition, the process has been used to set the free release standards of tritium and Fe-55 to 200,000 dpm/100 cm 2 fixed and 10,000 dpm/100 cm 2 removable, based on previous NRC allowances for these isotopes at other decommissioning sites. In Georgia, the Georgia State Financing and Investment Commission (GSFIC) acts as the owner on construction jobs working for the using agency (Georgia Tech in this case). While waiting for approval of the DP, the GSFIC hired, through a technical competitive procurement, CH2M HILL, Inc. to serve as the Executive Engineer on the project, acting for the State and for Georgia Tech. With CH2M HILL support, the State and Georgia Tech then prequalified five potential Decontamination and Decommissioning (D&D) contractors. The IT Corporation subsequently won the project as Decommissioning Contractor (DC) on a low-price competitive bid basis. IT was awarded the contract on June 30, 1999. One of the first tasks was a joint chartering session held among Georgia Tech, the State of Georgia, the Executive Engineer, and the DC. The purpose of the chartering session was to develop vision and mission statements for the project. The vision of this project was: "A facility (reactor containment building and grounds) left in a condition that meets required safety codes and is suitable for conventional demolition and construction (i.e., unrestricted free release plus ALARA [as low as reasonably achievable])." The mission of the project team is to work together in an enjoyable teaming relationship to bring to fruition the vision while concurrently accomplishing the following: Remain a good neighbor to the surrounding communities Win the confidence of the local people and the State of Georgia Become a model for learning, as befits one of the premier locations in the country for health physics studies Avoid negative impact to ongoing operations in the remainder of the facility During the chartering session, critical success factors for the project were developed and barriers to achieving the goals were identified. Actions were taken to prevent or mitigate those barriers. Following the chartering session, the DC spent the first 60 days developing eight major project specific plans and procedures for executing the decommissioning contract. These included policies and procedures for Health and Safety, Radiation Protection, Decommissioning Work Plan, Quality Assurance, Waste Management and the Initial Survey Plan. These plans contained more than 70 individual procedures. These documents were submitted to the Executive Engineer for subsequent approval by the Georgia Tech Technical Safety Review Committee (TSRC) prior to implementation. The TSRC is a standing committee at Georgia Tech designed to oversee the technical safety of the operations during decommissioning. The TSRC is composed of six senior people: 1. the Associate Dean of Engineering 2. the Chair of the School of Mechanical Engineering 3. a past President of the Health Physics Society
4. the Georgia Tech Radiation Safety Officer 5. the Director of the Neely Nuclear Research Center 6. the Manager of Capital Projects for Georgia Tech. The DC mobilized on the site in December 1999. An initial confirmatory survey was performed as well as the packaging and transport of some miscellaneous radioactive and mixed waste from within the containment building for disposal. The primary and secondary cooling systems were removed from the containment building along with the reactor beam tube plugs. In the months of March and April, the reactor start up source, the internal safety mechanisms, the reactor cover shields and the reactor vessel were removed and shipped off site. Except for the high-activity waste, the waste was packaged and sent to GTS Duratek s facilities in Oak Ridge, Tennessee, for subsequent segregation and shipment to either Envirocare of Utah or to the Barnwell Waste Disposal Facility. The highactivity waste, including the reactor vessel, was sent directly from Georgia Tech to the Barnwell disposal site. Once the reactor vessel was removed, the graphite was then accessible for removal (Figure 2). Fig. 2. Removal of Graphite Reflector During the months of June through October, a hoe ram was used to dismantle the bioshield (Figure 3). The outer portion of the shield was uncontaminated and the inner 20 inches were treated as contaminated, due to neutron activation.
Fig. 3. Demolition of the Bioshield In October, a specialty-lifting subcontractor removed the lead tank that surrounded the reactor vessel as a single unit. The activated portions of the concrete pedestal underneath the lead tank were removed thereafter. In January 2001, further decontamination activities (such as the decontamination of the spent fuel storage hole) will be undertaken as necessary, followed by the final release surveys. The Final Survey Report is anticipated to be submitted to the NRC by the end of March 2001. A few surprises have been encountered during the project, many due to incomplete characterization prior to awarding the decommissioning contract. Since Georgia Tech was operating under a Possession Only License, there was concern that destructive coring of the reactor was not permitted within the licensed operations. Therefore, past experience was used to model the neutron activation of the concrete within the biological shield. Activation was reported as extending 3 inches into the concrete or 67 inches from the center of the reactor core. Once the DC had mobilized and initiated the confirmatory survey, core samples were drilled in the biological shield. These samples showed that the concrete was actually activated extending approximately 20 inches into the concrete (~85 inches from the core) and contained significant amounts of iron resulting in more than 150,000 pounds of additional radioactive concrete as waste for disposal. Monitoring the facility for potential tritium contamination presented difficulties. Because the reactor was a heavy-water-moderated and -cooled reactor, significant levels of tritium contamination were expected where heavy-water spills had occurred. Approximately 2,400 gallons, which equates to greater than 97 percent of the heavy water, had been previously recovered and shipped to the Savannah River Site. However, when coolant systems were opened, residual amounts of tritium-contaminated water were present in pipe elbows and low spots. In an open system, the tritium became airborne and gave the semblance of a much greater contamination problem in the facility. Elevated readings of 8 percent of a derived air concentration (DAC)-hr were observed. Increasing airflow through the ventilation system resolved this concern.
During the removal of the thermal column and graphite reflectors, some of the graphite reflector blocks read more than 300 millirem (mr)/hr on contact, with many having contact readings of between 20 and 80 mr/hr. Closer investigation revealed not only that C-14, as expected, was present, but Cobalt (Co-60) also was present at up to 300,000 pci/g concentrations. The higher dose rates were associated with steel heli-coils that had been attached to the end of the graphite stringers to use to remove the stringers during the reactor operations so samples could be introduced for irradiation activities. Discussions with other research reactor D&D personnel who had worked on the Argonne CP series of reactors revealed another common problem that resulted from metal shavings from the saw blades that were used to cut the graphite to fit around the reactor vessel. These metal shavings impregnated in the graphite while sizing the blocks and became activated during the reactor operations producing the Co-60 source. As stated, other graphite blocks were reading from 20 to 80 mr/hr. These blocks contained quantities of europium Eu-152, Eu-154 and Eu-155. In reviewing the graphite specification during reactor construction, it was noted that the specified reactor graphite grade AGOT was thermally purified to drive off impurities; however, removal of rare earth elements, such as europium, requires a halogenated chemical purification at elevated temperatures. Envirocare s waste acceptance criteria for Co-60 is 30,000 pci/g and for Europium is 20,000 pci/g. Therefore, the vast majority of the graphite (45,000+ pounds) could not be shipped to Envirocare of Utah, and instead required disposal at Barnwell at three times the cost. ALARA WORKER EXPOSURE DURING D&D Through the end of November, the cumulative dose to workers was a 10.2 person-rem. At the start of each work activity, an ALARA plan is developed and an ALARA dose allocated. An increase in exposure was observed beginning in mid-march, which correlated with the removal of the reactor vessel and activation products in the surrounding material. Most of the increase in dose corresponds to the removal of the activated graphite. Specific ALARA Georgia Tech Approach The Georgia Tech approach includes a unique aspect for decontaminating hot spots below the Regulatory Guide 1.86 limits toward achieving the institute s ALARA goal of 20 percent of the regulatory guide values. As the contractor is decontaminating the facility, if hot spots are identified, the DC may propose a change order to the Executive Engineer to further reduce the contamination even though the release limits as defined in Regulatory Guide 1.86 are met. The Executive Engineer and Georgia Tech have developed a procedure to assess the value of reduced dose compared to the cost of the decontamination effort to achieve the reduced dose. The requests may or may not be approved based on the overall dose reduction versus cost effectiveness assessment. As a result of this approach, Georgia Tech hopes to develop a cost versus dose reduction assessment, which may prove helpful to other parties interested in achieving specific ALARA goals in their decommissioning activities. To date some candidate areas have been identified for this unique ALARA approach, and these are being evaluated for possible further decontamination.
EDUCATIONAL OBJECTIVE Four video cameras were installed inside the containment building to record the decommissioning process. Tapes are being summarized to produce a documentary that can be used for other decommissioning projects, as well as for students at Georgia Tech. Output from the cameras are displayed in a war room where students, regulators, and other interested parties can come and observe the activities in real time. The war room also contains copies of the approved policies and procedures, active Radiological Work Permits (RWPs), work packages, and data from the decommissioning project, allowing students to observe project delivery techniques as a learning experience. The educational objectives are being achieved and it is clear that the project will continue to provide valuable lessons for the students. COST The DP contained a cost estimate the State of Georgia Legislature fully funded at $7.4 million. This included $500,000 for specific ALARA activities. With change orders, the estimated project cost at completion is currently $6.9 million, which is within the State s allocated budget and is expected to remain so through license termination. SUMMARY Although it took much longer to remove the bioshield than expected, the project is progressing smoothly and is meeting all the mission objectives, at this writing. As can be seen in Figure 4, the reactor vessel, concrete bioshield and lead tank have been removed. The facility should be completely decontaminated and the final survey report sent to the NRC in March 2001. Following the NRC final confirmatory survey, free release of the site and termination of the license is expected in August 2001. An assessment of cost versus dose reduction is planned for specific ALARA activities. A documentary of the D&D activities for research reactors will be published after the license is terminated.
Fig. 4. Bioshield and Lead Tank Removed