ML20214C541

Dow Triga Research Reactor Environ Rept

ML20214C541
Person / Time
Site:	Dow Chemical Company
Issue date:	12/31/1986
From:	DOW CHEMICAL CO.
To:
Shared Package
ML20214C494	List: ML20214C492 ML20214C512 ML20214C535 ML20214C541 ML20214C549 ML20214C575
References
NUDOCS 8611210144
Download: ML20214C541 (7)

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i DOW TRIGA RESEARCH REACTOR 1

ENVIRONMENTAL REPORT i

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I 8611210144 861114 PDR ADOCK 05000264 p PDR

I 1. FACILITY The Dow TRIGA Research Reactor is located in 1602 Building of the Midland, Michigan location of The Dow Chemical Company. The reactor facility is operated by the Analytical Laborstory of the Michigan Division of The Dow Chemical Company. The reactor was installed in 1967 and was licensed to operate at a maximum steady-state power level of 100 kW. This Environmental Report is based upon an anticipated maximum power level of 300 kW.

The reactor is contained in a pool 6.5 ft diameter and 21.5 ft deep, filled with about 5000 gallons of deionized water. The pool is situated in a 20 ft by 23 ft steel frame / concrete block room constructed for the purpose of housing the reactor and associated equipment. The pool liner is constructed of welded 1/4-inch aluminum, wrapped with felt and sealed with pitch, surrounded by a 3-ft thick concrete shell inside a steel form. There is no below-grade access to the core of the reactor.

A water purification and cooling facility is located in the basement area of 1602 Building. This facility includes fHters, an ion-exchange purifier, a pump, and a heat exchanger.

I The reactor is loaded with stainless-steel-clad and aluminum-clad TRIGA fuel elements containing a uranium-zirconium hydride alloy with a uranium concentration of about 8.5% and a U-235 enrichment of less than 20%.

Supporting facilities include several laboratory rooms used for sample handling and counting of radioactive samples, a 14-MeV neutron generator facility, an irradiation facility equipped with remote manipulators and a thick lead glass window, and various functions of the Analytical Laboratory situated in 1602 Building.

There are no plans at this time for construction involving either the pool or the building housing the reactor.

2. ENVIRONMENTAL EFFECTS OF FACILITY OPERATION .

2.1. Thermal Discharges The heat exchanger is used to limit the temperature of the water in the reactor pool. The cooling water from this exchanger is discharged to the sewer serving the M. E. Pruitt Research Center of The Dow Chemical Company, from whence it is discharged to the waste water treatment plant of the City of Midland. The heat exchanger is used only during long operations of the reactor at maximum power, and the dilution by the runoff water from the Research Center results in an insignificant rise in temperature of the total outflow due to operation of the reactor.

I 2.2. Radioactive Discharges I Argon-41 is produced during operation of the reactor by the thermal neutron activation of Argon-40 in the air contained in the lazy susan and the pneumatic sample transfer assembly and in air dissolved in the pool water. Exposures to Argon-41 are based on external dose since argon is a noble gas and there is no retention of argon in the body. The inertness of the element and the short (108 minutes) half-life of the radioactive species prevent any accumulation in the environment. Evaluation of the discharges of radioactive Argon-41 (and of radioactive N-16) is based on the Safety Analysis Report for the Dow TRIGA Research Reactor (1966), modified where necessary to include the effects of operating at a power level of 300 kW.

The entry tube to the lazy susan is capped during operation of the reactor. Most of the Argon-41 formed during irradiation of the lazy susan decays in place since there is no flow of air through the irradiation facility. Small quantities may leak into the reactor room during the removal of samples after the irradiation, and be swept out the exhaust system along with any Argon-41 formed in the pool. Argon-41 formed during use of the pneumatic sample transfer system is exhausted through a fume hood in the Hot Lab.

The volume of the lazy susan within the irradiation zone is about 33 liters. When the reactor has been operated at 300 I kilowatts for more than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> the Argon-41 content is at equilibrium and the system contains about 300 millicuries of Argon-41. The dedicated ventilation system of the reactor room generates an air flow of about 1700 cfm, which gives a turnover time of about 3.5 minutes. The maximum permissible concentration for radioactive aggon in g restricted area, such as the reactor room, is 2 x 10 pCi/cm averaged over 13 consecutive 40-hour weeks (10CFR20) . This concentration would be obtained with the liberation of 270 microcuries into the room with no ventilation. The addition of half that quantity at half-life intervals (109 minutes) will mgintain gn average -

concentration at approximately 1.5 x 10 pCi/cm with no ventilation. Any delay in opening the lazy susan system after the end of an irradiation, such as the typical overnight delay following extended operation, would allow the argon to decay I within the lazy susan and would substantially reduce any j subsequent release and the consequent exposure of personnnel.

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'= The equilibrium amount of Argon-41 in the pneumatic transfer system with no flow of air is about 15 mci; the output from this system is vented to the atmosphere through a fume hood exhausting about 1000 cfm to the roof of 1602 Building. The l

roof is a restricted area; persons wishing to enter this area must secure written permission and all fume hood operations must I cease during any entry. An upper limit on the dose at the outlet of the fume hood can be estimated by assuming a continuous discharge of Argon-41 at the maximum rate. In such a case calculations indicate that the dose would be equivalent to less than the Maximum Permissible Concentration for a restricted area.

Significant quantities of radioactive Nitrogen-16 (7 second half-life) are formed in the core of the reactor. The transport time from the reactor core to the surface of the pool has been determined to be about 42 seconds when the reactor is operating at 100 kW, and when the cooling system is in operation the transport time is increased by interruption of the vertical convection currents by the discharge of treated water downward over the core of the reactor. In view of the transport time and of the short half-life the release of the radioactive nitrogen to the environment is negligible.

R.Adioactive materials produced in the reactor are segregated according to half-life. Materials with half-lives of less than 15 days are stored for periods of more than six months, then I monitored for residual radioactivity and discarded as chemical waste if no radioactivity is found; any radioactive materials found are identified and treated as long-lived radioactive I

waste. The long-lived radioactive materials, those with half-lives greater than 15 days, are stored until they can be disposed of as low-level radioactive materials through the Industrial Hygiene function of The Dow Chemical Company. In the I past these materials have been sent to licensed commercial facilities for disposal. Liquid long-lived radioactive materials were solidified before disposal. The spent. ion-exchange resin from the water purification system is dried and disposed of as long-lived low-level radioactive material.

All floor drains in the laboratory area have been sealed to minimize the possibility of loss of radioactive materials to the .

sewer system and thence to the municipal water treatment system.

2.3. ALARA All handling and release of radioactive materials and all exposure to ionizing radiation is performed using the principles I of ALARA - As Low As Reasonably Achievable. The objectives of ALARA are to minimize the exposure of individuals to ionizing radiation, to minimize the production of radioactive materials, I and to minimize the release of radioactive materials to the uncontrolled environment. Training, planning, shielding, I

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l practice sessions, distance, special tools, monitoring, and i design of experiments are used to achieve the goals of the ALARA program.

The production and use of radioactive materials is controlled by the Radiation Safety Committee (RSC) of The Dow Chemical Company. The RSC, composed of physicians, scientists, engineers and management personnel with broad backgrounds in the use of radioisotopes and radiation sources, has jurisdiction over all activities involving the use of radioactive materials and radiation emitting sources at the Midland location. The RSC is responsible for the training and certification of persons to use radioactive materials, for developing administrative procedures for properly safe-guarding against hazards associated with radiation sources and radioactive materials, for setting radiation safety policies and criteria for the use of radioactive materials, and other tasks associated with the use of radioactive materials.

All persons who use the radioactive materials produced in the reactor and who work in the reactor area are trained and certified by the RSC. Start-up reviews of new uses and projects are used to evaluate and minimize exposures to ionizing I radiation as well as chemical and other hazards. Monitoring of the re.diation exposures of personnel is conducted by a radiation safety officer of the Industrial Hygiene group under the direction of the RSC. Persons licensed to operate the reactor are trained annually in the topics of radiation safety and regulatory requirements as part of the NRC re-qualification procedure.

The effect of the training, procedures, and controls is to minimize and to document exposures of Dow workers and visitors to the effects of ionizing radiation, and to minimize the release of radioactive materials to the environment.

2.4. Radiation Control Radiation monitoring devices placed in the reactor room, in the laboratories, and upon the persons of workers are used to detect and monitor the exposures to ionizing radiation.

A continuous air monitor in the reactor room measures the amount of particulate radioactive material in that area. This monitor is equipped with an alarm level, an audible alarm indicator, a visual alarm indicator, and a computer alarm at the desk of the dispatcher at Dow Security, a post that is occupied at all times. This monitor is set to alarm at about 8 times the typical background level.

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I j An area monitor in the reactor room is set to alarm at levels exceeding 2 mR/hr, providing a visible and an audible response at the reactor control console.

A water radiation monitor is located in the water purification system, with a readout and audible alarm at the reactor control console, which responds to radioactivity in the pool water. The alarm is set at about 5 times the normal background.

Bench monitors are located in the laboratories in order to enable the experimenters to check samples and themselves for contamination.

Portable radiation monitors, including p-7 and neutron detectors, are maintained and used in the reactor room and the laboratories for checking sources and radiation fields.

Film badges and TLD finger rings are issued to persons who use radioactive materials to provide measurements of exposures.

Visitors to the facility are issued film badges.

Other portable survey instruments, pencil dosimeters, and air samplers are maintained in the emergency kits ready for use.

3. Environmental Effects of Accidents Accidents involving the reactor and experiments have been considered in the Safety Analysis Report and the Emergency Plan. The most credible accident, the release of radioactive material from a damaged fuel element, would involve the release of noble gases and halogens. The I halogens would be retained in the pool water but the noble gases would most likely be released through the ventilation system to an uncontrolled area. Calculations indicate that such a release would lead to concentrations of the order of 0.01 MPC at the nearest boundary between the Dow property and public areas.

4. Unavoidable Effects of Facility Construction and Operation.

Materials used in the construction of the reactor and the laboratories, the fission products in the fuel elements, and the low-level radioactive waste materials produced in the reactor are the major I unavoidable effects of operation and construction of the facility.

Careful segregation and disposal of the waste materials as they are generated and the proper disposal of other materials following I decommissioning of the facility will ensure that there will be no adverse effects on the environment due to operation of this facility.

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I 5. Alternatives to Construction and Operation of the Facility The facility is operated to provide information for The Dow Chemical Company, information which is necessary for the development of products, the control of production facilities, the characterization of products and waste materials, and for the conduct of business. Some of this information can be obtained through other means, although usually at an increased cost in manpower or in use of hazardous chemical processes; some of the information could be obtained through activities I at existing radiation facilities; and portions of the information could not be generated by other suitable or economic means.

6. Costs and Benefits The reactor has been in place for almost 19 years, so capital costs are limited to the requirements of replacement and upgrading of I instrumentation and equipment. Operational costs are covered by the Analytical Laboratory budget. The benefits accrue from the use of the facility as an analytical tool, as an irradiation facility, and as an isotope production facility, each serving a wide range of Dow research I and production groups. Research efforts involving the reactor, including development of analytical methods and other research projects, are generally supported by the day-by-day use of the facility in established programs.

The reactor facility is under continual scrutiny in an effort to assure that it is operated in an efficient manner as a necessary part of the total Dow research and development effort. The investment of fiscal and manpower resources in this facility is an indication of the value of the information produced at the facility.

7. Long-tern Effects on the Environment When the reactor is decommissioned the area will be returned to general I use. The radioactive fuel will be disposed of through the DOE high-level waste disposal program or will be transferred to another viable program, since the burnup of the fissile uranium is very low with this I reactor. Low-level radioactive materials will be disposed of through the normal channels, and construction materials will be treated as for any other demolition. The long-term effects on the environment are expected to be insignificant.

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