ML20127E813
| ML20127E813 | |
| Person / Time | |
|---|---|
| Site: | University of Texas at Austin |
| Issue date: | 05/31/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-1135, NUDOCS 8506240665 | |
| Download: ML20127E813 (88) | |
Text
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Safety Evaluation Report related,.to the construction permit and operating license for the research' reactor at The University of Texas Docket No. 50-602 '
U.S. Nuclear Regulatory Commission Offico of Nuclear Reactor Regulation
- May 1985 p m%,
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NUREG-1135 Safety Evaluation Report related to the construction permit and operating license for the research reactor at The University of Texas Docket No. 50-602 U.S. Nuclear Regulatory Commission Office of Nuclear Reactor ReOulation May 1985 l
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ABSTRACT This Safety Evaluation Report for the application filed by The University of Texas for a. construction permit and operating license to construct and operate a TRIGA research reactor has been prepared by the Office of Nuclear Reactor Regulation of the U.S. Nuclear Regulatory Commission. The facility is owned and operated by The University of Texas and is located at the university's Balcones Research Center, about 7 miles (11.6 km) north of the main campus in Austin, Texas. The staff concludes that the TRIGA reactor facility can be con-structed and operated by The University of Texas without endangering the health and safety of the public.
o TABLE OF CONTENTS Page ABSTRACT.......................................................... iii 1 INTR 000CTION................................................. 1-1 1.1 Summary and Conclusions of Principal Safety Considerations........................................ 1-2 1.2 Reactor Description..................................... 1-3 1.3 Reactor Location........................................ 1-3 1.4 Comparison With Similar Facilities...................... 1-3
- 1. 5 Summary of Open Items................................... 1-6 1.6 Nuclear Waste Policy Act of 1982........................ 1-6 2 SITE CHARACTERISTICS......................................... 2-1 2.1 Geography............................................... 2-1 2.2 Demography.............................................. 2-1
- 2. 3 Nearby Industrial, Transportation, and Military Facilities............................................ 2-1 i
2.4 Meteorology............................................. 2-2 2.5 Geology..................... ........................... 2-2 2.6 Seismology.............................................. 2-6 2.7 Hydrology............................................... 2-6 2.8 Conclusion.............................................. 2-6 3 DESIGN OF STRUCTURES, SYSTEMS, AND COMPONENTS................ '3-1 3.1 Wind Damage............................................. 3-1 3.2 Water Damage............................................ 3-1 3.3 Seismically Induced Reactor Damage...................... 3-1 3.4 Mechanical Systems and Components....................... 3-6 3.5 Conclusion.............................................. 3-6 4 REACT 0R...................................................... 4-1
, 4.1 Reactor Facility........................................ 4-1 l
4.2 Reactor Core............................................ 4-1 4.2.1 Reflector Assembly, Grid Plates, and Core Support Structure......................... 4-1 4.2.2 Fuel Elements.................................... 4-4 4.2.3 Neutron Source and Holder........................ 4-4 l 4.2.4 Control Rods..................................... 4-4 l
4.3 Reactor Tank and Biological Shield.......................
4-4 4.4 Reactor Instrumentation................................. 4-7 4.5 Dynamic Design Evaluation............................... 4-7 4.5.1 Excess Reactivity and Shutdown Margin............ 4-9 4.5.2 Normal Operating Conditions...................... 4-9
, 4.5.3 Assessment....................................... 4-10 UT TRIGA Reactor SER v
TABLE OF CONTENTS (Continued)
Pasle 4.6 Functional Design of Reactivity Control System......... 4-10 4.6.1 Control Rod Drive Assembly...................... 4-10 4.6.2 Transient Rod Drive Assembly.................... 4-11 4.6.3 Scram-Logic Circuitry and Interlocks. . . . . . . . . . . . 4-11 4.6.4 Assessment...................................... 4-12 4.7 Operational Procedures................................. 4-13 4.8 Conclusions............................................ 4-13 5 REACTOR COOLANT AND ASSOCIATED SYSTEMS...................... 5-1 5.1 Cooling System......................................... 5-1 5.2 Primary Coolant Purification System.................... 5-1 5.3 Primary Coolant Makeup System.......................... 5-3 5.4 Conclusion............................................. 5-3 6 ENGINEERED SAFETY FEATURES.................................. 6-1 6.1 Reactor Room........................................... 6-1 6.2 Ventilation System..................................... 6-1 6.3 Conclusion............................................. 6-1 7 CONTROL AND INSTRUMENTATION SYSTEMS......................... 7-1 7.1 Evaluation and Checkout of TRIGA Control System Console....................................... 7-1 7.2 Control System......................................... 7-1 7.2.1 Control Console................................. 7-1 7.2.2 Operating Modes................................. 7-5
- 7. 3 Instrumentation System................................. 7-6 7.3.1 Nuclear Instrumentation......................... 7-6 7.3.2 Nonnuclear Instrumentation...................... 7-6 7.4 Conclusion............................................. 7-9 8 ELECTRIC POWER SYSTEM....................................... 8-1 8.1 Electrical Power System and Emergency Power............ 8-1 8.2 Conclusions............................................ 8-1 9 AUXILIARY SYSTEMS........................................... 9-1 9.1 Ventilation System..................................... 9-1 l 9.2 Fire Protection System................................. 9-1 l 9.3 Communications System.................................. 9-1 :
TABLE OF CONTENTS (Continued)
Pag!!
9.4 Compressed Air System.................................. 9-1 9.5 Air Conditioning System................................ 9-1 9.6 Fuel Handling and Storage.............................. 9-1 9.7 Conclusion............................................. 9-2 10 EXPERIMENTAL PR0 GRAMS....................................... 10-1 10.1 Reactor Experimental Facilities....................... 10-1 10.1.1 Pool Irradiations.............................. 10-1 10.1.2 Pneumatic Transfer System...................... 10-1 10.1.3 Ro ta ry S pec i me n Rac k. . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 10.1.4 Central Thimb1e................................ 10-1 10.2 Special Experimental 10-2 Facilities.......................
10.3 Beam Tube Facilities.................................. 10-2 10.4 Experimental Review................................... 10-2 10.5 Conclusion............................................ 10-2 11 RADI0 ACTIVE WASTE MANAGEMENT................................ 11-1 11.1 ALARA Commitment...................................... 11-1 11.2 Waste Generation and Handling Procedures.............. 11-1 11.2.1 Solid Waste................................... 11-1 11.2.2 Liquid Waste.................................. 11-1 11.2.3 Airborne Waste................................ 11-2 11.3 Conclusion............................................ 11-2 12 RADIATION PROTECTION PR0 GRAM................................ 12-1 12.1 ALARA Commitment...................................... 12-1 l
12.2 Health Physics Program................................ 12-1 l 12.2.1 Health Physics Staff.......................... 12-1 l 12.2.2 Procedures.................................... 12-1 12.2.3 Instrumentation............................... 12-1 l
12.2.4 Training...................................... 12-2 12.3 Radiation Sources..................................... 12-2
. 12.3.1 Reactor....................................... 12-2 12.3.2 Extraneous Sources............................ 12-2 12.4 Routine Monitoring.................................... 12-3 12.4.1 Fixed-Position Monitors....................... 12-3 12.4.2 Experimental Support.......................... 12-3 l
TABLE OF CONTENTS (Continued)
Pag 12.5 Occupational Radiation Exposures...................... 12-3 12.5.1 Personnel Monitoring Program.................. 12-3 12.5.2 Personnel Exposures........................... 12-3 12.6 Effluent Monitoring................................... 12-3 12.6.1 Airborne Effluents............................ 12-3 12.6.2 Liquid Effluents.............................. 12-4 12.7 Environmental Monitoring.............................. 12-4 12.8 Potential Dose Assessments............................ 12-4 12.9 Conclusions........................................... 12-4 13 CONDUCT OF OPERATIONS....................................... 13-1 13.1 Overall Organization.................................. 13-1 13.1.1 Radiation Safety Committee.................... 13-1 13.1.2 Radiation Safety 0fficer...................... 13-1 13.1.3 Reactor Operation Committee................... 13-1 13.2 Training.............................................. 13-1 13.3 Emergency Planning.................................... 13-1 13.4 Reactor Startup P1an.................................. 13-3 13.5 Operational Review and Audits......................... 13-3 13.6 Quality Assurance P1an................................ 13-3 13.7 Physical Security Plan................................ 13-3 13.8 Review of Operational History......................... 13-4 13.9 Conclusion............................................ 13-4 14 ACCIDENT ANALYSIS........................................... 14-1 14.1 Fuel Handling Accident................................ 14-1 14.1.1 Scenario...................................... 14-2 14.1.2 Assessment.................................... 14-3 14.2 Rapid Insertion of Reactivity......................... 14-3 l 14.2.1 Scenario...................................... 14-4 14.2.2 Assessment.................................... 14-4 14.3 Loss of Coolant....................................... 14-5 14.4 Misplaced Experiments................................. 14-6 14.5 Mechanical Rearrangement of the Fue1.................. 14-6 14.6 Effects of Fuel Aging................................. 14-7 14.7 Conclusion............................................ 14-8 15 TECHNICAL SPECIFICATIONS.................................... 15-1 UT TRIGA Reactor SER viii
TABLE OF CONTENTS (Continued)
P_a21 16 FINANCIAL QUALIFICATIONS.................................... 16-1 17 OTHER LICENSE CONSIDERATIONS................................ 17-1 17.1 Prior Utilization of Reactor Components............... 17-1 17.2 Conclusions........................................... 17-1 18 CONCLUSIONS................................................. 18-1 19 REFERENCES.................................................. 19-1 LIST OF FIGURES 1.1 City of Austin............................................ 1-4 1.2 Balcones Research Center.................................. 1-5 2.1 Texas Tornado Frequencies................................. 2-3
- 2. 2 Austin Wind Rose Data..................................... 2-4 2.3 Balcones Fault Zone....................................... 2-5 2.4 Uniform Building Code Zone Map of the U.S................. 2-7 2.5 Texas Earthquake Data..................................... 2-8 3.1 Nuclear Engineering Teaching Laboratory (NET L) Bui ldi ng Fi rst Leve1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3.2 NETL Building Second Level................................ 3-3 3.3 NETL Building Third Level................................. 3-4 3.4 Cross Section of Reactor Facility Area.................... 3-5 4.1 Typical Mark II TRIGA Reactor............................. 4-2 4.2 TRIGA Stainless-Steel-Clad Fuel Element With End Fittings....................................... 4-5 4.3 Core Arrangement.......................................... 4-6 4.4 Typical Mark II TRIGA Reactor With Thermal Column.................................................. 4-8 5.1 Water and Coolant Puri fication Systems. . . . . . . . . . . . . . . . . . . . 5-2 7.1 Logic Diagram for Control System.......................... 7-2 7.2 Layout of the Reactor Control Console..................... 7-3 7.3 Console Control Panels.................................... 7-4 7.4 Neutron Channel Operating Ranges.......................... 7-7 13.1 Organizational Structure.................................. 13-2 LIST OF TABLES 4.1 Principal Design Parameters............................... 4-3 7.1 Minimum Reactor Safety System Channels.................... 7-8 UT TRIGA Reactor SER ix
TABLE OF CONTENTS (Continued)
Page 7.2 Console Alarm Settings....... ................... ........ 7-8 12.1 Humber of Individuals in Exposure Interval.... ..... .... 12-5 14.1 Doses Resulting From Postulated Fuel Handling Accident............... . ....... .... ..... 14-3 i
1 INTRODUCTION The University of Texas (UT/pplicant) submitted an application to the U.S.
Nuclear Regulatory Commission (EC/ staff) for a construction permit and operat-ing license for its proposed TRIGA research reactor by letter (with supporting documentation) dated November 1984.
The UT currently operates a TRIGA Mark I research reactor at its main campus.
This reactor was first licensed to operate in 1963 at a power level of 1 kW thermal. In 1968 the license was amended to permit operation at power levels up to and including 250 kWt. The UT plans to construct a new TRIGA Mark II research reactor in a new facility to be located at the university's Balcones Research Center, about 7 mi (11.6 km) north of the main campus in Austin, Tex-as. The applicant plans to dismantle and decommission the existing reactor facility when the new facility is completed.
The staff safety review with respect to issuing a construction permit and oper-ating license to The University of Texas has been based on the information con-tained in the application and supporting supplements, plus responses to requests for additional information. The application includes t.he Safety Anal-ysis Report, Environmental Report, Technical Specifications, Reactor Operator Requalification Program, Physical Security Plan, and an Emergency Plan. This material is available for review at the Connission's Public Document Room at 1717 H Street, N.W., Washington, D.C. The Physical Security Plan, dated November 9, 1984, and submitted on December 17, 1984, is protected from public disclosure under 10 CFR 2.790(d)(1) and 10 CFR 9.5(a)(4).
The purpose of this Safety Evaluation Report (SER) is to summarize the results of the safety review of the proposed UT TRIGA reactor and to delineate the scope of the technical details considered in evaluating the radiological safety aspects of construction and operation. This SER will serve as the basis for the construction permit and the license for operation of the UT TRIGA reactor facility at nonpulsing thermal power levels up to and including 1.1 MW and pulsed operation with step reactivity insertions up to 2.2% Ak/k. The appli-cant requests the possession and use of up to 5,800 g of contained 23s0 for use in connection with reactor operation. The facility was reviewed against the requirements of 10 CFR 20, 30, 50, 51, 55, 70, and 73; applicable regulatory guides (Division 2, Research and Test Reactors); and appropriate accepted in-dustry standards (American National Standards Institute /American Nuclear Socie-ty (ANSI /ANS 15 series)). Because there are no specific accident-related regulations for research reactors, the staff has at times compared calculated dose values with related standards in 10 CFR 20, the standards for protection against radiation, both for employees and the public.
This SER was prepared by Angela T. Chu, Project Manager, Division of Licensing, Office of Nuclear Reactor Regulation, Nuclear Regulatory Commission. Major contributors to the technical review include the project manager and C. Linder, A. Crawford, and J. Elder of Los Alamos National Laboratory (LANL) under con-tract to the NRC.
1.1 Summary and Conclusions of Principal Safety Considerations The staff evaluation considered the information submitted by the applicant, past operating history of the original UT reactor in annual reports submitted to the Commission by the applicant, reports by the Commission's Region IV of-fice, and onsite observations. In addition, as part of the licensing review, the staff obtained laboratory studies and analyses of several accidents postu-lated for the TRIGA-type reactor.
The principal matters reviewed and the conclusions reached for the UT TRIGA reactor were the following:
(1) The design and performance of the reactor structure and systems and compo-nents important to safety during normal operation are inherently safe, and safe operation can reasonably be expected.
(2) The expected consequences of a broad spectrum of postulated credible acci-dents have been considered, emphasizing those likely to cause loss of in-tegrity of fuel element cladding. The staff performed conservative analyses of serious credible accidents and determined that the calculated potential radiation doses outside of the reactor room are not likely to exceed 10 CFR 20 guidelines in unrestricted areas.
(3) The applicant's proposed management organization, conduct of training and research activities, and security measures are adequate to ensure safe operation of the facility and protection of special nuclear material.
(4) The facility is designed and will be operated in such a manner as to en-sure that releases of radioactive wastes are within the limits of the Com-mission's regulations and are as low as reasonably achievable (ALARA).
(5) Ihe applicant's preliminary version of Technical Specifications are gen-erally acceptable. The final Technical Specifications will be reviewed and approved by the staff before an operatoring license is issued. The results of the review will be addressed in a supplement to this SER.
(6) The financial data and information provided by the applicant are such that the staff has determined that the applicant has sufficient revenues to cover construction and operating costs and to ensure protection of the public from radiation exposures when operations are terminated.
(7) The applicant's physical security plan for providing for the physical pro-tection of the facility and its special nuclear material was submitted and is under review by the staff. All remaining open items will be resolved before an operating license is issued and will be addressed in a supple-ment to this SER.
(8) The applicant's procedures for training its reactor operators and the plan for operator requalification are adequate; they give reasonable assurance that the reactor facility will be operated competently.
(9) The applicant's quality assurance (QA) program for the design, construc-tion, and operation phases of the reactor facility complies with the regu-lations (10 CFR 50.34) with regard to the overall QA program for research reactors.
1-2
(10) The applicant has submitted an Emergency Plan in accordance with NRC re-quirements. The staff has completed its review of the plan. Two open items remain to be completed before actual implementation of the plan and will be addressed in a supplement to this SER at the operating license stage.
(11) The staff has reasonable assurance that the applicant will construct the facility in accordance with the design and proposed construction plans without any significant health and safety or environmental impact.
1.2 Reactor Description The UT reactor is a heterogeneous, pool-type TRIGA Mark II reactor which oper-ates at nonpulsing power levels up to and including 1.1 MW and at pulse-mode with maximum step reactivity insertion of 2.2% ck/k. The reactor core is cooled by natural convection of light water, moderated by zirconium hydride and light water, and reflected by graphite and light water. The core is located at 2 ft above the bottom of an aluminum tank that rests on a concrete pad and is surrounded by a concrete shield structure above ground.
The reactor core consists of 86 cylindrical stainless-steel-clad uranium zirco-nium hydride (UZrHx ) fuel elements enriched to less than 20% 2ssU. The fuel elements are assembled in concentric rings and are held by upper and lower alu-minum grid plates. Reactor experimental facilities include a rotary specimen rack, a pneumatic transfer system, a central thimble, and five beam tubes.
The UT TRIGA reactor facility has a new computerized control and instrumenta-tion system developed by General Atomic Technologies (GA). All four of the control rods are new. Three of the control rod drive mechanisms are inherited from the old UT reactor but have been totally reconditioned by GA. The fourth control rod drive mechanism has been purchased from GA.
The new UT TRIGA reactor facility inherits the reactor assembly bridge with all 92 fuel elements from the original UT reactor facility. An additional 59 fuel elements of the same type have been acquired from the Northrop Cooperation re-actor. Fuel elements that are not in use are stored in the racks in the reac-tor tank and in the storage wells located near the reactor tank.
I
- 1. 3 Reactor Location l
The UT TRIGA reactor facility will be situated on the east tract of the Balcones Research Center which is located about 7 mi (11.6 km) north of the UT main campus, in the city of Austin, Travis County, Texas (see Figure 1.1).
l The reactor site (see Figure 1.2) was operated as a magnesium manufacturing plant by the Federal Government before the university's leasing in 1947 and eventual acquisition.
I 1.4 Comparison With Similar Facilities The reactor core is similar to that of most of the 58 TRIGA reactors operating
- throughout the world, 27 of which are in the United States, and 24 of these are l licensed by the NRC and the other 3 by the Department of Energy (00E). The instruments and controls are typical of TRIGA reactors and most of the other research reactors licensed by the NRC.
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1.5 Summary of Open Items As a result of the s'.aff review of the safety aspects of the UT application, a number of items remain outstanding at the time of issuance of this report. The identified open items (and the sections of the report in which they are addressed) ;
are as follows:
- 1. Emergency Plan (Section 13.3)
- 2. Physical Security Plan (Section 13.7)
- 3. Technical Specifications (Section 15)
These open items do not impact the issuance of a construction permit for the facility. The staff review of these open items will be completed before a decision is made on issuing an operating license and will be addressed in a supplement to this report.
i 1.6 Nuclear Waste Policy Act of 1982 Section 302(b)(1)(B) of the Nuclear' Waste Policy Act of 1982 provides that the NRC may require, as a precondition to issuing or renewing an operating license for a research or test reactor, that the applicant shall have entered into an agreement with the Department of Energy (00E) for the disposal of high-level radioactive wastes and spent nuclear fuel. 00E (R. L. Morgan) has informed the NRC (H. Denton) by letter dated May 3, 1983, that it has determined that uni-versities and other government agencies operating nonpower reactors have en-tered into contracts with 00E that provide that DOE retain title to the fuel and is obligated to take the spent fuel and/or high-level waste for storage or reprocessing. Because The University of Texas has entered into such a contract with DOE the applicable requirements of the Waste Policy Act of 1982 have been satisfied for the UT reactor.
2 SITE CHARACTERISTICS 2.1 Geography The facility containing the TRIGA reactor will be situated on the east tract of the Balcones Research Center, which is located in the city of Austin, Texas in northern Travis County. The Balcones Research Center east and west tracts of land contain a total area of 0.72 mi2 (1.87 km2 ), with 0.357 mi2 (0.93 km2 ) in the east tract and 0.361 mi2 (0.094 km 2
) in the west tract of land. The site is located about 4.5 mi (7.4 km) from where the Colorado River crosses the transi-tion line between hill country and rolling plains. Elevations within the city vary from 393 ft (120 m) to 900 f t (275 m) above sea level. Most areas adjacent to the research center are developed for mixed commercial and industrial activi-ties. Major activities in the area are from the UT main campus at Austin and the State of Texas government and the business district of the city of Austin.
2.2 Demography The population of Austin is about 345,000 with the Travis County population esti-mated at 420,000, and the Austin Standard Metropolitan Statistical Area population at 536,000 (1980 census). Population densities in Travis County range from 6.4 persons per 10,758 ft2 (1000 m2 ) encompassing the main university campus to less than 12 per 1076 ft2 (100 m2 ) in growth areas north of the Balcones Research Center site, and about 1.2 to 2.0 persons per 10,758 ft2 (1000 m 2
) in the area adjacent to the site. Residential areas are located beyond adjoining areas around the Balcones Research Center. These residential areas are located about 0.81 to 1.3 mi (1.3 to 2.1 km) from the reactor facility site.
Approximately 800 persons were involved in activities on the east tract of the Balcones Research Center in the early 1980's. The projected activities at the site will increase to about 1000 persons by the late 1980's. On the west tract, the Microelectronics and Computer Technology Corporation is expected to employ 1000 persons by the end of 1985. Facilities north of the research center oper-ated by International Business Machines Corporation are expected to employ 6500 persons by the end of 1985.
2.3 Nearby Industrial, Transportation, and Military Facilities The area has substantial light industry but no heavy industry. Mixed commercial and industrial areas south and east of the Balcones Research Center are bounded by highway US 183, highway FM 1325, and the Texas New Orleans Railroad to the east. Much of the remaining area to the west of the research center is bounded by highway US 183 and the Missouri Pacific Railroad. Distance from the reactor site to the nearest railroad is about 1148 ft (350 m).
Immediately north of the Balcones Research Center east tract is a 0.884 mi2 (2.3 km2 ) complex operated by IBM Corporation. Adjacent to the site for the TRIGA reactor are the Center for Energy Studies, Center for Electromechanics, Bureau of Economic Geology, and Water Resources Center. The Austin business district is 8.06 mi (13.0 km) to the south-southwest of the research center.
I 8
j Distances to air traffic landing facilities in the area are 3.8 mi (6.2 km) for j private aircraft, 6.0 mi (9.7 km) for commercial aircraft, and 12.9 mi (20.8 km)
! for military aircraft.
! 2.4 Meteorology j The climate (Local Climatological Data, 1982) of Austin is humid subtropical with hot summers. Winters are mild with below freezing temperatures occurring
' on an average of less than 25 days each year. Daytime temperatures in summer i are hot, but summer nights are usually pleasant with the average daily minimum i in the low seventies. Rather strong northerly winds accompanied by sharp drops j in temperature occasionally occur during the winter months in connection with
! cold fronts. These cold spells are usually of short duration, rarely lasting j more than 2 days.
I Precipitation is fairly evenly distributed throughout the year. Most of the winter precipitation occurs as light rain. The amount of snowfall is insigni-
! ficant.
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- Prevailing winds are southerly throughout the year. Northerly winds accompany-ing the colder air masses in winter soon shift to southerly as these air masses move out over the Gulf of Mexico.
I Destructive winds and damaging hailstorms are infrequent. On rare occasions,
, dissipating tropical storms affect the city with strong winds and heavy rains.
Tornadic activity at the site is roughly one event per year per 1000 mi2 i (2600 km 2 ) op 4 x lo_s per year for an area of 333 ft2 (30.8 m2 , which is roughly l equal to the general site area. The frequency of tornado type activity is illus-trated in Figure 2.1 and the typical Austin wind data are presented in Figure
! 2.2.
1 2.5 Geology Travis County, within which the site is located, is spanned by two distinct i physiographic terrains that trend diagonally southwest to northeast. The north-western terrain is part of the Edwards Plateau, which is a highly dissected ,
i plateau with hilltops rising as much as 490 ft (150 m) above drainage bottoms.
i The southeastern terrain is within the Gulf Coastal Plain physiographic province and is characterized by the topography of a gently rolling prairie. The two landforms are separated by a scarp of the Balcones Fault Zone, which rises 98 ft I (30 m) to 295 ft (90 m) above the Coastal Plain (Figure 2.3).
- Rocks and soils that outcrop in this part of Texas are limestones, clays and
- sands of Cretaceous and Cenozoic age. They dip southeast at angles slightly
, greater than the slope of ground surface. For this reason outcrops of strata j are progressively older toward the northwest. ,
i
- The Mount Bonnell Fault, a member of the Balcones Fault Zone, is located about 1640 ft (500 m) northwest of the reactor facility. It separates limestone and i dolomite of the Lower Cretaceous Edwards Formation on the upthrown side of the fault from chalk and limestones of the Austin Group of Upper Cretaceous age on the downthrown side.
1
! The site is located in the Gulf Coastal Plain Tectonic Province. The Balcones l Fault is a major fault system within this province that crosses Travis County i '
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i, and extends to the southwest and northeast for several hundred miles. It is comprised of numerous down-to-the-Gulf normal faults that experienced movement
- .through the Miocene Epoch. No evidence of displacement younger than 5 million j years has been detected. Therefore, the Balcones Fault Zone is not capable j within the meaning of Appendix A, 10 CFR 100.
2.6 Seismology J ,
l The Seismic zone map (Figure 2.4) of the Uniform Building Code shows The Uni-versity of Texas TRIGA reactor site to be located in a zone where no damage from earthquakes is expected. However, this does not mean that the area is aseismic. For instance, the Austin, Texas, region has experienced three (re- '
corded) earthquakes within a 50-mi (92.6-km) radius (Carlson, 1984) since the ,
i late nineteenth century (Figure 2.5):
) (1) (May 1,1873, Manor earthquake with epicentral Modified Mercalli Intensity
- (P94I) III-IV (2) January 5, 1887, Paige earthquake with epicentral intensity V (MMI) 3 (3) October 9, 1902, Creedmoor earthquake with epicentral intensity IV-V (MMI)
! Other regions in central and east Texas have experienced earthquakes of epicen-tral intensity V and possibly VI (MMI). Damage from an intensity VI earthquake is limited to cracked plaster and damage to chimneys. Structures of good design j do not begin to experience damage from intensities below VII (MMI). Therefore, if state-of-the-art engineering practices for general structures of common de-sign are adhered to, seismic excitation from earthquakes of intensities V or VI i (MMI) are not expected to affect the integrity of the proposed reactor.
2.7 Hydrology Water drainage of the immediate site to prevent flooding is primarily related to the potential but temporary occurrence of extreme rainfall rates. Surface water runoff from the Balcones Research Center site is drained into the Shoal j Creek watershed except for the extreme northeast region of the site that drains into the Walnut Creek watershed. The proposed facility is located in the north-east site region with drainage into the Walnut Creek watershed. It is situated at an elevation well above the local area flood plain, and located nearly equi-l distant 0.5 mi (0.8 km) from drainage easements of both watersheds. Thus no I significant general site area flooding is anticipated.
Facility design includes provisions and features for removal of water runoff l from roof and surrounding areas. Water drainage from the site is also provided
- from the drive access area to avoid localized flooding of the lower level. The drainage provisions and small area for water accumulation compared to the large area of the first floor level combine to limit the potential for any flooding i of the first level.
i 1 2.8 Conclusion ,
4 l
- On the basis of the above considerations, the staff concludes that the natural ,
teatures and characteristics of the reactor site make it suitable for construc- 1 tion and operation of the reactor.
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3 DESIGN OF STRUCTURES, SYSTEMS, AND COMPONENTS The TRIGA Mark II reactor will be located on the first level in a special reactor room of the Nuclear Engineering Teaching Laboratory (NETL) building. The building includes office space, general laboratory areas, specialized laboratory areas, i shop areas for mechanical or electrical work, and the reactor facility. Build-ing orientation, floor plans, and a section of the reactor room area are shown in Figures 3.1 through 3.4.
The NETL building site is located above a rock subsurface composed of limestone that will accommodate substantial loads. Building foundation is composed of poured concrete pieces with concrete slab on compacted fill. Building superstruc-l ture is constructed of reinforced concrete for columns, beams, floors and roof.
Exterior structure walls are fabricated of precast concrete slabs.
4 3.1 Wind Damage The Nuclear Engineering Teaching Laboratory (NETL) building which has been designed for 70-mi per hour (1.88-km/ min) winds including factors for wind gust-conditions in excess of the 70-mph (1.88-km/ min) value. The peak wind recorded in Austin, Texas, was 57-mph (1.53-km/ min) in February 1947. Meteorological data indicate a low frequency of tornadoes and effects of tropical disturbances, but a moderately high frequency of summer thunderstorms. The UT TRIGA reactor facility will be located about 7 ft (2.13 m) below the mean site grade level, and the building is constructed of reinforced concrete. On the basis of the above information, the staff concludes that wind damage to the UT reactor is very unlikely.
3.2 Water Damage As indicated in Section 2, the site surface water is drained into the Shoal Creek watershed and the Walnut Creek watershed. The proposed facility is situ-ated well above the local area flood plains and is located about 0.5 mi (0.8 km) from drainage easements of both watersheds. No significant general site area flooding is anticipated. Facility features are designed to prevent local flood-ing for heavy rainfall. However, in the event that some flooding would occur on the facility first level, loss of the building's electric power would auto-matically scram the reactor and there would be no impact on safety. Therefore, the staff concludes that water damage to the reactor that could affect safety is extremely unlikely.
3.3 Seismically Induced Reactor Damage The UT reactor facility will be constructed in a 0 seismic zone where no damage 4 from earthquakes is expected (see Section 2.6). Since the proposed NETL build-ing is designed with state-of-the-art engineering practices, the staff concludes that in the event of an earthquake, its integrity will not be affected.
The UT TRIGA reactor will be located on the ground level of this building, on a
, concrete pad, and is surrounded by a concrete shield structure. An earthquake UT TRIGA Reactor SER 3-1
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of M I VI is not expected to have any significant effect on the reactor or on the ability to shut the reactor down. However, even if a rare severe earthquake does occur resulting in reactor loss of coolant or fuel damage, the analyses in Section 14 indicate that it will not affect the health and safety of the public.
3.4 Mechanical Systems and Components '
The mechanical systems and components of importance to the reactor safety are the control rod drive assemblies. They are mounted on a bridge assembly over the reactor pool and consist of motors, gear boxes, electromagnets, switches and wiring. The transient control rod for pulsing is operated with a pneumatic drive. These control rod assemblies are designed to be fail safe in case of a power failure from either man-made or natural hazard. These mechanical systems and components are securely attached to the reactor bridge assembly and are well protected by the physical containment of the reinforced concrete reactor building. Therefore, the staff concludes that damage to the mechanical systems and components from man-made or natural hazard are not likely.
3.5 Conclusion The UT reactor facility has been designed and constructed to withstand all credible and probable wind and flood events associated with the site. The con-sequences of an unlikely seismic event would not pose a significant radiological hazard to the public (see Section 14). Therefore, the staff concludes that the construction of the facility is acceptable and the proposed operation of the reactor will not cause significant radiological risk to the operation staff or to the public.
i t
4 REACTOR ,
I The University of Texas (U1) reactor will be a Genera 1' Atomic (GA) TRIGA Mark II
. reactor.. It will be a heterogeneous, pool-type reactor incorporating solid ,
uranium-zirconium hydride fuel-moderator elements with an enrichment of 19.7% '
assU. The reactor core will be submerged in a large, open tank of light water that acts as both a moderator and coolant. The reactor will be controlled by inserting and withdrawing neutron-absorbing control rods. Pulses will be initi-ated by the pneumatic ejection of a transient rod. An overall view of a typical TRIGA Mark II reactor is given in Figure 4.1, and the principal design parameters are listed in Table 4.1.
4.1 Reactor Facility The UT has been operating a GA TRIGA Mark I reactor on its main campus in Austin, Texas since 1963. It will be decommissioned when the new facility is completed.
The new reactor facility will be constructed at the Balcones Research Center, about 7 mi (11.6 km) from the existing facility. The only parts of the existing reactor that will be used in the new one are the fuel elements, the reactor bridge assembly and the three control rod drive mechanisms, which will be recon-ditioned by General Atomic Technology, Inc.
4.2 Reactor Core The reactor core will consist of a lattice of 86 cylindrical U-ZrH fuel ele-x ments, ~31 graphite elements, 3 fuel-followed control rods, and 1 air-followed transient control rod. The elements will be held in concentric rings by upper and lower aluminum grid plates. The active (or fueled) region of the reactor core will form a right circular cylinder $21.88 in. (55.58 cm) in diameter and
$15 in. (38 cm) high and will contain $7.5 lb (3.4 kg) of 23sU. Water coolant will occupy approximately one-third of the core volume.
4.2.1 Reflector Assembly, Grid Plates, and Core Support Structure A graphite radial reflector 10.2 in. (25.9 cm) thick and 21.8 in. (54.4 cm) high will surround the core region. Top and bottom axial reflection will be provided by $3.45-in. (8.76-cm)-long graphite plugs incorporated into individ-ual fuel elements.
The fuel elements will be positioned laterally at the top and bottom by two aluminum grid plates that are 0.625 in. (1.59 cm) and 0.75 in. (1.91 cm) thick, respectively. The lower grid plate will support the weight of the fuel elements.
The grid plates will be supported by pads welded to a ring that is welded to the radial graphite reflector assembly. The reflector assembly will be supported by an aluminum platform at the bottom of the reactor pool. In addition, a i safety plate of 0.50-in. (1.27 cm)-thick aluminum will be provided to preclude the possibility of control rods falling out of the core. The safety plate will be welded to the radial graphite reflector assembly and located $16 in. (40 cm) below the bottom grid plate.
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Table 4.1 Principal design parameters Parameter Description Reactor type TRIGA Mark II Maximum licensed non pulsing power level 1.1 MW Maximum pulse 2.20% ak/k (3.14$)
Fuel element design Fuel-moderator materici U-ZrHx
- Uranium content 8.5 wt%
Uranium enrichment 19.7% 2ssU Shape Cylindrical Length of fuel 15 in. (38.1 cm) overall Diameter of fuel 1.43 in. (3.63 cm) o.d.
Cladding material 304 stainless steel Cladding thickness 0.020 in. (0.051 cm)
Number of fuel elements Critical core s64 Operational core s90 Excess reactivity, maximum 4.9% ak/k (7.0$) (Tech. Spec.
maximum limit above cold, clean, critical condition)
Number of control rods 4 Transient (air-followed) 1 Shim (fuel-followed) 1 Safety (fuel-followed) 1 Regulating (fuel-followed) 1 Total reactivity worth of rods 8.7% ak/k (12.5$)
Reactor cooling Natural convection of pool water p effective 0.7% ak/k l
- The nominal H/Zr ratio is 1.60:1 and the maximum value is 1.65:1.
i l
4.2.2 Fuel Elements The reactor will use stainless-steel-clad cylindrical fuel elements in which the enriched uranium is mixed homogeneously with a ZrH x m derator.
The fuel part will consist of a cylindrical rod of U-ZrH containing x $8.5 wt% uranium enriched to slightly <20%. The nominal weight of 2ssU in each fuel element I will be $38 g. The hydrogen-to-zirconium atos ratio of the fuel moderator material will be $1.6 to 1. The fuel section of each element will be 15 in.
(38.1 cm) long and 1.43 in. (3.63 cm) in diameter. Graphite end plugs $3.45 in. (8.76 cm) long and located above and below the fuel region will serve as axial neutron reflectors. The fueled section and graphite end plugs will be contained in a 0.020-in. (0.051-cm)-thick stainless-steel-walled can welded with stainless-steel fittings at the top and bottom. Each element will be 428.8 in. (73.2 cm) long and will weigh ~7.0 lb (3.2 kg). A schematic view of a TRIGA stainless-steel-clad fuel element is shown in Figure 4.2.
Two fuel positions will centain a special instrumented fuel element into which three thermocouples were fitted during fabrication. The sensing tips of the fuel-element thermocouples will be located *0.3 in. (0.8 cm) from the vertical centerline. An instrumented fuel element is identical to a standard fuel ele-ment in all other respects. The thermocouples will monitor the fuel element temperatures and provide a scram signal upon sensing a preselected value. Graph-ite elements will be used to fill grid positions not occupied by fuel-moderator elements, control rods, or other core components. These elements will be of the same general dimensions and construction as the standard fuel elements but will be filled entirely with graphite and will be clad with aluminum. A plan view of the core showing the positions of normal, instrumented, and graphite elements is shown in Figure 4.3.
4.2.3 Neutron Source and Holder A 2 or 3 curie americian-beryllium neutron source will be used for startup. The neutron source holder is made of aluminum, cylindrical in shape, and will have a cavity to hold the source. The source holder can be installed in any vacant fuel or graphite element location.
4.2.4 Control Rods i Power levels in the UT TRIGA reactor will be regulated by four control rods:
one shim rod, one safety rod, one regulating rod, and one transient rod. The neutron poison material in all four control rods will be sintered compacts of boron carbide contained in a sealed stainless-steel tube.
4.3 Reactor Tank and Biological Shield The reactor tank will be a welded aluminum vessel located $7 ft (2 m) below main site grade level and surrounded by a reinforced concrete shield structure on the ground floor. The tank will be in the form of an elongated cylinder
$6.5 ft by 9.8 ft (2.0 m by 3.0 m) oval with a depth of 26.2 ft (7.7 m) and a capacity of >10,500 gal (39,743 L). The wall of the cylinder will be 0.25 in.
(0.64 cm) thick. The outside of the tank will have a bituminous coating for corrosion protection.
STAINLESS STEEL TOP END FITTING m
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The reactor centerline will be about 3.2 ft (1.0 m) above the bottom of the tank. Demineralized light water will serve as a radiation shield, neutron moderator, and reactor coolant. Heat will be dissipated by natural convective flow of pool water through the reactor core and forced circulation of the pool water through an external heat exchanger.
A cobalt-60 source (9000 Ci) is located on a shelf suspended in the reactor pool at the end opposite to the reactor location and it is at 10 ft (3.04 m) below the water level. Suspended fuel storage racks in the reactor tank will be available for routine storage of fuel elements and/or reactor components.
In addition, six 10.0-in. (25.4-cm)-diameter, 15-ft (4.6-m)-deep storage wells outside of the reactor pool will provide isolated storage for fuel elements or radiation sources. All storage racks have been designed to be critically safe
- for TRIGA fuel elements immersed in water.
The core will be shielded horizontally by a minimum of 9.5 ft (2.9 m) of ordi-nary concrete, 1.5 ft (45 cm) of water, and 10.2 in. (25.9 cm) of graphite reflector. Vertical shielding will be provided by at least 21.0 ft (6.4 m) of pool water above the core. A view of the reactor tank and shield structures is shown in Figure 4.4.
4.4 Reactor Instrumentation The reactor instrumentation will use two separate multifunct son computers to process the input from low-noise fission chambers. A separate gamma chamber to measure peak power and energy release will be used during the pulsing mode of operation. A detailed description of the reactor instrumentation is pro-vided in Section 7.
4.5 Dynamic Design Evaluation The safe operation of the UT TRIGA reactor will be accomplished by manipulating control rods in response to changes in measured reactor parameters such as power, flux, and temperature provided by the instrumentation channels. In addition, interlocks will prevent inadvertent reactivity additions, and a scram system will initiate rapid, automatic shutdown when safety settings are reached.
Additional stability and safety during both normal and pulsing conditions are incorporated into TRIGA reactors by virtue of the large, prompt, negative tem-perature coefficient inherent in the uranium-zirconium-hydride fuel-moderator material. The negative temperature coefficient is primarily a result of the spectral hardening properties of ZrHxat elevated temperatures, which increases neutron leakage from the fuel-bearing material into the moderator, where they are absorbed preferentially. The reactivity decrease is a prompt effect be-cause the fuel and ZrH are mixed homogeneously; thus, the ZrHx temperature x
rises essentially simultaneously with the reactor power. An additional contri-bution to the prompt, negative temperature coefficient is the Doppler broaden-ing of 2ssU resonances at high temperatures, which increases nonproductive neu-tron capture in these resonances (Simnad et al., 1976; General Atomic (GA)-0471, GA-4314).
This inherent property of U-ZrHxfuel has been the basis for designing TRIGA reactors with a pulse capability as a normal mode of operation. The large, UT TRIGA Reactor SER 4-7
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prompt, negative temperature coefficient rapidly and automatically compensates for step insertions of excess reactivity. In the pulse mode, it will terminate the resulting excursion without depending on electronic or mechanical safety systems or operator action. In the nonpulsing mode it serves as a backup safety feature, mitigating the effects of accidental reactivity insertions (Simnad et al., 1976; GA-0471; GA-4314). 4.5.1 Excess Reactivity and Shutdown Margin . The Technical Specifications for the UT TRIGA reactor limit the maximum excess reactivity to 4.9% Ak/k (7.0$) in the cold, xenon-free condition. The Technical Specifications also require a minimum shutdown margin of 0.2% Ak/k (*0.3$) with the highest worth control rod fully withdrawn and the highest worth nonsecured experiment in its most reactive state. The sum of the reactivity worths of all experiments in the reactor is limited by the Technical Specifications to 2.1% Ak/k (3.0$) and that of any single secured experitnent to 1.7% Ak/k (2.5$). The reactivity worth of movable experi-ments is limited to 0.7% Ak/k (1.0$). The control rod worths are 2.1% Ak/k (3.0$) for the transient rod, 2.6% Ak/k (3.7$) for the shim rod, 2.0% Ak/k (2.9$) for the regulating rod, and 2.0% Ak/k (2.9$) for the safety rod, yielding a total rod worth of 8.7% Ak/k (12.5$). Assuming the core configuration will consist of 86 fuel elements plus three fuel-followed control rods and the core excess reactivity will be at its maxi-mum technical specification limit of 4.9% Ak/k, the minimum shutdown margin with the highest worth rod fully withdrawn is 1.2% Ak/k (1.8$) = (8.7 - 2.6 - 4.9). Therefore, the core configuration will meet the excess reactivity and shutdown requiracums. 4.5.2 Normal Operating Conditions The Technical Specifications impose a safety limit of 2102*F (1150*C) for the maximum fuel temperature provided the fuel element cladding temperatures do not exceed 932*F (500 C). For fuel element cladding temperatures greater than 932*F (500*C), the Technical Specifications impose a safety limit of 1742*F (950*C) for the maximum fuel temperature. The safety limit for high-hydride (ZrH1.6) stainless-steel-clad fuel elements ( is based on preventing excessive stress buildup in the cladding because of l hydrogen pressure from disassociation of ZrHx . Based on theoretical and experi-mental evidence (Simnad et al., 1976; GA-4314), the above limits represent a {i conservative value to provide confidence that the fuel elements will maintain , their integrity and that no cladding damage will occur. Further limitations j are imposed on reactor power level and pulse reactivity insertion to provide assurance that the safety limit will not be exceeded. At the maximum licensed nonpulsing power level of 1100 kW, the maximum fuel temperature will be $887'F l (~475 C). During the maximum allowed 2.2% Ak/k (3.14$) pulse, local fuel tem-1 peratures will not exceed 1004 F (540 C). Scrams will be provided to shut the reactor down whenever the nonpulsing power level exceeds 1100 kW or the measured fuel temperature in a B-ring element (Figure 4.3) exceeds 1022*F (550*C). Based on radial and local power distributions, these requirements ensure that the above safety limits will not be exceeded anywhere in the core. UT TRIGA Reactor SER 4-9
4.5.3 Assessment The staff concludes that the inherent large, prompt, negative temperature coefficient of reactivity of U-Zrh fuel x moderator provides a basis for safe operation of the research reactor in the nonpulsing mode and is the essential characteristic supporting the capability of operation of the reactor in a pulse mode. Furthermore, the Technical Specifications require that the core excess reactiv-ity and experiment reactivity worths be limited so that the reactor always can be brought to a subcritical condition even if the highest worth control rod were removed totally from the reactor. The core configuration meets all of these limitations. The safety limits at the UT TRIGA reactor are based on theoretical and experi-mental investigations and are consistent with those used at other similar reac-tors. Adherence to these limits should provide confidence that fuel element integrity will be maintained. Operating data at maximum licensed nonpulsing power and at maximum pulse reactivity insertion show that the maximum fuel ele-ment temperatures remain well below the prescribed safety limit. TRIGA reac-tors similar to the UT TRIGA reactor have demonstrated safe and reliable opera-tion at nonpulsing power levels up to 1.5 W and pulse reactivity insertions up to 3.5% Ak/k (5.00$) (Simnad et al., 1976; GA-4314). On the basis of these considerations, the staff concludes that, under normal operating conditions, there is reasonable assurance that the UT TRIGA reactor can be operated safely at 1.1 W and 2.20% Ak/k (3.14$) pulses as limited by the Technical Specifica-tions requirements. 4.6 Functional Desian of Reactivity Control System The power level in the UT TRIGA reactor will be controlled by three control rods (one shim, one safety, and one regulating rod) and one safety transient rod, all of which will contain boron carbide as the neutron poison. The posi-tions of the four control rods are shown in Figure 4.3. Fod movement will be accomplished using rack-and pinion electromechanical drives for each control rod and a pneumatic electromechanical drive for the transient rod. Each control rod drive system will be energized from the control console through its own independent electrical cables and circuit % which tends to , minimize the probability of multiple malfunctions of the drives. When a scram l signal is received, all four control rods will fall by gravity into the core, thereby shutting down the reactor. 4.6.1 Control Rod Drive Assembly The control rod drive assemblies for the control rods will be mounted on a bridge assembly over the pool; each assembly will consist of a nonsynchronous, single-phase electric motor coupled to a rack-and pinion drive system. A draw tube connected to the rack will support an electromagnet that, in turn, will engage an iron armature attached to the upper end of a long connecting rod. The con-trol rod proper will be attached to the lower end of the connecting rod. During normal operation, the electromagnet will be energized, and the motorized system will insert or withdraw the control rod at a rate of ~11.5 in./ min (0.5 cm/s). If power to the electromagnet is interrupted for any reason, the connecting rod UT TRIGA Reactor SER 4-10
will be released, and the control rod will fall by gravity into the core, rapidly shutting down (scramming) the reactor. Limit switches mounted on the drive assembly will actuate circuits that will indicate on the control console the up (fully withdrawn) and down (fully in-serted) position of the magnet, the down position of the rod, and whether the magnet is in contact with the rod. In addition, a helipot connected to the pinion will generate position indications for the shim, safety, and regulating rods that will be displayed on the control console. 4.6.2 Transient Rod Drive Assembly The transient rod drive will be mounted on a steel frame that is bolted to the bridge and will be operated by a pneumatic drive system consisting of a single- l acting pneumatic cylinder whose piston is attached to the transient rod by a connecting rod. For pulse operation, compressed air will be admitted to the bottom of the cylinder through a solenoid valve, driving the piston upward in the cylinder and driving its connected transient rod out of the core. At the end of its stroke, the piston will strike the anvil of a shock absorber and decelerate at a controlled rate. Adjustments of the cylinder positions in relation to the piston head will control the piston's stroke length and hence l the extent of transient rod withdrawal from the core and the corresponding l amount of reactivity inserted during a pulse. The adjustment will be performed electrically at the rod drive housing. When the solenoid valve is deenergized, air will be vented from the cylinder, causing the transient rod to drop by gravity into the core. Limit switches mounted on the drive assembly will actuate circuits that indi-cate on the control console the up (fully withdrawn) and down (fully inserted) position of the magnet, and the down position of the rod. In addition, a heli-pot connected to the pinion will generate position indications for the tran-sient rod that are displayed on the control console. In the pulse mode, actuation of the transient rod by pneumatic operation will be prevented by control logic if a reactivity insertion value of more than 2.2% Ak/k (3.00$) is indicated or the prepulse power level is more than 1 kW. In the nonpulsing mode, an interlock will prevent application of air to the transient rod unless the shim, safety, and regulating rods are in the full "in" position. Thus, in preparation for high power operation, the transient rod always will be withdrawn first, thereby becoming, in effect, a safety rod. 4.6.3 Scram-Logic Circuitry and Interlocks The UT TRIGA reactor will be equipped with a scram-logic safety system that receives signals from core instrumentation (low-noise fission chambers) and other system instrumentation to initiate a scram by removing electrical power from the control rod magnets. The reactor parameters that will initiate these scrams are (1) high reactor power (2) high fuel temperature (3) high voltage failure on either or both safety channels UT TRIGA Reactor SER 4-11
1-(4) peak power (pulse mode) (5) minimum period (available but use is optional) , (6) external safety switches (as required) (7) manual scram
. Several safety interlocks will be incorporated into the control rod circuitry to prevent inadvertent reactivity insertions. During nonpulsing operation, the interlocks will prevent the simultaneous withdrawal of two standard control rods and the withdrawal of the transient rod if the regulating, safety, and
+ shim rods are not inserted fully. In the pulse mode, only the transient rod
, will be able to be moved. In addition, control rod withdrawal will not be allowed unless an adequate source signal is available to allow proper startup of the reactor.
3 Additional details concerning the safety-logic circuitry and interlocks is provided in Section 7. 4.6.4 Assessment j The UT TRIGA reactor safety and control system design uses proven state-of-the-art components and technology. It incorporates a new control console design, i two standard NM-1000 safety channels along with a control system computer that is programmed with all the necessary logic functions that are specified by elec-tronic circuits and electrical relay circuits in other TRIGA reactor facilities. l The control rods, rod drives, and scram and interlock logic have performed re- ' 4 liably and satisfactorily in the original UT reactor, and similar equipment has shown satisfactory performance in many other TRIGA reactors over a long period i of time. ! The control system design allows for an orderly approach to criticality and for safe shutdown during both normal and emergency conditions. There is sufficient redundancy of control rods to ensure safe shutdown even if the most reactive rod fails to insert upon receiving a scram signal. The reactivity worths and ! speed of travel of the control rods are adequate to allow complete control of l- the reactor system during operation from a shutdown condition to full power. Interlocks are provided to preclude inadvertent rod movement that might lead to hazardous conditions. Independent scram sensors and circuits incorporated to shut the reactor down automatically mitigate the consequences of single mal-
- functions. A manual scram button allows the operator to initiate a scram when-
- ever such action is needed.
f- In addition to the active electromechanical safety controls for normal and abnormal conditions, the large, prompt, negative temperature coefficient of i reactivity i;iherent in the U-ZrH xfuel-moderator, discussed in Section 4.5, provides a unique backup safety feature. The reactor shutdown mechanism of this fuel mixture will limit the power level and terminate reactor transients that produce large increases in temperature. Because this inherent shutdown mechanism acts to limit the magnitude of a possible transient accident, it
- would mitigate the consequences of such accidents and can be considered to be a fail-safe safety feature.
In accordance with the above discussion, the staff concludes that the re- , activity control systems of the UT TRIGA reactor are well designed and will l UT TRIGA Reactor SER 4-12
function adequately to ensure safe operation and safe shutdown of the reactor under all credible conditions. 4.7 Operational Procedures The University of Texas has implemented administrative controls at its existing campus reactor facility that require review, audit, and written procedures for all safety-related activities. A Reactor Operation Committee reviews all aspects of current reactor operation to ensure that the reactor facility is operated and used within the terms of the facility license consistent with safety of the pub-lic as well as of the operating personnel. The responsibilities of this com-mittee include review and approval of operating procedures, experiments, and proposed changes to the facility or its Technical Specifications. These admin-istrative controls will apply to the new reactor facility. Written procedures (reviewed and approved by the Reactor Operation Committee) for the new facility have been established for safety-related activities, in-cluding reactor startup, operation, and shutdown; preventive or corrective main-tenance; and periodic inspection, testing, and calibration of reactor equipment and instrumentation. The reactor will be operated by trained NRC-licensed personnel in accordance with the above mentioned procedures and Technical Specifications. 4.8 Conclusions The staff review of the proposed UT TRIGA reactor facility has included studying its proposed design and installation, its proposed control and safety instrumen-tation, and specific preoperational plans. As noted earlier, these features are similar to those typical of other TRIGA-type research reactors operating in many countries of the world. There are currently 11 TRIGA reactors operating at 1 MW or greater with no safety-related problems. On the basis of its review of the proposed UT TRIGA reactor and e,.perience with these other facilities, the staff concludes that there is reasonable assurance that the UT TRIGA reactor will be capable of safe operation, if constructed in accordance with the design and as limited by its Technical Specifications. l l l UT TRIGA Reactor SER 4-13
J i j 5 REACTOR COOLANT AND ASSOCIATED SYSTEMS The core of the UT TRIGA reactor will be cooled by natural convection of
$10,500 gal (38,600 L) of deionized light wacer. The reactor coolant will be
- pumped to a heat exchanger where the reactor heat will be removed before it is returned to the pool. The quality of the reactor coolant will be maintained by a purification system. A schematic of the reactor coolant system is given in Figure 5.1, and the coolant system instrumentation is described in Section 7.
5.1 Coolina System Suction of water from the pool will be provided by inlets that extend no more than 6.6 ft (2 m) below the top of the reactor tank. The suction intake will be composed of a bulk flow inlet for most of the intake volume and a limited volume flow inlet for water surface skimming. The coolant water will be drawn through the coolant pump and forced through the heat exchanger. Cooled water will be returned to the reactor pool by a discharge outlet above the reactor core or an outlet near the tank bottom. A diffused water jet will be created at the outlet by a nozzle above the reactor core. Delay and diffusion of the reactor core convective coolant column will be enhanced by the action of the coolant discharge nozzle. Accidental siphoning of reactor pool water will be prevented by the presence of suction breaks on both the suction and discharge lines of the coolant system. Siphon breaks will be created by holes located in the lines 1.6 ft (s0.5 m) below the normal water level. The heat exchanger and pump, which are the major components of the cooling sys-tem, will be located at about the same vertical level as the reactor core. ! Valves will be provided in the coolant loop for control and isolation of the cooling system. Chilled water for the secondary side of the heat exchanger will be provided by the university's physical plant. Apositivepressuredifferenceof1 psi)7kPa)betweentheshell-sideoutlet and tube-side inlet of the heat exchanger will be provided to prevent leakage of primary pool coolant into the secondary chilled water system. 5.2 Primary Coolant Purification System A purification loop will be incorporated into the cooling system. The loop will bypass the heat exchanger and will be located at about the same vertical location as the heat exchanger. A portion of the cooling system flow less than 10 gal / min will be diverted through the purification loop during operation of the cooling system. A small purification loop pump will be operated when the cooling system is not in operation to allow continuous removal of suspended particulates and soluble ions from the water coolant. Water suction and dis-i charge will be accomplished by the same lines that are used by the cooling system. The purification system will be operated either independently or in conjunction with the cooling system. 1 UT TRIGA Reactor SER 5-1
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Purification will be provided by two components: a filter for removal of sus-pended materials and a resin bed for removal of soluble elements. Filtration will be provided by 25 pm filters. Ion exchange will be provided by 3 ft3 of cixed cation and anion resins. Water purity will be measured by conductivity cells at the inlet and outlet of the resin bed. The purification loop flow rate will be indicated by a flow meter so that flow rate through the resin bed can be controlled. 5.3 Primary Coolant Makeup System Makeup reactor pool water is supplied by the city water system and manually cdded to the pool through the purification loop, Makeup water for the reactor pool is about 5-10 gal / week. 5.4 Conclusion The reactor coolant system design, including the reactor pool and the primary cooling and purification loops, has the same design features as used in many cther operating TRIGA facilities. There is no new or unproven technology involved in the proposed system. Furthermore, adequate reactor cooling is Ensured by the large cooling capacity inherent in the reactor pool volume, as well as the capacity of the cooling system. The staff has reviewed the applicant's heat transfer calculations relative to core cooling and coolant system component capacities and agrees that the reactor can operate at maximum licensed power with fuel temperatures well below the level where cladding damage might occur. Thus, the staff concludes that the reactor cooling and purification system designs for the UT TRIGA reactor facil-ity are adequate for safe operation. UT TRIGA Reactor SER 5-3
6 ENGINEERED SAFETY FEATURES The two engineered safety features of the UT TRIGA reactor facility will be the reactor room and the ventilation system. These features are designed to eliminate or mitigate the release of radioactive materials during routine or , l emergency conditions. 6.1 Reactor Room , The reactor room is designed to operate normally at a negative pressure of *2 in. of water to reduce the possibility of releasing radioactivity that might be pro-duced in the facility. All doors into the room will be fitted with seals. All other penetrations will be limited in size and sealed to minimize air leakage.
- 6. 2 Ventilation System The main ventilation system design consists of a blower that exhausts the reac-tor room air through the HEPA filter system and then through a roof stack at least 44 ft (13.4 m) above ground level. Another blower introduces filtered and temperature-conditioned air into the reactor room. When an exhaust air particulate monitor signals a high radiation level, the blowers will shut down automatically; and the system isolation dampers will close, effectively isolat-ing the reactor room.
A low-volume auxiliary ventilation system will be installed to purge radioactive gases from areas of expected production to the roof stack. 6.3 Conclusion The reactor room and ventilation system at the UT TRIGA reactor facility are well designed. The technology used in the design, fabrication, and installa-tion of the various components is well established and time proven. Isolation of the reactor from adjacent areas of the facility and other areas of the site will be accomplished effectively under both routine and postulated emergency conditions. Thus, the staff concludes that these engineered safety features will be adequate for safe reactor operations at the proposed UT TRIGA reactor facility. 2 UT TRIGA Reactor SER 6-1
+ T 7 CONTROL AND INSTRUMENTATION SYSTEMS 1 The University of Texas TRIGA reactor control and instrumentation system will l l be a computer-oriented system design incorporating state-of-the-art components and technology. The control console that will be located in the control room will display reactor parameters on digital meters and a color graphics display cathode-ray tube (CRT) screen. The control console also will contain various annunciators and the switches required for reactor operation. The remaining computer components will be contained in racks in the reactor room. A logic diagram for the control and instrumentation system is shown in Figure 7.1. 7.1 Evaluation and Checkout of TRIGA Control System Console The applicant submitted a checkout and evaluation plan for the TRIGA control system console which is intended to be applied by both GA Technologies and The University of Texas. The staff has reviewed the system design and the checkout and evaluation plan and finds that adequate consideration has been given to the calibration of the TRIGA control system console, and to periodic checkouts to ensure its availability. In addition, there is adequate redundancy and diver-sity in the nuclear and temperature monitoring circuits. On the basis of the review, the staff concludes that the system design and its checkout plans are acceptable. i 7.2 Control System The control system will consist of those components that control the operation of the reactor control rods as well as associated equipment appropriate to the reactor operating mode selected. The reactor control rods and rod drive mech-anisms are described in Section 4. 7.2.1 Control Console 1 The reactor control console is shown conceptually in Figure 7.2. Two indepen-dent instrumentation computers will have power and temperature readouts on digital meters. The operator also may call up any of these parameters for display on I the color CRT monitor. Two disc drives, a printer, and a terminal will be asso-l ciated with the control system computer (CSC). The CSC will manage all control rod movements, accounting for such things as interlocks and choice of particular operating modes. The CSC also will pro-cess and display information on control rod positions, power level, and fuel and water temperature and can display pulse characteristics and cooling system parameters. Many other functions also can be performed by the CSC, such as calibrating control rods and monitoring reactor usage. l The conceptual layout of the control panel is shown in Figure 7.3. The features ! of the panel are (1) key switch for rod magnet power (2) reactor operating mode switches l (3) rod control switches and annunciators UT TRIGA Reactor SER 7-1 k
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7.2.2 Operating Modes There will be four modes of operation associated with the UT TRIGA reactor: manual, automatic, square-wave, and pulse. 7.2.2.1 Manual Mode Regardless of which mode will be selected subsequently, reactor startup always will be done in the manual mode. Manual rod control will be accomplished by the switches on the rod control panel. Depressing any one of the CONTACT /0h (C/0) pushbuttons will interrupt the current to that magnet and drop the rod. If the rod is above the down limit, it will fall back into the core until the magnet is driven to the down limit, where it again contacts the armature. The ! relative position of all control rods will be illustrated on the CRT. Depressing the appropriate switch will cause the control rod to move in the direction indicated. Several interlocks will prevent the movement of the rods in the UP (withdrawn) direction. These are (1) scrams not reset (2) magnet not coupled to armature (3) source level below minimum count (4) two UP switches depressed at the same time (5) mode switch in the PULSE position (6) mode switch in AUTOMATIC position (regulating rod only) There will be no interlock inhibiting the DOWN (insert) direction of the control rods except in the case of the regulating rod while in the AUTOMATIC MODE. 7.2.2.2 Automatic Mode Automatic power control can be obtained by switching from manual operation to automatic operation. The regulating rod then will be controlled automatically in response to a power level and period signal. Reactor power level will be compared with the demand level set by the operator and the signal difference will be used to bring the reactor power to the demand level on a fixed preset period. The purpose of this design feature is to maintain the preset power level automatically during long-term power runs. There will be options avail-able to oper te in the automatic mode using control rods other than the regu-lating rod 7.2.2.3 square-Wave Mode In square-wave operation, the reactor will first be brought to a power level below 1 kW, leaving the transient rod partially in the core. The transient rcd will then be ejected from the core by means of the transient rod FIRE button. Within a few seconds the power level reaches the higher demand level, and it will be maintained at the higher level by immediately switching to automatic mode. 7.2.2.4 Pulse Mode Reactor control in the pulsing mode will consist of establishing a power level below 1 kW. This will be accomplished using the motor-driven control rods, UT TRIGA Reactor SER 7-5
leaving the transient rod either fully or partially inserted. The transient rod then will be ejected using the FIRE button. The MODE SELECTOR switch auto-matically will connect the gamma pulsing chamber to monitor and record peak flux (nv) and energy release (nvt). 7.3 Instrumentation System The instrumentation system design will be composed of nuclear and process insicu-mentation that will provide the operator with the information necessary for the proper operation and the control of the facility. 7.3.1 Nuclear Instrumentation The nuclear instrumentation will use two separate multifunction computers pro-cessing the input of low-noise fission chambers. A separate gamma chamber to measure peak power and energy release will be used during the pulsing mode. One of the nuclear instrumentation computers will provide wide-range log power indication from source range up to 150% power and a separate output to the linear percent power safety channel with level scram, as well as the adjustable power level scram function. This computer also will provide period indication and information to the adjustable period scram channel. The computer automatically will test the system to ensure that the higher power ranges are operable while the reactor is operating in the lower ranges, and vice versa when the reactor is at high power. The second nuclear instrumentation computer will provide the multirange linear power range data as well as the percent power safety channel with scram. This computer will take the input signal from its fission chamber and convert it into 10 linear power ranges, providing a more precise indication than the log channel. Range switching can occur either automatically or manually as selected by the operator. The same self-checking design features that exist in the log channel are included. The fission chambers that will provide input signals to the two computers are of a similar design to those previously used in the original UT TRIGA facility except that additional shielding has been used to improve the signal-to-noise ratio and thereby provide a usable signal from source range to maximum power. The neutron channel operating ranges are shown in Figure 7.4. A low sensitivity ionization chamber will provide signals to a microprocessor that provides output to the control recorder and CRT when in the pulsing mode. 7.3.1.1 Reactor Scram System A reactor protective action will interrupt the magnet current and result in the immediate insertion of all rods when activated by a safety channel. The minimum safety system channels and their set points are listed in Table 7.1. 7.3.2 Nonnuclear Instrumentation The nonnuclear process instrumentation will measure reactor fuel temperature and reactor coolant system parameters and display them for operator information. I { l UT TRIGA Reactor SER 7-6
2000 MW - - PULSE 200 MW - _ MODE 20 MW - B C 2 MW - .A. -- -- -- _ 100% 200 kW - - 10% 20 kW -
- 1:
2 kW - - 10'It 1 POWER 200 W - CHANNELS 10 2:
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- 10 31 TRIP 2W - -
10~4 0.2 W - - 10-5g 0.02 W - - 10 % SOURCE LEVEL 0.002 W - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 10~7%
--T SOURCE INTERLOCK TRIP 0.0002 W 10-8%
i A = Wide Range Log Channel B = Wide Range Linear Channel C = Manual, Automatic, and Squarewave Modes l Figure 7.4 Neutron channel operating ranges
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UT TRIGA Reactor SER 7-7
Table 7.1 Minimum reactor safety system channels Safety Channel Function Set Point Manual scram Scram Manual Fuel temperature Scram 550*C Linear power level Scram 110% of full scale Pe. cent power level Scram 110% of full scale Peak pulse power Scram 110% of full scale High voltage Scram Loss Magnet current Scram Loss Minimum period Scram Available as desired External safety switches Scram As required The output of chromel/alumel thermocouples embedded in reactor fuel (described in Section 4) is processed and displayed continuously on a digital meter on the control console and the CRT. The reactor pool water temperature will be displayed continuously on a control console meter and may be called up on the CRT. The reactor pool outlet and inlet water temperatures may be called up by the operator for display on the bulk pool water temperature meter and/or the CRT. The conductivity of the coolant in the purification loop will be measured at the inlet and outlet of the demineralizer. The operator may select either of these readings for display. There will be annunciators on the ccntrol console (Figure 7.3) that alarm for various unsafe conditions. These channels and their set points are listed in Table 7.2. Table 7.2 Console alarm settings ! Instrumental Channel Alarm Setting Pool water level 20 ft (6 m) above grid plate AP between primary and secondary l coolant systems 4 psi (27.6 to Pa) Primary coolant flow 0 Pool water temperature 110 F (43.3 C) In addition to the instrumentation displays in the control room, there will be several flow, temperature, and pressure gauges in the coolant treatment area , for local readout, l I l l l UT TRIGA Reactor SER 7-8
7.4 Conclusion The design of the UT TRIGA reactor control and instrumentation systems uses some new computer technology and hardware that has not been used previously in NRC-licensed nonpower reactors. However, these systems will be adequately tested and evaluated before operation in the UT facility and some of the com-ponent designs are in use in new power reactor facilities. Incntporation of digital electronic techniques to replace analog circuitry will result in mark-edly improved performance. In addition to normal reactor control and measure-Eent functions, the functional self-checks, circuit calibrations, and automatic data logging will result in a significant improvement in efficiency and avail-ability of information. UT TRIGA Reactor SER 7-9
d 8 ELECTRIC POWER SYSTEM 8.1 Electrical Power System and Emergency Power The electrical power for building lighting and reactor instrumentation will be standard commercial single phase, 60 Hz, 110/220 V that is furnished by the Lower Colorado River Authority Power Co. through a transformer and several con-trol panels located throughout the building. The electrical power for the cool-ant pumps and the crane will be three phase and provided through a dedicated control panel. Because the reactor control rods will scram in the case of a power interruption and the decay heat generated in the core following a scram will not cause fuel temperature to rise above the allowable limit, no emergency power will be needed or supplied. 8.2 Conclusions The staff concludes that the design of the electrical power system and the in-herent safety of the reactor design are adequate to ensure the safe operation of the UT TRIGA reactor. The applicant and the control and instrumentation system vendor have developed a program whereby the system will be used on a similar reactor at the vendor's facility. After checkout and evaluation, the equipment, with appropriate modi-fications, will be assembled at the reactor facility and will be checked thor-oughly and evaluated before and during reactor startup. The staff further concludes that the design of the UT TRIGA control and instru-mentation system coupled with the applicant's commitment to a thorough checkout and evaluation of the equipment will result in an adequately reliable system. UT TRIGA Reactor SER 8-1
9 AUXILIARY SYSTEMS 9.1 Ventilation System The ventilation system is considered an engineered safety system and is described in Section 6. 9.2 Fire Protection System Fire protection will be provided by fire standpipes and portable extinguishers located throughout the facility. The Campus Fire Marshall and the city of Austin fire department will survey the facility and will be supplied with information to enable rapid and safe response to a fire alarm. 9.3 Communications System Several communication systems will be installed in the facility. An intercom system will be provided that has stations in the control room, in the reactor room, and in the receptionist's office. An internal telephone system with stations suitably located throughout the building will be provided. Standard commercial telephone service will connect into the main University system. 9.4 Compressed Air System The compressed air system will consist of a compressor and a series of pipes, regulators, and valves to provide compressed air to the facility. A line will take air from the compressor; pass it through a filter, dryer, and regulator; and supply it to the reactor control system for pulsing operations, for pneumatic transfer system and for central thimble. 9.5 Air Conditioning System The reactor facility is supplied with air heated or cooled for human comfort and to provide a compatible environment for the electronic equipment. The air is conditioned by a central unit that uses water from the Balcones Center central chilled water plant or steam from a gas-fired boiler in the Nuclear Engineering Teaching Laboratory (NETL) building. 9.6 Fuel Handlina and Storace Fuel storage will consist of in pool storage racks for storage of irradiated fuel elements and a cluster of six fuel storage pits located outside and adja-cent to the reactor pool. The storage pits can be used for fuel elements and radiation sources. All storage facilities have been designed to prevent criti-cality when fully loaded. The reactor section of the facility will be serviced by a pendant-operated 5-ton crane to facilitate fuel transfer within the pool or for use of a fuel transfer cask. Other specialized equipment will be provided to service the reactor core UT TRIGA Reactor SER 9-1
s and the irradiation facility. This equipment will include handling casks for radfoactive samples and handling equipment for reactor fuel elements. 9.7 Conclusion Thes't$ffconcludesthattheseauxiliarysystemswillbeadequatetosupport
' the UT TRIGA reactor in a safe and reliable manner.
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10 EXPERIMENTAL PROGRAMS The UT TRIGA reactor will serve as a source of neutrons for research and limited radionuclide production. In addition to bulk in pool irradiation capabilities, the specialized experimental facilities will include a pneumatic transfer system, a rotary specimen rack, five beam tubes, and a central thimble. 10.1 Reactor Experimental Facilities 10.1.1 Pool Irradiations This reactor's open pool will permit the irradiation of experiments submerged in the vicinity of the core, yet outside of the cylindrical graphite reflector. The decision to perform experiments in the reactor pool as opposed to using the pneumatic transfer system, five beam tubes, or the central thimble for in-core irradiation will be dictated by specimen size and the type and intensity of radiation fields desired. The actual placement of experiments or samples in the core region will be controlled by their potential effect on reactivity, which is limited by the Technical Specifications. 10.1.2 Pneumatic Transfer System The pneumatic transfer system will allow small sealed samples to be transported rapidly between the reactor core region and the radiochemistry laboratory, which will have a pass-through opening to the activation analysis laboratory. This system will permit studies involving short-lived radioisotopes. The in-core terminus of this system will be located in the outer ring of fuel element posi-tions. Compressed air will be used to move the sample containers through 1%-in. (32-mm)-diameter aluminum tubing. Current plans call for exhausting the pneu-matic transfer system to the ventilation system to minimize 42Ar buildup. Procedures for use of the pneumauc transfer system are expected to prevent serious exposure to personnel in the event the sample container becomes stuck. 10.1.3 Rotary Specimen Rack A rotary, multiple position specimen rack located in an indented raceway in the top of the graphite reflector will permit production of radioisotopes and the simultaneous activation and irradiation of numerous samples. All positions in this rack will be exposed to neutron fluxes of comparable intensity. Samples. will be loaded from the reactor bridge through a watertight tube using a sample lifting device. This rack will be rotated manually or by a motor drive. 10.1.4 Central Thimble The reactor will be equipped with a central thimble for conducting experiments or irradiating small samples in the core at the point of maximum neutron flux. The central thimble will consist of a 1 -in. (38-mm)-outside diameter aluminum tube fitting through the center hole of the top and bottom grid plates. Holes in the tube will ensure that it normally fills with water; however, a special UT TRIGA Reactor SER 10-1
cap may be attached to the top end, compressed air applied, and the water column removed to obtain a well-collinated beam of neutrons. Vertical irradiation tubes similar to the central thimble may be positioned in any of the fuel element positions. The actual placement of experiments or samples in the core region is limited by the Technical Specifications. 10.2 Special Experimental Facilities An irradiator consisting of 156 pencil-shaped cobalt-60 (scCo) sources (9000 Ci) will be located in the pool opposite the reactor. Samples will be exposed to this irradiator in watertight canisters or dry vertical tubes. There appears to be no potential effects or interactions of this irradiation on the reactor that could have any impact on safety. 10.3 Beam Tube Facilities Five beam ports will provide tubular penetrations through the concrete shield and reactor tank water, making beams of neutrons (or gamma radiation) available for experiments. The ports will be closed with neutron and gamma shield plugs, which will reduce dose rates to acceptable levels during operation. Doors on inactive beam tubes will be shown to be closed by lights on an indicator at the control console. Seal welds or high-integrity mechanical seals will prevent leakage of coolant water. Current plans call for exhausting the beam tubes to the ventilation system to minimize " Ar buildup. 10.4 Experimental Review Before any new experiment will be conducted using the reactor experimental facilities, it will be reviewed and approved by the Reactor Operation Committee. This committee is composed of at least three members knowledgeable in fields that relate to nuclear safety. In addition to ensuring reactor safety and con-formance with licensed conditions, this review and approval process for experi-ments will allow personnel specifically trained in radiological safety and re-actor operations to consider and recommend alternative operational conditions (such as different core positions, power levels, and irradiation times) that might decrease personnel exposure and/or the potential release of radioactive materials to the environment. 10.5 Conclusion The staff concludes that the design of the experimental facilities, combined with the detailed review by the Radiation Safety Committee and administrative procedures applied to all research activities, are adequate to ensure that experiments will not pose an unacceptable risk of radiation exposure to operat-ing personnel or the public. I l UT TRIGA Reactor SER 10-2
/
l 11 RADI0 ACTIVE WASTE MANAGEMENT The major radioactive waste generated by reactor operations will be activated gases, principally 41Ar produced by neutron irradiation of air dissolved in the coolant water. A small volume of radioactive solid waste, primarily spent ion exchange resins and filters, will be generated by reactor operations, and some additional solid waste will be produced by the associated research programs. No radioactive liquid wastes will be generated directly by normal reactor oper-ations. Small amounts of radioactive liquid waste may be developed as a result of several of the reactor-related research activities. These research activ-ities are conducted under authority of the State of Texas Department of Health. 11.1 ALARA Commitment The UT Radiation Safety Committee instructs all reactor personnel to develop procedures to maintain the generation and possible release of radioactive waste materials at a level as low as reasonably achievable (ALARA). Examples of the ALARA commitment in the area of radioactive waste management are (1) de-sign of a system to transfer resins as a slurry, thereby reducing handling of resins, and (2) setting a goal of zero liquid waste from reactor operations. 11.2 Waste Generation and Handling Procedures 11.2.1 Solid Waste Solid waste generated as a result of reactor operations will consist primarily of ion exchange resins and filters, potentially contaminated paper and gloves, and occasional small, activated components or samples. Reactor-based research can be expected to result in the generation of' solid low-level radioactive waste such as contaminated paper, gloves, and glassware. This solid waste generation is expected to contain a few millicuries of radionuclides in a volume of
$17.7 fta/yr (s0.5 m3 /yr). The primary radionuclides involved will be 60 Co, s9Fe, 24Na, 27gg, seMn, and 187Cs.
Solid waste will be collected by the university's health physics staff, com-bined with other university generated waste, and held temporarily before being packaged and shipped to an approved disposal site in accordance with applicable regulations. Packaging and temporary storage will be done in a manner that is likely to prevent loss of control of any contaminated waste. For example, the ion exchange resin will be double bagged in polyethylene and placed in a prop-erly labeled drum that is stored in a locked, dry storage area until shipment. 11.2.2 Liquid Waste Normal operations will produce no radioactive liquid waste. However, some cleaning activities or irradiations may generate limited volumes of such waste. These solutions will be collected and retained in designated tanks. The waste solutions will be diluted as necessary and eventually discarded to the sanitary sewer under the supervision of the university's radiation safety staff at con-centrations within the guideline values of 10 CFR 20.203. 1 UT TRIGA Reactor-SER 11-1
11.2.3 Airborne Waste As no gaseous fission products escape from fuel cladding during normal opera-tions, the airborne waste of concern will be the radioactive gas produced by neutron activation of the constituents of air dissolved in the pool water. Of special interest are the 180 (n, p) 18N and the 48Ar (n, y) 41Ar reactions. Calculations by the applicant indicate dose rates at the pool surface from 18N rising from the core region might be as high as 400 mrem /h if no diffusion flow is Irovided. Because diffusion flow will be provided, a longer time to reach the pool surface will allow 18N to decay to lower concentrations. Actual dose rates at the pool surface from 18N are expected to be less than 20 mrem /h. In areas occupied by personnel, the 18N dose rate will not be a major consideration. 41Ar will be released from the pool surface and from the experimental facil-ities (primarily the beam tubes and pneumatic transfer system). The equilibrium concentration of 41Ar in the reactor, coming only from the pool, was calculated by the applicant and is not expected to exceed 2.1 x 10 3 *Ci/ml (s0.01% of 10 CFR 20 restricted area limits). A larger amount of 41Ar release averaged over a year will not cause a dose in an unrestricted area in excess of 100 mrem /yr. This dose is well within the 500 mrem /yr limit specified by 10 CFR 20. 11.3 Conclusion The staff concludes that waste management activities proposed for the new UT TRIGA reactor facility will be conducted in a manner consistent with the guide-lines of 10 CFR.20 and with ALARA principles. This conclusion is based on the staff's review of waste management plans for the new facility and on satisfac-tory practices at the original UT reactor facility. Because 41Ar will be the only potentially significant radionuclide released by the reactor to the environment during normal operations, the staff has con-sidered its release at the expected maximum power level. A conservative esti-mate of the dose beyond the limits of the reactor facility give reasonable assurance that potential dose to the members of the public as a result of 41Ar will be under 20% of that permitted in 10 CFR 20 when averaged over a year. l l l i l l UT TRIGA Reactor SER 11-2
12 RADIATION PROTECTION PROGRAM The University of Texas has a structured radiation protection with the radia-tion safety staff and monitoring equipment needed to control radioactive mate-rials and to measure occupational radiation exposures at its facilities. The UT radiation safety staff provides independent review of radiation protection activities performed by operating staff and experimenters at its reactor facil-ity and other laboratories. The daily implementation of radiation protection activities at the new reactor facility will be performed by trained members of the operations staff. 12.1 ALARA Commitment The charter of the UT Radiation Safety Committee has established formally the policy that operations are to be conducted in a manner to keep all radiation exposures ALARA. All proposed experiments and procedures at the reactor will be reviewed for ways to minimize the potential exposures of personnel. Any unanticipated or unusual reactor-related exposures will be investigated by both the health physicists and operation staffs to develop methods to prevent recurrences. 12.2 Health Physics Program 12.2.1 Health Physics Staff i The University's Radiation Safety Officer is a nonvoting member of the Reactor Operation Committee. The radiation safety staff at The University of Texas consists of a professional health physicist and two senior-level technicians. This staff provides radiation safety support to the entire UT complex, includ-ing an accelerator and many radioisotope laboratories. The radiation safety staff is on call and visits facilities on an as-needed basis. Although current plans do not call for permanent assignment of a radiation safety technician at the Balcones Research Center, the possible need will receive consideration dur-ing the initial phases of operation. 12.2.2 Procedures Detailed written procedures will be prepared or updated to address the radiation protection activities to be conducted during routine operation of the reactor facility. These procedures will identify the tasks assigned to the operations and radiation safety personnel. They also will specify administrative limits and action points, as well as appropriate responses and corrective action if these limits or action points are reached or exceeded. These procedures are reviewed by the Reactor Operation Committee and will be readily available to the operations, research, and radiation protection staffs and to the administra-tive personnel. 12.2.3 Instrumentation The University of Texas has a variety of detecting and measuring instruments for monitoring potentially hazardous ionizing radiation. Existing and planned UT TRIGA Reactor SER 12-1
2 instrument calibratia.: procedures and techniques give reasonable assurance that applicable types of radiation at significant intensities will be detected and measured correctly. ) 12.2.4 Training All reactor-related personnel will have received an indoctrination in radia-tion safety before they assume their work responsibilities. Other personnel in restricted areas of the reactor facility on a temporary basis will be accom-panied or monitored closely by reactor-related personnel. Additional radiation safety instruction will be provided to those who will be worki~ng directly with radiation or radioactive materials. The training program is designed to iden-tify the particular hazards of each specific type of work to be undertaken and methods to mitigate their consequences. Training in radiation safety will be provided, as needed, by the operations staff. Evaluation in the form of annual written examinations and performance observation will be conducted over a 2 year
- cycle. Examination results will be used to determine whether additional train-l ing of personnel is required.
12.3 Radiation Sources
- 12.3.1 Reactor Sources of radiation directly related to reactor operations will include radia-tion from-the reactor core, ion exchange columns, filters in the water cleanup systems, and radioactive gases (primarily 41Ar).
The fission products will be contained in the stainless-steel cladding of the fuel. Radiation exposures from the reactor core will be reduced to acceptable levels (1 mrem /h) by water and concrete shielding. Access to the reactor bay will be controlled during operation by a lock-and-key arrangement. The ion exchange resins and filters will be changed routinely before high levels of !. radioactive materials have accumulated, thereby limiting personnel exposure. Personnel exposure to the small amount of radioactive 41Ar will be limited by i its dilution and prompt removal through the ventilation system. 4 12.3.2 Extraneous Sources Sources of radiation that may be considered as incidental to the normal reactor operation but associated with reactor use include radioactive isotopes produced for research, activated components of experiments, and activated samples or specimens. Personnel exposure to radiation from intentionally produced radioactive mate-rial as well as from the required manipulation of activated experimental.com-ponents will be controlled by operating procedures that use the normal protective measures of time, distance, and shielding. These procedures receive review by the Reactor Operation Committee. Additionally, a 60C0 gamma irradiator (9000 Ci) will be located in the end of l the reactor pool opposite the reactor. This facility will be authorized within i the reactor license. Interaction between the radiations of the reactor and l irradiator is expected to be insignificant. UT TRIGA Reactor SER 12-2
12.4 Routine Monitoring 12.4.1 Fixed-Position Monitors The UT reactor facility will have several fixed position gamma radiation moni-tors in the experimental areas and an air particulate monitor located in the reactor. All gamma monitors have adjustable alarm set points and read out in the control room. The air particulate monitor will close the exhaust damper in the reactor bay exhaust and air supply ducts auto:natically and shut off the blowers if an alarm occurs. 12.4.2 Experimental Suppor_t The university's Radiation Safety Officer participates in experimental planning by reviewing all proposed procedures for methods of minimizing personnel exposures and limiting the generation of radioactive waste. Approved procedures specify the type and degree of radiation safety support required by each activity. 12.5 Occupational Radiation Exposures 12.5.1 Personnel Monitoring Program Personnel monitoring at the proposed facility will be consistent with existing practice. The university's existing personnel monitoring program is described in its Radiation Safety Instructions. To summarize the program, personnel expo-sures are measured by the use of film badges supplied and processed by a service contractor. File badges are assigned to all reactor-related individuals who might be exposed to radiation. In addition, self-reading pocket dosimeters are used, and instrument dose rate and time measurements are used to administratively keep occupational exposures below the applicable guidelines of 10 CFR 20. All visitors are provided with a self-reading dosimeter for monitoring purposes. Records of readings are kept in the visitor register. 12.5.2 Personnel Exposures The original UT research reactor annual exposure records for the last 5 years were reviewed as an indication of the effectiveness of the ALARA program. No doses in excess of 0.1 rem /yr were received. Although the dose data were too i few to verify a downward trend, they were sufficiently low to indicate a working ALARA program. l 12.6 Effluent Monitoring 12.6.1 Airborne Effluents As discussed in Section 11 of this report, airborne effluents from the reactor facility will consist principally of 41Ar from two sources. A small amount of 41Ar will be released from the pool into the reactor room, diluted by the 164,000-ft3 (4575-m 3 ) volume of ice in the reactor room, and discharged to the The forced ventilation system will provide two air changes per hour. roof vent. ! The saturation concentration in the reactor room was calculated to be on the l order of 2.2 x 10 5 pCi/mL (clearly a permissible concentration in a restricted area). A larger amount of 41Ar will be exhausted from experimental facilities UT TRIGA Reactor'SER 12-3 l t
F i (the beam tubes and pneumatic transfer system) and transferred directly by venti-lation duct to the roof vent. Potential doses in unrestricted areas near the tnilding will be monitored either by calculations based on measurements of 41Ar in the duct or by placing an integrating dosimeter at the point of interest. 12.6.2 Liquid Effluents Small amounts of radioactive liquid waste will be generated during routine operations. These will consist primarily of cleaning solutions. Before any releases of potentially contaminated liquid to the sanitary sewer system, representative samples will be collected and analyzed by standard tech-niques. If the concentrations of radioactive materials in the waste are less than the guideline values of 10 CFR 20.303, the liquids will be discharged di-rectly to the sewer. 12.7 Environmental Monitoring i Routine environmental sampling near the proposed facility is not considered necessary. However, environmental sampling is being considered to establish base-line radioactivity and chemical data at the Balcones Research Center before reactor operation. 12.8 Potential Dose Assessments Natural background radiation levels in the Austin, Texas, area result in an ex-posure of about 100 mrem /yr to each individual residing there. At least an ad-ditional 8% (s8 mrem /yr) will be received by those living in a brick or masonry structures. Any medical diagnostic X-ray examination will add to the natural background radiations, increasing the cumulative annual exposure. Conservative calculations by the applicant based on the amount of 41Ar released during normal operations from the reactor facility indicate a maximum annual exposure of 100 mrem /yr in the unrestricted area immediately outside the fa-cility. These calculations were verified by the staff. 12.9 Conclusions The staff concludes that the radiation protection program will receive appro-priate support from The University of Texas administration. The staff con-cludes that (1) the radiation protection program will be staffed and equipped properly, (2) the university's radiation safety staff will have adequate author-ity over and communication with the operating staff, (3) procedures will be pro-vided and integrated into research plans, and (4) operations and procedures will continue to achieve ALARA principles. The staff further concludes that the effluent monitoring programs conducted by UT personnel will be adequate to promptly identify significant releases of radioactivity to predict maximum ex-posures to individuals in an unrestricted area. Predicted maximum levels are well within applicable regulations and guidelines of 10 CFR 20. Accordingly, the staff concludes that the UT radiation protection program is acceptable and that there is reasonable assurance that the personnel and pro- ! cedures will protect the health and safety of the public during routine reactor l operations to a degree that is ALARA. UT TRIGA Reactor SER 12-4
f 13 CONDUCT OF OPERATIONS i 13.1 Overall Organization The UT TRIGA reactor facility is administered by the Director of the Nuclear Engineering Teaching Laboratory who is responsible to the Mechanical Engineering Department and the dean of the College of Engineering. Responsibility for the safe operation of the UT reactor facility is vested within the chain of command shown in Figure 13.1. 13.1.1 Radiation Safety Committee The President of The University of Texas appoints three members and a Chairperson to the Radiation Safety Committee. Responsibilities of this committee include all policies and practices regarding the license, purchase, shipment, use, moni-toring, disposal, and transfer of radioisotopes or sources of ionizing radiation at The University of Texas at Austin, Texas. 13.1.2 Radiation Safety Officer A Radiation Safety Officer acts as the delegated authority of the Radiation Safety Committee in the daily implementation of policies and practices regard-ing the safe use of radioisotopes and sources of radiation as determined by the committae. The responsibilities of the Radiation Safety Officer are outlined in The University of Texas at Austin Manual of Radiation Safety. 13.1.3 Reactor Operation Committee The Reactor Operation Committee is established through the office of the Dean of the College of Engineering at UT. The responsibilities of this committee include the evaluation, review, and approval of facility standards for safe operation. The Dean appoints at least three members to the committee who rep-resent a broad spectrum of reactor technology expertise. The Reactor Operation Committee meets at least twice each calendar year. 13.2 Training liost of the training of reactor operators is done by inhouse personnel. The applicant's operator requalification program has been reviewed, and the staff concludes that it meets applicable regulations (10 CFR 50.34(b)), and is, there-fore, acceptable. 13.3 Emergency Planning In accordance with 10 CFR 50.54(q) and (r) requirements, the applicant submitted an Emergency Plan on November 9, 1984. The plan was reviewed against the require-ments of Appendix E to 10 CFR 50. In addition, the review extended to ascertain- ! ing the degree of conformance with the guidance criteria set forth in Revision 1, to Regulatory Guide 2.6 and ANSI /ANS 15.16-1982, " Emergency Planning for Research Reactors." The staff has completed its review and found the plan to be accept-able, with two remaining open items. UT TRIGA Reactor SER 13-1
9 Office, President University of Texas at Austin Vice President for Academic Affairs and Research Dean College of Engineering Radiation Chairman Reactor Safety Department of Operation Committee Mechanical Engineering Committee e g I I Director l h----- Nuclear Engineering Teaching Laboratory
=----
l l l I Supervisor j IL----== Reactor ----- Operations Line of Responsibility
---- Line of Communication Figure 13.1 Organizational structure UT TRIGA Reactor SER 13-2
l Emergency procedures and guidance documents in support of maintaining emergency preparedness are to be prepared before actual implementation of the plan, when the facility is nearing completion. Agreement letters with offsite support groups to the Emergency Plan, describing the arrangements, capabilities, and responsibilities will be provided when the facility is constructed and nearing operational status. The currently operating UT reactor maintains several agree-ment letters as part of its operating license (R-92) Emergency Plan. The staff has reasonable assurance that similar suitable agreements will be obtained for the new facility. 13.4 Reactor Startup Plan The applicant submitted a startup plan which is to be implemented at the UT reac-tor facility after initial tests of facility systems are completed. In accor-dance with the operating license technical specifications to which this plan will be appended, a report will be submitted to the NRC within 90 days after completion of startup testing of the reactor. The first phase of the startup plan will involve determinations of critical core configuration and inventory. An estimate of integral control rod worths will be made from the criticality data. The second phase of the startup plan will consist of determining major core parameters. The third phase of the startup plan will consist of operational testing, including pulse step reactiv-ity insertion, instrumentation linearity and radiation doses around the reactor shield structure. The staff has reviewed the plan and concludes that it is adequate to provide the required baseline data for the new reactor. 13.5 Operational Review and Audits The Reactor Operation Committee (ROC) provides independent review and audit of facility activities. The ROC must review and approve proposed changes to the reactor operating license or procedures and plans for modifications to the reac-tor and new experiments. The ROC also is responsible for conducting audits of reactor facility operations and management and for reporting the results to the President of The University of Texas. 13.6 Quality Assurance Plan The quality assurance (QA) program for the design, construction, and operational phases of the UT reactor facility was reviewed by the staff for compliance with applicable portions of 10 CFR 50.34 and with Regulatory Guide 2.5, " Quality Assurance Program Requirements for Research Reactors," Revision 0-R, October 1977. 1977. The staff concludes that the UT QA program satisfies the criteria of Regulatory Guide 2.5 and 10 CFR 50.34 and is, therefore, acceptable. I 13.7 Physical Security Plan A Physical Security Plan for The University of Texas Mark II Reactor Facility was submitted on December 17, 1984, in accordance with 10 CFR 50.34C and is under review by the staff. All remaining open items will be resolved before UT TRIGA Reactor SER 13-3 _. _ __ ~ , - _ . _ _ _ _
an operating license is issued and the status of the plan will be addressed again in a supplement to this SER. 13.8 Review of Operational History The staff has reviewed available annual reports and inspection reports for the past several years of the currently operating UT reactor operation. The staff also has discussed the licensee's performance with NRC Region IV inspection per-sonnel specifically with respect to overall management of the current facility and conformance with the provisions of the license. The information obtained from these sources indicates that the UT has operated and managed their reactor facility in a competent and responsible manner. The staff believes there is reasonable assurance that the proposed UT reactor facility will be similarly operated and managed. 13.9 Conclusion On the basis of the above discussions, the staff concludes that the applicant has sufficient experience, management structure, and procedures to provide reasonable assurance that the reactor will be managed in a way that will cause no significant risk to the health and safety of the public. i i l UT TRIGA Reactor SER 13-4
14 ACCIDENT ANALYSIS In establishing the safety of the construction and operation of the UT TRIGA reactor, the applicant analyzed credible accidents to ensure that these events would not result in potential radiological hazards to the reactor staff or the public. The NRC staff has evaluated the applicant's submitted documentation and also has analyzed various potential site-specific events. These analyses included the various types of possible accidents and their potential conse-quences to the public. The following potential accidents or effects were considered to be sufficiently credible for evaluation and analysis: (1) fuel handling accident (2) rapid insertion of reactivity (nuclear excursion) (3) loss of coolant (4) misplaced experiments (5) mechanical rearrangement of the fuel (6) effects of fuel aging Of these potential accidents, only one, the fuel handling accident will cause loss of cladding integrity of one irradiated fuel element outside the reactor pool, releasing radioactivity in air in the reactor room and to the environment outside the UT TRIGA reactor building. The staff has designated the fuel han-diing accident as the maximum hypothetical accident (MHA). An MHA is defined as a hypothetically conceived accident for which the risk to the public health and safety is greater than that from any event that can be postulated mechanisti-cally. Thus, the staff assumes that the accident occurs, but does not attempt to describe or evaluate all of the mechanical details of the accident or the probability of its occurrence. Only the consequences are considered. The results of the analyses of accidents with less severe consequences than the MHA are included to demonstrate the extent of the staff investigation. 14.1 Fuel Handling Accident This potential accident, designated as the MHA, includes various incidents to at least one or more irradiated fuel elements in which the fuel cladding might be breached or ruptured. The staff did not try to develop a detailed scenario j but assumed conservatively that the cladding of one fuel element completely fails and that this occurs outside the reactor pool, instantly releasing the volatile fission products that have accumulated in the free volume (gap) be-tween the fuel and the cladding. Furthermore, the staff assumes conservatively that the accident occurs following an extended run at full licensed power such that the inventories of all significant radionuclides are at their maximum (saturation) values. Several series of experiments at GA have given data on the species and fractions of fission products released from U-ZrH xunder various conditions (GA-4314; GA-8597; Foushee and Peters, 1971). The noble gases were the principle species UT TRIGA Reactor SER 14-1
4 . found to be released. When the fuel specimens were irradiated at temperatures below 662*F (350*C),.the fraction released could be summarized as a constant equal to 1.5 x 10 5, independent of the temperature. At temperatures greater than 662*F (350*C),the species released remained the same, but the fraction released increased significantly with increasing temperature. l ! GA has proposed a theory describing the release mechanisms in the two tempera-l ture regimes that appears to be valid, although the data do not agree in detail (GA-8597; Foushee and Peters, 1971). It seems reasonable to accept the inter-pretation of the low-temperature results, which imply that the' fraction released
; for a typical TRIGA fuel element will be a constant, independent of operating l history or details of operating temperatures, and will apply to fuel whose tem-i perature is not raised above 662*F (350*C). That means that the 1.5 x 10 s j release fraction could be reasonably applied to TRIGA reactors operating up to at least 800 kW. However, the UT TRIGA reactor has a licensed nonpulsing power level of 1100 kW with a peak fuel temperature of $887*F (s475*C).
The theory for the fuel temperature regime above 662* (350*C) is not as well
, established as in the lower temperature regime. The proposed theory of release l of the fission products incorporates a diffusion process that is a function of temperature and time. Therefore, in principle, details of the operating history and temperature distributions in fuel elements would be required to obtain ac- . tual values for release fractions at the higher temperatures. In situations
! where a fuel cladding failure was assumed, the staff used the GA results l (GA-8597; Foushee and Peters, 1971) to estimate fission product release frac-tions.~ The staff considers these results to be conservative in that they repre-sent a theoretical maximum release greater than corresponding experimental ob-servations. Thus, for the fuel handling accident, the staff estimated a fission product release fraction of 7.5 x 10 5 of the inventory of both noble gases and halogens for the temperature regime above 662*F (3506C). l Because the noble gases do not condense or combine chemically, it is correct to j assume that any noble gases released from the cladding will diffuse in the air
- until their radioactive decay. On the other hand, the iodines are chemically I
active and are not volatile below about $356*F (*180*C). Therefore, some of i the radiciodines will be trapped by materials with which they come in contact,
- such as water and structures. Evidence indicates that most of the iodines
; either will not become or not remain airborne under many accident scenarios
- that are applicable to nonpower reactors (NUREG-0771, 1981). However, to be l certain that the fuel-cladding-failure scenario discussed below led to upper-limit dose estimates for all relevant events, the staff assumed that 100% of the iodines in the gap become airborne and that all fission products had reached their saturated activity levels. Normally, a significant amount of time elapses l before removing fuel from the reactor; however, no activity decrease was taken
! for radioactive decay during the time between reactor shutdown and removal of the fuel element from the pool into the air. These assumptions will be computed l thyroid doses that may be unrealistically high in some scenarios, for example, I those in which the pool water is present. I 14.1.1 Scenario The applicant and the staff analyzed similar scenarios that assumed a cladding , failure occurs in air in a B-ring fuel element immediately following an extended run at the authorized maximum power. All the noble gases and halogens in the UT TRIGA Reactor SER 14-2
fuel cladding gap are released from the fuel element and form a uniform distri- i bution in the reactor room. No plate-out was allowed. Scenarios incorporating ' realistic estimates of the above conservative assumptions could reduce the resulting doses significantly. The staff calculated the whole-body gamma-ray (immersion) dose and thyroid dose by iodine inhalation to an individual in the reactor room and in an unrestricted area immediately outside the building. For the occupational doses, it was as-sumed that the ventilation system was shut down at the time of the accident and all the fission products remained in the reactor room. For the outside doses, it was assumed that the proposed ventilation system was operating at its rated capacity. All dose calculations assumed immersion in a semiinfinite cloud (a very conservative assumption that produces the highest calculated exposures). 14.1.2 Assessment The calculated doses for the above assumptions and locations are presented in Table 14.1. Because there is no credible way in which the postulated accident could occur without operating personnel being alerted immediately, orderly evac-uation of the reactor room would be accomplished within minutes (*10 min.). As a result of the underlying calculative and atmospheric assumptions, the calcu-lated operational and public doses shown in Table 14.1 are higher than could occur realistically. On the basis of the discussions and analyses above, the staff concludes that if one fuel element from the UT TRIGA reactor were to re-lease all noble gases and halogen fission products accumulated in the fuel-cladding gap, radiation doses to both occupational personnel and to the public in unrestricted areas would be below the limits stipulated in 10 CFR 20, Appen-dix B. Accordingly, the staff concludes that there is reasonable assurance that the postulated accident poses no significant radiological risk to the health and safety of the public. l Table 14.1 Doses resulting from postulated
- fuel handling accident l
Whole-body Thyroid Dose and Location Immersion Dose Dose 10-min occupational dose in the reactor bay 40 mrem 3.4 rem 30-min public dose immediately outside the building 2.7 mrem 231 mrem 14.2 Rapid Insertion of Reactivity As discussed in Section 4.5 of this report, theoretical calculations have pre-i dicted and experimental measurements have confirmed that U-ZrH x fuel exhibits a strong, prompt, negative temperature coefficient of reactivity. This temper-l ature coefficient not only terminates a pulse or nuclear excursion but also l causes a loss of reactivity as the steady-state temperature of the fuel is raised. These results have been verified at many operating TRIGA reactors. Although it may be possible theoretically to rapidly add sufficient excess reactivity under accident conditions to create an excursion that would not be UT TRIGA Reactor SER 14-3 1
terminated before fuel damage occurred, the limits imposed by the design and Technical Specifications of the UT TRIGA reactor make such an event incredible. In some reactor configurations, full withdrawal of the transient rod could re-sult in a reactivity insertion greater than the authorized maximum pulse inser-tion. In such case, administrative controls are applied to the adjustment of I the transient rod stroke to ensure that the maximum allowed pulse reactivity is not exceeded. The Technical Specifications for the UT TRIGA reactor limit the maximum allowed pulse reactivity insertion to 2.2% ok/k (3.14$) and the total worth of the transient rod to 2.8% ak/k (4.00$). 14.2.1 Scenario This potential event is one in which the maximum excess reactivity available in , a single credible event is inserted into the reactor instantaneously. However, because of the Technical Specifications limitation, the staff finds no credible method of rapidly inserting the total excess reactivity into the core. The staff has considered the scenario of the reactor operating at some power level between 0 and 1100 kW, at which time all of the remaining excess reactiv-ity not compensated for by increased temperature is insertec rapidly. The anal-ysis neglected reactivity loss as a result of the buildup of tasXe. The staff found that the higher the temperature at which the rapid insertion is initiated, the lower the final temperature of the fuel immediately after the transient. Therefore, the staff has assumed the worst case as initiation of a 3.5% ak/k (5.00$) transient with the core at ambient temperature and essentially zero initial power. This corresponds to the complete ejection of the transient rod 2.8% ak/k (4.00$) simultaneous with the maximum addition of reactivity from an insecured experiment 0.7% ak/k (1.00$) in the core. The potential significant consequences of the reactivity insertion accidents considered by the staff are melting of the fuel or cladding material and failure of the cladding as a result of high internal gas pressures and/or phase changes in the fuel matrix. The primary cause of cladding failure at elevated temperatures in stainless-steel-clad elements would be excessive stress buildup in the clad-ding caused by hydrogen pressure from disassociation of the ZrH . Calculations x performed by GA and confirmed in many reactor pulses indicate that cladding integrity is maintained at peak fuel temperatures as high as 2147*F (1175 C) (GA-4314; GA-6874; Simnad et al., 1976). The staff used a Fuchs-Nordheim formulation modified to incorporate a tempera-ture-dependent specific heat (GA-7882) to calculate the accident conditions. The calculations indicated that the maximum fuel material temperature following a 3.5% ak/k (5.00$) reactivity insertion would be 1953 F (1067 C). The total energy released and the peak power in the pulse were calculated to be 51.1 MW-s and 7800 MW, respectively. 14.2.2 Assessment The staff also has reviewed the literature for large reactivity insertions into reactor cores similar to the UT TRIGA reactor. GA has performed many experiments with reactivity insertions as high as 3.5% ak/k (5.00$) in an 85-element TRIGA core. GA measured, among other parameters, the temperature of the fuel in the hotest core position and examined fuel elements af terward (GA-6874; Simnad et al. , UT TRIGA Reactor SER 14-4
1976). _There was no indication of undue stress in the cladding and no indica-tion of either cladding or fuel melting. The measured maximum temperature for the 3.5% ak/k (5.00$) pulse was $1382*F (750*C), and the estimated peak transient temperature at any localized point in the fuel was 2147*F (1175'C). Because the radial temperature distribution in a fuel element immediately following a pulse is similar to the radial power distribution, the peak transient tempera-ture immediately after the pulse is located at the periphery of the hottest fuel element. It will fall rapidly (within seconds) as the heat flows toward the cladding and toward the fuel center. It also was observed that for a 3.5% Ak/k (5.00$) pulse, the maximum measured pressure rise within an instrumented fuel element was far below the expected equilibrium value at the peak temperature (GA-6874; GA-9064; Simnad et al., 1976). From the above considerations, the staff concludes that there is no credible rapid insertion of 3.5% ak/k (5.00$) reactivity in the UT TRIGA reactor core that could lead to fuel melting or cladding failure resulting from high tem-perature or high internal gas pressure. Therefore, there is reasonable assur-ance that fission product radioactivity will not be released from the fuel to the environment as a result of an accidental reactor pulse or excess reactivity transient.
-14.3 Loss of Coolant A potential accident that would result in increases in the fuel and cladding temperatures is the loss of coolant shortly after the reactor has been operating.
Because water is required for adequate neutron moderation, its removal would terminate any significant neutron chain reaction. However, the residual radio-activity from fission product decay would continue to deposit heat energy in the fuel and would render the reactor core unshielded in the tank. It is assumed that the reactor has been operating at the licensed power of 1100 kW long enough to achieve fission product equilibrium (a conservative assumption based on expected usage) and is shut down at the initiation of a gross cooling-water leak. It is further assumed that heat is removed by con-vective water cooling until'the top of the core becomes uncovered, after which heat removal is provided only by air convection. Several investigations have evaluated such scenarios under various assumptions (GA-6596; GA-9064; Texas A&M, 1979; Oregon State University, 1968). In the UT TRIGA reactor, the core will remain completely immersed in water as long as the water level is ~5 ft (*1.5 m) above the tank bottom. That would require about 2100 gal (7950 L) of water in the tank and allow the removal of $8700 gal (*31,800 L) before the top of the core becomes uncovered. Because of the pip-ing arrangement, a break in the piping outside the reactor would only permit the water level to drop to ~1 ft (*0.5 m) below normal water level above the core. Accordingly, a significant leak can occur only in the liner below the core level. It is assumed that a gross constant leak of 500 gal / min (*32 L/s)
~
occurs at the bottom of the core tank liner, the core would remain covered for at least 16 min. Under these conditions, the peak temperature reached in the fuel would be less than 1382*F (750*C) which would not cause fuel cladding damage (see Section 14.2.1). A pulse performed immediately before water loss would not contribute signifi-cantly to the fission product decay heat. The heat generated during the loss UT TRIGA Reactor SER 14-5
l 1 of coolant with the pulse would be removed during the 16-min interval before the core becomes uncovered. The Technical Specifications require that corrective action be taken or the reactor be shut down if the water level falls below a level of $17 ft (5 m) above the top of the core. In addition, water level and radiation monitors would alert the operating staff to a low water condition. Even if the coolant loss was preceded by an extended reactor run at the maximum authorized power level of 1100 kW followed by a 2.2% Ak/k (3.00$) pulse, the resultant maximum fuel and/or cladding temperatures would not cause fuel damage or fission pro-duct release. From the above analysis, the staff concludes that loss of coolant at the UT ! reactor would not lead to fuel damage or consequent release of radioactivity to the environment. 14.4 Misplaced Experiments This type of potential accident is one in which an experimental sample or de-vice is inadvertently' located in an experimental facility where the irradiation conditions could exceed the design specifications. In that case, the sample might become overheated or develop pressures that could cause a failure of the
- experiment container. As discussed in Sections 10 and 13, all new experiments
- at the UT TRIGA reactor facility are reviewed before insertion, and all experi-ments in the region of the core are separated from the fuel cladding by at least one barrier, such as the pneumatic transfer and irradiation tubes, the central thimble, or the reflector assembly.
The staff concludes that the experimental facilities and the procedures for ex-periment review at The University of Texas are adequate to provide reasonable assurance that failure of experiments is not likely, and even if failure oc-curred, breaching of the reactor fuel cladding will not occur. Furthermore, if an experiment should fail and release radioactivity within an experimental fa-cility, there is reasonable assurance that the amount of radioactivity released l to the environment would not be more than that MHA discussed in Section 14.1. 14.5 Mechanical Rearrangement of the Fuel t This type of potential accident would involve the failure of some reactor system, such as the support structure, or could involve an externally originated event l that disperses the fuel and in so doing breaches the cladding of one or more l i fuel elements. ' The staff has not developed an operational scenario for such accidents. How-ever, the MHA assumes the failure of the cladding of a fuel element in air after extended reactor operation and evaluates possible doses resulting from the re-leases of the contained radioactive inventory. This encompasses the potential l consequences of any possible mechanical rearrangement accident. The staff con-cludes that no credible mechanical rearrangement would lead to an accident with more severe consequences than those accidents considered in Sections 14.2.1 and i 14.2.2. UT TRIGA Reactor SER 14-6
- - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - . _ - - - - _ _ - - - - _ . _ _ _ _ _ _ _ - _ _ - -_ = _ _ _ _
14.6 Effects of Fuel Aging , As discussed in more detail in Section 17, fuel aging is considered normal and is expected to occur gradually. The reactions external to the cladding that j might occur also are addressed in Section 17; the possibility of internal reac- ( tions is discussed in this section. There is some evidence that U-ZrH x fuel tends to f ragment with use, probably because of the stresses caused by high temperature gradients and the high rate of heating during pulsing (GA-4314; GA-9064). Some of the possible consequences of fragmentation are (1) a decrease in thermal conductivity across cracks, lead-ing to higher central fuel temperatures during normal operation (temperature distributions during pulsing would not be affected significantly by changes in conductivity because a pulse is completed before significant heat redistribu-tion by conduction occurs) and (2) an increase in the amount of fission pro-ducts released into the cracks in the fuel. With regard to the first item above, hot cell examination of thermally stressed hydride fuel bodies has shown relatively widely spaced radical cracks that would cause minimal interference with radial heat flow (GA-4314; GA-9064). However, after pulsing, TRIGA reactors have exhibited an increase in both steady-state fuel temperatures and power reactivity coefficients. At power levels of 1000 kW, temperatures have increased by ~42F (s23C ), and power reactivity coeffi-cients have increased by s20% (GA-5400; AFRRI, 1960). GA has attributed these changes to an increased gap between the fuel material and cladding (caused by rapid fuel expansion during pulse heating) that reduces the heat transfer coef-ficient. Experience has shown that the observed changes occur mostly during the first several pulses and have essentially saturated after 100 pulses. There-fore, the UT TRIGA reactor should not experience any further changes in the fuel-cladding gap caused by 2.2% Ak/k (3.00$) pulsas. Two mechanisms for fission product release from TRIGA fuel have been identified by GA (GA-4314; GA-8597; Foushee and Peters, 1971). The first mechanism is fission fragment recoil into connected gaps within the fuel cladding. This effect predominates up to ~752 F (s400 C) and is independent of fuel tempera-ture. GA has postulated that in a closed system such as exists in a TRIGA fuel element, fragmentation of the fuel material within the cladding will not cause an increase in the fission product release fraction (GA-8597). The reason for
' this is that the total free volume available for fission products remains con-stant within the confines of the cladding. Under these conditions, the forma-tion of a new gap or widening of an existing gap must cause a corresponding narrowing of an existing gap at some other location. Such a narrowing allows more fission fragments to traverse the gap and become embedded in the fuel or cladding material on the other side. In a closed system, the average gap size and, therefore, the fission product release rate remains constant independent of the degree to which fuel material is broken up.
Above 752 F (s400 C), the controlling mechanism for fission product release is diffusion, and the amount released depends on fuel temperature and fuel surface-to-volume ratio. However, release fractions used for safety evaluation are l based on a conservative calculation that assumed a degree of fuel fragmentation greater than expected in actual operation. UT TRIGA Reactor SER 14-7
l As the two likely effects of aging of the U-ZrHx fuel m derator will not have a significant effect on the operating temperature of the fuel or on the assumed release of gaseous fission products from the cladding, the staff concludes that there is reasonable assurance that fuel aging, compared with the MHA in Sec-tion 14.1, will not significantly increase the likelihood of fuel-cladding fail-ure or the calculated consequences of an accidental release in the event of the loss of cladding integrity. 14.7 Conclusion The staff has reviewed the credible transients and accidents for the UT reactor. On the basis of this review, the postulated accident with the greatest potential effect on the environment is the MHA, the loss of cladding integrity of one it-radiated fuel element in air in the reactor room. The analysis of this accident has shown that the expected dose equivalents in unrestricted areas would be be-low 10 CFR 20 guideline values. Therefore, the staff concludes that the design of the facility and the Technical Specifications provide reasonable assurance that the UT TRIGA reactor can be operated with no significant risk to public health and safety. l l l l l l l i I , UT TRIGA Reactor SER 14-8 l
, _ _ _ _ _ _ _ _ .- _ ___. - ~ - - -
15 TECHNICAL SPECIFICATIONS
'The staff has reviewed the preliminary version of the applicant's proposed Tachnical Specifications and found it to be generally acceptable. The final Tcchnical Specifications will be reviewed and approved by the staff before the operating license is issued. The Technical Specifications will be included as Appendix A to the operating license.
i i UT TRIGA Reactor SER 15-1
16 FINANCIAL QUALIFICATIONS l The University of Texas TRIGA reactor will be owned and operated by a state l university in support of its role in education and research. Therefore, the ' staff concludes that funds will be made available, as necessary, to support the construction and operations and eventually to shut down-the facility and main-tain it in a condition that would constitute no risk to the p0blic. The appli-cant's financial status was reviewed and found to be acceptable in accordance with the requirements of 10 CFR 50.33(f). UT TRIGA Reactor SER 16-1
17 OTHER LICENSE CONSIDERATIONS 17.1 Prior Utilization of Reactor Components Previous sections of this SER concluded that normal operation of the proposed l new UT TRIGA reactor will cause insignificant risk of radiation exposure to the public and that only an off-normal or accident event could cause some measur-tble exposure. Even the maximum hypothetical accident (MHA) would not lead to a dose to the most exposed individual greater than applicable guideline values of 10 CFR 20. While most of the systems and ccuponents of the proposed reactor are new, as noted before, the new UT reactor. facility will inherit some components from the currently operating 250-kW UT reactor, and from the 1-MW Northrop reactor which was shut down in 1984 and is in the process of decommissioning. The components that will be inherited from the original UT reactor are the reactor bridge assembly, the three control rod drive mechanisms, and all 92 stainless-steel-clad fuel elements. The reactor bridge assembly is a heavy grade structural steel I-beam device mounted over the reactor pool. It has not bien damaged or degraded from past use and is in good condition to support the nIw UT reactor's control rod drive mechanisms. The three control rod drive mechanisms from the current UT reactor will be totally reconditioned by GA Technologies Inc. and will be tested for their capability to precisely maneuver the control rods. In 1963 the original UT reactor was licensed with aluminum-clad fuel elements which were gradually replaced with new and used stainless-steel-clad fuel ele-ments during the 1970's. An additional 59 stainless-steel-clad fuel elements have been acquired from the Northrop reactor which was licensed with new fuel elements in 1963. Therefore, the burnup characteristics of the core for the proposed UT reactor will be that of a mid-life core, as opposed to a freshly fueled facility. BIcause the fuel cladding provides the principal defense against release of fission products to the environment, the staff nas considered whether prior use of the fuel elements might have caused significant degradai.Mn of the fuel cladding. Possible degradation mechanisms are (1) radiation degradation of cladding integrity, (2) high internal pressure caused by high temperature lead-ing to exceeding the elastic limits of the cladding, (3) corrosion of the clad-ding leading to thinning or other weakening, (4) mechanical damage as a result-of handling or experimental use. 4 17.2 Conclusions The staff's conclusions regarding these effects are as follows: (1) Nearly identical fuel has been laboratory tested elsewhere, and has been exposed under similar irradiation conditions to approximately the same or i higher radiation doses in operating reactors such as GA's 1.5 MW and 250 kW I 1 UT TRIGA Reactor'SER 17-1
reactors, which have been operating since the early 1960's, and the 1.5 MW reactor at the University of Illinois, which has been operating.with the same fuel elements that were acquired new in 1971. No significant radia-tion degradation of cladding has been noted in any of-these reactors. (2) The primary cause of cladding failure at elevated temperatures in stainless-steel-clad fuel elements is excessive stress buildup in the cladding caused by hydrogen pressure from disassociation of the ZrH x. GA has performed many experiments with reactor pulses as high as 3.5% Ak/k (5.00$) in an 85-element TRIGA core. The measured maximum temperature for the 3.5% Ak/k (5.00$) pulse was 750 C, and the estimated peak transient temperature was 1175 C. Cladding integrity was maintained at peak fuel temperatures as high as 1175*C (GA-4314; GA-6874; Simnad et al. ,1976). Based on the fact that the Technical Specifications for the current operating UT reactor have i a maximum 1.5% Ak/k (2.15$) reactor pulse limit and that the Northrop reac-tor pulses were limited to about 2.1% Ak/k (2.95$), the staff concludes that fuel elements inherited from these two reactors would not have experienced significant internal pressure stresses. (3) Both the original UT reactor core and the Northrop reactor core are cooled by natural convection of light water, so that erosion of fuel cladding as a result of high flow velocity is negligible. High primary water purity is maintained by continuous passage through the filter and demineralizer systems. With technical specification limits to control the conductivity of the primary coolant / moderator water, corrosion of the cladding has been kept to a reasonable minimum. (4) Fuel elements are handled as infrequently as possible, consistent with required surveillance. Any indications of possible damage or degradation are investigated immediately, and damaged fuel is removed from service in accordance with Technical Specifications. All experiments placed near the core are isolated from the fuel cladding by a water gap and at least one barrier or encapsulation. Even if a fuel handling accident, designated as the MHA, does ocdur, the accident analysis in Section 14.1 indicates that the resulting radiation doses would be below the guideline values of 10 CFR 20. On the basis of these considerations, the staff concludes that prior ulitization of certain reactor components does not significantly increase the risk of radia-tion exposure to the public. I 1 I f UT TRIGA Reactor SER 17-2
l 18 CONCLUSIONS On the basis of its evaluation of the application as set forth in this report, the staff has determined that (1) The application for a construction permit and operating license for its research reactor filed by The University of Texas, dated November 1984, as supplemented, complies with the requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's regulations set forth in 10 CFR Chapter I. (2) The facility will be constructed and operated in conformance with the application as supplemented; the provisions of the Act, and the rules and regulations of the Commission. (3) There is reasonable assurance (a) that the activities authorized by the construction permit and operating license can be conducted without endan-gering the health and safety of the public and without undue risk to the environment and (b) that such activities will be conducted in compliance with the regulations of the Commission set forth in 10 CFR Chapter I. (4) The applicant is technically and financially qualified to engage in the activities authorized by the construction permit and operating license in accordance with the regulations of the Commission set forth in 10 CFR Chapter I. (5) The issuance of a construction permit and an operating license for the facility will not be inimical to the common defense and security or to the health and safety of the public. t UT TRIGA Reactor SER 18-1
i I 19 REFERENCES American National Standards Institute /American Nuclear Society (ANSI /ANS) the 15 series. American Nuclear Society (ANS) 15.1',." Standard for the Development of Technical Specifications for Research Reactors," September 1982. .
-- , ANS 15.16, " Standard for Emergency Planning for Research Reactor," Draft 1978 and Draft 2, November 1981. - -- , ANSI /ANS 15.11, " Radiological Control at Research Reactor Facilities,"
1977. Armed Forces Radiology Research Institute (AFRRI), " Final Safeguards Report for the AFRRI TRIGA Reactor," Appendix A, Docket 50-170, November 1960. ! Foushee, F. C. and R. H. Peters, " Summary of TRIGA Fuel Fission Product Release Experiments," Gulf Corporation report Gulf-EES-A10801, San Diego, California (September 1971). General Atomics Company, GA-0471, " Technical Foundations of TRIGA," August 1958. 4 -- , GA-4314, Simnad, M. T., "The U-ZrH x Alloy: Its Properties and Use in TRIGA Fuel," E-117-833, February 1980. -
-- , GA-5400, "Thermionic Research TRIGA Reactor Description and Analysis,"
transmitted by letter dated February 28, 1966 (Docket No. 50-227), Rev. C,
, November 1, 1965. -- , GA-6596, Shoptaugh, J. F., Jr., " Simulated Loss-of-Coolant Accident for TRIGA Reactors," transmitted by letter dated September 22, 1970 (Docket No. 502227). -- , GA-6874, Cof fer, C. 0. , J. R. Shoptaugh, Jr. , and W. L. Whittemore, "Sta-
- bility of the U-ZrH TRIGA Fuel Subjected to Large Reactivity Insertion," trans-Oitted by letter dated July 25, 1967 (Docket No. 50-163), January 1966.
! -- , GA-7882, West, G. B. , W. L. Wittemore, J. R. Shoptaugh, Jr. , J. B. Du, and C. O. Coffer, '.' Kinetic Behavior of TRIGA Reactors," March 1967.
-- , GA-8597, Fouchee, F. C., " Release of Rare Gas Fission Products from U-ZrH Fuel Material," March 1968. -- , GA-9064, West, G. B., " Safety Analysis Report for the Torrey Pines TRIGA
- Mark III Reactor," transmitted by letter dated Janaury 29, 1970 (Docket No. 50-227),
j January 5, 1970. t National Oceanic and Atmospheric Administration, " Local Climatological Data; Annual Summary with Comparative Data 1982," Environmental Data and Information 4 Service, National Climatic Center, Asheville, N.C. UT TRIGA Reactor SER 19-1 _ _ _ _ - _ _ _ _ _ - _ _ _ _ . _ _ 2 -_ _ _ _ ...
' Oregon State University, "SAR for the Oregon State University TRIGA Research Reactor," Docket 50-243 (August 1968).
Simnad, M. T., F. C. Foushee, and G. B. West, " Fuel Elements for Pulsed TRIGA Research Reactors," Nuclear Technology 28, 31-56 (1976). Texas A & M, SAR for the Nuclear Science Center Reactor, Texas A & M University (Docket 50-128), June 1979. Texas Department of Commerce, "1980 Census of Population," Department of Commerce, Bureau of Census, City of Austin Planning Department. U.S. Geological Survey, " Earthquake Information Bulletin," Vol. 9, No. 3, U.S.
- Department of the Interior, May-June 1977.
U.S. Nuclear Regulatory Commission, NUREG-0771, " Regulatory Impact of Nuclear Reactor Accident Source Term Assumptions," For Comment issue, June 1981.
*U.S. GOVERNMENT FRINTING OFFICE: 1985-461 721:20165 e
UT TRIGA Reactor SER- 19 -
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us raver.o o~ ran aman NURGE-1135, i 1 o.u.iiru , u.v. .t m a viru Safety Evaluation Report Related to the Construction Y Pennit and Operating icense for the Research Reactor 'h at The University of xas w/ *, o.
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\ i This Safety Evaluation Report fpr,the appl;' cation filed by The University of Texas a TRIGAfor a construction research reactor has een per/mit prepared and6yoperat"ng the Office oflicense Nuclear to construct and operate Reactor Regulation of the U.S. Nucl f ar Regulatory Contission. The facility is owned and operated by The University /of Texas and is located at the University's Balcones -
Rssearch Center, about 7 iles (11.6 Kilometers) north of the main campus in Austin, " Texas. The staff conel es that the TRIGA reactor facility can be constructed - and operated by The Un safety of the public./ versity of Texas without ' dangering the health and -
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r 21a Construction Permit - Research reactor,1.1 Mw, TRIGA Unlimited J University of Texas ,. ucu. , co.u,,,c.r o~ Operating License ,r~,, ;
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l UNIVED SVATES ,,,,,et,,,,,, 1 NUCLEAR REGULATORY COMMISSION Postaci e rtas raio WASHINGTON, D.C. 20555 o f,',*, "o' c lj Pt RMIT ho G 67 l OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. $300 P 0 g , T
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