Epperson, C. E.

Rhodes, N. R.

UARK (University of Arkansas )

Journal of the Arkansas Academy of Science Volume 44 Article 34 1990 Characterization of Radioactivity in Hot Springs National Park, Arkansas C. E. Epperson University of Arkansas for Medical Sciences N. R. Rhodes University of Arkansas for Medical Sciences Follow this and additional works at: https://scholarworks.uark.edu/jaas  Part of the Geophysics and Seismology Commons Recommended Citation Epperson, C. E. and Rhodes, N. R. (1990) "Characterization of Radioactivity in Hot Springs National Park, Arkansas," Journal of the Arkansas Academy of Science: Vol. 44 , Article 34. Available at: https://scholarworks.uark.edu/jaas/vol44/iss1/34 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This General Note is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu. Proceedings Arkansas Academy of Science, Vol. 44, 1990 125General NotesWhat about the future? We must shift our emphasis from courses that use computers as tools to courses that use computers as an integralpart of the learning process. Cognitive science and neuroscience are being used to create new models that can be used to analyze the behaviorof students in problem solving. We need to find ways to combine the computing power available in the new microcomputers with this model toimprove our educational techniques.The latest revolution in microprocessors has been used to create computers that look like a PC but have the multi-tasking multi-user capabilityof mini computers and main frame computers. To utilize fully these capabilities, advanced operating systems such as OS/2 or UNIXmust be used.Evolutionary and revolutionary changes in computers are occurring so rapidly that many educators and educational institutions have been unableto utilize fully the phenomenal computing power that is available today. As educators, we need to find ways to use these new computers as anintegral part of the learning process.ROBERT L.DOUGLAS, Computer and Electronics Engineering Technology, HerffCollege ofEngineering, Memphis State University, Memphis,TN38152.CHARACTERIZATION OF RADIOACTIVITYINHOT SPRINGS NATIONALPARK, ARKANSASThe objective of this study was to determine the types and measure the levels of radioactive emissions found within the Hot Springs NationalPark boundaries. The study should help determine ifthe emissions pose a significant health hazard to the public or to park workers.The thermal springs of the Hot Springs National Park at Hot Springs, Arkansas, are radioactive. These springs have been a natural resourceof international renown for many years. Many tourists are attracted to the spa city and visit the park each year.The National Park is nestled in the eastern portion of the Ouachita Mountains in west Central Arkansas. The springs emerge in a compactbelt about one-fourth mile long and a few hundred feet wide, along the southwestern slope of Hot Springs Mountain. Excavation and coveringof springs, to increase and concentrate flows, have reduced the number ofspring openings from 72 to less than 40. Each spring opening is complete-ly encased inmetal and concrete and capped witha gas-tight metal hatch. A gravity collecting system (Figure 1) channels the flow of the springsto a central reservoir (Hanor, 1980), from which the water is redistributed to individual bathhouses and to public drinking fountains (Bedinger,et al., 1979).Figure 1. Distribution of the springs and bathhouses. Measured exposure rates of springs are depicted by geometric symbols. Units are /*Rh-'.The combined flow of the hot springs is currently about 670,000 gallons per day. The flow of the springs is highest in the winter and springand is lowest in the summer and fall. While the temperature of individual springs may vary, the temperature of the combined hot springs watersis about 62°C.The radioactivity of the hot springs waters is due mostly to dissolved radon and radon daughters with a small contribution from radium.USEPA reported a radium concentration in the waters of2.1 ± 0.22 pCi L'(Bedinger, et al., 1979). The radon concentration of 25 hot springsranged from 140 to 30,500 pCi L-> with a model value of 820 pCi L' (Kuroda, 1953).Radon concentrations were measured using passive alpha track monitors (ATM)(Ronca-Batista and Magno, 1988) and, insome cases, ac-tivated charcoal (AC) canisters (Gray and Windham, 1987). A pressurized ion chamber (PIC) and environmental thermoluminescent dosimeters(TLD) were used to make differential and integral exposure measurements of radon daughters. Gamma ray identities were confirmed using a port-able multichannel analyzer (MCA) witha sodium iodide probe. Aproportional probe and counter were used for charged particle detection. Severalconsecutive PIC readings were taken and averaged for each measurement. ATMs and TLDs were left in place for at least 90 days. AC canisterswere placed for 48 hour periods. Some measurements have been made year round over the past 2 years.External gamma fields were measured by placing the PIC indirect contact with spring covers or as close as possible to the region of interest.A map of the area and the exposure levels are shown in Fig. 1. The springs are numbered according to the Park Service's system. The largestexposure rates were observed from springs located at higher elevations. Rates decrease considerably at lower levels. This is probably due to themigration of radon gas back up the gravity collection system to higher elevations.125Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34Published by Arkansas Academy of Science, 1990Arkansas Academy of ScienceA highly localized area ofrelatively intense gamma radiation was found at an abandoned spring site on the upper slopes. This was the formersite of the Ral Spring (#14). The spring has been filledin withgravel and soil. The reason for the unusually high exposure rate at this particularspot is presently unknown.A portable shelter was erected at the Ral spring site to protect monitors and instruments from rain. The low levels of radon and abundanceofgammas (Table 1 and 2) indicate that the activity is below ground. This area is an external, not internal hazard. The 2 tables illustrate the reasonablygood agreement between different monitoring methods for radon and for daughters.An ATMand a TLD were placed side by side in each bathhouse basement for 110 days. Short term PIC readings were taken at the samelocation and averaged. The results are displayed in Table 3.Allbathhouses except one, the Buckstaff, are closed. Elevated radiation readings were found in those basements with flowingsprings thatleaked or seeped onto the basement floor. Radon levels were surprisingly low, since the bathhouses were sealed and had little or no ventilation.Family dwellings and other buildings within the reservation were assayed in the same manner as before. Results are tabulated in Table 4.The Park Service ranger station basement was found to be slightly elevated in radon levels.Table 1.Outdoor Measurements of Radon Over Inactive Spring (Ral) Table 2. Outdoor Measurements of Gamma Rays Over Inactive Spring(Ral)Measurement Charcoal Adsorption Alpha Track easuremenv _. T- 1 r Number uR h mremNumber pCi L1- 3.4 2.5 i, 326 8882. 3.4 2.0 2. 316 925Average 3.4 2.25 Average 321c 907a Instantaneous rates measured over a few minutesb Integrated over 110 daysc 321 uR h"' = 847 mR over 110 daysTable 3. Results Obtained from Spa Bath House Basement Table 4. Results Obtained from Basements of Family Dwellings andMeasurements Buildings Within ReservationRadon b TLDC PIC dBath house pCi L"'mrad uR h~' "" ""Radon* TLDa>b PIC CLamar 3.1 30 9.6 Location pCi L"'mrad uR h"'Buckstaff 3.8 40 6.8 Ranger Station 5.1 42 10.3Ozark 8.3 30 12.0 Dwelling 1 2.6 47 9.8Quapaw 3 8.0 87 60.0 Dwelling 2 2.5 46 10.5Fordyce a 1.3 49 13.2 Dwelling 3 2.0 42 10.2Maurice 3 2.7 30 6.7 Health Club 1.5 37 7.4Hale a 43.7 49 20.3 Visitor's Center 1.5 55 10.0Superior a 9.9 52 12.5 Maintenance Shop 0.8 36 7.9a Active spring in basement. "Integrated over 110 daysb 110 day alpha track monitors. bThis includes an average TLD background of 30 mradsc 110 day thermoluminescent gamma monitors. cInstantaneous rates measured over a few minutesThese include normal backuround of about 30 mrads.d Averaged instantaneous exposure rates measured over a few minutes.The effect of exposing thermal spring enclosures to the ambient atmosphere is demonstrated in Table 5. Initiallythe exposure rates of 3 springswere measured with the PIC in contact with the spring covers. Two of the spring covers were then removed, exposing the spring opening to theoutside atmosphere. After 1 hour, the covers were replaced and exposure rates re-measured. Two days later the readings were back to normal.The results indicate that once disturbed, equilibria between radon gas and radon daughter plateout under the spring hatch lid is quickly restored.The exposure rates measured at various times during a year are shown in Table 6. Radioactivity appears to decrease somewhat during thecolder months. More likely, this reflects the seasonal decrease in spring flow rates. Repeat measurements are very consistent.Salient observations from this study include the following:—Radon levels indwellings and other park buildings are below any current action level.—Bathhouse basements have some potential for becoming hazardous but this can probably be remedied with ventilation and sealing of cracks.—The highest external exposures exist over and immediately adjacent to thermal spring openings.126 Proceedings Arkansas Academy of Science, Vol. 44, 1990 126Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34https://scholarworks.uark.edu/jaas/vol44/iss1/34Proceedings Arkansas Academy of Science, Vol. 44, 1990 127General Notes—Essentially all spa areas were found to be well within acceptable radiation exposure limits.—Radon and daughters comprise essentially all of the radioactivity present in the park.—Dried up springs no longer emit gamma rays. The presence of water is evidently necessary for gamma emissions to exist.Table 5. PIC Reading Over Hatch Covers-Before and After OpeningyR h'1Spring Before Hatch After Hatcha 48 hoursNumber Removal Replacement Later5. 133 65 1367. 189 b 1908. 151 55 161Table 6. PIC Measurements at Spring Hatch Covers Across TimeSpring NumberDate //5 11/ IIHiR h"1July 1987 1V2 185Oct 1987 lit. 16 1Nov 1987 119 171Feb 1988 I1') 158a Spring was opened to ambient atmosphere for one hour beforereplacing hatch cover.Apr 1988 122 16/.Hatch not removed. May 1988 L33 18<) 151May 1988 136 I'll) 16]No reading takenLITERATURE CITEDBEDINGER, M.S., F.J. PEARSON, JR., J.E. REED, R.T.SNIEGOCKI, and C.G. STONE. 1979. The waters of Hot SpringsNational Park, Arkansas -their nature and origin.U.S. Dept. In-terior, Geological Survey Professional Paper 1044-C:4-25.HANOR, J.S. 1980. Fire in folded rocks. Eastern National Park andMonument Association. 42 pp.KURODA, P.K. 1953. Radioactivity tables of some natural waters.University ofArkansas Institute of Science and Technology. 58 pp.GRAY, D. and S. WINDHAM. 1987. EERF standard operatingprocedures for radon-222 measurement using charcoal canisters.USEPA. 30 pp.RONCA-BATTISTA, M. and P. MAGNO. 1988. Standard measure-ment techniques for indoor Rn-222 measurements. Health Physics.55:67-69.C.E. EPPERSON and N.R. RHODES, University of Arkansas for Medical Sciences, College ofPharmacy, 4301 West Markham, Little Rock,AR 72205.STATUS OF THE ACCELERATOR PROJECT AT U.C.A.A 2.5 MV Van de Graaff accelerator is being installed in a new facility at the University of Central Arkansas. The accelerator and someancillary hardware was donated to the school approximately 10 years ago, while the area in the building became available almost 4 years ago.The accelerator itself is one of many variants in a series produced by High Voltage Engineering Corporation. Builtin the late 1950's, it haspassed through several institutional hands in the interim, but has acquired relatively little actual running time. It was originally intended for usewitha negative terminal potential to accelerate electrons, as part ofan industrial X-ray system. Our use for the machine has required a conversiontopositive terminal operation to produce positive ion beams. Amore detailed discussion of these modifications and the installation to date appears below.The laboratory housing the accelerator was designed expressly for that purpose as part of an addition to the science building completed in1986. Itconsists of 4 rooms on the main (upper) floor of the building and one large room below them. Figure 1 shows a plan view of the upperfloor area and Fig. 2 shows the lower room.InFig. 1 we see 2 primary rooms, the control room and the accelerator vault. The control room is outside the curved shield wall of the vault;it houses the control console for the machine as well as providing space for data acquisition equipment. The 2 smaller rooms to the left of thevault will provide office and research area to faculty and students using the machine.The accelerator vault is 7.9 m in diameter and is enclosed by a high density concrete radiation shield wall; this room and the entire lowerroom, equally shielded, constitute the high radiation area of the laboratory. This area is protected against entry when radiation may be producedby a system of interlocks on all entrances.The accelerator is mounted vertically at the vault center so that the beam will immediately exit into the target room below. The machine'sbaseplate (A) is shown in Fig. 1, and is approximately 1.2 m square. The accelerator pressure tank stands roughly 2.4 m high and is removed andinstalled with an overhead track crane. A floor slot (B) allows crane access to the target room below. A large conduit (C) carries control cablesfrom the machine baseplate to the console (D). Gas storage and piping equipment for the insulating tank gas willbe installed in the vault.A stairway leads down to the target room, which occupies the area below all of the upper floor rooms plus a short extension to the west.The target room willcontain all of the beam handling system as well as the experimental areas. A wide door on the lower floor allows access forlarge equipment. A corner of the room houses a shielded neutron irradiation source for use in student experiments.127Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34Published by Arkansas Academy of Science, 1990

English

Characterization of Radioactivity in Hot Springs National Park, Arkansas

ScholarWorks@UARK

Journal of the Arkansas Academy of ScienceVolume 44 Article 341990Characterization of Radioactivity in Hot SpringsNational Park, ArkansasC. E. EppersonUniversity of Arkansas for Medical SciencesN. R. RhodesUniversity of Arkansas for Medical SciencesFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Geophysics and Seismology CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This General Note is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the ArkansasAcademy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact ccmiddle@uark.edu, drowens@uark.edu,scholar@uark.edu.Recommended CitationEpperson, C. E. and Rhodes, N. R. (1990) "Characterization of Radioactivity in Hot Springs National Park, Arkansas," Journal of theArkansas Academy of Science: Vol. 44 , Article 34.Available at: http://scholarworks.uark.edu/jaas/vol44/iss1/34Proceedings Arkansas Academy of Science, Vol. 44, 1990 125General NotesWhat about the future? We must shift our emphasis from courses that use computers as tools to courses that use computers as an integralpart of the learning process. Cognitive science and neuroscience are being used to create new models that can be used to analyze the behaviorof students in problem solving. We need to find ways to combine the computing power available in the new microcomputers with this model toimprove our educational techniques.The latest revolution in microprocessors has been used to create computers that look like a PC but have the multi-tasking multi-user capabilityof mini computers and main frame computers. To utilize fully these capabilities, advanced operating systems such as OS/2 or UNIXmust be used.Evolutionary and revolutionary changes in computers are occurring so rapidly that many educators and educational institutions have been unableto utilize fully the phenomenal computing power that is available today. As educators, we need to find ways to use these new computers as anintegral part of the learning process.ROBERT L.DOUGLAS, Computer and Electronics Engineering Technology, HerffCollege ofEngineering, Memphis State University, Memphis,TN38152.CHARACTERIZATION OF RADIOACTIVITYINHOT SPRINGS NATIONALPARK, ARKANSASThe objective of this study was to determine the types and measure the levels of radioactive emissions found within the Hot Springs NationalPark boundaries. The study should help determine ifthe emissions pose a significant health hazard to the public or to park workers.The thermal springs of the Hot Springs National Park at Hot Springs, Arkansas, are radioactive. These springs have been a natural resourceof international renown for many years. Many tourists are attracted to the spa city and visit the park each year.The National Park is nestled in the eastern portion of the Ouachita Mountains in west Central Arkansas. The springs emerge in a compactbelt about one-fourth mile long and a few hundred feet wide, along the southwestern slope of Hot Springs Mountain. Excavation and coveringof springs, to increase and concentrate flows, have reduced the number ofspring openings from 72 to less than 40. Each spring opening is complete-ly encased inmetal and concrete and capped witha gas-tight metal hatch. A gravity collecting system (Figure 1) channels the flow of the springsto a central reservoir (Hanor, 1980), from which the water is redistributed to individual bathhouses and to public drinking fountains (Bedinger,et al., 1979).Figure 1. Distribution of the springs and bathhouses. Measured exposure rates of springs are depicted by geometric symbols. Units are /*Rh-'.The combined flow of the hot springs is currently about 670,000 gallons per day. The flow of the springs is highest in the winter and springand is lowest in the summer and fall. While the temperature of individual springs may vary, the temperature of the combined hot springs watersis about 62°C.The radioactivity of the hot springs waters is due mostly to dissolved radon and radon daughters with a small contribution from radium.USEPA reported a radium concentration in the waters of2.1 ± 0.22 pCi L'(Bedinger, et al., 1979). The radon concentration of 25 hot springsranged from 140 to 30,500 pCi L-> with a model value of 820 pCi L ' (Kuroda, 1953).Radon concentrations were measured using passive alpha track monitors (ATM)(Ronca-Batista and Magno, 1988) and, insome cases, ac-tivated charcoal (AC) canisters (Gray and Windham, 1987). A pressurized ion chamber (PIC) and environmental thermoluminescent dosimeters(TLD) were used to make differential and integral exposure measurements of radon daughters. Gamma ray identities were confirmed using a port-able multichannel analyzer (MCA) witha sodium iodide probe. Aproportional probe and counter were used for charged particle detection. Severalconsecutive PIC readings were taken and averaged for each measurement. ATMs and TLDs were left in place for at least 90 days. AC canisterswere placed for 48 hour periods. Some measurements have been made year round over the past 2 years.External gamma fields were measured by placing the PIC indirect contact with spring covers or as close as possible to the region of interest.A map of the area and the exposure levels are shown in Fig. 1. The springs are numbered according to the Park Service's system. The largestexposure rates were observed from springs located at higher elevations. Rates decrease considerably at lower levels. This is probably due to themigration of radon gas back up the gravity collection system to higher elevations.125Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34Published by Arkansas Academy of Science, 1990Arkansas Academy of ScienceA highly localized area ofrelatively intense gamma radiation was found at an abandoned spring site on the upper slopes. This was the formersite of the Ral Spring (#14). The spring has been filledin withgravel and soil. The reason for the unusually high exposure rate at this particularspot is presently unknown.A portable shelter was erected at the Ral spring site to protect monitors and instruments from rain. The low levels of radon and abundanceofgammas (Table 1 and 2) indicate that the activity is below ground. This area is an external, not internal hazard. The 2 tables illustrate the reasonablygood agreement between different monitoring methods for radon and for daughters.An ATMand a TLD were placed side by side in each bathhouse basement for 110 days. Short term PIC readings were taken at the samelocation and averaged. The results are displayed in Table 3.Allbathhouses except one, the Buckstaff, are closed. Elevated radiation readings were found in those basements with flowingsprings thatleaked or seeped onto the basement floor. Radon levels were surprisingly low, since the bathhouses were sealed and had little or no ventilation.Family dwellings and other buildings within the reservation were assayed in the same manner as before. Results are tabulated in Table 4.The Park Service ranger station basement was found to be slightly elevated in radon levels.Table 1.Outdoor Measurements of Radon Over Inactive Spring (Ral) Table 2. Outdoor Measurements of Gamma Rays Over Inactive Spring(Ral)Measurement Charcoal Adsorption Alpha Track easuremenv _. T-1r Number uR h mremNumber pCi L1- 3.4 2.5 i, 326 8882. 3.4 2.0 2. 316 925Average 3.4 2.25 Average 321 c 907a Instantaneous rates measured over a few minutesb Integrated over 110 daysc 321 uR h"' = 847 mR over 110 daysTable 3. Results Obtained from Spa Bath House Basement Table 4. Results Obtained from Basements of Family Dwellings andMeasurements Buildings Within ReservationRadon b TLDC PIC dBath house pCi L"'mrad uR h~' "" ""Radon* TLDa>b PIC CLamar 3.1 30 9.6 Location pCi L"'mrad uR h"'Buckstaff 3.8 40 6.8 Ranger Station 5.1 42 10.3Ozark 8.3 30 12.0 Dwelling 1 2.6 47 9.8Quapaw 3 8.0 87 60.0 Dwelling 2 2.5 46 10.5Fordyce a 1.3 49 13.2 Dwelling 3 2.0 42 10.2Maurice 3 2.7 30 6.7 Health Club 1.5 37 7.4Hale a 43.7 49 20.3 Visitor's Center 1.5 55 10.0Superior a 9.9 52 12.5 Maintenance Shop 0.8 36 7.9a Active spring in basement. "Integrated over 110 daysb 110 day alpha track monitors. bThis includes an average TLD background of 30 mradsc 110 day thermoluminescent gamma monitors. cInstantaneous rates measured over a few minutesThese include normal backuround of about 30 mrads.d Averaged instantaneous exposure rates measured over a few minutes.The effect of exposing thermal spring enclosures to the ambient atmosphere is demonstrated in Table 5. Initiallythe exposure rates of 3 springswere measured with the PIC in contact with the spring covers. Two of the spring covers were then removed, exposing the spring opening to theoutside atmosphere. After 1 hour, the covers were replaced and exposure rates re-measured. Two days later the readings were back to normal.The results indicate that once disturbed, equilibria between radon gas and radon daughter plateout under the spring hatch lid is quickly restored.The exposure rates measured at various times during a year are shown in Table 6. Radioactivity appears to decrease somewhat during thecolder months. More likely, this reflects the seasonal decrease in spring flow rates. Repeat measurements are very consistent.Salient observations from this study include the following:—Radon levels indwellings and other park buildings are below any current action level.—Bathhouse basements have some potential for becoming hazardous but this can probably be remedied with ventilation and sealing of cracks.—The highest external exposures exist over and immediately adjacent to thermal spring openings.126 Proceedings Arkansas Academy of Science, Vol. 44, 1990 126Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34http://scholarworks.uark.edu/jaas/vol44/iss1/34Proceedings Arkansas Academy of Science, Vol. 44, 1990 127General Notes—Essentially all spa areas were found to be well within acceptable radiation exposure limits.—Radon and daughters comprise essentially all of the radioactivity present in the park.—Dried up springs no longer emit gamma rays. The presence of water is evidently necessary for gamma emissions to exist.Table 5. PIC Reading Over Hatch Covers - Before and After OpeningyR h'1Spring Before Hatch After Hatcha 48 hoursNumber Removal Replacement Later5. 133 65 1367. 189 b 1908. 151 55 161Table 6. PIC Measurements at Spring Hatch Covers Across TimeSpring NumberDate //5 11/ IIHiR h"1July 1987 1V2 185Oct 1987 lit. 16 1Nov 1987 119 171Feb 1988 I1') 158a Spring was opened to ambient atmosphere for one hour beforereplacing hatch cover. Apr 1988 122 16/.Hatch not removed. May 1988 L33 18<) 151May 1988 136 I'll) 16]No reading takenLITERATURE CITEDBEDINGER, M.S., F.J. PEARSON, JR., J.E. REED, R.T.SNIEGOCKI, and C.G. STONE. 1979. The waters of Hot SpringsNational Park, Arkansas -their nature and origin.U.S. Dept. In-terior, Geological Survey Professional Paper 1044-C:4-25.HANOR, J.S. 1980. Fire in folded rocks. Eastern National Park andMonument Association. 42 pp.KURODA, P.K. 1953. Radioactivity tables of some natural waters.University ofArkansas Institute of Science and Technology. 58 pp.GRAY, D. and S. WINDHAM. 1987. EERF standard operatingprocedures for radon-222 measurement using charcoal canisters.USEPA. 30 pp.RONCA-BATTISTA, M. and P. MAGNO. 1988. Standard measure-ment techniques for indoor Rn-222 measurements. Health Physics.55:67-69.C.E. EPPERSON and N.R. RHODES, University of Arkansas for Medical Sciences, College ofPharmacy, 4301 West Markham, Little Rock,AR 72205.STATUS OF THE ACCELERATOR PROJECT AT U.C.A.A 2.5 MV Van de Graaff accelerator is being installed in a new facility at the University of Central Arkansas. The accelerator and someancillary hardware was donated to the school approximately 10 years ago, while the area in the building became available almost 4 years ago.The accelerator itself is one of many variants in a series produced by High Voltage Engineering Corporation. Builtin the late 1950's, it haspassed through several institutional hands in the interim, but has acquired relatively little actual running time. It was originally intended for usewitha negative terminal potential to accelerate electrons, as part ofan industrial X-ray system. Our use for the machine has required a conversiontopositive terminal operation to produce positive ion beams. Amore detailed discussion of these modifications and the installation to date appears below.The laboratory housing the accelerator was designed expressly for that purpose as part of an addition to the science building completed in1986. Itconsists of 4 rooms on the main (upper) floor of the building and one large room below them. Figure 1 shows a plan view of the upperfloor area and Fig. 2 shows the lower room.InFig. 1 we see 2 primary rooms, the control room and the accelerator vault. The control room is outside the curved shield wall of the vault;it houses the control console for the machine as well as providing space for data acquisition equipment. The 2 smaller rooms to the left of thevault will provide office and research area to faculty and students using the machine.The accelerator vault is 7.9 m in diameter and is enclosed by a high density concrete radiation shield wall; this room and the entire lowerroom, equally shielded, constitute the high radiation area of the laboratory. This area is protected against entry when radiation may be producedby a system of interlocks on all entrances.The accelerator is mounted vertically at the vault center so that the beam will immediately exit into the target room below. The machine'sbaseplate (A) is shown in Fig. 1, and is approximately 1.2 m square. The accelerator pressure tank stands roughly 2.4 m high and is removed andinstalled with an overhead track crane. A floor slot (B) allows crane access to the target room below. A large conduit (C) carries control cablesfrom the machine baseplate to the console (D). Gas storage and piping equipment for the insulating tank gas willbe installed in the vault.A stairway leads down to the target room, which occupies the area below all of the upper floor rooms plus a short extension to the west.The target room willcontain all of the beam handling system as well as the experimental areas. A wide door on the lower floor allows access forlarge equipment. A corner of the room houses a shielded neutron irradiation source for use in student experiments.127Journal of the Arkansas Academy of Science, Vol. 44 [1990], Art. 34Published by Arkansas Academy of Science, 1990

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Characterization of Radioactivity in Hot Springs National Park, Arkansas

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