Section IV. PROGRAM SUMMARY 



1. Hardware and Program Development 



Xenon-133 is the only isotope used to date. This biologically in- 

 active isotope is diffused into the quartz sand grains at high tempera- 

 ture and low pressure. Tests indicate that this process does not affect 

 the hydraulic characteristics of the grain. As indicated by studies at 

 NRDL, there is little loss of xenon due to leaching and abrasion. Because 

 of degassing, the half life of tagged particles used in early studies was 

 2.7 days as opposed to 5.3 days for xenon-133. However, this problem 

 has been nearly eliminated and the halflife for the tagged particle is 

 now approximately 5.0 days. 



An apparatus capable of placing the tagged sand on the bottom in 

 deep water or in relatively shallow water of the breaker zone was re- 

 quired. The initial device was a cylindrical hopper which could be used 

 to emplace a slurry of tagged sand as either a point source or line 

 source. However, the sand clogged on occasion when it got wet in the 

 hopper. A springloaded clamshell device which opened upon contacting 

 the bottom proved effective for placing sand as a point source. 



The detection system consists of an on-board data collection system 

 and a towed ball-like device which houses four cesium iodide crystals 

 (scintillation detectors). Tests indicate that this ball design will 

 track well at speeds up to 5 knots with the present cable configuration. 

 As built, the device works 'to depths of 200 feet (about 6 atmospheres). 

 Electrical signals from the detectors are carried to a signal mixer on 

 the towing vehicle and then to a UoO-channel analyzer. By means of a 

 program interrogator, other data pertinent to surveying are coordinated 

 with the radiation data and read into the data display. 



Tagged sand is traced by towing the detector ball behind an am- 

 phibious vehicle. Navigational control uses a navigation system which 

 provides direct readout of distance in meters from two responder beacons 

 at established shore points. Position information and radiation data 

 are printed out simultaneously. Soundings are taken with a precision 

 fathometer located on board the amphibious vehicle. 



Computer programs have been developed for processing the raw field 

 data. Radioactivity data is corrected for background and decay; position 

 data is corrected to indicate the location of the ball behind the am- 

 phibious vehicle. These data are subsequently read into memory, and an 

 additional program plots and posts the corrected data. Isoactivity con- 

 tour maps (trend surface) of gridded data may be made by a Fourier 

 transform program. 



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