It was recognized that the Point Conception area would be a difficult 

 place to work, therefore, backup detection equipment and a much improved 

 on-board instrument shelter were built for this test. While the radiation 

 data collection system worked well, some problems developed. Bouncing of 

 the detector ''ball" as it was towed over the rock outcrops on the beach 

 and offshore bottom caused gain shift and noise in the detectors which 

 necessitated frequent adjustments to the recording instruments. in 

 addition, breaks occurred in the Tygon covering for the cable and allowed 

 water to penetrate the high voltage lines to the detector. The backup 

 detector was utilized during this program so that it could continue to 

 the planned completion stage. 



5. CERC Shore Processes Test Basin, May 1968 



Small quantities of labeled sediment are generally simpler to work 

 with than are large quantities. Logistics and radiation safety are 

 simpler. An excellent way to compare high and low specific activity 

 sand would be a laboratory experiment under controlled conditions that 

 permitted duplication of factors. Such a test at CERC compared results 

 obtained using a large quantity of low specific activity sand with those 

 obtained using a smaller quantity of high specific activity xenonated 

 sand. Total activity remained equal in both instances. Limited test 

 data on beach development and littoral movement under controlled condi- 

 tions were also obtained. The test proved the suitability of xenonated 

 sand for laboratory experiments in beach and nearshore processes. 



Tests were conducted in a flume 68 feet long and 10 feet wide, con- 

 structed in the north part of the CERC Shore Processes Test Basin. The 

 initial beach configuration for each test was essentially a plane beach 

 with a 1:10 slope. The sand was a well-sorted medium quartz sand with 

 an average mean size of 1. 87(f) (.27mm) and a standard deviation of 0.U2. 



Waves were O.k foot high with a period of 1.9 seconds. Each test 

 (low specific activity and high specific activity) comprised a total of 

 22 minutes of wave action. Each test was interrupted after 3 minutes 

 and again after 9 minutes of total wave action to measure changes in 

 beach morphology and radioactivity distribution. The bathymetry of the 

 beach face after 22 minutes of wave action is shown by Figure 51 and the 

 profiles are shown by Figure 52. 



When manufactured on 26 April 1968 , the low specific activity sand 

 had a specific activity of 5-28 microcuries per cubic centimeter; the 

 high specific activity sand had a specific activity of 520 microcuries 

 per cubic centimeter. On 29 April, about 1 liter of low specific activity 

 xenonated sand was emplaced at 0.5-foot intervals, approximating a line 

 source, from stations -1 through +8 along range 5; approximately 50 

 milliliters per interval was used. 



Following this test the radioactive sand was removed and the beach 

 face was rebuilt. On 3 May, about 10 cubic centimeters of high specific 

 activity xenonated sand was emplaced at the same 0.5-foot intervals from 



67 



