Establishment of a NORM baseline for selected seafood in the Gulf of Mexico.

Naturally occurring radioactive material was characterized in selected seafood samples from three areas in the Gulf of Mexico. Relatively desirable and abundant fish such as Red Snapper, Red Drum, Northern Whiting, and Spotted Trout as well as oysters were collected and analyzed using gamma spectroscopy to determine the concentration of 228Ra, 226Ra, and 40 K. Average total activity concentration from these radionuclides were 0.9 ±â€¯0.6, 1.6 ±â€¯1.2, and 132 ±â€¯57 Bq kg-1 respectively, in the edible portion of wet weight samples. The results were consistent with previous studies for other bodies of water. A small but statistically significant increase in 226Ra was found in comparison to similar research performed 20 years prior. These measurements provide a reasonable baseline for the examined species from the Gulf of Mexico.

Determination of Uranium Series Activity Before Secular Equilibrium Is Established.

Timely achievement of uranium series' secular equilibrium is not always feasible. Our objective is to mathematically justify methods for early uranium series gamma spectroscopy measurements that can accurately predict naturally occurring radioactive material equilibrium activities long before equilibrium is established. It was believed that, regardless of prior Rn escape, after sealing a sample for a few hours the activities of Rn, Ra, and U could theoretically be determined with a single measurement of both Pb and Bi. However, when accounting for error, this theory did not work as expected (CV = 14.0 in Ra simulation). A similar approach published by Li et al. in 2015 proved to be much more reliable with the error considered, using Pb activities measured at two different times gave significantly improved results when tested the same way (CV = 0.29 in Ra simulation). Because both Pb and Bi activities are typically available when using gamma spectrometry, we combine these approaches and further increased the accuracy of the calculated activities (CV = 0.21 in Ra simulation).

Visualizing High-Order Decay after Disequilibria.

High-order decay equations are often difficult to study without significant care taken with variables and assumptions. As parent and progeny activities evolve over time, the effects of uncertainties and approximations confound the quality and interpretation of results. Of particular concern is the situation when decay equilibrium has been disturbed and progenies have arbitrary initial activities. To address this, code was created using Wolfram Mathematica to visualize the time-activity plots of the high order progenies of naturally occurring radioactive material after secular equilibrium is disturbed. The Bateman equation for an un-replenished parent was expanded to calculate activity vs. time for up to 13 progenies at different initial activities. The code uses the formula of Skrable et al., without parent production, expanded to the 13th progeny with arbitrary initial concentration. The code calculates and plots activity vs. time; it also reports the cumulative disintegrations of each progeny over a user-specified time period for comparison to counting measurements. The code could also be modified to incorporate additional production or branched decay schemes. We believe this code may be useful to health physicists and is intended to be accessible for anyone's use. This paper presents the code with explanations and examples on how to use it.