All Radiochemistry lab results are now available in electronic form, if requested. The electronic format we use is a Excel Spreadsheet based on the EPA Manual entitled “Electronic data Deliverable (EDD) Comprehensive Specification Manual 4.0” dated March 2016. Call with any questions.
This is a fun lab used in our classes that you can do from a home computer.
Let’s say you have been tasked with making a direct radiation measurement of the exposure rate from a bucket of rocks for health and safety purposes. The rocks are believed to be from the Breccia Pipe formation in the South Rim of the Grand Canyon known as the Orphan Lode.
The first thing we have to do is select a survey instrument that is appropriate for this type of measurement. The meter should respond to photon radiations linearly over the range of energies that we anticipate from a natural uranium ore. Below is a high resolution gamma spectrum from a rock taken from the same ore body.
As you can see, there are many photons at different energies from the uranium daughters in the natural chain. Most of the energies, though, are from 80 keV to about 800 keV. The instrument should respond linearly and accurately over this range as a minimum.
On the shelf, we have three meters calibrated in mR/hr, the Ludlum Model 19 MiroR meter, the Ludlum 44-9 Pancake probe geiger counter, and the Ludlum Model 9 pressurized ion chamber. Now let’s look at the response of these meters and select one that is appropriate. Since this is a common task, Ludlum has made it easy for us by putting the response curves for all of their instruments on one page. See:
Now look at the curves for the different instruments that are available.
First look at the curve for the Model 19 microR meter.
Does this meter respond linearly and accurately (1.0) for the energy range we need?
If not, will it over-respond or under-respond?
Is it suitable for health and safety measurements?
Now look at the Model 44-9:
Will this meter respond correctly? If not, will it over-respond or under-respond?
Lastly, look at the Model 9 ion chamber:
Is this meter suitable for our health and safety measurement?
In the articles about the buckets of rocks in the Grand Canyon Museum, the staff used the Model 19 (apparently reading the microR scale as mR/hr), and the 44-9. They did not use the Model 9 ion chamber.
Are their measurements meaningful? If you visited the museum were you “overexposed”?
Natural uranium and thorium chain radionuclides are natural, and are a part of all soils and building materials at widely varying concentrations. To learn more about the natural decay chains see:
Recent news articles claim that two buckets of rocks at the Grand Canyon Museum “overexposed” visitors to radiation. We have made radiation measurements in and around the Grand Canyon over the last two decades and routinely analyze water and soil samples from the area. We can say with assurance, that the exposure rates quoted in the article are preposterous. Natural sources, like uranium ores, don’t produce external dose rates anywhere near the values shown in the article. Even the background reading of 2 mR/hr outside of the building was impossibly high. Background in the area is 4 to 20 microR/hr. The person making the radiation measurements either chose an instrument that was not appropriate for measuring exposure rates from uranium ores, or simply read the meter incorrectly (e.g. reported mR/hr when the meter was a microR/hr meter). Most likely, he did both.
Radiation Safety Engineering, Inc has been verified through the VA to be a Veteran Owned Small Business. See the determination letter.
The American Academy of Health Physics (AAHP) has approved the Radiation Safety Officer Course offered periodically throughout the year, for 24 CE credits. The approval ID Number is 2018-00-059.
Two papers in J. Radioanalytical and Nuclear Chemistry were just published by Dr. Metzger and his colleagues. The first paper covers the measurement and the dosimetry of long-lived contaminants in cyclotron produced radiopharmaceuticals. The second describes the interaction these contaminants have with the ubiquitous homeland security radiation monitors and their potential impact for patients who have had diagnostic studies.
The links to the papers are:
There has been a tremendous technological advancement in life-saving cardiac and interventional radiology procedures performed under fluoroscopic guidance. These procedures, such as TAVRS (see https://www.youtube.com/watch?v=csxJYTLXNJY), provide life-saving benefits to the patients, but can be long and complex, and result in high radiation doses to the cardiologists and radiologists performing the procedures. Doses to the head and neck, which are outside of the protective lead apron, are monitored with a collar badge attached to the top of the apron. These badge results are now over 1 rad per month in many institutions, and are climbing due to the demand for these new procedures.
The most sensitive organ in the head and neck is the lens of the eye, where radiogenic cataract formation can occur after a threshold dose is received. The current limit for eye dose is 15 rads per year, which is based on a threshold dose of 500 rads for cataract formation. Recent epidemiological studies suggest that the actual threshold is less than 500 rads, and the International Commission on Radiological Protection (ICRP) has recommended a lower threshold dose, and head and neck limit. Forcing the dose lower by regulatory means is not desirable, as any adversarial regulatory action that reduced the availability or accessibility to the new life-saving procedures would necessarily cost human life in the vulnerable patient population. A shielding plan to protect the cardiologists and interventional radiologists is needed.
The only shielding available to the cardiologists and radiologists are various types of shadow shields which must be positioned correctly to reduce the head and neck dose. While essentially all hospitals and outpatient clinics equipped with cath labs to perform these procedures offer some kind of shadow shielding, it is only rarely positioned and used optimally.
Dr. Metzger has produced a Monte Carlo model of a cath lab and a special procedures room that allows the efficacy of the various shadow shields available in a facility to be evaluated prior to a specific procedure. The dose reduction possible with each shadow shield and any combination of the shields can be modeled and determined before the start of the procedure.
Ga-68 for PET imaging is now available in a generator form from Eckert and Ziegler. As with all generators, there is always a possibility of some of the radionuclide held on the column (Ge-68) breaking through into the eluate (Ga-68) needed for imaging. A breakthrough test is needed with a limit of 0.001% or less of the Ge-68 parent in the Ga-68 eluate. We have recently developed an inexpensive test using high resolution gamma spectroscopy. Call for more details.
Long-lived contaminants are introduced into cyclotron produced radiopharmaceuticals from the activation and spallation of elements in the HAVAR target window into the target water. They are removed during the synthesis of the final imaging agent. Below, are a series of papers on the measurement of these contaminants, their retention in the body, and the dose delivered to the patient from them. The quantity of the contaminants is strictly controlled by the FDA which requires all drugs be 99.5% pure. The vast majority of prepared radiopharmaceuticals have only a tiny fraction of the allowed levels in them. The radiation dose these contaminants deliver to the patient, if present, is trivial.
They do, however, outlive the imaging isotope (typically F-18) and may alarm Homeland Security detectors found in many locations. The length of time these isotopes can alarm the detectors will be determined and published in the near future.
Keith Eckerman and Richard Leggett have provided uptake retention functions for soluble injected forms of each possible contaminating isotope and these tables are also presented in the link above.
Dr. Robert Metzger of Radiation Safety Engineering, Inc. is pleased to be presenting 3 papers at next weeks ICRS-13 / RSPD-2016 joint conference in Paris, France.
Below are links to each of the 3 papers.
- Uranium, radium and thorium in soils with high-resolution gamma spectroscopy, MCNP-generated efficiencies, and VRF non-linear full-spectrum nuclide shape fitting.