Fiestaware - Natural vs Depleted Uranium - Seriously This Time
Posted: 20 Jan 2020, 02:19
Today’s post is about the world famous Fiestaware, a line of ceramic glazed dinnerware manufactured in the United States since 1936, with a hiatus between 1973 and 1985.
According the New York Times “Fiestaware is the most collected brand of china in the United States. It's also the No. 1 selection for casual dinnerware in American bridal registries”.
[broken link removed - Steven]
The reason such an object is interesting to someone into gamma spectroscopy and radiation detection in general is that the red "Fiestas" pieces manufactured up until 1973 had Uranium Oxide in their glaze so they were pretty radioactive.
Between 1936 and 1943 Natural Uranium was used. Then, during WWII, the Manhattan Project started, the US government took control of Uranium and confiscated the company’s stocks of Uranium. The production of the red Fiestas stopped and only resumed in 1959, this time using depleted rather than natural Uranium.
In both cases the Uranium was chemically refined, so it did not contain all the products of the decay chain like Radium, Lead and Bismuth. Allegedly only the first isotope of the decay chain is present: Thorium 234, but the second makes an appearence here as well.
The difference between the pre-war and post-war pieces is the presence of Uranium 235, a lot more prominent in the pre-war pieces, containing natural Uranium.
I already posted a Fiestaware thread, but back then I had a few misconceptions about a thing or two.
viewtopic.php?f=5&t=522
To start with, the thread title was wrong, it reads “Depleted Uranium”, but the piece I tested was a pre-war one, containing natural, and not depleted Uranium.
So I decided to do a better, more complete test.
First of all I needed a Fiestaware containing depleted uranium, so I went after a post 1959 piece.
Checking ebay I found this saucer-cup set, dating back to the 60s according to the seller.
The initial inspection already revealed something strange, the saucer has what’s known as a wet foot, meaning the underside is completely glazed, you don't see any un-colored clay, while the cup has a dry foot ring.
I didn’t pay too much attention to it and I proceeded with the tests, starting with the saucer.
Nearly 33000 CPM on the Geiger was not a surprise, the other piece I have gave me a similar read.
Before recording a spectrum with the GS 2’’x2’’ I took a preliminary measurement of both pieces with the PDS 100G, three hours each. In order to have a good reference I also recorded a three hours spectrum of my other Fiestaware, the plate I tested back in September, containing natural Uranium.
The saucer’s spectrum left me pretty confused, it looked exactly like the plate’s, a clear indication that I was detecting natural Uranium again...did I waste my money?
The presence of natural Uranium means the saucer has been manufactured before 1943.
Here is the spectrum but in linear and logarithmic scale.
The 2’’x2’’ confirmed the saucer’s glaze had natural and not depleted uranium in it. You can tell by the prominence of the U235 peaks compared to the Th234 ones.
Protactinium 234 metastable was there as well with its two peaks at 766 keV and 1001 keV clearly visible in the “energy-per-bin” view.
Between the two Th234 peaks there’s another one at 77-80 keV, exactly where you would expect to find Lead X-Rays.
The spectrum is presented in both counts per bin and energy per bin view.
The Lead peak is not due to fluorescence from the shielding. I was expecting to find this peak and in order to be able to rule out any shield fluorescence I didn’t use any shielding for this measurement. The sample was active enough to be tested properly with a simple background subtraction.
So the Lead fluorescence peak comes from the saucer itself.
And now for the quantitative analysis, here’s the usual tab. It was several months since I measured the unshielded background of my measurements room, it didn’t change much since then, albeit a small change is there after all, it held stable at 256-259 CPS throughout many measurements across months. This time it was 251 CPS.
As for the sample: 438 CPS, but almost all of very low energy, therefore the measured exposure was the same I got from the background.
Part 2 about the cup is on the way...
According the New York Times “Fiestaware is the most collected brand of china in the United States. It's also the No. 1 selection for casual dinnerware in American bridal registries”.
[broken link removed - Steven]
The reason such an object is interesting to someone into gamma spectroscopy and radiation detection in general is that the red "Fiestas" pieces manufactured up until 1973 had Uranium Oxide in their glaze so they were pretty radioactive.
Between 1936 and 1943 Natural Uranium was used. Then, during WWII, the Manhattan Project started, the US government took control of Uranium and confiscated the company’s stocks of Uranium. The production of the red Fiestas stopped and only resumed in 1959, this time using depleted rather than natural Uranium.
In both cases the Uranium was chemically refined, so it did not contain all the products of the decay chain like Radium, Lead and Bismuth. Allegedly only the first isotope of the decay chain is present: Thorium 234, but the second makes an appearence here as well.
The difference between the pre-war and post-war pieces is the presence of Uranium 235, a lot more prominent in the pre-war pieces, containing natural Uranium.
I already posted a Fiestaware thread, but back then I had a few misconceptions about a thing or two.
viewtopic.php?f=5&t=522
To start with, the thread title was wrong, it reads “Depleted Uranium”, but the piece I tested was a pre-war one, containing natural, and not depleted Uranium.
So I decided to do a better, more complete test.
First of all I needed a Fiestaware containing depleted uranium, so I went after a post 1959 piece.
Checking ebay I found this saucer-cup set, dating back to the 60s according to the seller.
The initial inspection already revealed something strange, the saucer has what’s known as a wet foot, meaning the underside is completely glazed, you don't see any un-colored clay, while the cup has a dry foot ring.
I didn’t pay too much attention to it and I proceeded with the tests, starting with the saucer.
The saucer’s spectrum left me pretty confused, it looked exactly like the plate’s, a clear indication that I was detecting natural Uranium again...did I waste my money?
The presence of natural Uranium means the saucer has been manufactured before 1943.
Here is the spectrum but in linear and logarithmic scale.
Protactinium 234 metastable was there as well with its two peaks at 766 keV and 1001 keV clearly visible in the “energy-per-bin” view.
Between the two Th234 peaks there’s another one at 77-80 keV, exactly where you would expect to find Lead X-Rays.
The spectrum is presented in both counts per bin and energy per bin view.
And now for the quantitative analysis, here’s the usual tab. It was several months since I measured the unshielded background of my measurements room, it didn’t change much since then, albeit a small change is there after all, it held stable at 256-259 CPS throughout many measurements across months. This time it was 251 CPS.
As for the sample: 438 CPS, but almost all of very low energy, therefore the measured exposure was the same I got from the background.