Gamma Ray Measurements |
Here are several examples of the environmental gamma ray measurements that have been carried out by the Nuclear Physics Group of the University of Liverpool:
In about 1880 Straw Opal Glass was made at the Whitefriars glassworks in London. Its yellow colour was achieved by adding Uranium oxide. Measurements were carried out in collaboration with Liverpool Museum to try to measure the Uranium content to check whether the items have a composition consistent with the known recipe for Whitefriars Straw Opal Glass.
The items measured are shown in the photograph.
The gamma ray spectrum shows both 235U and 238U. The amounts present were deduced to be:
| 238U | 0.65g |
| 235U | 0.0043g |
The accuracy was limited to about ±20% by the detector efficiency calibration.
No daughter products lighter than 226Ra are seen.
The items had an amount of Uranium consistent with that expected. The records of the recipe to which the glass was made are equally uncertain. One report is that the glass consisted of:
| Sand | 1800 cwt | ||
| Red Pb | 12 cwt | ||
| Potash | 5 cwt | 3 qtr | 14 lb |
| Petre | 1 cwt | 0 qtr | 21 lb |
| Arsenic | 7.5 lb | ||
| Borax | 7.5 lb | ||
| Manganese | 12 oz | ||
| Uranium Oxide | 270 lb |
The movement of sheep west of the River Conwy was restricted following the Chernobyl incident in 1986. The results of a survey in March 1997 are shown.
Samples were taken in a field near Capel Curig in Snowdonia. The gamma ray spectrum has several prominent peaks:
| 662 keV | 137Cs |
| 238 keV | 212Pb (from 232Th) |
| 911 keV | 228Ac (from 232Th) |
| 1460 keV | 40K |
| 352 keV | 214Bi (from 238U) |
The activity versus depth profile that was measured for the 137Cs and 134Cs showed that they peaked about 5cm below the surface.
The River Dee flows from Wales through Chester into the Irish Sea. Samples were taken from Parkgate which is on the tidal estuary. The area where the sample was taken was marshland. The gamma ray spectrum shows prominent peaks:
| 60 keV | 241Am |
| 662 keV | 137Cs |
This sample was taken from the surface, the deduced activity being:
| 241Am | 150 ± 15 Bq/kg |
| 137Cs | 540 ± 20 Bq/kg |
For more information contact Prof. Paul Nolan, pjn@ns.ph.liv.ac.uk