Environmental Gamma Ray Measurements

Environmental
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:

Victorian Straw Opal Glass

   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.

Examples of Victorian Straw Opal Glass

The gamma ray spectrum shows both 235U and 238U. The amounts present were deduced to be:

238U 0.65g
235U 0.0043g

Spectrum of gamma rays from glass sample

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

Caesium-137 activity in Snowdonia

   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)

Spectrum of gamma rays from Capel Curig

The activity versus depth profile that was measured for the 137Cs and 134Cs showed that they peaked about 5cm below the surface.

Gamma Activity in the River Dee

   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

Spectrum of gamma rays from Parkgate

This sample was taken from the surface, the deduced activity being:

241Am 150 ± 15 Bq/kg
137Cs 540 ± 20 Bq/kg

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Document Last Modified 07/25/2005 09:46:51

For more information contact Prof. Paul Nolan, pjn@ns.ph.liv.ac.uk