Assaying of waste

A method of investigating a volume of material for radioactive material potentially associated therewith, the method comprising:

• providing an investigation location;
• providing a first detector, the interaction of one or more types of emission from radioactive material with the first detector causing the first detector to generate a signal;
• providing a volume of material at the investigation location;
• detecting signals from the first detector caused by the interaction of one or more types of emission from the radioactive material with the first detector;
• providing a second detector, the interaction of cosmic rays and/or one or more types of particle generated by cosmic rays with the second detector causing the second detector to generate a signal;
• detecting signals from the second detector caused by the interaction of cosmic rays and/or one or more types of particle generated by cosmic rays with the second detector;
• processing the signals from the first detector to provide information on the amount of radioactive material associated with the volume of material;
• processing the signals from the second detector to provide information on the amount of cosmic rays and/or one or more types of particle generated by cosmic rays incident on the investigation location;
• and
• correcting the information on the amount of radioactive material associated with the volume of material using the amount of cosmic rays and/or one or more types of particle generated by cosmic rays incident on the investigation location, thereby providing corrected information on the amount of radioactive material associated with the volume of material.