API Bull E2:2006 pdf download
API Bull E2:2006 pdf download.Bulletin on Management of Naturally Occurring Radioactive Materials (NORM) in Oil and Gas Production.
This section provides information describing radiation measurement and sampling techniques and appropriate applications in NORM surveys. This section also gives information on instrument maintenance and calibration and associated records.
3.1 SURVEY MEASUREMENT AND SAMPLING TECHNIQUES
NORM survcys generally involve thc following measurement and sampling techniqucs:
• Gamma surface scans
• Exposure rate measurements
• Direct measurements for total and removable alpha or beta surface activity
• Radionuclide concentrations in media (e.g.. soil, sediment, sludge, water, air)
• Personnel monitoring for external radiation exposure
• Personnel monitoring for internal radiation exposure
The following sections discuss each measurement or sampling technique and describe the application of the technique to monitoring for oilfield NORM.
3.1.1 Gamma surface scans
Instrumentation used to perform gamma surface scans typically includes a ratemeter/scaler coupled to a I or 2 inch sodium iodide scintillation detector. Surfaces are scanned to identify areas of elevated direct radiation which, based on the results of the scan. may require further investigation. The surveyor passes the detector slowly over the surface while keeping it as close to the surface as conditions allow. Increases in the count rate, as indicated by the audible output of the instnhmnent, are monitored, and areas of elevated direct radiation are identified for further investigation.
The area or item under investigation should he systematically surveyed. The surveyor should pay particular attention to areas such as pipe elbows where solids may accumulate. The meter probe should be in close proximity with the external surface of the equipment (normally not more than 1 centimeter away) and moved slowly across the equipment surfaces. The survey instrument’s response switch should be set to the fast” position during the initial scanning of the equipment. This setting minimizes the possibility of not detecting NORM dcposits. Wherever NORM deposits have been identified, the response switch should be set to the “slow” position in order to obtain more accurate readings.
Production equipment. particularly water-handling equipment. should be surveyed for external gamma radiation. In addition. equipment being removed from service, released for maintenance work, or released for unrestricted use (e.g.. sold or scrapped) should he surveyed for NORM.
Gamma surface scans of soil areas should be conducted over the subject land area on a dclincatcd grid. The grid spacing should be optimized for the size of the area to be surveyed, as well as for the potential for identifying areas with elevated readings: the smaller the area to be surveyed. the smaller the grid spacing. Some regulatory agencies require that grid spacing not exceed 10 meters (30 feet). One technique that has been particularly useful for large areas is the usc of a gamma-sensitive detector used in conjunction with a global positioning system. Use of’ this type of system allows simultaneous recording of detector response and positioning information. Areas exhibiting elevated readings should be identified for follow-up investigations, which may include additional radiation measurements (cg. exposure rate measurements) and soil sampling.
3.1.2 Exposure Rate Measurements
Exposure rate measurements are performed using a gamma-sensitive survey instrument. Instruments may be a single unit that contains a read-out device and detector (for example. a micro-R meter) or two units such as a rate meter’scaler attached to a sodium iodide detector. To pcrfonn the measurement, the surveyor places the detector in a location where the measurement is desired and allows the meter to stabilize. The average value observed is recorded,
Many states have established exposure rate guideline values for equipment and areas. These guidelines specify the measurement location. Exposure rate measurements are usually performed at contact or at 1 meter.
Exposure rate measurements are usually performed on NORM-impacted soil areas, tubulars or equipment. and areas identified by gamma surface scans. The following measurement locations are recommended.
