8.1 EXTERNAL DOSIMETRY

Dosimeters are radiation detection devices used to record the amount of radiation received by the wearer. The two types of dosimeters routinely used at TJNAF are the thermoluminescent dosimeter (TLD) and the Self Reading Pocket Dosimeter (SRPD).

8.1.1 TLD Badge

• The TLD is normally used to obtain your official dose of record. TLDs are processed routinely at the end of each calendar quarter. Your TLD may be retrieved for special processing more frequently if necessary. TLDs are sensitive to beta, gamma, and neutron radiation.

8.1.2 Self Reading Pocket Dosimeters - SRPDs

The term Self Reading Pocket Dosimeter applies to any of a variety of devices which can be read by the wearer to determine the dose received. The SRPD is usually used as a supplemental device to aid in dose tracking during activities where elevated doses are possible.

• Pocket Ion Chambers - (PIC) These are small instruments which operate on the electroscope principle. Typically, the range of the PIC is 0-200 mR. This is one of the most common supplemental dosimeters used in Radiation Areas.
  
  
• Electronic dosimeters (ED) are sometimes used instead of and in addition to PICs when it is helpful to have he additional capability of dose or dose rate alarm functions. The electronic dosimeter has a broad dose range and is usually very accurate.
  
  
• Self-reading neutron dosimetry such as neutron bubble dosimeters may be required for certain work areas. Always consult the applicable Radiation Work Permit (RWP) and Operational Safety Procedure.
  
  
• Other supplemental dosimeters may be required when entering High Radiation Areas or other RWP areas.

8.2 PROPER USE OF DOSIMETRY

Wear dosimetry at all times in Radiologically Controlled Areas and when required by signs, work permits or Radiological Control personnel.

Dosimetry must be worn on the chest area between the waist and the neck or as defined in radiological procedures, RWPs, or as directed by Radiological Control personnel.

When supplemental dosimeters are required, wear them in close proximity (within 3 inches) to the primary dosimeter. Have your pocket dosimeter re-zeroed by Radiological Control personnel prior to exceeding 3/4 scale or before reaching the limit prescribed by the RWP or other administrative procedure.

In the case of an offscale or irregular reading supplemental dosimeter, or an alarm in the case of an electronic dosimeter, take proper actions. These actions include:

Secure work activities



Alert others working in the area



Immediately exit the area



Notify Radiological Control personnel