PRM-470 Efficiency Test

The source assay activity is indicated on the certification documents or commonly printed on the source label. Verify activity is in units of Becquerels (Bq).

If needed, convert from microCi to Bq:

1 Bq = 1 microCi x 37000

Example: 7.513 microCi x 37000 = 277981 Bq

Calculate the number of days, t, between the source assay date and the current date. The assay date is indicated on the radioactive certification documents or commonly printed on the source label.

There are several online aids available to determine the number of days between two (2) dates. Example: From 15 August 2016 to 14 December 2020, t = 1582 days

A1 = Current Activity

A0 = Assay Activity

t = time since assay date in days (age)

For Co-57:

For Am-241:

Example: Co-57, Assay Activity = 277981 Bq, Age = 1582 days

Use the Rapiscan PRM-470 CG(N) Efficiency Test Form at the end of this procedure to document the PRM-470 model and serial number, Radioactive Isotope, Assay Date, Assay Activity, Age, and Current Activity.

Set the instrument on a stable surface.

Moving the instrument will cause it to enter SEARCH or FIND Mode. If this happens, press the MODE button to enter BACKGROUND MODE and wait for 30 seconds.

Write down the background counts on the Rapiscan PRM-470 CG(N) Efficiency Test Form.

Use tape to secure the radioactive source to the center of the bottom of the detector.

Moving the instrument will cause it to enter SEARCH or FIND Mode. If this happens, press the MODE button to enter BACKGROUND MODE and wait for 30 seconds.

N = Average CPS from source

N = Average CPS (source + background) – Average CPS (background)

Example: N = 278 – 60 = 218 CPS

E = Efficiency

A1 = Current Activity

N = Average CPS from source

For Co-57:

For Am-241:

Example: Co-57, N = 218, A1 = 4866 Bq

Record the calculated efficiency on the Rapiscan PRM-470 CG(N) Efficiency Test Form.

Submit assessment form or HATS assessment form electronically to proper authorities.