South Texas Project responds as follows: The rule we use is reflected in our survey procedure. The salient text is below. 5.13 IF using an ion chamber to determine contamination levels, THEN document the results in mRad/hr (see Step 4.0 of this addendum) OR; 5.13.1 Subtract any significant gamma background e.g., 0.5 mr/hr, THEN MULTIPLY the open window reading by 100,000 AND 5.13.2 RECORD the result in dpm.
Since we use a beta correction factor of 3 for RO20s, the conversion from mrad/h to dpm would be 1 mrad/h = 33K dpm. We have a technical basis document written 10+ years ago. Essentially, the ion chamber measurement is assuming that the contaminant is Co-60. Regards, Leonard Earls Consulting Engineer 361-972-7759 ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, September 27, 2011 17:15 To: [email protected] Cc: [email protected] Subject: Powernet: Off Scale Count Rate Instrument Rules of Thumb Palo Verde requests information on the following: If a count rate instrument's reading exceeds the measurement capability (i.e., off-scale), do you use or have a thumb rule to convert dpm to mrad? I have seen some mrad to dpm conversions such as 25,000, 28,000, and 50,000 dpm per mrad; however, I have not seen any technical justification or limitations for these thumb rules. If you have such guidance in your program what value do you use? Do you have any precautions or limitations for the thumb rule usage, e.g., qualitative measurement only, specified measurement height above smears, etc. Thanks, Seth ********************************************************************** Seth J. Kanter, CHP, RRPT Sr. Health Physicist Palo Verde Nuclear Generating Station Mail Sta. 7397 5801 S. Wintersburg Rd. Tonopah, AZ 85354 Phone (623) 393-3130 Fax (623) 393-1853 Unless otherwise noted, all opinions are my own Liviu Librescu ********************************************************************** --- NOTICE --- This message is for the designated recipient only and may contain confidential, privileged or proprietary information. If you have received it in error, please notify the sender immediately and delete the original and any copy or printout. Unintended recipients are prohibited from making any other use of this e-mail. Although we have taken reasonable precautions to ensure no viruses are present in this e-mail, we accept no liability for any loss or damage arising from the use of this e-mail or attachments, or for any delay or errors or omissions in the contents which result from e-mail transmission.
