PCM-2 turning off detectors by itself yet showing "green" light (operational)

[Pmink@bnfl-ettp.com]

Greetings!



We had an interesting problem happen recently and I thought I would check 

with the Radsafe community to see if anyone's had a similar problem.  A 

PCM-2 apparently disabled all 34 alpha and 34 beta channels by itself, yet 

it still appeared to the workers that it was operational, i.e., had the 

green light.  It would go through the motions of performing a personnel 

survey and indicate that the person had nothing over the limits on them, 

but all detectors were inactive.  The Instrumentation RCT found the PCM in 

this disabled state when he went to perform a source check on it.  He then 

went to pull the PCM log data at my request so we could determine the 

approximate time frame this happened.  After pulling the data file 

(involves exiting the PCM program to DOS), the RCT restarted the PCM 

program and the unit went back to the state it was in prior to all 

channels being turned off.  We've investigated this and have ruled out 

operator error and sabotage.  The high-level password required to access 

the menus to turn off the detectors had just been changed and only three 

Instrumentation RCTs had it. 



BNFL had Thermo Eberline modify the PCM program last year so that a tech 

couldn't accidentally turn off all the detector channels with a single 

keystroke.  This accidentally happened last year when one of the field 

RCTs, trying to help out, accidentally did this.  The menu options to turn 

off a single detector channel and to turn off ALL detector channels are 

right next to each other in the menu and the screens for each of them look 

exactly alike, except one says "all detector channels."  The modification 

Thermo made for BNFL requires that each detector channel has to be 

individually turned off, so someone would have to send a lot of time to 

turn off a total of 68 channels.  The last incident was issued as a 

"Lessons Learned" through the DOE system, which warned that the PCMs will 

still show a green light (i.e., appears to be operational) even if all 

detectors are off.



Anyone seen anything similar to this?



Thanks -



Paul J. Mink, SAIC

Lead Radiological Engineer/Technical Support

BNFL-ETTP RADCON K-1550-T trailer

Office (865) 576-2123

Fax     (865) 241-0452

Alpha pager 1-800-622-6576  (http://www.arch.com/message/)

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