United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-22: Underresponse of Radiation Survey Instrument to High Radiation Fields

                                                           SSINS No: 6835 
                                                           IN 86-22       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, DC 20555

                               March 31, 1986

Information Notice No. NO 86-22:   UNDERRESPONSE OF RADIATION SURVEY 
                                   INSTRUMENT TO HIGH RADIATION FIELDS 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP), and research and test reactors 

Purpose: 

This information notice is provided to alert licensees of a warning from 
Eberline to its customers that a microcomputer-based radiation survey 
instrument, Eberline's Model ESP-1 (with a HP-290 gamma probe) may 
underrespond to high radiation fields in certain circumstances It is expect 
that recipients will review the information for applicability to their 
radiation monitoring and survey program and consider actions, if 
appropriate, to preclude similar problems at their facility However, 
suggestions contained in this notice do not constitute NRC requirements; 
therefore, no specific action or written response is required 

Description of Circumstances: 

Eberline's microcomputer-based radiation survey instrument, Model ESP-1, has
software designed to compensate for detector coincidence counting loss 
resulting from dead-time to effectively extend the useful range of detection 
system When this dead-time correction capability is exceeded (either by 
preset detector count rate or dead-time correction factor magnitude), an 
overrange warning feature alerts the user The ESP-1 instrument is designed 
to be used with a wide range of different types of detectors (eg, beta, 
alpha, neutron, gamma) 

During calibration with an HP-290 high-range gamma detector probe, Eberline 
has recently discovered that the ESP-1 software designed to correct for 
dead-time losses and provide for overrange warning does not consistently 
provide adequate overrange warning in high radiation areas Because some of 
the gamma detectors may not reach the count-rate setpoint criterion for 
overrange initiation, Eberline issued a customer warning letter October 23, 
1985 (Attachment 1) The warning letter provides sound recommendations and 
precautions for users for problem identification and prevention The staff 
has learned that Eberline has subsequently developed a software modification 
that reportedly corrects this overrange problem 



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                                                            IN 86-22      
                                                            March 31, 1986 
                                                            Page 2 of 2   

Because of the nature and potential severity of the problem, this 
information notice is being issued to reinforce the Eberline's customer 
warning and ensure all potential NRC licensees are made aware of the 
problem 

No specific action or written response is required by this information 
notice If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office 



                                   Edward L Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  James E Wigginton, IE
                    (301) 492-4967

                    Roger L Pedersen, IE
                    (301) 492-9425

Attachments:
1   Eberline Customer Letter (October 23, 1985)
2   List of Recently Issued IE Information Notices


                                                            Attachment 1  
                                                            IN 86-22      
                                                            March 31, 1986 

Eberline
Post Office Box 2108
Santa Fe, New Mexico 87501
(505)471-3232 TWX 910-985-0678

October 23, 1985 

Reference: HP-290 Probes 

Dear Customer: 

Eberline's new microcomputer-based radiation survey instrument, Model ESP-1, 
is designed to correct for coincidence loss and thus extend the range of 
each detector probe It provides an "OVERRANGE" display when the coincidence 
correction factor exceeds 5 or when the count rate exceeds 25 X 106 cpm 
With Eberline's HP-290 probe, this indication should occur at about 80 R/h, 
and it is triggered when the count rate from the GM tube exceeds 25 X 106 
cpm 

We have discovered that some of the GM tubes which can be used in the HP-290
probe may not reach 25 X 106 cpm In such cases, the detector probe can be 
in a radiation field considerably above 80 R/h and still provide a reading 
below 80 R/h Replacement tubes that have not been selected in accordance 
with Eberline's overrange criterium may create this problem even if the 
original GM tube functioned properly 

We recommend that you take one or more of the following precautions if you 
are using a HP-290 probe with an ESP-1: 

     1)   Verify that the "OVERRANGE" display occurs at an exposure rate 
          below 100 R/h; or 

     2)   Administratively limit your use of HP-290 probes to exposure rates
          below 50 R/h In this case, you ray want to set the alarm at 50 
          R/h 

                                      and

     3)   Notify all appropriate individuals in your organization about this
          precaution or limitation on the use of HP-290 probes 

Sincerely, 

Julian Wells Quality Assurance Manager 

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