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
Page Last Reviewed/Updated Tuesday, March 09, 2021