ML20034B279
| ML20034B279 | |
| Person / Time | |
|---|---|
| Issue date: | 04/19/1990 |
| From: | Liza Cunningham Office of Nuclear Reactor Regulation |
| To: | Wells J EBERLINE INSTRUMENT CORP. |
| References | |
| NUDOCS 9004260299 | |
| Download: ML20034B279 (6) | |
Text
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_ April 19,1990; Mr. Julian Wells Quality Assistance' Manager Eberline. Instrument Corporation 504 Airport Road P.O. Box 210F Santa Fe, New Mexico 87504-21-8 i
Dear Mr. Wells:
(
L Enclosed for your'information is a= draf t NRC information n'otice concerning -
the potential for dose-rate survey instruments underresponding to the true radiation fields. This draft information notice is based on a review of theJ DOE Safety Action Notice on the'R0-2 series of instruments, Bicron's corrective <
actions as discussed in their letter', dated March 16, 1990 to NRC,'and discussions We encourage any-
-between my staff and other technical experts on the subject.
comments concerning the technical _and/or factual accuracy of information-contained-in the enclosed draft informatir>n-notice by c.o.b. May 4,-1990.
In accordance with our policy this~1etter, along with its enclosures, will be placed in the Public Document Room.
If. you. have any; questions, please call me at(301)492-1111 or Joseph Wang. at (301) 492-1147.:
Sincerely,
/s/.
i LeMoine J. Cunningham,' Chief; Radiation Protection Branch Division of Radiation' Protection and Emergency Preparedness L
Office of~the Nuclear Reactor Regulation-l l
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Enclosure:
As stated DISTRIBUTION:
Decke6tM3eg F. Congel PRPB Reading File NRC PDRs J. Wang
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4 Mr.- Julian Wells Quality' Assistance' Manager 3
Eberline Instrument Corporation.
504 Airport Road-P.O. Box-210F
. Santa Fe,-New Mexico 87504-21-8 t
Dear Mr. Wells:
Enclosed for--your information. is a draft NRC information notice concerni.ig_
the~ potential for dose-rate survey instrumentscunderrespondingLto,the true.
radiation fields. This draft information notice is~ based on a: review of. ther 4
DOE Safety Action Notice. on the R0-2 series.ofdinstruments,-Bicron's corre'etive' actions as discussed in' their letter; dated March 16.1990-to'NRC,:and discussions between my staff and other. technical experts on thel subject. We encourage,any comments concerning the technical and/or factual accuracy-of, information contained in the enclosed draf t information notice by-c.o.b.- May 4, ~1990.
In accordance with our polig this. letter, along'with~its enclosures', will'be.
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placed in the Public Document Room.
If you have any. questions, please call'me-at(301)492-1111 or Joseph Wang at (301) 492-1147.
Sincerely,,][
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finingham,pthief-l Rad tion Protection Branch-t Division of Radiation Protection and Emergency Preparedness-Office of the Nuclear' Reactor Regulation
Enclosure:
As stated i
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~ WASHINGTON,.D.C. 20555 date NRC INFORMATION NOTICE No. 90-XX: Dose-rate Survey Instruments Underresponding To The'True Radiation Fields, i,
Addressees:
ALL NRC Licensees
Purpose:
This information notice alerts addressees to potential problems resulting J
from dose-rate survey instruments underresponding to.the true radiation fields.
It-is expected that recipients-will' review the information_for applicability to their facilities and consider actions, as. appropriate to-avoid similar problems. However, suggestions. contained in.this.information.
notice do not constitute NRC requirements; therefore, no specific action-or l
written response is required.
Description of Circumstances:
L The Department of Energy recently issued a Safety Action Notice that described an event where two Bicron RS0-5 dose-rate instruments underresponded by a factor of about_100 on the second (0-50 mR/h) range. <The problem occurred when two health physics personnel were providing radiation protection; coverage at a DOE contractor facility. 'A normal reading was observed on the dose'-rate..
~
instrument's third range (0-500 mR/h). No personnel overexposure.to radiation occurred due to these instrument failures. This type of problem _can also
~
occur for other instruments which 'have the.same type of magnet arm switching.
design as the RS0-5.
3 The instruments were taken out of service and returned to the manufacturer.
Bicron's examination confirmed the.effect and found the cause of the failure-to be improper positioning of the magnet'which activates reed switches in the
. ion chamber. This magnet moves on a cam actuated arm attached to the range i
switch.
Figure 1 gives typical magnet arm positions for the Bicron RSO series-of instruments. At the zero position (one.end) of the range switch rotation, the arm moves the magnet over.the zero reed switch and shorts the electronics-input for zeroing. Switching from zero to the first (0-5 mR/h) and second (0-50 mR/h)' ranges, the cam moves the end of the magnet arm to the center position between the zero and high range reed switches, and neither reed 1
switch-is closed.
If the. magnet arm is not properl the point of contact, the extra room allowed (play)y aligned with the cam at i
for movement of the-e m-e
i i
magnet' arm with respect to the cam can result in the magnet at the other end-of the' magnet arm to be placed sufficiently past the. center position to close the high range reed switch upon range switching between the first (0-5 mR/h) and the second (0-50 mR/h) lower two ranges even though the magnet arm is not~
supposedly to move..
Because of the possibility for the above mechanical problem, severe underresponse to the true radiation fields for these dose-rcte survey instruments can occur as a result of switching between-these lower two rances.
This is because when the high range reed switch is'_in-the closed position, a i
different electronic circuit is actuated which reduces the sensitivity on-these ranges by a factor of about 100, requiring a true dose-rate of 5,000-mR/h to produce a full scale deflection on the (0-50 mR/h) scale or-a true-dose-rate of 500 mR/h to produce a full scale deflection on the (0-5 mR/h)_
1 scale.
The Instrument Engineering Department of Bicron has added an additional' quality assurance test to ensure the proper alignment of the magnet arm with respect'to the reed switch. This test is to be performed during the final acceptance test of a new instrument and-again prior to calibrating the new-i instrument for shipment, Discussion of Safety Sionificance:
i All licensees need to be aware of the potential for underresponse at the lower two ranges for all magnet arm switching dose-rate instuments.
Failure (i~.e.
high range reed switch in the open position) at the high range settings (0-500 mR/h, 0-5,000 mR/h) can only result in overresponse'of the: instrument. =lf a licensee performing a survey with the instrument is not sure-that he/she is in i
a high radiation field, the-licensee can ensure that.the instrument is not first to the high range settings to quantify th_e underresponding by switching TieTd before range switching to the lower range.
upper limit-of the radiation
- settings, r
This type of instrument problem reinforces the benefits of source checking the instrument prior to use, consistent with good ALARA practices.-
Licensees should also be aware that use of these type of magnet arm switching instruments in areas with high magnetic fields can inadvertently actuate the l
reed switches in the instrument without movement of the magnet arm.
(ANSI N42.17A, Performance Specifications For Health Physics Instrumentation
-Portable Instrumentation For Use In Normal Environmental Conditions.)
In addition to the Bicron Model RS0-5, we have identified that malfunctions may also occur for the following instruments:
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.'c, Bicron Model RS0-50 s
Eberline Model.R0 Eberline Model.RO-2A The-Department of Energy Safety Action Notice has recommended that all magnet arm switching dose-rate instruments _be inspected for proper alignment of_the-magnet arm and the presence of set screws to maintain the proper positioning of the magnet arm.
For copies of revised maintenance-procedures and other technical information concerning their instruments, contact the appropriate manufacturer at:
Bicron Corpo_ ration 12345 Kingman Road Newbury, OH 44065 John Nedorest (216)564-8000
~~~
Eberline-Instrument Corporation I
504 Airport Road P.O.-Box 2108 Santa Fe, NM 87504-2108
-l Ed Bethel
-1 (505)- 471-3232 (Ext 654)
Charles E. Rossi,-Director _
Division of Operational Events Assessment Office of' Nuclear Reactor Regulation Technical
Contact:
Jose h C. Wang, NRR (301 492-1147 Attachments:
i 1.
Figure 1, Typical Magnet Arm Position, RSO Instruments
.i 2.
List o Recently Issued NRC Information Notices
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4 Typtral "B"
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Position For
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Zero Reed Switch Closure.
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Typical "C"
Position For High Range Reed Switch Closure.
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-Typical. Magnet Arm Position 3
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I 9^fjh!qn LRSO
' Instruments DEBURR A BREAK DO NOT REV.
DATE DESCRIPTION BY alt. EDGES
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