ML20034B281
| ML20034B281 | |
| Person / Time | |
|---|---|
| Issue date: | 04/20/1990 |
| From: | Liza Cunningham Office of Nuclear Reactor Regulation |
| To: | Bellian J BICRON CORP. |
| References | |
| NUDOCS 9004260302 | |
| Download: ML20034B281 (6) | |
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April' 20,1990 Mr. Joseph G. Bellian i
Manager, Electronic Products Bicron Corporation 12345 Kinsman Road 3
Newbury, Ohio 44065-9677
Dear Mr. Bellian:
j Enclosed for your information is a draf t NRC information notice concerning -
l the potential for dose. rate survey instruments underresponding to the true l
radiation fields. This draft information notice is 'md on a review of the 1
00E Safety Action Notice on the RSO 5 series of instF 1ts,-Bicron's corrective actions as discussed in your letter, dated March 16,.mo to NRC, and discussions
]
between my staff and other technical experts on the subject. We encourage any i
comments concerning the technical and/or factual accuracy of information contained in the enclosed draft information notice by c.o.b. May 4, 1990, In accordance with our policy, this letter, 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) 4921147.
Sincerely, ief.C nOhm f
Le Radiation Protection Branch Division of Radiation Protection and Emergency Preparedness I
i-Office of the Nuclear Reactor Regulation l
Enclosure:
As stated DISTRIBUTION: _
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' April 20,1990-
- s+w Mr. Joseph G. Bellian Manager, Electronic Products Bicron Corporation 12345 Kinsman Road Newbury, Ohio 44065-9677
Dear Mr. Bellian:
Enclosed for your information is a draft NRC information notice concerning_
~
the potential for dose-rate survey instruments underresponding to' the~ true.
radiation fields. This draft information notice is based on a. review of the vi DOE Safety Action. Notice on.the RS0-5 series of instruments,- Bicron's corrective i
actions as discussed in your letter, dated March 16,,1990 to NRC, at:d-discussions J
between my staff.and other technical experts on the subject.- We encourage any '
i comments concerning the technical and/or factual accuracy of information contained in the enclosed draft information notice by c.o.b. May.4, 1990.
~
In accordance with our policy, this letter, along with.its enclosures, will be i
placed in the Public Document Room.
If you have any questions,.please call me
't l
at(301)492-1111 or Joseph Wang at (301) 492-1147.-
o Sincerely, 3
i
!=
l' p LeMo'ine J.
unningham, Chief.
i Radiation Protection Branch Division of Radiation. Protection and-Emergency Preparedness.
Office of the Nuclear Reactor Regulation'
Enclosure:
As stated I
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NUCLEAR' REGULATORY COMMIS$10N OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 date
.NRC INFORMATION NOTICE No. 90-XX: Dose-rate Survey Instruments Underresponding To The True Radiation Fields Addressees:
ALL NRC Licensees i
Purpose:
This information notice alerts addressees to potentia 1' problems resulting 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.conteined in this'information-notice do not constitute NRC requirements;~therefore, no specific action or written response is required.
Description of Circumstances:
- t 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'sthirdrange(0-500'mR/h). No personnel overexposure to radiation-occurred due to these instrument failures. This type _ of problem cati also occur for other instruments which have the same type of magnet arm switching.
design as the RS0-5.
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 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 hioves tho magnet over the zero reed' switch and shorts the electronics input =for zeroing. Switchingfromzerotothefirst(0-5mR/h)andsecond.
(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 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 t
for movement of the 4
1
- i
' magnet arm with respect to the cam can result in tne 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) 4 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, J
underresponse to the true radiation fields for these dose-rate survey:
instruments can occur as e result of switching between these lower two ranges.
l This is because when the high range reed switch is in.the closed nosition, a
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different electronic circuit is actuated which reduces the sensitivity on i
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)-
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 instrument for shipment.
Discussion of Safety Significance:
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 mP/h) can only result in overresponse of the instrument.
If a licensee performing a survey with the instrument is not sure that he/she is in a high radiation field, the licensee can ensure that the instrument.is not underresponding by switching first to the high range: settings to quantify the upper limit of the radiation TTeT8 before range switching to.the lower range settings.
i This type of instrument problem reinforces the benefits =of source checking the-instrument prior to use, consistent with good ALARA practices.
i Licensces should also be aware that use of these type of magnet arm switching
. instruments in areas with high magnetic fields can inadvertently actuate the reed switches in the instrument without movement of the magnet arm.
(ANSI l
N42.17A,. Performance Specifications For Health Physics Instrumentation
-Portable Instrumentation For Use In Normal Environmental Conditions.)
l In addition to the Bicron Model RS0-5, we have identified that malfunctions may also occur for the following instruments:
i
s
's a
Bicron Model RS0-50 Eber11ne Model R0-2 Eberline.Model R0-2A' The Department of. Energy Safety Action Notice has recommended that all magnet I
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 l
manufacturer at:
Bicron' Corporation 12345 Kingman Road Newbury, OH 44065 John Nedorest (216)564-8000 Eberline Instrument Corporation-504 Airport Road P.O. Box 2108 Santa Fe, NM.87504-210B Ed Bethel (505) 471-3232 '(Ext 654)
Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical
Contact:
Joseph C. Wang, NRR (301) 492-1147 Attachments:
1.
Figure 1, Typical Magnet Arm Position, RSO Instruments 2.
List o Recently Issued NRC Information Notices t
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