IE Circular 81-06, Potential Deficiency Affecting Certain Foxboro 10 to 50 Milliampere Transmitters
SSINS No.: 6820
Accession No.
8011040288
IEC 81-06
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 14, 1981
IE Circular 81-06: POTENTIAL DEFICIENCY AFFECTING CERTAIN FOXBORO 10 to 50
MILLIAMPERE TRANSMITTERS
Description of Circumstances:
NRC has been recently advised of two deficiencies in certain E-10 Series
Foxboro transmitters which could adversely affect their operation during
accident conditions. The deficiencies involve the improper use of Teflon
wire insulation and an unsuitable capacitor in the amplifier section of
these transmitters. The transmitters in question have been identified as
Foxboro Models N-E11, N-E13, and E-11, E-13 with suffix Codes /MCA,
/MCA/RRW, and /MCA/RR. These transmitters operate at an output signal level
of 10 to 50 milliamperes (mA). Similar model number units operating in the
range of 4 to 20 mA are not a concern in these matters.
Briefly, the information on the deficiencies was brought to the attention of
the NRC Staff during a recent meeting with several licensees of a "Utility
Transmitter Qualification (UTQ) Group." This group has been formed to
develop and implement an acceptable environmental qualification test program
for safety related electrical equipment in use or planned for use in nuclear
power plants.
According to Foxboro, the Teflon insulation material in question has
demonstrated a tendency to embrittle and deteriorate when subjected to an
integrated radiation dose of 200 megarads. A total integrated dose (TID) of
200 megarads was called for in the qualification test sponsored by the UTQ
Group that led to the discovery of the Teflon insulation and capacitor
problems.
With respect to the capacitor problem, the manufacturer determined that the
capacitor was not hermetically sealed as specified. Unsealed capacitors can
leak and malfunction under adverse conditions, especially those of heat and
time. Foxboro determined that the capacitor failed after being subjected to
high temperatures resulting from gamma heating during the above-mentioned
qualification test.
Subsequent to the investigation into the discussed problems, Foxboro issued
a technical letter dated March 12, 1981 to all licensees, NSSS vendors,
architect-engineers, and others who have purchased the Foxboro 10 to 50 mA
transmitters in question. This technical letter further describes the Teflon
and capacitor deficiencies and provides recommendations to identify and
correct the problems. Foxboro has also provided a copy of master instruction
(MI) booklet, MI-20-145, dated September 1976, on the Foxboro 10 to 50 mA
transmitters, to recipients of the technical letter. The MI document has
been specifically marked on pages 5 and 6 to identify the parts of the
amplifier in question.
.
IEC 81-06
April 14, 1981
Page 2 of 2
Enclosed are copies of the technical letter and the master instruction
document for your use and appropriate action.
For holders of Licenses of operating facilities including NTOL and SEP
plants, it should be noted that reporting requirements are specified in the
NRR/OL safety evaluation report (SER) relating to environmental
qualification of safety related electrical equipment. These instructions,
"We request that you provide --- within 90 days," are stated in both the SER
and the transmittal letter to each utility.
Recommended Actions to be Taken by All Nuclear Power Facilities Holding an
Operating Licensee or a Construction Permit:
1. Determine if your facility has installed or plans to install Foxboro 10
to 50 mA transmitters that have model numbers the same as those
identified above in safety-related systems located in areas subject to
a harsh environment, including those areas where long-term LOCA coolant
piping is routed.
2. Where Foxboro 10 to 50 mA transmitters are identified, it is
recommended that you replace the suspect amplifiers in accordance with
the recommendations and instructions provided in the enclosed letter
and instruction manual. However, if it is determined that a transmitter
is installed in an area where the TID is less than 10 megarads, the
licensee should assure that the affected transmitter will function as
intended under the expected TID resulting from the postulated accident
conditions.
3. We remind you that the equipment qualification SER identified above
requires that licensees of operating facilities (including NTOL and SEP
plants) develop plans and programs including schedules for corrective
action and the basis supporting continued operation regarding items 1
and 2 above. This information should be incorporated in your submittal
to the SER on equipment qualification.
4. For Holders of Construction Permits, resolution of these matters should
be available for review through normal follow-up inspections by the NRC
Regional Offices. This information will also be considered during the
operating license review.
No written response to this circular is required. If you need additional
information with regard to this subject, please contact the Director of the
appropriate NRC Regional Office.
Attachments:
1. Foxboro Technical Letter
dated March 12, 1981
2. Foxboro Master Instruction
MI 20-145 dated September 1976
3. Recently issued IE Circulars
.
Attachment 1
Foxboro, MA 02035 U.S.A.
(617)543-8750
The Foxboro Company
12 March 1981
Subject: Potential Deficiency Affecting Foxboro Transmitters, Model Numbers
N-E11, N-E13 or E11, E13 with suffix Codes /MCA, /MCA/RRW, or
/MCA/RR
Gentlemen:
Our records indicate that you have received one or more of the Foxboro model
numbered transmitters listed above. This letter is to notify you that two
deficiencies have been discovered in some of these transmitters which may
exist in the units shipped to you. The transmitters in question operate at a
signal level of 10-5OmA. Similar model numbered units operating at 4-2OmA
are not affected.
The first issue involves the possible use of incorrect insulating sleeving
on transistor and zener diode lead wires in the amplifier. The second issue
involves the use of a specific vendor's capacitor which is not hermetically
sealed (although claimed to be so). As a result, the capacitor electrolyte
can leak under adverse service conditions, specifically heat and time. The
failure mode is a decrease in resistance across the capacitor resulting in
electrical leakage. The transmitter operation can be affected by limiting
the output to something less than full value which, in time, can degrade to
no output at all.
Insulating Sleeving - Radiation resistant sleeving consisting of a silicone
coated glass fiber braid has been substituted by a teflon sleeving in some
transmitters. Tests have shown that teflon will become brittle and
deteriorate with a substantial integrated radiation dose. Foxboro testing
has demonstrated that the teflon sleeving used in these devices will
withstand an integrated dose of 10 megarads with no noticeable
deterioration. Tests to 200 megarads produce the brittle conditions which
can result in the teflon flaking from the wires. Based on these tests,
operating plants not expected to exceed an integrated dose of 10 megarads
have no potential problem and no action is required.
Where the integrated dose rate could exceed 10 megarads, then units in
service should be inspected to determine if the proper insulating material
has been used. This can be accomplished by opening the transmitter in
accordance with Foxboro Master Instruction MI 20-145. The amplifier cover
must be removed exposing the amplifier assembly. At one end of the assembly,
a transistor and a zener diode are mounted in the base casting which serves
as a heat link. The insulating material in question is a sleeving slipped
over the lead wires from these two components. The proper material is white
and heavy looking. Positive
.
Page 2
12 March 1981
Subject:
identification can be made by inspecting one end of the material to
establish that the outer material covers an inner braid. Teflon, if used,
will be a single layer material and could be either clear or white.
If improper insulation is present, then the corrective action is to replace
the amplifier (Foxboro P/N N0148PW). Replacement amplifiers can be purchased
from your local Foxboro Sales or Service Representatives. If you prefer to
have Foxboro Service Personnel inspect the equipment and, if necessary,
replace the amplifier, this can be arranged at standard service rates.
Capacitor - The capacitor degradation problem was discovered over time
through tracking failure situations. Internal corrective action has been
taken to remove the vendor involved from the qualified vendor list and to
purge all stock of capacitors from this vendor. Degradation of this
capacitor is a function of time and service conditions with heat being a
primary contributor. This phenomenon was observed in recent tests of
transmitters using these capacitors. The capacitor in question is
manufactured by Cornell-Duebilier and can be specifically identified by a
type number in the form TX-65-XXXX as well as a monogram in a box followed
by a date code, e.g. CDE 0874. It is assigned Foxboro part number N0141MF.
To determine if this capacitor is present requires a visual inspection of
the amplifier which can be accomplished as described above for the
insulating sleeving inspection. The recommended corrective action should the
above described capacitor be present is to replace the amplifier (Foxboro
P/N N0148PW) although is possible to replace the capacitor with a Foxboro
provided substitute. Use of Foxboro Service personnel to perform the
inspection and replacement, if necessary, can be arranged at standard
service rates as described above.
Due to lack of knowledge of specific application, redundancy, and the like,
Foxboro cannot determine if the NRC reporting requirements of 10CFR Part 21
are applicable. This determination is the responsibility of the user and any
such reporting would be made by them after completing their evaluation of
the situation.
If you have any questions regarding the above, please contact the
undersigned directly.
Very truly yours,
THE FOXBORO COMPANY
William Calder, Manager
Corporate Quality Assurance
joy
120381
Enclosure MI 20-145
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