Information Notice No. 85-08: Industry Experience on Certain Materials Used in Safety-related Equipment
SSINS No. 6835
IN 85-08
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D. C. 20555
January 30, 1985
Information Notice No. 85-08: INDUSTRY EXPERIENCE ON CERTAIN MATERIALS
USED IN SAFETY-RELATED EQUIPMENT
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or
construction permit (CP).
Purpose:
This information notice is being issued to provide licensees and
construction permit holders with information pertaining to the behavior of
certain materials used in safety-related equipment. The materials, as
described below, were observed to have the potential of degrading the
operability of safety-related equipment. These observations were made during
environmental qualification testing and/or during routine inspection of
in-service equipment. It is expected that recipients will review the
information for specific and generic applicability to their facilities.
However, suggestions contained in this notice do not constitute NRC
requirements; therefore, no specific action or response is required.
Description of Circumstances:
1. Elastomeric Seals Used in Personnel Air Locks for the Reactor
Containment Systems
In a recent 10 CFR 21 report to the NRC, the W. J. Woolley Company
reported that they have a testing program to qualify one type of
airlock that utilizes inflatable elastomeric seals around the perimeter
of the door for sealing against differential pressure. During this
testing, one of the inflatable seals manufactured by Presray
Corporation ruptured. The seal material is an EPDM elastomeric with a
fabric reinforcement part way around the seal, and the rupture occurred
in the area where the fabric ended. The ruptured seal was subjected to
the following conditions during the qualification test: artificial
aging for an equivalent of 5 years by exposure to 201F for 200
hours, exposure to an integrated radiation dose of 1 x 10-7 rads, and
exposure to a test chamber post-LOCA environment of 465F. These
parameters are applicable to Midland Nuclear Station.
The ruptured seal was examined by Woolley Company and Presray
Corporation. It was determined that the high temperature (465F)
had weakened the EPDM and caused the material to stretch resulting in a
rupture. The W. J. Wooley Company further stated that the Presray
inflatable seals may be
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inadequate for the following plants because of their relatively high
temperature applications:
Grand Gulf (Drywell Lock only) 330F
Perry (Drywell Lock only) 330F
River Bend (Drywell Lock only) 330F
South Texas (Containment Locks) 280F
The Woolley Company is working with Presray Corporation on the design
of a new inflatable seal that will have fabric reinforcement around the
entire seal. The new design will be used to replace the current
installed seals, according to the Woolley Company report.
2. Epoxy Phenolic Coating Applied to the Lower Portion of the Interior
Surface of Diesel Oil Storage Tank
In a 10 CFR 50.55(e) report to the NRC, the Philadelphia Electric
Company reported that during final inspection of the diesel oil storage
tanks at Limerick Generating Station, the epoxy phenolic coating on
portions of the interior surface of three of the four Unit 1 tanks was
observed to have extensive peeling and flaking. If not repaired, these
fragments could have entered the fuel oil transfer piping and filters,
thus impeding fuel oil flow and potentially causing a diesel generator
failure.
The specification for Limerick Station required that the entire
interior surface of the tanks be coated with an inorganic zinc primer
to a thickness of between 2.0 mils and 4.0 mils. On top of the zinc
primer, an epoxy phenolic coating was applied to a minimum of 12 mils
and a maximum of 18 mils dry film thickness.
Philadelphia Electric Company stated that there are two factors that
may have contributed to the coating failure: (1) chemical
incompatibility between the zinc primer and the epoxy coating, and (2)
improper curing of the zinc primer.
Subsequent investigation by Philadelphia Electric Company has revealed
an additional concern regarding the coating system. The zinc in the
primer coat may react adversely with diesel fuel when exposed over a
long period of time. Products of this reaction are often soluble when
the fuel is at room temperature, but may degrade into insoluble gums as
the fuel passes through the hot injectors and intake manifolds of a
diesel engine, and thus may result in degraded performance as the
engine is operated over a period of time.
The Philadelphia Electric Company has proposed corrective actions to
provide sufficient protection against the deficiencies described above
and also against any internal corrosion of the tanks as a result of
internal condensation. The interior surface of the tanks will be
sandblasted to white metal and recoated with a substitute epoxy
phenolic coating applied directly to the white metal. The new coating
will be certified by the vendor for compatibility with diesel fuel.
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January 30, 1985
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3. The Use of Viton Elastomer as the Seal Material in Hydrogen Recombiner
Applications
In a 10 CFR 21 report, Rockwell International reported that during the
evaluation of the post-LOCA hydrogen recombiner to develop methodology
for mechanical qualification of pressure retaining components, a
concern was raised as to the appropriateness of the use of Viton
elastomer as the seal material in recombiner application. Initial
findings indicate that Viton material would compress as a result of
exposure to radiation, elevated temperature, and steam. This
compression may cause some loss of sealing capability when the
temperature is subsequently reduced. Literature searches and inquiries
to vendors and research organizations reveals that, in laboratory
tests, Viton will exhibit deterioration in seal effectiveness when
exposed to environmental parameters similar to those conditions for
which the RI recombiners are designed. The effects on Viton elastomer
are believed to be synergistic, but the extent of synergism is not
quantifiable; e.g., steam absorption softens the material while
radiation and temperature harden it.
Rockwell International has recommended that its customers replace Viton
seals with alternate seals.
4. Environmental Qualification of ASCO NP Valves With Viton and Ethylene
Propylene Parts
The Equipment Qualification Branch of the Office of Nuclear Reactor
Regulation has reached the conclusions listed below regarding the
qualification of ASCO NP Solenoid Valves. This information superceeds
and/or supplements information previously provided in IE Information
Notices 80-11, 81-29 (Equipment Environmental Qualification Notice No.
10--Test Summary Report No. 1) and 82-52 (Equipment Environmental
Qualification Notice 10--Test Summary Report No. 2).
a. ASCO NP series solenoid valves with resilient seats and Viton
elastomers may be considered qualified only for those applications
in which the valves are not required to shift position following
exposure to total gamma radiation doses greater than 20 megarads
up to 200 megarads. No qualification data are available for
applications in which the radiation dose exceeds 200 megarads
gamma.
b. Except for model NP 8316 with Ethylene Propylene elastomers
(Suffix "E"), ASCO NP series solenoid valves are considered
qualified to the extent and levels reported in Table 5.1, pages 59
and 60 of ASCO Test Report No. AOR-78368/Rev. 1, "Report on
Qualification of Automatic Switch Co. (ASCO) Category NP-1
Solenoid Valves for Safety-Related Applications in Nuclear Power
Generating Stations," dated March 2, 1982.
c. ASCO valve model NP 8316 with Ethylene Propylene elastomers is
considered qualified to the levels reported in Isomedix Test
Report No. AOS 21678/TR, Rev. A, dated March 1978, revised July
1979. (Category III as defined in Table 5.1 of ASCO Test Report
AOR-67368/Rev. 1.)
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Discussion:
The above described circumstances, along with those circumstances that were
described and disseminated previously in Information Notices 84-12, 84-31,
and 84-83 point out the need for ongoing surveillance and evaluation of
in-service equipment to detect material degradation that may occur as a
result of the synergistic effects between material in use and the normal
operating requirements and associated environmental parameters.
The operability of the equipment will be less reliable as its constituent
materials age. The actual degradation of equipment is not quantifiable
because the synergistic effect of material is dependent on (1) the
environmental parameters where the equipment is installed and (2) the cyclic
and functional design requirements of the equipment. Very often, records of
these environmental parameters (under normal and abnormal conditions) and
records of equipment cycling or operation are not readily available and have
not been accounted for during the environmental qualification review
process. Therefore, a routine surveillance program for equipment that is
known to contain degradable material might be considered. Some licensees
have indicated that they are considering such a program, including periodic
review of the resulting data.
The items described in the above description of circumstances identify
certain deficiencies in specific equipment types. However, the NRC staff
considers that the potential effect of each of the above deficiencies is
generic in nature and is applicable to other equipment where circumstances
are similar.
No specific action or written response is required by this notice. If you
have any questions concerning this notice, please contact the Regional
Administrator of the appropriate NRC regional office or this office.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: U. Potapovs, IE
(301) 492-8030
Attachment: List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021