Information Notice No. 82-32: Contamination of Reactor Coolant System by Organic Cleaning Solvents
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D. C. 20555
August 19, 1982
Information Notice No. 82-32: CONTAMINATION OF REACTOR COOLANT SYSTEM
BY ORGANIC CLEANING SOLVENTS
All nuclear power reactor facilities holding an operating license (OL) or
construction permit (CP).
This information notice is provided as a notification of an event that may
have safety significance. It is expected that recipients will review the
information for applicability to their facilities. No specific action or
response is required at this time.
Description of Circumstances:
on April 24, 1982, while at full power, the Hatch Unit 1 plant experienced a
rapid increase in water conductivity in the condensate, feedwater, and
primary reactor systems. This was accompanied by increasing radiation
readings on the main steam line and offgas monitors. Operations personnel
began an orderly power reduction at 1430 CST. By 1730 CST, with the reactor
power at 35%, the reactor water conductivity had exceeded the Technical
Specification limit of 10 micromhos per centimeter. The plant was manually
scrammed at 1930 CST. At 19 hours into the event the conductivity peaked at
21 micromhos per centimeter. At this time the chloride level in the reactor
water, which also had been increasing, peaked at 2.5 ppm and the pH had
dropped to 5.1. The Hatch Technical Specification limits for these values
are 0.5 ppm for chlorides and greater than 5.2 for pH. A local power range
monitor (LPRM) detector failed within 9 hours of the start of the event and
by 48 hours into the event, 35 LPRM detectors had failed. This event
resulted in a plant outage of more than than 1 month.
After an extensive investigation, the licensee identified the cause of the
problem as contamination of the reactor coolant by trichloroethane. This is
an organic solvent (purchased under the trade name of "MOMAR Electrosafe"),
used for cleaning and decontamination at Hatch. MOMAR is a nonconducting,
nonionic cleaning agent for electrical equipment. The trichloroethane is
believed to have been present in the turbine building equipment drain sump
before the event. A leaking valve resulted in the overflow of water from a
condensate demineralizer system which also flowed into the same drain sump.
The sump pump automatically started and transferred the sump water along
with the trichloroethane into the radwaste collector tank. This water was
processed by the waste cleanup system and after routine sampling was
transferred into the condensate storage tank and then back to the reactor.
August 19, 1982
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The trichloroethane, being nonionizing, was not removed by the resins in the
radwaste demineralizers. Furthermore, the normal demineralized water
sampling methods, which largely depend on measuring the conductivity of the
water, did not detect the nonconducting trichloroethane. The licensee was
able to show, however, that the solvent breaks down and becomes ionizing
(and conducting) in the presence of heat and radiation. A mixture of 1
milliliter of solvent per liter of water, having an initial conductivity of
1.75 micromhos per centimeter, increased in conductivity to 1580 micromhos
per centimeter when heated to 200F and irradiated in the fuel pool for
30 minutes. The chloride ion concentration in the mixture also rose from
0.025 ppm to 22.5 ppm.
In addition to investigating the cause of the contamination and to cleaning
the reactor water, the licensee took the following action in response to the
Four fuel assemblies were removed, examined, and returned to the
One control rod blade was removed, examined, and retained for future
All LPRM strings were removed and some were sent to GE for
determination of the failure mode.
Plans were made for the establishment of procedures to analyze for
organic carbons in plant water systems.
An evaluation of the effect of the event on the reactor coolant system
was included in the long-range inservice inspection program.
These actions required about 40 days to accomplish. Although no problems
were identified during preliminary visual examination of the fuel and
control rod blade, the examination of the control rod blade and the LPRMS is
continuing. Further, the licensee is establishing procedures to analyze for
organic carbons in plant water systems. Prompt detection of organics such as
trichloroethane would have prevented the incident and avoided the lengthy
No written response to this information is required. If you need more
information about this matter, please contact the Regional Administrator of
the appropriate NRC Regional Office or this office. This event is also the
subject of INPO Significant Event Report 30-82, titled "Intrusion of
Cleaning Solvents (Organic) Into Reactor Coolant System.
Edward L. Jordan, Director
Division of Engineering and
Office of Inspection and Enforcement
Technical Contact: D. C. Kirkpatrick
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