Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
June 19, 1991
Information Notice No. 91-40: CONTAMINATION OF NONRADIOACTIVE SYSTEM
AND RESULTING POSSIBILITY FOR
UNMONITORED, UNCONTROLLED RELEASE TO THE
ENVIRONMENT
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is intended to alert addressees to the continuing
possibility for unmonitored, uncontrolled releases of radioactive material.
The staff had previously addressed these concerns in NRC IE Bulletin 80-10,
"Contamination of Nonradioactive System and Resulting Potential for
Unmonitored, Uncontrolled Release of Radioactivity to the Environment,"
dated May 6, 1980. However, two recent incidents involving the operation of
radioactive waste concentrators resulted in the radioactive contamination of
the auxiliary boiler system and subsequently, unmonitored, uncontrolled
release offsite. 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 written response is required.
Description of Circumstances:
Oyster Creek (NRC Inspection Report No. 50-219/90-06)
During early 1990, at the Oyster Creek Nuclear Generating Station, an
auxiliary boiler was being operated with radioactively contaminated boiler
water because of a leak in the "A" radioactive waste concentrator. On March
10, 1990, the deaerating feed tank associated with the auxiliary boiler
overflowed onto the boiler house floor. The water that spilled in the
boiler house was treated as radioactive, and actions were initiated by the
licensee to monitor and clean up the spill. Because of standing water in
the floor drains (which were clogged) and the negative results of the
initial surveys of the catch basin, the licensee originally concluded that
no radioactive material had been transported outside the radiologically
controlled area. However, subsequent monitoring at a different location
indicated that a small amount of radioactive water had been released into
the site storm drain. The storm drain system ultimately discharges into
Barnegat Bay.
9106130344
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IN 91-40
June 19, 1991
Page 2 of 3
FitzPatrick (NRC Augmented Inspection Team Inspection Report No. 50-333/91-
80)
On March 18, 1991, at the James A. FitzPatrick Nuclear Power Plant, an
unmonitored release of radioactively contaminated steam occurred through an
atmospheric vent of the auxiliary boiler for approximately 3 hours. The
radioactive materials were inadvertently drawn from the waste concentrator
into the auxiliary boiler system, released to the atmosphere, and resulted
in contamination of site buildings and grounds within the protected area.
Subsequently, some of the contamination was washed by rainfall into site
storm sewers and through the drain system into Lake Ontario.
Before the event on March 18, 1991, the auxiliary boiler had been operating
without detectable activity in the boiler water. The licensee was venting
the auxiliary boiler to the atmosphere (at approximately 9000 pounds per
hour) to increase its load, since operation at low loads made burner
operation difficult. The boiler became contaminated from the "B"
radioactive waste concentrator because operators failed to follow
administrative and radioactive waste concentrator operating procedures, and
a side stream steam supply line (steam agitation line) to the concentrator
had been installed contrary to the system design. While reducing the liquid
waste level in the waste concentrator, operators inadvertently left the
steam agitation valve FCV-02 open (see at-tached drawing). On the indication
of low concentrator level, the steam supply valve FCV-106 automatically
closed, as designed. Because FCV-02 was open and the steam agitation line
was installed downstream of FCV-106 rather than upstream as specified in the
design drawings, a flow path was established from the concentrated
radioactive liquid side to the steam side of the waste concentrator. The
motive force was the vacuum created as the steam condensed on the steam
side. When steam was readmitted to the waste concentrator, the
contamination was flushed to the condensate supply for the auxiliary boiler.
The licensee took samples of the boiler water 1 hour after the release was
terminated and found residual contamination at 3.4 E-2 micro-curies per
milliliter.
The licensee recognized the potential for the unmonitored release through
the storm sewer and took samples which indicated radioactive material
concentrations above the limits for release from the site. The licensee
effectively isolated the storm sewer system with inflatable plugs, securing
the release from the site. The licensee used plastic sheets on horizontal,
flat surfaces to prevent the spread of contamination by runoff or wind
action or by penetration into the soil as a result of the rains.
Contaminated building vertical surfaces were painted with a strippable
coating to temporarily fix the radioactive material on the surfaces. The
strippable coating was later removed and handled as solid radwaste.
Discussion:
In NRC IE Bulletin 80-10, the staff stated that the auxiliary boiler could
become contaminated from the radioactive waste evaporator concentrate tank.
The bulletin recommended that licensees take appropriate action to identify
non-radioactive systems that could become radioactive through system
interfaces and establish sampling and monitoring programs to prevent an
unmonitored,
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IN 91-40
June 19, 1991
Page 3 of 3
uncontrolled release. The events at Oyster Creek and FitzPatrick indicate
that not all licensees took effective actions in response to the bulletin.
The event at FitzPatrick emphasizes the potential for unmonitored,
uncontrolled releases from various sources, including the storm drain
system. The circumstances associated with this release were fortuitous in
that only a small fraction of the radioactive material released to the
atmosphere was released offsite. The small offsite release was attributed
to the high rate of deposition with condensed steam caused by the cold
ambient temperature which occurred during the release and also to the
effective corrective actions taken by the licensee once the release was
identified. If these conditions did not exist, offsite releases (and thus
radiological consequences) would likely have been substantially higher.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate NRR project
manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Richard Plasse, RI
(315) 342-4907
Robert Temps, RI
(315) 342-4041
Kenneth T. Eccleston, NRR
(301) 492-1081
Attachments:
1. Waste Concentrator (WC) B Flow Schematic
2. List of Recently Issued NRC Information Notices
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