Bulletin 80-17: Supplement No. 2, Failures Revealed by Testing Subsequent to Failure of Control Rods to Insert During a Scram at a BWR
SSINS No.: 6820
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
July 22, 1980
IE Bulletin No. 80-17
Supplement No. 2
FAILURES REVEALED BY TESTING SUBSEQUENT TO FAILURE OF CONTROL RODS TO INSERT
DURING A SCRAM AT A BWR
Description of Circumstances:
At about 3:35 a.m. on July 19, 1980, a manual scram test was initiated at
Dresden Unit No. 3. This test was initiated in accordance with the
requirements of IE Bulletin No. 80-17. The scram itself was accomplished
(i.e., control rods inserted). Following the scram, the Scram Discharge
Volume (SDV) was monitored by UT in accordance with Item #3 of IE Bulletin
No. 80-17. The UT check followed the normal draining of the SDV at a time
when personnel conducting the test believed the SDV to be empty. However,
the UT check revealed the scram discharge west header bank to be 80% filled
with water (i.e., apparently the drain was not successful).
Upon investigation, it appeared that the SDV vent system did not function
due to a stuck ball check valve (i.e., a ball check valve functioning as a
vacuum breaker). This ball check valve is installed in a tee connection
downstream of the vent valve in a one-inch vent header which terminates in
the reactor building equipment drain tank (RBEDT). The ball check valve
provides a vent path to the reactor building atmosphere in the event the
vent header does not. The vent header itself provides a path to other
interconnections and extends into the RBEDT under the surface of water
normally contained there.
Additional information has also resulted from scram testing at other BWRs as
1. At Duane Arnold, the Scram Discharge Instrument Volume (SDIV) drain
valve was found installed so that pressure in the SDIV tended to unseat
the drain valve disk. This resulted in leakage out of the SDIV during
the scram. This was corrected by reversing and reinstalling the valve.
The scram tests were performed on July 12 and 13 and the drain valve
was corrected before return to power operations on July 17, 1980.
2. At the Millstone Unit 1, the scram tests were performed successfully on
July 11 through 14. The function of the 10-second delay on scram reset
(per Item #2.(j) of IE Bulletin No. 80-17) was tested separately from
the scram tests. Review of the separate test results by plant
personnel established that the scram reset delay feature was not
functioning in the scram circuits due to a wiring error on the circuit
boards. This was corrected.
IE Bulletin No. 80-17 July 22, 1980
Supplement No. 2 Page 2 of 2
3. At Browns Ferry Unit No. 1, a test scram involving two rods was
performed on July 19, 1980. The test showed normal response of level
switches in the SDIV. When proceeding to drain the SDIV, however, the
SDV did not empty as required and expected. A vacuum in the SDV
apparently existed which kept the system from draining. Subsequently,
the vacuum was cleared by operator actions and the volume drained
properly. Tests are continuing toward determination of the cause and
to measure the vacuum.
4. At Nine Mile Point Unit No. 1, one rod failed to scram during the
manual scram test on July 14, 1980. This was due to a failure of the
scram pilot valve for that rod.
In view of the above-described events, the following actions in addition to
those specified in IE Bulletin No. 80-17, including Supplement No. 1, are to
be taken by BWR licensees.
1. Each BWR licensee with a SDV vent system that depends on any component
other than the vent valve alone for proper venting must provide an
alternate vent path continuously open to building atmosphere on the
side of the vent valve piping away from the SDV. This alternate vent
path must be positive in its function at all times (i.e., a vent must
be effective regardless of component operability other than the vent
Plants have made corrections by providing a vent through a standpipe
open to building atmosphere. This was done at Browns Ferry Unit No. 3
and is being done at Dresden Units 2 and 3. It is noted that due
consideration to radiological aspects should be included.
An alternate vent path must be provided within 48 hours following the
telephone notification on July 19, 1980 in order to continue or
2. Report in writing within 5 days of the date of this Bulletin Supplement
the confirmation of your action in response to the above. Reports
shall be submitted to the Director of the appropriate NRC Regional
Office and a copy shall be forwarded to the NRC Office of Inspection
and Enforcement, Division of Reactor Operations Inspection, Washington,
More information on the details of the Dresden and Browns Ferry events and
modifications can be obtained by contacting the Dresden and/or Browns Ferry
operating supervision. In addition, we understand that a General Electric
Company task force is available for consultation at (480) 925-3188.
For all boiling water power reactor facilities with a construction permit,
this Bulletin is for information only and no written response is required.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80. Approval was
given under a blanket clearance specifically for identified generic
Page Last Reviewed/Updated Friday, May 22, 2015