Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
April 5, 1989
INFORMATION NOTICE NO. 89-38: ATMOSPHERIC DUMP VALVE FAILURES AT
PALO VERDE UNITS 1, 2, AND 3
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees to potential
failures of main steamline atmospheric dump valves (ADVs). It is expected
that recipients will review the information for applicability to their facil-
ities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information notice do not constitute
NRC require-ments; therefore, no specific action or written response is
required.
Description of Circumstances:
On March 3, 1989, Palo Verde Unit 3 experienced a large load rejection and a
subsequent automatic reactor power decrease from 98 percent to 45 percent
power. The turbine bypass valves opened but the bypass valve controller
malfunctioned, causing excessive steam relief and overcooling of the reactor
coolant system (RCS). A main steamline isolation and reactor trip were caused
by low pressure in the number 2 steam generator. Safety injection and
containment isolation activated upon low RCS pressure. Following steamline
isolation, the ADVs remained closed after operators attempted to open them
first from the control room and then from the remote shutdown panel. The
valves do not receive an automatic signal to open. After the ADVs failed to
open remotely, auxiliary operators experienced difficulty in opening the ADVs
using the handwheels because of the lack of lighting (including emergency
lighting), poor labeling of ADV equipment, poor procedures and training, a
disengaged handwheel, and considerable noise caused by the opening of the main
steamline safety relief valves. The operators partially opened two ADVs.
The pneumatic operators on the ADVs are actuated by using either plant instru-
ment air or a stored, pressurized nitrogen supply. The valves were
manufactured by Control Components, Inc. (CCI). CCI indicated that previous
problems had been experienced in the testing of ADVs at Palo Verde Unit 1 and
other facil-ities. Excessive bonnet pressure caused by abnormally high
leakage past the main valve plug piston ring is suspected to have contributed
to these problems. Foreign particles from the steamlines in the clearance
areas and under the piston ring sealing surfaces may produce the high piston
ring leakage. CCI has developed design modifications to address this problem.
8903300021
. IN 89-38
April 5, 1989
Page 2 of 2
Following the failures of the ADVs to open remotely at Palo Verde Unit 3, the
licensee tested the ADVs at the other two Palo Verde units. Four of the eight
valves failed the functional tests. Preliminary results indicated that there
were problems with valve positioners, possible valve stem binding problems,
and calibration problems with nitrogen pressure regulators. The licensee for
Palo Verde is continuing to investigate the cause of valve failures but has
not yet identified a root cause.
Contributing to the simultaneous ADV failures at Palo Verde is the lack of in-
service testing under hot steam conditions. The valves are routinely tested
during refueling outages with the steamlines cold and depressurized. For
testing, the pneumatic operators are actuated with plant air rather than
with the pressurized nitrogen supply.
Licensees may wish to reassess the frequency of ADV testing and to evaluate
their ADV surveillance test procedures and consider performing the tests under
conditions that better simulate inservice conditions.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the
technical contacts listed below or the Regional Administrator of the
appropriate regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Horace Shaw, NRR
(301) 492-0906
Walton Jensen, NRR
(301) 492-1190
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 89-38
April 5, 1989
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
89-37 Proposed Amendments to 4/4/89 All U.S. NRC
40 CFR Part 61, Air licensees.
Emission Standards
for Radionuclides
89-36 Excessive Temperatures 4/4/89 All holders of OLs
in Emergency Core Cooling or CPs for nuclear
System Piping Located power reactors.
Outside Containment
88-86, Operating with Multiple 3/31/89 All holders of OLs
Supp. 1 Grounds in Direct Current or CPs for nuclear
Distribution Systems power reactors.
89-35 Loss and Theft of Un- 3/30/89 All U.S. NRC
secured Licensed Material byproduct, source
and special
nuclear material
licensees.
89-34 Disposal of Americium 3/30/89 All holders of an
Well-Logging Sources NRC specific
license
authorizing well-
logging activities.
89-33 Potential Failure of 3/23/89 All holders of OLs
Westinghouse Steam or CPs for PWRs.
Generator Tube
Mechanical Plugs
89-32 Surveillance Testing 3/23/89 All holders of OLs
of Low-Temperature or CPs for PWRs.
Overpressure-Protection
Systems
89-31 Swelling and Cracking 3/22/89 All holders of OLs
of Hafnium Control Rods or CPs for PWRs
with Hafnium
control rods.
89-30 High Temperature 3/15/89 All holders of OLs
Environments at or CPs for nuclear
Nuclear Power Plants power reactors.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
..
