Following is an old NRC Information Notice. The history and risks of Upper Head Injection is extensive and I'll have a lot to say about this in future entries. Duke did not immediately abandon its UHI, but it did so in due time. TVA kept its system but ultimately got rid of it. The Japanese kept theirs at OHI for a long time, but they also got rid of it.
Upper Head Injection was installed at Westinghouse Ice Condenser Plants to provide a rapid injection of cooling water in the event of a large break LOCA. Ice condenser plants have a lower back pressure and UHI compensates for this. American electric Power never bought into this for its Cook units.
In Simpson's book, "Nuclear Power from Underseas to Outer Space," he spends one line on UHI on apge 199, "Where this couldn't be done or wasn't enough we proposed an upper head injection system,"
This is my opening salvo that will include my close involvement in a long and interesting history, please stay tuned.
PolInformation Notices > 1985 > IN 85-02
SSINS No.: 6835
IN 85-02
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
January 11, 1985
Information Notice No. 85-02: IMPROPER INSTALLATION AND TESTING OF DIFFERENTIAL PRESSURE TRANSMITTERS
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
Purpose:
This information notice provides notification of a potentially significant
problem pertaining to the improper installation and inadequate functional
testing of differential pressure transmitters.
Such conditions occurred at the McGuire Nuclear Station, Unit 1, when the Barton differential pressure switches utilized to control the isolation valves of the upper head injection (UHI) system were replaced with Rosemont differential pressure transmitters. It is expected that recipients will review the information contained in this notice for applicability to their facilities and consider actions, if appropriate, to preclude similar problems from occurring at their facilities. However, suggestions contained in this notice do not constitute NRC requirements; therefore, no specific action or written response is required.
Description of Circumstances:
On November 1, 1984, Duke Power Company informed the NRC that the UHI isolation valves failed to close when the UHI water accumulator was drained at its McGuire Nuclear Station, Unit 1. At that time, the plant was shut down because the nitrogen content of the water in the UHI accumulator exceeded the limit permitted by its technical specifications. Subsequent
investigations revealed that the four differential pressure transmitters used to sense the level of water in the UHI accumulator and initiate automatic closure of the isolation valves on a predetermined level had been improperly installed. As a result, the isolation valves did not automatically close when the water level in the UFII accumulator reached the set point.
The McGuire UHI system design includes a separate nitrogen accumulator that supplies pressurized nitrogen to force the water from the UHI water accumulator into the reactor vessel during the initial phase of a design-basis loss-of-coolant accident (LOCA). Thus, if the UHI isolation valves fail to close during the course of a design-basis LOCA, nitrogen could be injected into the reactor vessel. To prevent such an event, the differential pressure transmitters are designed to initiate automatic closure of the UHI isolation valves when the water in the UHI accumulator reaches a predetermined level.
8501080502
.
IN 85-02
January 11, 1985
Page 2 of 2
During April of 1984, the McGuire Nuclear Station, Unit 1, Barton
reverse-acting differential pressure switches were replaced with Rosemont
direct-acting differential pressure transmitters to improve the accuracy and
repeatability of the UHI water accumulator level sensing system. However,
the Rosemont differential pressure transmitters were not properly installed
in that the impulse lines were not connected to the appropriate transmitter
ports.
Several factors contributed to the improper installation, including
inadequate installation instructions. The major contributor was inadequate
functional testing of the UHI system after it had been modified in that the
post-modification tests were limited to calibration tests of the differential pressure transmitters. These calibration tests were performed with the transmitters isolated from the impulse lines. Consequently, the tests only verified that the transmitters would provide the required output
signal for a given differential pressure, but they lid not demonstrate that
the transmitters sensed the differential pressures associated with water
level changes in the UHI water accumulator. Thus, the differential pressure
transmitters were not only improperly installed, but the error was not
detected until this event. If a design-basis LOCA had occurred during this
period, the UHI system would have been actuated, but the UHI isolation
valves would not have closed when the water in the UHI water accumulator had
been depleted and nitrogen gas could have been injected into the reactor
vessel during the course of the LOCA.
Similar installation errors have been addressed in Information Notice No. No.
84-45, "Reversed-Differential Pressure Instrument Lines." However, the
majority of events described in that information notice occurred in boiling
water reactors during plant construction and were detected by functional
tests performed before commencing power operation.
In contrast, the event described in this infomation notice occurred at a pressurized water reactor and was undetected during approximately 5 months of power operation.
No specific action or written response is required by this information notice; however, if you have any question regarding this notice, please contact the Regional Administrator of the appropriate NRC regional office or the technical contact listed below.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: I. Villalva, IE
(301) 492-9007
F. R. McCoy, RII
(404) 221-2689
Attachment:
List of Recently Issued IE Information Notices
Today, May 3, 2008, I found the following via GOOGLE. This is another example of loads of dollars that have gone into useless thermal hydraulic testing. These tests were reported during 1979 and apparently the reporting system caught up with this during 2001. The investigators recommend higher temperature for the UHI water. Of course, UHI has been abandoned, however, the recommendation came in 1979 and was never adopted. It is another matter that could drive plant operators nuts.
ROSA (Rig Of Safety Assessment)
Title
Performance test of the upper head injection system at the ROSA-II test facility
Creator/Author
Tasaka, K. ; Adachi, H. ; Sobajima, M. ; Soda, K. ; Suzuki, M. ; Okazaki, M. ; Shiba, M.
Publication Date
1979 Sep 01
OSTI Identifier
OSTI ID: 5425745
Other Number(s)
CODEN: NUTYB
Resource Type
Journal Article
Resource Relation
Nucl. Technol. ; Vol/Issue: 45:2
Research Org
Japan Atomic Energy Research Inst., Tokai, Ibaraki
Subject
220900 -- Nuclear Reactor Technology-- Reactor Safety ;210200 -- Power Reactors, Nonbreeding, Light-Water Moderated, Nonboiling Water Cooled; ;ECCS-- PERFORMANCE TESTING;PWR TYPE REACTORS-- ECCS; HYDRODYNAMICS;TEST FACILITIES
Related Subject
ENGINEERED SAFETY SYSTEMS;FLUID MECHANICS;MECHANICS;REACTOR PROTECTION SYSTEMS;REACTORS;TESTING;WATER COOLED REACTORS;WATER MODERATED REACTORS
Description/Abstract
To evaluate upper head injection system (UHIS) performance during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR), ten UHIS tests were conducted at the ROSA-II test facility.^The experimental results were different from the expected UHIS performance in the following points.^First, flashing took place in the upper head and a mixture level was formed before UHIS actuation.^Second, emptying of the upper head was observed immediately after UHIS shut off.^Third, part of the water which flowed down from the upper head, penetrated into the core and contributed to core cooling at the top part of the core, however, most of the water flowed out through the broken loop hot leg.^In the case of higher injection water temperature (approx.^120/sup 0/C), the fluid behavior in the pressure vessel differed significantly from the results for the low injection water temperature (approx.^20/sup 0/C), and the core cooling was remarkably improved.^Therefore, high-temperature UHIS water is recommended for effective core cooling.^The results described above are due to the following physical phenomena: (1) fluid mixing in the upper head is not good; (2) subcooled water, which flows into places such as the upper plenum where steam exists, causes strong condensation-depressurization which affects the flow behavior and core cooling.^Although the magnitude of the thermal-hydraulic effects observed in the ROSA-II/UHI tests may be unique to this facility, the above two physical phenomena observed are applicable to all PWRs with a UHIS.^Therefore, these two phenomena must be included in a LOCA analysis of a PWR with a UHIS.
Country of Publication
United States
Language
English
Format
Pages: 121-139
System Entry Date
2001 May 13
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment