ML18136A267
| ML18136A267 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 11/26/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Proffitt W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| NUDOCS 7912070007 | |
| Download: ML18136A267 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION II In Reply Refer To:
- RII:JPO 50-338, 50-339 50-404, 50-405 c.:§Zso, so-}Sb 101 MARIETTA ST., N.W., SUITE 3100 ATLANTA, GEORGIA 30303 NOV 2 6 1979 Virginia Electric and Power Company Attn:
W. L. Proffitt Senior Vice President, Power P. 0. Box 26666 Richmond, Virginia 23261 Gentlemen:
The enclosed Circular No. 79-24 is forwarded to you for information.
No written response is required.
Should you have any questions related to your understanding of the recommendations on this matter, please contact this office.
Sincerely,
- ..-.
- James P.
Enclosures:
- 1.
IE Circular No. 79-24
- 2.
List of IE Circulars Issued in the Last Six Months Director 0
Virginia Electric and Power Company cc w/encl:
e W.R. Cartwright, Station Manager Post Office Box 402 Mineral, Virginia 23117 P. G. Perry Senior Resident Engineer Post Office Box 38 Mineral, Virginia 23117 W. L. Stewart, Manager Post Office Box 315 Surry, Virginia 23883 NOV 2 6 1979 UNITED STATES Accession No: 7910250492 SSINS No. 6830 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 November 26, 1979 IE Circular No. 79-24 PROPER INSTALLATION AND CALIBRATION OF CORE SPRAY PIPE BREAK DETECTION EQUIPMENT ON BWRs Description of Circumstances:
During 1976 the Iowa Electric Light and Power Company identified and corrected a potential problem involving the core spray (CS) pipe break detection system at the Duane Arnold Energy Center (DAEC).
The problem relates to the setpoint, function, and installation of the differential pressure (dp) instrument which monitors for a CS pipe break that is located in the annulus area of the reactor vessel (i.e., located outside the core shroud but inside the reactor vessel).
The installed instrument, range of O - 24 psid, was found deflecting downscale (i.e., reading negative psid) during operation.
The licensee's investigation of the downscale deflection revealed that the original piping arrangement and calibration did not adequately take into account the effect of density changes of the water in the pressure leg connections.
The original installation had the high pressure side of the dp instrument (see attached Figure 1) connected to the reference leg in the vessel (Figure 1 Connection X) and the low pressure side to the core spray piping outside the vessel but inside the drywell (Figure 1 Connection Y).
With the piping intact, this arrangement senses the pressure difference between bottom and top of core.
With a break in CS piping in the annulus area the instrument then senses the additional pressure drop across the separators (dp ~ 7 psi additional) and dryers (dp ~ 7-inches water).
This installation was in accordance with GE design requirements.
Also in accordance with GE instructions the calibration of the dp instrument was performed with the reactor in the cold condition and the alarm was set to trip at 5 psid increasing.
Because of this cold calibration the dp instrument then indicated full downscale negative during operation.
This negative dp was due to the heat up of the reference leg (Figure 1 Connection X) which caused the fluid
.density to decrease as the plant reached hot conditions.
The magnitude of this dp was determined to be about 3.5 psid following completion of the modification discussed below.
IE Circular No. 79-24 November 26, 1979 Page 2 of 3 Adding the 3.5 psi downscale deflection to the 5 psi alarm setpoint results in a total required deflection of 8.5 psi to initiate the alarm at the setpoint.
Since the total dp available across the separators and dryer is only 7 psi (1.5 psi less than the total required deflection), the alarm would not be actuated by a CS pipe break in the annulus.
Therefore, the original installation, including calibration procedure, was deficient.
r To correct the problem, Iowa Electric modified the installation by interchanging the pressure leg connections and resetting the alarm to trip at 2 psid decreasing.
In this orientation it was found that going from cold to hot produced a 3.5 psid positive deflection.
The technical specifications were changed to reflect the revised alarm setpoint.
Further review by the NRC has revealed that the above described lack of trip which precipitated the piping modification and technical specification change at DAEC, exists on other operating BWRs and that BWRs under construction have or will have piping arrangements on the core spray system (i.e., high pressure core spray system on BWR S's and 6 1s) that will potentially generate the same problem.
The specific concern is that failure of the injection piping would not be detected on the plants in question, because the alarm is the only control room indication involved.
The actual differential pressure can only be read at local gauges located on instrument racks in the reactor building.
General Electric has recently sent correspondence to utilities which recommends that:*
"1.
BWR operators, who have differential pressure (AP) instrumentation which reads only positive values, interchange their core spray line break instru-ment connections so that the high side connection is to the core spray sparger sensing line and the low side connection is to the above the core plate sensing line.
This instrumentation should be calibrated for a zero AP reading during cold shutdown; it will then give a positive AP reading during normal rated power operation and a pegged zero reading for a line break indication during normal rated power operation.
Also, when this change is made, the recommended alarm setpoint (on decreasing AP) setting is 0.5 +/- 0.25 PSID; and for those plants that have a value in their technical specifications,> 0 PSID is recommended as a limit.
This change will produce an alarm during normal shutdown.
When the plant is returned to service, clearing of the alarm by a positive AP reading near rated power will indicate that the instrumentation is working.
- 2.
BWR operators, who have installed or who prefer to install AP instrumen-tation (e.g., -10 to +10 PSID) that covers their range of negative and positive AP values and who continue with the instrument high side connected to the above the core plate sensing line, use the same alarm set point of 0.5 +/- 0.25 PSID (and a technical specification limit, if applicable, of< 1 PSID).
The instrument should again be calibrated to read zero AP during cold shutdown."
IE Circular No. 79-24 November 26, 1979 Page 3 of 3 Recommended action for BWR licensee's and permit holders considerations:
All holders of operating licenses for BWR power reactor facilities (other than Duane Arnold) should be aware of the potential problems described above.
It is recommended that the matter be reviewed at your facility in the following respects:
- 1.
If your facility utilizes a core spray leak detection system similar to that described above, determine if the described problems exist. If so, initiate appropriate corrective action at the next planned refueling outage.
- 2.
Propose changes, as appropriate, to those technical specifications which must be revised as a result of your modifying the item above.
- 3.
For interim operations until full corrective measures have been taken it is recommended that direct readings from dp gauges be periodically taken or setpoints changed along with providing necessary instructions to the operators regarding indications from this system.
All holders of construction permits for BWR power reactor facilities should be aware of this potential problem and initiate appropriate modification prior to the initial fuel loading.
This Circular is being forwarded for information to all other power reactor facilities with an operating license or construction permit.
No written response to this Circular is required.
If you need additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
Enclosure:
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IE Circular No. 79-23 November 26, 1979 Circular No.
79-24 79-23 79-22 79-21 79-20 79-19 79-18 79-17 79-16 LIST OF IE CIRCULARS ISSUED IN THE LAST SIX MONTHS Subject Proper Installation and Calibration of Core Spray Pipe Break Detection Equipment on BWRs Motor Starters and Con-tactors Failed to Operate Stroke Times for Power Operated Relief Valves Prevention of Unplanned Releases of Radioactivity Date of Issued 11/26/79 11/26/79 11/16/79 10/19/79 Failure of GTE Sylvania 9/24/79 Relay, Type PM Bulletin 7305, Catalog 5U12-11-AC With A 120V AC Coil Loose Locking Devices 9/13/79 on Ingersoll-Rand Pumps Proper Installation of 9/10/79 Target Rock Safety-Relief Valves Contact Problem in SB-12 8/14/79 Switches on General Electric Company Metalclad Circuit Breakers Excessive Radiation Exposures 8/16/79 To Members Of The General Public And A Radiographer Enclosure.*
Page 1 of 2 Issued to All Power Reactor Operating Facilities and Holders of Reactor Construction Permits All Power Reactor Operating Facilities and Holders of Reactor Construction Permits All Power Reactor Operating Facilities and all Facilities Having a CP All Power Reactor Operating Facilities and all Facilities Having a CP All Power Reactor Operating Facilities and all Utilities Having a CP All Power Reactor Operating Facilities and all Utilities Having a CP All Power Reactor Licensees with a CP and/or OL All Power Reactor Licensees with a CP and/or OL All Radiography Licensees
IE Circular No. 79-23 November 26, 1979 Circular No.
79-15 (Correc-tion) 79-15 79-14 79-13 79-12 79-11 79-10 79-09 LISTING OF IE CIRCULARS ISSUED IN LAST SIX MONTHS Subject Date of Issue Bursting of High Pressure Hose 8/22/79 and Malfunction of Relief Valve "O" Ring in Certain Self-
-Contained Breathing Apparatus Bursting of High Pressure Hose 8/8/79 and Malfunction of Relief Valve "O" Ring in Certain Self-Contained Breathing Apparatus Unauthorized Procurement and 7/13/79 Distribution of XE-133 Replacement of Diesel 7/13/79 Fire Pump Starting Contactors Potential Disel Generator 6/28/79 Turbocharger Problem Design/Construction Interface Problem Pipefittings Manufactured from Unacceptable Material Occurrences of Split or Punctured Regulator Diaphragms In Certain Self Contained Breathing Apparatus 6/27/79 6/26/79 6/22/79 Enclosure Page 2 of 2 Issued to All Research Reactors All Materials Priority I, Fuel Cycle and Operating Power Reactor Licensees All Medical Licensees Except Teletheraphy Medical Licensees and to all Radiopharmaceu-tical Suppliers All Power Reactor Operating Facilities and all Utilities Having a CP All Power Reactors Operating Facilities and all Utilities Having a CP All Applicants for, and Holders of Power Reactor CPs All Power Reactor Licensees with a CP and/or OL All Materials Priority I, Fuel Cycle and Operating Reactor Licensees