ML20082Q637
| ML20082Q637 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 12/05/1983 |
| From: | Draughon C CAROLINA POWER & LIGHT CO., WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20082Q614 | List: |
| References | |
| ISSUANCES-OL, NUDOCS 8312120288 | |
| Download: ML20082Q637 (11) | |
Text
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UNITED STATES OF AliERICA NUCLEAR REGULATORY C0itMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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CAROLINA POWER & LIGHT COMPANY
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Docket Nos. 50-400 OL and NORTH CAROLINA EASTERN
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50-401 OL MUNICIPAL POWER AGENCY
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(Shearon Harris Muclear Power
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Plant, Units 1 and 2)
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AFFIDAVIT OF CLARENCE G. DRAUGHON County of Allegheny
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Commonwealth of Pennsylvania
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CLARENCE G. DRAUGHON, being duly sworn according to law, deposes and says as follows:
1.
My name is Clarence G. Draughon. My business address is P.O. Box 355, Pittsburgh, Pennsylvania 15230.
I am employed by the Westinghouse Electric Corporation as Manager of the Instrumentation and Control Systems Licensing Group in the Nuclear Safety Department of the Nuclear Technology Division (UTD).
I have served in this capacity since January 1933. The statement of my backgrouad and qualifications is attached hereto as Exhibit A.
2.
I was graduated from the U.S. Naval Academy in 1975 with a B.S. degree in Mechanical Engineering. For the past three years I have been employed by the Westinghouse Electric Corporation in the Instrumentation & Control Systems Licensing (I&CSL) group working in the areas of equipment qualification, emergency response capabilities, and control and protection systems licensing.
Included in this work has been the direction of the licensing efforts on the Westinghouse Reactor Vessel Level instrumentation Systen (RVLIS) since January 19E9.
r312120288 831207 PDR ADOCK 050CKb400
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3.
I mako this Affidavit in support of Applicants' Motion for Summary Disposition of CHANGE Contention 44 and Eddleman Contention 132.
I have personal knowledge of the matters stated herein and beliave then; to be true and correct. The first section of the Affidavit describes the role which the Reactor Vessel Level Instrumentation System (RVLIS) plays in the enhanced instrumentation system to detect inadequate core cooling (ICC), and describes the RVLIS design for the Harris plant.
In the following three sections I address the three areas of criticism of RVLIS raised by the intervenors:
margin at error, corrosion and blockage.
RVLIS in the Harris Plant 4.
The NRC has defined an ICC instrumentation system for pressurized water reactors as consisting of subcooling margin monitors, core-exit thermocouples, and a reactor coolant inventory tracking system. See NRC Generic Letter No 82-28. The Westinghouse differential pressure RVLIS is designed to meet the requirement for a reactor coolant inventory tracking system.
5.
During the first stages of a hypothetical I.CC transient, the subcooling margin monitor provides indication to the operator concerning the
-core cooling and inventory state of the reactor coolant system (RCS).
If the RCS subcooling margin drops to zero, this system is no longer an effective means of providing a trend of RCS inventory, or of indicating an approach to core uncovery. During this phase of a hypothotical ICC transient, RVLIS measures the height of liquid in the vessel, and provides the operator with information regarding the trend in RCS inventory and an approach to core uncovery, if depletion continues.
6.
If inventory depletion ccntinues such that the active fuel region of the ccre becomes uncovered of liquid, superheated steam will be generated, which will be observed by the core exit thermocouple system. However, the - _ _ _ _ _ _ _ _
RVLIS also provides a diverse and unique indication to the operator, since it also will provide a direct indication of vessel level, as well as the time dependent trend.
7.
Therefore, the RVLIS provides an indication of trend of reactor vessel ir,,t:.. tory or level during an ICC transient after the time that subcooling is
' lost but before the time the core has uncovered. RVLIS also provides a diverse indication of core uncovery along with the core exit thermocouples, when the core is uncovered. The RVLIS then provides an anticipatory trend indication of oncoming ICC, and confirms the core exit thermocouple
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indications.
- 8. During normal operation, sufF cient subcooling margin exists to prevent the formation of voids in the system, so RVLIS is not required.
In the event of an accident producing a reactor trip and loss of the subcooling margin, RVLIS is designed to detect the presence of significant void volumes, either as a circulating homogeneous water-steam mixture with Reactor Coolant Pumps (RCPs) operating, or as a water level with all RCPs shut down.
9.
The RVLIS utilizes two sets of three differential pressure (d/p) transmitters. These transmitters measure the differential pressure from the bottom of the reactor vessel to the top of the vessel and from the hot legs to i
the top of the vessel. The d/p measuring system utilizes transmitters of differing ranges to cover different behavior with and without reactor coolant pump (RCP) operation.
- 10. When the RCPs are not operating, the d/p measurement orovides an indication of the collapsed water level in the vessel, i.e., as if no steam voids were present in the water phase.
Since residual heat will generate steam bubbles in the core, the true water level which provides effective heat transfer from the core will be higher than the measured level, so the measurement is a conservative indication relative to core cooling. The open 1attice of the core fuel rods provides for radial fluid communication, so the distribution of bubbles at any elevation in the core will be reasonably uniform. When one or more RCPs is operating, voids in the coolant will be circulated as a homogeneous water-steam mixture throughout the system as well as through the core. The d/p measurement provides an indication of the relative void content of this circulating mixture.
- 11. The d/p transmitters are located outside containment to minimize the large increase in measurement uncertainty (temperature, pressure, and radiation) associated with a change in the containment environment during an accident. The d/p transmitters are connected to the RCS penetration taps through a hydraulic system incorporating high volume sensors, capillary ~1ines, hydraulic isolators, and manual isolation valves.
- 12. The pressuie sensing lines extending from the RCS penet. rations are a combination of 3/4-inch Schedule 160 piping (316 stainless steel) and 3/8-inch tubing (316 stainless steel). These sensing lines connect to six sealed capillary impulse lines (two at the reactor head, two at the seal table, and one at each hot leg) which transmits the pressure measurements to the d/p transmitters located outside containment. The capillary impulse lines (316 stainless steel) are sealed at the RCS end with a sensor bellows which serves as a hydraulic coupling for the pressure measurement. The impulse lines extend from the sensor bellows through the containment wall to hydraulic isolators which also functions as a bellows seal thus providing hydraulic coupling as well a~s isolation of the lines. The capillary tubing extends from the hydraulic isolators to the d/p transmitters where instrument valves are provided for transmitter isolation. The capillaries are installed within instrument tubing channels to protect the capillaries from jet impingement and missiles where necessary. - _. -
- 13. The high volume sensors, hydraulic isolators, and d/p transmitters are a' standard stainless steel (316 stainless steel) housing rated at 3,000 psig and factory tested at 4,500 psig. The bellows material of the above devices is also 316 stainless steel. The material was selected to minimize corrosion based upon knowledge and experience with these materials in either a borated RCS coolant or demineralized water. The hydraulic isolator principal gaskets are metallic for preservation of pressure boundaries through the more severe postulated accident conditions.
- 14. The d/p transmitter signals are fed to a microprocessor unit that s
converts the d/p transmitter signal to a reactor vessel level indication when pumps are not running or a relative d/p (void) indication when pumps are running. The microprocessor unit automatically compensates the d/p.
transmitter signals for difference in system density and reference leg density. Strap-on resistance temperature detectors (RTDs) are employed for the vertical reference leg temperature change. The core exit thermocouple signals and RCS wide range pressure are used for system density.
- 15. The compensated level readings are displayed on redundant plasma / graphic displays mounted on the control board. The microprocessor equipment consists of two separate and independent trains located in one cabinet. The cabinet is divided to provide train separation ar.d independence.
Margin of Error 16.- The maximum allowable error for RVLIS wide range and narrow range indications is six (6) percent of the indicated span. This value is acceptable for two reasons. First, real trends in RCS inventory will be detected. For example, with respect to the wide range measurement with reactor coolant pumps on, operator action is required pursuant to the Emergancy Response Guidelines when the wide range inoication drops from 100 percent to approximately 50 percent. This span is large compared to the _ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _
maximum error. Additionally, if the actual is either graater or less than the indicated value due to maximum instrument uncertainties, tha effectiveness of the operator actions is not impaired. Second, the maximum error is small enough such that ICC transients can be detected and distinguished from other non-ICC transients that aay occur.
17.
In order to demonstrate the performance of the Westinghouse RVLIS in providing an indication of the it. vel in the vessel during transient conditiens, the hydraulic components of the RVLIS were installed at the Semiscale Test Facility in Ida..;.
The objective of the demonstration was to show thot RVLIS measurements compare favorcbly with the Semiscale measurements during the tests.
- 18. The Semiscale Test Facility, sponsored by the NRC, is a model of a 4-loop pressurized water reactor coolant system with elevation dimensioris asentially equal to the dimensions of a full-size PWR. Various loss-of-coolant-accident tests, inc?uding ICC transients, have been conducted at this facility. Over 300 pressure, temperature, flow, level and fluid density instruments are installed in the reactor vessel and loops to record the fluid conditions throughout a test run.
- 19. The RVLIS water level measurements obtained during each test run were compared with data obtained from gamma densitometers installed at 12 elevations on the reactor vessel, which provide accurate indications of the two-phase mixture level during the transient. These comparisons confirm that the RVLIS measurement trends with the two phase mixture level and consistently predicts a level below the two-phase level in the vessel.
Based on the broad range of transients tested, the tests confirm that RVLIS will provide an acceptable and useful measurement of the vessel level during small break I
transients, natural circulation conditions, and during the reccvery cortion of _
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large break transients. The test results and conclusicns were endorsed by the Oak Ridge National Laboratory, which reviewed the test program for the NRC.
See NUREG/CR-2623.
- 20. At oae operating plant where RVLIS has been installed, a water level comparison test was performed by injecting nitrogen gas into the reactor
. vessel head. A comparison of the water level decrease detected by RVLIS with the water level increase in the pressurizer showed that the indicated level differed from the calculated level by only about two (2) percent of the instrument span, well within the uncertainties of the system.
21.
It is not required for RVLIS to determine if the core is completely covered. Core uncovery an the order of magnitude of the maximum uncertainty will not result in excessive fuel or fuel clad temperatures, and therefore does not represent an ICC situation. Additionally, the RVLIS is used in conjunction with core exit thermocouples to determine if true inadequate core conditions exist. The RVLIS provides the operator with trending information to indicate whether vessel inventory is improving or degrading.
Corrosion
- 22. Materials of construction (304/316 stainless steel) of the capillary tubing sensors, hydraulic isolators, and differential pressure transmitters and the fill fluid (i.e., demineralized and de-aerated water) wore selected to minimize corrosion based upon general knowledge and excerience with these materials.
Blockage
- 23. Blockage in the core resulting from a significant over-heating will tend to increase the frictional pressare drop and the total differr..tial pressure.across the vessel, resulting in a higher RVLIS indication.
In order for blockage to occur, the core would have to have been uncovered for a
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prolonged period of time. A low RVLIS indication along with a high core exit thermocouple indication would occur prior to this time and appropriate emergency procedures initiated.
- 24. Under natural circulation conditions, the impact of core blockage on the RVLIS indication is minimal. At a natural circulation flow of 4.5 percent, the RVLIS error in level indication due to flow would be about 5 percent of the vessel height with 2/3 of the fuel assemblies completely blocked from top to bottom. Under an equilibrium boi!-off condition, where flow supplied to the core equals the residual heat boil-off flow, the RVLIS error due to flow blockage is negligible. Therefore, even with a large amount of flow blockage, the resulting RVLIS error is small, and the RVLIS will trend with the vessel inventory and provide useful information for monitoring the recovery from ICC.
Conclusion 25.
In summary the NRC has accepted on a generic basis the tiestinghouse RVLIS. This acceptance was based on a thorough and expert review by the NRC Staff and technical consulting assistance which included the review by Oak.
Ridge National Laboratory and extensive testing of the RVLIS at the SEMISCALE Test Facility at the Idaho National Engineering Laboratory. Thesa tests have confirmed that RVLIS provided useful indication for detecting the approach to inadequate corc cooling, that it trends vessel level and provides a direct indication of the li pid and coolant level in the vessel. Therefore, RVLIS is a satisfactory component -- along with proper procedurer,, adequate personnel..
e training, core exist thermocouple instrumentation, and core subcooling nonitor -- of the Inadequate Core Cooling Instrumentation requirement of the kRC's TMI Action Plan, b-Clarence G. Draughon /
Sworn to and subscribed before me this day of December, 1983.
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A ltl4 W h k Notary Public i t.'nuf;!t01:m. NcinY Pt'st!C
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Exhibit A
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Education:
BSME - U.S. Naval Academy, 1975 U.S. Nog Summary / Experience 1975 - 1980 U.S. Naval Nuclear Power Program.
Served on board nuclear submarine as an Engineering Department Division Officer.
Certified as Engineer of Naval submarine nuclear propulsion plant.
Westinghouse Electric Corporation 1980 - 1982 Engineer in Instrumentation & Control Systems Licensing (I&CSL) Group in the Nuclear Safety Department responsible for safety evaluations of safety related instrumentation and control systems including seismic and environmental qualification and preparation of related FSAR sections.
Participated in development and preparation of utility environmental qualification reports in accordance with NUREG-0588 and IE Bulletin 79-01B for Westinghouse utilities and provided engineering assistance in responding to NRC questions.
Provided lead licensing support for Westinghouse equipment on environmental qualification audits and pump and valve operability audits at Jcstinghouse utilities.
Member of AIF working group on Mechanical Equipment Qualification.
Manager of the IaCSL group' responsible for group of 1983 - Present seven evaluation engineers who evaluate the safety of instrumentation and contrc1 systeins, including equipment qualification, emergency response capabilities, reactor protection systens and engineered safety features and preparation of related FSAR sections.
Responsible for direction of the above and licensing activities related to the Westinghouse RVLIS system.
Member of AIF Equipment Qualification Subcommittee.
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