ML20031D710
| ML20031D710 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 06/22/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20031D662 | List: |
| References | |
| NUDOCS 8110140041 | |
| Download: ML20031D710 (7) | |
Text
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e ENCLOSURE SAFETY EVALUATION REPORT 3.
SUPPLEMENTS 5, 6 AND 7 0F WCAP-7709-L
" ELECTRICAL HYDR 0 GEN RECOMBINER LWR CONTAINMENT" Sumary of Topical Report Westinghouse Electric Corporation has developed and tested an electric hydrogen recombiner to limit hydrogen concentration within a pressurized This water reactor containment following a loss-of-coolant-accident.
recombiner is located inside the containment and consists of a metal sheathed electric resistance heater provfded to heat a continuous flow At this temperature hydrogeri of containment gas mixture to about 1150 F.
reacts with oxygen in the environment to form steam, thereby reducing the The control panel and hydrogen content in the containment atmosphere.
power supply are located outside the containment.
pennanently installed inside of The recombiner:; are designed to be containment and are not intended to be used for sharing between tw or more units.
not take into account vibratory and impact loads that would be imposed during transportation in addition to the loads that would be imposed during a seismic event.
WCAP-7709 L provides a description of the electric hydrogen recombiner, Supplement 1 to design criteria, design bases and_ performance analyses.
WCAP-7709 L provides a description, analysis and results of performance tests of a prototype recombiner under conditions simulating post-LOCA Supplement 2 to WCAP-7709 L provides a conditions inside containment.
description, analysis and results of tests to qualify the recombiner for Supplement 3 seismic loads and loss-of-coolant-accident environments.
provides a description, analysis and results of long term te s
Supplement 4 provides a description, analysis, and ment (21 days).
results of perfonnance tests of a production unit to demonstrate its capa-bility to operate when sprayed with sodium tetraborate and to successfully recombine hydrogen and oxygen.
The staff has previously reviewed WCAP-7709 L through Supplement 4, andle for u found the Westinghouse recombiner functionally acceIn addition, environ 323-1971," General power plants.
found to be acceptable based on the requirements of IEEE Trial - Use Guide for Qualifying Class IE Electrical Equipment for Nucle Power Generating Stations" and IEEE Qualification of Class IE Electrical Equipment for Nuclear Power Generating Our safety evaluation was transmitted to Westinghouse by letter In that evalua-Stations".
dated May 1, 1975 from D. B. Vassallo to C. Eiche1dingen.
tion we concluded that additional documentation would be required for 811014
. 811009 yDRADL 05000
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plants committed to meet IEEE-323-1974 "IEEE' Standard for Qualification of Class IE Electrical Equipment for Nuclear Power Generating Stations".
This standard includes both seismic and environmental qualifications.
Supplements 5, 6, and 7 to WCAP-7709-L provide additional documentation to demonstrate conformance of the Westinghouse electric hydrogen recombiner to the requirements of IEEE 323-1974.
Supplement 5 provides the results of tests to demonstrate design margin, capability to withstand containment leakage tests, and capability to operate during an earthquake.
Supple-ment 6 compares the tests and analyses performed for the recombiner with the requirements in IEEE 323-1974 to demonstrate conformance.
Supplement 7 prnvides results and analyses of additional tests to demonstrate accept-ante of auxiliary equipment for the recombiner (power supply, control panel, power cables, cold reference junction box, and automatic temperature controller).
Our evaluation of Supplements 5, 6, and 7 to WCAp-7709-L are provided below.
Sumary of Reculatory Evaluation Infonnation in Supplements 5 and 6 is intended to show that the Westinghouse electric hydrogen recombiner is in conformance with IEEE 323-1974.
Type testing (recommended in IEEE 323-1974 as the preferred method), was primarily used to qualify the Westinghouse recombiner.
The tests and analyses performed by Westinghouse adequately, demonstrate that the recombiner, excluding the control
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panel and power supply, meets the following specific requirements of IEEE 323-1974.
1.
The eauioment shall be operated to the extremes of performance and electrical characteristics.
3 The recombiner was operated at higher thannormalgemperatures(1450Fversusthenormaloperatingtempe5a-ture of 1200 F).
We noted in our May 1,1975 evaluation that 1450 Fg l
gas temperature corresponded to a maximum sheath temperature of 1600 F (rated sheath temperature) and that this temperature was achieved with 66 kilowatts power supplied to the heaters.
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'1 Supplement 5, additional over# temperature tests were successfully run with tge heater at maximum power level and sheath temperatures up to 1750 F.
We conclude based on the tests, that the heaters l
will operate satisfactorily with the maximum power of 75 kilowatts l
supplied to the recombiner.
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3-2.
Equipment shall be aged in accordance wi h Section 6.3.3 of IEEE 323-1974 to put it in a condition which simulates its expected end-of qualified life condition...
The recombiner inside containment is composed primarily of metallic structural material, metal-enclosed thermal insulation, metal clad ceramic heater elements, and power cables.
Since the recombiner is in a normal containment atmosphere and subjected to periodic testing, Westinghouse concluded that the most significant aging factor was the fatigue life of ~ the structure, due to thermal stresses induced by the periodic heat up and cool down tests (i.e., the recombiner would not deteriorate significantly due to normal atmospheric conditions alone). The recombiner structure was subjected to 80 thermal cycles, corresponding to 40 years of expected periodic testing, and was found to be in good operating condition.
We conclude that the recombiner structure.vas satisfactorily tested to demonstrate acceptable end of life condition. The power cable inside containment was tested in accordance with IEEE Std 383-1974 and after reviewing the details of the tests performed, we conclude that the irradiation, steam, and alkaline spray conditions were sufficiently severe and the cables were acceptably qualified.
3.
The aged equipment shall be subjected to mechanical vibration...
The Mechanical Engineering Branch has evaluated the mechanical vibration tests conducted on the " aged" equipment.
The concept of aging was addressed explicitly for the first time in IEEE-Std. 323-1974.
The aging guidance therein reflects the requirements of IEEE Std. 279-1971 Sec. 4.4.
The objective of aging is to put samples in a condition equivalent to the end-of-life condition.
For the initial seismic tests reported in WCAP-7709-L, Supplement 2, it was assumed that the recombiner is in the de-energized mode since, for PWR containments, the recombiners are not energized for approxi-mately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the DBA.
A seismic analysis of the recombiner heater element is presented in Appendix B of Supplenent 5 to WCAP-7709-L which demonstrates analytically that the recombiner would function adequately under seismic conditions while it is energized and is in ca' ? tion.
In this analysis the natural frequency of the heater ele-mei.ts are calculated to be 250.5 cps for built-in ends and 112.0 cps for simply supported ends.
Static loadings equal to 5.6g horizontal and 2.59 vertical (1.5g seismic + lg weight) are applied in the analysis.
The stresses are determined to be 1322 psi and 607 psi in the horizontal and vertical directions, respectively, which are much lest than the o
yield strength of 13500 psi for Incoloy 800 tubing at 1600 F.
This tubing forms the metal cladding of the heater element assembly and since it is the most highly stressed part of the assembly, heater elements are acceptable for the hot seismic condition. The midspan deflections and the clearance between heater elements and holes in u-rwv--
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An additional vibration test of a production recombiner is described in WCAP-7709-L, Supplement 5 in which the recombiner was energized and at temperature before, during and after the vibration test. This test confirms the analysis of the heater elements discussed earlier.
The equipment was vibrated in 3 directions, horizontal side-to-side, horizongalfront-to-backandvertical. The recombiner was maintained at 1250 F tl.roughout and after the test. The test input was of the sine beat wave form type and was performed at resonant frequencies, determined by a frequency search test performed from 1 to 35 Hz plus additional frequencies described in the report.
The test method used is a single frequency method (described in IEEE 344-75 Section 6.6.2.3).
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The single frequency sine beat method is justified for this application on the basis that the resonances are widely spaced and do not interact to reduce the fragility level, as permitted in Section6.6.2 of IEEE 344-75.
The single axis test is justified on the basis that the tests conser-vatively reflect the seismic loadings at the equipment mounting locations.
A comitment is made in the report that for each plant application, the required seismic response spectrum for that plant will be checked against the test response spectrum to verify that the test response spectrum envalopes the required response spectrum. This is consistent with the requirements of Regulatory Guide 1.100.
4.
The aged equipment shall be operated while exposed to a simulated DBA...
A series of tests were performed on the portion of the production recombinerthatislocatedinsidethecontafnment,includingseveral post-LOCA pressure transients (69 psia, 302 F) and long term steam tests to demonstrate that the recombiner can successfully withstand the post-LOCA environment.
In addition, alkaline solution was sprayed on the recombiner during operation. These tests have been accepted by the staff for qualification of the Westinghouse electric hydrogen recombiner because the recombiner has no temperature sensitive electrical components required to operate during the portion of the post-LOCA pressure transient whereinhightemperaturesexistsgndthemaximumexpectedsteamtemperature following a steam line break (420 F) is not likely to cause structural failure of the recombiner.
5.
The equipment shall be operated while exposed to the simulated post-accident conditions...
To show the long tem capability of the heater banks to operate in the post-LOCA environment, two heater banks were subjected to a DBA plus 12 months of simulated post-LOCA environment.
The test showed that the individual heater elements and banks plus thermocouples, electrical cabling, and themocouple junction boxes which are susceptible to steam would perfom satisfactorily.
v Supplement 7 to WCAP-7709-L is the last in the series of reports for the Westinghouse electric recombiner and contains qualification results for the recombiner power cable located inside tontainments, the recombiner control and power supply panels located outside containments, and additional optional features including a cold reference junction box and an automatic temperature control device which may be selected by an applicant.
The qualification of the control panel and power supply located Lutside the containment does rot meet our interpretation of the aging requirements set forth in IEEE Std 323-1974. However, tests perfonned on the control panel and power supply located outside thg containment included short-tenn high temperatuSe exposure (10 days at 155 F for the control panei and 10 days at 135 F for the power supply). We found the qualification of the control panel and power supply acceptable, based on these tests and also based on the accessibility of these components for repair following a LOCA.
The recombiner will not be'needed for several days following a LOCA and since these components will be easily accessible, repair of components that may fail can be acccmplished.
Seismic tests of the control panel and power supply were perfonned to demonstrate conformance to IEEE 344-1975 "Recomended Practice for Seismic Qualification of Class IE Equipment for Nuclear Power Generating Stations".
IEEE 344-1975 recomends that seismic tests be performed using biaxial motion and both random frequency and sine beat input. The power supply and control panels were mounted on the drive plate of a vibration table and energized. The test series consisted of resonance frequency search plus five OBE's followed by an SSE.
The input for the five OBE's was a biaxial, random frequency while the SSE was a biaxial sine beat input, the maximum "g" level being 0.2.
The magnitude of the vertical acceleration was kept to two-thirds the magnitude of the horizontal acceleration. The.
input was made of decaying sinusoids covering the frequency range of 1.25 to 3.50 Hz. The sine beat test was performed at each resonance frequency and at eleven other frequencies ranging between 1.25 and 33.5 Hz. These tests were run four times (once for each equipment mounting direction) without component failure. We find these tests acceptable.
The power cables for the recombiner were tested along with the heater banks in the post LOCA steam and spray environment and seismically tested with the recombiner. The testing did not completely conform to the procedure outlined in IEEE 383-1974, " Standard for Type Tests of Class IE Electric Cables, Field Splices and Connections for Nuclear Power Generating Stations".
To meet the requirements of Section 2.4 of this standard, which deals with environmental exposure, a series of tests were performed on the power cables which included thermal aging, irradiation, post LOCA containment steam and spray exposure and voltage tests. We find these tests acceptable.
The cold reference junction box is for use in those containments which have copper conductors through containment penetrations already installed.
l The usage of a compensator in the junction box allows the chromel-i alumel leads from the recombiner to be connected to copper leads inside 1
m 6-the junction box. The copper leads can khen be run through a typical copper penetration to the. control panel, thus eliminating the need to replace installed copper penetrations with chromel-alumel penetrations.
The cold reference junction box, with the exception of the compensator, has been tested for the same range of conditions as-the tests that were performed on the recombiner. The compensator it: elf was irradiated and placed in a steam environment for a short period of time. Since the compensator (a wire-wound resistor encapsulated in a ceramic type material) does not have temperature sensitive elements ih it and since the compensator is used only to provide the operato; with an approximation of the tem-perature of the heater inside the recombiner and has no control functions, we find the qualification tests of the cold reference junction box to be acceptable.
The automatic temperature control feature is an option which allows the power level to be controlled by feedback signal from the recombiner thermocouples.
It consists of minor wiring modifications within the control panel and addition of a printed cicuit card to the temperature indicator. Because the changes that would have to be made in the design of the control panel to add the automatic temperature control feature are minor, we find this concept acceptable from a qualification standpoint.
However, the use of this device to control a recombiner system that also incorporates the cold reference junction box would mean that a compensator in the junction box would be relied upon for control purposes.
To alleviate this problem Westinghouse has agreed not to allow the use of the automatic temperature control device except during periodic tests.for those plants that choose to use the cold reference junction box.
We find this approach acceptable.
l Regulatory Position Based on our review of WCAP-7709-L, we have concluded as follows:
(1) The Westinghouse electric hydrogen recombiner, (excluding the control l
panel, power supply and the optional automatic temperature control l
and cold reference junction) meets the requirements of IEEE 323-1974.
(2) The control panel and power supply are acceptable on the basis of h'igh temperature exposure tests and also because there would be adequate accessibility and time for repair, if necessary, following a loss of coolant accident before they would be required to operate.
(3) The recombiner, control panel and power supply meet the requirements of IEEE-344-1975.
(4) Power cables meet the requirements of IEEE-383-1974.
(5) The optional automatic temperature control feature is acceptable for use on all plants except those which use the cold reference junction box.
For plants using the cold reference junction, automatic temperature control may be used for periodic tests but must be disconnected at other times during plant operation.
(6) The cold reference junction box is acceptably qualified to provide approximate heater temperature indication to the operator; however, it is not qualiited for control functions.
1 Westinghouse report Ws'Ap-7709-L and Supplements 1 through 7 may be refer-enced in applications to support the above conclusions where the calcu-lated accident environmental conditions and plant seismic response spectrum are enveloped by the conditions for which the recombiner is qualified.
Each application referencing this topical report shall either include information to demonstrate that environmental and seismic conditions for that plant fall within the accepted envelope conditions of WCAP-7709-L, or provide further analyses or tests to demonstrate acceptability.
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