ML20133F993
| ML20133F993 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/31/1978 |
| From: | Joshua Wilson WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19269B549 | List: |
| References | |
| CIVP-S-031, CIVP-S-31, WCAP-9347, NUDOCS 8508080521 | |
| Download: ML20133F993 (40) | |
Text
_._.
l WESTINGHOUSE PROPRIETARY CLASS 3 E8 ci.
oa QUALIFICATION TESTING FOR MODEL B ELECTRIC HYDROGEN RECOMBINER J. F. Wilson July 1978 Work performed under Shop Order EJSP-917 WESTINGHOUSE ELECTRIC CORPORATION Nuclear Energy Systems P. O. Box 355 8508080521 850802 Pittsburgh, Pennsylvania 15230 PDR TOPRP EMVWEST C
PDR S
l TABLE OF CONTENTS Section Title Page 1
INTRODUCTION 11 2
CHANGES TO THE MODEL A RECOMBINER WHICH HAVE BEEN INCORPORATED IN THE MODEL B RECOMBINER 2-1 2-1.
Changes Recognized as Desirable During Qualification Testing 2-1 2-2.
Changes to Facilitate Installation 21 2-3.
Changes to improve Manufacturing 2-3 3
QUALIFICATION TESTS 3-1 3-1.
Performance Tests 3-1 3-2.
Heatup Test 3-1 3-3.
Air Flow Test 3-1 3-4.
Aging Test - 100 Heatup and Cooldown Cycles 3-4 3-5.
Seismic Test 3-4 3-6.
Hydrogen Tests 3-6 3-7.
Spray Tests 3-6 4
SUMMARY
OF QUALIFICATION TESTS 4-1 4-1.
IEEE 344-1975 (Seismic Qualification) 4-1 iii
9 LIST OF ILLUSTRATIONS Figure Title Page 2-1 Heater Comparison Test, Models A and B 2-2 3-1 Temperature Versus Power 3-2 3-2 Air Flow Test 3-3 3-3 Random Frequency Test 3-5 3-4 Sine Beat Input for Testing 3-7 35 Acceleration Versus Frequency 3-8 3-6 Accderation Frequency 3-9 3-7 Test Equipment Orientation 3-10 3-8 Seismic Test in Test Direction #1 3-11 3-9 Test Facility (Schematic) 3-13 1
A-1 Electric Hydrogen Recombiner A-2 A-2 Typical Heater, Electric Hydrogen Recombiner A-4 s
1
LIST OF TABLES Table Title Page A-1 Electric Hydrogen Recombiner Model B, Typical Parameters A3
?
vii
SECTION 1 INTRODUCTION The Model B recombiner is a technologically improved revision of the Model A recombiner (present model). The Model B recombiner uses the same principle of thermal recombination with flow induced by natural convection ~ as the Model A. The flow arrangement through the Model B is the same as the Model A and in outward appearances, the two are very similar.
The Model A recombiner was designed in 1971 and has been subjected to an extensive qualification test program as described in WCAP-7709L, Supplements 1 through 7. No changes which would affect the qualifications were permitted on the Model A recombiner. Suggested changes to improve the recombiner were accumulated from 1971 to 1976 and then incor-porated in a Model B recombiner. A test program has been performed to qualify the features of the Model B recombiner that have been incorporated as changes from the Model A. A complete description of the Model B recombiner is given in appendix A. It should be noted that the power supply and control panel are the same for Models A and B.
The Model A recombiner was approved by the Nuclear Regulatory Commission to be qualified in accordance with IEEE 323-1974, subject to the conditions in the Staff evaluation.
(John F. Stolz, USNRC to Thomas M. Anderson, Westinghouse, June 22, 1978) l 11
SECTION 2 CHANGES TO THE MODEL A RECOMBINER INCORPORATED IN THE MODEL B RECOMBINER The following changes have been made in the Model A design. They are grouped into three categories based on the reason for the changes.
2-1.
CHANGES RECOGNIZED AS DESIRABLE DURING OUALIFICATION TESTING e
Redesigned support structure, running the main vertical structural members the full height of the recombiner rather than only to the top of the heater section. This stiffens the structure, Fastened side panels to main structure by welding rather than bolting to stiffen the m
structure.
Four heaters banks with increased power capability are used, rather than five banks.
m Tests on the Model A show that disconnecting the fifth bank (i.e., the top heater, which generates only 5 kw) does not affect the temperature distribution within the recombiner. This is shown in figure 2-1.
m Redesigned flow channel so that there is more space between heater banks. This pro-motes mixing which results in a more uniform gas temperature and increases gas ve-locity slightly, a
Modified louver blade shape to increase stiffness, a
The length to the power cables was reduced by rerouting cables; however, the same cabling as previously qualified to IEEE 3831974 was used.
2 2.
CHANGES TO FACILITATE INSTALLATION Reduced height of the recombiner to 98 inches. This reduced the installed head m
room required and made it possible to ship the units on a standard truck rather than a special truck.
Enclosed the thermocouple junction box and the power lead junction box within m
the recombiner so that they do not protrude from the recombiner. This leaves a smooth exterior surface on the recombiner and facilitates shipping without damage; it also reduces the area required for installation and improves the appearance of the recombiner.
2-1
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2 3.
CHANGES TO IMPROVE MANUFACTURING The base structure and electrical junction box of the Model A recombiner was made e
from carbon steel which was then painted. In practice, the painting of these compo-nents caused a problem in selecting paint systems and colors to match various con-tainments. it was decided that these components in the Model B should be made of stainless steel; this eliminates the time-consuming process of selecting the proper paint colors and painting procedures for each application.
The heater frame on the Model A prototype was made from incoloy 800 and the m
heater frame of the Model A production Model was Inconel 600. Both units were qualified for high-temperatures application. In 1971, it was decided to use inconel 600, since the manufacturing group felt it would be easier to fabricate (Both alloys have good high temperature, corrosion resistant properties). Since 1971, the Inconel structural members have become more difficult to obtain. (They are rolled only one time per year and now the production on some members has been discontinued.)
These structural members have been eliminated in the heater frame of Model B and incolay 800 has been substituted. This material was used satisfactorily in the Model B fabrication and qualification testing.
The thermal insulation system has been redesigned to facilitate insulation installation m
and to remove air spaces that existed in the Model A recombiner. The result has been a more compact design which slightly reduces the size of the recombiner.
23
SECTION 3 QUALIFICATION TESTS The following tests were perforr1ed to requalify the electric hydrogen recombiner. All tests were performed on the first unit of the Model B recombiner.
3-1.
PERFORMANCE TESTS 3-2.
Heatup Test The purpose of this test was to measure the power required to reach recombination tempera-ture. For this test the recombiner was connected to a recombiner power supply and control panel. Power was then applied in increasing steps. A plot of recombiner temperature as measured in the hottest zone versus power is shown in figure 3-1. This shows that recom-bination temperature is reached at 49 kW, which leaves a 26 kW reserve of the 75 kW total.
3-3.
Air Flow Test The purpose of this test was to measure the air flow through the recombiner to ascertain that the flow rate was equal to or greater than 100 scfm (14.7 psia, 70 F). For this test, the re-combiner was connected to a power supply and control panel. The recombiner was heated up 0
to 1250 F and the air flow measuring duct, shown in figure 3 2, was attached to the recom-biner. (This is the same equipment used on the Model A). The duct decreases the flow area and thus increases the air velocities to values which can be measured using standard air veloc-ity measuring devices. To compensate for the pressure loss imposed by this duct, a tell-tale in-dicator was placed in the measuring duct adjacent to the recombiner inlet. This indicator is a lightweight vane (made of paper) which indicates differential pressure in that it will be pushed in the direction of the greater pressure, i.e., between the measuring duct and surrounding air.
For testing, the exhaust of a fan was directed at the duct inlet so that no differential pressure existed across the measuring duct at the recombiner inlet, thereby cancelling the effect of the measuring duct pressure losses. Flow measurements were made by traver:;ing the duct with a flowmeter. The flows measured were well in excess of the design value of 100 scfm. The flow was measured as 115 scfm at 12500F.
31
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34.
Aging Test - 100 Heatup and Cooldown Cycles During the recombiner's 40-year design life it will be subjected to approximately 80 heatup and cooldown cycles to demonstrate its availability (approximately 2 cycles per year). These heatup and cooldown cycles result in transient thermal stresses which are very difficult to analyze. A test program was conducted to demonstrate that the recombiner structure would not be damaged by these thermal stresses. The test consisted of connecting the recombiner to a control panel and power supply and alternately heating the recombiner to 1250'F and then coolinrj to approximately ambient temperature. This cycle was repeated 100 times. After the cycle test was completed, the recombiner was examined for damage, such as gross warp-age and cracks in the structure and welds. Inspection showed there were no cracks in the structure or welds and that there was no panel warpage.
3 5.
Seismic Test The purpose of this test was to demonstrate that the Model B recombiner will perform its intended function after five Operating Basis Earthquakes (OBE) and one Safe Shutdown Earthquake (SSE) in accordance with IEEE 344-1975.
The seismic test was performed using biaxial motion and both random and sine beat input frequencies. The tests were conducted at the Westinghouse Advanced Energy Systems Divisions seismic test facility located at Large, Pennsylvania. The recombiner was mounted on the drive plate of the vibration table using the same mounting connections as recommended for installa-tion in a reactor containment. The test series consisted of a resonance frequency search, foi-lowed by five OBE's using biaxial motion and random frequency input. Following this, four biaxial sine beat and four random motion tests were conducted at SSE level accelerations. The angle of motion of the table was set to produce vertical accelerations equal to the horizontal accelerations for the sine beat and random motion tests; four separate tests were run. First, 0
the equipment was mounted 45 to the horizontal plane of motion, then rotated 90 for each of the next three test runs in accordance with paragraph 6.6.6 of IEEE 344 1975.
The acceleration levels for the random frequency OBE and SSE tests are shown in figure 3-3.
The input motion was made up of decaying sinusoids covering the frequency range of 1.25 to 35 Hz. Following the random frequency tests, each of which lasted 20 seconds, a series of four biaxial sine beat tests were performed at each resonant frequency and at the following frequencies: 1.25,1.75, 2.5, 3.5, 5, 7, 9.5,13,18, 24.5 and 33.5 Hz.
A sine beat test consisted of five beats, each containing 10 cycles as shown in figure 3 4. The peak horizontal input accelerations are shown in figures 3 5 and 3-6. (These are input accelera-tion, not response spectra.) The equipment orientation on the drive plate for all testing is shown in figure 3 7. Accelerometers were located on the frame structure near the top and under the upper louvers. Figure 3-8 shows a photograph of the equipment in the drive table.
34 3
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Random Frequency Test 35
For all tests, the recombiner was energized and at operating temperature before, during, and after each vibration test. Following the entire test series, the recombiner was inspected for damage. No disabling damage was found. (Some fine thermal insulation material was found on the floor of the recombiner and no other surfaces.) An air flow test was then conducted and results show no loss of air flow.
This test conforms to the requirements of IEEE 344-1975.
3 6.
Hydrogen Tests The purpose of this test series was to demonstrate the safe operation of the Model B recom-biner in an air-hydrogen atmosphere and to measure the hydrogen removal rate. To perform this test, a special test facility as shown on figure 3 9 was constructed. This facility includes i
a pressure vessel to house the recombiner, hydrogen and air injection equipment, and a spray system. The facility enabled recombiner testing under closely controlled environmental condi-tions in a safe manner.
For the test, the Model B recombiner was connected to a production power supply and con-trol panel located remotely from the test facility.
The procedure for a typical test run was to energize the recombiner and bring the tempera-ture to 1225 F. The facility blower was actuated to provide cooling air to the recombiner.
When the temperature had been stabilized for 30 minutes, hydrogen was injected and samples from the inlet and outlet of the recombiner were analyzed. (The power setting was not changed during the hydrogen test run). The thermocouples on the heaters were read after the temperatures stabilized. This test was repeated for hydrogen concentrations ranging from 1 v/o to 4.5 v/o hydrogen. Test results show that for 4 v/o hydrogen, the recombiner removes 4 cfm hydrogen. (No measurable hydrogen at the outlet). The temperature stabilized at 14740F at 4 v/o hydrogen, which is well below the temperature at which the heater elements were b
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3-7.
Spray Tests Following a LOCA, some containment safeguards systems use a spray system to control the containment environmental conditions. Since the recombiner is located inside the containment, it is subject to spray impingement.
The purpose of this test was to demonstrate that the recombiner will operate satisfactorily in post LOCA containment spray environment for an extended period of time.
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The test facility used for this test is shown schematically on figure 3-9. The spray solution l
used was sodium tetraborate which contained 2500 ppm boron as boric acid and sodium hy-droxide to bring the solution to N pH 10. The spray rate at the intake louvers was set at 0.15 gal / min per square foot of horizontal area. The spray rate throughout the rest of the re-combiner area was approximately the same.
For this test the spray system was actuated and then the recombiner was energized and brought to 1225 F in the spray. The spray test was continued for [
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the end of this time, hydrogen was injected into the containment. Results show no significant 1
amount of spray residue accumulation on the recombiner inlet and flow through the unit, as measured by electric power required to maintain temperature, was not effected. These results are the same as for the Model A recombiner. Following the spray test, a two percent air-hydrogen mixture was processed with no detectable hydrogen at the recombiner exit.
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l SECTION 4
SUMMARY
OF QUALIFICATIONS TESTS The recombiner power supply and control are unchanged from the Model A design so the environmental and seismic qualifications of these equipment items remains unchanged. These qualifications are surnmarized in WCAP 7709L Supplement 6Ill with additional testing de-scribed in Supplement 7.I2}
Certain major hardware items on the recombiner are unchanged. These are:
Heater element design (except length reduced by 9 inches) u e
Heater bank terminal end design Thermocouples and mounting design.
a Therefore, the extensive testing performed on the heater design for Model A applies to Model B.
These tests include aging in steam for one year, high temperature tests, overpressure tests (for containment leak tests), irradiation tests, long term operation simulating post LOCA duty.
Hardware and structure items which require requalification are:
a Recc..ioMer support structure H tater Frame structural design a
a Louvers e
Orifice plate flow control e
insulation (thermal) 1.
Wilson, J. F., " Electric Hycirogen necombiner IEEE 323 1974 ovelification". WCAP 7709L Suppl. 6. oct.1976
- 2. Wilson, J. F., " Electric Hyttrogen Hecombiner Lwr. Containments Supplemental Test Number 2". WCAP.7709L Suppl. 7, oc t.197 7 41
a-e Heater bank mounting design e
Power Cable Junction Box and T/C Junction Boxes.
These items must be qualified to IEEE 323 1974 and IEEE 344-1975, in the following paragraph, the requirements of IEEE 344-1975 and IEEE 323-1974 are compared with the tests performed on the recombiner.
4-1.
lEEE 344-1975 (SEISMIC QUALIFICATION)
This Standard establishes recommended practices to verify that the equipment will meet its performance requirements during and following one safe shutdown earthquake (SSE) preceded by a number of OBE's (operating basis earthquakes). The Standard lists several methods for accomplishing this verification. The method selected for qualification of the recombiner is as follows.
Since the recombiner is supplied for a number of applications, fragility type testing was per-formed using acceleration values much higher than would be expected for any particular plant application. The acceleration values used were selected from experience in examining seismic specifications for a number of plant applications for which the Model A recombiner was supplied. The specification for the proposed Model B applications will then be compared with the test accelerations to verify that the applicable portions of the Required Response Spectra (RRS) are enveloped by the Test Response Spectra (TRS). The TRS for the Model B recombiner is derived from the drive plate input spectra shown on figures 3 5 and 3 6.
4-2.
QUALIFICATION TO IEEE 323 1974 The Model A recombiner qualification program was described in WCAP 7709L Supplement 6.
The qualification requirements and application requirements are reproduced in the following section:
The requirements for qualifying the recombiner are described in IEEE Standard 323 1974.
The recombiner has been qualified primarily by type testing the first production unit. Some analysis was performed to demonstrate performance under environmental conditions which would be difficult to simulate in the laboratory. Since the recombiner is provided for a number of plant applications, the test conditions used were the most severe conditions that could be postulated for any foreseeable plant. The requirements for a particular plant can be compared with actual test conditions to assure individual plant compliance. Margin requirements, as noted in Section 6.3.15 of IEEE 3231974, are taken into consideration in this evaluation, t
42
The sequence for type testing is listed under paragraph 6.3.2 of IEEE 3231974. This para-9raph is as follows:
6.3.2 Test Sequence (From IFEE-323-1974)
The type tests shall be run on the equipment in a specified order. For most equipment and applications, the following constitutes the most severe se-quence; however, the sequence used shall be justified as the most severe for the item being tested.
(1) Inspection may be performed to assure that a test unit has not been damaged due to handling since manufacture and to determine basic dimensions. This inspection shall not be directed to select a specific unit for type testing.
(2) The equipment shall be operated under normal conditions to provide a data base for comparison with performance under more highly stressed conditions. Certain measurements, such as drift (rate of change with time) of a parameter may be made at this time.
(3) The equipment shall be operated to the extremes of all performance and electrical characteristics given in the equipment specifications, ex-cluding design basis event and post design basis event conditions, unless these data are available from other tests on identical or essen-tially similar equipment.
(4) Equipment shall be aged in accordance with Section 6.3.3 to put it in a condition which simulates its expected endof-qualified 4ife condition including the effect of radiation (design basis event radiation may be intluded). If the required radiation level can be shown to produce less effect than that which would cause loss of the equipment's Class IE function, radiation need not be included as part of aging. Certain key measurements should be made, following aging, to determine if the equipment is performing satisfactorily prior to testing.
(5) The aged equipment shall be subjected to such mechanical vibration as will be seen in service. This should include simulated seismic vibra-tion (see IEEE Std. 344 1971), self induced vibration (see IEEE Std. 344 1971, Trial Use Guide for Type Test of Class 1 Electric Valve Operators for Nuclear Power Generating Stations), or vibration from other causes (such as might be seen by pipe mounted equipment).
(6) The aged equipment shall next be operated while exposed to the simulated design basis event (Section 7) (radiation may be excluded if incorporated in (4) abovel. Those functions which must be per-formed during the simulated design basis event shall be monitored.
43
l (7) The equipment shall then be operated while exposed to the simulated post accident conditions (following exposure to accident conditions).
Those functions which must be performed following the simulated design basis event shall be monitored during this simulation.
(8) Disassemble, to the extent necessary for the inspection of the status and condition of the equipment and record the findings.
The requirements for aging are described in paragraph 6.3.3 of IEEE-323-1974, and in the Addendum to Foreword to IEEE-3231974, which are as follows:
6.3.3 Aging The objective of aging is to put samples in a condition equivalent to the end-of-life condition. If previous aging of various devices exists, it can be utilized provided these data are applicable and lustifiable in regard to the service conditions that are required by the perfoo mance specifications of the device to be type tested.
A short period of accelerated thermal aging merely simulates service life; however, it produced some deterioration and, when followed by vibration may produce realistic failure modes. Radiation shall be added to other known degrading influences where appropriate. Margins over that expected in the qualified life shall be provided in the application of each influence.
Electromechanical equipment (motors, relays, etc.) shall be operated to simulate the expected mechanical wear and electrical contact degradation (for example, contact pitting) of the device to be type tested.
An accelerated rate for the number of cycles equal to the required number during the design life may be utilized provided the rate shall not be accel-erated to any value which results in effects that would not be present at normal rates.
For insulating materials, a regression line (see IEEE-101-1972, Guide for Statistical Analysis of Thermal Life Test Data) may be used as a basis for selecting the aging time and temperature. Sample aging times of less than 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> shall not be permitted.
ADDENDUM TO FOREWORD CLARIFICATION STATEMENT TO /EEE STANDARD 323-1974Ul 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. 279u1971, Section 4.4. It is based on an awareness by members of IEEE Nuclear Poser Engineering Committee that the ability of Class 1E equipment to perform its safety functions might be affected by changes due to natural, operational, and environmental phenomena over time (aging).
It was not their intent that aging should be applied to all Class 1E equip-ment, but rather that aging must be considered in the same manner as
- 1. Addendum to Foreword. Clarifcation Statement. IEEE 323-1974 4-4
other environmental parameters. The need for aging of a particular equip-ment should be determined by an evaluation of its specific design and application. If aging is needed, a further determination must be made on whether accelerated aging techniques: 1) can be applied to the equipment, and 2) will yield valid results that may be correlated to real time, ongoing qualification.
The state of the art regarding aging is more advanced for some Class 1E equipment than for others. It is expected that known technology will be utilized in any aging program. Optionally, and especially where the state of the art is limiting, aging as part of the qualification program may be addressed by operating experience, analysis, or combined or ongoing quali-fication, as detailed in Sections 5.2, 5.3, 5.4 and 5.5.
Further clarification of aging as it applies to specific types of equipment will be provided in individual IEEE Class 1E equipment qualification docu-ments. For example, IEEE P-381 is bemg prepared to establish criteria for Class 1E modules. IEEE Standards 334, 382, and 383 provide guidance for motors, valve operators, and cables, respectively.
4.1.2 Comparison of Model B Tests with IEEE 323-1974 Requirements A step-by-step comparison of requirements with tests and analyses of the Model B recombiner follows:
The sequence of testing on the Model B recomniner followed the sequence given in para-graph 6.3.2 of the Standard. The sequence is justified since it represents the sequence of events which would take place if a hydrogen recombiner were required to perform after a Design Basis Accident (DBA).
1.
Inspection may be performed to assure that a test unit has not been damaged....
Since the test recombiner was made at the production facility, the normal inspection performed in all recombiners was completed. in addition, the unit was visually inspected by Westinghouse PWR-SD engineering personnel.
2.
Operation under normal conditions...
This was accomplished by energizing the unit and then performing an air flow and temperature distribution test. These tests are described in Sections 3.1 and 3.2 of this report.
3.
The equipment shall be operated to the extremes of performance and electrical characteristics...
This requirement was accomplished by operating the recombiner at higher than normal temperatures. The recombiner was operatec at 1320 F whereas normal test temperature is 1225 F. Further ' off-design" tests are reported in Step (7) of this program.
4-5
4.
Equipment shall be aged in accordance with Section 6.3.3 to put it in a condition which simulates its expected end-of-qualified life condition.
The components of the Model B Recombiner which require qualifi-cation are all located in the recombiner. (The power supply and control panel are the same as the Model A).
The following evaluation was made to determine how aging might affect the equipment life:
Recombiner The recombiner unit is composed primarily of metallic structural material, metal-enclosed thermal insulation, metal-clad ceramic insulated heater elements, and power cables.
The normal schedule of the recombiner calls for periodic testing to determine system availability plus periods of non-operating time in normal containment environment. Evaluation of these factors leads to the conclusion that the most significant aging factor was the fatigue life of the structure, due to thermal stresses induced by the period:c heat up and cool down tests. It was concluded that the metal structures and metal-enclosed thermal insulation would not be affected by time alone. The heater life for this type of heater element is far in excess of the duty cycles imposed by the periodic tests; however, the duty cycles were included in the aging program since they are a necessary part of the recombiner test. The power cables are subject to deterioration due to aging: they are covered by lEEE-383. " Standard for Type Test of Class lE Electric Cables, Field Splices and Connections for Nuclear Power Generating Stations" and have been qualified to this standard.
The aging test for the recombiner structure consists of 100 heatup and cooldown cycles as described in section 3-4. Estimating two full tempera-ture tests per year for an installed recombiner leads to a projection of more than 40 years of qualified life. Following the 100 cycle test, the unit was inspected for damage and was found to be in good operating condition. As previously noted, the heaters were also aged in this test.
5.
The aged equipment shall be subjected to mechanical vibration...
The recombiner was subjected to seismic tests as described in paragraph 3-5 of this report. OBE and DBE test levels, with the recombiner at operating temperature, were conducted using both biaxial random frequency and biaxial sine beat inputs. These tests demonstrate the seismic adequacy of the Model B recombiner.
4-6
l 6.
The aged equipment shall be operated while exposed to a simulated DBA...
To demonstrate that the recombiner will operate during and immediately after a DBA, steam pressure transients were performed on Model A recombiner heater banks, electrical cabling and internal electric heater connections. Since the Model A and Model B design of the applicable portions of these components is identical, the Model A test results as discussed in WCAP-7709L Supplement 3, Section 3.2 apply. The thermo-couple junction box wiring connections and electrical junction box wiring connections are the same for Model B as for Model A so this part of the Model A qualification applies. However, since the Model B junction boxes are now built into the recombiner rather than being separate units as in the Model A, the effect of the pressure transient in the box structure must be evaluated. This analysis is shown in Appendix B. Also, since the Model B recombiner heater frame is structurally different than the Model A, the effect of a pressure transient was recalculated using the same method as used on the Model A recombiner. The louvers were qualified in section 3-7 by testing with a spray environment.
7.
The equipment shall be operated while exposed to the simulated post-accident conditions.
A number of tests were performed on the Model A recombiner which are applicable to the Model B recombiner and additional tests were performed on the Model B recombiner. Model A tests which apply include all heater element and heater assembly tests. (High temperature, LOCA transient, long term post LOCA, external air pressure during containment leak tests, over voltage and irradiation as reported in WCAP's 7709L Supplement 2, 3, 4 and 5 and as summarized in Supplement 6.
Tests were run of the Model B recombiner to show that it will recombine hydrogen efficiently and that it will withstand the post-LOCA containment spray. These tests are described in this report.
The test and analyses described in this report show that the Model B recombiner complies with the applicable portions of IEEE 323-1974.
4-7
l APPENDIX A DESCRIPTION OF THE MODEL B ELECTRIC HYDROGEN RECOMBINER A-1.
DESCRIPTION The electric hydrogen recombiner is shown in figure A 1. A summary of typical design param-eters is presented in table A-1. The recombiner consists essentially of a thermally insulated vertical metal duct with metal-sheathed electric resistance heaters provided to heat a continuous flow of containment air (containing a low concentration of hydrogen) up to a temperature which is sufficient to cause a reaction between hydrogen and oxygen.
Air and its contained hydrogen enter the recombiner and flow up through the heated section and out the top by natural convection. The intake of the recombiner is located only on one side and the exhaust ports are located above and on the other three sides of the recombiner.
This arrangement of intake and exhaust ports serves to ensure that for downflow air currents external to the recombiner, there would be little tendency for recirculation of the recombiner process gases (from the exhaust back into the intake).
No circulation fans are required and the desired flow rate of air is established by providing the proper size inlet flow area through an orifice plate at the bottom of the recombiner.
Thus, with the air flow rate regulated by a fixed orifice and with the supply of electric power determined by a control station outside the containment, controls are not needed in-side the containment. Heat added to the containment air by the recombiner is removed by containment cooling systems already available for other much larger heat loads so that the containment air temperature will remain essentially unaffected by the recombiner.
The electric hydrogen recombiner uses conventional type electric resistance heaters sheathed with incoloy-800, which is an excellent corrosion-resistant material for this service. These heaters, which are shown in figure A-2, have been designed to operate with the same sheath temperatures as commercial heaters, but at power densities much Ic.wer than normal. Each bank contains 60 individual heating elements. Operation of the unit is virtually unaffected if a few individual heating elements fail to function properly.
The major structural components are manufactured primarily of 300-Series stainless steel.
Incoloy-800 is used for the heater sheaths and for other parts such as the heater duct, which operates at high temperature.
A-1
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TABLE A-1 ELECTRIC HYDROGEN RECOMBINER MODEL B TYPICAL PARAMETERS Power (Maximum) 75 kW Power (Nominal) 50 kW Capacity (Minimum) At I atmosphere 100 scfm Heaters Number 4
Maximum Heat F.ux 7.9 watts /in.2 0
Maximum Sheath Temperature 1550 F Gas Temperature Inlet 80 to 155 F In Heater Section 1150 to 1400 F i
Exhaust 0
~50 F above Ambient Materials Outer Structure 300-Series S.S.
Inner Structure incoloy-800 Heater Element Sheath Incoloy-800 Dimensions Height 8 f t.
Width 3.9 f t.
Depth 4.6 f t.
Weight 4500lb.
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Electric Hydrogen Recombiner, Typical Heater A-4
A-2.
DESIGN CRITERIA The following are criteria considered in the design of the electric hydrogen recombiner for pressurized water reactor containments:
a The recombiners are designed to sustain all normal loads and accident loads, includ-ing seismic loads and temperature and pressure transients from a loss-of-coolant accident.
The recombiners must be protected from damage from high-energy missiles or jet e
impingement from broken pipes.
The recombiners must be located in the containment such that they process a flow e
of containment air containing hydrogen at a concentration which is approximately typical of the average concentration throughout the containment.
e The recombiners must be located away from high-velocity air streams, st.ch as could emanate from fan cooler exhaust ports, or they must be protected from direct impingement of high-velocity air streams by suitable barriers such as walls or floors.
The recombiners are designed for a lifetime consistent with that of the reactor plant.
e All materials used in the recombiners are selected to be compatible with the environ-m mental conditions inside the reactor containment during normal operation or during accident conditions.
A-5
i APPENDIX B ANALYSIS OF TRANSIENT PRESSURE LOADS The purpose of this analysis is to verify the structural adequacy under LOCAL containment pressure transient loads of the heater frame, thermocouple junction box, and electrical junction box for the Model B Recombiner. The same calculational technique as developed for the Model A heater frame and reported in WCAP-7709L Supplement 2lll will be used. The ca-pacity to withstand a 10 psi per second pressure transient will be analyzed and this will be the design basis for the Model B Recombiner. (Same as Model A)
The recoi biner is basically an open structure and only small differential pressures are devel-oped during a pressure transient. The heater frame, electrical junction box, and thermocouple boxes, although well-vented to prevent differential pressure, are the most restrictive compo-nents and have been analyzed.
The analysis is presented in two parts: (1) The determination of the pressure acting across the component; and (2) the determination of the stresses in the component resulting from these pressures. The analysis for the heater frame it presented in detail and the results for the same analysis applied to the two junction boxes is summarized.
B 1.
PRESSURE LOADING AND ANALYSIS Thc heater duct and frame has a volume of about 27.6 ft3 and an inlet area of 0.562 ft3 The external pressure across the walls will be conservatively calculated as follows: Assume that the pressure inside the volume follows the external pressure, i.e., the containment pressure, with no time lag. Determine the mass flow rate into the chamber to keep the internal pres-sure equal to the external pressure. Determine the pressure drop across the inlet area required to develop this mass flow rate.
The nomenclature for the calculations is as follows:
A = Flow area into volume gc = gr vitational constant hl = Head loss at inlet area 1
Wilson. J. F. " Electric Hydrogen Recombiner for PWR Containments. Equipment ouahfication Report." WCAP 7709L.
Supplement 2, September 1973.
B-1
K = Pressure loss coefficient at inlet rIn = Mass flow rate into volume Q = Volumetric flow into volume R = Gas constant T = Air temperature t = Time V = Heater duct and frame assembly volume v = Velocity through inlet area Ap* = Pressure drop across inlet area Ap
- = External pressure rise rate At p = Density of air b,c J
B-2
b,c 3
2 For the case of the heater duct and frame assembly, where V = 27.6 ft, and A = 0.562 ft ;
the differential pressure calculated by this conservative method would be 0.015 psi, which is small as expected.
B 2.
STRESS ANALYSIS The heater duct and frame assembly is a box structure with 0.156-inch-thick Incoloy sheet metal sides. The stresses in the box will be conservatively calculated by analyzing a strip of unit width with simply supported ends subjected to a lateral loading of Ap* and an end load, P. The maximum stress in the strip is given by the formulaIll.
1.
Roark, R. J. "Formular for Stress and Strain," 4th edition, New Wrk, McGraw-Hill,1965.
B-3
b.c I
e S = 363 psi B4
This stress is much less than the material yield strength under blowdown conditions and is, therefore, acceptable A similar analysis, when applied to the thermocouple junction box and electrical junction box, show them to be acceptable based on low stress during the pressure transient.
B5