ML20004B205
| ML20004B205 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/18/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8105270391 | |
| Download: ML20004B205 (23) | |
Text
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TENNESSEE VALLEY AUTHORITY
.p CH ATT A NOOG A, T ENNESSEE 3Not 400 Chestnut Street Tower II j \\ P l m&
May 18, 1981 I
U$ [,'.J.E.~Tp(5 os Mr. Robert L. Tedesco f._
^
Ej MAY 26198l
- 9' Ass 10 tant Director for Liesusing 4
Division of Licensing i
% s.Nucu n u n c ou 7
U.S. Nuclear Regulatory Comission (g
p
- "55*
Washington, DC 20555 N
,j s
\\Y/
Dear Mr. Tedesco:
fG In the Hatter of the Application of
)
Docket No. 50-328 Tennesese Valley Authority
)
In res',.onse to your letter of May 1,1981 regarding TVA's core degradation program, we are pleased to provide the following information:
1.
We have revised and updated the sections in our second quarterly report which describe the Electric Power Research Institute's (EPRI) hydrogen research program. These revised sections are included as Enclosure 1 to this letter. In the revised sections, we have included all the available information about each subproject of the EPRI program (its purpose, description, and status) so that referencing of earlier quarterly reports or studies will not be necessary. We believe that the revised program description addresses the majority of the comments contained in the draft report which you forwarded in your May 1,1981 letter.
2.
Tho:.9 coments which were not addressed by the revised EPHI program des a'iption are specifically addressed in Enclosure 2.
TVA, Duke Power, and American Electric Power discussed each of these coments personally with your staff in our meeting in Bethesda, Maryland, on May 6, 1981.
3 In your letter, you requested that we address those specific issues identified during the recent hearings on the McGuire docket. We believe that Enclosurc 1 to this letter in combination with our responses to your letter of April 14, 1981 adequately covers those issues.
4.
In regard to the four items you specifically addressed in the last paragraph of your May 1,1981 letter, the following s rmarizes our comitments.
Item 1 - The containment usponse during a spectrum of degraded core accident scenarios through the recovery period TVA will provide a CLASIX analysis which addressec this item in our October 1981 submittal on the Permanent Hydrogen Hitigation System (PHMS).
An Equal Opportunity Erantoyer 8105 270 39 l
=s 2-Directoi of Nuclear Reactor Regulation May 18, 1981 Item 2 - The potential for and consequences of inadvertent inerting of the lower compartment TVA has addressed this item in response to question number 1 of your April 14, 1981 letter Item 3 - The potential for and consequences of transitions to detonation to ooour in the upper plenum of the ice condenar TVA has addressed this item in response to question number 3 of your April 14, 1981 letter Item 4 - Thermal response of and any need ')r hardening of essential equipment to assure these pieces of equipment will survive the consequences of buming hydrogen gas This item is currently under investigation. TVA will be prepared to respond to this issue by May 31, 1981, in conjunction with the other equip:nent survivability issues outlined in Supplement No. 4 to the Sequoyah Safety Evaluation Report (NUREG-0011).
Very truly yours, TENNESSEE VALLEY AUTHORITY
/
L. M. Mills, Ma ger Nuclear Regulation and Safety Suorn to subsor before me this_/
' day of I
/ 1981 M
ft wMr hotafPublio
//
.3 My Commission Expires s
/ /
Enclosures
. _ _ _.. -. - -. - ~. -...
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j ENCLOSURE 1 i
SEQUOYAH NUCLEAR PLANT i
I i
REVISIONS TO SECTION B AND APPENDIX A.1 j
0F THE TVA SECOND QUARTERLY REPORT ON THE HYDROGEN RESEARCH PROGRAM 1
i i
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B.
Electric Power Research Institute (EPRI)/TVA/ Duke /AEP B.1 Scope The scope of the four EPRI research programs remains unchanged.
However, to facilitate the review of the program, we have in this special revision to the second quarterly report, at the request of the NRC, consolidated the information we have about each project, its scope, description, and current status. We have included this latest information, including new sketches showing proposed test configurations for some tests, in the revised Appendix A.1.
The EPRI research program is currently at a stage where test matrices are being finalized and tests are commencing. We expect to have further information available and wiu include this information in TVA's third quarterly report which is currently scheduled to be submitted June 16, 1981.
B.2 Schedule EPRI has recently issued a revised schedule which includes the latest progress and changes for all four of the EPRI tests. The revised schedule is shown in Figure II.B-1.
The most significant change involves shifting the Hanford tests from the May through September test window to the July through November timeframe. The Hanford tests have been delayed due to unexpected difficulties in the contract negotiations between EPRI and the U.S. Department of Energy. An agreement and the formal signing of a contract is imminent.
B.3 Status The revised Appendix A.1 includes the latest status for each of the four projects.
4
HYDR 0 GEN COMBUSTION AND MANAGEMENT PROGRAM
- FIGURE II-B.1 SCALE
~
3 3
1982 (10 FT )
11/1 1/1 3/1 5/1 7/1 9/1 11/1
.1/1 0.001.>'
IGNITER DEVELOPMENT (WHITESHELL/.
)
0.6 HYDROGEN CONTROL STUDIES (ACUREX) 0.2 HYDROGEN COMBUSTION STUDIES (AECL, WHITESHELL) 30 HYDROGEN MIXING STUDIES (HEDL-W)
- II/81 i
i
2 i
APPENDIX A.1 EPRI PROGRAM - TECHNICAL DETAILS 1.0 Introduction In order to design and install a permanent hydrogen mitigation system at Sequoyah Nuclear Plant, several questicns concerning hydrogen
=anagement should be addressed. TVA, American Electric Power (AEP),
and Duke Power hava entered into a research effort with the Electric Power Research Institute (EPRI) to study hydrogen mitigation and control under degraded core accident conditions. The following is a description and status of that program to date.
1.1 Objectives and Technical Issues This program is intended to meet the following limited objectives:
1.
Determination of whether and when hydrogen can burn in postulated ice condenser accident environments resulting frem degraded core scenarios; 2.
Demonstration that if a hydrogen burn does occur, its effects will not exceed the realistic survival capabilities of equipment and containment; and 3.
Demonstration that reasonable control methods can provide adequate safety margins assuring the integrity of the containment and of key safety-related equipment.
Dett mination of the effects of hydrogen deflagrations on containment and equipment requires investigation of several questions, in particular:
4 a.
What are the lower flammability limits under degraded core accident conditions and how effective are thermal ignition sources; b.
What is the character of deflagrations in various geometries and how can the offects be mitigated; c.
What is the nature of hydrogen mixing and distribution in large compartmentalized volumes; and d.
What is the potential for the accelerstion of deflagrations, or for flame propagation between compartments in turbulent mixtures.
5
3 1.2 Program Elements We believe the following projects will provide the information needed to satist'/ the program Objectives. The projects are related. and consist of:
1.
Development and preliminary testing of thermal igniters for a deliberate ignition system (AECL Whit 4shell);
2.
Experiments and analyses on basic hydrogen combustion phenomena including the effects of steam, turbulence, and flame propagation between compartments (AECL Whiteshell);
3 Experiments on hydrogen control methods including water spray and fog (Acurex/7actory Mutual);
4.
Measurement and analyses of hydrogen mixing and distribution in a large compartmentalized volume (HEDL-W ).
Figure 1 shows ti*a scales for the projects, including the test phase (solid line).
2.0 Description of the Prcgram Elements The four projects listed above will be accomplished at four facilities
( AECL Whiteshell, Acurex, Factory Mutual, and Hanford Engineering and Development Laboratory). The following is a description of each of the four projects and the facilities they will use to meet their program objectives.
2.1 Tgniter Development ( AECL Whiteshell)
The interim distributed ignition system which TVA installed in September of 1980 in Sequoyah Nuclear Plant employs a diesel engine glow plug. The ability of this glow plug to ignite hydrogen at low concentrations under various environmental conditions of steam, pressure, humidity, water spray, and airflow across the igniter surface was demonstrated during the Fenwal test. The current EPRI program is designed to compare four thermal igniter types, including the glow plugs, for effectiveness under an expanded range of environmental conditions and to compile data for comparison with the larger body of existing hydrogen combustion data.
This program will be accomplished at AECL Whiteshell in a 0.6 ft3 vessel which is approximately 12 inches high by 14 inches in diameter. Four types of thermal igniters will be subjected to identical test conditions. The igniters will be 4
p.....
y evaluated for their ability to ignite hydrogen in the range of 5 to 12 volume percent under various steam concentrations in the range of 0 to approximately 60 percent.
.te tsst will be conducted both with and without fan-induced turbulence. The vessel will be instrumented with fast response thermocouples (10 microseconds) and pressure transducers (1 microsecond) tied into a computerized data acquisition system.
Current Status The vessel has been instrumented and is currently undergoing shakedown tests. The testing program should begin within the next two weeks.
2.2 Hydrogen Combustion (AECL Whiteshell)
The objectives of these tests are:
1.
To provide fundamental understanding of H2 combustion; 2.
To escablish comparison between glow plus data and spark ignition data; 3
To study the effects of turbulence created by obstacles; and 4.
To stuly the flame propagation between different concentrations of hydrogen.
In order to accomplish these objectives, the tests will be conducted in an S-foot diameter, 220 cubic-foot sphere, and when necessary a connected 12-inch (id) pipe. The sphere nas a design pressure of 1450 lbs/in2 Both the sphere and the pipe are trace heated and insulated. The vessel will be instrumented with fast response thermocouples (10 microseconds) and pressure transducers (1 microsecond) as well as ion probes from which flame speeds can be determined. This vessel, like the smaller vessel discussed in 2.1 above, will emnloy a computerized data acquisition system. The vessel will also be equipped with two fans, the details of which are noted on Table 3, and provisions for gas sampling both before and after each testing using gas chromatography.
The tests have been divided into four parts to study:
1.
The lower flammability limits in steam, 2.
Laminar spherical deflagrations, 3.
The effects of turbulence on deflagrations, and 4.
Propagation of deflagrations between connected voleres.
4
5 Current Status The 220 cubic-foot sphere has been instrumented and is currently undergoing shakedown tests. Both these combustien tests and the igniter development tests are ceing conducted in parallel at Whitesnell. This particular testing pec3 ram is expected to begin collecting test data in approximately one week.
The following is a description of each of these parts of the program. A test matrix which summarizes these tests is presented as Tables 1 through 4 2.2.1 Lower Flammability Limit and Extent of Reaction At concentrations below 10-percent H, the combustion 2
reaction may not be complete. These experiments are designed to determine whether size and shape of the vessel affects the extent of reaction by comparing the results uith those obtained previously at Whiteshell in a small cylindrical vessel.
In these experiments, uniform hydrogen / air / steam mixtures will be spark-ignited at the bottom of the spherical vessel. By analyzing the mixture before and after the experiment, using gas chromatography, the extent of reaction will be determiced. Transient pressure and temperature measurements will be made and ionization probes will be used to detect flame speeds. The flammability limits and extent of reaction depend on the location of the ignition source, and some experiments will be performed with central and top ignition which are known to be less effective in producing a reaction.
2.2.2 Laminar Scherical Deflagrations At hydrogen concentrations greater than 10 percent, complete combustion is expected. Burning rates are important for determining the effects of high flame speeds and for estimating the time during combustion that heat trans.'er can occur. A correlation for laminar burning velocity as a function of hydrogen concentration and temperature has already been developed at Whiteshell Lased upon their bench scale experiments. This correlation allows a prediction of the pressure transient resulting from a laminar deflagration, and it is the intent of thes '
experiments to validate those calculations.
Central ignition of uniform hydrogen / sir / steam mixtures in the 8-foot sphere will be performed for hydrogen concentrations in the range of 10 to 42 percent. Maximum burning velocities and the fastest deflagration transients are expected at 42-percent hydrogen. High speed pressure and te=perature transducers will record the transients and ionization probes will detect flame arrival.
i 6
2.2 3 Effeeg,of Turbulence and Structures on Spherical Deflaggn.ons Since tutuulence can r.ignificantly accelerate the combustion rate,.these experiments are proposed to examine this effect. Turbulence in containments may be caused by convection currents from the ventilation fans and by obstacles (such as pipes, grids, etc.).
The proposed experiments would utill:e:
(1) a fan to produce convection flows before controlled ig7ition of uniform hydrogen / air / mixtures; and (2) obstacles to determine their effect. The obstacles to be used for these tests would consist of 1/4-inch perforated plates placed horizontally at two different elevations within the sphere. The perforations in the plate are one inch in diameter and are spaced equally over the surface of the plate leaving approximately 50 percent of the area of the plate open to ficw. The elevations of the two plates will be appioximately 2.6 feet and 5.3 feet from the bottom of
'he vessel. The experiments uill be performed in a manner similar to those described previously.
2.2.4 _The Sphere and Connected Pipe The Whiteshell high pressure sphere and pipe will be combined to study propagation of deflagrations between connected volumes. Unaqual concentrations of hydrogen in different volumes vill be ignited in one of the volumes and the propagation of the flame front and pressure wave will be measured. The pipe is 20 feet long by 1 foot in diameter.
2.3 Hydrogen Control Studies ( Acurex/ Factory Mutual)
The purpose of thess tests is to study the effect of spraye and fogs on hydrogen deflagrations. This will be accomplished by studying the interrelationship between wet water droplet size, water concentration, and hydrogen concentrations in small scale tests at Factory Mutual. Based on the data obtained from Factory
!!utual, large scale tests will be conducted by Acurex to study the pressure suppressant effects of sprays and fogs on hydrogen l
de flagrations.
2.3.1 Factory Mutual Studies A schematic of the experimental apparatus to be used is shown in Figure 2.
The test vessel is a Plexiglass tube approximately 3-1/2 feet long with a 6-inch inside diameter. The ignition source will be a spark igniter.
Ionization probes will verify the prc3ence of a flame during an ignition attempt. Thermocouples will measure the test vessel's atmosphere temperature.
4
7 Th] current tt t matrix will provida dtta for drop)Gt sizes in the range of 10-400 microns and water concentrations varyits from 0-5 volume percent. The hydrogen concentration will be varied from 4-12 volume percent. These tests will provide information on conditions that produce inerting. From this data, spray droplet sizes with potential to reduce the maximum pressure. from controlled burning will be selected for further study at the Acarex test facility.
Curent Status Factory Mutual is currently performing droplet characterization studies and facility checkout tests.
Testing will begin June 18, 1981 and is expected to be complete on or around July 8, 1981. Factory Mutual expects to complete their final report by August 6, 1981.
2.3.2 Acurex Studies Figure 3 provides a flow diagram of the facility to be used. Vessel instrumentation is shown in Figure 4 The vessel is approximately 17 feet high with a 7-foot inside diameter. The volume is 630 cubic feet. Instrumentation includes pressure transducers, Type K thermocouples, and ionization probes. Ignition will be by spark and glow plugs. This will allow correlations to be made between the Factory Mutual studies and postulated conditions inside containment.
Although the exact test conditions will not be determined until the Factory Mutual studies are well underway, the range of parameter values will be within those specifie4 in section 2.3.1.
These tests will provide information on the pressure suppressant effects of foss/ sprays on hydrogen deflagration. From this information, the relative merits of incorporating fogs / sprays into a hydrogen mitigation system can be evaluated.
. Current Status The Acurex test vessel has been instrumented. The vessel, however, has not been delivered to the test site. Acurex ex;octs to move the vessel and begin shakedown tests by June 1, 1981. Testing will begir by approximately June 15 and be completed on or around July 20, 1981. Acurex expects to complete their final report by September 14, 1981.
4
8 2.4 Hydrogen Mixing and Distribution Studies (Hanford)
The purpose of these tests is to quantify the degree of hydrogen mixing in a simulated ice condenser geometry under accident conditions.
Compartments will be built in the 30,000 cubic-foot containment system test facil; to simulate a simplified ice condenser containment geometry (see figures 5 and 6). The tests will then be performed with scaled hydrogen and steam flows based on average release rates obtained from the MARCH computer code.
Hydrogen concentrations and temperatures at various spatial locations will be measured as a function of time. Other measurements to be taken include water / vapor concentrations, and convective gas flow patterns in a few key locations. Testing will be restricted by safety regulations to use of only 4 volume percent hydrogen since the vessel is located in a building which houses other experiments.
Identical tests will be run with both helium and hydcogen, and a correlation between the two will be obtained to allow the majority of tests to be run with helium.
Status Hanford has not as yet finalized their test matrix. Currently, they have been concentrating on selecting appropriate scaling factors and test geometry. The test vessel will be available starting July 7,1981, and testing is expected to begin by August 7,1981.
4
TABLE 1 Test Matrix for Whiteshell Experiments i
1.
Extent of Reaction of Lean Mixtures Exp. #
%H NN 0 Ignitien 2
2 1-3 5.0 0
bottom 4,5 6.5 0
bottom 6
8.0 0
bottom 7-9 5.0 15 bottom 10,11 6.5 15 bottom 12 8.0 15 bottom 13,14 6.5 30 bottom 1
8.0 30 bottom 16 6.5 0
center 17 6.5 15 center 18 8.5 0
top 19 8.5 30 top Note: Steam concentrations are in the process of being revised upward to address current NRC concerns.
4 4
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TABLE 2 2.
Lami. par Spherical Deflagrations
.Exp. #
5H
%H O Ignition 2
2 1
10 0
center 2
20 0
center 3
30 0
center 4
42 0
center 5
to 10 center 6
20 10 center 7
30 10 center 8
42 10 center 9
10 20 center 10 20 20 center
?1 30 20 center 12 42 20 center 13 10 30 center 14 20 30 center 15 30 30 center 16 42 30 center 17 14 0
bottom 18 20 0
bottom Note: Steam concentrations are in the process of being revised upward to address current NRC concerns.
4
TABLE 3 3
Effect of Fans and Obstacles Ex. #
%H JH O Fan Speed Orating Ignition 2
2 1
6 0
50%
No bottom 2
6 0
100%
No bottom 3
7 0
100%
No bottom I
4 6
0 0
Yes bottom 5
7 0
0 Yes bottom 6
7 0
100%
Yes bottom 7
14 0
100%
No center 8
20 0
100%
No center 9
14 0
0 Yes center 10 20 0
0 Yes center Fan Particulars Grating Particulars blade tip diameter:
16 in.
type:
1/4" perforated plate air deflectors hole size:
1: dia.
max. speed
- 1800 rpm
-blocked area: 50%
max. flow rate
- 1500 ofm spacing: 2 plates placed (sphere vol = 220 ft#3$)
horizontally at 1/3 points No. of fann
- 2 centinuously variable speed i
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'A TABLE 4 4.
Sphere and Protruding Pipe Exp. #
$H
%H O Ignition 2
2 1
8 0
sphere-center 2
20 0
sphere-center 3
8 0
pipe-end j
4 20 0
pipe-end i
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5 8p/6s O
pipe-center i
j 6
10p/6s O
pipe-center i
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SEQUOYAH NUCLEAR PL*NT !
RESPONSE TO DR. STREELOW'b COlICERNS TVA's revised description of the EPRI research prohram is contained in.
We believe that this revised program (will answer many of the comments contained in Dr. Strehlow's draft report. ; Dr. Strehlow's concerns are addressed individually as follows.
Item 1 - Please refer to the revised Appendix A.1, Section 2.2.
Item 2 - The tests described in revised Appendix A.1,: Sections 2.2.1 and 2.2.2 are the control runs for this vessel.
Item 3 - Our nomenclature was misleading. The purpose of these tests is to study the effects of turbulence caused by fans and grids. We believe that the results of these tests can be generalised. TVA has modified the description of these tests in Appendix A.1, Section 2.2.3, to clarify their p,urpose.
Item 4 - We have revised our description in Appendix A.1, Section 2.2.4, to provice additivnal information. However, Dr. Strehlow's concern about the diaphragm requires further consideration. We have referred the comment to our consultants at Whiteshell for resolution.
Item 5 - The igniter development program is a continuation of the confirmatory testing of glcw plug-type devices at Fenwal.
In addition, this testing will be used to draw comparisons between glow plug effectiveness at lower fla=mability limits in the presence of steam 7.r4 similar testa using a spark igniter.
Concerning Dr. Strehlow's comment on our schedule, we would respond by noting that it is necessary for us to plan our final design based cn preliminarf results.
Item 6 - Please refer to revised Appendix A.1, Section 2.2.
Item 7 - Please refer to revised Appendix A.1, Section 2 3 Item 8 - Please refer to revised Appendix A.1, Section 2.4.
Item 9 - The Atlantic Research draft report is complete, but we have not received their final report which incorporates our comments.
However, based on the draft report we have perfoemed some cor-rosion tests with Halon decomposition products at TVA's Singletca Laboratories. Preliminary results of these testa indicate that the decomposition products are too highly corrosive to allow us to cansider Halon as our Permanent Hydrogen Mitigation System. TVA will provide further in?ormation in our next quarterly report.
4
Item 10 - TVA has discontinued the EMI studics and dropped spark igniters from further consideration.
Item 11 - No coment necessary.
Item 12 - We are awaiting t,he first draft of-the catalytic combustor final report.
Item 13 - We agree with De, Strehlow's comment, and we are proceeding to develop an appropriate ' test scheme at TVA's Singleton Lcboratories.
Item 14 - No coment necessary.
Regarding the " Summary of Research Needs" provided by Dr. Strehlow, these issues have been addressed by TVA in the text of this letter and its enclosures.
i 4
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