ML19345D437
| ML19345D437 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/15/1980 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19345D436 | List: |
| References | |
| NUDOCS 8012150108 | |
| Download: ML19345D437 (127) | |
Text
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E::CLCSUR.E 1 TE'iNESSEE VALLEY AUTHCRITY SEOUOYAH NUCLEAR PLANT RESEARCH PROGRAM ON hTDROGEN COMBUSTION AND CONTROL QUARTERLY PROGRESS REPORT DECEMBER 15, 1980 i
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\ a, 301g150 1
f TABLE OF CONTENTS I. Introduction II. Task Description, Schedule, and Status A. Atomic Industrial Forum (AIF)/TVA
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B. Electric Power Research Institute (EPRI)/TVA/ Duke /AEP C. Westinghouse /TVA/ Duke /AEP i
C.1 Fenwal, Incorporated l C.2 CLASIX Modifications D. TVA/ Duke /AEP D.1 Halon (Atlantic Research Corporation)
D.2 Electremagnetic Interference Study D.3 Catalytic Combustor .
D.4 Fogging TVA 8.1 Browns Ferry Probabilistic Risk Assessment (Pickard, Lowe, and Garrick)
E.2 Sequoyah Full-Scale Safety and Availability Analysis (Kaman Sciences Corporation)
E.3 Consequence Analysis E.4 Singleton Testing E.5 Severe Accident Sequence Analysis (SASA)/(ORNL)
E.6 Ice Condenser Contairiment Code
III. Appendices A. Program Details A.1 AIF Program A.2 EPRI Program A.3 Halen Study A.4 Consequence Analysis A.5 Singleton Testing B. Equipment Survivability C. Comparison of Postaccident Inerting Agents 6
E50337.01
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I. Introduction This report is the first of a series of quarterly research summaries presented to the Nuclear Regulatory Commission (NRC) by the Tennessee Valley '"*hority (TVA) to satisfy the following condition of the Sequoyah Nuclear Plant unit 1 operating license:
During the interim period of operation, TVA shall continue a research program on hydrogen control measures and the effects of hydrogen burns on safety functions and shall submit to the NRC quarterly reports on that research program. .
TVA is pleased to document the various facets of its current degraded core research program in this report and is confident that all possible efforts have been exerted to ensure the timeliness, effectiveness, and completeness of the program.
Increased attention was devoted to accidents beyond the design basis in ear.y 1980 as TVA, with the aid of Westinghouse and three architect-engineering firms, produced a report that has sinca been submitted to the NRC on September 2, 1980, as Volume I l
l of the Sequoyah Nuclear Plar.t Degraded Core Program Report. TVA t
l has remained in the forefront of L1dustry efforts in many areas of degraded core research and development. This leadership was
, demonstrated by the decisior. to valuntarily implement the interim l
l distributed ignition system at Sequoyah to extend the plant's l
l capability for hydrogen control. IVA has continued to 1
voluntarily conduct its own degreded core programs and to cooperatively participate with other utility groups in these research efforts. These efforts are the subject of the present report. The format is designed to present in Section II a summary of the secpe, schedule, and status of each task with further technical details in appropriate appendices.
In addition, a summary of the TVA position on equipment survivability for hydrogen burning during degraded core events is presented in Appencix B. TVA firmly believes that the equipment survivability issue is generic and not limited to ice co.idenser containments. If anything, the equipment within an ice condenser containment could withstand a hydrogen burn better than in a dry containment due to the heat removal potential inherent in the ice bed and structural heat sinks. Appendix B includes a list of key equipment inside the Sequoyah containment, estimates of environmental conditions resulting from hydrogen combustica, and an evaluation of their. effects on such equipment.
j A brief discussien of studies to scope the potential of carbon I dioxide as a postaccident inerting a3ent is presenteo in Appendix l
C.
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II. Task Description, Schedule 1 Status The major emphasis of TVA's current research program is to discover, collect, and evaluate enough information about degreded core events and potential mitigations for their risk reduction to be able to select, design, and install a permanent hydrogen centrol system for Sequoyah Nuclear Plant. This per=anent system would satisfy the following condition of the unit 1 operating license:
For operation of the facility beyond January 3- 1982, the Commission must confirm that an adequate hydrogen control system for the plant is installed and will perform its intended function in a manner that provides adequate safety margins.
A list of the most impo.* tant topics where further information is needed is shown in Table 1. Another list showing both TVA's current major tasks and its outside consultants and resources is presented in Table 2. Figure
- shows a schedule of activities necessary to meet the unit 1 licensing conditions.
This section provides a summary of each individual or group l
effort in whien TVA is actively involved that is related to hydroger. ecmbustion and control, risk assessment, or overall degraded core studies. Her'. the current scope, schedule, and status of each effort ic summarized with further details
! presented in the appendices. Nate that certain related risk l
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assessment studies for the Browns Ferry Nuclear Plant are also described, since experience with these techniques will be useful in Sequoyah risk studies.
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i Table 1 Information Needed to Decide on Final Mitigation
- 1. Halen feasibility study completed. Conceptual design and preliminary safety evaluation done, if feasibility study is positive.
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- 2. Catalytic combustor feasibility study completed. Preliminary design anc safety evaluaticn done, if feasibility study is positive.
3 New igniter fevelopment program completed.
4 Study on electromagnetic interference (EMI) effects of spark J
ignicars completed.
i i 5. Evaluation of additional potential =itigations such as spray f fogging and postaccident inerting ec:pleted.
- 6. Best possible decision on design basis accident scenario (s) made.
- 7. Preliminary MARCH runs ( impleted inhouse en Sequoyah model.
l S. Time-dependens hydrogen source term reasonably assured.
9 CLnSIX modifications cene. New pinac specific cases run, if r
necessary.
- 10. Reasonable assurance that any potential hazards from operaticn or misoperation of the final system are understood.
- 11. Estimate true risk reduction '.enefit of final =itigation.
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I Table 2 J
Major Tasks and Outside Consultants / Resources 1
Major Tasks Outside Consultants / Resources Risk assessment Kaman Sciences Corporation Pickard, Lowe, and Garrick Consequence analysis Batelle, Columbus Laboratory Oak Ridge National Laboratory i
Containment response Westinghouse Offshore Power Systems State-of-technology research Atomic Industrial Forum and rulemaking Igniter develapment EPRI (Rockwell-Rocketdyne) l l Combustion research EPRI (AECL-Whiteshell)
Hycrogen centrol (Halon, E?E: (Acurex)
I fogging)
Hydrogen mixing and EPRI (Hanford Engineering
distribution Develop =ent Laboratory)
Igniter combustion tests Fenwal Halon development Atlantic Research Corporation Spark igniter develop =ent Keiser Engineering (electromagnetic interference) e 1
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'Me _
--e
r vy80
' Si.udy varicus nitigation cencepts
~~ (Volune 1 of Hydrogen Study) nr. ,,, g0 __
.ty'80 Jun'8C . -.. A Interir. Distributed If,n .tien d Systen (IDIS)
Jul'80 designed and installed in SQN-1.
Aug'So .
Document IDIS and safety evaluation Sep'80 *---- 3 (Volune 2 of Hydrogen Study)
Cct'80 Nov'80 rec'80 = C1 __
Jan'81 refine projects and .:ecure censultants to study
- D 2
degraded core behavier, containnent response, Feb'31 and selected mitigatien nethods.
Mar'81 .e--- C2 l Apr'81 May'81
.. a E __
Jun'81 C3 Design final system Jul'81 Procurenent
' Aug'81 Sep'81 ~ C'4 Construction, installation and t
-- preeperational esting.
Oct'81 (partially cutage dependent)
^
Final safety evaluation NOV'01
"- report.
ec'81 --- C 5 __
Jan'82
- m F -
Legend:
A: T7A regraded Core Task Force established 3: SQN Full pcwer licen::e awarded C: NRC quarterly reports due D: Firct Licensing c.cndition cleared
.:: Decision for fina. fix F: All licensing conditions cleared i
Figure 1
i A. Atomic Iadustrial Forum (AIF) Proposal A.1 Scope The scope propown includes the following 15 tasks:
- 1. Safety Goal / Criteria Application
- a. Generate position paper on the role of safety goal / criteria in the degraded core rulemaking activities
- b. Generate comprehensive criteria for methods for evaluation of degraded core conditions
- 2. Selection of Dominant Sequences
- a. Initial definition of "likely" dominant sequences based on available material, an initial ranking of sequences in terms of i
l probability and consequences anc' a definition or currently available preventive and mitigative (e.g., containment heat removal) systems D. Quantify the dominant sequences defined in "ad, identify any other sequences that should be considered, provide preliminary I
consequence assessments, and document the process and rationale for selection of dominant sequences
- c. Update to include detailed study results such as the ones for Zicn-Indian Point, NSAC/ Duke, Limerick, TVA, etc.
3 Identification of Phenomenological and Con',ainment Transient Critical Sequences General containment phenomenolog. :al event trees (or equivalent) for.the major reactor systems.
- 4. Steam Overpressure 'rhenomena (In-Vessel, Containment)
Pr vide sound phanomenolog; cal models for:
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- a. The progression of core melt for the identified dominant sequences
- b. The conditions necessary for occurrence of steam explosions and effects of resultant explosions
- c. Mixing dynamics of core debris-water interactions
- d. Steam generation rates far core debris-water interactions and the dynamic effects of large scale cora debris-water interactions en the materials involved given typical reactor plant geometries.
- 5. Hyorogen Generation and Burn Provide sound phenomenological models for the l
generation, distribution, iginition, and combustion of hydrogen
- 6. Lydregen Burn control
- a. Survey of hydrogen detectors
- b. Evaluation of preinerting for containments
not already evaluated
- c. Evaluation of fogging / spray suppression
- 7. Equipment Survivability for the Degraded Core Environment For five plant configurations (Bh3, each NSSS 1
vendor Ph3, and ice condenser)
- a. Identify the minimum set of functions which must be performed or equipment which must not operate as a consequence of the environment to permit termination of core degradation sequences or.to monitor the status of the plant and retain containment.
- t. Based on "a," identify necessary minimum set of generic equipment.
- c. Identify environments associatec with the dominant sequences.
- d. Evaluate ths survivability of the equipment in "b" for the concitions in "c" and define tests, if necessary.
- e. Develop recommendations on equipment
survivability criteria and document results of complete task.
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- 8. Core Debris Coolability
?rovide technically sound, phenomenological models for the progression of postulated core melt for the dominant centainment s-quence events.
- 9. Containment structu tl capability
- a. Schedule a seminar of utilities and associated consultants who have performed realistic analyses of containment capability to identify what has been done, what residual work may remain, and what criteria should be proposed i
by the industry for these evaluations.
I b. Define the inertial loadings which may be encountered (from Tasks 6 and 15) and specify the program of analysia of containment inertial load capability for performance.
- 10. Evaluation of Liquid ?&thway Dose Integrate available informatior. and provide
- scoping information on the feasibility time span i
and cost of source interdiction.
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- 11. Fission Product Liberation and Removal EPRI and DOE are pursuing the development of a program to improve the models currently used to estimate the amount of =aterial liberated and the i depletion of this material prior to reaching the population. The intent is to integrate the results of that program into the development of
, the industry positions en degraded core.
- 12. Vented Containment Systems Define the range of applicability of vented containment systems and maintain awareness of i
alternative pressurs reduction systems.
13 Core Ladle Identify the advantaEes and disadvantages, real contributions to risk reduction (positive, negative, neutral) and impacts of additior, of this feat;te.
- 14. Residual Risk Reduction Evaluation Provide the capability to baseline a limited number (2-4) of plants using detailed PRA studies L
(e.g., Zion-Indian Point, NSAC/ Duke, Limerick) and I do risk tradeoff evaluations of alternative preventive or mitigative features and risk sensitivities of key phenomenological issues (e.g.,-H burn, steam pressure).
- 15. Integrated Model Definition and Analysis Provide the integrated analyses of the dcminant sequences for representative plants and integrate the models developed in the previous tasks into this integrated analysis. This will include the following tasks: .
- a. Define MARCH / CORRAL Use Summarize current experience with MARCH / CORRAL application.
- b. Containment Analyses Perferm analyses for representative containment / system types for dcminant accident sequences and necessary variants.
- c. MARCH /00RRAL Improvements Define program for improving MARCH / CORRAL
models and implement, if desired.
- d. Integrate Phenomenology Models into Analyses Include the results of the phenomenological development activities into the integrated transient analysis.
See Appendix A-1 for more.information.
A.2 Schedule The preliminary schedule for the 15 AIF tasks is shown in figure II.A-1, I
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O.1.23.4.5.6.7.8910 . 11 . 12 . 13 14 . 15 . 16 . 17 18 . 19 20 . 21 . 22 . 23 . 24 .
- 1. -
0 2.(1.) O Initial Dominant (2.) " g Dominant Sequences (3.) " t 15 3 j)ContagrmentEventSequences a
- * ~ _ Interim i Final flodels
) y 7 15 Lit Survey y 9(2. ) Experie ntal refinitive Program
) Dita
(*) I, 15 -- -
5.(1.) V OJeneration Rate L Amount For If2 (2.) Position Paper 8 * " "U 3
, er - 112 Combuction Limints 6.(1.) e o IL, Detection (2.) y C O Pre-Inerting (3,) O Fogging / Spray Mitigation
- 7. 4 OEquipment Survivability n 8.(1.) fLitSurvey. Interim Firal 4 4 ,
(Final.
Definitive Survey Lit Interim hinal 9.(1.) O 10 (P.) 4bIII O , Liquid
- ( ") QVented containment Pathway
- 8(1.) Ladle St tStudies y, .0M 1/ } 15 14 g
- 14. Detailed PRA I
>C':S 4 13 O User Seminar- ORisk 15.(1.) ** "
.) 23 5 5 5 8 4 f g g gg 4 I: valuation (I . )
8 (5.)
f O BWR IIeatup Code o
lh s
- Identified Contingency tHe Integrate with DOE /EPRI PRELIMINARY PROJECT SCHEDULE Figure II.A-1
A.3 STA *r, T/bs consi:lering participation in'the in% pFdge,
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- 3. Electric Power Research Institute (EPRI)/TVA/ Duke /AEP B.1 Scope EPRI has developed the following tasks and has received proposals fecm the listed organizations to accomplish each of the projects.
- 1. Development of preliminary testing of deliberate ignition systems (Rocketdyne Division of Rockwell);
- 2. Experiments and analyses on basic hydrogen combustion phenomena including the effects of steam, turbulence, and the potential for transition to detonation (AECL Whiteshell);
3 Experiments on hydrogen cor. trol methods including water spray,; fog, and Halon (Acurex);
4 Measurement and analyses of nydrogen mixing and i
distribution with natural and forced convection (HEDL- }[ ) .
See Appendix A-2 for m;re information.
I t.
B.2 Schedule The preliminary schedule for the four tasks is shown in figure II.B-1.
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1-l Proposed Schedule for EPRI Tasks j
i 1981 11/1 1/1 3/1 5/1 7/1 9/1 11/1 i Igniter Development i
ilydrogen Control Studies
, TAcu7ex)
Ilydrogen Combustion Studies (AECL,Whiteshell) i I _ _ _ _ _ ,, jiydrogen Mixing Studies (HEDL-W). )
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Figure _II.B-1 3_
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B.3 status Details of the EPRI program are still being finalized.
TVA, Duke, and AEP have agreed to participate fully in the funding and manage =ent of the EPRI program.
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C. Westinghouse /TVA/ Duke /AEP 4
TVA, Duke, and AEP are cooperating with Westinghouse in two major experimental and analytical efforts described in this i
section.
1 C.1 Fenwal, Incorporated a
C.1.1 Scope Westinghouse, under authorization from TVA, Duke, and '.EP, sub- tracted Fsnwal, Incorpe 4ted, of Ashland, Massachusetts, to perform t.'1e phase 1 and 2 igniter testing
, program.
1 The purpose of ths testing program was to:
Phase 1 - Determine if the igniter would burn hydrogen at concentrations of 8 to 12 l percent for various environmental conditions of pressure, temperature, air flow across igniter, and humidity. <
Demonstrate igniter durability.
4 Phase 2 - Establish the lowest hydrogen
concentration at which the igniter would initiate burning.
Determine the igniter's ability to function in a spray environment.
Measure the gross effects of a hydrogen burn on a representative sa=ple of equipment.
Confirm multiple burne due to continuous addition of hydrogen.
Provide =cre e=pirical data for support of igniter licensing.
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, C.1.2 Schedule and Status l
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All Fenwal testing has been completed. .A report i i
by Fenwal, Incorporated, on Phase 1 testing and an evaluation report by TVA and Westinghouse on 4
Phase 1 and 2 testing have been completed and
! were submitted to the NRC about December 1, j 1980. (See Appendix N of Volume 2 of the TVA ;
j Sequoyah Nuclear Plant Degraded Core Program '
- t Report.) The Fenwal report on Phase 2 is due 3
shortly.
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C.2 CLASIX Modifications C.2.1 Scope TVA, Duke, and AEP have authorized Westinghouse / Offshore Power Syste=s to implement the following modifications in the CLASIX code:
Addition of structural heat sinks Addition of structural hett transfer cc:' relations Addition of air return fan head / flow model l
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C.2.2 Schedule These modifications will be completed during the first quarter of 1981.
C.2 3 Status CLASIX with structural heat sinks currently being debugged.
Radiative heat transfer module under development.
Development of air return tan model pending receipt of information from tan manufacturer.
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J D. TVA/ Duke /AEP i
D.1 Halon (Atlantic Research Corporation). ,
D.l.1 Scope
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- i TVA, Duke, and AEP have authorized Atlantic ;
Research Corporation to perform the folicwing tasks:
Preliminary Halon injection system design i
i Investigation to determine if combustion of inerted mixtures can be initiated within a J
blast wave l
l Datermine amount of Halen that may cecompose l postaccident inside containment I
l Study the change in water chemistry due to
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H&lon decomposition
'i Investigate additives to prevent Halon i
decompositicn I
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i D.1.2 Schedule Interim report submitted - 11/15/80 Work of Atlantic Research Corporation to be finished - 12/15/80 Final report to be presented - 1/15/80
D.1 3 m ;atus Watts Bar Nuclear Plant visited by Atlantic Research Corporation personnel and their subcontractces.
Information concerning ice condenser containments sent to Atlantic Research Corporation to aid them in their study.
Information concerning containment materials sent to a subcontractor to. Atlantic Research l
Corporation. .
Interim report received by T7A/ Duke /AEP (see Appendix A-3).
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- D.2 Electromagnetic Interference (EMI) Study D.2.1 Scope !
TVA, Duke, and AEP have authcrized consultant Dr. Bernhard Keiser (Keiser Engineering, Vienna, Virginia) to perform the following tasks:
Assess the electromagnetic interference emissions ,
from spark-type igniter for:
Direction Frequency Intensity Eff! cts on instrumentation l
Design suppression or shielding equipment which is compatible with:
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c Established seismic requirements l
Flow and combustion requirements 'if suppression equipment is located around the igniter)
..._m._ _ , , _ . _ _ . _ . . - . . - . - - . . _ ,_. . _ . . , - . . ,. ,,- ,
Test suppression or shielding equip =ent to verity design.
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D.2.2 Schedule Provide EMI consultant with one Flaregas Corporation igniter, Model Number ETX-105 -
12/1/80 Provide consultant a list of instrumentation located in containment, the manufacturer of this instrumentation, and a contact at the manufacturer for technical information - 12/1/80 Test igniter for emission profile - 12/8-9/80 Report on igniter testing - 1/20/81 Shielding / filtering preliminary design complete -
2/13/81 Onsite testing of shielding / filtering design complete - 3/3/81 Final report o
- onsite testing complete '- 3/20/81
D.2 3 status Consultant has received the list of instrumentation and a contact for each manufacturer involved from TVA.
Consultant has received the Flaregas igr'ter.
Testing of the igniter for emission profile to begin December 8, 1980.
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D.3 catalytic combustor D.3.1 Scope TVA, Duke, and AEP are currently evaluating -
proposal from Acurex Corporation to perform the following tasks:
Investigate catalyst flammability limits and heat release capabilities at:
- inlet gas temperatures below 250 F
- low hydrogen concentrations in the presence of poisons
- water concentrations from 5 to 80 percent .
At each point, identify:
- Oatalyst light-off temperature
- pressure drop across catalyst
- combastion efficiency
- bed temper & Lure profile
maximum throughput
~ m , e-. ,.-g- ,e,-. , --m p .-- - , +--w - -r ----, 4 - , , -- .-- , - - ,,---w. , y a - , x-
D.3 2 Schedule The experimental work would take approximately two months.
The final report would be presented approximately one month af ter completion of the l experi= ental work.
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D.3 3 Status The proposal frem Acurex is currently being evaluated and defined by the utilities.
No centract has been approved, l
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D.4 Fogging i
D.4.1 Scope TVA, Duke, and AEP have agreed to participate in the funding and management of the EPRI program (see B above) which includes the follouing tasks which have been proposed by Acurex:
i Effect of fog en icwer flammabilit: limit 5
i Effect of fog on a deflagration Efftet of fog on the transition to detonation ,
Effect of deflagration on equipment with a fog present T7A, Duke, and AEP are currently pursuirg
~
additional consultants to aid in the 4
investigation of fogging as a hydrogen <
r mitigation.
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D.4.2 Schedule Acurex preparation for experimental work will begin 1/1/81 and end 3/31/81.
Ac:1 rex experimental work will begin 4/1/81 and end 7/1/81.
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D.4.3 Status Acurex has located a test facility for use in this study.
Details of the EPRI program are still being finali::ed.
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i E. TVA 5
, In addition to the preceding, TVA is independently pursuing l other areas of de$raded core studies which are outlined in this section.
E.1 Browns Ferry Nuclear Plant Probabilistic Risk Assessment ,
! (Pickard, Lowe, and Garrick)
! E.1.1 Scope
- In an effert to quantify the risk to public health and safety cf the Browns Ferry Nuclear ,
- Plant, TVA has contracted the firm of Pickarh, Lowe, and Garrick (PLG) to perform a risk assessser.t study of Browns Ferry Nuclear Plant unit 1.
l Specific tasks to be accomplis.ted in the study include:
! - Identification of dominant event sequences leading to the Browns Ferry Nuclear Plant risk, including quancification of their probability of cc:urr e nce.
l l - Faul; trees wil be developed to evaluate f
the contribution of component failure to
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the total system failure. c trator action and common cause failure will be ine'uded.
- - Specific Browns Ferry Nuclear Plant site characteristics will be used to evaluate a
radiological consequences.
- A comparison of the Browns Ferry Nuclear l
Plant risk with other nuclear plant risk studies and acknowledged societal risks {
j will be performed.
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.l During the study,.PLG is to train TVA personnel I in the techniques of risk ascessment.
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E.1.2 Schedule The study began 10/80 Dates for major milestones
- D3ta analysis, event trees, and fault trees -
3/81
- Explant consequence model assess =ent - 4/81
- Seismic analysis reports - 7/81
- Explant consequence analysis - 9/61
- Final report - 12/81
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l E.1.3 Status Tasks coc:pleted or presently underway:
- Obtaining of plant specific maintenance and operating data
- Identificatien of preliminary event initiators
- Definition of event sequence diagrams Near !bture tasks
- Accident sequence analysis
- System failure analysis
- Seistje analysis l
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E.2 Sequoyah Nuclear Plant Full-Scale Safety and Availability Analysis (Ka:an Sciences Corporation)
E.2.1 Scope The full-scale safety and availability analysis of Sequoyah Nuclear Plant being performed by Kaman Sciences Corporation (KSC) with EPRI funding and TVA cooperation has several objectives.
- Qualitative and quantitative safety, reliability, and availability estinates
- Sensitivity studies identifying eceponents, equipment, procedures, and operator action with most significance to safety and availability
- Identification of system components in 1cw order fault sets affecting safety and availability
E.2.2 Schedule Phase I (preliminary assessment) 1/31 Phase II (final assessment) 1/82 e
.,ar -
y
E.2 3 Status Comprehensive system models have been developed.
Preliminary top level models and a plant availability assessment have been drafted.
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- E.3 -Consequence Analysis E.3 1 scope Provide TVA capability to analyze phenomena associated with degraded core accidents l Evaluate key sequences for Sequoyah and other TVA plants j Multifaceted analysis encompasses
- Primary system thermal hydraulics (PT and 7
core melt) 1
- Contai.nment repsonse (PT, burning, and concrete interaction)
- Fission product transport (aerosol and plating)
- Evalua: ion of public risk l
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E.3 2 Schedule
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Consequence analysis code package 1
(MARCH / CORRAL /others) - 12/80 i
l Develop Sequoyah base case models - 1/81 1
Obtain consultant and conduct consequence assessment training - 2/81 Identify high priority accident scenarios -
2/81 Run MkRCH analyses - 3/81 Input MARCH results to consequence codes -
4/81
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- Identify needed MARCH improv2ments 4/81 l
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Input TVA MARCH experiences.to industry code improvement effort - 6/81 Assess analysis results for development /
verification of TVA permanent hydrogen control system - 3/81-7/81
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i i E.3 3 Status l
j Latest. MARCH version obtained (October 1980 and November'10 update)
{
1
- CCRRAL/CRAC obtained from SAI j- Sequoyah base case model prepared, testing begun ,
, S2D, TMLB', and AD sequences selected for preliminary consequence assessment f
Battelle, Columbus Laboratory, selected for
- degradea core analysis training program
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i E.4 Singleton Testing i.
E.4.1 Scope TVA has continued to perform igniter reliability I
. and endurance testing at its Singleton Lab.
1 Several Genersl Motors 7G glow plugs were 3
energized with voltages ranging frem 11.0 volts
- , ac to 1t.0 volts ac, and the surface l
temperatures at the different voltages were noted.
~
J 302 General Motors 7G glow plugs were subjected
, to a preconditioning test designed to eliminate-t plugs with manufacturing defects.
50 GM glow plugs were selected at random from .
the group of plugs which successfully passed the preconditioning test for acditional cycling and
. endurance testing.
E.4.2 Schedule and Status Endurance testing of the 50 GM glow plugs is continuing (see Appendix A-5 for further infor:ation).
Similar reliability and endurance testing of Bosch glow plugs will begin in the near future.
E.5 Severe Accident Sequence Analysis (SASA)/(ORML)
E.5.1 Scope The NRC is conducting a severe accident sequence
, analysis (SASA) program which involves four national laboratories. TVA is participating with Oak Ridge National- Laboratory (ORNL) in its SASA studies involving Browns Ferry Nuclear Plant unit 1. The purpose is to improve best-estimate understanding of the phenomenological sequence of nuclear reactor accidents with partial or total core melt and to determine improved means for mitigating the accidents and containing the fission products.
Progran products include:
- Documented calculations of plant response to a broad spectrum of accident sequences including i
events beyond the design basis
! - Gra... cal overviews of the progression of t
accident sequences as a function of time
- Analyses of operatcr information needs, alternattve mitigating or ag2ravating actior.s, and consequences of those acticns
t
- Delineation of accident management strategies i.
Program tasks include:
- Develop accident sequence charts with timing
[ information to guide potential corrective action for a station blackout and a loss-of-heat-sink scenario
- Analyze system in,teractions e - Analyze factors leading to direct failure of containment
- - Identify critical equipment and instrumer.tation and critical requirements for operator action
- Analyze fis31on product behavice and inherent retention phenomena
- Determine _ limits of coolability for varying fuel melt configurations
- Determine limits of containment capability for varying fuel melt configurations and varying degrees af malfunction l
1
,m._ ,, -. - .- _ . ~ . . , . _ , , - . . , . - . . _ . . _.
i 1.
E.5.2 Schedule
- Develop time-line chart for station blackout case with potential corrective action - 12/80
- Integrate instrumentation modeling with overview model - 1/81
- Develop list of pertinent instrumentation,
', locations, functi,on, and potential effects of i
station blackout accident sequence - 2/81
- Complete fission product transport calculations for station blackout sequence -
i 9/81 i
- Issue draft final report for station blackout sequence - 10/81 .
i I
E.5 3 Status
- Time-line chart for unperturbed station blackout sequence has been developed.
- RELAP calculation has been performed for the core with no ac power.and no ECCS function
- MARCH has been made operational, and a EFN model is beiag eqnstructed
- An (incomplete) overview model (simulation) has been developed for comparison with more detailed analyses.
I i
1
+
E.6 Ice Condenser Containment Code E.6.1 Scope
- Develop a TVA in-house capability to analyze pressure and temperature transients for severe conditions in an ice condenser containment.
- Present ice condenser containment codes available: .
- a. LOTIC 'destinghouse proprietary
- b. ' CONTEMPT-4-Developed by EG&G - not operational due to errces
- Possible strategies a
- a. Modify existing containment or sub-compartment codes (CONTEMPT-LT, COMP ARE, etc . )
i
- b. Write a new code I
Decisicn CONTEMPT 4 was chosen for the basis of-the TVA code because it offerad:
i i
-?<, ,-17~~ , , .,-- . . - ,,e,-,ac. ,e.,.-....--er..v.,,v-n v , . , . ,n, ,. -- e ,, , rm. - ,+ --,, , .- - - - - - g w , - -
- a. State of-the-art features such as dynamic storage allocation
- b. Multicompartment model l
- c. Ice condenser
- d. Basic containment features available; e.g., sprays,, heat sinks, fans, and heat exchangers
- e. Potential for rapid development l
l l
l t
c l
l
E.6.2 Schedule-The code development program consists of three parts:
Part I
- Obtain a working code that will analyze conventional containment transients (LOCA,
! MSLB ) - 1/15/81, i Part II Expand- and modify the code to allow evaluation -
of Class 9 events - 4/1/81 i
- a. Add a hydrogen burn model i
i 1 -
- b. Consider multicomponent atmosphere (H '
2 N ' 0 , CO ' H 0, etc.)
2 2 2 2
- c. Model radiative heat transfer from atmosphere to heat sinks
- d. Extend range of code tc permit high temperatures Part III l
Jontinuing development of a best estimate code - ongoing beginning 4/1/81
- a. Develop a dynamic ice condenser model
- b. Improve abilities to track H concen-2 trations l
t 0
I l
E.6.3 Status I
Part I - approximately 50-percent complete Part. II - approximately 10-percent complete Part III - currently in planning E50337.01 -
APFriDIX A-1 AIF PROGRAM - TECHNICAL DETAILS go V ]T I \
INITI AL PROGRAM P' AN We c' J Ujl . 4 This initial program plan identifies Se integrated efforts believed necessary to generate sufficient technical infor e.icn to develcp rational positions on key degraded core issues and to provide the base for successful degraded core rulemaking hearings.
The program has been scoced to incorporate the results of known programs--
incustry, NRC, foreign--and includes only those efforts necessary prior to participatien in the rulemaking.
Based on current knowledge, it is unlikely that any simple sclutiens are available; there are gaps in the technological information which must be filled to develop and defend ratienal positions, and there is a nee ' for effective understanding of the complete picture r'egarding degraded cort issues and strong management of an integrated program.
The program is focused on obtaining sufficient information, not defeloping inforration for the sake of information.
The program is defined in related segments. These segments have be*n c'erivec from an overview of the degraded core situation as follows.
The industry will develop rational positions related to the characteri:a-l l
tion of residual risk from degraded core conditions and the potential
{ alternatives for further prevant19, or mitigation of residual risk.
A safety goal or criteria that provides a measure of acceptability is a necessary concition for effective avaluation of residual risk.
The release of radioactivity to the environment is cause of deleterious consequences. Reieases can occur only if both arge quantities of racia-c:tivity are produced and releasec from the primary system and the con-tainment is ineffective, i
l The release 'of radioactivity to the environment is the cause cidelete deleterious consequences. F.eleases can occur only if toth :arga quan-l titles of radioactivity are produced and released from the primary system and the containment is ineffective. The attenuation prior to containment failure must a'.so be considered.
Even if releases to the environment are postulated, significant attenua-tion mechanisms are physically real and act to reduce the consequences.
Residual risk evaluation must include both the probability of occurrence and the consequences. Reducing either the former through prevention or the latter through mitigation is a viable means of risk reduction.
Based on these general precepts, the program structure develops and inter-relates as described below.
Define the role of the specified safety criteria. ,
Identify the dominant sequences of events contributing to risk--dominant means those where the combination,of probability of occurrence and pre-dicted consequences of the sequence is significant in the risk.
Identify the core degradation. and containment transient phenomena which are critical to determining the challenge to the containment or the quan-tity and timing of reltase of activity.
For critical phenomana, develop sufficient information to adopt rational positions en the magnitude and effects on containment or release. Based i on previous studies and experience, the critical phenomena include the.
generation and burning of hydrogen, steam generation resu'. ting from. core cebris-water interaction, care debris coolability f acluding consideration l
I of core debris-concrete interaction, and radioactive product transit.and deposi tion.
L Perform integratec analyses of the spectrum of-dominant sequences with appropriate .anges for tna critical phenomena to determine the margin
- h currently existing for tcleration of degraded core events.
l Identify the advar.tages ar.d.cisadvantages of. alternative -preventive or
- mitigatise maasures incluoing can'cepts actively being pursued by flRC.
I Quantify tne risk reductions achieved and the relative risk reductions l
l achieved if alternative preventive or mitigative measures are considered.
3 '9 }
D D .
~~ ' #
The separate tasks are:
- 1. Safety Goal / Criteria Application
- 2. Selection of Dominant Sequences
'3. Identification of Phenomenological and Containment Transient critical Sequences
- 4. Steam Overpressure Phenomena (In-Vessel, Containment)
- 5. Hydrogen Generation and Burn
- 6. Hydrogen Burn Control
- 7. Equipment Survivability for the. Degraded Core Environ ent i 8. Core Debris Coolability j 9. Containment Structural Capability L
- 10. Evaluation of Liquid Pathway Dose
- 11. Fission Product Liberation and Removal l
l
'2. Vented Containment Systems ,
- 13. Core Ladle
- 14. Residual Risk Reduction Evaluation
- 15. Integrated Model Definition and Analysis For each task, the followirg sheets identify the relationship of the task to overali d jectives, the information known to be available, the scope of the recomrrenced actions, the schedule and budgetary estimates.
- 1. SAFETY GCAL/CRITERIAL APPLICATION Relationsnip to Objectives: A safety goal / criteria is a necessary condition
! for proceeding with the rulemaking. There must be:
l
- a. Acceptability limits for individual and population health effects including both probability and consequences,
( b. Risk / benefit criteria for alterr.ative evaluation I c. Definition of methods for evaluation of cegraded core conditions (realistic analysis of transients, no arbitrarily postulated equipment failures, use of realistic ultimate containment pressure capability, etc.)
Without these items, there is no common basis for_ decisions regarding
- acceptacility of current designs, the relative benefits of alternative l
features, and the enalytical e asults obtained for ontainment transients.
Available Information: For the proposed program, it has been assumed that the development of the safety criteria has been successfully completed through ' current industry efforts. Since the current AIF goal propesal is consistent with the needs, this assumption seems warranted.
With respect to methods for evaluation, information is available from on-going work in the following studies: Zion-Indian ooint,-TVA/Ouke/AEP, Limerick, and NRC companion studies. However, a comprehensive written position is not currently available.
Scope of Recommended Actions:
- a. Generate position paper on the role of safety goal / criteria in the degraded core rulemaking activities
- b. Generate comprehensive criteri'a for methods for evaluation of degraded core conditicc3 Schedule / Budget: It is estimated that 2MM of effort will be required to generate the position paper and comprehensive criteria. These must be completed prior to initiation of major analytical or design alternative evaluation efforts.
Significant broad based review of the criteria and position paper are required, and the effort necessary is assumed contributory on the part of the involved and interested parties.
- 2. SELECTION OF DOMINANT SEOUENCES Relationship to Objectives: Understanding the sequences of fatiures neces-(
sary to cause a- degraded core condition is fundamental to analyzing the
(
! resultant containment challenges of evaluating oreventive or mitigative -
features. This understanding must include the mechanisms (equipment
( failures, operator interactions, etc) and the relative probabilities 'and
! consequences of the sequences.
The dominant sequences are t.;csc which centribute measuraoly to tne risk, i.e., thosa sequeness whose combined probacility anc' consequences are I
relatively higher than the remainder. By selecting the' dominant sequences, the analytical and evaluation efforts are focused on areas where significant gains can be achieved.
Available Information: For defining dominant accident sequences, a con-siderable technical base is available from similar studies, either complete or due to be completed in the near term. These include: the Reactor Safety Study (WASH-1400), the NRC Reactor Safety Study Methodology Application Program (RSSMAP) which includes studies on four additional reactors, the individual plant studies including Zion-Indian Point Mini-WASH 1400 and complete study, TVA Sequoyah studies, the NSAC/ Duke Oconee study, the Philadelphia Electric Limerick study, and others.
In addition, studies on Auxiliary Feedwater Reliability, the IREP Program, and Inadequate Core Cooling studies each provide additional information useful in defining dominant accident sequences.
For the early phases of this program, the assimilation and integration of this available information is necessary. Although the information is useful, direct application without informed scrutiny would not provide the proper base for proceeding of particular importance is the inclusion of operating plant experience in defining the dominant sequences.
In the later phases of this program, integrating the results of. major on-going studies is necessary, since no resource is provided in'the program for performing studies to this level of detailed information.
Scoce cf Recorrmended Actions: The scope of this task is to define the j dcminant sequences ar.d rational for selection and provide cocumentation.
This scope is divided into three parts:
(1.) Ir.itial cefinition of "likely" cominant sequcaces basea on available matertal, cc ini-f al ranking of sequer.ces in terms of procability and .
consecuences and a definition of urrently available preventive and mitigatise (e.g., coa:ajament heat removal) systems would be prepared.
l
This effort would be performed by small groups of individuals highly familiar with the plant systems and operations supported by personnel thoroughly familiar with the application of Probabilistic Risk Assessment techniques.
This task would be performed at the outset of the program (approximately one month duration) by a group of utility engineering / operating, NSSS vendor, AE and PRA personnel. Following assingment to the team and a material review period, one meeting of each team would be convened to establish the initial 'ikely dominant sequences. Based on 2 MW per individual, 8 individuals for BWR, 6 indivuals per PWR NSSS vendor type, the total estimate is 13 MM, 4 CRU.
To maximize productivity, it is assumed that the necessary picked per-sonnel are made available and 'that the PRA personnel on each team are the same as assigned to "(2.)" below. .
(2.) Dominant Accident Sequence Assessment, Quantification and Documentation:
The objective is to quantify the dominant sequences defined in "(l.)"
identify any other s'equences that should be considered, provide pre-liminary consequence assessments, and document the process and rationale for selectica of dominant sequences.
Input to this task includes the output of the task "(l.)" above and the prelirinary containment sequence identification task. -
The output is a document identifying how and why the dominant ' accident sequences were chosen and integrating the results of previous studies into the industry position. Identification of similarities and dif-ferencas between the final result and other studies is important.
This task is estic .ted to require 6 MM for all BWR types and 4 MM for aach PWR type over a 4-month pariod.with 6 CRU. It is assumed that this task will be perfc.ved by parsonne'. highly qualified in Probabilistic Risk Assessrent tachniques who participated in task
' i.)" above.
(3.) Update to include detailed study results: After detailed studies (Zion-Indian Point, NSAC/ Duke, Limerick, TVA, etc.) are completed, these results would be integrated into the dominant accident sequence selection and rationale. The detailed studies should provide the in-depth technical basis for the dominant accident sequence selection.
This task is estimated to recuire 6 MM of effort assuming personnel familiar with the detailed studies are available.
Schedule /Budcet: Given above.
- 3. SELECTION OF CONTAINMENT PHENOMEN0 LOGICAL SEQUENCES Relationshio to Objectives: Identification and understanding of the criti -
cal phenomena of degraded core conditions which lead to containment challenges is necessary to evaluate the inherent plant margins and the effects of proposed mitigating features. The identification of the contain-ment sequences in conjunction with the dominant accident sequences focuses the analytical and experirrental efforts on the critical-areas related to system or containment failure challenges. A comprehensive identification of containnent sequences assures that analyses or features are considered only if broadly significant.
Available Information: Tne Reactor Safety Study (WAsii-1400), NRC studies en mitigating features, and on-going industry studies (Zion-Indian Point, Lirrerick, TVA/ Duke /AEP) each provide information on core degradation phenomena and the importance with respect to centainrrent challenge.
Further information in specific areas (hydrogen generation and burn, core degradatio,n progression, etc.) is identified in tasks below.
Scope of Recorrended Effort: The scope cf this activity is to generate containment phenorrenological event trees (cr equivaler.t) for the major reactor systems. The containment event tree (or equivalent) would start whera the dominant accident sequence effort rarmirates, i.e. , conditions for core cegradation have been postulata: to occur. The ever.t tree would identify tha significant branch points thereafter until recovery or
t containment failure (with associated releases) terminate the progression.
The significant branch points (nodes) would be chosen based on knowledge gained from current studies on the phenomena which could lead to contain-ment challenge, e.g. , hydrogen release and burn prior to core melt, steam pressure generation from core debris-water interaction. By properly cefining the. nodal decision points, the event tree (or equivalent) can be used- to determine the best estimate progression paths as well as less likely paths, eliminate physically unrelizable paths, provide a framework for relative probabilistic evaluations of progressions, and focus the analytical and e>perimental efforts. The dominant sequence efforts coupled with the containmant event tree (or equivalent) provide the framework for evaluating the residual risk reduction .of proposed mitigating alternar;:s.
The intent is to generate a minimu,m number of containment phenomenological event trees which provide comprehensive generic coverage of the' core degradation and containment transient phenomena for light ).ater reactors.
For this estimate, it has been assured that two (cne for PWR an_d one for i BWR are necessary).
The effort is in two phases: The first to establish the event teee logic, and the second to provide integration of the phenomenological developments of subsequent tasks and estimated ranges of probabilities for the nodes.
Budcet/ Schedule: Based on the availability c' current work and using o
l personnel thoroughly familiar with the plant types and phenomenology, the
[ development on the initial containmer.t event trees (or equivalent) is estimated to require 4 MM for each (BWR and PWR). This effort requires l input from the initial selection of dominart accidents and provices funda-
, rental guidance for the remaining major activities.
l Giver. the event tree structure, analytical and phenomenological efforts, integration and estimates of probability ranges would require 3 MM late j in the program.
L-
_g_
4, STEAM OVERPRESSURE PHENCMENA (IN-VESSEL, CONTAINMENT)
Relationshio to Obiective: Production of large energies or quantities of steam from the interaction of core debris with water is one of the major postulated mechanisms for causing containment failure. Since a wide range of steam production rates can be calculated depending on the assumptions used in the analysis, it is necessary to develop technically based positions on the phenomena involved and the uncertainties in the theoretical and experimental bases for these phenomena. For realistic evaluations of residual risk, bounding calculations on the production of steaming are misleading at best. The proper approach is to evaluate the phencmena realistically based en current kncwledge, specifically identify uncertain-ties, and provide an integrated assessment of the potential for containment challenge resulting from core-debris-water interaction.
Since the amount of debris, rate of interaction, and initial conditions of debris-water-system complex, are all interrelated, this phenomenological evaluation includes the determination of appropriate models for core degra-dation rrelt progression, (included in task 8) necessary conditions for steam explosion initiati~on, dynamics of mixing and steam generation between core debris and water, and conditions for missile generaticn and analyses of results of missiles.
Available Information: The Reactor Safety Study (WASH 1400), NRC studies related to mitigating features, vapor explosion research in the metals and LMFBR areas, and Zion-Indian Point / Limerick industry studies all include infomation relating to these phenomena.
Extensive researca programs in these areas have been or are being carried out at Sandia, Arg:nne, Hedl, Brookhaven, Battelle-Columbus, Purdue University, and German facilities, as well as various other sites.
Sccce of necormended Act'ons: The overall scope of the activities listed bel.:w is to provide sound phenomenological models for the progression of core melt for the identified dominant sequences, the conoitions necessary for occurrence of ;te2m explosions and effects of resultant explosions
10-based on proper conversion efficiencies, mixing dynamics of core debris-water interactions, steam generation rates for core debris-water inter-actions, and the dynamic effects of large scale core debris-water interactions on the materials involved given typical reactor plant geometries . The task is divided into parts. For each part, the intent is to develop the following information:
- a. Description of phenomena involved j b. Relationship of phenomena to containment challenge
, c. Description of the physics underlying i.he phenomena
- d. Available theeretical models and experimental evidence
- e. Best estimate progression path
- f. Range of uncertainties that should be considered
- g. Recommended model(s) for analysis
- h. Recommended experimental effor'ts (1.) Steam Pressure Generation and Steam Explosion The task includes providing the above information for the interaction i of large quantities of core debris (molten) with water in several
~
possicle configurations: Core debris poured into water with and without elevated pressure conditions initially, and water poured onto core debris. The necessary and sufficient conditions for occut rence i of steam explosion would be identified. The appropriate range of i
thermal to mechanical energy conversion associated witn physically l
relizable steam explosions would be defined.
For sten pressure generation, mechanistic models for she rate of heat transfer and the amount of heat transfer would be developed.
Where hydrodynamic effects are likely to be significant, the models should provide for inclusion. Particle size effects hould be included based on the information devaloped below ir. (2.)
(2.) Dynamics of Mixing and Steam Ger:aration This task inciedes providing the above informa: ion fcr the dynamics of mixing !arge quantities of core debris' and water. The physical requirements that must 'be met for coherent, rapid mixing would be
- - - . ,- , e g- ,,,,.,,,,y- -- ,y, , ..yw-r- e -ea
established. Included would be the patential effects of the energy required for mixing and mechanisms for supplying the energy, local thermal interactions, hydrodynamic dispersion effects, particulari-zation of the debris, crust formation among others. Based on the information developed, mechanistic models for steam generation would be developed.
Cependiag on the results of this effort and the assumed pursuit of the current NSAC and planned EPRI program with ANL, experi-4 mental work broadening the technical base may be desirable. This could include: varying core debris injection mode, varying initial pre:sure conditions, and simulant material tests to establish specific mechanisms. This effort should presently be considered contingency.
(3.) Structural Response of Equipment Based on the results of (1.), this task would establish' the conditions for missiles or ex-vessel steam exp',osion phenomena. Establishing t: : aecessary conditions for missiie generation for physically reali-
~
zable steam explosions includes identification of the means for rapid momentum transfer to the structure. Based on analyses to date, it is li k ely that such transfer is improbab)g.at best. Ex-vessel steam explosion phenomena and resultant structural loadings will be assessed.
-~
It is assured that the currant study results provide a reasonable assessment and that extensive structural analyses will not be required.
Budcet/ Schedule: For each task above, the following sequence would apply--
- a. Literature survey and precise definition of program and results (1-3 months after initiation)
- b. Interim Report covering Items A-E ir. detail (6-9 months after initiation)
- c. Final Report including medels and experimental data (12-18 months after1 ini tiatior.)
, - , , . - - , - -~ . , , .
l The estimated resources 'to complete the tasks are:
1 (1.) Steam Pressure Generation and Steam Explosion Phencrena -
18 MM plus 40K (2.) Dynamics of Mixing and Steam Generation -
24 MM plus 75K (30 MM plus 100K additional to EPRI-ANL contingency--
performed after decision based on Interim Report) l l
(3.) Structural Response of Equipment ;
i 10 MM plus 20 CRU
- 5. HYDROGEN GENERATION AND SURN
- Relationshio to Objectives
- The results of ignition of large quantities of hydrogen represents one significant postulated mechanism for causing con-tainment failure. A wide range of postulated hydrogen production rates and amounts, hydrogen distributions, and hydrogen ignition phenomena can be calculated or used in calculations of containment transient pressure loadings.
Development of technical bases for each of these areas including uncertain-l ties is necessary to the generation of intelligent positions on the potential for containment challenge from these phenomena. The proper approach is to evaluate the phenomena realistically based on current know-ledge, specific. lly identify uncertainties, and provide an integrated l
assessment not to do bounding or physically unrealistic calculations.
I Available Information: Considerable literature exists related to the com-bustion of hydrogen. Compendiums of this literature have been prepared by Sandia and EPRI/NSAC. In addition, significant analytical and experimental
(
work has been performed outside of the U.S. (e.g. , Battelle - Frankfurt, Ge rmany. )
i
! EPRI/NSAC and the Department of Energy a.e sctively initiating or pursuing -
programs; analytical and ex;erimental coordinatfor, wita these is mandatory.
Work compiated or in progress in the Zio..-Indian Poiat, Limerick and TVA/AEP efforts is directly applicable.
4 I
Sccce of Recommendec Actions: The scope of this task is to provice sound phenomenological models for the generation, distribution, ignition and combustion of hydrogen as related to LWR conditions. The task'is divided into parts. For each part, the intent-is to develop the following 4
information:
s a. Description of phenomena involved
- b. Relationship 'of phenomena to containment challenge l
- c. Description of the physics underlying the phenomena
- d. Available theoretical models and experimental evidence
- e. Best estimate progression path
- f. Range of uncertainties that should be considered I g. Recorrended model(s) for analysis
- h. Recorrended experi::vntal effo.-ts l (1.) Generation Rate and Amount of Hydroger.
- Fcr the dominant accident sequences, determine the rate and amount of zirconium-water or stainless-steel-water reaction producing hydrogen for both , intact core geometry and core-debris-water. inter-action progressions. Currently available experimental data and
! models whould'be used and improved to determine the best estimates of hyarogen production , rates and amounts r d to identify the' appro-priate. ranges of uncertainties.
(2.) Hydrogen Distribution -
l This part includes two areas: 3 position paper compiling previous
, work on the large scale mixing enaracterisitcs of'hy'drogen and the-E conditions nece:sary to prevent-sign 1fic' ant stratification or pock,eting, and system (or small scale)' analysis of districution and mixing of hydrogen.
For the second area, determine analytically thE potar.tial distributions
- - assumng hydrogen rich releases (characteristic of the dominant 3.ccident sequences) irto air atmospheres fo.tconditions character--
istic of releases into containmer.t volumes, through suppression
pools, or though ice condensers of spray curtains. Included in these analyses are the effects of turbulence, geometry, heat transfer and condensation as important to determining the hydrogen concen-trations. Define the need for and boundary conditions for 'ecalized turbulent deflagration or detonation analyses. Based on material available, develop the necessary models for anlayses of these phenomena.
(3.) Comoustion Limits of H 2-Air-Steam This part includes the compilation of available material and develop-ment of mcdels for burning of hydrogen in conditions representative of the dominant accident sequences as developed in the containment event sequence. Included are the definition and characteri:ation of the flammability limits (upward propagation, upward-wideward-downward propagation, transition from deflagration to detonation, turbulent deflagration, detonation), effects of diluents including steam, temperature and pressure effacts on flammability limits, scale and geometry effects, and water spray / fogging effects. Definiticn of pressure developed, burn velocity and flame frcnt propagation velocity models would be included.
The EPRI (or EPRI/ DOE) progrim has been assumed to continue and to provide i informatien--particularly large scale experiments.
l l
The EPRI/NSAC/ANL program on hydrogen blanketing of the zirconium-water reaction would be a worthwhila, but nct r.ecessary addition as of today I
with rerpect of H2 generation ratas.
t l
l Budcat/ Schedule: For each of the above, the following sequence would apply -
- a. Literature survey and precise aefinition of program and expected results (1-3 months after initiation)
- b. Interim Report covering Items A-E fn detati _(d-9 months after initiation)
- c. Final Report :ncluding models and experimental cata 02-18 months after initiation) l l
The estimated resources to complete the tasks are:
(1.) Generation Rate and Amount of Hydrogen 15 MM (2.) Hydrogen Distribution 30 FN (3.) Combustion Limits of H 2-Air-Steam 8 MM For budgetary purposes, a contingency of 200K for experimental work in this area should be included.
- 6. HYOR0 GEN BURN CONTROL Relationshio to Objective: Since the burning of hydrogen provides a poten-tial challenge to the containment, means to prevent er control this burning must be defined and evaluated. The evaluation of these means would include l feasibility, potential advantages and disadvantages particularly fccused to evaluation of the benefits (negative, neutral or positive) with respect to risk reduction, and the-impacts of including the alternative devices.
Available Information: The Sandia and NSAC hydrogen compendiums provide '
a general source for information. The on-going efforts, particularly TVA, provide a substantial further source of information with respect to pre-inerting; significant industry effort has been expenoed and; data is available.
It has been assumed that present activities being carried out by TVA/
Duke on ignitors and Halen injection will be completed and will form the basis for, development of scund industry positions related tc the avalua-tion of these means for prevention or mitigaticn of burn.
i Sccoe of Recormended Activities: There are three areas in this task:
l survey of hydrogen detectors, evaluation of pre-inerting for containments not already evaluated, ar.d avaluation of fogging / spray suppressicn.
i
(1.) Survey of Hydrogen Oetectors Establish the capabilities of currently existing equipment for detection of hydrogen including sensitivity, respense time, environmental capa-bilities, etc. and document.
(2.) Evaluation of Pre-Inerting For a representative gorup of containments, cefine the benefits and hazards of pre-inerting based on the containment accident transients developed below. The primary focus of this task is to define the impacts on availability, maintenance, personnel hazards and operations of pre-inerting.
(3.) Fogging / Spray Suppression Cefine the necessary conditions for suppression or mitigation of large hydrogen burns through use of water spray cr fogging systems. Define the advantages and disadvantages for this type of mitigation.
Budget /Scnedule: The budget for these activities is identified as:
- a. Survey of Hydrogen Detectors 3 MM
- b. Eva'.uation of Pre-Inerting 12 MM (assuming 3 major type evaluations)
- c. Fogging Spray Suppression 3 MM These activities do not need to be started intnediately.
- 7. ECUIPMENT Sl;RVIVABILITY FOR ENVIRONMENT (DEGRADD CORE)
Relationship to Objective: In the definition and analysis of cegraded core sequences, certain equipment is assumed to remain operationai, and other equipment is assumed not to fall into an intolerable state. It is necessary to define what 7.inimum equipment must exist to per.'.it termination or to j monitor the st:tus of the plant. The environment in which this equipment
t a
i' i
t !
must operate must be defined and the capability of the equipment to i l
i survive must t! developed.
4 i
Available Information: Information currently exists on the definition of
{ necessary parameters as part of the TMI-actions. Information on environ-ments either exists through on-going studies or will be developed as part of this industry program.
a
) .Scoce of Recommended Activities: For five plant configurations (BWR, each NSSS vendor PWR, and ice condensor), the following tasks are recommended:
- a. Identify the minimum set of functions which must be performed or equip-ment which must r.at operate as a consequence of the environment to i permit termination of core degradation sequences or to monitor the status of the plant and return
- containment.
t
- b. Based on "a.", identify necessary minimum set of generic equipment
- c. Identify _ environments associated with the dominant sequences
- d. Evaluate the survivability of the equipment in "b." for the conditions in "c." and define tests if necessary. !
- a. Develop recommendations on equipment survivability criteria and document '
results of complete task.
Budget / Schedule: The cudget for this effort is estimated to be 4 3/4 MM l per type, or 24 MM total.
For testing 100K should be incluced in contingency.
This effort should start after the containment sequences are defined.
- 8. CORE C00tABILITY Relationshic to Objective: 'The progression of a postulated ccre melt is the dominant factor in determining ne potentia" for cor.tainment challenge.
The amcunt of the ore -f avolved coherar.tly (on a _reiatively short time scale) will effect the generation of steam pressures, tne release of :
hydrogen, the '.essel fai~ure moces, the distribution of material subsequent-to vessei failure, the ultimate coolatility of the molten material, and I
I J
1 i f 1
i the contair ment transients. Since the data base is currently limited to analytical /:heoretical models and small scale exoeriments, the range of i
! calculatec transients can te extremely broad. It is necesssry to develop sound phencmenological medels based on current understandi/g and data, '
specifically identify ranges of uncertainties, and provide i'tegrated l physically consistent assessements of the potential contair....it cnallenges.
l This phencmenological evaluatien includes the progression of core melt prior, and subsequent to attaining melt temoerature through loss of core gecretry, slumping into the icwer internals / bottom head, penetration of the I reactor vessel, and ultimate disposition. Further, the conditions for i termination of core degradation or melt progression would te deveicoed.
j Finally, the conditions for coolability of the debris, including considera-tions of debris-concrete reactions, wculd be defined. By using the con-tainment event sequences, an integrated assessment of the potential patns j and termination points would be provided and sound technical informatien developed to support the case.
Available Information: The Reactor Safety Study (WASH 1400), NRC studies,
^
Zicn-Indian Point Study, Limerick Study, LMFSR data a'nd foreign work all
, provide fundamental cata for this effort. Further, industry TMI-2 damage progression analyses and evaluations provide significant input.
l Scoce of Recommended Activities: The overall scope of this effort is to-l provide technically sound, phenomenological medels for the progression-l of postulated core melt for the dominar.t containment sequer.ce events. The
. task is divided into areas. For each, the intent is to develcp the folicwing information:
- a. Cescription of phenomena involved l'
- b. Relationship cf phenomena to containment challenge
- c. Description of the physics underlying che phe.7omena
- d. Avafiable theoretical models and experimental evidence
. e. Best estimate progression path
- f. Range of uncertainties that should be ennsidered
! g. Recommended model(s) for analysis
- h. Recommended experimental efforts
_ _ - - , - _ . - _.__-_.__ __ _ . .~. _ .-.._
(1.) Analysis of In-Vessel Core Melt Progressi:n and Reccolacility
~
or eacn of the deminant accident secuences, determine the Oregres-sien of the event fr:m boileff throuen major ;ecretry disruptien to penetratien of the debris tnreugn the core supporting structure.
The progression medels should ac: cent for prcper transfer of the heat of :ircenium-steam reaction into :ne fuel, interasseme!y radia-tien, fuel relecatien thermal prepagatcrs, melting /refree:ing, quenching and particulari:stien, and pcwer profiles.
8 (2.) In-Vessel C0clability, Yessel Penetration, Ex-Vessel C:olability The sc0;e of this effort is to establish the ifmits for in-vessel coolability of debris, the medes and timir.g of vessel $enetration, and tha limits for ex-vessel ,ccolability. The medels develoced would ~ account for de5ris 5ec quenching, heat transfer between core debris and structures, structural failure predictions, conditiens for and impact of crust formation, particulari:ation of debris, limits for coolability of debris beds including power density--
height--particle si:e--por:sity consideratiens--and other effects which would substantially increase or decrease the debris coolability.
(3.) Core Cebris C:ncrete Reaction The scope of this effort 'ncludes the critical evaluation of cur-l l rently existing models, develectent of rate of concrete penetration and ncn-condensible gas generation by refining current model estimates, and assimilating and fellcwing Sandia and foreigr. work in this area.
Succet/ Schedule: For each task above, the folicwing sequence would apply--
- a. Literature survey and precise definition of program and results (2-3 mcnths after initiation)
- b. Interim Raccet covering Items A-E tr. detail (9-15 months after initiatien)
- . Final Report incivd1ng accels and experimantal data (15-24 months after initiation)
4 The estimated resources to complete the task are:
i
- a. Analysis of In-Vessel Core Melt and Reccolability 50 PM 100 CRU
- b. In-Vessel Ccolability, Vessel Penetration, Ex-Vessel Coolability 60 MM 50 CRU 100K E toerimental
- c. Core Debris Concrete Reaction 18 FN
- 9. CONTAINMENT STRUCTURAL CAPABILITY l
Relationshio to Obiectives: The structural capability of centainment is the most significant mitigating feature identifiec to date. If the cen-tainment can withstand the pressure and temperature leadings imposed by the Postulated Core Degradation Events, there is no significant risk l
Establishing a uniform realistic base for determining the ultimate con-tainment capability is essential to the completion of the effort.
Available Information: NRC and industry studies are available for Zion-Indian Point, Duke, TVA, Limerick and other plants.
Recommended Scoce of Activities: The scope of this activity is in two parts: defining and integrating what has alread; been completed and i
identifying any residual issues; ana two, defining and implementing a program for evaluating inertial (detonation or turbulent deflagration) loads or containtrents.
(1.) The first activity is to chedule a seminar of utilities and associated consultants who have parformed realistic analyses of containment capability to identify what has bean done, what residual work may emain, and what criteria should be prcposed by the incustry for these
! : valuations. These resuits would ba documentad.
(2.) The second activity is to defir.e the inertial loadings which may be encountered (from Tasks 6 an'd 15) and specify the program of analysis of containment inertial load capability far performance. Strong con-l sideration should be given to enlistir.; 'sarsonnel experier.ced in weapons progra.n analyses for consultation if not perfomance of this effort.
l L
Budget / Schedule; f
i a.
2 MM to provide documentation assuming utility contribution o personnel to seminar b.
2 MM to define loadings; 20 MM to perform analysis I
The inertial loading The seminar should be scheduled early in the program. f initial conditiens activity would be initiated folicwing better definiticn o from Task 6 above.
- 10. EVALUATION OF LICUID PATHWAY COSE The potential for increased risk due to transport Relationshin to Objective; for interdiction of fission products through liquid
- pathways and the nee of these was raised by the NRC.
not a major risk contributor.
NRC Liquid Pathways Study, Sandia Study, 'd Offsho Available Information_: ide infor-Power Systems Liquid Pafhways Study, and Battelle work all pro i mation.
ilable.
In addition, work at Hanford'en leading and transport may be av If this issue is raised, integrate Recommended Scoce of Activities _: h feasibility available information and provide scoping information on t e time span and cost of source interdiction.
This work shoulc not be initiated .immeciately, and in Budget / Schedule:
fac: may not be ecessary.
The ef#crt for the aoove scope is 3 MM.
4 1
- 11. FISSION PRODUCT LIBERATION AND REMOVAL Even if containment failure is postulated, the Relatienship to Objective: i amount of material liberated and the depletion of this material prior to Evidence exists l reaching pcpu;ation is critical to determining the risk.
' that the current partioning and depletion is overly pessimistic.
EPRI and DOE are pursuing the development of a Available Information:
program to improve the models currently used.
Immediately after initiatien of the Recommended Scoce of Activities _:
industry program, contacts with DOE should be made to determine the scope i The intent is to integrate and schedule of tne program being impelmented.
the results of that progr m into the develcpment of the industry positions 4
Since it is likely that the DOE program will cover all on degraded core.
necessary activities. and that schedules could be adopted to fit the needs of this program, no effort separate from that program is presently estim
- 12. VENTED CONTAINMENT SYSTEMS _
One mitigating feature currently being actively Relationshio to Objectives _:
pursued by the NRC 15 the concept of venting the centainment to pre It is necessary to identify the advantages and disadvantages, failure.
real contributions to risk recuction (positive, negative, neutr&l) and impacts of addit cr of.this feature.
i NRC Studies (Sandia), D. Okrent work, Zion-Indian Available Information:
_ Point and TVA studies all include 'nformation relevant The scope of the task is to define the Recommendec Scoce of Activities _:
range of applicability of vented containment systems and mair.tain aw of alternative pressure reduction systems.
- a. Range of Applicability Define the probability of need anc types of events fcr SWR plants fo Define the which a venting system is a credicie mitigatirg system.
gross requirements fer a system in terms of siz',ng.
,. _., - - , __ .- _ _. . . _ _ -. ~
Establish the major design parameters and systen design (without developing fine detail on design--si:es of filter beds are not required).
Define the operational npects of the system with particular attention to alternative valve / control arrangements for containment penetratien.
Evaluation of the benefits and hazards including probability of successful and spurious operations. thfine in conjunction with Task 14 telow the risk benefits (or lack thereof).
Budget / Schedule: This activity should be initiated later in the program unless NRC activities dictate thct useful results would accrue by earlier performance.
The estimated resource for this is 20 MM. .
- 13. CORE LADLE Relationshio to Objective: One mitigating feature currently being pursued It is necessary to identify the advantages and by NRC is the core ladle.
disadvantages, real contributions to risk reduction (positive, negative, neutral) and impacts of addition of this feature.
NRC/Sandia Studies and industry efforts (Zion-Available Information:
Indian Point. Floating Nuclear Platform) plus significant National Lab and foreign studies ali include material related to core ladle design require-ments, etc.
Recommended Scoce of Activities: An evaluation of the real impacts of retrofitting cor.bined with assessments in conjunction with Item 8 that cooling inherent y provided by water ioss is more effective is recommended.
Budge t/ Schedule _:
This effort should not be initiated immediately unless NRC activities prov' ice another rationale for doing werk early.
The estimated rescurce for this activity is 3 MM.
- 14. RISK REDUCTIONS ACHIEVED Relationshio to Objective: There are two purposes: First, highlight that actions taken and planned have reduced the likelihood of core
- degradation, and second, perform risk evaluations of the benefits if any, of alternative features either singularly or in ccmbination.
i Available Information: On-going PRA and industry degraded core studies ano NRC studies should provide basic infornation for this effort.
Recommended Scope of Activities: Provide the capability to baseline a limited number (2-4) of plants using detailed PRA studies (e.g., Zicn-Indian a
Point, NSAC/ Duke, Limerick) and do risk tradeoff evaluations of alternative preventive or mitigative features and risk sensitivities of key phenorreno-logical issues (e.g., H2 burn, steam pressure). The assessments must include consideration in detail of new risks associated with adoitional features.
Budcet/ Schedule: Performance of the task requires baseline PPA and input information related to benefits / disadvantages of alternative features or phenomena from other tasks. It is estimated that the task could be perfomed in 6 months, and that 14 MM of effort would be required.
- 15. MODEL DEFINITION AND ANALYSIS Relationship to Objective: An integrated analysis of the transients for degraded core consideratiens incorporating the results of the chenomeno--
i logical model definition tasks is necessary. This analysis provides the capability to compare the results of the costalatad events age. inst th'e
- entainment capability.
Available Information: Results from on-going stucies (NRC and industry) and models (MARCH / CORRAL, EPRI/NSAC TMI Heatup Code, etc.) provice the basis for tnis ef' art.
-- . - ~ . -. -- . -
1
- Reccerended Sc0ce of Activities
- The sccpe cf this task is to provice the integrated analyses of tne dominant sequences for representative
{ plants and integrate the mccels cevelcped in the previous tasks into this integrated analysis. There are five tasks defined belcw.
It has been assumed that the approach will be the mcdification of the MARCH / CORRAL system augtrented by the E?RI/NSAC TMI Heatup Code. This assumotion results from the facts that MARCH /CORPAL is i:rrediately and I widely available, provides capability for effective sensitivity analyses if prcperly " calibrated", and will be used by NRC and must therefore be understccd in detail by industry.
(1. ) Cefine MARCH /CORPAL Use Convene perscnnel experienced Qith MARCH /CORPAL application and degraded core analyses to the minimum mandatory a.cdifications for MARCH / CORRAL prior to use, plans for baselining MARCH / CORRAL for industry use, plans for integrating phenomenological model development
! into analyses and identify the desirability and directions for major upgrade of MARCH / CORRAL.
L I
I (2.) Centainment Analyses Perform analyses for representative containment / system types for l
dominant accident sequences and necessary variants.
l (3.) MARCH /CORPAL Improvements Cefine program for major development of PARCH / CORRAL model-improve-ments and implement if desired.
(4.) Integrate Phenomenclogy Mode!s into Analyses
- nclude the results.of the phencmenological develcpment activities into the integrated transient anlaysis.
(5.) E?RI/NSAC TMI Code Qualify and document the PWR damage progression .: ode. Cevelop,
_ qualify and dccument the BWR camage pr gression equivalent code.
l L'
Sudget/ Schedule: The resources estimated for these activities are:
- a. 5 MM centributory by interested parties
- b. 24 MM and 100 CRU per plant type assuming results frem on-going studies are applicable, assume three more types for a total of 72 MM and 300 CRU.
- c. Major upgrade program would be 60-100 t@t and 300 CRU. Should be undertaken only if directions indicate a real need for support of rulemaking in the March / April time frame.
- d. 10 MM 20 CRU
- e. 12 MM 30 CRU e
l l
l I
1
0W TASK RESOURCES E
MM CRU K$ K5
- 1. 2 16 13 4 105
- 2. (1.)
146 (2.) 18 6 48 (3.) 6
- 3. 11 88 40 184 4 (1.) 18 75 267 (2./ 24 10 20 86 (3.)
S. 15 20 126 (1. )
20 246 (2.) 30 64 (3.) 8 24
- 6. (1.) '
3 96 (2.) 12 24 (3.) 3 7, 24 10 195 50 100 430
- 8. (1.)
60 50 100 595 (2.)
144 (3.) 18
- 9. 2 16 (1. )
20 182 (2.) 22
- 10. 3 24 11.
- 12. 2" ;60
- 13. 8 64 14 14 20 lit
~~
hd/I TASK RESCURCES E
MM CRU KS KS
- 15. (1. )
300 666 (2.) 72 (3.) --
10 20 86 (4.)
30 105 (5.) 12 474 4305 IDENTIFIED CONTINGENCY . 540 4845 5571 CONTINGENCY (15%)
~
6686 1115 PROJECT MAttAGEMErli (20%)
i 1 -
l l
i
Revision 1 AFFENDIX A-2 November 10, 1980 EFRI PROGRAM - TECHNICAL DETAILS DRAPT FROGRAM FIRI Hydrogen Combustion and Management Studies L. Thompson 1.0 Introduction Hydrogen generation during i severe accident and its subsequent
- postulated accident scenarios management pose many difficult questiors.
and complex LWR geometries can result in a wide range of situations, some of which would threaten the containment barrier if a deflagration or Combustion properties for hydrogen-air-steam mix-detonation is initiated.
tures in large scale with turbulence are not well kncwnl and manageaent systems must accommodate the hydrogen that is characteristic of both large and small break accidents, in atmospheres of various steam, gas and aerosol concentrations, at various pressures, and with the likelihood of substantial e
stratification and pocketing. .
Alltechnicalissuesrecahdinohydrocen 1.1 Objectives and Technical Issues _.
comt.stinn cannot ba explored in dapth in a reesonabic time frame, nor wnuld.
it be profitable to dn so. This program will intend, rather, to meet the following limited objectives:
- 1. Determination of whether and when hydrocen can burn in various LWR accident environments resulting from ' Class 9' scenarios;
- 2. Damonstration that if a hydrogen bura does occur its effects will not exceed the realistic survival capabilities of equipment and containment; and
- 3. Demonstration that reasor.able control methoo's can provide adequate safety margins assuring the intecrity of the containment 25d of key safety-related scuipment.
Determination of the containmer.t 2nd ecuip'ent capacity to surv4ve potential threats cue tc hydrogen conbustion reauires investication of several questions:
- 3. Experiments on hydrogen control methods includino water spray and fog (Acurex); ,
4 Measurement and analyses of hydrogen mixing and distribution with i
natural and forced convection (HEDL-W); and
- 5. Demnnstration of hydrogen combustion and management methods on a large scale turbulence (Nevada Test sitel.
Table I provides a capsule description of each program. Ficure I shows ealistic time scalas for the projects, including the test nhase (solid line).
- 2. Relationshio of Procram Elements to Technical Issues. Ner.e of the questions a-d above can be answered satisfactorily in any one facility due to questions of scaling or practicality. The need for near-tenn result in several areas also necessitates parallel efforts which employ the best features of each facility. Figure 2 illustrates the proposed use of facilities to answer i
the iss"es. Tna issues are briefly discussed below, and Tables II-VI expand on Figure 2 and describe how the various facilities can contribute in each case.
2.1 Lower Flam1 ability Limits. The generally accepted lower flammability limit (LFL) of 4". hydrogen for uoward propagation was derived from small I
scale epariments in air (1-3) . The questions now concern the effect of vessel size ana shapa, igniter tyne, icniter location, turbulence, and ctaam (up to high concentrations.
In addition the use of water scravs, fcgs, or other mitigation methods will affact the LFL at least for some conditions of flow rate and drop sizes and should be evaluated. Table II indicates the facilities which would be l
l invcived in the EPRI program.
2.2 Character nf Daflacrations. The nature cf datlagrations in LWR crvironments is infiaenced oy many parameters. anc careful selection is i _ .-- , _.. _ -- ,-
necessary to avoid an overwhelmino matrix of cases for exparimentation.
For hydronen concentrations above 10%,cc=bustion is essentially comnlete, and the burning rate in various environment,s and for various scales is of most interest. The transient pressure in the volume is related to the rate of deflagration which may be characterized by a burning velocity.
The maximum burning velocity fnr hydrngen in air is found to be about 3,5 m/second in well-mixed quiescent atmospheres ir, small volumesU'N and it is known that diluents such as steam lower this value '}
Questions involve the effects of hydrogen oncentration, turbulence, steam, initial tem;:erature, pocketing or nonhomogeneity. and v.ater sprays fog and other mitigation approaches. Table III indicates the potential research activities 2.3 Hydronen Mixing and Distribution, The procable location and distributinn of hydrocen in containnent followino a degraded core accident remains one of the most diffiruit questions. Data is needed for a variety of conditions so that computer codes which' deal with natural and forced convection can be im-proved or validated. Quasistatic diffusion-experiments have been parfonned, notably at Battelle-Frankfurt.( Battelle found that a temperature dif ferance of lese than 20 degrees F between upper and' lower compartments of a 2500 ft 3 vnlume resulted in a significant segration of hydrocen. The lower comoar*. ment, occupying t vo-thirds of the voluma and separated frnm the upper by an orifi e of 10 f t2 (1,,100 of the area), reached a hydrocen concentration of 4% while j the upper coupartment saw only 1%. Experiments with a virtually homngeneous tamparatura resulted in unifort concentrations, r.nd that result is confirmed 9,0).
by calculation Tha current ouestions relate to forced circulation and the dynamic ef fects of hydrogan ja;s. Water sprays. and Circulation fans in Complex genmetri es, in addition to the effects of stea : and imposed thernal gradients.
Se of a c^mpartmentalized volume which cenerically simulates a licht water A
~
- a. What are the lower flammability limits in LWR accident conditions and how effective are various ignition sources;
- b. What is tha character of deflagrations in various LWR 9eometries and how can the effects be mitigated;
- c. What is the nature of hydrocen mixing and distribution in large compartmentalized volumes with natural and forced convetion; and
- d. What is the potential for the acceleration of deflagrations, or for
" transition to detonation" in turbulent mixtures, and how can the effects of such explosiens be mitigated.
l .
Two additional researcn needs are implicit: {1) The development of predictive capabilitias tn allow extrapolation of test results to other geometries, scales, and environments; and (2) The assessment of hydrogen burn effects on safety-related equipment. ,
A very large data base does exist for combustion and for hydrogen in particular. That data base provides a starting coint for investication of the environments and geometries which are peculiar to LWR safety. The role of turbulence and dynamic phenomena on combustion durina accident conditions is not well known, for example, and new data are needed to meet the ob.iectives stated above.
I 1.2 Procram Elements. Several projects are proposed which would provide the information needed to satisfy the program objectives. The projects are relatea, and consist of:
- 1. Development and preliminary testing of deliberate ignition l
systems (Rocketdyne Division of Rcc'<well);
- 2. Experiments and analyses on casic hvorogen combustion phencmena including the effs:t; of steam, turtu'.ence, and the potential for transiticn t] detonation ( AECL ',-lhitesneli);
i l
reactor would provide a helpful damonstration. Table IV indicates the facilities which could contribute in this area.
2.4 Transition to Detonation. It is well known that detonations are easier to oroduce in " shock" tubes or small volumes than in a large space. The classic " detonation limits" indicated by Shapirn and Moffette ) are vary uncartain. Hydronen/ air / steam conditions which fall within the detonation region may very well rasalt in ordinary deflagrations, particularly if ignition is bv a nnn-axplosive trioger in an onen volume U2-D) . Turbu-1erce pecmotars such as a grid system (or stacked floor gratings), will accelarate a burn. Nevertheless it is ex; ected that the most vulnerable regions will he in local structures such as protrusions from a lar:;er volume.
Structures and equipment may also have a substantial capacity to survive a detonation since the pressure and temperatore very quickly decays to deflag-ration levels, and hydrogen control means such as water sprays may sufficiently mitigate the phenomena. Table V indicates the research fr.cilities which could stt.dy the potential for transition to detonation.
2.5 Effects of Burn on Safety-Related Ecuioment. The surviveability of safety equipment during a hydrogen burn is a serious question. The rapid decay of temperature and pressures plus the therinal capacity of much equipment creates a potentially favorable situation. Secondary fires initiated by a hydrogen flame front may be of greater danger. Pressure damage will cacend on how well the eq.sipmant can ")raathe". Safetv-related materials and equipment can be placed in volumas tn be used in combustion tests to help assess su rv-:vaaot ii ty. Table VT indica es the facilities that could provide ecuipment qualification results.
- .. .. -. . _ - = - _ . _ _ _ _ -_ _ .- ._ -_. - ..
1 3.0 Descriotion of procram Elements.
i j Following is an expanded description of each of the five subprograns. ;
The facilities and capabilities of each site are described in Appendices A-E.
3.1 Icniter Cevelopment (Rockwell/Rocketfyne). The task plan preparation is now underway, and involves establishment of requirements and combustion characteristics ,for various igniter types, including hot surface, Spark, and ccmbustion wave types. The testing system, igniter design, and experiment ,
matrix will be defined in the initial project phase. Inniter and system c
j fabrication, testing and evaluatien will follow, with the emphasis cr. scocing
- the comparative effectiveness of the various igniter types in steam and water spray environments. -
l 3.2 Combustion Studies (WMteshe'l),. A four-tronth period of tests will becin by April 1.1981 to answer basic questiens of combustion in a hydrogen / air / steam
[
atmosphere. An 8-foot diameter sphere will be used for most of those tests,
~
I and a 5-foot diameter by 19-foot high cylinder is also available. The design
- j. pressure of 1450 psi will allow the occurrence of detonations, ,1though none i
are expected.
Tests are being defined to study lower flamability limits in steam, I laminar spherical deflagrations, and the effects of turbulence on deflagrations.
i
- In addition special tests such as ignition in one of two connected volumes l
will be performed. It is expected that about 50 tests can be performed in the i four month peric , with a hich degree of flexibility. The test environment during this pt-riod will include the widest range of hydrogen / air / steam mixtu'res, bat will not include water spray or other mitigation measures.
3.2.1 Lower Flarnability Limits and Extent of Reaction _. At concentrations
- r. ear tr.e LFL, i.e. less than approximately 10*; H2 , the combustion reaction is not cceplete. Thesa experiments can determine whether size and snace of tne i
i
, = _ . __. . -. - . ..
i
) vessel affects the extent of reaction by comparing the results with those f
obtained previously at Whiteshell in a two-litre cylindrical vessel.
In these experiments, uniform hydrogen / air / steam mixtures will be spark-ignited at the bottom of the spherical vessel. By analysing the mixture before and after the experiment, using cas chromatography, the 1
extent of reaction will be determir.ed. Transient pressure and temperature measurements will be made and ioni:ation probes will be used to detect flame -
speeds. Significant differences in the extent of reaction between the bench-scale cylinder and the eight-foot sphere may warrant subsequent experi-ments in the large cylinder. The flammability limits and extent of reaction depend on the location of the ignition source, and some experiments will be performec with central and top ignition which are known to be less effective in producing a reactien.
3.2.2 1.aminar Scherical Osflacrations. At hydrogen :oncentratiens greater than 10%, complete combustion is expected. Burning rates are import:nt for deterTnining possible b!ast effects at high flame speeds and for estimatino the tirre during combustion that heat transfer can occur to reduce maximum pressures
- and temperatures. A correlation for laminar burning velocity as a function of nydrogen concentration and temperature has already been developed at Whiteshell based upon their bench scale experiments. This correlation allcws a prediction of the pressure transient resulting from a laminzr deflagration, and it is the intent of these experiments to validate those calculations.
Central i t. %n of uniform hydrogen / air / steam mixtures in the eight foot i
sphere will be r 4d for hydrogen concentraticns in the range of 10 to 45%.
! tiaximum turning velocities and the fastest deflagration transients are expected l
l at 42'. hydrogen. Detonations are not necessarily expectec in this inter-mediate scale volume with a spark ignition source. High speeo pressure and te oerature transducers will record the transients and ionizatien probes vill i
detect flame arrival.
7
.- ~ . __ -.
3.2.3 Effect of Turbulence and Structures on Scherical Deflagrations.
Since turbulence can significantly accelerate the combustion rate, experi-ments are proposed to examine this effect, somewhat qualitatively at this point. 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 utilize: (1) a fan to produce convection flows prior to contral ignition of uniform hydrogen / air / mixtures; and (2) various structures or obstacles to determine their effect. The experiments would be performed in a manner similar to those described oreviously.
3.2.t Soecial Tests. The Whiteshell high pressure schere, pipe and ,
cylinder can be combined in various configurations, which allows for several interesting possibilities. Unequal concentrations of hydrocen in different volumes can be separated by a weak diaphram, with ignitien in one cf the volumes. A 20-foot long i foot diareter pipe may also be connected to the sphere to evaluate the potential for local detonations l
in protrusions from larger volumes.
I 3.3 Control Studies (Acurex). The Acurex test vessel would be used for scoping mitigation phenomena such as the effects of water spray, fogs, and halon which will not be investigated in the near-term at Whiteshell. A bunkered data acquisition system is available, and remote operation from within the bunker will allow rapid turnaround between tests. Igniters developed and initially evaluated at Rockwell would be tested here in a larger volume with higher hydrogen concentrations.
3.t Hyd ogen Mixing and Distribution Studies (HEDL-W). Large scale near-term hydrogen mixing and distribution tests would be performed in the HEDL Contain-ment Syctems Test Facility (CSTF) to investigate aspects of hydrogen mixing, stratifica-ion anc local accumulatior.. Efforts are expected to include l
Q
. . . - - . - , , , , - . - . - --- . - , - ,- - , - . -- _ _ _ . . .- . , . . . . . - . , . , , ~ , - _ ~ , -.
E i
3 mixing in the large open volume (30,000 ft ) for baseline data, minimal compartmentalization to validate computer codes, and simplified configurations representative of LWR plants. Tests would be performed with and without containment sprays and steam, and would consider hydrogen mixing by both natural and forced convection. !!easurement would be made of temperature, hydrogen concentrations, water / vapor concentrations, and convective gas flow patterns. The test results would be compared to pre- and post-test cor.puter code analyses in an effort to validate and improve existing codes.
Compartments may be built outside of the CSTF and taken in through the large existing vessel door. Testina in the near tern as planned will recuire use of only 4 volume percent hydr: gen, however. Use of combustible mixtures would necessitate extensive safety reviews since the vessel is located in a building which houses other experiments. Tables Vil and VIII outline the potential tests separated into natural and forced convection experirent 1
series.
3.5 Larce Scale Deflagration Tests _. The Nevada test planning will incorporate results of the igniter development, combustion, control and distribution studies. The Nevada tests should demonstrate that the lessons learned at
/
small scale apply to much larger scale, and that expected wide spread' turbulence and nca-homogeneity in an accident environment contribute no
" surprises." Commercial-design containment sprays will be used, and a test matrix will be performed to verify deflagration limits and the effects of igniter location (and type), hydrogen concentration, and structures such as grids or obstacles. The effects of deflagrations on safety-related equip-ment ca. a!so be studied.
. - - , , ~ , - , , , - . , , , -
4.0 Estimated Procram Costs.
Each of the programs outlined is intended to be flexible in terms of experime. ital activity, and costs can be adjusted accordingly. Table IX indicates the best estimates for the time periods shown in Figure 1.
w 9
10
REFERENCES
- 1. H. F. Coward and G. W. Jones, Limits of Flammability of Gases and Vacers, Bulletin 503, Bureau of Mines, U.S. Department of the Interior (1952).
- 2. ft. G. Zabetakis, Flammability Characteristics of Combustible Gases and Vacers, Bulletin 627, Bureau of Mines, U.S. Department of the Interior (1965).
- 3. B.C. Slifer and T.G. Peterson, " Hydrogen Flamability and Burning Characteristic in SWR Containments," NEDO-10812, 73NED49, General Electric (April, 1973).
4 A.L. Furno, E.B. Cook, J.M. Kuchta and D.S. Surgess, "Some Observations on Near-Limit Flames," 13 Sym. on Comb., (Pittsburg, Comb. Inst., 593-599, 1971).
- 5. D.D.S. L1u, et.al. Canadian Hydrocen Combustion Studies Related to huclear Reactor Safety nssessment, nr.u.-ors , p.o ce puoilsneo),
- 6. J. Warnatz, " Calculation of the Structure of Laminar Flat Flames II:
Flame Velecity and Structure of Freely Propagating Hydrocen-Oxygen and Hydrogen-Air Flames," 3er Bunsenges Phys Chem, (82:643-649, 1978).
- 7. D.K. Kuehl, " Effects of Water on the Burning Velocity of dydrogen-Air Flames," ARS, (32:1724-1726, 1962).
- 8. G. Dixon-Lewis and A. Williams, " Effects of Nitrogen, Excess Hydrocen and Water Additions on Hydrogen.-Air Flames," AIAA J (1,2416-2417,1963).
- 9. H.L. Jahn and G. Langer, Distribution of Hydrogen Released within Comoartmented Containment in Consecuence of a LOCA - Analysis and Verification, Battelle-Institut, Frankfurt; paper presented at NRC Seventt Water Reactor Safety Research Information Meeting, Gaithersburg, Md. (November 1979).
- 10. G.J.E. Willcult, Jr. , R.G. Gido, and A. Koestel, Hydrogen Mixing in a Closed Containment Compartment based on a One-Dimensional Model with convective Effects, NUREG/CR-1575, LA-8429--MS (September 1980).
- 11. Z.M. Shapiro and T.R. Moffette, Hydrogen Flammability Data and Acoli-cation to PWR Loss-of-Coolant Accident, WAPD-SC-545, Bettis Plant (September 1957).
- 12. L.H. Cassutt, F.E. Maddocks, ano W. A. Sawyer, A Study of the Hazards in Storage and Handling of '.iouid hydrocen, Arthur D. Little, Inc. , AD ov/ cs , uncatec.
11
i
- i ll REFERENCES (cont.)
! 13. M.G. Zabetakis, A.L. Furno and H.E. Perlee, Hazards in 'Jsino Licuid
, Hydrocen in Bubble Chambers Bareau of Mines, Report of Investigations
! 6309, 1963.
14- B. Lewis and G. von Elbe, Corbustion. Flames and Exolosions of Gases, 2nd. Ed. (New York: Academic Press, 1961).
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TABLE I Options in Hydrogen Combustion & Manager.ent Pr gram
- 1. Igniter Development (Rockwell)
Evaluation of techniques for ignition of combustible gases, including advanced niethods developed for the U.S. space program. Goal is to obtain methods for re-liable ignition cf fuel-lean mixtures in atmospheres cf hydrogen, air, and steam.
- 2. HydrogenCombustionStudies(Whiteshell)
Basic studies of hydrogen combustion properties in a high pressure sphere and cylinder which 'can be connected by a variable length pipe. Associated modeling of burning velocities and gas dynamics, and small-scale model development tests.
- 3. Hydrogen Control Studies (Acurex)
Near-tenn exploration of various hydrogen managemlnt methods. Use of test site near EPRI and a surplus high pressure vessel with existing protected data aquisi-tion system.
4 Hydrogen Distribution _ and Mixing Studie's (HEDL)
A large cylindrical vessel with and without compartments, with various thermal gradients, atmosphere compositions, hydregen injection rates, and use of forced convection generated by water sprays and tans.
- 5. Large Scale Deflaoration Studies (Nevada)
Study of hydrogen deflagrations, and demonstration of management methods in a very large sphere, with and without compartments and water sprays, and with use of various ignition methods and locations, temperature gradients, and flame suppressants or water fogs. Demonstration that the small-scale database is applicable to "real" LWR accident conditions.
i
TABLE II Lower Flammability Limits II)
Facility Parameter Rockwell Whiteshell Acurex Nevada 3
volume (ft ) 100 300 300 75,000 Igniter Type Yes No Yes Selective Igniter Location No Some Some Yes Steam Yes Yes Yes Yes Turbulence Yes Yes Yes Yes Non Uniformity No Yes Yes Yes Water Spray Yes -
No Yes .Yes Halon No No Yes ?
Key Measurements P,T, Conc. Yes Yes Yes Yes Ion Probe No Yes Yes Yes I
Approx. No. Tests -
100 20 10 5 II)Underiined items indicate key sites for investigation.
O I
1 1A l
TABLE III Deflagrations (I)
Facility Parameters Whiteshell Acruex Nevada 3
Volume (ft) 300 300 75,000 Hydrogen Concent. Yes Yes Yes Steam Concent. Yes Yes Yes Initial P and T Yes Yes Yes Turbulence Yes Yes Yes Pocketing Yes Yes Yes Water Spray No Yes Yes Water Fog No Yes ?
Halon No . Yes ?
Structure Effects Yes Yes Yes Key Measurements -
P T. Conc., Ion Yes l;
Yes Yes Approx. No. Tests 30 15 '. 5 l
1 II) Combustion tests with hydrogen concentrations generally greater than 10"..~ Underlined items indicate key sites for investigation.
l l
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TABLE IV Hydrogen Mixing and Distribution (I)
Facility HEDL I2I Nevada (3) f I Whiteshell Parameter 67 (Vertical) 52 (Diameter)
(
I Characteristic Length (ft) 19 (Vertical) 50 (Horiz. Tube) 30,000 75,000 400 Volume (ft. ) I4) Yes(5) 7 Yes _
Compartments Yes_ Yes Yes Temperature Gradients Yes Yes Yes Steam - Yes_ Yes No Water Sprays Yes No Yes Hydrogen Jets Key Measurements: Yes Yes Yes T, Concentration ' Yes No No Gas Velocity 20 5 l 20 f Approx. No. Tests II) Underlined items indicate key sites for investigation.
I2) Limited to maximum of 4% hydrogen '
(3) Distribution data obtained in conjunction with combustion tests.
I4I Compartment data can be obtained when sphere and cylinder are connect f
(5) Generic simulation of LWR possible.
e a y-
i TABLE V Transition to Detonation (TTD)(I}
Facility Parameter Whiteshell Acurex Nevada (2)
Geometry Cyl., Sphere, Tube Cylinder Sphere I 75,000 Volume (ft 300 300 Steam Yes Yes Yes Water Spray No Yes Yes Water Fog No Yes ?
Halon No Yes ?
Ignition in
' Compartments' Yes I) Yes I4) ?
Structure Effects Yes Yes Yes Simultaneous Ignition Yes Yes ?
Ignition Power No Yes No
)
Key Measurements l P, T, Conc., Ion Yes Yes Yes Shadowgraph, Schlieren Future Possible No Approx. No. Tests 10 10 ?(2) j (I) Underlined items indicate key sites for investigation. ,
(2) Demonstration tests using mixtures approaching the detonation region may be conducted if, intermediate scale tests indicate TTD is very unlikely.
(3) Ignition in tuae connected to large volume.
I') Ignition in balloon or small compartment.
f
TABLE VI Effects on Equipment (I)
Facility Acurex Nevada WhitesF-Parameters 300 75,000 3 300 Volume (ft ) Yes Yes Possibly Deflagration No Possibly Yes Detonation Yes Yes No Water Spray ?
No Yes Water Fog ?
No Yes I Halon 10
?
10 Approx. No. Tests IIIUnderlined items indicate key sites for investigation.
-w
TABLE VII Hydrogen Mixing by Natural Convection PURPOSE: The purpose of these experiments is to quantify the degree to which hydrogen mixes with the containcent atmosphere when mixing is induced only_by natural convection processes.
INFORMATION TO BE OBTAINED: These tests will measure the concentrations of hydrogen at strategic spatial locations as functions of time. This information will be analyzed in terms of a natural convection computer code which will allow the determination of turbulent diffusivities.
FACILITY REQUIREMENTS: These tests will employ low hydrogen concentrations (0-4;) and could best be done in the CSTF vessel at HEDL.
DESCRIPTION OF TEST SERIES: The mixing of hydrogen, introduced through porous plates at low velocity, would be measured under various thermal gradients.
Saturatec steam-air mixtures at various temperatures would be established, and then hydrogen would be introduced. Parameters would include atrosphere temperature, composition and temperature of hydrogen gases introduced, and duration of the injection period. The use of compartments and generic LWR structures would be planned.
e e
21
TABLE VIII Hydrogen Mixing Augmented by Forced Convection (HEDL) eg PURPOSE: These tests will quantify the degree of hydrogen mixing phich res'ults when forced convection processes are present. Realistically, hydrogen will likely enter the containment atrosphere as a jet, sprays may operate or ventilation fans may operate. All of these processes augment hydrogen mixing and need to be accounted for.
INFORMATION TO BE OBTAINED: Hydrogen concentrations at various spatial locations will be measured as a function of time. Also gas velocities and directions will be measured at a few key locations. These data will be used to prove containment mixing codes, providing turbulent dif fusivities and
~
forced convection flow quantities.
FACILITY REOUIREMENTS: These tests could best be done in the CSTF vessel at HEDL.
DESCRIPTION OF TEST SERIES: These tests are ouite similar to those of the p evious series except that various mixing promoters would be operated. Several tests would be required to study the effect of mixing when H2 was introduced as a circular jet. At least two tests would use containment sprays, one at ambient temperature anc or.e at an elevated temperature. The use of com-partments and generic LWR structures would be planned.
4 e
22
APPENDIX A-3 HALON STUDY - TECHNICAL DETAILS II. TECHNICAL BACKGP.0UND Eefore describing a Halon system we should give the basis for our opinion, mentioned earlier, that a 1301 system miaht be suitable for an ice condenser containment. It is based on the following simplified estimates: the total containment volume is taken as approximately 1.2 x 3
106 fg which includes upper and lower compartments and ice condenser plenu: and bed volume. We further assume approximately 1,200 lb mass of hydrogen to be produced, which by itself is equivalent to roughly 3 psi in the total containment volume. Based on results in the report
- cited belcw, it is estimated that about 175,000 lb mass of Halon would be required to inert the containment for these conditions. This ir a uivalent to approximately 6 psi of Halon, which now produces a total contein.r ent pressure of 9 psig and is less than desicn. However. we emchasis that these rough estimates a.'e only meant to show first-cut feasibility of the concept. Note also tnat the heat to vaporize the total Halen inventory would ba 6.2 x 106BTU which is small compared with the blow-down energy or the heat of fusion of the total ice inventory.
Any water-cocled nuclear reactor in which a LOCA occurs can produce hydrogen gas by reaction of H2O with zirconium and by radio 1ysis of cooling water by oecay products. Explosive mixtures of hydrogen with the air of the containment c6a form. There are a number of possible means of providing protectiot, and the method to be described here involves
'i nerting the containme t with a gas known as Halon 1301, which chemical.ly is trifluorobromometha le, CF 3 Br. Atlantic Research arporation over a period of nearly three < ears conducted a study of the use of Halen 1301 in the reactor containment for nuclear powered ships, under sponsorship of the Maritime Administration of the Department of Commerce ("Hydrocen Suppression Study and Testing of Halon 1301", by Edward T. McHale, Contract Nos. MA-6562, and T-38619, December 1976 and March 1978). Copies of these reports are being submitted with this proposal. In the er e of the maritime reactor, a Halon system was found to be completely suita le and would have been the system of choice had such reactors been built.
Much of tne following information is drawn from the above-listed recorts.
II - 2 s
l t
The'suppresion system would consist of a predetermined quantity of Halon 1301 stored as a liquified gas in several storace vessels near the containment. In the event of a LOCA, if the hydrogen concentration reached some precetermined level, the 1301 would be discharced either aut'omatically or manually into the contv nment through a piping and valve system. tiany operational advantages are associated with the simolicity of a 1301 system.
For e'xample, there are few moving parts, minimal power requirements, high reliability, relative economy, storage convenience, ease of periodic testina, and once a'ctivated the system requires little further attention.
I When Halon is mixed at the proper concentration with hydrogen / air or oxygen enriched air, it will render such mixtures completely nonflamable.
Other gases such as nit" ogen and carbon dioxide produce the same effect, although such large quantities of these compounds are required that the overpressure in an ice condenser containment (or probably any containment) would exceed design or even ultimate rating. The amount of Halon required g
for a given volume depends on the concentration of hydrogen and air, temperature, pressure, presence of steam, losses, etc. Experimental measurements have been made at Atlantic Research to map the complete t
flammability (explosive) diagrams for H2/02/N2 mixtures containinn Halon 1301. It is virtually certain that once the hydrogen / air concentrations, etc. , are knom that the required amount of Halon could be specified with no further testing.
I A great number of physical and chemical properties of an inerting g gas must be considered before it can be selected for containment application.
These involve materials compatibility, thermal stability, long tenn storage, toxicity, vapor pressure, critical temperature, solubility in H 0, and others. Many of these are discussed in the above referenced 2
report. In general, the properties of Halon 1301 are very favorable for containment use. There are, however, sore questions concerning its I
radiolytic stability in water and the effecc of decomposition products I
(if any) on metals. Thu:e will be specifically addressed in the present i
! study. In addition to the at,ove properties, the availability of Halon i must be considered. It is presently marketed by DuPont under the tracename Freon 1301as a fire and explosion suppression acent, and its availability is not expected to be a proble.n.
II 3 l
There are certain questions about Halon behavior which are unique to a containment application. Scme of these have been examined in our previous study and will be mentioned. One question that arose concerned the effectiveness of charcoal filters, through which the containment atmosphere is passed when being purged,'to absorb iodine and methyl iodide radioactive fission products in the presence of Halon. Tests showed i
that air or H / air mixtures containing Halon would pass through the 2
charcoal with no absorption of the Halon but with complete absorption of i the iodine materials. It was also possible to show analytically that Halon and iodine compounds would not react with each other. Thus Halon mixtures, either following a LOCA, or in the event of accidental discharge, could be safely vented through a charcoal filter system.
Extensive studies were also conducted on the radiolytic ste.bility of Halon in the radiation field of the containment. It was shown that in the containment volume proper, negligible radiolytic decomposition would occur.
}
It was found, however, that if Halon could find a way to become exposed to the cooling water and to dissolve in it'(solubility in the rance of 0
100 ppm at 120 F and decreases with increasing temperature), the core radiation could decompose a small amount of the Halon. This. loss should
' be allowed for during system design. In the case of the ice condenser containment, the small amount of decomposition may yield sufficient halide compounds disWed in water to produce a deleterious effect (from a long range or recoverable point of view) on materials in the primary system. This is a key problem which will be carefully examined in the l-l proposed study. It should also be mentioned that should this prove to be a problem there are means available to overcome it. For example, the decomposition reaction is self-arresting and there are additives which can bring about this arresting effect and retard any decomposition.
The foregoing discussion is meant to provide an indication of what l
a Halon inerting system would involve and of some questions (many of which have been answered) that can be raised about its operational features.
Before ending this secti,on it #5 desirable to outline in broad form what is requireo to be done to d;etermine if such a system ca: be applied to an ice condenser containmen't. "ery soon after a system study is initiated, 11-4
technical personnel from Atlantic Research would visit a nuclear plant for a complete inspecticn and a briefing of all aspects of the reactor system and containment that are relevant to Halon application. Folicwina this visit a preliminary working design of a Halon system would be devised.
This would include full specifications of worst-case amount of hydrogen expected and amount of 1301 required for inertine (considerina that required for safety margin and make-up for all losses - long-term leakage, raciolysis,dissolutico,etc.) Pressure-temperature-time histories would be plotted using the COGAP and ARC computer codes. TF'se codes would also yield the required rate of Halon injection to stay ahead of H2 build-up.
Simultaneous with the system specification study we would begin to examine tne potential prcblems that could initially be identified. These involve as a minimum Halon decomposition, water chemistry and materiais compatibility with decomposition products. One question that had been raised concerned the ignition of inerted hydrogen mixtures using a shock wave initiation source. For example, if a pocket of Hp/ air formed in an inaccessible section of the lower compartment and did not get inerted by Halon, whac effect would it produce on the inerted containment mixture if it become ignited and sent out a blast wave. These and other questions will be addressed by literature search and analytical study using experts in each particular subject area.
i k
.i
III. PROPOSED WORK
- 1) A preliminary system design will be made which, while it will represent a working model, will nevertheless be complete. It will specify Halen quantity required, rate of discharge, H2 build-up rate, pressure-time and temperature-time hi.. aries, Halon losses from all known sources (leakage, radioysis, dissolution), contribution by Halon to bicwdown energy removal, etc.
(ARC and COGAP codes to be used.) The Halon
' hardware system will be specified to the extent of storape tanks sizing and number for redundancy, spray system configuration for thorough mixing and discharge rate, and distribution analysis of Halen throughout upper and Icwer compartments.
Between two and four technical cersonnel will visit a nuclear clant with an ice condenser containment for one or two days of discussions early in the program.
- 2) The present flammability diagrams for H2/02/N2mixtures containina Halon were mapped using the " strongest credible" ignition source which was represented by a squib igniter. It has been postulated that hydrogen might pocket somewhere in the lower comoartment, not get properly inerted, and then ignite and p.oduce a blast. Therefore, we will inv'estigate by literature searcr. an'd ccmbustien analysis if it is known whether otherwise inert mixtures can be initiated with a blast wave. The question to be answered here is not whether mixtures can be inerted against shock wave initiation but rather how much extra, if any,1301 agen' .1uld be required.
I In this task, as in others requiring literature search, we will use our own background knowledge of sources ploi the Atlantic Research DIALOG computer search facility which has the capability of examining numerous sources of tecnnical literature.
- 3) The amount of Halen deccmposition that will occur in the ice condenser containment due to dissolution in H2 O and radiolysis from the core will be computed. This is obtained by calculating the total decay energy from which is obtained the accumulated radiation dose per NRC guidelines.
Then knowing Halon partial pressure.G-value,and deccmposition rate functional dependence the total integrated amount of deccmposition can be comouted.
- f. ) Stucy the change in water chemistry due to Halon decemoosition and III-5
)
its effect, if any, on materials of construction in thw primary system.
Examine in detail methods of inhibiting decomposition by additives if necessary and the effects of additives on water chemistry and their materials compatibility.
Corrosion and degradation of properties of metals in the primary sysMm will be the main concern.
Literature searches will be conducted to determine if changes in such properties as tensile strength ,
1 elongation, elastic modulus, etc., have been studied when metals are exposed to low concentrations of halides in water at elevated temperature
( and pressure.
5)
The above list of proolems is preliminary and other items to the studied are likely to be discovered when the various topics are examined in detail.
Two technical reports will be submitted in the course of the work. At the mid-poi : of the study an interim report will be prepared outlining progrcas to catc on each topic. At the completion of the program a final svalary report will be submitted which will present complete results and their interpretation together with recormlendations. The program manager i
1 will deliver the final report to the sponsor and make an oral presentation
- or results.
l ;
l III-7 1,
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ATL ANTIC AESE AACH CCAACA ATICN 539C CHEACKEE AVENL;E ALEX t.NC91A.VIAG:NIA - 22314 7C3 642 4CCO
~v:xr*: s G ee25 November 26, 1980 Dr. Wang Lau Tennessee Valley Authority 400 Commerce Avenue Knoxville, TN 37902
Reference:
Contract TV-55205A " System Feasibility Analysis of Using Halon 1301 in an Ice Condenser Containment"
Dear Dr. Lau:
This summary letter report is being sub=itted per the contract requirement ta provide an interim report in the course of the program. Up to the present time a visit was mace to the Watts Bar plaat by five technical persons associated with the study, numerous telephone discussions h' ave beer. ? 21d with TVA, AEPSC and Duke Power personnel, and a group from Duke Power visited Atlantic Research for a review of the Halon system and our opinion about alternative approaches.
We have had requests to accelerate progress if possible, which we are trying to accommodate but, as explained, much of the work follows a sequential path and certain tasks cannot be completed until other prior work has been performed.
In broad summary, it can be reported that a Halon 1301 system is certain to be able to provide full safety against any possible hydrogen hazard following a LOCA in an ice condenser containment. The matter that remains does not concern safety acceptability, but rather concerns the question of how much corrosion might certain materials be subjected to, and will the primary and secondary systems meet
- specifications and be recoverable after a LOCA if they were exposed to Halon decom-position products.
Briefly, the corrosion problem is as follows: Halon itself is stable and inert toward materials. However, if needed following a LOCA, Halon gas could dis-solve to a.small extent in the emergency cooling water (its solubility is 150 ppm l by weight in water at 77'F and 0.5 atm). Radiolytic decomposition can then occur, the result of which could be the formation of bromides (and fluorides) in low con-centration (about 400 ppm Br-) in the water. Therefore, the ausstion being addressed is what effect such a solutien will have on reactor materials, particularly stainless steels.
If unfavo'rable answers emerge from the =aterials study, then the options are the following:
o Plan to install a Halon 1301 system to provide saf ety during th'e interim while an alternative system is being developed, using the rationale that the likelihood of '..aving to employ Halon is extremely small.
l
. Contract TV-55205A
! Interim Report Page Two e Study the effect of expocure of stainless steels to hydrogen. Since hydrogen has an embrittlieg effect on steels, it may be that hydrogen alone is deleterious enough that the reactor system could not be re-covered anyway, even if Halon were not used.
e Investigate means of elimiaating or reducing the effect of bromides.
l The general approach would be to find additives that defeat the Halon radiolytic decomposition mechanism in solution. Several candidate approaches have been considered:
- Determine if Halon decomposes it; sclution in the presence of I. hydrogen as rapidly as in its absance. Hydrogen may compete with Halon for solvated electrons, the species responsible j for initiating Halon degradation.
l - Add an additive to the water that will precipitate bromide in inert form. (A search for candidate additives will be made.)
- Add an additive to the water tha$t will produce hydroxyl radi-cals in solution. These radicals are thought to react with bromide ions to reverse the decomposition reaction. Alcohols may be good candidates.
- Determine whether decomposition of Halen will occur to the same extent over a range of pH values.
- Generally attempt to find additives that may be effective in reversing Halon degradation.
Substantial progress has been made on three tasks of the program and each of
- these is reviewed below.
System Desizn If no credit is allowed for steam inerting, it will require 191,600 lb = ass of Halon 1301 to inert the total containment, including upper and lower compart-ments and ice condenser plenums (1.2 x 106 f t3). The Halon requirement is derived from the flammability data obtained in the previous ARC study and the assumption of 75% zirconium cladding reaction releasing 1450 lb mass of hydrogen. Assuming l negligible losses and specifying a 20% excess, the total Halon requirement will be 230,000 lb. Neglecting losses is justified because the containment leak rate is essentially zero, and the loss to cooling water is 454C lb via Halon decompo-sition and 880,1b through dissolution. The containmec .11.1 pressures will be (70*F basis):
Air 1.000 atm = 14.70 psia H 0.234 ata = 3.44 psia 2
Halon 0.493 atm = 7.25 osia 1.727 atm = 25.'3 psia = 10.7 psig l
. - . .- .~ -. - - = . . ,
_ . ~
Contract TV-55205A Interim Report Page Three A storage and piping configuration has been designed which is based on the guiding principle that the system must function properly even if two independent
=alfunctions occur simultaneously. The Halon would be stored in five 316 stain-less steel tanks, four of which would contain the required 230,000 lb and an iden-tical fifth back-up tank would contain 57,500 lb. The storage tanks are sized to contain the Halen at temperatures in excess of 130*F where the liquid density is 77.6 lb/ft3 Each tank would have an equivalent spherical diameter of 12 f eet with a wall thickness of three <nches. This provides a working pressure of 600 psig for the system, conforminb cc Section VIII of the ASME Unified Pressure Vessel Code.
Each tank would have an associated tank of nitrogen gas connected to it which would maintain a delivery pressure of 600 psig if the Halon had to be discharged.
The five Halon tanks are valved independently to two manifolds of four-inch .SS Schedule 40 pipe. (The manifold piping diameter may have to be larger if a total run of much more than 300 - 400 feet is required.) Two penetrations of the cou-tainment will be required for the four-inch pipes. The piping will conform to ANSI B-31.10 classification. Inside the containment, the piping branches to the
- er and lower compartments, each accumulator compartment and the instrument room
_. saximize coverage of isolated compartments.
An array of spray nozzles comes off each manifold pipe inside the containment.
The requirement is to deliver 230,000 lb Halon in 1000 seconds or 1330 gpm at 130*F.
One arrange =ent to accomplish this is to use 20 full cone nozzles of 15/32" orifice on each manifold, one of which is sufficient. This feature of ti.e system design is being left open at present. The _ exact nozzle system configuration would iave to be determined by actual inspection of the containment and computation of the require-ment in each area.
The final report will present the system design in much greater detail. Other i aspects of the design are also being worked on, including instrumental analysis re-quirements.
Halon Decomposition and Bromide Ion Concentration l
Since the net decomposition of Halon ceases at equilibrium Br concentration l of 5.2 x 10-3 moles /1, the total quantity of Halon decomposed depends (at equili-briu=) upon the total quantity of water in the containment (6.46 x 10-3 lbs Halon decomposed per gallon of water). For the maximum amount (702,950 gallons, re: TVA letter of Oct. 31, 1980), the quantity of Halon decomposed is 4540 lb, independent of the fission product release to the water. An additional 880 lb will remain dis-solved in the water.
The rate of Halon decomposition also depends upon the quantity of water in the containment. The time-dependent quantity of Halon decomposed for several potential values of the containment water inventory has been computed and will be given in the final report.
Decomposition of Halon yields Br- in solution which acts as a scavenger for the OH radical and tends to suppress further Halon deco = position. Equilibrium is attained at a 3r concentration of 5.2 x 10-3 moles / liter also.
j ,Centract TV-55205A Inte.-hn Report Page Four .
Water Chemistry and pH Er- is presumably formed as ".. aitd decomposition HF ionization, of Halon however, also produces is suppretecd by HF 1 at concentrations 3 times that of HBr. dissociated.
the H+ from HBr ionitation, and at equilibrium most of the HF is un The pH changes depend upon the initial chemical composition and pH water in the containment system. l to alkaline (pH >7) and perhaps buffered (presence of sodium borate, for examp i le, prevent criticality), calculations of the pH changes have beenAssuming made conservat com- ve y
' assuming pure water (pH of 7.0) in the containment system initially. 4 for HF, the re-ih plete ionizat-lon of H3r and an ionization constant of 3.53 x 10 HF ionization largely suppressed.
Shock Ignition of H -31r-Halon 3
Mixtures by Hydrogen-air s.ixtures can be inerted against combustion by addition of Eslon 1301, and a large body of data on the flammability limits of Thesuch mixtures questien aas has ke d In developed previously using sparks and squibs as d to ignition determine - sources order to answer this question, a literature search is being conducte if the matter has ever been studied, and an analysis of the hydrogen c chemistry is being performed.The analytical work, although still incomplete, is indicatingnnot be sh direct information. i that initiated.
once inerted against sparks-or pyrotechnic ignition, a m xture ca in definite conclusions are possible because hydrogen-oxygen combustion is the 4
understood of all fuel systems.
structural effects would be In addition, we are examining the question of what f various dimensions, expected from explosion of uninerted pockets of H2 -air i Very truly yours, a
ATLANTIC RESEARCH CORPORATION i
[ddf. Alc/%
Edward T. McHale, Manager Combustion and Physical Science Department.
ETM/bls cc: Stephenb.Miloti American Electric Power Service Corp.
William H. Rasin Duke Powar Company 1
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