ML17252B172

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Special Report No. 14, Hydrogen Flammability Control System in a Boiling Water Reactor.
ML17252B172
Person / Time
Site: Dresden Constellation icon.png
Issue date: 05/24/1971
From:
Commonwealth Edison Co
To:
US Atomic Energy Commission (AEC)
References
14
Download: ML17252B172 (47)
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DRESDEN NUCLEAR POWER STATION UNIT3 SPECIAL REPORT NO. 14 Hydrogep. Flammabilit_y .Control System in a Boiling -Water Reactor RETURN TO RtGlll~13i1l GEM ll JW ROOM 01 S *:*

Commonwealth Edison

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DRESDEN NUCLEAR POWER STATION UNIT3 SPECIAL REPORT NO. 14 HVDRbbEN FLAMMABILITY CONTROL SYSTEM INA BOILING WATER REACTOR

TABLE OF CONTENTS

' QUESTION 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 QUESTION 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 QUESTION 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 QUESTION 4_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1

-QU_ESTION5 .. .. . . .. . . .. . . .. .. . . .. . . . . .. .. .. .. . . .. .. . . . 5.1 QUESTION 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 QUESTION 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1-QUESTION 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1

LIST OF FIGURES Figure TI tie 1-1 Flammability Control System 1-2 Containment Atmosphere Monitoring System

  • 4-1 Decay Energy Versus Time 4-2 Integrated Energy Versus Time 4-3 .Gamma Absorption Fraction in the Core 4-4 Flammability Experiments of Furno, Et al 4-5 Effect of Initial Metal-Water Reaction on Initiation Time and Flow Rate 4-6a Flammability Limit Versus System Requirements For Initial Metal-Water Reaction of 2%

4-6b Flammability Limit Bersus System Requirements for Initial Metal-Water Reaction of 3%

4-7a Radiolysis Rate Constant Versus System Requirements For Initial Metal-Water Reaction of 2%

4-7b Radiolysis Rate Constant Versus System Requirements For Initial Metal-Water Reaction of 3%

7-1 Two-Hour Cloud Gamma and Thyroid Dose 7-2 Two-Hour Cloud Gamma and Thyroid Inhalation Dose 7-3 Thyroid Inhalation Dose

  • 7-4 Cloud Gamma Dose 7-5 Thirty-Day Cloud Gamma and Thyroid Inhalation Pose LIST OF TABLES

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Table Title. Page*

4-1 Hydrogen Generation Key Parameters - 4.2 7-1 Fission Product Source Terms Applicabl,e to Radiological Evaluation 7.2 7-2 Meteorology and Breathing Rates Applicable During Normal Leakage and 7.3 Containment Venting as a Function of Distance - AEC Bases 7-3 Meteorology and Breathing Rates Applicable During Normal Leakage anCl 7.4 Containment Venting as a Function of Distance - GE Bases 7-4 Basic Conditions Evaluated Which Were Basis for Radiological Evaluation 7.5 ii

  • INTRODUCTION In Am.endrnent .24 w_e provided preliminary information regarding the feasibility of removing hydrogen formed by radiolysis by initiating controlled purging of the containment system. We also showed that the addition of a hydrogen

.. c;ontrol system in addition to the controlled purging did not provide substantial, additional protection to the public and

. theref.orf!!.shoul9 ~~t !>e required in accordance with 10CFR50.109. On December 22, 1970, in a letter from Peter A.

_, )Vlor,ri~ to Cornrno~wealth Edison Company, additional information was requested which would help determine whether the back-fitting of the .Dresden 3 facility would be required. This Special Report responds to that letter.

This Special Report provides a ~onceptual design of a fla~mability control system and a containment atmosphere monitoring system. The flammability control system takes a gas mixture from the containment through a spray cooler to a thermal recombiner. Here the recombiner acts to recombine the hydrogen with any oxygen to form water. The resulting mixture is discharged into the torus by an eductor which provides the motive power for the system. In a noninert system where oxygen is initially present within the containment, a flame arrestor is added to the system immediately upstream of the thermal recombiner to prevent possible flame flashback into the containment.

Redundancy of the active components is provided for this system with controlled purging providing complete backup capability.

The containment atmosphere monitoring system is provided to detect the concentration of hydrogen and oxygen within the containment and to provide indication of the amount of fission products which have been released to the drywell and torus following an accident. This system is actuated automatically on .high drywell pressure and alternately takes a gas sample from the drywell and the torus, analyzes the sample for hydrogen, oxygen and radioactivity and discharges the sample back to the torus. Complete redundancy is provided by having two independent systems. This system is required for use with either the flammability control system or the controlled purge "system."

lnerting of the containment eliminates the need for forced mixing of the containment atmosphere. However, since continued inerting following a loss-of-coolant accident is necessary with the AEC imposed assumptions, the present inerting system will require upgrading to. meet safeguard equipment standards. If the containment is not inert, equipm~nt will be required to provide forced circulation (mixing) within the containment. Forced circulation will prevent "pocketing" of the combustible gases in the containment. This forced circulation can be obtained with a high velocity blower taking suction from the top of the drywell head and discharging it into the cavity immediately surrounding the reactor vessel.

Amendment 24 showed the cost of the hydrogen control system of 1.6 million dollars. This was based on a preliminary *-

design concept. The minimum cost for the flammability control system as described herein is 1.7 million dollars. The cost of the containment atmosphere monitoring system is 0.7 million dollars. This cost justifies considering this system in light of the "backfit" requirement of 1OCF R50.109.

This report also gives the off-site doses associated as a result of controlled purging of the containment following a LOCA and using a TID 14844 source term and the AEC assumptions listed in Safety Guide No. 3. That is a loss-of-coolant accident is considered wherein the loss of all ECCS is postulated thus providing a TID 14844 source term and a large metal-water reaction. Further assume the conservative assumptions used in AEC Safety Guide 3 including the worst possible meteorological conditions. With the maximum containment leak rate allowed by Technical Specifications the maximum exposure to an individual at the low population zone would be 150 Rem thyroid inhalation dose and 2.4 Rem whole body dose. This is below the 10CFR100 guidelines of 300 Rem thyroid and 25 Rem whole body. Thus further justification for claiming the flammability control system to be a "backfit" is shown.

The possibility of an accident occurring as just described is so remote as to be considered negligible especially when coupled with the conservative assumptions and meteorological conditions postulated to occur. In view of the large cost for a flammability control system it appears far more logical and considerably more consistent to rely on the controlled purging operation should such an improbable accident occur. The controlled purging operation could be performed by the reactor operator who is monitoring the loss-of-coolant accident conditions as they develop within the drywell. He has precise indication that the accident has occurred. He has full knowledge of the ECCS operability, of the hydrogen being generated due to any metal-water reaction and the slower radiolysis reaction, he knows the activity levels within iii

the containment and he can readily obtain the amount of activity being released to the environs through the standby gas treatment system and out the main stack. It is seen then that controlled purging of the containment can be accomplished with full awaren~ of the conditions actually existing at the time of the loss:of-t:oolant aceide.nt ..*- ..

  • It can be seen that the addition of a flammability control system as described in this special 'report does not provide substantial, additional protection to* the public. The addition of the containment atmosphere monitoring syitem provides the operato*r with adequate information to start controlled purging of the containment to prevent hydrogen buildup to dangerous limits. We conclude that the backfitting of the flammability control system* to the. DreSden 3 facility should not be required in accord with the AEC's regulations as stated in 10CFR Part 50.109 .

' j. .' **'

iv

QUESTION 1 Describe the conceptual design of the system referenced in Amendment 24. Discuss the major components of the system, indicate the consideration given to their performance in the post-accident environment, and indicate your

, criteria for redundancy of components. A process flow diagram for the conceptual desig.n of the system should be included. Describe the provisions that would be taken to assure mixing of the containment atmosphere, measuring the levels of hydrogen within the containment atmosphere, and the means for controlling the hydrogen concentration.

ANSWER Amendment 24 referenced a Hydrogen Control System (Flammability Control System) and a Hydrogen Monitoring System (Containment Atmosphere Monitoring System). A description of the systems, as well as pro~isions for assuring mil(ing of the containment atmosphere, measuring the levels of hydrogen within the containment atmosphere, and the

.means for controlling the hydrogen concentration are discussed .below.

1. HYDROGEN CONTROL SYSTEM 1.1 CRITERIA ,r----- - --------

The criteria for the system are:

a. Be operator initiated at a time not less than .30 minutes after the OBA.

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b. Remove hydrogen or oxygen at a ra.te at least equal to the generation rate when the concentration closely *P approaches the hazard concentration.

-.. c. The system must sustain a pressure of 62 psig and a temperature of 340°F and meet the seismic and code requirements of the primary containment.

d. Tl1e system must operate over the temperature range from 100 to 250° F and the pressure range from Oto 35 psig with a relative humidity between 40 and 100%.
e. The system must meet the criteria for redundancy of active components required of an engineered safeguard. }.
f. The system must not influence the containment pressure in a way that would interfere with the operation of other engineered safeguards.
g. The system must be "testable."
h. . The control system must be designed to operate as required un,der the conditions of a Tl D 14844 release.

1.2 SYSTEM DESCRIPTION

  • .The Flammability Control System chosen for Dresden 3 (Figure 1-1) consists of a closed loop with a spray cooler,
  • flame arrestor, a thermal recombiner and eductor for motive power. A direct contact spray cooler removes excessive amounts of steam from the process stream. The process stream then goes to a porous plug flame recombiner that.will decrease the hydrogen .. concentration if it exceeds 4%. The exothermic heat of reaction is removed in a porous plug condenser of identical design to the burner. This insures that the input to the thermal recombiner is less than 5%

hydrogen and at less than 150°F .

.The process stream then enters the thermal recombiner where the hydrogen and oxygen are allowed to recombine

~ithout a flame at temperatures above 1qo°F.

  • The motive force to move the gas through the treatment system is provided by a water driven air eductor. This is considered a passive component and the drive water is, of course, redundantly supplied.

1.1

. I

i

This system takes its input from the drywell and discharges the reactant depleated stream to the torus.

1.3 COMPONENT DESCRIPTION 1.3.1 Cooler

  • ':'t This is a water-cooled (direct contact) condenser-aircooler and water separator unit and has a redundant source of water from the LPCI system (see Subsection 1.3.3). The cooler consists of a spray and drain chamber and a separator de-entrainer section. It has a drain sump with two traps to 'provide single failure of an active component reliability.

1.3.2 Thermal Recombiner-Heater There are two possible forms ofthis unit. In the first, called the internally heated form, the recombiner itself-consists of stainless steel tube about 18 inches in diameter and 13 feet long with about 3 in. of insulation ori the inside. The upstream portion of this recombiner would contain two redundant bundles of heaters, each of about 60 kw capacity.

The temperature of these heaters will be controlled each with a separate controller for a peak heater surface temperature of about 1500° F to prevent burnout. The heaters are sized to provide a heater section exhaust temperature of 1400°F.

Note that at 1500° F the time to 99% completion of combustion is approximately 10 milliseconds.

The heater section of the recombiner is followed by the residence or drift section wherein the hot gas which has not already reacted completely on the heater is allowed to undergo its homogeneous reaction. The drift section has its size conservatively determined on the assumption of a uniform gas temperature of 1200° F.

The heaters are sized to provide a gas temperature of 1400°F from a 1500°F maximum surface temperature.

In the second form, the recombiner consists of an externally heated pipe sufficiently long to ensure that heat would be transferred to the gas. A particular example would be a 2-1 /2 in. diameter inconel tube about 90 feet long coiled in an electrically heated furnace. General Electric, in a commercially available unit, heats about 50 cfm of gas to 1650°F in a 1800°F furnace in this manner. The residence time is very small at this temperature.

1.3.3 Eductors To provide the gas flow through the flammability control system, a device is required to overcome flow resistance and the pressure difference between the drywell and the torus. A water-spray-driven eductor similar to Schutte and Koerting Company No. 5 type 49 water jet exhauster will meet this requirement and will at the same time serve as a direct contact spray cooler for the exhaust of the thermal recombiner.

The water requirements for this eductor could be met by 200 gpm of 80 psi water at 140°F or by 500 gpm of 40 psi water at 200°F and would be provided by the low-pressure coolant injection system. To achieve the lower flow rate the water tap off point is chosen downstream from the LPCI heat exchangers where a maximum water temperature of 200°F is available. Two heat exchanger's are added in series cooled by separate service water sources to result in an output temperature of. less than 140°F. The flow required here is less than 11 % of the normal flow in the LPCI system and can be achieved without any change in LPCI pump size.

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  • 1.3.4 Flame Arrester - Porous Plug Burner (For use in the noninert system)

Since there exists a remote possibility that the input to the recombiner is flammable, a provision would be made to prevent a fire in the recombiner flashing back to the source of gas. Hydrogen rich mixtures of input gas could also cause excessive recombiner outlet temperatures. For these two reasons, a water-cooled porous plug burner-flame* recombiner and porous plug condenser will be added upstream of the thermal recombiner. This flame arrester consisting of a sintered powdered copper plate with two separate copper tube cooling circuits imbedded in it. The gas flow rate through this burner is about 0.2 cfm/in 2 of burner. Since this "flame arrester" is intended to act as a burner in the event of a reactant rich stream, the cooling must be provided to prevent heat damage. In order to fix the flame zone in 1.2

all design conditions, an igniter would be provided downstream of the flame arrester. This igniter would, of course, have no affect when the mixture is really nonflammable. The design of the porous plug itself with respect to the air flow passage size is _such that it *would stop a combustion wave as well as being strong enough to sustain a detonation pressure* wave.

1,4- MIXING 1.4.1 Containment lnerted If the containment is inerted by maintaining the oxygen concentration below 5%, the only factor tending to de~inert is, the radiolytic formation of 0 2

  • Using AEC assumptions, the formation rate of 0 2 does not exceed 3 scfm at the mlriimum time the system would have to be actuated with containment initially inerted to less than 5% 0 2 (about 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after the DBA). In a containment with a free air volume greater than 200,000 ft 3 (Dresd~ 3 containment free volume Is approximately 280,000 ft 3 I. the addition of this small amount of 0 2 from a dispersed source cannot cwase locai nonuni-formity of 0 2 concentration greater than a small fractional percentage. There are many driving sources for mi'xing ~ith the containment. The one driving force for mixing that can be precisely calculated (i.e., diffusionf is sufficient to insure that the maximum volume with 0 2 concentration more than 0.1 % 0 2 greater th,m the average 0 2 concentration is less than 10 ft 3 . Other driving forces for mixing (natural and forced convection) will also exist in the containment; therefore, absolute mixing can be assured. Even if this s.mall volume were to combust the chemical energy

- liberated would be negligibly small.

1.4.2 Containment Not lnerted For a noninert containment (i.e., air atmosphere) hydrogen concentration is the determining factor for system reqllirements. The conservative metal-water reaction assumption used in designing the system (2% of the active fuel cladding) impiies hydrogen generation rates at least two orders of magnitude larger than radiolysis rates will exist during

  • - the lnitiai period of the accident. Thus, there is potentially more of a possibility that pocketing could occur. However, pocketing is still not very likely because: (1) the-actual generati-on rates due to metal-water reactions are at least an order of magnitude less than assumed, and (2) strong convection currents exist due to the blowdown process and the containment sprays when turned on. Thus, even for the metal-water hydrogen evolution rates, mixing will most probably occur. However, a system to promote additional mixing and give added assurance that positive circulation will oecur. has-been investigated for design.

' ' .' . . ~

For the purpose of designing such a system it is postulated that the hydrogen produced by metal-water- reaction takes place over- a finite period of time such as within 1 /4 to 1/2 hour. Also, it is postulated that 2% of the cladding reacts to give abou-t 11,000 cubic feet of hydrogen at the end of that time.

. The logical region for the hydrogen to accumulate if it is postulated to stratify is in the upper section of the drywell. A

.system capable o_f moving several thousand cfm can be installed to move air out of this region and discharge it in the lower region of the drywell. Thus, the entire volume of hydrogen generated would be swept out within a few minutes.

Several -methods of moving this quantity of air have been studied. The most promising system is to install two 10,000

'ctm hi~h velocity blowers taking suction from the upper portion of the drywell head. These would discharge through the openings in the drywell liner to pressure vessel seal. With one blower working this would turnover the upper volume

,* in less than a minute.

The discha~ge wou_ld blow down one side of the annular space between the drywell wall and the vessel where itwould then mix with the remainder of the air. The blowers could be activated within a few minutes after an accident. The power requirements are less than 20 hp per blower and these can be driven from the emergency bus one minute after the LOCA.

Another less desirable means for mixing has also been examined whic_h could be used. This system is one employing static eductors driven by a portion of the containment spray. Unfortunately, these are large and cumbersome and require an extensive water piping layout in addition to ducting. Backfitting costs on such a system are high due to extensive work inside the drywell itself.

1.3

1.4.3 Torus Mixing An additional mixing system in the torus is not needed. First, breaks which uncover the core even momentarily and thus could potentially result in metal water reaction are at least 0.1 ft 2 and such a break will force nearly all the. air into the torus. Thus, even if all the hydrogen which can be produced after the blowdown were carried over to the suppression chamber, it would be mixed with enough air to be well within flammability limits. Further, the hydrogen will be distributed around the torus via the downcomers and will then mix with the air as it leaves the water surface.

There are no obvious pockets within the torus, and the open geometry and relatively small dimensions will ensure good diffusion. Also, the torus sprays are located at the very top and thus are effective at the most optimum location to mix the air volume.

In reference 1, mixing due to sprays is implied from the temperature measurements observed at spray densities of 0.11 to 0.19 gal/ft 2 -min. The spray density in the torus is between 0.3 and 0.4 gal/ft2 -min of mean cross*s~ctional area.

Also, in reference 2 iodine concentration measurements made with sprays can be used to imply mixing since the iodine migration is presumably through the convection present in the containment. At spray rates of 0.10 gal/ft 2 -min, 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> were requir.ed to equalize the concentration but at a rate of 0.29 it required only 1/4 hour. 3 These tests were conducted in a volume of 140,000 ft 3 - a size comparable to the torus air volume. The implicati~n fro~ the foregoing tests is that sprays promote moxing and hence a positive mixing means is already present in the torus. *

2. CONTAINMENT ATMOSPHERE MONITORING SYSTEM 2.1 CRITERIA The Hydrogen Monitoring System must provide the following:
a. A redundant continuous sampling system, capable of operating at the endurance conditions and indicating the volume percent of hydrogen and oxygen in containment and meeting the pressure, temperature, design requirements of the containment must be provided.
b. A redundant activity sampling system* must be provided (not continuous). Existing systems for radiation activity sampling are acceptable provided they meet the same quality requirements as the control*system.
c. The measurement system must be designed to operate and indicate as required under the conditions of a TIO 14844 rel ease.

2.2 SYSTEM DESCRIPTION Conceptual design of the Containment Atmosphere System is shown on Figure 1-2. This system is designed to automatically scan one of two samples drawn from either the drywell or the torus. An Auto-manual switch allows the operator to override the automatic scanning and select the sample point to be monitored.

The sample is drawn from the primary containment and returned by means of a diaphragm. The sample system is a closed loop from sample point intakes to return, equipped with stainless steel tubing and valves throughout. The sample pump shall have an on-off control switch and continuous pump recirculation provisions to allow the sample pump to operate when the sample return line is valved off from the primary containment.

The sample system pump is to be a diaphragm-type pump. Oil, grease, oil fumes, or other petroleum compounds are not to be permitted to contaminate or be discharged in the sample system. The pump is of sufficient capacity to pump the sample gases through the discharge to the primary containment against 62 psig pressure head.

1. INC-1325 "Simulated DBA Tests of the CVTR - Preliminary' Results", October 1969.
2. BNWL-1547 "Natural Transport Effects in Fission Product Behavior in the CSE", December 1970
3. BNWL - 1084 Nuclear Safety Quarterly Report, February-March 1969.

1.4

The Containment Atmosphere Monitoring System will continuously monitor the containment atmosphere following a loss,of-coqlant accident, with the intention of revealing the data or performing the function listed below:

a. The hydrogen content (H 2 )

b ..

c. The noble gas airborne activity concentration
d. To automatically scan each sample on a time sequence
e. . To record.and identify continuously the hydrogen and oxygen content of the sample being monitored.

2.3 COMPONENT DESCRIPTION 2.3.1 Hydrogen and Oxygen Analy~er The hydrogen analyzer will monitor continuously the hydrogen content of the pumped sample. It is capable of operating and analyzing the hydrogen concentration of a mixture of air, nit~ogen, and saturated steam at 340°F and 62 psig at the source of the sample and will detect a hydrogen concentration which constitutes 0.1 to 20% of the sample volume with an accuracy of +/-2%. An alarm is provided at about 90% of the hazard level.

The hydrogen analyzer will have an- adjustable high level H 2 concentration alar~ syste~ that is adjuStable over the full-scale range of the instrument. The alarm contacts shall close on either H 2 concentration or instrument failure (power loss, etc.).

The hydrogen analyzer will be capable of operating for at least 90 days of continuous, unattended operation before calibration adjustments are required.

The oxygen analyzer will monitor continuously the oxygen content of the pumped sample. It is capable of operating and analyzing the oxygen concentration of a mixture of air, nitrogen, and saturated steam at 340°F and 62 psig at the source of the sample, and will detect an oxygen concentration of 0.1 to 25% of the sample volume with an accuracy of

+/-2%. An alar'm will be provided at the 5% level.

The programmer will contain the electronic and mechanical components necessary to program, and control the complete analysis cycle._

Designed with a mechanical-auto zero configuration, the programmer will permit bargraph presentation of the hydrogen/oxygen concentration on a strip chart recorder. An adjustable contact will be provided on.the recorder which can be set as low as 0.1 % concentration by volume of hydrogen/oxygen.

2.3.2 Fission Products Monitoring System 2.3.2.1 Particulates Filter Operating mode of the particulate filter is such that movement of the filter could be selected for continuous or step advance. Step programming is adjustable between 1 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. A manually operated switch, operated from the

-* control room is provided to override the automatic step programming and advance the filter if desired .. A failure alarm is provided which is actuated if power is lost or the filter tape is torn. The filter is designed for operating for at least 90 days of continuous, unattended operation.

1.5

2.3.2.2 Iodine Filter The iodine filter is a charcoal-cartridge-mounted in series with the particulates filter. The filter is of a fixed type, capable of being manually changed and is designed for at least 90 days of continuous, unattended operation. The filter element is supported in a shield assembly.

The filter shall be capable of removing at least 99% of the iodine activity entering the filter. This efficiency shall be maintained during the entire sampling period.

2.3.2.3 Gas Monitor The gas monitor channel is designed to monitor the effluent for gaseous radioactivity after it has passed through the iodine filter. The system is designed to monitor gross gamma energy over a three-decade range 109 MeV /sec/ml down to 106 MeV /sec/ml. A solenoid-operated check source is provided with an actuation switch on the ratemeter panel for check and calibration.

2.3.2.4 Rate meter The log ratemeter is to be all solid*state construction with a minimum of three-decade scale.

2.3.2.5 Recorder The recorder is a two pen strip chart type designed to match the log ratemeter output.

2.3.2.6 Grab Sample A one-liter capacity grab sample is provided for a manual sampling and calibration. The grab sample is equipped with an

,automatic type sample disconnect.

2.3.2.7 Control The system is designed to start automatically on the high drywell pressure signal or manually from the main control room.

1.6

FCF: IOSX904 (DRESDEN Z f3) *

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rROM /40°F LPci B-----1 40GPM ZOOGPM

  • , 20GfM

[)£MIN W,QT£R. FLRME

,QRRESTOR ft=----....&.-+-L--~ I SPRllY

'------' 1-------1------1 COOLER

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ZO ~PM 4CPSJ IJeMIN WllTc-e RJR AIR CONTAINMN75 ONLY TWO FET BELOW LOW W/ITE,e LEVEL IN TORl.IS FIGURE 1-1 FLAMMABILITY CONTROL SYSTEM

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I. SYSTEM "A" SHOWN, SYSTEM 11 8 11 IDENTl.CAL

2. NOBLEGAS MONITORING SYSTEM MAY BE LOCATED IN A SEPARATE CABINET.

~. CABf NET SHALL BE EQUIPPED WITH.

AUXILIARY HEATING* ELEMENT FOR SAMPLt CONDITIONING AS REQUIRED. ' .

4. CONDENSATE PUMP SHALL BE PROVI~ED IF REQUIRED.

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,. I I I iL-----.J~ 1 LITER UUPU REFERENCE DOCUMENTS:

nssiON PRooucrs ttii>N1rOR1Ne:. I. PRIMARY CONTAINMENT HYDROGEN/OXYGEN CHANNtL (NOTE 2)

MONITORING SYSTEM PURCHASE SPtC 21Al7~1

---~~l-- ------------------ ~---------------- --~-~'"

SYSTEM PURCHASE SPEC 21Al7XX.

RM 40 TO 1001 AIRBllNE CONC£NTRATION 3014d/CC INTE.2GpTED RADIATION LEVEL

. l.h 10 ~ (Co UONTll P[R.IOD) .

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I PRESSURE SUPPRt'E.SION POOL.

I ---------------------

_L .i FIGUREl.1-2 CONTAINMENT ATMOSPHERE MONITORING SYSTEM

QUESTION 2 Describe how such a sys:tem might be installed into an already constructed facility such as Unit- 3, diseu5sing the location of new equipment and necessary modifications in existing structures and components.

ANSWER

1. MONITORING FOR DRYWELL AND TORUS A new H 2 , 0 2 , and gamma monitoring system is proposed for sampling the gases in the drywell and torus. These systems are redundant and could be located on opposite sides of the drywell. The drywell samples can be pulled through 1-inch pipes from existing penetrations X-204 and X-143. The torus samples can be pulled from penetration X-308C and X-3158 and the return line connected to X-315A.

The monitoring panels can be installed in the available spaces at Col Line 46L to Mand 50L to K. These locations will provide separation as well as redundancy. Electrical power, instrument air, cooling water and contaminated drains for the equipment contained therein can be made available from existing sources within 100 feet of these locations.

  • The monitoring system shall have recorder read out and alarms in the control room.
2. RECOMBINER SYSTEM The recombiner assembly, which includes a cooler (flame arrestor for noninerted systems). the recombiner, and eductor, will require floor space of approximately 10 feet x 12 feet including access for maintenance. Two-foot-thick concrete shield walls around the equipment are proposed to reduce radiation levElls to the surrounding areas during post accident operation. This assembly can be installed on the ground floor of the reactor building next to the south wall between columns 46 and 47. The floor at this point are capable of taking 600 lbs/ft 2 loading.

The 4-in. drywell outlet line would be tied into the existing 18-in. drywell outlet line at the 572-ft level just outside of penetration X* 125. Core drilling of two floors will be required to route this line* to the ground floor.

The water supply for the cooler and eductor can be provided from the two LPCI loops in the basement corner rooms.

An additional heat exchanger for each loop would be installed to provide water temperatures below 140°F, and would be cooled by service water available at these locations.

The 4-in. water lines will tie into the LPCI loops downstream of the existing heat exchangers. The two water lines can then be routed up to the main floor and into the cooler and eductor through check valves. The redundant water supply lines will insure water to this system even if one loop of the LPCI is disabled. Core drilling will be required for routing/

the pipe lines between floors.

The discharge of cooled gases and water will be carried to the torus basement room by a 6-in. pipe line into spare penetration X-316A (10 in.). The trapped drainage from the contact cooler will also be routed into the above line to the torus. \

I The flame arrestor will require 20 gpm of 40 psig water with minimum impurities. Two sources available are condensate transfer storage tank and fuel storage pool.

. Power for the recombiner heaters (up to 60 kw) will be available 30 minutes after an accident from the two emergency buses supplied by the diesels.

The control panels for the recomb_iner system will be located adjacent to the H2 , 0 2 , and gamma monitoring panels

  • (listed in A above).

2.1

3. DRYWELL MIXING BLOWER These would be installed above the drywell-vessel seal to avoid costly work inside the drywell. Electrical power from the emergency busses would be brought in through existing spare penetrations. There are a sufficient number of holes in the seal to permit adequate air circulation and discharge.

2.2

QUESTION 3

.-.-Brea!< c:lown ttle 1'6" rrrillion dollar *cost estimate-for *the hydrogen control system into -cost for equipment, cost of

,ins~allation, and cost of reactor downtime and discuss the effect ori these estimates if the installation were to be conduct.ed concurrently with a refueling outage.

()

ANSWER

  • The cost estimate of 1.6 million dollars for the hydrogen control system provided in Amendment 24 was based upon a preliminary conceptual design. The cost has been estimated using the more detailed conceptual design described in the answer to Questions 1 and 2. As discussed in the answer to Question 1, the noninerted system has been required to have a mixing system provided to preclude the possibility of pocketing of hydrogen within the drywell. The cost estimate then includes a comparison of the costs for the inerted system and the noninerted system. The cost estimate follows:

COST ESTIMATE - DRESDEN 3 ONLY FLAMMABILITY CONTROL SYSTEM AND CONTAINMENT ATMOSPHERE MONITORING SYSTEM (Dollars in Thousands)

Inert System Noninert System Flammability Control System

., Cost of Equipment $ 345.4 $ 464.3 Cost of Installation 1,381.2 1,586.7 C,ost of Reactor Downtime 0 258.0 Containment Atmosphere Mo.nitoring System Cost of Equipment 314.6 314.6 Cost of Installation 210.4 210.4 Cost of Reactor Downtime 0 0 Cost of Upgrading of lnerting System 170.6 0 TOTAL $2,422.2 $2,834.0

    • The above costs are as of 'May 1971, with no cost escalation applied beyond this date. Also, no cost or reactor downtime was included for stress relieving of drywell and torus.

Costs for reactor downtime assume that installation of all equipment located outside the drywell is accomplished while the reactor is operating and that installation of equipment .inside the drywell is accomplished concurrent with the refueling operation. Therefore, the reactor downtime is quoted as that amount of time in addition to the refueling outage time.

3.1

The above listed cost estimates show the inerted system costs to be a less cost than the noninerted system. This, as mentioned earlier, is due to the mixing system which is necessarily employed to preclude the possibility of pocketing of hydrogen within the drywell. Not included in the cost estimate, however, is the cost associated with operation of the inerted system compared t9 that of the noninerted system. It is estimated that the cost of operation associated with the inerted system is approximately $540,000 per year, whereas the cost of operation associated with the noninerted system is negligible. Thus, the noninerted system would realize a savings above the inerted system in less than one year

  • 1 of operation.

3.2

QUESTION 4

-- ---~- -- ~ *- ----- -~~**- -~- -*-- -- - --- -.--- -~- ----- -- ------- -~ --- --- - - -

Detail the assumptions used in ardving at your conceptual model of the recombiner system including the extent of initial metal-water reaction, initial oxygen level, the radiolytic hydrogen generation rate (G(H 2 )), the fission product source term, transport and distribution model, and the 1.ower flammability limits for the hydrogen mixture assumed.

Discuss the sensitivity of the system design and costs to various changes in design parameters such as varying the initial metal-water reaction or the hydrogen generation rate. The enclosed table lists values of the parameters that we consider should be used to determine the concentrations of hydrogen and oxygen in the primary containment. These parameters should be included in the sensitivity comparison.

ANSWER The question will be answered in two parts: (1) the values of the key parameters used in defining system requirements will be discussed in detail; and (2) the sensitivity of the system design to variations in the key parameters will be discussed. All studies were based upon a noninert containment.

The hydrogen control system requirements have been determined using the AEC tentative recommended values with the exception of four items:

a. Gamma radiation energy absorption in the core of 5% rather than 10%;
b. Radiolytic decomposition rate in the *5uppre.ssion pool of 0.2 molecules Hz/100 ev rather than 0.5 molecules Hz/100 ev;
c. A flammability limit of 8% hydrogen by volume rather than 4%;
d. Extent of metal-water reaction of 2% rather than 5%.

The hydrogen control system resulting from these assumptions has a required initiation time of 156 hours0.00181 days <br />0.0433 hours <br />2.579365e-4 weeks <br />5.9358e-5 months <br /> after the LOCA, and the corresponding control system flow rate must be 9 scfm.

Further, this.control system, designed with these conservative assumptions, eliminates the need for containment atmosphere inerting.

1. KEY.PARAMETERS

. Table 4- l list~ the key parameters and values used in arriving at the system requirements. These values are. similar to the AEC tentative values (which were recognized to be very conservative by the AEC staff when first proposed) with four exceptions. These exceptions are:

AEC tentative value GE value L Fraction of fission product gamma radiation energy absorbed by coolant in core region 10% 5.0%

2. RadiOlytic decomposition rate (GH ) in the 0.5 molecules H1 0.2 molecules H2 2

pressure suppression pool 100 ev 100 ev

3. Hydrogen concentration for lower limit of flammability 4% 8%
4. Extent of metal water reaction during the LOCA, percent of active cladding 5% 2%

4.1

Table 4-1 HYDROGEN GENERATION KEY PARAMETERS

1. Fraction of fission product radiation energy absorbed by the coolant. .,

(a) Beta (b) Gammas (1) Betas from fission products (1) Gammas from fission products in the fuel rods,

  • in the fuel rods: 0 coolant in core region: .05 (2) Betas from fission products (2) Gammas from fission products intimately mixed intimately mixed with coolant: 0 with coolant, all coolant: 1.0
2. Core: 0.5 molecules/100 ev Suppression Pool: .2 molecules/100 ev
3. Core: 0.25 molecules/100 ev Suppression Pool: .1 O moleeu les/100 ev
4. Extent of metal-water reaction (Percentage of active fuel cladding that reacts with water) 2%
5. Aluminum corrosion rate for aluminum exposed to solution. 200 mils/yr **'

I

6. Fission product distribution model (a) 50% of the halogens and 1% of the solids present in the core are intimately mixed with the coolant water.

(b) All noble gases are released to the containment.

(c) All other fission products remain in fuel rods.

7. Hydrogen concentration limit 8vol%

J It should be noted that item 2, the radiolytic decomposition rate of 0.2 molecules/100 ev, applies only to the suppression pool. The AEC proposed value of 0.5 was still used in the core region. The reason for this distinction between the suppression pool and the drywell will be explained in Section 2 ("Suppression Pool Radiolytic Decomposition Rate") of this Question.

It should also be noted that the assumptions regarding the release of fission products from the core were the same as those proposed by the A.EC. This assumption alone will result in a conservatively sized system as will be shown in the discussion of the sensitivity of the design to variations in the key parameters.

The justification for using different values than those tentative values proposed by the AEC in the four areas discussed .

above will be presented in the following paragraphs.

4.2

1.1 GAMMA RADIATION ENERGY ABSORPTION IN THE REACTOR CORE WATER

- - -*-- ---- - - !)~tailed calculations were conducted to evaluate the extent of gamma radiation absorption by the water in the core region followlng a.postulated loss-ofcoolant accident (LOCAi. Thifreactor core was assumed to have-been operated for*

108 sec (i.e., approximately three years) prior to the accident. The fission product gamma ratiation source data used for the calculations *was based on empirical fits to measured data. 1 A total of eight separate energy spectrum levels were used in the calculations. The energy spectrum covered the range from 0 to 6 mev.

The physical model used in the calculations consisted of an infinite array of fuel rods at its normal spacing. The amount of energy deposition in the fuel, cladding, and water is calculated by converting the computed energy flux into energy absorbed in a given material using the linear energy absorption coefficient, µa (i.e., nuclear cross section) and the volume fraction. The total energy absorbed by each material is obtained by summation of the integrated energy absorption of the eight energy bands.

The reactor core gamma decay energy consistent with the TID 14844 release is given on Figures 4-1 and 4-2.

The amount of energy deposited in the reactor core region is shown on Figure 4-3. It can be seen that the use of a constant value of 5% will result in a conservative in~egration of the total energy deposited in the coolant over the time ranges of interest *(i.e., one day to five or six days).

1.2 SUPPRESSION POOL RADIOLYTIC DECOMPOSITION RATE The* postulated fission* product release Tl D 14844 is associated with a molten core and the release of 1.00% of the noble gases, 50%_ of the halogens and 1% of the solids from the nuclear fuel. This assumption is inconsistent with the conservative design of the emergency core cooling .network and its redundant systems. Actual release of fission products

., would be much less 2

  • 3 than arbitrarily specified in TIO 14844. However, the postulatior:i of TID 14844 necessit_ates the evaluation of the extent of energy associated with the fission products and consequently the extent of fission products potentially available for radiolytic decomposition of water outside the core region (i.e., in the suppression pool). The noble gases would be airborne and only the fission products trapped in the water (i.e., halogens and solids) would contribute to the overall radiolytic decomposition rate of water. The resulting core decay energy c.onsistent with the TID 14844 release and the energy associated with both conditions of 50% halogens-1% solids and 25% halogens (1%

solids are given on Figure 4-1). In addition, the integrated energy for both the core and suppression pool regions is given .

on Figure 3-2. Although TID 14844 allows for plateout of one-half of the released halogens, the inconsistent AEC assumption for radiolytic decomposition has been accepted to deposit all of the released halogens and the solids into the suppression pool thereby resulting in an infinte partition factor (i.e., no airborne halogens). Therefore, all decay energy (gamma plus beta) associated with the released halogens and solids is assumed to be deposited in the suppression pool.

a The total extent of radiolytic decomposition according to the ORNL simulated BWR radiolysis tests4 ,s*. 6 is function of both the residence time and the water temperature. Similarly, an evaluation of the ORN L test data revealed a maximum hydrogen yield rate (GH ) of approximately 0.2 at short residence time (7 minutes). and low water 2

1 Smith, M.R., "The Activity of Fission Products of U2 3 5 ," XDC-60-1-57 General Electric Company.

2 0RNL Nuclear Safety Research and Development Program Bi-Monthly Report, ORNL-TM-2777, September-October 1969.

3 Horton, N.R., Williams, W.A., Holtzclaw, J:W., "Analytical Methods for Evaluating the Radiological Aspects of the General Electric Boiling Water Reactor," March 1969 (APED 5756).

4 "Hydrogen Generation in a Boiling Water Reactor" Dresden Nuclear Power Station Unit 3, Amendment 23.

5 Zittel, H.E., 3.4 "Radiation and Thermal Stability of Spray Solutions", Nuclear Safety Bi-Monthly Progress Report September-October 1969, ORNL TM-2777.

6 Zittel, H.E., 3.4 "Radiation and Thermal Stability of Spray Solutions", Nuclear Safety Bi-Monthly Progress Report November-December 1969, ORN!,. TM-2829.

4.3

temperature. Application of the ORNL test data to the suppression pool with essentially an inf_initely long residence time of fission products would result in a maximum GH of approximately 0.1. In addition; a shutdown radiolysis test 2

conducted at KRB in May 1970 yielded an overall hydrogen generation rate, GH of approximately 0._14 *. * . .: .

2 Therefore, a maximum hydrogen yield of 0.2 molecules H2 /100 _ev is the Gene~al *Electric design basis for the suppression pool. This value is conservative, based on: ( 1) test data, (2) the Tl D 14844 fission product release, and (3) the assumption that all of the released halogens and solids are deposited in the pool water. ' . *:

Since the residence time of coolant in the core region is much shorter than in the pool, the AEC proposed value of 0.5 molecules H 2 /100 ev was used in the sizing studies.

1.3 FLAMMABILITY LIMITS In a recent paper on the subject of flammability limits, Furno, et al 7 have demonstrated exp~ri~entally that the lower flammability limit for a fixed volume system is apporximately 8% hydrogen by volume in air. Figure 4-4 is taken from this paper. This figure shows that until the hydrogen concentration reached the 8% hydrogen. concentration level, the hydrogen will ignite locally, but cannot be sustained.

Further, it must be noted that previous analyses 8 have shown that the pressure suppression containme.nt can sustain the pressure and temperatures associated with burning of hydrogen in the containment even with hydrog.en con;c~ntrations above 20% by volume. The pool temperature rise associated with burning is approximately 5 to 10°F. The containment pressure rise is in the range from 10 to 50 psi, well within the drywell pressure capability. The data of Furno, et al, show that even with 12% hydrogen by volume, the pressure rise was only 50 psi in _a closed velum~ without venting.

Hence, the choice of 8% hydrogen concentration by volume as a lower limit of flammability in a hydrog~f)-air'mixture has two margins of convervatism: ( 1) the actual pressure rise at 8% H2 is much les.s than the theoretical value; and (2) even if all of the hydrogen does ignite, it has been shown 9 that the pressure suppression system can easily .a~c;o~modate the energy release, even when hydrogen quantities are many times those associated with 8% hyd~ogen concentration.

There are several laboratories with equipment of a size of interest in which additional tests .covering param.eters of .,

interest can be conducted. General Electric Company is planning conduct of such tests 'to e~t-ablish. hydrogen concentration limits applicable to the containment hopefully before the end of the year.

1.4 EXTEND OF METAL-WATER REACTION *I,*

The postulated loss-of-coolant accident would result in an increase in temperature of the nuclear fuel rod cladding, thereby resulting in a metal-water reaction and the release of hydrogen gas. The overall extent of. the ~etal-water reaction was conservatively calculated to be less than 0.15% across the entire postulated break area spectrum, the worst bundle having 'V1 %. Even under the extremely severe conditions of the simulated spray cooling transients qonducted under the FLECHT program, the maximum extent of metal-water reaction for the Zr-2 test wa.s m.ea~ured to be only 1.4% 1 0 This is much less metal-water reaction than would have been predicted if our conservative. analytical assµmptions had been applied to the test bundle. If the total core metal-water reaction is calculated b~sed on a rate consistent with that observed in the FLECHT test the core metal-water reaction would be 0.10%. However, a conservative values of 2.0% total core metal-water reaction rather than 0.1 % was selected as a design basis to provide

  • Based on 5. % 'Y to H2 0; 'Y = 60% of core decay.

7 A.L. Furno, E.B, Cook, J.M. Kuchta, and D.S. Burgess "Some Observations on Near Limit Flames", Proceedings of the International Symposium on Combustion, No. 13, Salt Lake City, 1970, to be published June 1971.

8 D.J. Liffengren, "Considerations Pertaining to Hydrogen lnerting", APED 5654 August 1968).

9 Dreden Unit 3, Amendment No. 23, AEC Docket 50-249.

10 Duncan, J.D. and Leonard, J.E., "Thermal Response and Cladding Performance of an Internally Pressurized, Zircaloy-Clad, Simulated BWR Fuel Bundle Cooled by Spray Under Lott-of-Coolant Conditions~" GEAP-13112 April 1971.

4.4

margin in the overall design of the flammability control system. The conservatively large amount of hydrogen released is assumed to be equally mixed between the drywell and torus, resulting in about a 4% initial hydrogen concentration .

2. SENSITIVITY ANALYSIS System requirements are subject to rapid changes in magnitude when certain key parameters are extended beyond a point whose magnitude is dependent on the other parameters. This extreme sensitivity makes it very important to make reasonable judgements in selecting design values for the key parameters. For example, if all the AEC proposed values
    • for the key parameters were used to size a noninert hydrogen control system, the system would have to be actuated at time zero because the initial H2 concentration would exceed the 4% limit porposed by the AEC. Also, the flow rate required would be several orders of magnitude larger than calculated using the reasonable values. No attempt at determining the detailed cost of this system has been done since it would have to be completely different in concept than that described in the response to Question 1. It would, however, be several times as expensive as the proposed system.

System costs are a function of the flow rate. The proposed system was designed for 50 scfm. System costs in the range of 20 to about 70 scfm are essentially the same. Below about 20 scfm, the substitution of tubing for piping will result in slightly lower costs. Above 70 scfm, there will be step changes in costs*as the number of recombiners and associated equipment are increased to cope with the higher flow rates. A system designed to handle 150 scfm would cost roughly three times as much for equipment as the 50 scfm system. Installation costs would not be affected significantly for the larger system. Above about 200 scfm, however, the design concept would have to be changed and there would be a different set of cost requirements. Since no system concepts have been evolved for these higher flow rates, there are no cost estimates available. '

System* <:*osts'will not be significantly affected by changes in the key parameters as long as reasonable assumptions are made for the values. This is because system flow rate will always fall within th.;! 50 scfm design size using reasonable

  • assuhiptioris. In order to give a better appreciation for the sensitivity of the system size with variations in the key parameters, a set of parametric curves have been generated.

The parametric curves were generated ~ holding all key parameters constant except one. The parameters varies were:

  • .--~

(1) initial metal water reaction, (2) G 2 in the pool, and (3) hydrogen flammability limit. Unless otherwise stated, Table 4-1 values were used for the parameters held co_nstant. Data plotted were flow rate and initiation time (i.e., time to reach flammability limit).

Figure 4-5 shows the effect of initial metal-water reaction on initiation time and flow rate for two levels (5 and 10%)

of gamma absorption in the core. It can be seen that a sharp rise in flow rate required and a sharp drop in initiation time occur when the initial metal-water reaction is assumed to be greater than 3%. This sharp change in slope is characteristic and will be seen in the other figures. It represents a transition from hydrogen concentration being at the flammability limit in the drywell to it being at the limit in the suppression pool. Because of the differences in volumes and generation rates involved, the flow rate requirements change sharply when there is a transition from. the drywell to the suppression pool as the controlling volume.

Figures 4-6a and 4-6b show the effect of varying the H 2 flammability limit on system requirements for initial metal-water reactions of 2 and 3%, respectively. Again the transition from drywell to suppression pool controlling causes a sharp rise in system requirements. This occurs below 6% H 2 for the 2% initial metal-water case and only slightly below 8% H 2 for the 3% initial metal-water reaction case. Therefore, it can be seen that the transition points are also sensitive to variations in other parameters.

The final set of curves (Figures 4-7a and 4-7b) show the effect of varying the radiolysis rate constant (GH ) in the pool for initial metal-water reactions of 2 and 3%, respectively. The transition points occur at about GH ~ 0.3 for 2 %

2 initial metal-water and GH = 0:2 for 3% initial metal-water.

2 All of the foregoing sensitivity studies were done using Tl D 14844 assumptions for fission product release to the suppression. pool. No credit for plateout of halogens was taken although one-half of the halogens plating-out is allowed

. for dose' cak:ulation purposes. All fission products released except noble gases from the core were assumed to be 4.5

completely mixed with the suppression popl water, thus maximizing the radiolysis rate. Significant reductions. in system requirem~nts co~ld be achieved using a more realistic approach* in estimating the amount of fission. product release calculations on system requirements are best illustrated by using a case in which the other assumptions are extremely conservative. The following table illustrates the sensitivity of the design to the .fission product release model.

Initial IVletal~INater 4% 4% *.*

'Y absorbed in core 5% 5%

GH in pool .5 .5 2

H2 limit 6 6 Fission Product Release IVlodel AEC (TIO) GE System Flow Rate (scfm) 180 34 Vent Time (hours)

Thus, the realistic release model resulted in reducing system size by a factor of 5.

3.

SUMMARY

Based on the preceding discussion (subsections 1 and 2). the following conclusions can be reached:

1. Conservative sizing criteria (Table 4-1) indicate the proposed system flow rate is at least a factor of 5 larger than the minimum required.
2. The system size is a strong function of the assumptions used for the key parameters, especially when the ~/

values exceed certain limits which define whether the drywell or the suppression pool is controlling.

3. Use of the AEC tentafrile values for the key parameters would require a completely different ~oncept because of the extreme conservatism of the assumptions .

. *See discussion on suppression pool radiolytic decomposition rate in A.2 of this Answer an.d references 2 and 3.

4.6

CORE }'(TOTAL - TIO RELEASE) lo- 3 f

I'>

C!J 50% HALOGENS, 1% SOLIDS II::

II.I z ( Y+ /J l II.I

(..)

II.I 0

lo- 4 25% HALOGENS, 1% SOLIDS

'1*

~ l. *.

TIME (hr)

FIGU_RE 4-1 DECAY, EHER~Y VERSUS TIME

COREY (TOTAL - TIO RELEASE) 50% HALOGENS (Y+ /J l 1% SOLIDS 25% HALOGENS ( Y + {J) 1% SOLIDS TIME (tir)

Fl~UR~.4-2 HHEGRATED ENERGY VERSUS TIME.

4 0

LI.I m

a::

0

"'m

<I:

<I:

~ 3 1-z LI.I 0

a::

~

2 0 100 200 .300 400 500 600 700 800

. TIME (hr)

FIGURE 4-3 GAMMA ABSORPTION FRACTION IN THE CORE

60 50 SINGLE SPARK 40 Cl) a.

. REPETITIVE SPARKS 10 Ii I

~ I **'

0 *'

0 2 4 6 8 10 12 INITIAL HYDROGEN (percent)

FIGURE 4-4 FLAMMABILITY EXPERIMENTS OF FURNO, ET AL

~00 GH CORE::::.5 2

GH POOL==.2

  • 300 2 . .

50% HALOGENS/1% SOLIDS IN POOL

.,, =5% FLAMMABILITY=8% H 2

200

. 100 Y=1Cl%

70 /

~

u..

(.) //

~ 50 I

I UJ

<(

a:::

~

I 0

...J 30 u..

~

0 z

<(

..c I

20 UJ Y=l0% - - -

i=

z 0 I i= _ _J

<(

E 10

~

7 Y= 5%

5 3

--- FLOW RATE (SCFM)

INITIATION TIME (SCFM) 2 0 2 4 6

% METAL - WATER REACTION

. *FIGURE 4-5 EFFECT OF INITIAL METAL-WATER REACTION ON INITIATION TIME AND FLOW RATE .

GH CORE =.5 400 2 GH POOL=.2 2

50% HALOGENS/1% SOLIDS IN POOL ~t 300 INITIAL MW=2% OF ACTIVE FUEL CLADDING 200 5% =y

\

~

100

\\.

u..

0

~

UJ 70 \\ 10% = y I-

<(

0:: \\

31:

0

_J u..

50

\\_.

\

0 z

<(

.c UJ j::

z 30 0

j::

<(

20

' 10% =y E

z 10 ............. 5%= y 7 --- FLOW RATE (SCFM)

INITIATION TIME (hr) 5 3

2 4 6 8

(%) H - FLAMMABILITY 2

..FIGURE 4-6a FLAMMABILITY LIMIT VERSUS SYSTEM REQUIREMENTS FOR INITIAL METAL-WATER REACTION OF 23

GH CORE=.5

'-2 300 INITIAL MW=3% OF ACTIVE FUEL CLADDING 50% HALOGENS/1% SOLIDS IN POOL GH POOL= .2 2

  • . 200 150 5%= }'

70

~

LL

(.)

(/) 50

UJ t-

<(

0:

10% =}'. *.,*

...  :;r: ,,-'

'* 0

_J LL 30 c

~ 1 *~. z

<(

:g UJ 20
!: FLOW RATE (SCFM)
  • .~

i==

z INITIATION TIME (hr)

0

i==

<(

~ E

=,,

.-~

~: i z 5%

10

-7 5

~

3

,2 4 6 8

(%) H2 - FLAMMABILITY FIGURE 4-6b FLAMMABILITY LIMIT VERSUS SYSTEM REQUIREMENTS FOR INITIAL METAL_.:WATER REACTION OF 33

GH

  • CORE== .5 2

INITIAL MW==2% OF ACTIVE FUEL CLADDING 300 50% HALOGENS/1% SOLIDS IN POOL FLAMMABILITY==8% H 2

200

>' == 5% - - - - - - - - - - -

100

>'=10% ____________________________--....

70 11.J I-

<(

0:: 50 3::

0

_J LL.

0 z

<(

30 /

11.J

~

z 0

j::

j::

<(

j::

20

>'=10% - - - * - - - -

-- _../'/

/

/

""'/

/

z /

/

10 7

>'= 5% -- --- ------

I __./

FLOW RATE (SCFM) 5 fNITIATION TIME (hr) 3 2 .....~~~~--'~~~~~~~~~~~--~~~~~---~~~~_.,~~~~~~ *'

0 .1 .2 .3 .4 .5 .6 GH IN POOL

,2 FIGURE 4-7a RADIOLYSIS RA TE CONSTANT VERSUS SYSTEM REQUIREMENTS FOR INITIAL METAL-WATER REACTION 0 F 23

~ C<;}RE=.5 INITIAL MW=3% OF ACTIVE FUEL CLADDING 50% HALOGENS/1% SOLIDS IN POOL 300 FLAMMABILITY= 8% H 2

100 Y=5%------

~ 70 u.

u

~

UJ I-

<( 50 a::

3:

0

...J

. u.

c z

<(

30

.c UJ

~ 'Y=lQll..O - - /

I-z 20 0

j::

<(

/

E

~ /

10

____ /

,, =5% ----

7 FLOW RATE (SCFM)

INITIATION TIME (hr) 5 3

2L..~~~__J~~~~---'-~~~~-'-~~~~"':-~~~~:--~~~-;

0 .1 .2 .3 .4 .5 .6 GH IN POOL 2

FIGURE 4-7b RADIOLYSIS RATE CONSTANT VERSUS SYSTEM REQUIREMENTS FOR INITIAL METAL-WATER REACTION OF 33

QUESTION 5 Describe-the electrical -power -requirements for -this system and relate to the increased- load-on the d ieseL generators- -- -

and/or battery.

ANSWER The flammability control system requires about 60 kw for each heater., The heaters should be supplied by seprate emergency busses. This power is not needed until at least one-half-hour following the accident. The timing of this demand is such that there is no addition to the emergency bus peak demand.

The mixing system adds about 20 hp maximum to each emergency bus, but it need not be initiated until several minutes after the accident. Hence, the timing is not concurrent with the peak diesel load.

Some very small loads are applied to the battery system but these will not add appreciably to the battery-loading requirements.

5.1

QUESTION 6

- -Describe-the operation of the system after: a LOCAJincluding the pl_ans for monitor_i!'!:l _!he_ containme!"'t _atmosphere) from the control room and describe any necessary operator action in initiating the system and during its operation.

ANSWER In the event of a LOCA, the containment atmosphere monitoring system would actuate automatically and begin providing information to the control room. Some time following the blowdown (more than 30 minutes). the operator would have been able to assess the hydrogen, oxygen and radiation levels within the containment. The operator would initiate the flammability control system from the control room as soon as a significant amount of hydrogen begins to be evolved, thus limiting any possibility of explosive mixtures within the containment. No further action is required.

6.1

\

QUESTION 7

- - - - - - - _____ Comp~r:_e1_hgsjiJfuJc.i1t?CLe>_fJ-si!~d_ose~fr_QIT!_a desigr:i basis LOCA using this system with those calculated and reported in Amend~~~ts 23 and 24 assuming venting ~th;-;;~~t~i~m~itl: Use,_the-assu-mptTons-glven-in-Safety--Gulde-3

... ("Assumptions . Used for .Evaluating the P,otential Radiological Consequences of a Loss-of-Coolant Accident for Boiling

,Water Reactors", November 2, 1970) a~d the assumed acci.dent containment leak rate of 2.0% of the containment

.. , -volum~ pe~.day (r~ther than the 0.635% per day assumed in the calculations presented in Amendment 24). Consider the effects of containment inerting to initial levels of oxygen in the range from 1 tb 5 vol % in delaying the initial use of the

. hydrogen .co.ntrol system, ANSWER 1 RADIOLOGICAL EVALUATION - CONTAINMENT VENTING i

' ,_, - INTRODUCTION The radi.ological exposures resulting from venting the primary containment following a loss-of-coolant accident are presented in this section and are based upon various assumptions regarding percent of metal-water reaction, maximum hydrogen concentration, fission product source term, etc. The combi9ation of the various parameters into the most pessimistic condit.ions has resulted in various venting times and venting rates. These conditions' are coupled to the meteorological conditions assume.ct to exist at the time of venting to arrive at the maximum off-site exposure. Two basi~ source terms have been considered in arriving at the calculated exposures: ( 1) those presented in AEC Safety Guide No. 3 1 and. (2) those presented in APED 5756 2

  • The source terms in Safety Guide No. 3 (referred to hereafter as .!

AEC assumption~) neglect the redundant safeguard systems provided to prevent core melt thus providing an upper limit .Jo to.t~e calculated .exposures. The source terms in APED 5756 (referred to hereafter as GE assumptions) consider only partial credit for these safeguards, thus providing a more realistic but still conservative estimate of the possible

  • consequences. The source terms considered are presented in Table 7-1. In addition to the.difference in source terms two conditions were e.valuated with regard to the meteorology coincident with the LOCA. The meteorology coincident with

.. the AEC source term was the "envelope" meteorology discussed in Safety Guide No. 3, while the meteorology coincident with the GE Source term was unstable and neutral. These conditions* and their appropriate duration of applicability are presented in Tables 7-2 and 7-3.

' N~te ~h.at the que~i~n ask~ that a containment leak rate of 2.0% of the containment volume per day be used for the calculations. However, the maximum leak rate allowed by technical specifications is* 1.6% of the containment volume .:,,

per day. Therefore, the leakage rate used for the calculations is the technical specification value of 1.6%.

1.2 SENSITIVITY ANALYSES The various cases regarding percent metal-water reaction, H2 generation, etc. arid the applicable parametric values which were investigated from a radiological dose consideration are shown in Table 7-4. The doses resulting from those cases are presented in Figures 7-1 through 7 -5 as a function of distance from the release point. The effective release height considered was 100 meters with flat terrain for all distances. As noted in Figures 7-1 and 7-2, the two-hour cloud gamma and thyroid dose for either GE or AEC assumptions is well below the respective 25 rem and 300 rem guidelines set forth in 10CFR100.

The 30-day thyroid dose as a function of distance and venting condition using AEC assumption is presented in Figure 7-3, while the 30-day cloud gamma dose is presented in Figure 7-4. As noted for the LPZ applicable to the Dresden Site 1

Safety Guide 3 - Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactor - November 2, 1970.

2 "Analytical Methods for Evaluating the Radiological Aspects of the General Electric Boiling Water Reactor," APED 5756, NR Horton, WA Williams, JW Holtzclaw.

7 .1

Table 7-1 FISSION PRODUCT SOURCE TERMS APPLICABLE TO RADIOLOGICAL EVALUATION . '

APPLICABLE VALUE FOR ASSUMPTIONS OF PARAMETER GE *AEC

1. Fuel Rods damaged 25% 100%
2. Fission Products Released Noble Gases (Avg) 1.8% 100%

Halogens (Avg) 0.32% 50%

Solids (Avg) 1% ~

' 1%

3. Plate()ut Factor Applicable to Halogens 2 ' ' 2

... * :i_

4. 12 C9nv.. ,to CH 3 I 1% *ao/o
5. Venting Via Suppression Pool Ye5 *- *Yes
6. Reduction in Suppression Pool '

Noble Gases 0

0 *'

Elemental Iodine ** 10 :

Methyl lodi.de 2 ' :t

  • *10*

.Solids I ,A*

7. Filter efficiency SGTS (%) 99  :*1*90**
  • The elemental iodine and particulate fission products in the suppression pool are assumed to be in equilibrium with the primary containment free volume with a partition factor of 100 applicable. *
  • 7.2

Table 7-2 METEOROLOGY AND BREATHING RATES APPLICABLE DURING NORMAL LEAKAGE AND CONTAINMENT VENTING AS A FUNCTION OF DISTANCE - AEC BASES Time Breathing Rate Sector Frequency Meteorology and Wind Speed (m/sec) As a Function of Distance (m)

(cc/sec) Avg. Meteorology Condition

(%) 300 500 800 1200 30QO 7000 0 to 8 hrs 347 No 100 A-1 A-1 B-1 C-1 D-1 E-1 8 to 24 hrs 175 Yes- 100 A-1 A-1 B-1 C-1 D-1 E-1 22.5° i

1to4 Days 232 Yes - 100 A-2(40%) A-2(40%) B-2(40%) C-3(33.3%) D-3(33.3%) #-2(50%)

22.5° C-3(60%) C-3(60%) C-3(600'6) D-3(33.3%) E-2(33.3%) F-2(50%)

i E-2(33.3%) F-2(33.3%)

4 to 30 Days 232 Yes - 33 Some Meteorology As 1-4 Days 22.5°

Table 7-3 METEOROLOGY AND BREATHING RATES APPLICABLE DURING NORMAL LEAKAGE AND CONTAINMENT VENTING AS A FUNCTION OF DISTANCE - GE BASES Time Breathing Rate Sector Avg. Frequency Meteorology and Wind Speed (m/sec) As a Function of Distance (m)

(cc/sec) Meteorology Condition

(%)

300 500 800 1200 3000 7000 0 to 8 hrs 347 NO 100 Unstable 1 m/sec 8 to 24 hrs 175 Yes - 22.5° 100 Unstable 1 m/sec 1 to 4 Days 232 Yes - 22.5° 50 Unstable 3 m/sec (50"Ai)

Neutral 3 m/sec (50%)

4 to 30 Days 232 Yes - 22.5° 33 Unstable 3 m/sec (50%)

Neutral 3 m/sec(50%)

Y*,

..~**.

~ .

Table 7-4

- j - - - - - ~ ---

BASICCONDITIONS EVALUATED.WHICH WERE BASIS ~OB ~ADIOl,OGJCAL EVALUATION PARAMETRIC VALUE AND CASE NO.

  • PARAMETER II Ill IV vi v1 2

~- 1. Metal Water Reaction (%) 4 4 3 3 2 5

2. G(H 2 ) Pool 0.5 0.5 0.5 0.2 0.2 0.5
3. Max H 2 (%) 6 8 8 8 8 4
4. Gamma Energy absorbed by Coolant (%) 5 5 5 5 5 10
5. Inert No No No No No Yes
6. Fission Product Source GE AEC AEC AEC AEC AEC
7. Time Venting Initiated (Hr) 4.1 14 88 156 10
8. Vent Rate (SCFM) 34 74 41 10 9 52 1

GE-recommended hydrogen assumptions, as discussed in Question 4.

2 AEC-recommended values, as specified in question attachment .

7.5

(4827m), the maximum 30-day thyroid dose is 210 rem, while the cloud gamma dose is 3.6 rem, both of which are below the guidelines set forth in 10CF R 100. It is noted that the maximum 30-day thyroid dose exceeds 300 rem at the site boundary. It w.ill therefore be necessary to evacuate the area adjacent to the site boundary in the event that the radiation monitoring system indicates that a TID 14844 source term is present inside the containment.

Case No. Vl(AEC) in Table 7-4 was re-evaluated with an initial drywell oxygen concentration of 1% rather than 5%.

The time to vent was increased from 10 to 175 hours0.00203 days <br />0.0486 hours <br />2.893519e-4 weeks <br />6.65875e-5 months <br /> by this change. Correspondingly, the vent rate was decreased from 52 to 11 scfm. The doses corresponding to the 1% initial oxygen case would be similar to those calculated for Case V, which is the noninert case using the GE-recommended values tor* the key parameters. The differences are relatively insignificant between the two cases with the only practical implication being that the evacuation zone is slightly reduced from between the site boundary and 2200 meters for the 5% initial 0 2 case to between the site boundary and about 1100 meters for the 1% initial 0 2 case. Since all other cases (except case I, which used GE assumptions for fission products released from the core) require some evacuation outside of the site boundary, there is little advantage in reducing the initial 0 2 concentration.

1.3 CONCLUSION

S Based on the data presented in Tables 7-1 through 7-4 and Figures 7-1 through 7-5, the following conclusions can be reached:

1.
  • Using the fission product sources described in APED 5756 and the parameteric values presented in Table 7-4, Case I, the resulting off-site radiological exposures (i.e., Figure 7-5) are orders of magnitude below the guidelines set forth in.10CFR100.
2. Using the AEC Sources and recommended GE assumptions regarding hydrogen generation and percent metal-water reaction (i.e., Table 7-4, Case V) the resultant 30-day exposures are 78 rem thyroid and 1.3 rem whole body. These doses are due to the contribution from both normal leakage and venting.
3. The 2-hour site boundary dose, 35 rem thyroid and 1 rem whole body, using AEC assumptions is due entirely to normal leakage ( 1.6%/day). since venting is not required in the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> using AEC assumptions.
4. Using all of the recommended AEC assumptions (i.e., Table 7-4, Case VI) venting is initiated in 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. The 2-hour site boundary dose is the same as that presented in conclusion 3. The 30-day LPZ dose (4827m) is 150 rem thyroid and 2.4 rem whole body.
5. For the inerted cases, the effects of initial oxygen concentration (1 to 5%) has little effect on the resulting radiological exposures.

7.6

1. *POWER LEVEL=2550 MWt
2. NORMAL LEAKAGE (1.6%/DAY)
3. BASES-AEC ACTION GUIDE NO. 3 THYROID DOSE CLOUD GAMMA DOSE SE' UJ 0:: 10 1 UJ

"'c0 c

6 0::

c:

I-1 I

i DISTANCE (meters)

FIGURE 7-1 2-HOUR CLOUD GAMMA AND THYROID DOSE

1. GE ASSUMPTIONS
2. VENTING INITIATED AT 1 HOUR
3. PRI. CONT. LEAK RATE=l.6%/DAY
4. POWER LEVEL=2550 MWt
5. DOSE INCLUDES NORMAL LEAKAGE PLUS T'°'YROID DOSE CONT. VENTING CONTRIBUTION SE" UJ a:

~ UJ a:

UJ g

"'g o*.

10-4 10-2 i 0

a:

i::: CLOUD GAMMA DOSE C*

r- 0

..J 0

DISTANCE"" METERS FIGURE 7-2. 2-HOUR CLOUD GAMMA AND THYROID INHALATION DOSE

\~* >,.*,_

1. INCLUDES NORMAL LEAKAGE (1.6%/DAY)

PLUS VENTING CONTRIBUTION BASED ON AEC ACTION GUIDE NO. 3 POWER LEVEL= 2550 MWt 30 DAY DOSE VENTING INITIATED 4.1 hr

~

11.J Q::

11.J

"'0 10 hr c

c llf 0Q::

J:

I-88 hr

~156hr io3 10 5 DISTANCE !meters)

FIGURE 7-3 THYROID INHALATION DOSE

io2

1. INCLUDES NORMAL LEAKAGE (l.6% 1DAY)

PLUS VENTING CONTRIBUTION

2. BASED ON AEC ACTION GUIDE NO. 3
3. POWER LEVEL =2550 MWt
4. 30 DAY DOSE
Ii II.I 0::

II.I

~

0 101

  • ~

<.:l 0

0

_J

(..)

156 hr VENTING INITIATED 4.1 hr 10 hr 14 hr 88 hr 1~ .

. , 10 2 104 QISTANCE imeters)

FIGURE 7-4 CLOUD GAMMA DOSE

... ,.,... .. _____.. ~------**-------* --------*-******-*---- --* ---*-- --****------..:.- - ***- -------*--* ------- ---------- --****-----**----------*-*--*---~--*-*-**----- -*------- ---- *- *----4----* --****--- - *****-**---**-- -

e

1. GE ASSUMPTIONS
2. VENTING INITIATED AT 1 HOUR
3. PRI. CONT. LEAK RATE=l.6%/DAY
4. POWER LEVEL=1550 MWt
5. DOSE INCLUDES NORMAL LEAKAGE PLUS CONT. VENTING CONTRIBUTION UJ er l

UJ

i io-2 io-1i. 0"'

ILJ 0 a: I <(

UJ

! ~

~ <(

t'.l 0

0  ! 0 0a: 0

_J x

(..)

I-10-3 L..._ _ _ _ _ _ _ _..._......,_.__...._.......__..__........_.__ _ _ ___._ ___..___......___..__...._.....__.__ _...__ _ _ __.__ _ _ 10-2 2

10 DISTANCE (meters)

FIGURE 7-5 30-DAY CLOUD GAMMA MU> THYROID INHALATION DOSE

...... ~.- ;*~ .--...~....::;_.~::-

QUESTION 8

  • - Descrioe-any-changes-in *plant design- or operation-necessary to-permit-*venting -through-the* standby-gas-treatment- - *-

system as described in Amendment 24.

ANSWER

, In order 1.

to provide for venting, the following changes must be made:

Two flow control valves in series with optional bypass valves on each must be provided.

2. The flow through each will be read out on the main control panel.
3. These flow control valves and their bypass valves will be normally closed and will operate with keylock switches.
4. In order to vent, at least one of each parallel pair must be open.*

The flow rate will be pre-set and will be interconnected to a containment vent-makeup supply. If the containment is non inert, the makeup supply, controlled to the same rate as the vent, will be provided by a pair of flow control valves from the instrument air supply.

In the event that the containment is inert, the inert makeup must be provided by a redundant inert gas supply based on two liquid nitrogen storage containers. Each container will be kept pressurized at at least 60 psig and will provide enough gas to maintain vent flow for at least one week. It can be expected that refill from commercial source will be available at that time. Of course, this flow must also be controlled to equal the vent rate.

The containment atmosphere monitoring system will be added. This system is described in the answer to Question 1.

  • L

'I f

8.1

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