ML20207Q488
| ML20207Q488 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 01/31/1987 |
| From: | PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | |
| Shared Package | |
| ML20207Q481 | List: |
| References | |
| NUDOCS 8701270423 | |
| Download: ML20207Q488 (138) | |
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Safety Evaluation / Analysis Supporting I
Hydrogen Water Chemistry For Peach Bottom Atomic Power Station I
Units 2 and 3 I
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I January, 1987 Attachment Docket Nos. 50-277 s
50-278 Contents 1
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Philadelphia Electric Company Safety Evaluation for Hydrogen and Oxygen Storage Systems, Revision 1 I
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Stearns Catalytic Corporation Safety Analysis for the Liquid Hydrogen Storage System, Revision 1 3.
Stearns Catalytic Corporation Safety Analysis for the Liquid Oxygen Storage System, Revision 1 4.
Electric Power Research Institute Guidelines for i
Permanent BWR Hydrogen Water Chemistry Installations,
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March 1986 I
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9 MECHANICAL ENGINEERING DIVISION N2-1 2301 Market Street SAFETY EVALUATION FOR HYDROGEN AND OXYGEN STORAGE SYSTEMS, REV. 1 Peach Bottom Atomic Power Station, Units 2 & 3 FILE: GOVT l-1 (NRC)
REFERENCE:
- 1) Bolling Water Reactor Owners Group (BWROG),
" Guidelines for Permanent Bolling Water Reactor Hydrogen Water Chemistry Installations"
- 2) Stearns Catalytic " Safety Analysis for the Liquid Hydrogen Storage System"
- 3) Stearns Catalytic " Safety Analysis for the Liquid Oxygen Storage Systenf' I
SUBJECT:
This safety evaluation covers the cryogenic storage, vaporization, and gaseous storage of hydrogen and oxygen on-site at Peach Bottcm, as required to supply gaseous hydrogen and oxygen to the.. stat lon for the implementation of hydrogen water chemistry.
CONCLUSIONS:
The storage of hydrogen and oxygen on-site at Peach Bottcm for use in Hydrogen Water Chemistry does not involve safety related equipment.
The operation of the storage systems, including Ilquid hydrogen and I
oxygen storage and vaporization and hydrogen gas storage, will not affect safety related equipment. The location and use of the hydrogen and oxygen storage systems on-site at Peach Bottcm does not constitute an unreviewed safety question. This rrodification maintains the capability to safely shut down the plant in the event of a fire. A change to the plant's Technical Specifications is not required. A change to the UFSAR is not required, however, it will be revised to discuss these systems. This modification does not result in a significant reduction in the margin of safety. A significant hazard cc,nsideration is not required.
DISCUSSION:
Cryogenic 1Iquid hydrogen, IIquid oxygen, and gaseous hydrogen storage I
facilities are required at Peach Bott2n to supply hydrogen and oxygen gas to a hydrogen water chemistry system.
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, Oxygen Storace System:
The oxygen supply system consists of a cryogenic storage tank, an amblent air vaporizer and associated controls. The system will be installed at Peach Bottom, north of the Emergency Cooling Tower, outside of the plant security fence, on a concrete foundation pad. The I
cryogenic storage tank consists of an inner stainless steel vessel and outer carbon steel vessel, with the annular space evacuated and filled with thermally non-conducting material to provide the required insulation. The I
Inner tank is conservatively designed and tested to ASME Code requirements and is provided with a relief valve and a back-up rupture disc for overpressure protection. The outer tank is provided for thermal insulation only and is not designed to ASME codes. The 11guld oxygen flow is regulated through an ambient air vaporizer, with the rest.1 ting gas supplied to the station for use as part of a future hydrogen water chemlutry system. The system also incorporates provisions for temporary oxygen supply via trucks.
Oxygen is stored as a cryogenic 11guld at approximately 150 psig and - 300 F. Oxygen exists as a blue IIquid or a colorless gas. Oxygen is nontoxic and non-flanmable; however, it is a strong oxidizer.
Materials which burn in air will carbust more vigorously in oxygen.
The primary potential hazard associated with the storage of liguld oxygen is the potential for adversely affecting the station's level of I
fire protection. The design of the liquid oxygen storage tank provides protection against a major vessel rupture and subsequent large oxygen release, but an unusual accident, stx:h as a seismic event rupturing the vessel, is credible.
Cryogenic oxygen, both IIquid and gas, is heavier than air, so a large spill will disperse away frcm the tank along the ground. The oxygen will begin mixing with the surrounding air as it warms. The increased flarrmability of ccmbustibles in an enriched oxygen atmosr aere is a concern. A conservative value of 30% by voltme was chosen as the highest allowable oxygen concentration at any air intakes to safety related areas (normal air is 21% oxygen).
I Liquid oxygen tanks are widely used, including providing the oxygen gas to most hospitals, and vessel failure has been shown to be extremely infrequent and always acccmpanied by an external cause.
I Nevertheless, the 1Iquid oxygen tank at Peach Bottcm has been located l
such that, in the unilkely event of a ccmplete storage vessel failure, i
the oxygen concentration at safety related air intakes will not exceed l
the 30% by voltme criteria.
This determination is based on Figure 4-9 i
of reference 1, which was developed using the industry recognized l
DEGADIS tredel for heavier than air gas behavior. This model is
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appropriate for this analysis because cold oxygen gas is significantly I
denser than ambient air. This siting criteria will assure that the atmosphere within the station near safety related equipment will remain I
l well below the oxygen concentrations that would pose an increased flamnabil ity concern. Additionally, since no ignition sources or ccmbustibles are added, the probability of a fire near safety-related equipment is essentially unchanged.
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I. The oxygen storage tank is located outdoors, so any oxygen leakage, such as that from a pipebreak, will dissipate and is not a safety concern. Any failures of associated oxygen system equipment, such as piping or vaporizers, is enveloped by the rupture of the storage vessel. The foundation pad material is concrete, which does not burn and will not conbust even in the presence of pure oxygen. The I
storage system will be fenced and lighted, with barriers to prevent inadvertent contact with noving vehicles on-site. The location of the oxygen tank as well as control and location of ccTbustible materials is I
in accordance (and will be maintained in accordance) with NFPA 50, " Bulk Oxygen Systems at Constmer Sites".
The oxygen storage system will be designed to remain in place during the PBAPS design basis tornado wind (300 nph) to preclude the tank from falling nearer the station than the site analyzed in our evaluation.
Based on this design, the tank was analyzed for a I
canplete failure at its location (Ref. 2).
Based on the ability to tolerate such a failure and the fact that the BWROG guidelines (ref. 1) do not require the oxygen storage system to be designed for earthquakes, the liquid oxygen supply system need not meet seismic design criteria.
The referenced safety analysis (ref. 3) evaluates the siting of a large liquid oxygen tank at Peach Bottom as conpared to the guidelines developed by the BWROG (ref. 1).
Based on this analysis, we have concluded that the siting of the IIquid oxygen tank does not involve a significant reduction in the margin of safety, and therefore does not constitute an unreviewed safety question.
Based on the above discussion and on Reference 3, it is concluded that the location and operation of the liquid oxygen storage system as I
described is acceptable. The UFSAR need not be changed, however it will be revised to discuss this system.
The electrical power supply for the oxygen supply system will be covered separately.
Hydrocen Storace System Hydrogen will be stored as a cryogenic 1Iquid at approximately 100 psig and -425 F, in a cryogenic storage vessel consisting of an inner altmlntm vessel and an outer carbon steel shell. The annular space is evacuated and filled with thermally non-conducting material to provide l
the required insulation. The inner liquid hydrogen tank is designed and tested to ASME code requirements and is provided with redundant overpressure protection devices. These requirements include pressure l
testing to 1.5 times the Maximtm Allowable Working Pressure. A safety I
relief valve (set above the nonnal working pressure) and a rupture disc (set above the relief valve setting) protect the vessel from damage due to overpressure. The outer tank is provided for thermal insulation only and is not designed to ASME codes. The liquid hydrogen is pressurized to approximately 2500 psig by a cryogenic IIquid hydrogen, reciprocating type, ptmp.
The 11guld hydrogen is driven by the ptmp
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through an arrbient vaportzer bank, which discharges the resulting gaseous hydrogen to high pressure storage tubes, which will provide the hydrogen gas to the station. The high pressure storage tubes are also equipped with a pressure relief device. The system also incorporates provisions for temporary hydrogen supply via trucks.
The hydrogen storage system, including the tank, punps, outdoor vaporizers, storage tubes, piping, and controls will be located outdoors approximately 1700 feet northwest of the Unit 3 Reactor I
Building, 1180 feet frcm the offgas stack.
The equipment will be mounted on a concrete foundation pad with the tank, tank supports, and Interconnecting piping from the tank to a flow limiting device (valve I
or orifice), meeting PBAPS Design Basis Earthc,uake seismic design requirements as required by the BWROG "uldelines. The storage system, including tank, vaporizers, gas storagu tubes and associated controls, is designed to withstand the PBAPS design basis tornado wind which is 300 rrph.
The storage system design and siting is in accordance with NFPA 50A,
" Standard for Bulk Hydrogen Systems at Consuner Sites", and NFPA 50B,
" Standard for Liquifled Hydrogen Systems at Consuner Sites".
The storage of hydrogen on-site is a concern due to the carbustibility of hydrogen in air. The canbustion of hydrogen is exothermic, with a low activation energy required to initiate the reaction. Hydrogen, in air, has a lower flamnability limit of 4% by volume and an upper flamnability limit of 74.2% by volune.
Additionally, hydrogen is detonable in air, in confined spaces, at I
concentrations of frcm 18.2% to 58.9%. The quantity of hydrogen in the storage tank will be as much as 2.5 million standard cubic feet, which has an explosive equivalent (using industry accepted equivalence conversions which are utilized by the NRC in Regulatory Guide 1.91), if optimaliy vaporized and detonated, of approximately 14 tons of TNT.
Additionally, this quantity of hydrogen, if burned rather than exploded, would form a fireball which would create significant thermal I
fluxes.
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The location for the hydrogen storage facility at Peach Bottom, j
was chosen to provide adequate distance frcm the station so that, in the unlikely event wherein hydrogen is released, no resulting events would have a significant adverse effect on any safety related structures, including the offgas stack, l
AlthougF the possibility of detonation was considered, an unconfined detonation is extremely unlikely. As deta!1ed in *.he referenced safety analysis, all docunented, unconfined hydrogen spills in the presence of an Ignition source, to date, have burned, but have not exploded. Additionally, for the analysis which considered large l
spills due to major vessel failure, it was determined (per Reference 1) that any ccrrhustion, whether a fireball or an explosion, would take place at the tank site and would not drift near the plant cr the offgas stack before ccmbustion. This determination was made on the basis of the very low activation energy C.019 millljoules) required to initiate the hydrogen / oxygen reaction. A review of the storage tank design and the tank's overpressure protection devices concluded that any accident which l l
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I was capable of rupturing the vessel would be the result of external causes, such as aircraft crashes or tornado misslies. These events would be accompanied by sparks, high temperature material, or in the case of tornado misslies, static electricity, which would contain, considering the low activation energy of hydrogen centustion, sufficient energy to ignite the release.
In an unconfined area, such as the hilltop where the tank is located, a fireball is the nest probable result if a large quantity of hydrogen was released. A fireball consists of a cloud of hydrogen vapor. The concentration of hydrogen in the cloud varies frcm the surface to the center. Scme volune of gas at the surface of the cloud is in the flarrmable range. The internal hydrogen thus feeds a large fire on the exterior of the volune. As detailed in the BWROG guidelines (ref.1), the fireball resulting from such a large spill would last in the range of 3 to 9 seconds. The thermal flux at the station, or the offgas stack, would be less than half the heat input required to ignite wood; values this low would have little effect on reinforced concrete structures.
As previously stated, the detonation of hydrogen gas in an unconfined, outdoor location is improbable (no record of unconfined hydrogen / oxygen mixtures detonating is available); however, for h
conservatism this evaluation also considered the shock wave the station would receive due to the detonation of the entire tanks contents at the
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storage location. The calculations utilize an Industry accepted method I
for converting ccmbustible gas explosions to TNT equivalence, as recognized by the NRC in Reg. Guide 1.91.
A maximun pressure pulse of approximately 1 psig peak overpressure, which is below the 6 psig threshold value for partial demolition of brick buildings, would be I
received by the station. As detailed in reference 1, the 6 psig value for partial denoliticn of brick buildings was detennined using a data base of buildings damaged during World War II from various bcnb sizes at various' distances. Overpressures of this magnitude would have little effect on reinforced concrete structures at Peach Bottcm which are designed for 300 mph tornado wind loads. Additionally, an
,g independent review using a method recognized by the NRC (NUREG/CR-2462) j
'E for calculating safe standoff distances frcm explosions was performed.
This method is inherently trore conservative because the response of the Reactor Building to the pressure pulse is considered. The results of lBg this evaluation, as detailed in Appendix A of Reference 2,. require the tank to be sited approximate!y twice the distance frcm the station and offgas stack required by the initial analysis, or approximately 600 feet. As mentioned previously, the PBAPS tank siting meets this requirement.
Accidents which result in the failure of the IIquid hydrogen tank i g will provide sufficient energy to ignite the release. The storage
!E system 9aseous piping, IIquid piping after the flow limiting device, i
vaporizers, punps and gas storage tubes, are non-seismic and could lI fall due to an earthquake, without an external ignition source present.
This would permit a non-Ignited cloud to drift towards the station.
The storage system is sited considering the failure of any of these non-seismic components. Such failures are enveloped by the failure of lI l
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1 the largest pipe line containing liculd or gaseous hydrogen. Therefore, the system's location insures that the flanmable hydrogen /alr mixtures
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(hydrogen concentration between 4 and 74.2% by volune) created would not pose a hazard to safety related equipment due to the intake of an enriched hydrogen mixture. The referenced safety analysis (Reference 2),
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determined that, even in the worst case scenario where either a 2" high I
pressure gas line or a 3/8" liquid hydrogen Iine (liquid hydrogen supply lines shall have flow limiting devices that control hydrogen discharge to this equivalent flow), failed in the direction of the station, the concentration of hydrogen at any safety related air intake is well below 4% by volune which assures that. hydrogen concentrations within the plant will remain well below hazardous levels. The storage system is I
seismically designed up to the flow limiting devices to assure that releases will be limited to only those analyzed.
This determination was made using a jet dispersion model (for high pressure gas release) assuning the nost conservative environmental conditions of a calm, still day with the Ilght wind in the station direction (Gaussian dispersion, F weather stability). The quantity of hydrogen that would be released by the actuation of a pressure relief device is enveloped by the pipeline break analysis.
This analysis of hydrogen concentration versus distance also shows that the combustion of such a gas or liquid pipellne release outdoors I
at the tank site is not a concern because the hydrogen released will not be in the ccntustible concentration range (greater than 4%) at the station. The ccmbustion of the dispersing hydrogen cloud due to a pipeline break, unlike the fireball caused by a large hydrogen release, is very short and produces insignificant thennal fluxes to surrounding areas. Since the burning cloud would not be located at the station or I
the offgas stack, no adverse impact on any plant structures would result.
The referenced safety analysis (Ref. 2) evaluates the sitira of the liquid hydrogen storage system at Peach Bottcm. The referenced analysis uses as its basis the guidelines (ref. 1) developed by the Bolling Water Reactor's Owners Group (BWROG). Based on this evaluation it has been determined that the siting of a liquid hydrogen storage facility does not involve a significant reduction in the margin of safety. This nodification does not constitute an unreviewed safety questlon.
Based on the above discussion and on Reference 2, it is concluded that the location and operation of the liquid hydrogen system as I
described is acceptable. A change to the UFSAR is not required, however, a revision will be made to describe this system.
I The electrical power supply to the hydrogen storage system will be evaluated separately.
GENERAL:
The transportation of hydrogen und oxygen on-site was also evaluated in accordance with the same criteria for the storage systems. Deliveries of hydrogen and oxygen will vary cepending on usage but are expected to range frcm daily to nonthly. The supply tank trucks are of simitar design as the
, I pennanent vessels. The supply tank trucks also hold less hydrogen or oxygen than that analyzed for the storage systems and will be at the plant site only during deliveries. Deliveries will be scheduled such that at no time will the total quantity of hydrogen, including storage tank and delivery truck, be greater than that analyzed (see above discussion) for Peach Bottan.
Additionally, the supply trucks will ccme no closer to the station than the storage system sites. Thus it is concluded that the potential hazards of on-site transportation are enveloped by the analyses for the permanent storage systems.
The hydrogen and oxygen supply systems are each equipped with a low temperature switch downstrean of the vaporizers. The switch will I
shutoff flow to prevent the inadvertent injection of cryogenic gas or 11guld which could damage station equipment or materials.
Due to the separation distance between the hydrogen and oxygen storage facilities (greater than 1000 feet) an evaluation of simultaneous storage site accidents is not required.
The following docunents have been reviewed in the performance of this safety evaluation:
PBAPS UFSAR Sect. 2, 12, 10CFR50, NRC Reg.
Guide 1.91, and NUREG/CR-2462.
10CFR50.59 CHANGES, TESTS AND EXPERIMENTS:
1.
The location of hydrogen and oxygen facilities at Peach Bottom does not involve an unreviewed safety question.
A.
This nodification does not involve a significant increase in the probability or consequences of an accident or malfunction of equignent important to safety previously evaluated in the safety analysis report.
This modification invokes the Installation of new equipment that will be physically located exterior to the station. Existing station equipment or procedures are not affected by this modification; therefore, the I
siting of oxygen and hydrogen storage systems at Peach Bottcm does not increase the probability or consequences of an accident previously evaluated.
B.
The rrodification does not create the possiollity of an accident or malfunction of a different type than any previously evaluated in the safety analysis report.
I This modification involves the installation of new equipment exterior to the station. Hcwever, the hydrogen and oxygen storage facilities have been I
located at sufficient distances frcm the station such that no credible accidents could have adverse effects upon the station or any safety related equipmen't in
. excess of any effects previously analyzed. This I
includes consideration of all accident scenarios Included in the UFSAR.
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C.
The modification does not reduce the margin of safety as defined in the basis for any technical specification.
The hydrogen and oxygen storage facilities have been located at sufficient distances from the station so that no credible accidents could have adverse effects upon the station or any safety related equipment in I
excess of any effects previously analyzed. This includes consideration of all accident scenarios included in the UFSAR. Additionally, there are no technical specifications concerning the hydrogen and oxygen storage facilities.
2.
A change to the Peach Bottom Technical Specifications is not required. There are no Technical Specifications applicable to these systems.
10CFR50.92 SIGNIFICANT HAZARDS DETERMINATION:
A Ilcense amendment is not required, therefore a significant hazards determination is not required.
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Prepared by:
Ge[N. bb 8!s t./P7 Date:
Reviewed by:
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' Interfacing Section (Civil Section Head) f alf'L A d s Y _l___
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Engineer-in-fthargeNES
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S. J. Kowalski S. R. Roberts L. B. Pyrih J. W. Austin A. R. Lewis B. E. Edwards P. K. Pav11 des W. C. Birely T. E. Shannon G. A. Hunger I
C. Caprara C. B. Patton D. R. Helwig ISEG Engineer (PB)
D. Marano R. J. Scholz R. A. Mulford P. A. Tutton I
G. T. Brecht J. F. O'Rourke W. J. Mindick D. A. Anders G. M. Leitch C. M. Cooney R. S. Fleischmann W. M. Alden F. W. Polaski DAC (NG-8)
F. J. Mascitelli
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I PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION SAFETY ANALYSIS FOR THE LIQUID HYDROGEN STORAGE SYSTEM Revision 1 September 24, 1986 I
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Prepared by Stearns Catalytic Corporation I
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P.T. Reichert Supervisor Licensing I
and Nuclear Analysis W'H J
/V G. T. 6eeley F
Manager, Nuclear Systems h d) l D.M.Giofgione Project Manager dW&
R. E. Basso Manager, Nuclear Technology I
g 300es
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TABLE OF CONTENTS I.
INTRODUCTION II.
DESCRIPTION OF LIQUID HYDROGEN STORAGE SYSTEM III.
SCENARIOS FOR POTENTIAL HYDROGEN RELEASE IV.
GENERAL BEHAVIOR OF HYDROGEN RELEASES ll V.
DESIGN CRITERIA RELATED TO HYDR 0 GEN RELEASES c
VI.
HYDROGEN RELEASE CONSEQUENCE ACCEPTABILITY i
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REFERENCES LIST OF FIGURES FIGURE 1 SITE PLOT PLAN FIGURE 2 HYDROGEN VS. METHANE IGNITION ENERGIES I
FIGURE 3 MINIMUM REQUIRED SEPARATION DISTANCE VS. HOLE SIZE AND ID OF PIPE FOR GASEOUS RELEASES FROM 150 PSI LIQUID HYDROGEN STORAGE TANK I
FIGURE 4 MINIMUM REQUIRED SEPARATION DISTANCE VS. HOLE SIZE AND DISCHARGE RATE FOR LIQUID RELEASES FROM 150 PSI LIQUID HYDROGEN STORAGE TANK F WEATHER STABILITY, 1 M/S WIND VELOCITY.
FIGURE 5 MINIMUM REQUIRED SEPARATION DISTANCE VS. LIQUID HYDROGEN STORAGE TANK SIZE FOR INSTANTANEOUS RELEASE OF ENTIRE TANK CONTENTS AND EXPLOSION AT TANK SITE F WEATHER STABILITY.
I FIGURE 6 THERMAL FLUX VS.
DISTANCE FROM FIREBALL CENTER FOR LIQUID HYDROGEN STORAGE SYSTEM I
APPENDIX A CAPABILITY OF SAFETY RELATED STRUCTURES TO WITHSTAND BLAST I
LOADINGS APPENDIX B IMPACT ON TRANSMISSION EQUIPMENT IN VICINITY OF HYDROGEN STORAGE SYSTEM
I.
INTRODUCTION This safety analysis of liquid hydrogen storage is intended to support the license amendment to permit liquid hydrogen to be stored on site.
The hydrogen will be stored in a liquid hydrogen storage tank of 20,000 gallons or less.
A.
Purpose of this ReDort The purpose of this report is to establish the acceptability of the chosen site for the liquid hydrogen storage facility.
The determination of the acceptability is based upon application of the criteria from EPRI-NP-4500-SR-LD, " Guidelines for Permanent BWR Hydrogen Water Chemistry installations", by the BWR Owner:
I Group for IGSCC Research, March 1986 (Reference 1).
The Peach Bottom Atomic Power Station (PBAPS) liquid hydrogen storage system will meet all appropriate guidelines provided by Reference 1.
I This report provides the basis for compliance with the liquid hydrogen storage guidance given in Reference 1.
B.
Structure of this Report Section II of this report describes the liquid hydrogen storage system for PBAPS.
The actual hydrogen supplier has not yet been cnosen.
The liquid hydrogen storage system will be provided by a supplier with extensive experience in the design, operation, and maintenance of hydrogen storage and supply systems.
This report (Section III) also develops possible event scenarios--both man-made and natural, as well as both onsite and offsite--that could damage the hydrogen storage system and lead to hydrogen releases.
The general behavior of released hydrogen is described in Section IV.
This behavior, along with a review of causal events, is used to develop general design criteria for the hydrogen storage system (Section V).
These general design criteria are consistent with EPRI-NP-4500-SR-LD.
The general design criteria in EPRI-NP-4500-SR-LD are the result of a series of release event consequence analyses that are a I
function of distance f rom the storage system.
These analyses were i translated into a series of curves for safe standof f distances as a function of certain storage system design parameters.
This I
report evaluates the credible release scenarios and uses the applicable EPRI-NP-4500-SR-LD curves to assure that the storage.
system location is appropriate (Section VI).
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Conclusions This report provides the basis for concluding that:
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A safe location has been established for the liquid hydrogen storage system.
The safety of this storage system site has been determined based on the relative location of other Peach Bottom equipment; and the ef fects of the normal, abnormal, and accident conditions which might occur at the storage location.
The ef f.ects on the hydrogen storage system of the design basis external events used for safety related equipment (such as tornados and earthquakes) have also been' l
considered.
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The liquid hydrogen storage facility is designed and can operate safely without preventing safety-related structures and equip',nent f rom performing their design functions.
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II.
DESCRIPTION OF LIQUID HYDROGEN STORAGE SYSTEM A.
System Design
I The liquid hydrogen will be stored in a liquid hydrogen storage tank.
This tank consists of an inner vessel meeting Section VIII, Division 1 of the ASME Code for Unfired Pressure Vessels; and an outer " vacuum jacket" vessel, with the space between filled with
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insulation and evacuated.
Liquid hydrogen will be pumped from the tank to ambient vaporizers to produce gaseous hydrogen for plant use.
EPRI-NP-4500-SR-LD, Section 3.2.2 provides additional details
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rega rding the design of liquid hydrogen storage systems.
The I
PBAPS system will meet all of the design requirements of EPRI-NP-4500-SR-LD, Section 3.2.
B.
Sitina The storage system location is shown on Figure 1.
The storage system is within the site boundary, with access controlled by a locked gate.
It is within its own locked fence as well.
The route to be taken by liquid hydrogen delivery trucks is also shown on Figure 1.
Delivery trucks will never approach closer to I
safety-related equipment than the storage site.
The liquid hydrogen storage system will be located 1180 feet away from the nearest safety related structure, which is the plant stack.
The next nearest safety related structure is the Unit 3 reactor building which is 1700 feet away.
The nearest safety related air intake is for dilution air at the plant stack which is 1180 feet from the liquid hydrogen storage system.
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III. SCENARIOS FOR POTENTIAL HYOROGEN RELEASE A.
Hydrogen Storace System SDecific Events EPRI-NP-4500-SR-LD includes several special requirements above and beyond normal industry practice and ASME code requirements.
These requirements deal with longitudinal weld radiography and overpressure protection.
These added requirements were instituted based upon fracture mechanics analyses and overpressure protection reliability analyses, r,espectively, which were done in support of the Dresden HWC design (Reference 2).
These added features are considered suf ficient to render the possibility of vessel failure by detected ~ or undetected crack growth, or by overpressure protection system failure, to be of such a low probability as to be negligible.
The only normal operation of the storage system where hydrogen can be released to atmosphere would be when the station is not using hydrogen.
Then, af ter a few days, the normal heat transfer f rom the ambient air will vaporize enough liquid to require controlled venting of the tank.
The vent rate would be on the order of 0.002 lbs./sec., intermittently.
Abnormal occurrences resulting in hydrogen releases, which are I
unlikely but might occur over the life of the storage system, are
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related to the operation of overpressure protection devices.
The peak vent rates associated with the worst case f ailure would be about 8 lbs./sec.
These normal and abnormal hydrogen release events will not impact the hydrogen storage system, or other Peach Bottom safety related or non-safety related equipment.
This is the case whether or not the release were to be ignited.
As shown in Reference 3,
these events are less limiting in determining storage system siting than those associated with the failures discussed in Section III due to severe natural phenomena. Therefore, they are not evaluated further.
B.
Site Characteristics and Site-Related Events The site characteristics and site-related events important to the safety of the liquid hydrogen storage system are:
(1) the location of the hydrogen storage facility relative to I
safety-related structures and equipment; (2) the site-related characteristics that protect the storage area, and; (3) the control of hydrogen deliveries onsite.
3006S Page 6 of 23
1.
Location Figure 1 is the site plot plan showing the location of the hydrogen storage area.
The liquid hydrogen storage system will be located 1180 feet away from the nearest safety-related structure, which is the plant stack.
The next nearest safety related structure is the Unit 3 reactor
- building, which is 1700 feet away.
The nearest safety-related air intake is at the plant stack.
In order to protect the hydrogen storage area from any potential vehicle accidents, truck barriers are installed entirely ~ around the hydrogen storage facility.
The approach road will be such that the delivery trucks will approach I
along the side of the storage area.
The approach road is not a public road and is a route for only minimal plant traffic.
2.
Security for Storage Area The storage area is inside the site boundary.
The road leading to the approach road has a
locked gate.
An additional locked fence also surrounds the hydrogen storage area, as required by NFPA 508.
3.
Fire Protection There are no flammable materials stored near the hydrogen storage site.
The system and its siting will meet NFPA requirements.
The design basis for the overpressure protection systems for the liquid hydrogen storage tank assumes a hydrocarbon fire beneath these vessels.
Thus external fires do not cause vessel failures.
The hydrogen release through the relief devices may or may not be consumed in the fire, but in any case, would not impact other Peach Bottom safety related or non-safety related equipment.
An external fire cannot cause a fire or detonation within the tank because of the absence of oxygen in the tank.
Ignition of relief valve dinharges is possible, though not generally expected except in ths case of an external fire.
The preferred and most practical practice for extinguishing ~
I hydrogen fires, as stated in NFPA 50A and SOB, is simply to isolate the hydrogen supply.
Even if the hydrogen supply' cannot be isolated, the fire will simply burn until the hydrogen is exhausted.
This will have no impact on plant safety-related or non-safety related equipment.
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4.
Control of Construction Activities I
No construction activity of any kind is presently contemplated in the vicinity of the hydrogen storage system.
Any such construction wculd undergo a safety review to confirm that the hydrogen storage system would be unaffected.
5.
Hydrogen Delivery and Of fsite Hydrogen Transportation Figure 1 shows tha route taken by the liquid hydrogen trucks through onsite areas.
The hydrogen delivery trucks approach no closer than the storage area to safety-related equipment, and contain less hydrogen than the maximum sized storage tank.
Therefore, the analyses of tank f ailures control the location of the storage area.
The liquid hydrogen delivery containers are of similar construction, and have similar overpressure protection systems, to that of the storage tank, except that the contents of the truck is less than that of the storage tank.
One hydrogen supplier (Reference 4) reported that in more than 51,000,000 miles of delivery truck mileage a total of 6 serious accidents (truck roll-overs) had occurred; ano that none of these accidents resulted in a liquid hydrogen spill, or a loss of vacuum between the inner and outer shells.
Based upon the above discussion, the likelihood of a
delivery-related accident is very small.
6.
Conclusions About Site Related Even,tji, No site-related releases other than relief device action due to potential fires are postulated.
This type of fire is considered a system-specific event, the ef fect of which is enveloped by more serious events discussed below.
Based on the excellent history of liquid hydrogen transportation, the possibility of a transportation related accident is very remote.
Because the hydrogen delivery trucks approach no closer to the plant than the storage area and contain less hydrogen than the maximum sized storage tank, the analyses of tank failure are considered limiting on the location of the storage area.
For these reasons, no transportation-related hydrogen release is postulated.
(
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C.
External Events A set of external events was used as the basis for licensing th@
original plant and is described in the PBAPS FSAR.
These events I
have been considered to determine if any of them have the potential for causing a release of liquid hydrogen from the storage tank.
These events include natural phenomena and of f site industrial hazards.
For compa rison, the way each event was i
treated in the FSAR is given first, followed (if applicablt) by the evaluation of the. event in light of the hydrogen storage system.
1.
Earthquake a.
Plant Design Basis The seismic design for safety-related structures and equipment for PBAPS is based on dynamic analyses using I
acceleration or velocity response spectrum curves which are based on a horizontal ground motion of 0.12g; a vertical acceleration equal to 0.089 is assumed to occur simultaneously.
b.
Hydrogen Storage System Design The liquid hydrogen storage tank and supporting
~
structures will be analyzed for seismic loads using a static equivalent method.
The liquid hydrogen storage I
tank and supporting structures will be capable of withstanding a seismic event of the magnitude used in plant safety-related system design.
Therefore, the safe I
shutdown earthquake will not cause f ailure either of the liquid hydrogen tank or of its supporting structures, and a seismic event will not cause a large release of liquid hydrogen.
Piping containing liquid hydrogen may not all be designed to withstand the safe shutdown earthquake for PBAPS.
For I
non-seismic portions of such piping, a break caused by an earthquake would be postulated.
The amount of hydrogen released due to such events will be restricted to an I
acceptable level if necessary by the use of seismically-supported excess flow check valves or by other flow-limiting devices.
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2.
High Winds. Tornados, and Tornado Missiles a.
Plant Design Basis i
The design basis for PBAPS safety-related structures is a tornado with 300 miles per hour winds.
Design basis tornado missiles are a 12 foot x 4 inch x 12 inch board traveling at 300 miles per hour striking end on, and a I
4000 pound automobi.le propelled at 50 miles per hour.
The safety related structures are also designed for a 3 psi pressure differential caused by a tornado.
In the case of the plant stack and reactor building above the refuel floor, these structures and equipment therein I
are not required in order to acnieve safe shutdown following a tornado.
Therefore, they are not designed to withstand tornado effects.
b.
Hydrogen Storace System Design The liquid hydrogen storage tank and supporting h
structures will be designed to withstand the loads E
associated with tornado winds of 300 mph.
Therefore, tornado winds will not cause any tank failures.
The tank is not capable of withstanding the design basis tornado missiles.
Therefore, a tornado missile could rupture small lines, or the storage tank and cause a large spill of liquid hydrogen.
The tank failure is most limiting.
The effects of a large spill of liquid hydrogen are discussed in Section~IV.
3.
Flood
^
The hydrogen storage facility is 215 feet above the design basis flood level for the P8APS Site, and flooding will have no effect on the storage area. ' Topography at the hydrogen storage site is such that local floMing is not a concern.
4.
Offsite Industrial Hazards l-There are no of f site industrial hazards deemed of suf ficient risk to require consideration in the design of the PBAPS.
The same conclusion is applicable to the hydrogen storage area.
5.
Toxic Chemicals 1
Toxic chemicals considered in PBAPS design basis will not affect the material strength of the liquid hydrogen storage facility.
Toxic chemicals that would affect operator I
personnel would not affect the liquid hydrogen
- system, because no operator ac. tion is required for hydrogen storage system operation.
Therefore, no failure of the hydrogen storage system due to toxic chemicals can occur that could lead to hydrogen releases.
g 3ms Page 10 of 23 I
6.
Ai rc ra f t a.
Plant Design Basis An evaluation of the potential hazard f rom aircraf t in the vicinity of the PBAPS plant is contained in the FSAR.
The conclusion of this evaluation is that the probability of an airc ra f t crashing into the PBAPS is suf ficiently low that aircraf t impact is not considered a design basis event.
b.
Hydrogen Storage System Design The evaluation of aircraft hazard for the plant is I
equally applicable to the hydrogen storage area, except that the hydrogen storage presents a smaller target area than the plant.
Therefore, the probability of aircraf t impact is even smaller for the hydrogen storage facility.
7.
Lightning The hydrogen storage system will be protected from the effects of lightning per the requirements of NFPA 78.
No hydrogen releases will be caused by lightning.
I 8.
Conclusions on Releases Caused by External Events Based on the above evaluations, the conclusions are:
a.
No hazards associated with of fsite industrial facilities I,
or transportation routes will cause any hydrogen releases.
b.
No accidental hydrogen releases are expected due to onsite PECO activities.
Nonetheless, the overpressure
+I protection system is designed to accommodate a fire directly under the storage vessels.
The ef fects of any overpressure system related release would be less than I
those associated with those caused by severe natural phenomena.
c.
The only natural phenomena with potential for causing a release of hydrogen are tornado missiles, which could.
rupture small lines containing hydrogen or create a hole in the tank, and a seismic event, which could break small piping connected to the tank.
d.
The ef fects of system normal (very small) and abnormal operation releases of gaseous hydrogen are enveloped by E
releases caused by severe natural phenoraena.
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IV.
GENERAL BEHAVIOR OF HYOROGEN RELEASES I
The conceivable hydrogen release events discussed in Section Ill are of three general types:
(1) small releases of gaseous hydrogen f rom the liquid storage tank related piping or relief devices at a
- specific, I
determinable mass flow rate (2) small releases of. liquid hydrogen from the liquid storage tank related piping at a specific, determinable mass flow I
rate, and (3) large releases of substantially all the liquid tank contents nearly at once.
Hyd.rogen release may behave in any of three ways:
(1) dispersion due to momentum, thermodynamics, and/or meteorology (2) ignition resulting in a fireball type combustion, or (3) ignition resulting in detonation.
I When mixed with air, hydrogen gas is flamable and potentially explosive.
When hydrogen is released from the storage
- system, atmospheric processes and any fluid momentum contribute to the dilution and dispersion of the hydrogen.
A hydrogen release will I
dilute first below the upper flammability limit (75%) and eventually below the lower flamability limit (4%).
Between 75% and 4% there is a potential for ignition of the hydrogen air mixture, which would I
result in a fireball type combustion.
Between 18.3% and 59% the potential for cloud detonation also exists under some conditions.
1 This section of the report describes these types of behavior of releases of gaseous or liquid hydrogen.
A logical result of this discussion is the identification of design criteria for locating a hydrogen storage system, such that the behaviors discussed in this I
section do not present unacceptable consequences to safety-related structures. Such criteria are given in Section V of this report.
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A.
Dispersion Behavior of Hydrogen Releases I
Releases from the parts of the liquid hydrogen storage system containing gaseous hydrogen have substantial momentum and I
relatively small volume such that they are fairly rapidly dispersed.
EPRI-NP-4500-SR-LO uses a jet dispersion model to determine the associated dispersion.
This model is discussed in i
Reference 3,
Section V.B.
Releases from the portions of the liquid hydrogen tank containing gaseous hydrogen are not as restrictive on the location of the storage area as other events.
I Releases f rom the parts of the storage system containing liquid hydrogen will result in a liquid jet that will either flash to vapor due to its superheated condition or evaporate rapidly upon E
hitting the ground.
The resulting vapor has a low momentum.
W Gaussian dispersion models are considered the most appropriate way to model this type of release.
The plume will be at or near neutral buoyancy and is assumed to disperse at or near ground level.
B.
Hydrogen Ionition Behavior I
Air Products and Chemicals, Inc. ( APCI) has conducted a review of all known sources of liquid hydrogen spill events.
This review is I
given in Reference 3.
APCI's conclusions from these events regarding ignition were as follows:
(1) vessel rupture was not shown to be a reliable source of I
ignition (only 3 out of 10 vessel ruptures resulted in ignition).
I (2) liquid hydrogen releases did not have a
tendency to auto-ignite.
There were identifiable sources of ignition for each case that ignited.
(3) for the 79 tests where liquid hydrogen was released and ignition sources were intentionally provided, ignition always occurred without detonation.
During spill tests in which ignition sources were not.
intentionally provided, spurious potential ignition sources were h
deliberately avoided.
In normal industrial settings, this i s.
E likely not to be the case.
In other words, ignition sources are l
more likely to exist.
Potential ignition sources include flame, I
electrical, static or friction sparks, and anything above the auto-ignition temperature of hydrogen (9320F at 1 atm).
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l A literature search located no studies of the likelihood of 5
ignition in the vicinity of liquid hydrogen spills.
- However, hydrocarbon (e.g.
methane) ignition data can te used as a conservative measure of this likelihood.
James (Reference 5) examined records of the distance traveled by hydrocarbon vapor clouds in 81 rail car spills where ignition occurred.
It was found that 58% ignited within 50 feet, 7 5".
ignited within 100 feet, and all ignited within 300 feet.
When we compare hydrogen and methane ignition, we find that:
(1) minimum energy required to ignite hydrogen is less than 7% of that required to ignite methane (2) the hydrogen auto-ignition temperature is 250 4 lower than that of methane, and (3) hydrogen has a flammability range of 4 to 75% compared with 5 to 15% for methane.
Minimum energies for spark ignition as a function of concentration of methane and of hydrogen in air are given in Figure 2 (taken from Reference 6).
The curves clearly illustrate the much broader I
region for hydrogen ignition than that for rethane.
'he minimum ignition energies for hydrogen and for methane are 0.019 and 0.28 millijoules, respectively.
For comparison, 1.0 millijoule is the I
minimum spark energy that can be felt by humans (i.e., the human shock threshold).
In other words, hydrogen can be ignited by a spark having less than one fif tieth of the energy of the static electricity one might feel when touching a door knob.
C.
Hydrogen Detonation Behavior I
The APCI review of hydrogen spill data in Reference 3 and the physics of detonation of flammable gases resulted in the following conclusions:
"As the test data have shown, no detonation of an unconfined liquid hydrogen spill has occurred.
The unconfined conditions for F
these tests were mostly flat ground with only a shallow diked area and instrument towers as obstructions.
It is well known that when flanrnable hydrogen-air mixtures are totally confined (e.g., a lon'g pipe with closed ends) ignition can result in detonation.
No i I quantitative data was found on the propensity of semi-confined liquid hydrogen spills to detonate or not detonate.
A 1958 A. D.
Little report qualitatively discussed a test where liquid hydrogen l
spills were semi-confined by three walls of a test bay.
The i
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statement is made that
'even partial confinement can add I
substantially to the magnitude of the pressure wave generated by the combustion of gases in free space'.
It is also well known that objects immersed in a combustible vapor cloud can act as turbulence generators.
These can cause acceleration of the I
burning velocity which could run up to a detonation.
These considerations suggest that the possibility exists for the formation of a ' pressure wave' if ignition is delayed and the I
vapor c.-"
drifts in an environment that could provide
~
acceleratec combustion."
D.
Hydrogen Release Behavior for the Hydrogen Storage System The facts given above (and -elaborated in Reference 3) about the general behavior of hydrogen releases lead to several logical I
observations.
(1) following any liquid spill resulting from violent disruption h
of the liquid hydrogen storage system, ignition near the site 5
of the spill is considered very likely.
I (2) ignition of an unconfined cloud would be expected to result in a fireball (3) detonation may be possible in a semi-confined cloud, or a I
cloud in the vicinity of turbulence-generating structures or equipment that might be in relatively open surroundings I
(4) hydrogen vapor clouds drif ting between or being taken into structures by HVAC systems present some risk of detonation.
(5) hydrogen releases through a pressure control valve, or relief I
device generally do not ignite, although there have been cases where they have.
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V.
DESIGN CRITERIA RELATED TO HYOROGEN RELEASES A.
Consideration of Release Events i
Af ter reviewing the hydrogen behavior presented in Section IV, one can identify three scenarios following a release of hydrogen that could be unacceptable if not properly addressed using suitable design criteria.
Those scenarios are:
(1) if a hydrogen vapor cloud ignited where a fire could damage safety-related equipment (2) if a hydrogen vapor cloud ignited with a run-up to a detonation, where resulting blast overnressures could damage safety-related equipment, and (3) if a hydrogen vapor cloud could drif t to where it could be taken in by plant ventilation equipment or other equipment requiring an air supply B.
Design Criteria The following design criteria provides adequate protection for saf ety-related structures from the three scenarios given above.
(1)
Prevention of Releases The potential for releases of liquid or gaseous hydrogen must I
be minimized to the extent practical by design of the hydrogen storage system and the equipment utilized for its prote: tion.
(2)
Protection from Fireball The distance f rom the tank to safety-related structures must I
be such that a fireball type of combustion at the spill site, which is the most likely consequence of a large spill, will not prevent safety-related structures f rom performing their design functions.
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(3)
Protection from Detonation Even though detonations of unconfined hydrogen clouds have not occurred, the distance f rom the tank to safety-related structures must be sufficient to assure that complete tank f ailure and detonation of the tank contents in the detonable concentration range, at the spill site, will not result in I
l peak overpressures that would prevent those structures from i
W performing their design functions.
I (4)
Prevention from Hydrogen Accumulation Near Safetv-Related EauiDment For any hydrogen release, either early ignition of the resulting cloud must be sufficiently likely that the cloud will not reach any plant air intake system, or such releases must be out of the flarrynable range due to dilution in the I
distance from the point of release to safety-related structures or plant air intake system.
C.
RelationshiD of Design Criteria to EPRI-NP-4500-SR-LD Guidance Criterion 1 -- Prevention of Releases:
I EPRI-NP-4500-SR-LD provides guidance for the design of liquid hydrogen supplies which meets and exceeds industry standards f or the associated equipment.
EPRI-NP-4500-SR-LD recommendations for I
protection of storage equipment and safe handling of liquid hydrogen by experienced suppliers make abnormal hydrogen releases very unlikely.
In f act, only some of the most severe natural phenomena used as the design basis for safety related equipment are expected to have the potential for causing significant hydrogen releases.
Therefore, Criterion 1 is met by use of the EPRI-NP-4500-SR-LD guidance.
Criterion 2 -- Protection from Fireball:
EPRI-NP-4500-SR-LD provides analyses of fireball durations and' I
heat fluxes assuming that the entire tank contents are involved.
These results can be used to establish that the distance from the' hydrogen storage area to the safety-related structures is sufficient to protect safety-related equipment.
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200eS
, age n ef 23 I
The details of this type of analysis are discussed in Reference 3.
l l
The EPRI-NP-4500-SR-LD analysis will be usGd as the basis for determining that the PBAPS HWC System meets Criterion 2.
Criterion 3 -- Protection from Postulated Detonation:
EPRI-NP-4500-SR-LD provides conservative analyses of TNT I
equivalency for a hydrogen. release associated with tank failure.
Blast overpressures and. impulses can then be calculated using the U.S. Army Technical Manual TMS-1300.
EPRI-NP-4500-SR-LD provides minimum separation distances vs. tank size assuming that safety-related, reinforced concrete structures can withstand an incident blast overpressure of 6 psi.
Reference 4 and Appendix A provide additional discussion of historical data on the response of reinforced concrete structures I
to blast loading.
These discussions support the recommendations
)
in EPRI-NP-4500-SR-LD.
I The hydrogen storage system location will meet, with considerable margin, the EPRI-NP-4500-SR-LD recommended separation distances.
The calculated incident overpressure at the plant stack and Unit 3 I
reactor building are 1.21 and 0.76 psi, respectively.
Prevention of Hydrogen Accumulation Near
(
Criterion 4
Safetv-Related Eauipment:
EPRI-NP-4500-SR-LD is based on the f act that violent storage tank I
damage such as that caused by an aircraft impact or tornado missiles will provide ample ignition sources such that early ignition is assured.
In EPRI-NP-4500-SR-LD early ignition is not considered to be assured for events such as earthquakes that only result in pipe breaks.
Therefore, dispersion analyses are done and appropriate separation distances vs. break size are calculated.
The EPRI-NP-4500-SR-LD guidance was used to establish the adequacy of separation distances for pipe breaks.
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VI.
HYDROGEN RELEASE CONSEQUENCC ACCEPTABILITY EPRI-NP-4500-SR-LD provides the consequence analyses which are used in the assessments given below of the acceptability of the proposed hydrogen storage system location.
Based upon the previous sections, we have identified events that I
result in either:
(1) no release, (2) a small gas release from the liqaid storage tank, (3) a small _ liquid release, or (4) a large liquid re: lease.
A summary of the events, analyses of the consequences of the releases using the EPRI-NP-4500-SR-LD guidance, and assessment of I
storage site location acceptability are presente2 in this section.
A.
No-Release Events Either the facility design or site characteristics prevent certain events from causing hydrogen releases.
The events are listed l
I below.
They include PBAPS safety-related structure design basis events and events specifically related to the hydrogen storage system.
(1)
Floods (storage area above design basis flood level);
(2)
High winds including 300 mph tornado winds (storage vessel design basis);
I (3)
Toxic chemical releases (no impact);
(4) Onsite and of f site industrial hazards (no PBAPS design basis events);
(5) Manufacturing defect (prevented by quality control and I
application of appropriate code requirements);
(6)
Delivery or other vehicle impact with hydrogen storage facility equipment (area protected by barriers);
(7)
Construction activity onsite (none planned near storage site);
(8)
Lightning strikes (facility grcunded);
I (9)
Aircraft impact (not a PBAPS design basis);
l (10)
Hydrogen delivery truck accidents (very unlikely and enveloped by other analyses);
B.
Small Gaseous Hydrogen Releases 1.
Sumary of Events The events that could cause small gaseous releases f rom the liquid storage portion of the hydrogen storage system are:
(1)
Failure of small piping caused by earthquakes; (2)
System abnormal operations leading to discharge through 3
relief devices.
g (3)
Extremely small and inconsequential pressure control valve releases.
I 3006S Page 19 of 23 I
a The worst case event is the seismically-induced rupture of g
relief piping upstream of the relief devices.
This piping will be 2 inches or less in diameter, 2.
Dispersion. Blast-Overpressure, and Fireball Effects Figure 3 (f rom EPRI-NP-4500-SR-LD, Figure 4-7) shows minimum I
acceptable separation distances from release point to safety-related structutes (based on blast overpressure calculations) and safety-related air intakes (based upon distance required to be below the lower flammability limit)
I vs. hole size in the storage system.
For a 2 inch hole, 110 feet and 460 feet of separation, respectively, are required.
I The separation distance provided at PBAPS is 1180 feet for safety related structures and 1750 feet for safety related air intakes, and is therefore acceptable.
Therefore, Criterion 4 for preventing the intake of flammable concentrations of hydrogen into safety-related air intakes and Criterion 3 for blast effects are met.
These events are not I
the limiting case for protection from fireball effects (Criterion 2).
C.
Small Liouid Release 1.
Summary of Events J
The events that could cause a small release of liquid hydrogen are:
(1)
Earthquake induced line break; (2)
Tornado missile induced line break:
The effects of tornado missile induced line break are enveloped by the impact of tornado missile induced vessel rupture, which is discussed under large liquid releases.
I 2.
Dispersion. Blast-Overoressure and Fireball Effects The consequences of a
earthquake-induced line break are acceptable if the hydrogen is out of the flammable range, before reaching saf ety-related air intake structures, and if lI detonation of the vaporized liquid in the explosive concentration range will not impact safety-related structures.
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Figure 4 (f rom EPRI-NP-4500-SR-LD, Figure 4-8) indicates that, for the 1180 feet of separation from safety-related intakes provided at PBAPS, the mass flow rate should be limited to less than approximately 0.5 kg/sec.
This corresponds to a I
break in the liquid line equivalent to an orifice of slightly over 1/4 of an inch diameter.
Air intake related separation requirements are more limiting than blast overpressures.
Based on the above, piping containing liquid hydrogen will be either (1) totally seismically supported; (2) seismically designed and supported up to and including a structural anchor downstream of excess flow check valves: or (3) seismically supported up to and including a structural anchor downstream of devices restricting mass flow in the event of a break to 0.5 kg/sec. or less.
Based on the above, Criterion 4 for preventing the intake of flammable concentrations of hydrogen into safety-related air I
intakes and Criteria 3 for blast ef fects will be met.
These events are not the limiting case for protection f rom fireball effects (Criterion 2).
D.
Large liquid Release 1.
Summarv of Events The only event that could cause large liquid hydrogen releases from the liquid hydrogen storage tank at the PBAPS site is a I
direct hit by a design basis tornado missile.
2.
Dispersion. Blast-Overpressure, and Fireball Effects i
Figure 5 (f rom EPRI-NP-4500-SR-LD, Figure 4-6), indicates that the necessary minimum distance f rom the storage area to the I
nearest safety-related structure for protection from blast overpressure is 400 feet.
The PBAPS separation distances are 1180 feet to the nearest safety related structure (plant stack);
and 1700 feet from the nearest safety related structure (reactor building) which is needed for safe shutdown in the event of a design basis tornado.
I Figure 6 (from EPRI-NP-4500-SR-LD, Figure 4-5) shows the results of analyses of fireball heat fluxes and durations.
This clearly shows that, at the separation distances provided at
- PBAPS, no uracceptable effects would result.
Thus Criterion 2 is met for the worst case fireball.
l A comparison of ignition sources caused by a tornado and associated missile strikes at the hydrogen storage system location with those associated with hydrccarbon spills caused by rail car at..ldents (see Section IV.8) is difficult.
Both I
3006S Page 21 of 23 I
a events are destructive to industrial equipment on a
5 significant scale and both would have the potential to disrupt electrical equipment, leading to arcing and other ignition 1
sources.
- Moreover, the thunderstorms that frequently I
accompany tornados and high winds are likely to be sources of static charge -- the extreme case being lightning.
Early 1
ignition following a tornado missile is considered likely.
Any ignition would lead-to a fireball type combustion and prevent any hydrogen cloud from reaching any plant air intake.
Thus Criterion 4 is met and no dispersion analysis is I
considered necessary.
It is also expected that dispersion of a tornado induced I
release will be rapid and that explosive and flammable concentrations would only occur in the immediate vicinity of the spill site and would be short lived.
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VII.
REFERENCES 1.
EPRI-NP-4500-SR-LD, " Guidelines for Permanent BWR Hydrogen Water Chemistry Installations" March 1986, by BWR Owners Group for IGSCC Research, Hydrogen Installation Subcommittee.
2.
- Linney, R.
E.,
" Hazard Analysis for Liquid Hydrogen Customer I
Station Located at the Commonwealth Edison Dresden Nuclear Power Plant", Air Products and Chemicals, Inc., October 22, 1984.
3.
- Camilli, L.
L.: Linney, R.
E.
& Doelp, L.
C.,
" Liquid Hydrogen I
Storage System -- Hazardous Consequence Analysis", Air Products and Chemicals, Inc., October 1,1985.
I 4.
- Reichert, P.
T.; Seeley, G.
T.,
" Safety Analysis for the Liquid Hydrogen Storage System -- Dresden Nuclear Power Station", Stearns Catalytic Corporation, October 31, 1985.
5.
- James, G.
B.,
" Fire Prevention in the Chemical Industry", NFPA Quarterly, Vol. 41, pg. 256.
6.
Lewis, V. and Von Elbe, G.,
Combustion. Flames and Explosions of Gases, 1951.
I 7.
Department o'f the Army, Structures to Resist the Effects of Accidental Explosion, TMS-1300, June 1969.
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FIGURE 2 HYDROGEN VS. METHANE IGNITION ENERGIES
- I I
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__----.,.-.-_3_....
I
.(
a...__-_.
... a..
e I
.a...
s _._
- x.. _.__ l_.....
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8
...L ME.THANt_ __..li
- ....._i......._...~.._--.i__..,.
I z-
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.... _. a.,
- a...__ t.
1.
...____t......,.. _. _. _... _...
...-t...__....
._._...._. :a,.
_.._....z.._._.
I 1.0 _.
... _. l _....i._..._.5 l
MINIMUM IGNITION ENERGY I
(MILLIJOULES)
I HYDROGEN 0.1 _
- s..
,i, J.........
.._........._.4._....__..
I
.t k
. ___ i._....
- _...;. j
._ e.
I
....._..._......._...t._.
...._._1_..
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0.01.
I
_i..__--
0 10 20 30 40 50 60 70 CONCEN1RATIONINAIR(%)
- FROM LEWIS, B. AND VON ELBE, G., COMBUSTION, FLAMES AND EXPLOSION OF GASES, 1951
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FIGURE 3 I
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I Minimum required separation distance to safety-related air intakes
~
460 tec.T I
g
$2 g
iIO SLt$.
y 102 I
y g
g
.g c
l 5
Minimum required separation distance to safety refated structures 10 1
I I I I III I
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.1 1
10 I
e.. e.
Hofe Size or inside Diameter of Pipe (in.)
l From EPRI-ND-4500-SR-LD Figure 4-7. Minimum required separation distance vs hole size and ID of pipe I
for gaseous releases from 150 psi liquid hydrogen storage tank.
I l
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. -.. =. _
I FIGURE 4 I
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Minimum required separation distance to safety related air intakes
~
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g 10 5
g g
g g
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Minimum required separation distance to safety-related structures
!102 I
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t 1
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1/8 1/4 1/2 1
Hole Size or Insicle Diameter of Pipe (in.)
' ' ' ' '.1 I
10 1
10 I
.01 Discharge Rate (kg/sec)
From EPRI-ND-4500-SR-LD Figure 4-8. Minimum required separation distance vs. hole size and discharge i
rate for liquid releases from 150 psi liquid hydrogen storage tank F w eather stability,1 m/s, wind velocity.
i l
n
I an m Sp e e
FIGURE 5 i
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i i iill l
1 i
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=
I E.
.50 5
303 2
Acceptable siting s
7 locations j
3 Minimum required
[
separation distance E
I
- s
.E
.52 Dynamic strength analysis required t
I t
i iiiI I
I I I I I i 102 4
105 103 10 Storage Tank Size (gal)
From EPRI-ND-4500-SR-LD I
Figure 4-6. Minimum required separation distance vs. liquid hydrogen storage tank size for instantaneous release of entire tank contents and explosion at tank site F weather stability.
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g l
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Key Tank Size (gal) Fireball Duration (sec) 0 20,000 8.18 O
18,000 7.90 I
4 A
9.000 6.27 y
6,000 5.48 102 I
Q 3,000 4.35
~
~
1,500 3.45 2
C I
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10 '
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dt.S ta t.k b
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1 0
200 400 600 800 1000 1200 1400 Distance from Fireball Center (ft)
,I'
- p. n.
Fron EPRI-ND-4500-SR-LD fg Figure 4 5. Thermal flux vs. distance from fireball center for liquid hydrogen storage system.
g
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APPENDIX A TO THE HYOR0 GEN SAFETY ANALYSIS CAPABILITY OF SAFETY RELATED STRUCTURES TO WITHSTAND BLAST LOADINGS Q
A2.
CALCULATED BLAST OVERPRESSURES A3.
HISTORICAL DATA ON BLAST EFFECTS
^
" " " ' " " " " ' ' " ~ ~ " ' '
'" "'-"'- ~'" "" "
I A3.2 EQUIVALENT REINFORCE 0 CONCRETE DATA A
3.3 CONCLUSION
S ON USE OF BLAST HISTORICAL DATA A3.4 BLAST EFFECTS ON REINFORCED CONCRETE STACKS A4.
EVALUATION OF PEACH BOTTOM CRITICAL STRUCTURE BLAST RESPONSE CAPABILITIES A4.1 PLANT STACK A4.2 REACTOR BUILDINGS A4.2.1 CONSIDERATION OF EPRI-NP-4500-SR-LD GUIDE A4.2.2 CONSIDERATION OF HISTORICAL DATA A4.2.3 USE OF NUREG/CR-2462 METHODOLOGY I.
I I
_._.~. ___ -,____ ___.__.._ _,_
A1.
INTRODUCTION This appenttix provides additional justification for the determination that the separation between the postulated hydrogen explosions and I
Peach Bottom safety related structures is satisfactory.
Identification of critical structures and the blast parameters f rom I
the limiting postulated explosion is provided in Section 2.
The historical data on blast effects which provide a basis for expected blast response capabilities are discussed in Section 3.
Section 4 provides an evaluation of blast response capabilities of critical structures considering both historical data and analytical methods.
The conclusion from these evaluations is that postulated explosions I
resulting from very unlikely, large releases from the hydrogen storage system will have no impact on the safety related equipment required to achieve safe shutdown following the release event.
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l 30065 l
A2.
cal.CULATED BLAST OVERPRESSURES The two nearest safety related struciures" to the liquid hydrogen storage site are the Plant Stack and the Unit 3 reactor Building.
These are located at 1180 ft. and 1700 feet, respectively, from the hydrogen storage site.
Safety related structures beyond these distances are considered to not be threatened by the postulated I
explosions due to the expected very low overpressures at these locations.
The worst case postulated explosion of released hydrogen for these two structures results from a tornado missile striking and piercing the liquid hydrogen tank, releasing its entire contents, followed by detonation of the resulting vapor' cloud.
The conversion f actor f rom EPRI-NP-4500-SR-LD yields a 27,400 lb. TNT equivalence for the 20,000 gallon tank.
Table i provides the relevant blast parameters.
I TABLE 1 BLAST PARAMETERS AT CRITICAL LOCATIONS (for 27,400 lb. TNT equivalent explosion)
(Calculated Per Reference 2, Page 122)
UNIT 3 PARAMETER PLANT STACK REACTOR BUILDING Distance (ft.)
1180 1700 Scaled Distance (ft./lb.
1/3) 39.14 56.39 Peak Side-On Overpressure (psi) 1.211 0.761 Peak Reflected Overpressure (psi) 2.506 1.555 Shock Wave Velocity (ft./sec.)
1155 1141 Particle or Wind Velocity (ft./sec.)
63.48 40.40 I
Dynamic or Wind Pressure (psi) 0.0352 0.0140 G
3006S
A3.
HISTORICAL DATA ON BLAST EFFECTS Historical data on the ef fect of blasts on. structures is principally f rom World War II.
The effects of both conventional and nuclear explosives have been used to determine thresholds for various levels of damage to structures.
I A3.1 Jarrett Formulation -- Used In EPRI-NP-4500-SR-LD Guide Reference 1 provides a range of damage thresholds based upon a review a
of well documented blast effects on brick construction dwelling g
units.
The threshold equation and constants are restated below:
gg%
I a + egyy Where R = Distance from Explosion in Feet I
W = TNT Weight Equivalent in Pounds DAMAGE EXPECTED (Incident Overpressure for Large Explosions)
K = 9.5 - Almost complete demolition.
(10.6 psi)
I K=
14
- 50 to 75 percent external brickwork destroyed or rendered l
unsafe and requiring demolition.
(5.2 psi)
K=
24 - houses uninhabitable - partial or total collapse of roof, partial demolition of one to two external walls, severe damage to load bearing partitions requiring replacement.
(2.3 psi)
K=
70 - not exceeding minor structural damage, and partitions and joinery wrenched from fixings (0.57 psi)
K = 140 remaining inhabitable after repair - some damage to ceilings and tiling, more than 10 percent window glass broken.
(0.22 psi)
Reinforced concrete structures which are designed seismically and for tornado winds have much greater strengtn than brick construction.
I For this reason a K of 14 was used as the acceptance threshold for safety related structures in EPRI-NP-4500-SR-LD.
A3.2 Reinforced Concrete Data Data and conclusions in Reference 2 and 3,
dealing with nuclear explosions and seismically designed reinforced concrete structures suggest the following K values:
DAMAGE EXPECTED (Incident Overpressure for Large Explosions)
I K = 5.7
- SEVERE DAMAGE Walls shattered, severe frame I
distortion, incipient collapse.
(35 psi)
A-3 30065
MODERATE DAMAGE -- Walls breached or on the point of being K o 6.5 so, f rame distorted.
Entranceways damaged, doors blown in or jammed, extensive spalling of. concrete.
(25 psi) l I
K = 9.8 - SLIGHT OR LIGHT DAMAGE -- Some cracking of concrete walls and f rame.
(10 psi)
References 2 and 3 can be used for brick construction to predict a K of 14 for severe damage and U for moderate damage.
These are in reasonable agreement with Reference 1.
As can be seen from historical
- data, seismically
- designed, reinforced concrets structures have considerable blast resistance.
This blast resistance is far in excess of brick construction.
A3.3 Conclusions On Use Of Blast Historical Data The K = 9.8 damage threshold is associated with a level of damage which might be considered acceptable for nuclear power plant I
structures, i.e.,
some cracking of structural
- concrete, but no spalling or loss of integrity.
However, for several reasons, a value should be chosen which provides some additional margin.
These reasons include (1) the limited amount of data, (2) there may be significant structural dif ferences, e.g. window openings may have served to rei uce the differential pressure durations (3) the nuclear blasts may have been above the structure, (reducing the reflected overpressure ef fects), (4) the likely variation in historical response.
The value of K of 14 was chosen as the criteria in EPRI-NP-4500-SR-LD for determining acceptable separation distances for critical structures.
For large blasts (where K is ef fectively equal to 2, the scaled distance) this corresponds to an incident overpressure of 5.2 psi.
This overpressure is 4.8 psi below those observed, in historical data, to result only in cracking of walls.
Therefore, it would be reasonable to assune that any damage would be limited to slight cracking with no loss of integrity.
A.3.4 Blast Effects On Reinforced Concrete Stacks Reinforced cc1 crete stacks respond to blast ef fects dif ferently than do reinforced concrete buildings.
These structures do not respond to blast overpressures because the blast pressures are quickly equalize'd due.to their small lateral size.
For this reason, stacks will respond principally to the dynamic pressure (wind loading or drag forces) which accompany the blast wave.
(See Reference 2 for additional discussion.)
j In Reference 2, two industrial stacks were observed which survived 15 psi blast overpressure (with resulting 4 psi dynamic pressure).
One stack was observed to have failed, with a 30 psi blast overpressure (with a resulting 20 psi dynamic pressure).
Stacks survive dynamic pressures which are greater than their static pressure design basis because of the very short duration of these loads relative to the stack period.
3006S
A4.
EVALUATION OF PEACH BOTTOM CRITICAL STRUCTURE BLAST RESPONSE CAPABILITIES I
A4.1 Plant Stack i
The Plant Stack is not required for safe shutdown of the Peach Bottom Plant.
It is seismically designed but not designed for tornado winds.
Its safety function is to provide release dilution in the I
event of a design basis accide't.
The stack is designed for wind loads varying from 25 psf at tbs base to 55 psf at the top (0.174 to 0.382 psi).
I The calculated blast overpressure, dynamic pressure, and particle (wind) speed are given in Table 1, above.
The dynamic pressure is far below those which have been observed to cause stack failure.
In 3
addition, the short duration, dynamic pressure is below the stack 5
static wind loading design basis.
Therefore, the postulated explosior. of release hydrogen will have no effect on the plant stack.
A4.2 Reactor Buildings The Reactor Buildings are constructed of two foot thick concrete I
walls, with floor elevations relative to grade of 0, 30, 60, and 99 feet.
The wall above the refuel floor are of a steel frame and siding construction not designed for tornado winds or missiles.
The I
concrete walls are designed for 300 mph wind speeds and a 3 psi tornado induced differential pressure.
The Reactor Buildings are 1700 feet from the hydr 6 gen storage site.
A4.2.1 Consideration of EPRI-NP-4500-SR-LD Guide The EPR1-NP-4S00-SR-LD criteria would require that the liquid I
hydrogen storage site be located at least 400 feet from the reactor building.
The provided distance of 1700 feet clearly meets this criteria.
A4.2.2 Consideration of Historical Data The calculated incident overpressure of 0.76 psi is far below the I
observed threshold for slight damage, (cracking in walls and frames) of approximately 10 psi overpressure.
I A4.2.3 Use of NUREG/CR-2462 Methodoloav Analysis of the response of the Reactor Building is considered unnecessary given the very low overpressures expected from the I
postulated hydrogen release explosion.
- However, a
simplified calculation, using the methodology discussed in NUREG/CR-2462 is included to assess the possible results of an analytical approach.
In this esse the reactor building is modeled as a three span 2 foot thick concrete wall, with.rebar sufficient to provide a static strength of 3.0 psi.
The output of this analysis is attached.
The calculated minimum allowable separation distance from the 27,400 lb. TNT equivalent blast is 579 feet.
Again, the provided distance I
of 1700 feet is well in excess of this criteria.
A-5 3006S l
w A4.2.4 Refuel Floor Effects The effects on the reactor building refuel floor (of a hydrogen storage tank breach, caused by a tornado missile, and followed by I
content release and postulated detonation) are considered to be comparable to that of a tornado striking the reactor building, i.e.
the steel walls may fail but safe shutdown would not be prevented.
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REFERENCES I
1.
- Jarrett, D.
E.,
" Derivation of the B r.i ti sh Explosives Safety Distances", Prevention of and Protection Against Accidental Explosion of Munitions. Fuels and Other Hazardous Mixtures, Annals of the New York Academy of Sciences, Volume,152, October 28, 1968.
2.
Glasstone, Samual, "The Ef fects of Nuclear Weapons",1962.
I' 3.
The Lovelace Foundation under contract to the U.S.
Atomic Energy Commission, " Nuclear Bomb Effects Computer", 1962.
i 4.
NUREG/CR-2462, " Capacity of Nuclear Power Plant Structures to Resist alast Loadings", September 1983. -
5.
EPRI-NP-4500-SR-LD,
" Guidelines for Permanent BWR Hydrogen Water Chemistry Installations", March 1986, by BWR Owners Group for IGSCC Research, Hydrogen Installation Subcommittee.
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I 30065 lI
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PROGRAM BLAST-EM I
This procram as for determining the capabilities of reinforced concrete to withstand blast loadings. The'aethods and assumptions are directly fres NUREG/CR 2462. "Capab111ty of nuclear Power Plants to-Withstand Blast Loadings", Sandia National Laboratories, September, 1983. Equation and Esferences are for this report unless otherwise noted.
I overpressures as opposed to sasuming that the reflected overpressure is One exception as that this program uses actual, normal incident, reflected Just 2 times the incident overpressure.
Dlast side-on overpressures and impulses are calculated using curvefits to I
data from " Air Blast Parameters Versus Distance for Hemispherical TNT Surface Bursts", Report No. 1344. Ballistic Research Laboratories, Aberdeen Proving Grouno, MD, September 1%6.
PROGRAM LAST REVISED: SEPTEMBER 10, 1986 I
- NUREG/CR 2462 Ref.
INPUT WALL THICKNESS (inches)
= 24.00 INPUT DEPTH FROM COMPRESSION SURFACE TO IINPUTRATIOOFAREA0FTENSILESTEELTO CENTROID OF TENSILE STEEL (anches) 21.38
=
TO EFFECTIVE AREA 0F CONCRETE = 2.730E-003 INPUT MAXIMUM $ PAN LENGTH (feet) 39.00
=
t'ALL MODELED AS THREE SPAN 5 IK=1.89E-001 MU = ULTIMATE STATIC MOMENT CAPACITY (in-lb/in width) = 6.58E+004 ** From Equation (All.
- +
From Equation (A9).
IG = GR055 MOMENT OF INERTIA (in."4/in. width) = 8.14E+002 Fros Equation (A7).
IC = CRACKED MOMENT OF INERTIA (in.*4/in width) = 1.63E+002 From Equation (AB).
IA = AVERAGE MOMENT OF INERTIA (in."4/in. width) = 4.89E+002 IP3=CALCULATEDSTATICCAPACITY From Equation (A6).
(psi)
=
3.00
- From Table A29.
Rn = EFFECTIVE YIELD POINT RE5ISTANCE OF STRUCTURE (psi) 3.96
- From Table A29.
=
T =
BUILDING PERIOD (milliseconds) 169
- From Table A29.
=
ITC=CLEARINGTIME(milliseconds)
HC = CLEARING LENGTH (ft) 90.00
- From Table A29.
=
225 From Equation (2.2).
=
INPUT DISTANCE FROM EXPLOSION TO WALL (feet) 1700 IINPUTTNTEQUIVALENT(1bs.)
=
= 2.740E+004 P50 = PEAK INCIDENT OVERPRES5URE (psi)
C.76
=
PR = NORMAL INCIDENT REFLECTED OVERPRES5URE (psi)
=
1.56 150=INCIDENTIMPULSE(gst-as) = 4.77E+001 TI = INCIDENT TRIANGULA LOAD DURATION (ss) =
From Equation (2.1).
125
- +
VITH 27400 POUND 5 OF TNT EQUIVALENT AT MINIMUM ALLOWABLE DISTANCE:
I AND WITH AN ALLOWABLE DUCTILITY OF 3.00:
PATH #1: CLEARING TIME 15 GREATER THAN LOAD DURATION ALLOWABLE Z (scaled distance) = 19.2 I
ALLOWABLE INCIDENT OVERPRE55URE (psi) 3,16
=
ASSOCIATED REFLECTED OVERPRE55URE (psi) 6.89'
=
ALLOWABLE R = 579 (feet)
IMPUL5E AT ALLOWABLE Z (psi-us) = 1.35E+002 TRIANGULAR DURATION AT ALLOWABLE Z (as) 85
=
TD = DURATION OF LOADING (as)
From Equation (A19).
85
=
++
" TD /T = *.06E-001 TM/T = 5.64E-001 Taken fres Figure A-4.
TH = TIME OF MAXIMUM RESPONSE (as)
=
95 IF1/RM= PEAK (REFLECTED) PRE 55URE/ YIELD POINT RESISTANCE = 1.74E+000 ** From T19ure A-4.
++
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I APPENDIX B TO THE HYDROGEN STORAGE SYSTEM SAFETY ANALYSIS IMPACT ON TRANSMISSION E0VIRNENT IN THE VICINITY 0F THE HYDROGE'N STORAGE SYSTEM REVISION-2 OCTOBER 10, 1986 l
Bl.
INTRODUCTION B2.
RELATIVE LOCATION OF NON-SAFETY RELATED EQUIPMENT B3.
COMPLIANCE WITH NFPA SEPARATION REQUIREMENTS B4.
NORMAL AND ABNORMAL HYDROGEN RELEASES B5.
IMPACT OF RELEASE EVENTS B5.1 NORMAL OPERATION I
B5.2 ABNORMAL OPERATION I
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B.1 INTRODUCTION -
~
~~ The hydrogen storage facility is located at a safe distance from
^
safety related structures..This is discusse~d in the main body of
{
~
I this report.
The goal for safety related structures is to assure t
that they are undamaged, such that safe shutdown can be accomplished for any release from the hydrogen storage facility whichhas a credible cause.
The impacts of the full range of severe natural I
phenomena used for the design of Peach Bottom safety related equipment are considered for the hydrogen storage system.
I For non-safety related equipment the design goal is to assure that this equipment will not be impacted by normal operation of the hydrogen storage system, nor by abnormal operation events which might reasonably be expected over the~ life of the equipment.
This is I
particularly the case for equipment which migh*; lead to a Peach Bottom plant transient.
I It is expected that compliance with NFPA SOB separation requirements will provide adequate protection for normal and abnormal operational events.
The equipment which was evaluated to assure that protection is adequate includes the nearest transmission line and the nearest I
500 KV substation.
The credible events which could cause larger hydrogen release are I
very inf requent, i.e. tornados and earthquakes, and have their own potential for disrupting non-safety related equipment, independent of what happens at the hydrogen storage site.
Therefore, protection of I
non-safety related equipment from the releases caused by severe natural phenomena is not considered necessary.
B.2 RELATIVE LOCATION OF NON-SAFETY RELATED EOUIPMENT Transmission lines and a 500 KV tubstation are the nearest PECO facilities, whose failure might contribute to a plant transient (i.e.
The nearest transmission line is a 500 XV line which is about 300 feet from the hydrogen storage area.
A substation is located 600 feet from the hydrogen storage area.
B.3 COMPLIANCE WITH NFPA SEPARATION RE0VIREMENTS NFPA 508, " Liquified Hydrogen Systems at Consumer Sites", has no I
separation requirements for transmission facilities, houever, the most restrictive l' imitation for this size of facility is 100 feet from combustibles (NFPA 508 Table 2).
NFPA SOB includes some I
spec' sal requirements for electrical equipment which is within 25 feet of a liquified hydrogen system.
The provided separation between the liquid hydrogen storage area and the transmission facilities is well in excess of the above requirements.
The NFPA requirements are sufficient to protect PBAPS facilities from the worst case vent stack release (Section B.4).
I Section B.5 provides assessments of the worst potential consequences of vent stack releases.
B-1 3006S 1
i
... ~.. -. _
_ v.J NORMAL AND ABNORMAL HYOROGEN RELEASES
-I The only norma.1 operatiot of the storage system where hydrogen can be released to atmosphere would be when the station is not using I
ambient air will vaporize enough liquid to require controlled venting hydrogen.
Then, af ter a few days, the normal heat transfer f rom the of the tank.
The vent rate would be on the order of 0.002 lbs./sec.,
intermittently.
I Abnornal occurrences resulting in hydrogen releases, which are unlikely but might occur over the life of the storage system, are I
related to the operation of overpressure protection devices (relief valve or rupture disk).
The peak vent rates associated with the worst case failure would be about 8 lbs./sec.
B.5 IMPACT OF RELEASE EVFNTS 8.5.1 Normal Operation The pressure control releases which are necessary after extended shutdown of the hydrogen supply system are at a very low rate, and are routed through a vent stack for elevated (on the order of 40 feet I
above grade) release.
They would be rapidly dispersed to below flammable concentrations at the exit.
B.S.2 Abnormal Operation The abnormal releases from relief valve or rupture dick operation are I
also routed through a vent stack for elevated release.
A high velocity vertical jet results and is dissipated to below flammable concentrations before significant lateral drift has occurred.
Vent stack releases are well away from ignitions sources and ignition is I
generally not expected.
Because of the unconfined location of the hydrogen release, even in I
the event of ignition, only a fire at the top of the vent stack would be expected.
Calculate thermal fluxes from such a vent stack fire fall below that necessary to ignite wood at a distance of 35 feet I
from the plume (Reference 1).
Such a fire would have no impact on Peach Bottom site transmission facilities. The thermal fluxes at the transmission lines 300 feet away would be on the order of area solar intensities.
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REFERENCE.
E 1.
- Camilli, L.
L.; Linney, R...E.;
& Doelp.
L.
C.7 " Liquid' Hydrogen Storage System. = Hazardous Consequence Analysis", Air Products and Chemicals, Inc., October 1,1985.
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PHILADELPHIA ELECTRIC COMPANY 1
I PEACH BOTTOM ATOMLC POWER STATION SAFETY ANALYSIS FOR THE LIQUID OXYGEN STORAGE SYSTEM Pevision 1 i
September 24, 1986 I
Prepared by Stearns Catalytic Corporation
_LA.
P.T. Reichert I
Supervisor Licensing and Nuclear Analysis 187KM b-Manager,NuclearSystem/
G. T. S(eley
/
I s
b r
/
D. M. Gi4rgione Project Manager I
//M E
R. E. Basso Manager, Nuclear Technology I
2985S
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TABLE OF CONTENTS I
I.
INTRODUCTION
~
II.
GENERAL DESCRIPTION OF LIQUID OXYGEN STORAGE SYSTEM (LOXSS)
I III.
POTENTIAL FOR SIGNIFICANT ACCIDENTAL RELEASES FROM THE LOXSS I
IV.
SAFETY EVALUATION OF LIQUID OXYGEN STORAGE SYSTEM LOCATION i
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2985S Page 2 of 7 I
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INTRODUCTION This safety analysis of liquid oxygen storage is intended to support the license amendment to permit liquid oxygen to be stored on site.
I The liquid oxygen will be stored in a liquid oxygen stcrage tank of i
11,000 gallon or less.
A.
Purpose and Scope of this Report The purpose of this report is to establish the acceptability of the design and chosen site for the liquid oxygen storage system.
I The determination of this acceptability, is based upon application of the criteria f rom EPRI-NP-4500-SR-LD, " Guidelines for Permanent BWR Hydrogen Water Chemistry ' Installations", by the BWR Owners Group for IGSCC Research, March 1986 (Reference 1).
B.
Structure of this Report Section II of this report describes the liquid oxygen storage system.
The actual oxygen supplier has not yet been chosen.
The liquid oxygen storage system will be provided by a supplier with I
extensive experience in the design, operation, and maintenance of storage and supply systems.
I Section III identifies the circumstances which might result in the release of liquid oxygen, up to and including release of the entire contents.
Section IV presents the evaluation of the location of the liquid oxygen storage system using EPRI-NP-4500-SR-LD guidance.
C.
Conclusion The conclusion of this report is that safe separation distances I
are provided between the LOXSS site and all PBAPS safety related equipment.
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29855 Page 3 of 7 I
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II. GENERAL DESCRIPTION OF LIQUID OXYGEN STORAGE SYSTEM (LOXSS)
I A.
Eauipment Description The LOXSS will consist of:
a liquid oxygen storage tank, up to 11,000 gallons in size (2) ambient air oxygen vaporizer banks I
a pressure / temperature control manifold I
related interconnecting piping, valves, control panel and controls The oxygen tank will consist of an inner vessel or " liquid container" and an outer vessel with the space between filled with insulation and evacuated.
The inner vessel will be designed, I
fabricated, tested and stamped according to applicable ASME codes.
The tank will have appropriate overpressure protection devices.
The liquid oxygen storage system will meet all applicable design requirements of EPRI-NP-4500-SR-LO.
The design of the LOXSS system makes large unplanned relea'ses of I
oxygen very unlikely.
Potential site-related causes of tank failure are evaluated to determine what other, related design criteria should be used.
The tank will be designed to remain in place under Peach Bottom Atomic Power Station (PBAPS) tornado wind I
load design basis conditions.
B.
Location of LOXSS I
The location of the LOXSS relative to other PBAPS facilities is shown on Figure 1.
Table 1 shows the distance from the liquid oxygen storage tank to all safety related air intakes and their I
height above grade.
The LOXSS meets all separation requirements of NFPA 50, Bulk I
Oxygen Systems at Consumer Sites including required separation from liquid hydrogen storage facilities.
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III.
POTENTIAL FOR SIGNIFICANT ACCIDENTAL RELEASES FROM THE LOXSS The only possible releases from the LOXSS under normal operating conditions are in the event of extended supply system shutdown where I
the gradual heat input must be controlled by occasional, small volume, venting the tank.
I The only possible releases from the LOXSS under abnorrnal operating conditions would be associated with tank relief valve actions.
Both normal and abnormal operational releases would be rapidly I
dispersed in the imediate vicinity of the LOXSS.
Adequate protection from such releases is provided by compliance with NFPA 50 standards.
It is not possible to protect the LOXSS from the full range of design basis natural phenomena used for the PBAPS safety related equipment.
Therefore, low probability, accidental releases of the entire tank contents are postulated and evaluated in Section IV.
Design provisions are made to assure that the release will originate at the LOXSS site.
These include that the liquid oxygen tank is I
designed to remain in place during a PBAPS design basis tornado and design basis flood.
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IV.
SAFETY EVALUATION OF LIOUID OXYGEN STORAGE SYSTEM LOCATION The only hazard f rom a liquid oxygen spill is a possibly increased fire risk.
Oxygen-enriched air can make combustible materials ignite I
at lower temperatures and accelerate combustion.
However, it would not increase area combustible loadings nor would spontaneous ignition result. An ignition source is still required.
The design goal is to prevent ingestion of excessively oxygen-enriched air into safety-related. air intakes.
The limiting hazard is associated with an assumed total, instantaneous release of the tank contents.
For safety-related building HVAC air intakes, for the emergency I
cooling tower air inlet, and for the diesel generator combustion air intakes, the guidance from EPRI-NP-4500-SR-LD for location o( the liquid oxygen storage system was used.
EPRI-NP-4500-SR-LD uses a dense gas dispersion model to predict the extent and height above grade of the oxygen plume resulting f rom a liquid oxygen tank instantaneous breach.
EPRI-NP-4500-SR-LD uses a I
conservative limitation of 30 percent oxygen at any safety related air intake.
I TaDie 1 shows the distance f rom the liquid oxygen storage tank to all safety related air
- intakes, their height above grade and the appropriate limitations f rom Figure 2 (f rom EPRI-NP-4500-SR-LD, Figure 4-9).
All safety related' air intakes are at an acceptable distance and/or height.
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l TABLE 1 SEPARATION OF SAFETY RELATED AIR INTAKES FROM OXYGEN STORAGE SYSTEM DISTANCE HEIGHT MINIMUM l
FROM OXYGEN OF INTAKE REQUIRED HEIGHT STORAGE SYSTEM ABOVE GRADE ABOVE GRADE REACTOR BUILDING HVAC 885 FEET 79 FEET 19 FEET CONTROL BUILDING HVAC 1055 FEET 43 FEET 19 FEET I
DIESEL GENERATOR BUILDING 1422 FEET 16 FEET 0 FEET HVAC AND COMBUSTION I
EMERGENCY SERVICE WATER 1065 FEET 25 FEET 19 FEET I
PUMP ROOM I
EMERGENCY COOLING TOWER 300 FEET 39 FEET 19 FEET ELECTR0 MECHANICAL EQUIPMENT ROOM AND I
COOLING TOWER AIR INTAKE I
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Distance from Liquid Oxygen Storage Tank (ft) m.sv.
From EPRI-ND-4500-SR-LD Figure 4-9. Acceptable locatiens cf safety-related air intakes for various sizes of liquid cxygen storage tanks.
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Electric Power a
chemistry Research Institute Corrosion protection I
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Guidelines for Permanent BWR l
Hydrogen Water Chemistry Installations I
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Prepared by Electric Power Research Institute Palo Alto, California I
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Guidelines for Permanent BWR Hydrogen l2 Water Chemistry Installations I.
NP 4500-SR-LD Special Report March 1986 Prepared by BWR OWNERS GROUP FOR IGSCC RESEARCH Hydrogen Installation Subcommittee I
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lI Prepared for BWR Owners Group and l
Electric Power Research Institute 3412 Hillview Avenue Palo Alto, California 94304 I
EPRI Project Manager W. J. B!ianin Nuclear Power Division I
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ABSTRACT Intergranular stress corrosion cracking (IGSCC) of austenitic stainless steel piping in BWRs has resulted in costly plant outages. One method shown effective in, arresting pipe cracking and pipe crack growth is a process known as Hydrogen Water Chemistry (HWC). HWC consists of maintainirg good water chemistry and adding hydrogen to the feedwater. Addition of hydrogen decreases the oxidizing power of the reactor water and reduces its aggressiveness toward plant structural materials. This document provides guidelines for design, construction, and oper-I ation of permanent hydrogen injection systems at BWRs to allow implementation under 10 CFR 50.59. The scope of this document includes the currently available on-site hydrogen and oxygen supply cptions (i.e., compressed gas, cryogenic liquid, and electrolytic generation) and the delivery system design and controls. Included are guidelines for design, operation, maintenance, surveil-I lance, and testing to provide for safe system and plant operation. Compliance with these guidelines will ensure that this system installation and operation will not produce a safety concern.
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I ACKNOWLEDGMENTS This document was prepared by the following experienced industry personnel through an effort sponsored by the BWR Owners Group for IGSCC Research and EPRI.
W. Bilanin. EPRI L. Brehm, Northern States Power Company L. Camilli, Air Products and Chemicals, Inc.-
J. Goldstein, New York Power Authority D. Helwig, Philadelphia' Electric Company M. Ira, Tennessee Valley Authority E. Kearney, Boston Edison Company J. Klapproth, General Electric Company E. Rowley, Comonwealth Edison Company R. Scholz, Philadelphia Electric Company a
T. Seeley, Stearns Catalytic Corporation 1
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CONTENTS Section Page i
1 INTRODUCTION............................................................
1-1 1.1 Scope..............................................................
1-1 1.2 Background.........................................................
1-2 1.3 Preimplementation Testing..........................................
1-3 1.4 Reference..........................................................
1-4 2
GENERAL SYSTEM DESCRIPTION..............................................
2-1 I
2.1 General Design Criteria............................................
2-1 2.2 Hydrogen Supply 0ptions............................................
2-1 2.2.1 Comerci al Su ppl i ers........................................
2-3 2.2.2 On-Site Production..........................................
2-3 2.2.3 Recovery....................................................
2-3 2.3 Gas Injection Systems....................'..........................
2,4 2.3.1 Hydrogen Injection System...................................
2-4 2.3.2 Oxygen Injection System.....................................
2-7 2.4 Instrumentation and Contro1........................................
2-8 2.4.1 Hydrogen Injection Flow Contro1.............................
2-8 2.4.2 0xygen Injection Flow Contro1...............................
2-12 I
2.4.3 Monitoring..................................................
2-12 3
SUPPLY FACILITIES.......................................................
3-1 3.1 Gaseous Hydrogen...................................................
3-1 3.1.1 System 0verview.............................................
3-1 3.1.2 Specific Equipment Description..............................
3-1 3.2 Liquid Hydrogen....................................................
3-4 3.2.1 System 0verview.............................................
3-4 I
3.2.2 Specific Equipment Description..............................
3-5 3.3 Electrolytic.......................................................
3-8 3.3.1 System 0verview.............................................
3-8 3.3.2 Specific Equipment Description..............................
3-8 I
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E Section Page 3.4 Liquid 0xygen......................................................
3-11 3.4.1 System 0verview.............................................
3-11 3.4.2 Specific Equipment Description..............................
3-11 3.4.3 Materials of Construction for Oxygen Piping and Va1ves.............................................
3-13 3.4.4 0xygen Cleaning............................................
3-15 4
SAFETY CONSIDERATIONS..................................................
4-1 4.1 Gaseous Hydrogen...................................................
4-1 4.1.1 Site Characteristics of Gaseous and Liquid Hydrogen.........
4-1 4.1.2 Gaseou s Storage Vessel Fail ure.............................
4-2 4.1.3 G aseou s P i pe Bre ak s........................................
4-4 4.2 Liquid Hydrogen....................................................
4-7 4.2.1 Storage Vessel Fa11ure.....................................
4-7 4.2.2 Pipe Breaks................................................
4-10 I
4.3 Electrolytic......................................................
4-13 4.3.1 Genera1....................................................
4-13 4.3.2 Purity of Gases............................................
4-16 4.3.3 Air In1eakage...........................................
4-16 4.3.4 Out Leakage......................................'..........
4-17 4.3.5 External Events............................................
4-17 4.4 Liquid 0xygen.....................................................
4-17 4.4.1 Site Characteristics of Liquid 0xygen.......................
4-17 4.4.2 Liquid Oxygen Storage Vessel Failure.......................
4-18 4.4.3 ' Liquid Oxygen Vapor Cloud Dispersion........................
4-18 I
4.5 Reference.........................................................
4-19 5
VERIFICATION............................................................
5-1 6
OPERATION, MAINTENANCE, AND TRAINING....................................
6-1 6.1 Operating Procedures..............................................
6-1 6.1.1 Integration Into Existing Plant Operation Procedures........ 6-2 6.1.2 Plant Specific Procedures..................................
6-2 6.1.3 Radiation Protection Program................................
6-2 I
6.1.4 Water Chemistry Contro1.....................................
6-4 6.1.5 Fuel Surveillance Program...................................
6-4 6.2 Maintenance.......................................................
6-4 6.3 T r a i n i ng..........................................................
6-5 6.4 Identification.....................................................
6-6 I
6.5 References........................................................
6-6 viii g
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=m..
a Section Page Su m m u m ANo 1ES11Ne................................................ z-1 7.1 Sys tem I nteg r i ty Te st i ng..........................................
7-1 7.2 Preoperational and Periodic Testing...............................
7-1 8
RADIATION MONITORING...................................................
8-1 8.1 Introduction......................................................
8-1 8.2 Mai n Steam Line Radi ation Moni tori ng.............................. 8-1 I
8.2.1 Dual MSLRM Set Poi nt Recommendation........................ 8-2 8.2.2 MSLRM Safety Design Basis..................................
8-2 8.2.3 MS LRM Sens i t i v i ty..........................................
8-3 8.2.4 Conclusions................................................
8-3
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8.3 Equ i pment Qual i f i cati on........................................... 8-3 8.4 Env i rormental Consi derati ons...................................... 8-3 8.5 References........................................................
8-4 9
QUALITY ASSURANCE......................................................
9-1 9.1 System Designer and Procurer......................................
9-1 9.2 Control of Hydrogen Storage and/or Generation Equiprent Suppliers..........................................~...............
9-1 9.3 System Constructor................................................
9-2 APPENDIX A CODES. STANDARDS, AND REGULATIONS APPLICABLE TO PERMANENT HYDROGEN WATER CHEMISTRY INSTALLATIONS......... A-1 I
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I-LIST OF FIGURES Figure Page 2-1 Hydrogen Addition System..................................... 2-2 4-1 Thermal Flux versus Distance from Fireball Center for........ 4-3 Gaseous Hydrogen Storage System 4-2 Damage Curve for Residential Brick Buildings................. 4-5 I
4-3 Minimus Required Separation Distance to Safety-Related....... 4-6 Structures versus Vessel Size for Gaseous Hydrogen Storage System 4-4 Minimum Required Separation Distance to Safety-Related....... 4-8 Air Intakes versus Hole Size or ID of Pipe for Releases from 2450 psig Gaseous Hydrogen Storage System 4-5 Themal Flux versus Distance from Fireball Center for........
4-11 Liquid Hydrogen Storage System 4-6 Minimum Required Separation Distance versus Liquid...........
4-12 Hydrogen Tank Size for Instantaneous Release of Entire Tank Contents and Explosion at Tank S.ite - F Weather Stability 4-7 Minin:m Required Separation Distance versus Hole Size........ 4-14 and ID of Pipe for Gaseous Releases from 150 psi Liquid Hydrogen Storage Tank 4-8 Minimum Required Separation Distance versus Hole size and....
4-15 I
Discharge Rata for Liquid Releases from 150 psi Liquid Hydrogen Storage Tank - F Weather Stability, 1 m/s Wind Velocity 4-9 Acceptable Loctions of Safety - Related Air Intakes for......
4-20 Various Sizes of Liquid Oxygen Storage Tanks e
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I LIST OF TABLES Table Page I
2-1 Recomended Trips of the Hydrogen Addition System............
2,9 2-2 Hydrogen Addition System Instrumentation and Controls........
2-10 I
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Section 1 INTRODUCTION 1.1 ' SCOPE This document sets forth design, construction, and operational guidelines for permanent hydrogen injection systems at boiling water reactors (BWRs) to allow implementation under 10 CFR 50.59. As such, its purpose is to provide a reference I.
document for utility use. NRC staff acceptance of these guidelines should minimize the amount of plant specific evaluations required.
The purpose of the hydrogen injection system is to inject hydrogen into the reac-tor coolant, presently via the feedwater system, to suppress the dissolved oxygen concentration. Sur;ressing the dissolved oxygen concentration and maintaining high purity in the reactor coolant will reduce the susceptibility of reactor piping and materials to intergranular stress corrosion cracking (IGSCC). This process is referred to as hydrogen water chemistry (HWC).
g The scope of this document includes the currently available on-site hydrogen and W
oxygen gas supply options (i.e., compressad gas, cryogenic liquid, and electro-lytic generation) and the gas delivery system design and controls. Included in this scope are the hydrogen injection system requirements for operation, mainte-l nance, surveillance, and testing to provide for safe system and plant operation.
Compliance with these requirements will ensure that the installation and operation of this system does not produce a safety hazard.
There are two primary regulatory concerns related to the pemanent implementation of HWC: the potential impact of failures in the oxygen and hydrogen storage /
g handling systems on the plant safety systems and increased dose rates due to l N increased N-16 carry-over in the steam. For the oxygen and hydrogen storage /
handling issue, this document addresses the possible failure modes of these systems. These failure modes include events external to these systems such as seismic, tornados, fire, vehicle hazards, etc. In addition, system internal I
events such as overpressurization and relief valve failures and the potential impact on plant structures and control room habitability are addressed. For these I
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events, a mechanistic approach, as opposed to a probabilistic approach, is used as the basis for siting hydrogen and oxygen gas storage facilities. Using sufficiently conservative assumptions, the minimum distance between the hydrogen and oxygen supply facilities and safety-related structures is prescribed.
Injection of hydrogen into the feedwater system of a BWR can result in up to an approximate 5 fold increase in the activity in the steam. Consequently, HWC will result in a minor increase in the site personnel exposure. However, over the life of the plant, HWC offers the potential for significantly reduced exposures because of the avoidance of recirculation pipe replacement and reduced pipe crack repair and inspection. This document provides reconsnendations to' minimize the radio-logical impact of permanent HWC installations and to maintain exposures as-low-as-reasonably-achievable (ALARA). In addition, the justic ication for increasing the main steam line radiation monitor setpoint to accommodate HWC is provided.
Some potential issues that will not impact continued safe plant operation but are associated with permanent HWC programs are:
1.
Materials impect 2.
Fuel impact 3.
Reactor physics impact 4.
Equipment qualification impact Based on the conclusions of HWC laboratory testing and field testing at Dresden 2, there is no significant concern with hydrogen embrittlement. Based on the destructive examiration of fuel exposed to HWC at Dresden 2, no significant impact on fuel performance is, expected. Although the dissolved hydrogen concentration in the core inlet water increases slightly, the impact on core reactivity is insignificant, and reactor physics will not be affected. With regards to equip-I ment qualification, dose rates inside the drywell close to the recirculation I
piping will decrease due to the increased carry-over of~N-16 in the steam. Out-side the drywell, the increase in the dose rates is relatively small relative to the integrated dose assumed for qualification tests.
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1.2 BACKGROUND
l The recirculating coolant in BWRs is high-purity (no additive) neutral pH water l
containing radiolytically produced dissolved oxygen (100-300 ppb). This level of dissolved oxygen is sufficient to provide the electrochemical driving force needed 1-2 I
2 -
I to promote IGiCC of sensitized austenitic stainless steel piping and similar structural components if the other two prerequisites for IGSCC [a sensitized microstructure (chromium depletion at the grain boundaries) and a tensile stress above the yield stress] are also present.
A variety of IGSCC remedies have been developed and qualified which address the sensitization and tensile stress aspects of stress corrosion cracking. Another approach for suppressing IGSCC involves modifying the BWR coolant environment to reduce the electrochemical driving force for IGSCC.
The HWC technique consists of reducing the coolant dissolved oxygen level from the present -200 ppb to that level which, in combination with high water quality, has been shown to result in IGSCC immunity. The reduction in coolant oxygen is accomplished by the additien of hydrogen and the conductivity of the coolant is I
reduced (if needed) by improved water quality operational practices. The feasibility of suppressing oxygen by this approach has been demonstrated in short-term demonstrations in eight BWRs. A long-term verification test which will extend over two or three 18-month fuel cycles was initiated at Dresden-2 in April 1983.
An extensive laboratory investigation of the material performance consequences of combining oxygen suppression with conductivity control has demonstrated that sub-stantial mitigation and possibly complete suppression of IGSCC can be achieved in
-280*C water witt less than 20 ppb dissolved oxygen content if the conductivity was maintained below about 0.3 vs/cm. Results of slow strain rate tests at I
Dresden-2 have confirmed the anticipated improvement in the IGSCC resistance of sensitized austenitic stainless steel under HWC conditions and also supported other laboratory data indicating that HWC is a more innocuous service enviror. ment for most BWR ple.nt structural materials than the non-HWC environment.
I 1.3 PREIMPLEMENTATION TESTING Each utility should consider verifying the feasibility of implementing hydrogen I
water chemistry at their particular site.
In order to implement HWC, each utility should maintain water quality consistent with the "BWR Water Chemistry Guidelines" (Reference 1-1). This may result in an additional burden to the radioactive waste system. Each utility should evaluate I
the effect maintaining high water quality will have on plant systems.
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I Each utility should determine the hydrogen addition rate where IGSCC is mitigated. As the hydrogen addition rate is incrementally increased, the reactor dissolved oxygen concentration and the reactor recirculation piping electrochemical potential (ECP) decrease. Measuring the ECP of metal samples exposed to reactor recirculation water is one method for determinirig the point at which IGSCC imunity has been reached.
I After determining the HWC operating parameters, verification methods such as Constant Extension Rate Testing (CERT) and Crack Arrest Verification (CAV) systems can be implemented.
Implementing HWC will increase the N-16 carryover of the steam which causes I
increased on-site and off-site dose rates. These radiological impacts should be evaluated for acceptability. Section 6.1.3 of this report provides guidance for evaluating this impact and some techniques for mitigation.
As the hydrogen addition rate is increased, the feedwater dissolved oxygen I
concentration is reduced. During preimplementation testing, this parameter should be monitored. If the feewater dissolved oxygen concentration is found to be unacceptably low, feedwater oxygen injection can be used to resolve this concern.
The guidelines for short-term HWC preimplementation testing to determine the I
hydrogen flow sheet are not in the scope of this document. Also, system availability and other issues that are required to obtain licensing credit for HWC (e.g., reduced in-service inspection) are not addressed.
1.4 Reference i
1-1 "BWR Water Chemistry Guidelines." EPRI Report NP-3589-SR-LD, April 1985.
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Section 2 GENERAL SYSTEM DESCRIPTION I
Figure 2-1 shows the hydrogen addition system in simplified form. For this report, the system is divided into hydrogen supply, oxygen supply, hydrogen injection, and oxygen injection systems.
Options for hydrogen supply are discussed briefly below, and detailed descriptions of the main options are provided in Section 3.
Oxygen supply is also described in Section 3.
The gas injection systems are described in this chapter. Also des-cribed in this chapter are instruments and controls applicable to the entire system.
2.1 GENERAL DESIGN CRITERIA The hydrogen water chemistry system is not safety-related. Equipment and compo-
'nents need not be redundant (except where required to meet good engineering prac-tice), seismic category I, electrical class IE, or environmentally qualified.
Nevertheless, proximity to safety-related equipment or other plant systems requires special consideration in the design, fabrication, installation, operation and maintenance of hydrogen addition system components. Section 9 of this docu-ment delineates the quality assurance and quality control requirements to assure a safe and reliable hydrogen addition system. In some cases these requirements are I
over and above those which are normally required for non-safety-related installations.
The hydrogen addition system s;.suld suppress the dissolved oxygen concentration in the recirculation water to a point where IGSCC imnranity is maintained at all reactor power levels at which the hydrogen addition system is operating.
2.2 HYDROGEN SUPPLY OPTIONS Hydrogen can be supplied from three sources: (1) a commercial hydrogen supplier; (2) onsite production from raw materials; or (3) recovery and recycle of hydrogen from the off-gas system. Any combination of these three methods may, in princi-ple, be appropriate at a given facility.
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I Feedwater or condensate booster pump Condl R.P.V.
H gas Hydr en Q
Oxygert I
supp y :
<-->-> supply subsystem subsystem Hydrogen Oxygen I
- injection injection -
subsystem subsystem Figure 2-1. Hydrogen addition system.
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2.2.1 Comercial Suppliers Hydrogen can be obtained comercially from two types of sources: (1) merchant producers (i.e., companies that make hydrogen for the purpose of selling it to I
others) and (2) by-product producers (i.e., companies that produce hydrogen only as a by-product of their main business).
r.ydrogen obtained in this manner is supplied as a high pressure gas or as a cryogenic liquid. Detailed considerations for gaseous and liquid hydrogen supply facilities are described in Sections 3.1 and 3.2 of this report, respectively.
{
2.2.2 On-Site Production Industrial processes for hydrogen production can be divided into two groups:
electrolysis of water and thermochemical decomposition of a feedstock that contains hydrogen.
Detailed considerations for onsite production of hydrogen by electrolysis are I
described in Section 3.3 of this report.
All other processes for producing high purity hydrogen involve thermochemical decomposition of hydrogen-containing feedstocks followed by a series of chemical and/or physical operations that concentrate and purify the hydrogen. While these I
processes are feasible, in principle, they are not currently envisioned for implementation. Therefore, these processes are not addressed in this report.
2.2.3 Recovery Many processes are comercially available for separating, concentrating, and pur-ifying hydrogen from refinery or by-product streams or for upgrading the purity of manufactured hydrogen. Processes are also being developed for the recovery and storage of hydrogen by the formation of rechargeable metal hydrides.
I Although recovery of hydrogen is a viable option, near-term imp 1'ementation of this option is not envisioned. Therefore, this option is not addressed in this report.
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2.3 GAS INJECTION SYSTEMS 2.3.1 Hydrogen Infection System The hydrogen injection system includes all flow control and flow measuring equipment and all necessary instrumentation and controls to ensure safe, reliable operation.
I 2.3.1.1 Injection Point Considerations. Hydrogen shall be injected at a location that provides adequate dissolving and mixing and avoids gas pockets at high points. Experience has shown that injection into the suction of feedwater or condenstte booster pumps is feasible.
I Injection into feedwater pumps will require hydrogen at high pressures (e.g.,
150-600 psig). This may require either a compressed gas supply, compressors or a cryogenic hydrogen pump, depending on the supply option chosen. In the case of a liquid hydrogen storage system, this can also affect the sizing of the liquid hydrogen tank.
l '
There may be pressure fluctuations in feedwater systems, depending on reactor power level and pump performance. The hydrogen addition system sha'11 be designed to accomodate the full range of such fluctuatiers.
l 2.3.1.2 Codes and Standards. This system shall be designed and installed in accordance with OSHA standards in 29 CFR 1910.103.
Piping and related equipment shall be designed and fabricated to the appropriate I
edition of ANSI B31.1 or B31.3 for pressure-retaining components. Storage con-tainers, if used, shall be designed, constructed, and tested in accordance with appropriate requirements of ASME B&PV Section VIII or API Standard 620. All components shall meet all the mandatory requirements and material specifications with regard to manufacture, examination, repair, testing, identificatior, and certification.
All welding shall be performed using procedures meeting requirements in AWS 01.1, ANSI B31.1 or B31.3, or ASME B&PV,Section IX, as appropriate.
~
I Inspection and testing shall be in accordance with requirements in ANSI B31.1 ANSI B3.3, or API 620, as appropriate.
I 2-4
System design shall also conform with pertinent portions of NUREG-0800, 10CFR50.48, Branen Technical position BTP CMEB 9.5-1, and appropriate standards and regulations referenced in this document. Appendix A provides a list of codes, standards, and regulations applicable to permanent hydrogen water chemistry installations. Each utility is responsible for identifying additional plant-I sp?cific codes and standards that may apply, such as State-imposed requirements.
Uniform Building Code, ACI or AISC standards.
I Piping and equipment shall be marked or identified in accordance with ANSI Z35.1.
2.3Property "ANSI code" (as page type) with input value "ANSI Z35.1.</br></br>2.3" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process..1.3 System Design Considerations. Hydrogen piping from the supply system to the plant may be above or below ground. Piping below ground shall be designed for cathodic protection, the appropriate soil conditions such as frost depth or liquefaction, and expected vehicle loads. Guard piping around hydrogen lines is not required; however, consideration shall be given to its use for such purposes as protection from heavy traffic loads, leak detection and monitoring, or isola-tion of the potential hazard from nearby equipment, etc. All hydrogen piping should be grounded and have electrical continuity.
Excess flow valves should be installed in the hydrogen line at' appropriate loca-tions to restrict flow out of a broken line. Excess flow protection shall be designed to ensure that a line break will not result in an unacceptable hazard to personnel or equipment (BTP CMEB 9.5-1).
The design features for mitigating the consequences of a leak or line break must perform their intended design function with or without normal ventilation.
Individual pump injection lines shall contain a check valve to prevent feedwater from entering the hydrogen line and to protect upstream hydrogen gas components.
Automatic isolation valves should be provided in each injection line to prevent hydrogen injection into an inactive pump.
Purge connections shall be provided to allow the hydrogen piping to be completely purged of air before hydrogen is introduced into the line. Nitrogen or another inert gas shall be used as the purge gac. Gases shall be purged to safe loca-tions, either directly or through intervening flow paths, such that personnel or explosive hazards are not encountered and undesirable quantities of gas are not injected into the reactor.
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Area hydrogen concentration monitors are an acceptable way to ensure that hydrogen concentration is maintained below the flamable limit. If used, such menitors should be located at high points wherE hydrogen might collect and/or above use points that constitute potential leaks. These monitors shall be capable of I
detecting hydrogen leaks with or without normal ventilation. Sleeves or guard pipes can be used as an alternative method to mitigate the. consequences of a line break.
A hydrogen addition system will increase the hydrogen concentration in the I
feedwater, reactor, steam lines and main condenser. Each of these systems shall be reviewed for possible detrimental effects. A discussion of possible concerns is presented below.
1.
Ma'in Condenser The main condenser presently handles combustible gases. The I
hydrogen addition system does not significantly change the con-centration or volume of non-condensables. Therefore, it is not anticipated that hydrogen addition will affect operation of the main condenser.
2.
Off-Gas System I
0xygen shall be added into the off-gas' system to recombine with the hydrogen flow thus limiting the extent of the system handling hydrogen rich mixtures and reducing volumetric flow-rates. The net effect will probably be a revised heat input I
into the recombined off-gas. The capability of the off-gas system to handle this revised heat load must be evaluated to ensure that temperature limits are not exceeded. Considera-tions in the design of the off-gas oxygen injection system I
should include loss of oxygen and runaway oxygen injection.
3.
Steam Piping and Torus Hydrogen water chemistry may slightly increase the rate of hydrogen leakage into the torus via the safety relief valves.
However, the rate of oxygen leakage will be decreased. Thus, I
the possibility of forming a combustible mixture is not significantly increased when compared to non-HWC operation.
4.
Sumps There are three water systems that may be affected by HWC: main condenser condensate, feedwater and reactor water. For sumps which receive water from any of these three sources, the I
average hydrogen concentration in the water may increase slightly. The maximum expected concentration of hydrogen in the sump atmosphere should be determined to ensure that the hydrogen concentration remains below the lower combustible I
limit of hydrogen in air.
I 2-6 I
I-I 2.3.2 0xygen Injection System The oxygen injection system injects oxygen into the off-gas system to ensure that I
all excess hydrogen in the off-gas stream is recombined. It includes all necessary flow control and flow measurement equipment.
2.3.2.1 Injection Point Consideration. Oxygen should be injected into a portion I
of the off-gas system that is already diluted such that the addition of oxygen does not create a combustible mixture. If this is not possible, other system design considerations t il be provided in plant-specific cases to reduce the chances for off-gas fires.
I 2.3.2.2 Codes end Standards. The system shall be designed and installed in accordance with OSHA standards in 29 CFR 1910.104, and CGA G4.4, Industrial Practices for Gaseous Oxygen Transmission and Distribution Piping Systems.
Piping and related equipment shall be designed, fabricated, tested and installed I
in accordance with the appropriate edition of ANSI B31.1 or ANSI B31.3. Addi-tionalguidanceonmaterialsofconstructionforoxygenpipingandvalvesisgiven in Section 3.4 of this report, and in ANSI / ASTM G63, " Evaluating Nonmetallic Materials for Oxygen Service."
I Welding shall be performed using procedures meeting requirements of AWS 01.1 or ASME B&PV,Section IX, as appropriate.
Piping shall be marked or identified in compliance with ANSI Z35.1.
l I System design shall also conform with appropriate NFPA, CGA, and other standards and regulations referenced elsewhere in this document. Ee.ch utility is respon-sible for ide'ntifying plant-specific codes and stardards that may apply, such as State-imposed requirements, Uniform Building Code, ACI or AISC standards.
2.3.2.3 Cleaning.
I All portions of the system th1t may contact oxygen shall be cleana_d as described in Section 3.4 of this report, and in accordance with CGA G-4.1, Cleaning Equipment for Oxygen Service.
I 2-7 I
I 2.4 INSTRUMENTATION AND CONTR01,,
This subsection discusses the instrumentation, controls, and monitoring associated with the hydrogen addition system.
The instrumentation and controls include all sensing elements, equipment and valve operating hand switches, equipment and valve status lights, process information instruments, and all automatic control equipment necessary to ensure safe and reliable operation. Table 2-1 lists the recomended trips of the hydrogen I
addition system. The instrumentation shall provide indication and/or recording of parameters necessary to monitor and control the system and its equipment. The instrumentation shall also indicate and/or alarm abnormal'or undesirable conditions. Table 2-2 lists the recomended instrumentation and functions. This I
table also includes instrumentation for hydrogen and oxygen supply options.
System instrumentation and controls shall be centralized where feasible to facili-tate ease of control and observation of the system. As a minimum, there shall be a system trouble alarm and/or annunciator provided in the main control room.
2.4.1 H.ydrogen Injection Flow Control Parallel flow control valves should be provided in the hydrogen injection line, I
for system reliability and maintainability. If flow control is automatic, hydrogen flow rate should be controlled as a function of pl. tnt process parameters such as steam or feedwater flow.
The capability should be provided to adjust flow rate to each pump manually, if I
this is found to be necessary to achieve adequate hydrogen distribution.
Manual isolation valves shall be provided in each pump injection line to accom-modate pump-out-of-service conditions. Individual pump injection lines should contain automatic isolation valves interlocked to the corresponding pump, so that hydrogen is not injected into a pump that is not running.
Provisions for shut-off of hydrogen injecticn shall be provided in the control room.
I l
l 2=8
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_.,y.
___,.,,-,_7,_
y
l t>r.
Table 2-1 REC 0m ENDED TRIPS OF THE HYDROGEN ADDITION SYSTEM Limiting low power level per plant safety analysis (Control Rod I
Drop Accident). if required by Tech Specs Reactor SCRAM Operator request (manual)
+
Low residual oxygen in off-gas High area hydrogen concentration Low oxygen injection system supply pressure or flow Off-gas train or recombiner train trip High hydrogen flow I
Differential hydrogen inlet and outlet of system
- 0xygen concentration in hydrogen
- I I
I
- Electrolytic generation option.
W I
I 2-9
m M
M M
M M
M M
M M
M Table 2-2 HYDROGEN ADDITION SYSTEM INSTRUENTATION AND CONTROLS I
Portion of Parameter Measured or High Low Auto Overall System Function Perfonned Record _
Indicate Alare Alarm Control Injection systems Hydrogen flow
' (X)
X Trip
- on (H2 and/or 0 )
high flow 2
Oxygen flow (X)
X c
I Offgas residual oxygen (X)
X Trip on low oxygen g
Recirc water dissolved oxygen (X)
X X
l Area hydrogen concentration (X)
(X)
Trip l
Hydrogen injection line pump interlock Isolate when f
pump is not in operation
- If this supply option is used
- for electroytic generation option X = required.
(X) = recosamended.
m m
m m
m M
M Table 2-2 (Continued)
HYDROGEN ADDITION SYSTEM INSTRUMENTATION AND CONTROLS Portion of Parameter Measured or High Low Auto L
Overall System Function Performed Record Indicate Alarm Alarm Control Hydrogen supply Hydrogen storage tank level **
X (X)
Hydrogen storage tank pressure gauge" X
Hydrogen storage tank vacuum readout" X
Hydrogen gas supply pressure" X
i Hydrogen gas storage temperature" X
Differential flow rate"*
X X
X Trip
- 0xygen concentration in hydrogen X'
X X
Trip compression module"*
Hydrogen concentration in oxygen"
- X Trip m
b 0xygen supply Oxygen tank level gauge X
(X) j 0xygen tank pressure gauge X
0xygen tank vacuum readout connection X
- If this supply option is used i
- For electroytic generation option l
X = required.
l (X) = recommended.
l l
i
..i.
I 2.4.2 0xygen Injection Flow Control _
Parallel flow control valves should be provided in the oxygen injection system reliability and maintainability.
Oxygen flow rate shall be controlled to provide residual oxygen dow T
System controls shall be designed to ensure that oxygen injec I
g.
recombiners.
continues after hydrogen flow stops, so that all free hydrogen is safely recombined.
- 2. 4.'3 Monitoring I
Provision shall be made to monitor continuously the concentration of dis f
In obtaining samples of recirculation water oxygen in the recirculation water.
for this purpose, appropriate containment isolation shall be provided in I
3, 54, 55, 56, f
accordance with 10 CFR 50, Appendix A General Design Criteria F
f,i or 57.
L Provision should be made to monitor continuously the concentration of oxyge t
and/or hydrogen in the off-gas flow downstream of the recombiners.
I
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I I
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b L
t 2-12 I
._6 I-Section 3 SUPPLY FACILITIES 3.1 ~ GASEOUS HYDROGEN 3.1.1 System Overview Hydrogen gas can be supplied from either permanent high-pressure vessels or from transportable tube trailers. For the permanent storage system, gaseous hydrogen I
is stored in seamless ASME code vessels at pressures up to 2,400 psig and ambient temperatures. Transportable vessels are designed to 00T standards and store hydrogen at pressures up to 2650 psig at ambient temperatures. With either storage design, the gas is routed through a pressure control station which maintains a constant hydrogen supply pressure. In any event, the gaseous hydrogen system shall be provided by a supplier who has extensive experience in the design, operation and maintenance of associated storage and supply systems. Gaseous hydrogen shall be provided per CGA G-5 and G-5.3.
3.1.2 Specific Equipment Description 3.1.2.1 Hydrogen Storage Vessels. The hydrogen storage bank shall be composed of ASME code gas storage vessels. Each tube shall be constructed as a seamless vessel with swagged ends. Specific tube design shall be based on ASME Unfired Pressure Vessel Code,Section VI!!, Division 1 and Code Case 1205.
The tube bank shall be supported to prevent movement in the event of line failure and each tube shall be equipped with a close-coupled shut off valve. As an alternative, one safety valve per bank of tubes can be used, provided the safety valve is sized to handle the maximum relief from all tubes tied into the valve.
Each bank shall be equipped with a thermometer and a pressure gauge, a's is necessary for proper filling.
3.1.2.2 TranscortableHydrogenStorageVessej. Transportable hydrogen vessels shall be constructed, tested, and retested (every 5 years), in accordance with 00T specifications 3A, 3AA, 3AX, or 3AAX. All valving and instrumentation shall be identical to Section 3.1.2.1.
3-1
3.1.2.3 Pressure Reducing Station. The pressare control station shall be of a manifold design. The manifold shall have two (2) full-flow parallel pressure reducing regulators. 'The discharge pressure range of these regulators shall be adjustable to satisfy plant hydrogen injection requirements. Pressure gauges shall be provided upstream and downstream of the regulators. Sufficient hand valves shall be provided to ensure complete operational flexibility.
An excess flow check valve shall be installed in the manifold imediately down-stream of the regulators to limit the flow rate in the event of a line break. The stop-flow setpoint shall be determined by each plant and should be set between the maximum plant flow requirements and the full C of the flow control valves.
y 3.1.2.4 Tube Trailer Discharge Stanchion. A tube trailer discharge stanchion shall be provided for gaseous product unloading. The stanchion shall consist of a flexible pigtail, shut-off valve, check valve, bleed valve, and necessary piping. Filling apparatus shall be separated from other equipment for safety and convenience, and protected with walls or barriers to prevent vehicular, collision A tube trailer grounding assembly shall be provided for each discharge stanchion to ground the tube trailer before the discharge of hydrogen bagins.
I.
3.,1. 2. 5 Interconnecting Pipeline. All equipment and interconnecting piping supplied with this system shall be installed in compliance with the following standards:
American National Standards Institute (ANSI) B31.1, Power Piping, or B31.3, Chemical Plant and Petroleum Refinery Piping.
National Fire Protection Association (NFPA) 70, National Electrical Code.
NFPA-50A, Bulk Hydrogen Systems.
All applicable local and national codes.
There are several suitable field installation techniques which are based on industrial experience. The following are guidelines which may be used for field connections:
g 32 1
Copper-to-Copper, Brass-to-Brass, and Copper-to-Brass Socket Braze Joints.
--Silver Alloy 45% Ag, 15% Cu, 16% Zn, 24% Cd., ASTM B260-69T and AWS AS.8-69T, BAG-1 Melting Range-Solidus-607.2*C Liquidus-618.3*C
--Flux Working Range 593.3*C to 871.1*C Copper, Brass, Carbon Steel, and Stainless Steel N.P.T.
Threaded Joints.
--TEFLON
- Tape **
SCOTCH *** Number 48
~
Tape ** or equal.
-195.5'C to +204.4*C, O to 3,000 psig. Wrapped in direction of threads.
Flange Joints (On all Materials).
--Ring Gasket Material Low Precut T.F.E.
Pressure (720psig impregnated asbestos, maximum) 1/16 inch thickness.
Garlock 900 or equal.
-195.5'C to +168.3*C, O to 900 psig.
--Ring Gasket Material, High FLEXITALLIC**** Type.
Pressure Material to be 0.175 inch thick 304 stain-less steel with TEFLON I
filler and 0.125 inch carbon steel guide ring.
- TEFLON is a trademark of E. I. duDont de Nemours & Co., Wilmington, DE 1989.
- If tape is used, electrical continuity / grounding of each piping section should be confirmed.
- SCOTCH is a trademark of 3M Company, St. Paul, MN 55101.
- FLEXITALLIC is a trademark of Flexitallic Gasket Co., Be11mawr, NJ 08031.
3-3
I I
--Antiseize Compound For flange face, nut, and bolt lubrication.
Halocarbon 25-55 grease or equal. -195.5'C to I
+176.6'C, O to 3,000 psig. 00 NOT USE ON ALUMINUM, MAGNESIUM, OR THEIR ALLOYS UNDER 1
CONDITIONS OF HIGH TORQUE OR SHEAR.
Carbon Steel Stainless Steal, and Aluminum Alloys Socket and I
Butt Welds.
--Welding Procedure Gas Metal Arc Welding I
(GMAW), Gas Tungsten Arc Welding (GTAW),
Shielded Metal Arc Welding (SMAW), or I
Plasma Arc Welding (PAW);withappropriate filler material and shielding gas. Proper I
surface and joint preparation (in regard to cleaning and I
clearances) should be exercised.
3.1.2.6 Ccmponent Cleaning. All components that contact hydrogen must be free of I
moisture, loose rust, scale, slag, and weld spatter; they must be essentially free of organic matter, such as oil, grease, crayon, paint, etc. To meet these objec.
tives, system components shall be cleaned in accordance with standard industrial practices, as recomended by the gas supplier, prior to and following system fabrication.
3.2 LIQUID HYDROGEN 3.2.1 System Overview Liquid hydrogen is stored in a vacuum-jacketed vessel at pressures up to 150 psig and temperatures up to -403*r (saturated). Based on data relating hydrogen injec-tion pressures to BWR plant power levels, hydrogen supply froid a liquid source can be provided directly from a tank or pumped into supplemental gaseous storage.
Gaseous storage requirements are identified in Section 3.1.
The required supply pressure shall be based on pressure requirements at the point of hydrogen I
injection and line losses from the hydrogen supply system to the injection point.
3-4 l-
i Feedwater pressure requirements and line losses must not exceed 120 PSIG if hydrogen is to be supplied directly from a liquid tank.
In any event, the liquid hydrogen system shall be provided by a supplier who has I
extensive experience in the the design, operation and maintenance of associated storage and supply systems, such as cryogenic pumping. Liquid hydrogen shall be provided in accordance with CGA G-5 and G-5.3.
3.2.2 Specifle Equipment Description I
3.2.2.1 Cryogenic Tank. Tanks for liquid hydrogen service are available with capacities between 1,500-gallons and 20,000-gallons. An " inner vessel" or " liquid container" is supported within an " outer vessel" or " vacuum jacket " with the
. space between filled with insulation and evacuated. Necessary piping connects from inside of the inner vessel to outside of the vacuum jacket. Gages and valves I
to indicate the control of hydrogen in the vessel are mounted outside of the vacuum jacket. Legs or saddles to support the whole assembly are welded to the outside of the vacuum jacket.
Inner vessels are designed, fabricated, tested, and stamped in accordance with I
Section VIII, Division 1 of the ASME Code for Unfired Pressure Vesse,1s. Materials suitable for liquid hydrogen service must have good ductility properties at temperatures of -422"F per CGA G-5.
In addition to ASME Code inspection require-ments, 100% radiography of the inner vessel longitudinal welds shall be completed. The tank outer vessel shall be constructed of carbon steel and shall I
not require ASME certification.
Insulation between inner and outer vessels shall be either perlite, aluminized mylar or suitable equal. The annular space should be evacuated to a high vacuum of 50 microns or less.
Tank control piping and valving should be installed in accordance with ANSI B31.1 or 831.3. All piping shall be either wrought copper or stainless steel. The following tank piping systems shall be subsystems.
I Fill circuit, constructed with top and bottom lines so that the vessel can be filled without affecting continuous hydrogen supply.
Pressure-build circuit, to keep tank pressures at operational levels.
I 35
I 1
Vacuum-jacketed liquid fill and pump circuits, where i
applicable.
I 3.2.2.2 Overpressure protection Syste3 Safety considerations for the tank shall be satisfied by dual full flow safety valves and emergency backup rupture discs.
The primary relief system shall consist of two sets of a minimum of one (1) rupture disk and safety valve piped into separate " legs." Relief devices shall be connected in parallel with other relief devices. The system shall be coupled by a 1
3-way diverter valve or tie bar interlock so that one leg is opened when the other is closed. With this arrangement, a minimum of cne safety valve and one rupture disk will be available at all times. The dual primary. relief systems with 100%
standby redundancy allows maintenance and testing to be performed without sacrificing the level of protection from overpressure.
El The primary relief system shall comply with the provisions of the American Society of Mechanical Engineers (ASME) Pressure Vessel Codes and the Compressed Gas I
Association (CGA) Standards.
I.
The tank shall also be supplied with a secondary relief system not required by the ASME Codes. This system shall be totally separate from the primary relief system. It shall consist of a laced open valve, a rupture disk, and a secondary I
vent stack. This rupture disk shall be designed to burst at 1.33 MAWP.
Supply system piping that may contain liquid and can be isolatable from the tank relief valves shall be protected with thermal relief valves. All outlet connec-tions from the safety relief valves, rupture devices, bleed valves, and the fill I
line purge connections shall be piped to an overhead vent stack, per CGA C-5 Section 7.3.7.
I Two relief devices shall be installed in the tank's outer vessel to relieve any excessive pressure buildup in the annular space.
Hydrogen tanks and delivery vehicles shall be grounded per CGA P-12.' Sections 5.4.5 and 5.7.1.2.
Excess flow protection shall be added to the tank's liquid piping wherever a line I
break' would release a sufficient amount of hydrogen to threaten safety-related structures. An acceptable methodology is identified in Section 4.2.2 " Pipe Breaks."
g 3-e
I 3.2.2.3 Instrumentation. The tank shall be supplied with a pressure gauge, a I
liquid level gauge, and a vacuum readout connection. These gauges are sufficient for normal monitoring of the tank condition. Instrumentation for remote monitor-ing, such as high/ low-pressure switches, pressure and level transmitters may be added. A listing of supply system instrumentation and control is identified in Section 2.4.
3.2.2.4 Liquid Hydrogen Pump and Controls. The liquid hydrog'en pump shall be of proven design to provide ' continuous hydrogen supply in unattended, automatic operation. The following items comprise the more important system controls.
3.2.2.4.1 Positive isolation valve. A positive isolation valve shall be used W
to control the liquid feed into the pumping system per NFPA 508. The valve shall be a failed-closed, pneumatically operated valve. The valve shall only be open during pump operation, shall close in any fault mode, and shall be able to be remotely overridden in case of emergency.
3.2.2.4.2 System overpressure shutdown. Although the system is protected by safety relief valves and rupture disc's, system overpressure shall be avoided by shutting down the pumps at high pressure.
1 3.2.2.4.3 Temperature indicating switch. A temperature switch shall con-tinuously monitor the downstream gas line for low temperature and shall trip the liquid pump to protect downstream equipment from low temperatures.
3.2.2.4.4 pump operation. Pump operation shall be continuously and automatically monitored. Operation which results in pump cavitation, high I
temperature at the pump discharge, or low temperature downstream of the vaporizer shall cause t'he pump to be shut down by the remote control panel.
The fault shall be indicated on the remote control panel by an audible alarm and light indication.
3.2.2.4.5 Purging of controls. All electrical components in hydrogen service should be designed in accordance with NFPA 70. Nitrogen or air shall be used I
for purging pump n.otors, control panels and valves.
3.2.2.5 Interface with Gaseous System. Liquid hydrogen pump systems typically I
require a gaseous storage system as a surge or back-up to plant hydrogen supply.
These storage systems shall be designed in accordance with Section 3.1, GASEOUS
I
\\
\\
HYDROGEN. Whenever a gaseous back-up is used in conjunction with a liquid hydrogen system, switchover controls shall be provided.
3.2.2.6 Vacorization. Vaporization of the liquid hydrogen shall be achieved by the use of ambient air vaporizers. Vaporizer design, installation and operation shall take guidance from NFPA SOA and 508.
The vaporizer should feature a star fin design and aluminum alloy construction.
I For a combined liquid and gaseous storage system, the vaporizers used should have a design pressure consistent with plant injection pressure requirements. The units may be piped in parallel such that each unit can operate independently. Parallel vaporizer assemblies shall be sized for the peak hydrogen flow required for each plant and shall provide for periodic intervals for defrosting, as appropriate.
I Other atmospheric vaporization systems may be utilized if their capacity is -
demonstrated to be adequate for the plant flow and ambient conditions.
I For a pumped liquid only storage system, the vaporizer must withstand maximum pressures generated from the cryogenic pump. These vaporizers shall be equipped I
with stainless steel linin'g designed to 3500 psig.
3.3 ELECTROLYTIC 3.3.1 System Overview The disassociation of water by electrolysis is an acceptable method of obtaining the gases needed for hydrogen water chemistry. This can be done on site and the I
gases can conveniently be generated at the rate used. The electrolytic gas generator should be proven equipment, the same as used in other industrial applications. Depending on the generator operating pressure, either hydrogen compressorsor.pressurebreakdown(control)isutilizedtomatchplanthydrogen injection pressure requirements. The electrolytic system shall be provided by a i
supplier who has extensive experience in the design, operation and maintenance of these systems.
3.3.2 Specific Equipment Description Equipment and processes associated with the electrolytic method of providing the HWC gases include rectifiers, the electrolytic cells, scrubbers, compressors, piping, valves and associated controls.
I 3-8 I
o
=
I 3.3.2.1 Gas Generator. Water is disassociated into hydrogen and oxygen in the electrolytic cells by the direct current electricity provided through the rectifiers. The water flows into the cells, at the rate dissociated, where it forms a solution with the electrolyte used to carry the electrical current form one electrode to the other. Hydrogen is fonned at one electrode and oxygen at the I
other, which is dependent on current direction. The electrodes are separated by a membrane which is permeable for the electrolyte but which keeps the gas bubbles separate as they rise to the collection outlets of the cells.
3.3.2.2 Vessels. Unless exempted because of size (smaller than 120 gallons of I
water) or pressure (less than 15 psig), for industrial safety reasons, the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section VIII, Division 1 shall apply to the design and construction of vessels. The code design pressure and temperature shall be I
selected to be above the highest pressure and temperature that can be reached during operation.
3.3.2.3 Piping. Piping and related equipment shall conform to the American National Standard Code (AMSI) for Piping B31.1 or B31.3 except that non metallic-I materials may be used in low pressure applications if supported by experience and/
or tests which have demonstrated their suitability for the service conditions, and operating pressure and temperature conditions are within the material manufac-turer's specifications. Typical non-metallic materials are limited to pressures below 150 PSIG and temperatures below 140'F.
I 3.3.2.4 Valves. Valves should be designed such that the prevention of hydrogen leakage into an enclosed area does not rely on a single packing. Valves in'any portion of the hydrogen flow path that is at subatmospheric pressure should be designed for zero inleakage of air.
Welded connections shall be used on all hydrogen piping that may operate below atmospheric pressure.
i I The oxygen flow path, including valves, shall not contain greases, oils, or other combustible materials which can ignite at the conditions of temperature and velocity.
I I
3-9 I
I Valves in the hydrogen flow path in or downstream of any point where the pressere can be belcw atmospheric should hcve spark resistant rubbing and impacting surfaces if the rubbing or impacting velocities can exceed the spark threshold.
A soap bubble test shall be performed to assure a leak tight system after I
installation.
3.3.2.5 Comoressors. If a mechanical method of gas compression is employed, it should be located at the gas generation facilities. A gas pressurization method may be employed which does not require mechanical compressors and which permits I
gas generation at a rate equal to gas usage. However, if a. mechanical compressor is used, it shall meet the following requirements:
(a) the pressure gradient at any seal should be outward whenever the compressor contains hydrogen; I
(b) the shaft seal leakage shall not discharge into any enclosed space that is not either continuously purged with an inert gas or ventilated to avoid an explosive mixture of air and hydrogen assuming the greatest potential rate of shaft seal leakage; I
(c) the compressor shall not introduce unacceptable levels of organics and/or fluorides / chlorides into the hydrogen; (d) the compressor shall be designed to permit purging of all compartments before and after maintenance; I
(e) the compressor should be dry lubricated and should be of the diaphragm type.
Where gas storage volumes are used, their size sheuld be minimized. Where practical for the application, a type of compressor should be used that does not require surge tanks.
3.3.2.6 Gas Generator Shelter. Passive ventilation shall be provided for the gas generating room of the equipment shelter. Inlet openings shall be provided at floor level in exterior walls and outlet openings shall be located at the high g
point of the room. Inlet and outlet openings shall have an arrangement and 3
sufficient area to assure fault-free passive ventilation. The discharge from outlet openings shall be directed to a location that has no ignition sources.
I The gas generating room of the shelter shall be partitioned away from all other rooms that could contain ignition sources. The rectification equipment shall be I
partitioned away from the gas generation equipment.
I 3-10 I
I~
~
Equipment for space heating of the gas generating room st all not contain any ignition sources and shall not allow gases, including air, to pass out of the room
.to an ignition source in a heating system.
Windows and doors shall be in exterior walls only. Windows shall be made of shatterproof glass or plastic in metal frames.
1 The shelter shall be of noncombustible materials (except for the transparent materials used in windows).
3.4 LIQUID OXYGEN 3.4.1 System Overview Liquid oxygen is stored in a vacuum-jacketed vessel at pressures up to 250 psig and temperatures up to -251*F (saturated). Oxygen taken from the vessel shall be I
vaporized through ambient air vaporizers and routed through a pressure control station which maintains gas pressures within the riesired range. The liquid oxygen system shall be provided by a supplier who has extensive experience in the design, operation and maintenance of associated storage and supply systems. Liquid oxygen shall be provided per CGA G-4 end G-4.3.
I 3.4.2 Specific Equipment Description I
3.4.2.1 Cryogenic tank. Tanks for liquid oxygen service, with capacities between 3,000 gallens and 11,000 gallons are similar in principle. An ' inner vessel" or
' liquid container" is supported within an " outer vessel' or " vacuum jacket," with insulation provided in the space between the tanks. Necessary piping connects from inside of the inner vessel to outside of the vacuus jacket. Gages and valves I
to indicate the control of product in the vessel are mounted outside of the vacuum jacket. Legs or saddles to support the whole assembly are welded to the outside of the vacuus jacket.
Inner vessels shall be designed, fabricated, tested and stamped in accordance with i
Section VI!!, Division 1, of the ASME Ccde for Unfired Pressure Vessel.s.
Materials suitable for liquid oxygen service must have good ductility properties at cryogenic temperatures of -300*F per CGA G-4.
The outer vessel should be censtructed of carbon steel and does not require ASME certification.
I I
3-11 I
I Insulation between inner and outer vessels shall be either perlite, aluminized mylar or suitable equel. The annular space should be evacuated to a high vacuum of 50 microns or less.
Tank control piping and valving should be installed in accordance with ANSI B31.1 I
or B31.3. All piping shall be either wrought copper or stainless steel. The following tank piping systems shall be subsystems:
Fill circuit constructed with too and bottom lines so that the vessel can be filled without affecting system operation.
I Pressure build circuit, to keep tank pressures at operational levels.
Economizer circuit, to preferentially feed oxygen gas frcm vessel vapor space to process.
Since the analysis in Section 4.4 assumes the vapor cloud originates from the tank I
location, the tank and its foundation shall be designed to remain in place during the design basis tornado.
I 3.4.2.2 Overpressure Protection System. Safety considerations for the tank shall be satisfied by dual full flow safety valves and emergency backup rupture discs.
I The primacy relief system shall consist of two sets of one (1) safety valve and one (1) rupture disc piped into separate legs, coupled by a three-way valve. This dual primary relief system with 100% standby redundancy allows maintenance and testing to be performed without sacrificing the level of protection from overpressure.
The primary relief system shall comply with the provisions of the ASME Pressure Vessel Codes and the Compressed Gas Association (CGA) Standards.
Annular space safety heads shall be provided to relieve any excess positive pres-I sure builoup which might result from a leak in an inner vessel. Supply system piping that may contain liquid and can be isolatable from the tank relief valves shall be protected with thermal relief valves.
The tank shall be supplied with a pressure gauge, a liquid level gauge, and a I
vacuum readout connection. These gauges are sufficient for normal monitoring of the tank condition. Instrumentation for remote monitoring, such as high-low-pressure switches, pressure and level transmitters may be added. A listing of supply system instrumentation and control is identified in Section 2.4.
3-12 I
3.4.2.3 Vaporization. The vaporization of the liquid oxygen shall be achieved..
the use of ambient air vaporizers.
The vaporizer should feature a star fin design and extruded aluminum alloy con-struction. The vaporizers shall have a minimum design pressure of at least 300 psig. The units shall be piped in parallel such that each unit can operate independently. Parallel vaporizer assemblies shall be sized to handle peak plant I
flow. requirements and shall provide for periodic intervals for defrosting, as appropriate.
I 3.4.2.4 Pressure Control Station. The pressure control station shall be of a manifold design. The manifold shall have two (2) full-flow parallel pressure I
reducing regulators. The discharge pressure range of these regulators shall be adjustable to sittisfy plant oxygen injection requirements. Pressure gauges shall be provided upstream and downstream of the regulators and sufficient hand valves shall be provided to ensure complete operational flexibility.
I Protection of downstream equipment from low oxygen temperatures shall be included in the system design.
I 3.4.3 Materials of Construction for Oxygen Piping and Valves The design and installation of oxygen piping and related equipment shall be in accordance with ANSI B31.1 or B31.3 and the following guidelines for material selection for oxygen systems.
Observations of past oxygen fires indicate that ignition can occur in carbon steel and stainless steel piping systems operating at, or r. ear, sonic velocity. Fric-tion from high velocity particles is considered to be the source of ignition.
Copper, brass, and nickel alloys have the characteristic of melting at tempera-I tures below their respective ignition temperatures. This makes these materials extremely resistant to ignition sources, and once ignited, they exhibit a much slower rate'of burning than carbon or stainless steels.
As a result of these observations, the following materials, in order of prefer-I ence, are acceptable for oxygen service. In the case of carbon steel or stainless steel, the maximum velocity of gaseous oxygen shall be within guidelines estab-lished by the Compressed Gas Association CGA Pamphlet CGA-4.4, " Industrial Practices For Gaseous Oxygen, Transmission and Distribution Piping Systems."
I 3-13 I
I I
Copper Brass Monel Stainless Steel Carbon Steel If steel pipe is to be used for the system and some local flow conditions could cause the velocity to exceed that established in CGA G-4.4, then that portion of the system must be converted to a copper-based alloy and extend a minimum of 10 diameters downstream of the point of return to the allowable velocity. These local flow conditions may occur at control valves, crifices, branch line take-off I
points, and in the discharge piping of safety relief devices.
Valves that open rapidly are not suitable for oxygen service, since rapid filling of an oxygen line will result in a temperature increase due to adiabatic compres-sion. As a result of this phenomenon, ball valves and automatic valves may only I
be used with the following restrictions:
Valve bodies shall be made of a copper alloy. Balls shall be I
monel or brass. Valve seats and seals should be teflon, non-plasticized Kel-F, Kalrez, or Viton.
Ball valves may not be used as process control valves in I
throttling or regulating service. Ball valves may be used as isolation valves, emergency shutoff valves, or vent or bleed valves where they are either fully open or fully closed.
Pneumatic or electric ball valves used for on-off services shall have ar. actuation time from fully closed to fully open of 4 seconds or greater for pressures up to 250 psig. No I
restriction is placad on actuation time from fully open to fully closed. Piping immediately downstream must be a straight run of copper-bearing material for a minimum of 10 diameters.
I Pneumatic or electric ball valves used for emergency service may be fully open or fully closed to the emergency position, with no restrictions on actuation time.
I Suitable valve packing, seats, and gasket materials are listed below in order of preference from the oxygen compatibility basis only.
I Teflon Glass-filled Teflon l
Nonplasticized Kel-F I
3-14 w.
I' Garlock 900 Viton or Viton A 3.4.4 0xygen Cleaning All piping, fittings, valves, and other material which may contact oxygen shall be I
cleaned to remove internal organic, inorganic, and particulate matter in accordnace with CGA-4.1. Observation has shown that ignition can occur in properly designed piping systems when foreign matter is introduced. Therefore, removal of contaminants such as grease, oils, thread lubricants, dirt, water, filings, scale, weld spatter, paints, or other foreign material is essential.
I Cleaning should be accomplished by precleaning all parts of the system, maintaining cleanliness during construction, and by completely cleaning the system after. construction.
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Section 4 SAFETY CONSIDERATIONS 4.1. GASEOUS HYOROGEN 4.1.1 Site Characteristics of Gaseous and Liquid Hydrogen 4.1.1.1 Overview. Review of the following site characteristics shall be con-ducted by each BWR facility in locating the gaseous and/or liquid hydrogen supply systems:
1.
Location of supply system in proximity to exposures as addressed in NFPA 50A and 508.
2.
Route of hydrogen delivery on site.
3.
Location of supply system in proximity to safety-related equipment.
4.1.1.2 Specific Considerations.
4.1.1.2.1 Fire Protection. The area selected for hydrogen system siting shall meet or exceed all requirements for protection of personnel and equipment as addressed in NFPA SOA and 50B, gaseous and liquified hydrogen systems, respectively. Each standard identifies the maximum quantity of hydrogen storage permitted and the minimum distance from hydrogen systems to a number of exposures.
The need for additional fire protection for other than the hydrogen facility shall be determined by an analysis of local conditions of hazards on-site.
exposure to other properties, water supplies, and the probable effectiveness of I
plant fire brigades in accordance with NFPA SOA and 508.
4.1.1.2.2 Security. All hydrogen storage system installations shall be completely fenced, even when located within the owner-controlled area. Lighting shall be installed to facilitate night surveillance.
4.1.1.2.3 Route of hy'drogen delivery on site. Each plant should determine the route to be taken by hydrogen delivery trucks through on-site and cff-site 4-1 I
I I
areas. In order to protect the hydrogen storage area from any vehicular accidents, truck barriers shall be installed around the perimeter of the system installation.
Within the plant security area, all deliveries shall be controlled per the requirements of 10 CFR 73.55.
4.1.1.2.4 Location of storage system to safuy-related structures. Each plant shall determine that the location of the hydrogen storage system is acceptable relative to safety-related structures and equipment considering the hazards described in Sections 4.1.2, 4.1.3, 4.2.1 and 4.2.2.
4.1.2 Gaseous Storage Vessel Failure Gaseous storage vessels in the scope of this report are the comercially available, seamless, swagged-ended vessels that are commonly referred to as "hydril tubes." This section addresses the non-mechanistic rupture failure of sir.gle vessels and the separation distances required to avoid damage to safety-I related equipment. Simultaneous failure of multiple vessels is not addressed because the inherent strength of the vessel makes them unsusceptible to failure from outside forces (e.g. seismic, tornado missiles, etc.).
This feature eliminates comon cause vessel failures so that the maximum postulated instantaneous release is the fully pressurized contents of the largest single vessel. The potential consequences of such a release, a fireball or an explosion, are addressed in order.
I t
4.1.2.1 Fireball. The thermal flux versus distance from the fireball center are shown on Figure 4-1 for the two most comon vessel sizes. These fluxes and I
durations will not adversely affect safety-related structures. However, each utility shall review any unique site characteristics to assure all safety-related equipment will function in the event of a fireball.
i 4.1.2.2 Explosion. When a gaseous storage vessels ruptures, the expansion of the high pressure gas results in rapid turbulent mixing with the surrounding air. In I
the case of gaseous hydrogen, the release will go through the detonation limits of 18.3 - 59% before the wind can translate the mixture. Consequently, any explosion blastwaves will originate at the vessel rupture site. For this report, it is conservatively assumed that 100% of the vessel contents will contribute to the I
4-2 I
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Key Vessel Size (sef) Fireball Duration (sec)
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Distance from Fireball Center (ft)
Figure 4-1. Thermal flux vs. distance from fireball center for gaseous hydrogen storage system.
I 4-3 I
I blastwave and that the TNT-hydrogen equivalence is 20% on an energy basis (5207. on a mass basis)..This translates to 27.1 lbs. of TNT per 1000 standard cubic feet (SCF) of gaseous hydrogen. Using this conversion factor and U.S. Army Technical Manual TM5-1300, blast overpressures and impulses can be calculated as I
functions of distance from the vessel location. These blast parameters could then be compared to the dynamic strength of safety-related structures.
I The concept of dynamic strength of structures is illustrated on Figure 4-2 for the threshold of partial demolition of re.sidential brick construction. This curve I
represents many " data points" for homes damaged during World War II frem known size bombs at various standoff distances. Brick buildings subjected to incident impulses /overpressures to the right and above this curve will receive more severe damage. Points to the left and below the curve will be under the threshold for this damage criterion. In order to determine the required separaticn distances, I
similar curves to this could be generated for specific related structures at each nuclear power plant. As an alternative to individual strength calculations, it would be conservative to assume that the heavily reinforced concrete safety-related structures could withstand the blast parameters for this damage criterion. Further discussions of this criterion can be found in Reference 4-1.
I Therefore, the minimum required separation distances from the storage vessel to safety-related structures or equipment for the event of an explosion at the storage vessel site shall meet the criterion depicted on Figure 4-3.
Alterna-tively, a dynamic strength analysis may be performed for a specific safety-related I
structure if closer storage is desired. In either case, the vessel (s) and the foundation shall be designed to withstand the " design basis tornado character-1stics" as outlined in Regulatory Guide 1.76 so as a minimum the vessel (s) will remain in place.
I 4.1.3 Gaseous Pipe Breaks This section addresses the requirements for hydrogen piping systems attached to I
gaseous storage vessels up to the point where excess flow protection is provided. The criteria for acceptable siting for the event of a pipe break are:
1.
Dilution of resultant release below the lower flammability limit of 4% before reaching safety-related air intakes.
2.
Maximum overpressures below the blast damage criterion outlined I
in Section 4.1.2 I
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vs. vessel size for gaseous hydrogen storage system.
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I It is conservatively assumed that all releases occur while the storage vessel is at 2,450 PSIG. This is the maximum allowable working pressure of the majority of commercially available vessels.
Gaseous releases at elevated pressures result in supersonic jet velocities and a
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dispersion process that is momentum-dominated. Under these conditions, the Gaussian dispersion model unrealistically overestimates the amount of hydrogen in the explosive region and the distance to the lower flammable region. Therefore, I
th'ese properties of gaseous re. leases were calculated using a jet dispersion model described in Reference 4-1.
The results of t'his modeling are shown in Figure 4-4 as minimum separation distances between safety-related air intakes versus hole size or inside diameter of the pipe. For evaluating separation di-tances to safety-related structures, the effect of the maximum amount of hydrogen in the detonable region for pipe breaks less than 1-1/2 inch diameter is below the blast damage criterion shown in Figure 4-2.
Therefore, all non-cryogenic gaseous piping in the scope o.~ this report shall be less than or equal to 1-1/2 inch diameter. Each utility shall determine that the storage vessel piping and location meet these requirements or I
show that less stringent criteria should be applied to a specific case. An example of such an exception would be if the air intakes have automatic shutters controlled by hydrogen analyzers thus preventing the ingestion of a flamable mixture.
4.2 LIQUID HYDROGEN 4.2.1 Storage Vessel Failure I
For this report, storage vessel failure is defined as a large breach resulting in the rapid emptying of the entire contents of liquid hydrogen. It is assumed that the tank is full at the time of fr.ilure and that the entire spill vaporizes instantaneously. The following enumerates potential causes of vessel failure and the required design features that mitigate or alleviate these potentials.
Seismic The tank and its foundation shall be designed to meet the seismic criterion for critical structures and equipment at the I
plant site (i.egsign basis earthquag It is preferable to seismically suppor; aii ii A h 4 vgen piping. If this is-not possible, the liquid hydrogen piping shall be seismically I
supported up to and including excess flow protection devices.
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l 4-8 I
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Tornado and Tornado Missiles The tank and its foundation shall be designed to withstand the
" design basis tornado characteristics" as outlined in Regulatory Guide 1.76. As a minimum, the tank shall remain in place so that any liquid spillage will originate from the tank I
location.
Design basis tornado-generated missiles are capable of breaching all known commercially available liquid hydrogen storage vessels. Therefore, tornado missiles are a potential cause of " storage vessel failure."
Aircraft A large aircraft crashing directly into the storage area is capable of breaching all known comercially available liquid I
hydrogen storage vessels. Therefore, aircraft crash is a potential cause of " storage vessel failure."
Fire The overpressure protection system shall be sized to accommodate the worst-case vaporization rate caused by a hydrocarbon fire engulfing the outer shell with loss of vacuum and hydrogen in the annulus of the double-wall storage tank (as per Compressed Gas Association 5.3 ar.d ASME Section VIII requirements).
Flog The following flood conditions could result in vessel failure:
High water reaches the top of the vent stack for the overpressure p-Otection system.
High flood velocities dislodge the tank.
Under either condition, water could enter the vent system and I
defeat the overpressure protection system. Therefore, the tank shall be located such that maximum flood heights cannot exceed the vent stack elevation and such that potent;al flood velocities cannot damage the vent stack cr dislodge the tank.
Vehicle Imoact The storage vessel shall be protected from the impact of the I
largest vehicle used on-site by a barricade capable of stopping such a vehicle.
Vessel Structural Failun
+
The. storage vessel shall be designed, constructed, inspected and operated to assure an extremely low likelihood of tank I
structural failure during its tenure on site. A vessel designed in accordance with this document complies with this low probability requirement.
1 4-9 I
I 4.2.1.1 Fireball. For the two potential causes of " storage vessel failure,"
tornado missiles and aircraft impact, a fireball at the tank location is the expected result. Themajorreasonsforthisisthehighignitabilityofhydrogen and the density of ignition sources in the aftermath of these causal events.
Details of these considerations are given in the report for the Dresden plant (Reference 4-1).
The thermal flux versus distance from the fireball center (tank locatien) is shown on Figure 4-5 for the range of commercially available tank sizes. The durations of the various fireball sizes are also given. These fluxes and durations will not el adversely affect equipment or personnel enclosed in concrete / steel safety-related structures. However, each utility shall review any unique site characteristics to assure all safety-related equipment will functicn in the event of a fireball.
4.2.1.2 Explosion at Tank Site. Although an. explosion is not expected, safety-related structures and equipment shall be verified to be capable of withstanding a detonation occurring at the site of the tank installation. For the instantaneous release of the entire tank contents, the following were used to determine blast parameters for an explosion at the tank site.
1.
Gaussian F weather stability 2.
Deton'ation limits of hydrogen, 18.3-59%
3.
TNT - hydrogen equivalent of 20% on an energy basis (520% on a massbasis)
The above results in an equivalence of 1.37 lbs of TNT per gallon of tank size.
Using this conversion factor and U.S. Army Technical Manual TMS-1300 and the damage criterion outlined in Section 4.1.2.2, required separation distances have been determined as a function of tank size and are shown on Figure 4-6.
There-fore, the minimum required separation distances from the storage t ak to safety-related structures or equipment for the event of an explosion at the tank site shall meet the criterion depicted on Figure 4-6.
Alternatively, a dynamic strength analysis may be performed for a specific safety-related structure if' closer siting is desired.
4.2.2.
Pipe Breaks This section addresses the requirements for gaseous and liquid hydrogen piping systems attached to the storage vessel up to the point where excess flow protection is provided. The criteria for acceptable siting for the event of a I
4-10
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I Figure 4-6. Minimum required separation distance vs. liquid hydrogen storage tank size for instantaneous release of entire tank contents and explosion at tank site F weather stability.
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4-12
I pipe break are the same as outlined in Section 4.1.3.
It is conservatively I
assumed that all releases occur while the storage vessel is at 150 psig (the maximum allowable working pressure of the majority of commercially available tanks).
4.2.2.1.
Gaseous Piping. The same dispersion model for momentum-dominated jets I
discussed in Section 4.1.3 applies to gaseous releases from liquid storage tank piping with the appropriate release conditions for saturated vapors. The results of this modeling are shown in Figure 4-7 as minimum separation distances between safety-related structures and air intakes versus hole size or inside diameter of piping not protected with excess flow devices. Each utility'shall determine that the storage vessel piping and location meet these minimum requirements or show that less stringent criteria should be applied to a specific case. An example of such a suitable exception would be if the air intakes are provided vith autcmatic shutters controlled by hydrogen analyzers to prevent the ingestion of a flamable mixture.
4.2.2.2 Liquid Piping. The vapor cloud formed by the flashing and rapid vaporization of a liquid release is nearly neutrally buoyant and has little momentum associated with its formation. For these conditions, a Gaussian dispersion model is employed and it is conservatively assumed that liquid discharges will instantaneously vaporize.
The minimum required separation distances to safety-related structures and air intakes, using the above assumptions, are given on Figure 4-8 as a function of discharge rate. These distances shall be applied to all liquid piping, including I
those from any pump discharges, that are not seismically supported or protected by excess flow devices. For convenience, hole size or inside diameter of pipe for the worst-case break geometry is also plotted on Figure 4-8.
4.3 ELECTROLYTIC 4.3.1 General i
The electrolytic supply option need not constitute storage of hazardous materials on-site if it operates at approximately atmospheric pressure and involves the storage of no more than 2500 scf of hydrogen and 250 scf of oxygen. If these limits are met, and the system is designed as described in Section 3.3, it need i
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Figure 4-8. Minimum required separation distance vs. hole size and discharge rate forliquid re! eases from 150 psiliquid hydrogen storage tank F weather stability,1 m/s wind velocity.
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4-15
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only be analyzed as described below. Other system designs have not yet been considered. Compressed gases utilized in conjunction with electrolytic systems I
shall be in accordance with Sections 3.1 and 4.1.
Events important to industrial safety (abnormal transients, accidents and external events) must be evaluated to identify those which could result in any of the following conditions:
1.
Hydrogen accumulation to a combustible mixture in an enclosed.
space.
2.
Air or oxygen mixing with hydrogen within electrolytic system components.
3.
Hydrogen fires.
When the potential exists for the above undesired conditions to occur, appropriate I
mitigating features shall be incorporated in the design or operation of the system or the consequences with respect to plant and personnel safety shall be evaluated by the owner.
4.3,.2 Purity of Gases The gases as collected from the electrolytic cells in a well working system will be over 99% pure and concentration of the oxygen in the hydrogen stream and the concentration of hydrogen in the oxygen stream will be well below the ignition limits. However, over time, purity may tend toward acceptable limits due to the build up of oxides or contaminants on the electrodes. This trend is a very slow I
process detectable by periodic purity testing well before combustible mixtures are reached. The time that it takes depends on materials of the electrodes, and impurities in the water. To monitor cell performance and avoid combustible mix-tures, gas purity shall be periodically or continuously measured. As a second g
precaution against an unsafe condition, the equipment shall be designed to contain l ur an internal explosion.
4.3.3 Air Inleakace The electrolytic cells and their gas collection headers shall be controlled to a pressure above atmospheric.
Since nearly any method of compression will cause a reduction of pressure at the I
inlet of the compression device, the equipment at and between the pressure regulating device (for maintaining the gas generator pressure) and the compressor 4-16 I
I must be designed to avoid air inleakage. This equipment shall be designed to (1) not contain sufficient hydrogen to represent a hazard to plant safety, (2) not have any ignition sources,in the hydrogen flow path, and (3) avoid combustible gas mixtures. Valves in this flow path should have spark-resistant seat and stem I
guides. The design should be capable of containing an internal explosion.
4.3.4 Out Leakage The system must be designed to avoid combustible gas mixtures which could result from unintentional outleakage. Controlled venting to safe locations in the atmosphere is acceptable.
The kindling temperatures of combustible materials decrease with increased concentrations of oxygen. Therefore, oxygen must not be vented in the vicinty of combustible materials that would be at temperatures above the kindling temperature in a pure oxygen concentration.
4.3.5 External Events External events such as seismic, tornado, aircraft crash and flood cannot result in consequences more severe than cited above and need not be considered further.
4.4 LIQUID OXYGEN 4.4.1 Site Characteristics of Liquid Oxygen 4.4.1.1 Overview. Review of the following site characteristics shall be completed by each BWR facility as part of their efforts to locate the liquid oxygen storage system.
I 1.
Locction of supply system in proximity to exposure as addressed in NFPA 50.
2.
Route of liquid oxygen delivery on site.
3.
Location of supply system in proximity to safety related equipment.
4.
Location of hydrogen storage.
4.4.1.2 Specific Considerations.
4.4.1.2.1 Fire protection. The area selected for liquid oxygen system siting shall meet or exceed all requirements for protection of personnel and equipment as addressed in NFPA 50, Bulk Oxygen Systems. The standard identifies the types of 4-17
I exposures under consideration. The number of exposures warrants a plant-specific I
review for proper code compliance. As much separation distance as practical should be provided between the hydrogen and oxygen systems.
4.4.1.2.2 Security. All liquid oxygen supply system installations shall be completely fenced, even when located within the security area. Lighting shall be installed to facilitate night surveillance.
4.4.1.2.3 Route of liquid oxycen delivery on site. Each plant should determine the route to be taken by liquid oxygen delivery trucks through on-and off-site areas. In order to protect the oxygen storage area from any vehicular I
accidents, truck barriers shall be installed around the perimeter of the system installation.
Within the plant security area all deliveries shall be controlled by plant security personnel, per the requirements of 10 CFR 73.55.
I 4.4.1.2.4 Location of storace system to safety-related ecuipment. Each plant shall determine that the location of the liquid oxygen supply system is acceptable considering the hazard described in Section 4.4.2 and 4.4.3.
4.4.2 Liquid Oxygen Storage Vessel Failure Liquid oxygen storage vessels are vulnerable to the same potential causes of I
failure as the liquid hydrogen vessels but the potential consequences of failure are much less severe. The potential threat from a liquid oxygen spill is the contact of oxygen-enriched air with combustible materials or the ingestion of oxygen-enriched air into safety-related air intakes. For the purpose of this report, it is conservatively assumed that total oxygen concentrations above I
30 vol. 5 (21% 02 in air +'9% enriched 0 ) will increase the effective 2
combustibility of ignitible materials in the area.
4.4.3 Liquid Oxygen Vapor Cloud Dispersion The vapor cloud instantaneously formed by a large liquid oxygen spill will have a density of 3.59 relative to air. Such a cloud will experience considerable l
gravity-driven slumping as it disperses and translates with the wind. This g
process has been described by the DEGADIS model developed by Prof. J. A. Havens of
! E the University of Arkansas. His model has been found to agree well with published data on large releases of dense gases conducted by the U.S. Department of Energy, U.S. Coast Guard and others.
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I
I I-The DEGADIS model has been used to determine the height of the vapor cloud as a I
function of distance for various sizes of comercially available liquid oxygen storage tanks. It wa's conservatively assumed that any vessel failure would result in the instantaneous vaporization of the entire tank contents. Figure 4-9 shows the results of this study for the worst-case weather conditions of F stability and a 10-meter per second wind speed. For dense gas dispersion, lower wind speeds I
result in more radial spreading with a lower cloud height and shorter maximum drift distance. Higher wind speeds will transiste even the largest release past safety-related intakes in less than 10 seconds, giving little time for ingestion of enriched air.
I Therefore, liquid oxygen storage vessels shall be located such that safety-related air intakes are within the acceptable region defined by Figure 4-9 or alternative analyses shall be performed to justify the location.
4.5 REFERENCE 4-1 " Air Products Liquid Hydrogen Storage System Hazardous Consequence Analysis."
Revision 1. October 1, 1985.
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200 400 GOO 800 1000 1200 Distance from Liquid Oxygen Storage Tank (ft)
Figure 4-9. Acceptable locations of safety-related air intakes for various sizes of liquid oxygen storage tanks.
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I 4-20 I
I I-I Section 5 VERIFICATION I
The various methods of verifying the effectiveness of HWC (i.e., electrochemical I
potential, constant extension rate tests, etc.) are not within the scope of this document. Appropriate methods of verification should be sele.cted and implemented on a plant specific basis.
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I l-I Section 6 OPERATION, MAINTENANCE, AND TRAINING I
This section gives recomendations to the operating utility for operation, main-tenance, and training in order to meet the design intent of the hydrogen water chemistry (HWC) system.
The operation of a HWC system will require operator and chemistry personnel attention. Because of the radiation increases that result from employing this I
system, an awareness of ALARA principles is required by all plant personnel. This system could also have an effect on the off-gas system and the plant fire protection program.
6.1 OPERATING PROCEDURES Written procedures describing proper valving alignment and sequence for any anti-cipated operation should be provided for each major component and system pro-cess. Check-cff lists should be developed and used for complex or infrequent I
modes of operation. Operating procedures should be considered for the following operations:
1.
Hydrogen addition system startup, normal operation, shutdown and alarm response I
2.
Material (gas or liquid) handling (filling of storage tanks) operations which are consistent with the supplier's recomendations I
3.
Purging of hydrogen and oxygen lines 4.
Operation of on-site gas generation system (if appropriate) 5.
Fire protection or safety measures for hydrogen or oxygen enhanced fires and hydrogen or oxygen spills.
I 6.
Calibration and maintenance procedures as recomended by equipment or gas suppliers 7.
Routine inspection of HWC system equipment 8.
Adjustment of the main steam line radiation monitor setpoints (ifappropriate) 6-1
I 6.1.1 Integration into Existing Plant Oreration Procedures Where appropriate, cperation of the HWC system shall be incorporated into normal I
~
plant procedures such as plant startup and shutdown.
6.1.2 Plant-Soecific Procedures Appropriate procedures shall be developed to provide guidance for plant operators I
when operation of the HWC system necessitates operation of an existing system in a different mode or raises new concerns. Areas which should be considered are:
1.
Operation of the off-gas system 2.
Possible off-gas fires 6.1.3 Radiation Protection Program Operation of a HWC system results in an increase in radiation levels wherever nuclear steam is present. The radiation protection program shall be reviewed and appropriate changes made to compensate for these increased radiation levels.
I s
The following guidelines are established to ensure that radiological exposures to both plant personnel and the general public are consistent with ALARA require-ments. Compliance with these requirements minimizes radiologically significant hazards associated with HWC implementation. The operation of a hydrogen addition I
system may cause a slight reduction in the off-gas delay time due to the increase in the, flow rate of non-condensables resulting from the excess oxygen added. This may slightly increase plant effluents and should be reviewed on a plant-specific basis.
I 6.1.3.1 ALARA Commitment. Permanent hydrogen water chemistry systems and programs will be designed, installed, operated, and maintained in accordance with the provisions of Regulatory Guides 8.8 and 8.10 to assure that occupaticria' radiation exposures and doses to the general public will be "as low as reasonable achievable."
I 6.1.3.2 Initial Radiological Survey. A comprehensive radiological survey should be performed with hydrogen injection to quantify the impact of hydrogen water chemistry on the environs dose rates, both within and outside the plant. This survey should be used to determine if significant radiation changes occur within the plant and at the site boundary. Based upon the magnitude of the change, it I
should be determined if new radiation areas or high radiation areas need to be created. Appropriate posting, access, and monitoring requirements should be 6-2
I-implemented for the affected areas. Plant operating and surveillance procedures I
should be revised, as required, to minimize the time and number of personnel required in radiation areas for operations, maintenance, in-service inspection, etc.
6.1.3.3 Plant Shielding. The radiological survey of subsection 6.1.3.2 should be
,I used to determine the. adequacy of existing plant shielding. In addition, the radiation levels'from sample lines, sample coolers and monitoring equipmt.nt may increase due to HWC and should be checked for adequate shielding. If required, measures for selective upgrading of plant shielding should be implemented to reduce both work area and site boundary dose rates.
6.1.3.4 Maintenance Activities. Hydrogen water chemistry will have minimum impact on occupational exposures resulting from maintenance activities. Plant procedures should incorporate appropriate requirements for access to and monitor-ing of areas where increased dose rates exist with HWC to satisfy ALARA require-I ments. For extended maintenance, plant procedures should include provisions to terminate the hydrogen injection. Due to the short half-life of N-16, radiation levels will return to pre-HWC conditions within minutes of hydrogen shutoff.
6.1.3.5 p)fologicalSurveillancePrograms. Dose rate surveys should be I
conducted and radiation levels should be scnitored periodically to ensure compliance with the radiological limits imposed by 40 CFR Part 190, 10 CFR Part 100, and 10 CFR Part 20. Addition &1 surveys may be required to comply with ALARA require.ments.
I 6.1.3.6 Measurement of N-16 Radiation. The radiological surveillance program should include provisions for the new distribution of N-16 in the main steam.
Selection of app h priate health. physics instrumentation and application of correction factors are required to provide accurate dose measurements. (This correction is required due to the effect of the energenic N-16 gama on I
instrumentation calibrated with less energenic gamma sources.) All plant survey meters should be reviewed and appropriate calibration and correction methods accounted for in plant procedures.
A review of the plant personnel dosimetry program shall be conducted to ensure that the appropriate calibration or correction' factors are used.
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6.1.3.7 Value/ impact Considerations. The following discussion reviews the total dose impact on a plant which implements HWC.
A radiological assessment at Dresden indicates that the total dose increase with HWC is approximately 0.5% on an annual basis (from 1935 to 1945 man-rem / year)
I (Reference 6-1). While this increase is site dependent due to plant layout and shielding configurations, significant variances from the Dresden assessment are not anticipated. Thus, over the life of a plant (assuming a 25-year remaining life), the projected total dose increase with HWC is -250-300 man-rems.
I With HWC Implementation, the potential exists to relax current augmented in-service inspection requirements imposed by NRC Generic Letter 84-11 (Reference 6-2) and elimination of extended plant outages for pipe replacement and/or repair. The value/ impact assessment presented in Appendix E to Reference 6-3 projects a 1161 man-rem (best estimate) savings over the life of the I
plant as a consequence of reduced inspections and repairs with HWC. Typical pipe replacement projects result in a total dose of 1400 to 2000 man-rem. Thus HWC implementation could result in a significant savings in total dose over the life of the plant.
6.1.4 Water Chemistry Control Procedures should be developed to maintain the high reactor water quality I
necessary to obtain the maximum benefit from the HWC system. The EPRI-BWR Owners Group has developed "BWR Water Chemistry Guidelines" which should be used in developing these procedures (Reference 6-4).
I S.1.5 Fuel Surveillance frogram No significant effect of hydrogen injection on fuel performance has been observed, nor is expected. However, since in-reactor experience with hydrogen water I
chemistry is limited, utilities should consider the fuel surveillance programs recommended by their fuel suppliers.
l 6.2 MAINTENANCE A preventative maintenance program should be developed and instituted to ensure l
proper equipment performance to reduce unscheduled repairs. All maintenance l
activities should be carefully planned to reduce interference with station oper-ation, assure industrial safety, and minimize maintenance personnel exposure.
Written procedures should be developed and followed in the performance of l.
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I' maintenance work. They should be written with the objective of protecting plant persor.nel from physical harm, radiation exposure and to reduce hydrogen addition I
system downtime. Radiation exposure should be reduced by shortening the time required in a high radiation field and by reducing its intensity by turning off the HWC system or other means prior to maintenance.
All excess flow check valves used for hydrogen line break protection shall be I
periodically tested to assure they will function properly.
6.3 TRAINING In order for the NWC system to maintain its system integrity and to provide the I
expected benefits from its use, the system must be operated correctly. The most effective means of reducing the potential of operator error is through proper training.
Training should be provided to:
I 1.
Instruct operators on the function, theory and operating characteristics of the system and all its major system components; 2.
Advise operators of the consequences of component malfunctions and misoperation and provide. instruction as to appropriate l
corrective actions to be taken; 3.
Advise operations and maintenance personnel of the potential hazards of gases in the system, and provide instruction as to appropriate procedures for their handling; 4.
Instruct emergency response personnel on appropriate procedures j
for handling fires or personnel injuries involving spills or releases of H2 or 02 liquid and gases.
5.
Instruct plant personnel on the expected radiation changes due to the operation of the HWC system and the appropriate ALARA practices to be taken to minimize dose.
6.
Instruct appropriate personnel on the benefits of HWC.
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Advise maintenance and construction personnel of the routing of hydrogen lines and of the appropriate protectivt actions to be taken when working near these lines.
l su Periodic training should be provided to reinforce informstion described above and to comunicate infctmation regarding any modifications, procedural changes, or incidents.
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l 6.4 IDENTIFICATION In order to aid plant personnel in identifying hydrogen and oxygen lines, these j
lines should be color coded as required by ANSI Z35.1.
6.5 REFERENCES
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6-1 " Environmental Impact of Hydrogen Water Chemistry." EPRI Hydrogen Water Chemistry Workshop, Atlanta, Georgia, December 1984.
6-2 " Inspection of BWR Stainless Steel Piping." NRC Generic Letter 84-11, I
April 19, 1984.
6-3 " Report of the United States Nuclear Regulatory Comission Piping Review Comittee." NUREG-1061, Volume 1, August 1984.
6-4 "BWR Water Chemistry Guidelines. EPRI Report NP-3589-SR-LD, April 1985.
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l-Section 7 SURVEIL *ANCE AND TESTING 7.1 $YSTEM INTEGRITY TESTING In addition to the testing required by the applicable design codes, completed -
procers systems which will contain hydrogen shall be leak tested with a soap soluton prior to initial operaticn of the system. All components and joints shall be so tested in the fabrication shop or after installation, as appro-priate. Appropriate helium leak tests shall be performed on portions of the system following any modifications or maintenance activity which could affect the pressure boundary of the system, 7.2 PREOPERATIONAL AND PERIODIC TESTING Completed systems should be tested to the extent practicable to verify the operability and functional performance of the system. Proper functioning of the following items should be verified:
1.
Trip and alarm functions per Table 2-2 2.
Gas purity, if generated on site 3.
Safety features 4.
System controls and monitors per Table 2-2.
A program should be developed for periodic retesting to verify the operability and the functional performance of the system.
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Section 8 RADIATION MONITORING
8.1 INTRODUCTION
This section reviews the radiological consequence of hydrogen water chemistry (HWC) and presents the basis for increasing the main steam line radiation monitor setpoint to accomodate HWC. It is con:luded that implementation of HWC does not reduce the margin of safety as defined in the basis of the technical specification setpoint.
During normal operation of a BWR, nitrogen-16 is formed from an oxygen-16 (N-P) reaction. N-16 decays with a half-life of 7.1 seconds and emits a high-energy I
gama photon (6.1 MeV). Normally, most of the N-16 combines rapidly with oxygen to form water-soluble, nonvolatile nitrates and nitrites. H:.wsver, because of the lower oxidizing potential present in a hydrogen water chemistry environment, a higher percentage of the N-16 is converted to more volatile species. As a conse-quence, the steam activity during hydrogen addition can increase up. to a factor of I
approximately five. The dose rates in the turbine building, plant environs, and off site also increase; however, the magnitude of the increase at any given location depends upon the contribution of the steam activity to the total dose rate at that location. The specific concerns include:
1.
The dose to members of the general public (40 CFR 190),
2.
The dose to personnel in unrestricted areas (10 CFR 20), and 3.
The maintenance of pers'onnel exposure "as low as reasonably l
achievable" (ALARA).
l 8.2 MAIN STEAM LINE RADIATION MONITORING As noted in the previous section, main steam line radiation levels can increase up to approximately 5-fold with hydrogen water chemistry. The majority of BWRs have a technical specification requirement for the main steam line radiation monitor (MSLRM) setpoint that is less than or equal to three (3) times the normal rated I
full power background. For these plants an adjustmant in the MSLRM setpoint may be required to allow operation with hydrogen injection. For earlier BWRs with 8-1
MSLRM setpoints of seven (7) to ten (10) times normal full power background, a set point change may not be required.
8.2.1 Dual MSLRM Setooint Reco=endation For plants at which credit is taken for an MSLRM-initiated isolation in the control rod drop accident (CRDA), a dual setpoint approach may be utilized. Above 20% rated power the setpoint should be readjusted to 3 times the normal rated full power background with hydrogen addition. Below 20% rated power or the power level required by the FSAR or technical specifications (see Table 2-1), the existing setpoint is maintained and hydrogen should not be injected. If an unanticipated power reduction event occurs such that the reactor power 'is below this power level without the required setpoint change, control rod motion should be suspended until the necessary setpoint adjustment is made. At newer plants, credit is not taken for an MSLRM-initiated isolation after a CRDA, and a dual set point is not needed at these plants.
8.2.2 MSLRM Safety Design Basis The only design basis event for which some plants may take credit for main steam isolation valve (MSIV) closure on main steam line high radiation is the design basis control rod drop accident (CRDA). As documented in Reference 8-1, the CRDA is only of concern below 10% of rated power. Above this power level the rod worths and resultant CRDA peak fuel enthalpies are'not limiting due to core voids I
and faster Doppler feedback. Since the current MSLRM setpoint will not be changed below 20% rated power, the MSLRM sensitivity to fuel failure is not impacted and the FSAR analysis for the CRDA remains valid.
The licensing basis for the CRDA states that the maximum control rod worth is I
established by assuming the worst single inadvertent operator error (Reference 8-2). From References 8-2 and 8-3, the maximum control rod worth above 20% rated power, assuming a single operator error, is <0.8% AK/K. Parametric studies utilizing the conservative GE excursion model (Reference 8-1) indicate that the maximum peak fuel enthalpy for a dropped control rod worth cf 0.8% AK/K I
is less than 120 calories per gram (Reference 8-3).
Consequently, the conservatively calculated peak fuel enthalpy for a CRDA above 20% rated power will l
have significant margin to the fuel cladding failure threshold of 170 calories per gram.
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An increase in the MSLRM s'etpoint will not impact any other FSAR design basis accident or transient analysis since no credit is taken for this isolation signal. Consequently, a technical specification change which adopts the recommended dual setpoint approach will not reduce overall plant safety margins.
I 8.2.3 MSLRM Sensitivity Conceptually, the sensitivity of the MSLRM to fission products is effectively I
reduced by the increase in the setpoint above 20% power. However, it is still functional and capable of initiating a reactor scram. The main function of the instrument is to help maintain offsite releases to within the applicable regula-tory limits. The MSLRM is supplemented by the offgas radiation monitoring system which monitors the gaseous effluent prior to its discharge to the environs. The I
offgas radiation monitor setpoint is established to help ensure that the equivalent stack release limit is not exceeded.
8.2.4 Conclusions From the above discussion, it can be concluded that an increase in the MSLRM setpoint above 20% rated power will not reduce the safety margins as defined by technical specifications or increase the offsite radiological effects as a consequence of design base accidents. Furthermore, since this change to the MSLRM can be justified independent of HWC, this change does not constitute an unreviewed safety concern.
8.3 EQUIPMENT QUALIFICATION I
Outside primary containment the increase in dose rates with HWC is relatively small relative to the integrated dose assumed for equipment qualification (EQ) tests. Furthermore, dose rates inside the drywell near the recirculation piping will decrease because of the increased carryover of H-16 in the steam. Each utility should review the resultant dose increases to ensure that the doses I
assumed in the EQ tests required for electrical equipment per 10CFR Part 50.49 l
remain bounding.
8.4 ENVIRONMENTAL CONSIDERATION
S Implementation of a HWC system is unlikely to significantly increase the amounts or significantly change the types of effluents that may be released off-site.
Although an increase in individual or cumulative occupational radiation exposure may occur, the guidelines provided in Section 6.1.3 of this document will ensure I
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that radiological exposures to both plant personnel and the general public are consistent with ALARA requirements. Since the design objectives and limiting conditions for operation as defind by 10 CFR Part 50, Appendix I, are not impacted, no Appendix I revision is required.
Each plant should examine the environmental effects of a HWC system. However, it is unlikely that environmental impact statements or environmental assessments will be required for HWC systems.
8.5 REFERENCES
8-1 R. C. Stirn et al. " Rod Drop Analysis for Large Boiling Water Reactors."
General Electric Company, March 1972 (NE00-10527).
8-2 R. C. Stirn et al. " Rod Drop Accident Analysis for Large Boiling Water Reactors Addendum No. 2 Exposed Cores." General Electric Company, Janua'y 1973 (NED0-10527 Supplement 2).
8-3 R. C. Stirn et al. " Rod Drop Accident analysis for Large Boiling Water Reactors Addendum No. 1 Multiple Enrichment Cores With Axial Gadolinium."
General Electric Company, July 1972 (NEDO-10527 Supplement 1).
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Section 9 QUALITY ASSURANCE Although the HWC system is non-nuclear safety related, the design, procurement, fabrication and construction activities shall conform to the quality assurance provisions of the codes and standards specified herein. In addition, or where not covered by the referenced codes and standards, the following quality assurance features shall be established.
9.1 SYSTEM DESIGNER AND PROCURER 1.
Design and Procurement Document Control - Design and procurement documents shall be independently verified for conformance to the requirements of this document by I
individual (s) within the design organization who are not the originators of the design and procurement documents. Changes to design and procurement documents shall be verified or
. controlled to maintain conformance to this document.
2.
Control of Purchased Material. Equipment and Services -
Measures shall be established to ensure that suppliers of I.
material, equipment and construction services are capable of supplying these items to the quality specified in the procure-ment documents. This may be done by an evaluation or a survey of the suppliers' products and facilities.
3.
Handling, Storage. nd Shipping - Instructions shall be provided in procurement documents to control the handling, i
storage, shipping and preservation of material and equipment to prevent damage, deterioration, and reduction of cleanliness.
9.2 CONTROL OF HYDROGEN STORAGE AND/OR GENERATION EQUIPMENT SUPPLIERS In addition to the requirements in Section 9.1, the system designer should audit the design and manufacturing documents of the equipment supplier to assure conformance to the procurement documents. The system designer shall specify specific factory tests to be performed which will assure operability of the I
supplier's equipinent. The system designer or his representative should be present for the factory tests.
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I 9.3 SYSTEM CONSTRUCTOR 1.
Inspection -- In addition to code requirements, a program for inspection of activities affecting quality shall be established I
and executed by, or for, the organization performing the activity to verify conformance with the documented instruc-tions, procedures, and drawings for accomplishing the i
activity. This shall include the visual inspection of com-I ponents prior to installation for conformance with procurement documents and visual itspection of items and systems following installation, cleaning, and passivation (where applied).
I 2.
Inspection, Test and Operating Status -- Measures shall be established to provide for the identification of items which have satisfactorily passed required inspections and tests.
3.
Identification and Corrective Action for Items for Nonconformance -- Measures shall be established to identify items of nonconformance with regard to the requirements of the I
procurement documents or applicable codes and standards and to identify the remedial action taken to correct such items.
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I Appendix A CODES, STANDARDS, AND REGULATIONS APPLICABLE TO PERMANENT HYDROGEN WATER CHEMISTRY INSTALLATIONS I
This Appendix lists codes, standards, and regulations which may be applicable to specific permanent hydrogen water chemistry installations.
10 CFR 20 Standards for Protection Against Radiation 10 CFR 50.48 Fire Protection' 10 CFR 50.49 Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants 10 CFR 50 Appendix A General Design Criteria for Nuclear Power Plants, General Design Criteria 3, 54, 55, 56, or 57 10 CFR 73.55 Requirements for Physical
.ection of Licensed Activities in Nuclear Power Reactors Against Radiological Sabotage 10 CFR 100 Reactor Site Criteria 29 CFR 1910 Labor - OSHA Healti Standards 29 CFR 1910.103 Hydrogen 29 CFR 1910.104 0xygen 40 CFR 190 Protection'of Environment - Environmental Radiation Protection Standards for Nuclear Power Operations ASME Boiler and Pressure Vessel Code Section VIII, Pressure Vessels ASME Boiler and Pressure Vessel Code Section IV Heating Boilers I-ASME Boiler and Pressure Vessel Code,Section IX, Welding and Brazing Qualifications ANSI B31.1 American National. Standards Institute, Power Piping ANSI B31.3 American National Standards Institute, Chemical Plant and Petroleum Refinery Piping ANSI Z35.1 Accident Prevention Signs. Specification for ANSI / ASTM G63 Evaluating Nonmetallic Materials for Oxygen Service API Standard 620 Design and Construction of Large Welded, Low-Pressure Storage Tanks, America Petroleum Institute Recommended Rules for I
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I AWS 01.1 Structural Welding Code NFPA50 Bulk 0xygen Systems NFPA SOA Gaseous Hydrogen Systems at Consumer Sites NFPA 508 Liquified Hydrogen Systems at Consumer Sites NFPA 70 National Electrical Code Compressed Gas Association G-4, Oxygen Compressed Gas Associated G-4.1, Cleaning Equipment for Oxygen Service Compressed Gas Association G-4.4, Industrial Practices for Gaseous Oxygen Transmission and Distribution Piping Systems Conpressed Gas Association G-5, Hydrogen Co.apressed Gas Association G S.3, Comodity Specification for Hydrogen Compressed Gas Association P-12, Safe Handling of Cryogenic Liquids U.S. Army Technical Manual TMS-1300 U.S. Department of Transportation Specification 3A, 3AA, 3AX, 3AAX I
U.S. Nuclear Regulatory Comission Regulatory Guide 1.76, " Design Basis Tornado for Nuclear Power Plants" U.S. Nuclear Regulatory Comission Regulatory Guide 8.8, "Information Relevant to I
Ensuring that Occupational Radiation Exposures at Nuclear Power Stations Will Be As Low As Reasonably Achievable (ALARA)"
I U.S. Nuclear Regulatory Ccmission Regulatory Guide 8.10. " Operating Philosophy for Maintaining Occupational Radiation Exposures As Low As Reasonably Achievable" U.S. Nuclear Regulatory Comission Franch Technical Position CMEB 9.5-1,
" Guidelines for Fire Protection for Nuclear Power Plants" I
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