ML20238D890

Permanent Hydrogen Water Chemistry Safety Analysis

ML20238D890
Person / Time
Site:	Peach Bottom
Issue date:	01/31/1987
From:	Jeffrey Jacobson, Loy H, Schock E GENERAL ELECTRIC CO.
To:
Shared Package
ML20237L734	List: ML20237L732 ML20238D865 ML20238D885 ML20238D890 ML20266J724 ML20266J726
References
DRF-A-23938, DRF-A00-023938, EQDE-01-0187, EQDE-1-187, NUDOCS 8709110473
Download: ML20238D890 (23)

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Philadelphia Electric Company Peach Botte- Atomic- j Pcwer Station, Unit 2/3 I

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Moa 15&~1 M' Permanent Hydrogen Water.

Chemistry Safety Analysis January 1987 Prepared by W #

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H.L.LoybrincipalEngineer Equipment Design Engineering Prepared by 2 Y gM P 6 hcA, E. L. Schock Licensing Services Approved by . M/ //

J.[acobson,' Manager Equipment Design Engineering - 4 Approved by h [, .'(/ / M .

. J. Robare, Manager . .g.,2"'

Licensing Services a,! c i 8709110473 B7002427 l DR ADOCK O GENERAL ELECTRIC COMPANY .

NUCLEAR FUELS AND ENGINEERING SERVICES DEPARTMENT SAN' JOSE, CALIFORNIA 95125 -

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2870000452

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• Janusry 1987 DISCLAIMER OF RESPONSIBILITY This document was prepared by the General Electric Company.- Neither the General Electric Company nor any of the contributors to this documents A. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this document, or that the use of any information disclosed in this document may not infringe privately owned rights; or B. Assumes any responsibility for liability or damage of any kind which may result from the use of any information disclosed in this document.

The information contained in this report is believed by General Electric to be an accurate and true representation of the facts known, obtained or ~

, .. provided t'o General; Elect'ric at.the time this rep' ort was p'repded.'

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.. .+,'. PO:ch Botton Unit 2/3 l January 1987 287000045P l 1. INTRODUCTION i .

! This report provides a review of the operational impact of. permanent L

m Bydrogen~ Water Chemistry (HWC) at the Peach Botton Atomic Power' Station, Unit 2/3.

.The review concludes that the concerns addressed herein, during normal HWC operations, will not represent an unsafe condition at PB-2/3.*

2. NORMAL OPERATION POTENTIAL HAZARD ANALYSIS The plant systems affected by' normal operation of the NWC system, are evaluated below to show that the impact is satisfactory with regard to plant or personnel safety.

~2.11 1ADWASTE DRAIN '8 UMPS

The introduction of hydrogen into the feedvater system increases the amount of hydrogen in the feedwater, reactor water, and nuclear steam, which ultimately comprise a significant portion of the water reaching the radwaste sumps. These increases were measured during the HWC pre-implementation test at' Peach Bottom 3. Feedwater hydrogen concentration is increased from essentially zero to a maximum of 1.28 ppe. Reactor recirculation water hydrogen concentration is increased from 10 ppb to a maximum of 210 ppb. Main steam hydrogen concentration increased from 1.90 ppa to 2.01 ppa. Hydrogen in the main condenser condensate remained at essentially zero. t i

• This report addresses only normal, steady state operating conditions occurring during hydrogen water chemistry. Offgas composition during abnormal operating conditions and transients should be addressed by PECO.

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.i.'* Pach Botton Unit 2/3 January 1987 The hydrogen concentration increase in the sump water sources.results in increased hydrogen concentrations in the sump air spaces when the dissolved hydrogen comes out of solution. The potential for forming explosive mixtures-of hydrogen and air in the various sump air spaces has been evaluated and'is

. discussed below. The sump compositions evaluated are based upon data contained in the PB 2/3 FSAR,. Figure 9.2.lb', Radweste Process Diagram.

2.1.1 Floor Drain Sumps Hydrogen water chemistry would have essentially no effect on the hydrogen concentration.in the floor drain sumps because this water does not receive pressuris'ed main steam, reactor water or feedwater.

2.1.2. Radwaste Equipment Drain Sump Hydrogen watei chemistry should not affect the hydrogen concentration in .

the radwaste equipment drain sump because this sump does not receive pressurized main steam, reactor water or feedwater.

2.1.3 Turbine Building Equipment Drain Sumps Water in these sumps originate from the condenser train, feedwater train, and offgas system drains. Not considering the offgas drain, which should contain essentially no_ hydrogen, the average sump water hydrogen composition is 0.61 ppe. This results in a maximum of 1.9% hydrogen in the sump air space, which is well below the lower combustible limit of 41.

2.1.4.' Reactor Building Equipment Drain Sumps Water in these sumps originate from reactor water and feedwater. The average sump water hydrogen composition is 0.75 ppe, which results in a

. maximum of 2.31% hydrogen in the sump air space. This is well below the lower <

l combustible limit of 4%.

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• J:nusry 1987 j 2.1.5 Drywell Equipment Drain Surp l

Water in these sumps is.primarily reactor recirculation water with some j feedwater and condensed steam. The average sump water hydrogen composition is f 0.48 ppe, which results in a maximum of 1.48% hydrogen in the gas space of the ,

4' sumps. Since the drywell is inerted and the dissolved oxygen level in the water is low, combustible limits do not apply to thece sumps. ,

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j 2.2 TORUS AIRSPACE COMBUSTIBILITY AFTER SRV BLOWDOWN Hydrogen water chemistry slightly increases the hydrogen addition rates to the torus via the SRVs when compared to non-hydrogen water chemistry conditions. Oxygen blowdown is decreased, and the inerted containment reduces the possibility of forming a combustible mixture. The following table j 1

1 compares the rate of change of hydrogen and oxygen in the torus assuming that all steam at 100% power is released-into the tbrus. -

Rate of Change (%/ Minute)

Without Hydrogen With Hydrogen Water Chemistry Water Chemistry Cas Hydrogen 0.059 0.063 Oxygen 0.034 0.015 Risk of reaching a combustible mixture in an inerted torus is reduced during hydrogen water chemistry due to a decrease in the available oxygen.

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2.2.1 Effect on Steam Leakage Hydrogen Concentration The PB-2/3 HWC pre-implementation tests (Reference 1) have shown that the concentration of hydrogen in the reactor steam was only 6% higher at the hydrogen injection rate required for IGSCC mitigation, as compared to hydrogen concentrations observed under normal water chemistry conditions. Thus, HWC introduces no new concerns about generalized steam leaks and attendant l

i flammability thresholds within steam driven systems.

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3. IMPACT ON PLANT SYSTEMS AND COMPONENTS The hydrogen water chemistry system interfaces diroccly with the feedwater system, the condensate system, and the offgas system. It interfaces indirectly with the reactor recirculation system, the reactor vessel and internals,-the main steam lines, the turbine, the main condenser, and equipment drain sumps.

Where hydrogen water chemistry operation impacts another plant system or could effect its. operation, it was evaluated. The results of these evaluations are given below.- -

. . 3.1 0FFCAS SYSTEM Hydrogen flow into the offgas system during normal hydrogen water. chemistry system operation will increase about 6%. Stoichiometric oxygen is added to recombine with the hydrogen. The net effect is an increased heat input into ihe recombined offgas'. Yheoffgassystemisconservative1'ydesignedfor128 scfm hydrogen (FSAR Table 9.4.1). Based on the data of Reference 1, a maximum flow of 80.3 scfm is expected. The offgas system remains conservatively designed to handle the expected increased hydrogen and oxygen flow to the recombiner.*

3.2 MAIN CONDENSER The noncondensible gas composition in the main condenser will shift from an essentially stoichiometric mixture of hydrogen and oxygen to a hydrogen 1 rich mixture during operation with HWC. Based on the PB-2/3 pre-implementation j test date in Reference 1,'and 30 cubic feet (at 60*F) air inleakage into the main condenser, the noncondensible composition in the main condenser at ]

normal HWC operating point (reactor power at 100% and Feedwater hydrogen concentra- tion of 1.28 ppm) is as follows:

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• CE continues to be concerned about the operation of PB-2/3 with mechanical l compressors and pressure much above atmospheric in the offgas train. This subject has not been considered in this report but certainly should be l

addressed by Philadelphia Electric if they intend to operate in that mode. {

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Noncon'densible Gas Flow Rate (SCFM) at Main Condenser Air'Eiector Exit Without Hydrogen . ;With Hydrogen Cas Water' Chemistry _. Water Chemistry.

Hydrogen injected 0.0 50.9 E' Hydrogen - radiolytic* 75.6' '29.4 TOTAL Hydrogen, -75.6 80.3-Oxygen inleakage 5.7 5.7 0xygen - radiolytic* 43.8 - 20.0 TOTAL 0xygen 49.5 25.7 Nitrogen inlaskage 22.7 22.7 TOTAL 147.8 128.7

• The radiolytic hydrogen / oxygen ratio'is normally expected to be the stoichiometric ratio of 2:1. The deviation from that ratio is believe'd to be the accuracy with which it-was possible to sample and analyze hydrogen and oxygen concentrations in the nuclear steam with the techniques available.

during the P,B-3 pre, implementation testing.

The net affect of HWC is to reduce the total noncondensible flow by 13%

and to reduce the oxygen. composition from 33% to 20%. Neither of these condi-

.tions pose any operability or safety concerns for the equipment. i 3.3 CONDENSATE AND FEEDWATER SYSTEMS' Based on'the PB-2/3 pre-implementation test data (Reference 1), the feed-water oxygen concentrations were reduced substantially below 20 ppb. Carbon steel exposed to water below 20 ppb oxygen introduces a region where the onset of substantially increased carbon steel corrosion may be observed. The hydro-'

gen water chemistry system has the capability of injecting oxygen into the suction of the condensate pumps to maintain the condensate above 20 ppb oxy- 3 gen, and protect the feedwater and condensate systems from this phenomena of .

i increased corrosion; therefore, these systems will not be affected by HWC j operation. )

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3.4 REACTOR COOLANT' RECIRCULATION SYSTEM f

Based upon data from'the PB-3 pre-implementation testing,*the oxygen-concentration in the reattor recirculation water dropped from'196 ppb oxygen without HWC, to.14 ppb oxygen when 1.28 ppe hydrogen was injected into the

feed- water. This low oxygen concentration in the recirculation water results )

in ICSCC protection for the recirculation piping, which is the purpose of HWC. The pre-implementation test (Reference 1), demonstrated that the  ;

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. recirculation system operation will not be affected by HWC operation. j i

3.5 REACTOR VESSEL AND VESSEL INTERNALS  !

I It is believed that HWC will offer improved protection, for the reactor vessel and vessel internals, from irradiation assisted stress corrosion crack-

.ing; but the degree of protection has not been quantified. General Electric, '

.'in cooperation wit '

'E r EPRI and industry participants, is invoIved in two separ-ste programs to further evaluate HWC protection for the reactor vessel and vessel internals.

3.6 MAIN STEAM LINES AND TURBINE Based upon the PB-3 pre-implementation test (Peference 1), with opera-tion of HWC at the proper feedwater hydrogen injection rate to mitigate ICSCC at full power, the steam oxygen concentration is reduced from 17.5 ppm to 8.0 ppe . - Hydrogen concentration in the steam is increased slightly from 1.9 ppm to 2.02 ppe. The main steam lines and turbine will not be adversely affected-by HWC operation. The radiation levels due to the main steam is expected to increase. This is discussed below.

4. RADIOLOGICAL CONSIDERATIONS 4.1 ALARA CONSIDERATIONS One of the consequences of adding hydrogen to the feedwater is, when at reactor power, the main steam line nitrogen-16 (N-16) activity increases. In l 6

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normal BWR water chemistry conditions, the N-16 reacts with the dissolved

j. oxygen to form a nitrate (NO3 ~), which is soluble in water. Under hydrogen water chemistry conditions the N-16 combines with the hydrogen to l

form ammonia (NH 3 ). Since ammonia is more volatile, more of it escapes with the steam, causing the steam lines and turbine to emit more gamma radiation.

Because the N-16 has a short half-life (7.1 sec), the radiation level drops to normal within a minute after the hydrogen. addition is terminated.

Extensive plant interior and exterior radiation surveys were conducted as a part of the PB-2/3 HWC pre-implementation test (Reference 1). The increased dose rates encountered were in the range expected and are controlled by plant operating, procedures.

l Discussion

• *- ' Based upon the PB-2/3' pre-implementati,on test at'100% power," a hydrogen l injection rate of 1.28 ppe in the feedwater, the Main Steam Line Radiation Monitor (MSLRM) reading increased by a factor of approximately three over the reading at normal BWR water chemistry conditions. Similar or somewhat higher ratios were realized near the turbine, near the condenser bays, and near the moisture separators.

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A radiological assessment is being prepared to determine if additional shielding is required to meet long term ALARA guidelines.

d It should be noted that HWC radiation levels need not affect maintenance activities in the turbine area. This is due to the radiation levels dropping to normal very rapidly upon hydrogen addition interruption or reduction to a low hydrogen injection rate. Laboratcry results indicate that the materials protective effects of HWC remain effective for about eight hours after 1 hydrogen interruption. In addition, the environmental dose rate has shown a distance versus dose effect with essentially no effect at 2430 feet.

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5. FUELS IMPACT i

L Permanent EWC at PB-2/3 is not expected to adversely impact. fuel performance. This is demonstrated by current EWC operating experience and examinations of fuel bundle components at Dresden 2, which has been operating with permanent EWC for 36 months with no apparent adverse effects on fuel performance. Examinations of fuel bundle components at poolside and in hot calls were performed after the first cycle (18 months) of operation in the HWC

. environment. These examinations revealed that the corrosion and hydriding performance of fuel components were not influenced by HWC. These examinations cleo determined that crud deposits were within the normal range, based on samples obtained at similar BWR's operating without EWC.

Since PB-2/3 will be the first crud induced localized corrosion (CILC) type plant operating under EWC conditions, fuel surveillance will be performed .

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6. REFERENCES I

1. Peach Bottom III Hydrogen Water Chemistry Mini Test Final Report, J. Law, et. al., February 1985 8

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SCD Contract No. 39775 Philadelphia Electric Company Hydrogen Water Chemistry BWROG CUIDELINES REVIEW 6/30/87 )

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SUMMARY

f A permanent Hydrogen Water Chemistry (HWC)' System is currently being installed

! at Philadelphia Electric Company's Peach Bottom Atomic Power Station, Units 2 and 3. A review of -the system design 'has been performed to determine I conformance to the requirements specified in " Guidelines For Permanent BWR Hydrogen Water Chemistry Installation" 1987 revision prepared by the BWR l Owner's Group for IGSCC Research. This report presents the results of that review. 'The HWC system design is essentially in conformance with the BWROG Guidelines. The report addresse' only those items which require explanation or clarification. No direct exceptions were taken. Paragraph numbers refer to the applicable section of the BWROG Guidelines.

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4 SECTION 1 - INTRODUCTION No Clarifications or exceptions.

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SECTION 2 - GENERAL SYSTEM DESCRIPTION

~ Para 2.3.1.1 - Injection Point Considerations Hydrogen is injected at a local high point in the feed pump suction 'line. The potential for gas pocketing has been evaluated and will not be a problem.

Para 2.3.1.2 - Codes & Standards (1) 29 CFR 1910.103 is applicable to gas supplier's scope of work.

(2) Design' meets codes and standards specifically referenced and standards in Appendix A that are applicable. '

Para 2.3.1.3 - System Desian considerations (1) All below-ground piping is either stainless steel or copper. Cathodic protection, coating or wrapping is not required. Underground piping does not require grounding, and, since it is welded or brazed, electrical continuity is maintained.

(2) In the event of a line break, hydrogen flow is isolated ,

by excess flow check valves, low pressure signal or high hydrogen flow signal. Excess flow protection is provided for leaks greater than 90 SCFM downstream of the main control station or 200 SCFM between the hydrogen supply facility and the main control station. Hydrogen monitors will automatically isolate hydrogen flow if hydrogen concentration exceeds 2% in the valve station shrouds. Heat detectors on the shrouds will isolate flow in the event of hydrogen ignition inside the shrouds. All of the above features are independent of area ventilation. However, very small leaks (<90 SCFM) which occur outside the shrouds will not be detected and the hydrogen leak detection evaluation took credit for ,

area ventilation rates to maintain hydrogen concentrations below flammable limits.

(3) Hydrogen monitors are located at use points that constitute potential leaks (valve and instruments).

High point area monitors are not used because they would not be ef fective for detection of small leaks considering the large air volume in the turbine Duilding and the HVAC air changeover rates. For larger leaks

( 90 SCFM) the HWC system is automatically shut dowa.

(4) The ef fect of increased hydrogen concentrations in feedwater, reactor, steam lines, main condenser and off-gas has been addressed by PECo.

4 Pa ra 2.3.2.1 -

Oxygen is injected into off-gas system upstream of  ;

recombiner. Excess oxygen will be maintained below 45%.  !

Para 2.3.2.2 - Codes and Standards (1) 29 CFR 1910.104 applies to gas supplier's piping, not distribution piping.

(2) Oxygen system is in compliance with CGA G4.4 with following clarifications:

(a) 0xygen velocities are not defined in CGA G4.4 for pressures below 200 PSIG. Maximum velocity at 200 PSIG is 200 ft/sec.

(b) Maximum velocity for partial suppression is 70 ft/sec, which is well below acceptable value for carbon steel portions of system. This will require reevaluation for full suppression operation since maximum velocity increases to 250 ft/sec.

(c) Underground piping is brazed. This satisfies requirement for all-welded piping.

(d) Cathodic protection is not required for underground copper piping.

(e) Manual isolation valves in carbon steel portion of the system have components which are not copper-based alloy material. These valves normally "emain full open and are not intended to be used for i throttling. Therefore, they are not considered to be potential ignition points.

(3) Only non-metallic materials used are teflon and EPDM.

EPDM was evaluated using ASTM G63 with result that ignition probability is remote and effect of ignition is

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negligible due to small mass. l i

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'(4) ANSI 235.1' specifies format for warning signs.

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format was used for signs at~ hydrogen and oxygen storage facilities and for signs above underground piping.

.However, SCD referenced OSHA 1910.145 since this is-standard used for commercially available signs. Pipe-

' markers were specified by PECO.

I 2.4' Instrumentation and Control

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!' Table 2-1 Peach Bottom does not have a separate recombiner train trip.

l In :the event of an of f-gas train trip the HWC system will E trip on high oxygen level so there is no need for a redundant of f-ga s ' trip.

~ Table 2-2 All instrumentation required for distribution and injection

.has been provided. Instrumentation at the storage facility

- is within APCI scope of. Work.

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SECTION 3 - SUPPLY FACILITIES SCD did not review APCI design for conformance to BWROG guidelines.

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SECTION 4 - SAFETY CONSIDERATIONS Para 4.1.1.2.2 PECO is providing' lighting to facilitate night surveillance as required.

Pa ra 4.1.1.2.3 . Truck barriers are provided at locations around perimeter of hydrogen storage facility where truck approach from the road is possible.

Para 4.1.2 & 4.2 For a complete discussion of conformance to these requirements, refer to Safety Evaluation / Analysis supporting Hydrogen Water Chemistry for PBAPS Units 2 & 3.

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I-SECTION 5 - VERIFICATION I.

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.This is not within 500 scope of work.

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4 SECTION 6 - OPERATION. MAINTENANCE. TRAINING l

Para 6.1 -

Written operating procedures including check-off lists have been prepared for all modes of operation for the distribution / injection system. APCI will prepare procedures for the storage facilities.

Para 6.1.1 - The operating goals of the HWC system are independent of l normal plant start-up and operating requirements. -The HWC '

system will automatically shut down whenever the plant shuts down.

6.2 Maintenance (1) Preventative maintenance is handled by the PBAPS maintenance personnel. The HWC system will be incorporated into the overall plant maintenance 3 program. An inspection procedure has been prepared '

which addresses the following activities:

Hydrogen System Walkdown for leak detection using a portable hydrogen detector; Oxygen System Walkdown for leak detection using visual and audio inspection:

Inspection of hydrogen detectors at shrouds.

(2) Excess flow check valves will be tested every 5 years per manufacturer's recommendation.

(3) Operator training will be addressed by PECO plant staff.

(4) Station firefighters are trained to combat fires associated with flammable compressible gases / liquids and oxidizers. The station fire coordinator will revise the plant hazards maps to indicate presence of hydrogen and oxygen.

6.4 Identification There is no requirement for color coding of piping in ANSI Z 35.1. This must be a misprint. Oxygen and Hydrogen piping is identified using signs outside and pipe markers inside.

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SECTION 7 - INSPECTION AND TESTING 7.1 Systems Intearity Testina (1) Hydrogen System will be leak tested with helium using a soap solution (portable helium detector is optional).

1 (2) Maintenance Procedure does address leak testing with i helium after repair operations, i l 7.2 Preoperational and Periodic Testina (1) Modification Acceptance Tests address all applicable requirements.

(2) Operability and Functional Performance can be verified '

by periodically rerunning MAT's.

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t SECTION 8 - RADIATION MONITORING SCD did not review Radiation Monitoring Requirements.

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SECTION 9 - OVALITY ASSURANCE y

-9.1 System Assianer and Processor (1) Independent review has been performdd by PECO.

(2) All procurement was by PECO and all suppliers were.on PECO qualified suppliers list. N (3) ' Specifications did provide general instructions for storage, preservation and cleanliness.

9.2 Control of Hydroaen storace EauiDment SuDDliers (1) APCI is system designer of Storage System and these functions should be part of their scope.

9.3 System Constructor (1) These activities are performed by PECo site construction personnel in accordance with existing QA/QC program. ,

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