ML20134H166

Equipment Survivability Enhancement

ML20134H166
Person / Time
Site:	River Bend
Issue date:	08/31/1985
From:	GULF STATES UTILITIES CO.
To:
Shared Package
ML20134H157	List: ML20134H166 RBG-21884, Forwards Equipment Survivability Enhancement. Hydrogen Control Owners Group quarter-scale Testing Performed 17 Scoping Tests Demonstrating That Hydrogen Burn Phenomena Modeled by CLASIX-3 Computer Does Not Occur
References
NUDOCS 8508280303
Download: ML20134H166 (24)

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Attachnent 1 EQUIINENP SURVIVABILITY DEANCENENT August, 1985 Gulf States Utilities River Bend Station - Unit 1 t

I 8508290303 850816 PDR ADOCK 05000458 A PDR

Survivability Enhancenent Report Table of Contents 1.0 Introduction 1.1 Purpose 1.2 Acceptance Criteria 2.0 Rosenount RW Ievel Transnitters 2.1 Incal Installation Details 2.2 Insulation 2.3 W ermal Shields 2.4 Relocation 3.0 Hyi @ i Igniters 3.1 Iocal Installation Details 3.2 Insulation

~3.3 %ermal shields 3.4 Relocation 4.0 Wetwell Cables 4.1 Iocal Installation Details 4.2 Analysis Results 5.0 Conclusion

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e 1.0 Introduction 1.1 Purpose

'Ihe purpose of this report is to describe and provide preliminary evaluations of the effectiveness of various techniques to enhance the survivability of essential equipnent.

Enhancements considered include the application of external insulation, the use of thermal radiation shields and the physical relocation of equipnent or sensitive canponents.

Survivability enhancenents are being considered in order to demonstrate that essential equipnent located in the intermediate volume can survive exposure to a significant nurrber of serial burns predicted to occur in the RBS wetwell by the CLASIX-3 analysis previously subnitted (Ref. 1) . It is recognized that the thermal envirornnent predicted for the wetwell is more severe than what would be expected to occur in the intennediate volane. If burning were to occur in the in6Miate volume, the burns would be less severe, fewer in number and less frequent that the wetwell burns predicted by CLASIX-3. Evaluating the survivability of equignent located in the intermediate volume using the wetwell thermal profiles is very conservative. Therefore, if the equipment can be shown to survive a significant number of these serial wetwell burns, it can be reasonably assumed to survive the degraded core accident.

o Equipnent located in the wetwell volume, hydrogen igniters and their power cables, must be shown to survive the entire wetwell thermal enviroment. The previously subnitted equipnent survivability report (Ref. 2) did not denonstrate survivability of the hydrogen igniters. Various physical modifications which would enhance the hydrogen igniter survivability are evaluated here.

1.2 Criteria The goal of this report is to evaluate the effectiveness of various survivability enhancanent schemes in order to determine the most appropriate methods of ensuring equipnent survivability.

A series of criteria have been developed in order to evaluate various options. Acceptable enhancanent schanes must meet the following:

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1. There should be minimal effect on existing equipnent

, qualification.

2. *he enhancanent must be physically feasible and not interfere with normal operation and maintenance.

3. All physical modifications, if necessary, must be empleted before startup following the first refueling outage.

4. Technically acceptable options should be cmpared on a cost basis.

2.0 Rosenount Transmitters 2.1 Iocal Installation Details Incal installation details have been examined for the Rosemount RW level transmitters. 'Ihe transmitters are mounted in two horizontal rows on open racks. The racks are mounted on 1 1/4" thick solid steel pool swell shields welded directly to the HCU floor sugort steel (el. 114'0"). The pool swell shields provide direct thermal radiation shielding frm the wetwell volume. The transmitters are mounted such that the sensing module is toward the rear of the panel and the electronic housing is toward the front but within the confines of the open racks. The distance of the various racks frm other equignent and walls varies and, therefore, no credit is taken for local shielding by equignent and walls.

2.2 Insulation

Consideration has been given to the addition of insulation on individual Rossount transmitters. An insulation system consisti:q of a one inch thick layer of SILTEMP #CH188 insulation fitted over the entire electronic housing, surrounded by a sixteenth inch thickness of stainless steel, has been analyzed. The results indicate that with this insulation syst s the Rosm ount transmitters are capable of withstanding 23 serial wetwell burns. 'Ihe use of a second insulation syst s consisting of a layer of KA0HOOL insulation between two layers of SILTEMP is being considered. 'Ihe heat conduction properties of this systs indicate that this systs would be more effective in protecting the equipnent.

Evaluation of this insulation scheme indicates that there may be sme impact upon the existing qualification of the units.-

Since these transmitters are supplied by GE, the effect on the seismic and IE qualifications would require GE review and approval. However, at this time the effects appear to be negligible, as the proposed insulation is lightweight and the transmitters generate very little heat with tmperature inside the electronics housing typically only 5 - 10 F above ambient.

Conceptual design indicates that the concept of insulating individual transmitters is feasible and could be implemented in 1

an acceptable timeframe and at a reasonable cost. In addition, the insulating materials are readily available 't the site and can be fabricated into easily re ovable sections to facilitate periodic tran mitter calibration.

2.3 %ermal Shields Various m%i.s of providing thermal radiation shields have been considered. %e simplest concept consists of the application of thin sheet metal shields enclosing all four sides of the instrunent racks. W ese sheet metal shields would provide for a reduction of the incident thermal radiation by a factor of approximately two. However, the shields would be responsive.to the tarperature due to convective heat transfer and would lose their effectiveness as the shield tarperature approaches the gas tarperature.

A second unWi. of thermal shielding, using a t>mally thick shield, consisting of a layer of two inch thick KAOWOOL insulation encapsulated in SILTDP fabric has been considered.

Wis ' shield would be mounted on the four sides of the instrunent rack to protect all exposed sides of the Rosemount transnitters. Open areas would be provided above and below the shields to allow natural air circulation around the instrunents.

An evaluation of this shielding scheme has shown that the instruments could survive at least 19 serial wetwell burns.

%e analysis of this shielding schane was stopped at 13,250 seconds'since this was sufficient to show the viability of this enhanosnent method. We to w ature at this point was 325 F R

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which is well below the equipnent qualification tenperature.

'Iherefore, functionally this schane is effective. Imaving space for natural circulation aronnd the transmitters would not affect their qualification for normal and IOCA service. 'Ihe shield would be designed to be removable to allow for maintenance activities. No significant problems are foreseen with respect to the design, construction, installation and cost of this option. 'Iherefore, preliminary analysis indicates that this thermally thick shield m a.q d. is an acceptable method to achieve survivability for the Rosenount transmitters.

2.4 Relocation Relocation of the Rosemount transmitters would require extensive rerouting of cables and tubing. In addition to the expense and schedule inpact which could be prohibitive, the transmitter function is very sensitive to location parameters such as elevation and instrument line length. '1herefore, this option is to be unfeasible for the reactor level transmitters.

3.0 Wetwell Hydrogen Igniters 3.1 Iocal Installation Details

'No methods are utilized for mounting the igniters to the structures in the wetwell region. Six igniters are bolted to

The the webs of the structural beams supporting the HCU floor.

rmaining six wetwell igniters are bolted directly to the cutside of the drywell wall.

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l beams are provided significant The igniters attached to the shielding by the beams and by a pool swell shield plate (5/8" x of the beam flange. Those 29" x 13") welded to the bottcm mounted directly to the drywell wall have a pool swell shield located below them (within 2 feet of the igniter) which provides scme thermal shielding. The thermal model used in this evaluation is of a typical igniter located on the drywell wall. 'Ihe igniters located on the beams Imve not been evaluated in detail.

3.2 Insulation would Close wrap insulation of the hydrogen igniters potentially invalidate the hydrogen igniter environm ntal qualification. This effect is primarily due to the large internal heat generation frcm the internal transformer.

Therefore, no further consideration has been given to this option at this time.

3.3 %ermal Shielda A thermal shield concept has been evaluated for the hydrogen  ;

igniters. mis concept consists of a thermal shield consisting i i

l of one inch thickness of KAOWOOL encapsulated in SILTEMP fabric l

l insulation. A layer of stainless steel would be added to the i

i outside surface -for support. %ese thermal shields would be mounted vertically on both sides of the igniter, above the igniter, and beneath the igniter above the pool swell shield.

l l We thermal shields would be placed as close as possible to the igniter and the top surface of the igniter. The thermal response analysis using this protection concept indicated that the thermal limiting ccanponent, the ignition transformer, would reach a terrperature of 345 F after 38 wetwell burns. Further ,

refinement of the protection concept and a better estimation of the qualification tenperature should demonstrate that this concept will provide a sufficient protection for the entire series of wetwell burra.

3.4 Relocation l

Relocation or replacement of the wetwell igniter transformers (the critical ccmponent with respect to thermal survivability) l has been considered. In this case, a series of low voltage (12 to 24 volt) transformers would be mounted above the HCU floor.

Each transformer would supply power to several igniters.

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Preliminary evaluation of this concept indicates that there would be sane effect on existing equipnent qualification, although physical nodifications to the igniters would be limited. The availability of qualified transfonners for this application is - also uncertain. In order to inplanent this design, replacement transfonwrs would be required to be placed within an enclosure which would protect the transfonner fran the harsh envircrrnent while allowing for cooling of the transfonner. As an alternative, consideration is being given to the placanent of transformers outside containment. Further evaluation, including cost and schedule inpact is underway.

4.0 Wetwell Cables 4.1 Incal Installation Details The only cablas located in the wetwell that are considered as essential equignent are those supplying power to the wetwell igniters. The igniter power cables are run in aluminum conduit and are in direct contact with walls and structural steel nanbers. In the vicinity of the igniters flexible conduit is used and is typically not attached to walls. These cables are Oakonite cables, using ethylene propylene rubber (EPR) insulation surrounded by two layers, the conductor jacket and outer jacket, of hypalon.

9 4.2 Analysis Results The~ cables- that are located in the flexible conduit are ccmpletely exposed to the high temperature envirorrnent. In order to provide supplanental protection to this portion of the cables a wrap insulation has been considered. We insulation considered censists of four layers of SILTEMP CH188 fabric providing a total thickness of 0.216 inches. Analysis shms that the ' cable in flexible conduit remains below 250 F, which is significantly below the qualification temperature of the cable and therefore survives the entire transient.

Analysis of the ceble located within conduit mounted onto walls has not been canpleted. We intended analytical approach is to determine the thermal response of the cable and to then calculate the life of the insulation using a Arrhenius technique. As shown above, if this method fails to denonstrate survivability of the cable, application of thermal insulation could then be used to enhance survivability.

5.0 Conclusions The evaluation of equiptent survivability enhancanents for the Rosemount transmitters indicated that relocation is not a feasible alternative. Of the renaining two options, insulation and shielding, both meet the acceptance criteria although scrne question

J renains regarding the inpact on envimmnital qualification for the insulation option. Since- the _ shielding option has no inpact on envite-eital qualification and meets all acceptance criteria this would be the most-feasible survivability enhancement.

For the hydrogen igniters located in the wetwell volume, the option of using close wrap. insulation is 'not feasible due to the putaiLial inpact on enviromental qualification. Likewise, relocation may not be desirable due to enviivmental qualification concerns and the extensive redesign and rework required. %erefore, the most feasible option for providing survivability enhancenents for the wetwell igniters would be thermal shielding.

Se evaluation of survivability enhanoceents for cable located in the wetwell indicates that the addition of external insulation significantly inproves the ability of this cable to survive a h A % i generation event.

In stenary, this evaluation has demonstrated that there are acceptable methods of enhancing the ability of equipnent to survive a hydrogen generation event. For each of the cwwe_nts . evaluated, a preferable method has been identified. If the results of the GSU final analysis and HCOG testing program indicate a need to enhance the survivability of equipnent required to survive a h A cjoi generation event this evaluation will be used to define the appropriate protection measures. Since the appropriate protection

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measures, if required,nust consider both deflagration and diffusion thermal envimsients, 'it is not prudent to provide equiI nent l

P1.0Lection at this time.

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Y REFERENCES

1. RBG-21,218 dated June 7, 1985, fr m Gulf States Utilities (J. E.

Booker) to Nuclear Regulatorv Cmmission (H. R. Denton) .

2. RBG-21,423 dated July 1, 1985, frm Gulf States Utilities (J. E.

Booker)- to Nuclear Regulatory Ccanission (H. R. Denton) .

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I Attachmnt 2 RESPCESES 'IO NRC STAFF QUESTICNS GSU/NRC Meeting August 12, 1985

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Questions and Ccanents fran'8/12/85 GSU/NRC Meeting

1. Provide additional information on the equipnent hatch and personnel

' air locks. Specifically, provide the type and nunber of seals.

Response: 'Ihe equipnent hatch located at El.103' 9", Azinuth 225 and radius 60'0" is provided with double O-ring seals. The personnel air locks are located at elevation 117'10" and elevation 175'O." Each airlock has an inner aM cuter door each

" of which is provided with 'a double inflatable seal. Each inflatable ' seal has its own air tank with makeup being provided' by the Instrunent Air Systen (IAS) . In addition, the air supply to aach seal is provided with a check valve such that loss of one seal does not effect the other seal. 'Iherefore, if the perfonnance of the innermost seal of the inner door is degraded, there will still be. three seals to protect containment integrity.

2. The 'NRC staff suggests adding the Reactor Pressure Vessel pressure

. instrumentation to the list of. equipnent required to survive a hy& % i burn event. In addition, the applicant should consider L aMing the non-ADS safety relief valves and the renaining containnent monitoring systan valves to this list.

Response: Gulf States Utilities agrees to add these to our list. of

- equipnent required to survive a hyi vf=n generation event. The specific equipnent to be added to this list is given in Table 1.

his equipnent will be incorporated into our final list of equipment to be presented in our final equipnent survivability report.

3. Provide additional information to justify exclusion of check valves fran the list of equignent required to survive a hydrogen generation event.

Response: Exclusion criteria nunber four of the equipnend:

survivability report (RBG-21,423 dated July 1,1985) stated tha-check valves which are qualified for reactor pressure and tanperature and which have no safety-related instrumentation or electrical function are ' assuned to survive a hydrogen burn mechanically. We HPCS check valve (E22*NNF005), the RHR check valves (E12*NNF041A, B and C) and the IPCS check valve (E21*NNF006) have been evaluated under our mechanical equipnent qualification program. All of these valves are 10 inch Atwood &

Morrill Co. testable check valves. We only non-metallic subempanents associated with the check. valve itself are the valve packing and gasket. 'Bo types of packing are used for these valves; Grafoil 235 and non-asbestos J. Crane 1630EU. The maxinum service terperature for these materials is 1000 F. We gasket material is Parker Style 911 (Grafoil & S/S) Spirotallic which has a maximum service tenperature of 1000 F. Since all non-metallic subcu p nents of these check valves have a high service tanperature and are effectively shielded fran a hydrogen

burn enviroment, their ability to survive a hydrogen burn is assured. In addition, the geserce of water on at least one side of the check valve will further enhance the ability of these valves to survive a hy&w generation event.

4. Provide the basis for the nunber of burns the Rosemont pressure transmitter, and other equipnent listed in the August 5, 1985, subnittal, can withstand.

Response: h evaluation of the nunber of wetwell burns the

_ equipnent located in the in+amadiate volume can withstand considered a small motor, a Target Rock solenoid, a Rosemont transmitter and power cable. 'Ihe Okonite power cable was evaluated against the maximtun continuous service tenperature of 440 F for an avm=re time of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. '1he cable was conservatively assumed to fail the first time that the EPR reached this taperature. As stated in the August 5, 1985, subnittal, this approach is conservative since the cunulative exposure time at this ta perature is much less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

'Ihe Rosemont transmitter was evaluated against a temperature of 303 F. As illustrated in our August 7,1985, subnittal this is conservative since the. transmitters' have been qualified at

' towatures in excess of 311 F for a mininun time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

'Ihese values are based on a Rosemont Model 1152 transmitter.

Since the pressure transmitters associated with RW water level and pressure have been replaced by Rosemont ledel 1154

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. transmitters, it- is more appropriate to use the qualification g tanperatures for these transmitters. 'Ihe Rosemont Model 1154 transmitters have a qualification temperature of 420 F and were tested at Wi w atures above 320 F for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. 'Iherefore future' evaluations of agni -ant survivability for these transmitters will use 320 F as the qualification tsoperature for the thermally limiting internal sub-conpanent. 'Ihe Target Rock solenoid was evaluated against a qualificaion ta perature of 385 F. To establish a more realistic. qualification bi W ature for the most . thermally limiting emponent. would require an evaluation of. the thermal response using the actual equipnent

qualification thermal profile. If this evaluation is necessary to . demonstrate equipnent survivability, the results will be incorporated into the final equipnent survivability report. '1he l Reliance motors- were evaluated against a qualification-Wi W ature of 340 F. Review of the qualification thermal profile indicates that the motors were tested at 346 F for three T.

I hours. 'Iherefore, use of 340 F is conservative.

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5. Provide additional justification on the ability of the contairment l

unit cooler mtor and hydrogen mixing system fan motor to withstand-

- a static pressure of 35 psig.

Response: 'Ihe. peak pressure resulting fran a forced, simitaneous wetwell, intadiate volume and upper contaiment burn was 35 psig.- Since the hy& m i mixing system will not be operating at j

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this time, the only cmponent of this systs susceptible to a high static pressure would be the hydrogen mixing system fan motor. Although this motor has not been sp rifically tested to pressures above 15 psig, other motors of similar construction have been demonstrated to survive elevated pressures. The hydrogen mixing system fan motor is a totally enclosed fan cooled,1.5 hp, NDR class 4 motor (Westinghouse TEEE 145T).

Review of the enviromental qualification test data for a Reliance motor indicates that this motor has been qualified to a pressure of 105 psig. Based on this emparison, it can be concluded that even though the hydrogen nixing syst s fan motor has not been qualified to pressures above 15 psig the fact that similar motors have been qualified to high pressurcs indicates that this motor will survive pressures produced by hydrogen deflagrations. '1he containment unit cooler fan motor, like the hydrogen mixing system fan motor, is also of open construction.

'Ihis motor is a 150 hp Westinghouse model 445'ICZ motor. Since it is similar in construction to other motors which have been qualified to high static pressures we have reasonable assurance that this motor will survive the pressures produced by hydrogen deflagrations.

Table 1 -

Peak Equipnent Description Make/ . Incation . Peak ,Wcident Equipnent Manufacturer Vendor Model/- EDC Zone. Azimuth. Accident EDC Qualified:

Identification' Function Catalog No. Iocation . Elevation D w ees Radius- b W ature Tenperature Contaiment 04S Containment Abuusgere Monitoring.

ICNS*SOV33A ~ Conf mi==nt Solenoid Valve, Target Rock CT-G 190'9" 61.55 59'9" 165 385 Atmosphere TRCP 77KK-003 Sanpling ICNS*SOV33AA TRCP 77KK-003 CT-G 128'4" - 20.61 61'1' 165 - 385 1 CMS *SOV33B TBCP 77KK-003 CT-G 190'2" 298.75 58'7"- 165 385 1CNS*SOV33BB TRCP 77KK-003 CT-G 138'6" 338.47 58'11" 165 385 1CNS*SOV33D TBCP 77KK-003 C-G 190'9" 245 59'6" 165 385 1CES*SOV33G TBCP 77KK-003 CT-G 165'4" 300.35 166'4" 165 385 1 CMS *SOV33H TBCP 77KK-003 C-G 182'3" 263.30 48'11" 165 ' 385 1CNS*SOV33J- TBCP 77KK-003 C-G 181'4"- 115.30 33'9" 165 385 1CES*SOV33K TBCP 77KK-003 CT-G 184'0" 53.56 29'2" 165 385 1CNS*SOV33S TBCP 77KK-003 CT-G 157'3" 278.95 54'8" 165 385 1CNS*SOV33T TBCP 77KK-003 CT-G 157'3" 250.79 54'5" 165 385 1CES*SOV33U TRCP 77KK-003 CT-G 190'9" 26.08 57'5" 165 385 1(ES*SOV33V TRCP 77KK-003 CT-G 190'9" 335.83 57'0" 165 385 1CES*SOV33W TBCP 77KK-003 CT-G 145'6" 23.56 56'1" 165 385 1CNS*SOV33X TBCP 77KK-003 CT-G 145'6" 332.58 58'7" 165 385 1CNS*SOV33Y TRCP 77KK-003 CT-G 143'5" 145.00 39'10" 165 385 1 CMS *SOV33Z TRCP 77KK-003 CT-G 145'9" 223.20 39'9"- 165 385

Peak ..

Equipnent Description Make/ . Iocation Peak - Accident Equipnent Manufacturer Vendor Model/ EDC Zone Azinuth Accident EDC . Qualified-Identification Function Catalog No. Incation Elevation Degrees . Radius TEERperature TERperature Drwell Safety Relief Valves. .

1B21*RVF41A Depressurize Crosby 8xRx10, DN 132'4"- 50.91 19'0" 330 340 F:

Reactor Style HB-65-DF Vessel-1B21*RVF41G Style H3-65-DF DW-1 132'5" 76.21 24'3" 330 340 F.

1B21*RVF41L Style HB-65-DF DW-1 132'4" 63.07 25'5" 330 340 F 1B21*RVF47B Style HB-65-DP DW-1 132'5"- 271.90 23'7" 330 340 F 1B21*RVF47D Style HB-65-DF DN-1 132'3" 316.34 19'7" 330 340 F 1B21*RVF47F Style HB-65-DF DW-1 132'4" 302.58 25'3" 330- 340 F IB21*RVF51B Style HB-65-DF DN-1 132'5" 283.79 24'3" 330 340 F IB21*RVF51C Style HB-65-DF DN-1 132'5" 82.07 23'9" 330 340 F 1B21*RVF51D Style HB-65-DF DW-1 132'3" 325.99 19'11" 330 340 F M

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g w Equipnent Description Make/ ..

Iocation Peak Accident?~ '

Rpipment Manufacturer Vendor Model/ EDC Zone Azinuth ' Accident EDC Qualified Identification Function Catalog No. Iocation- Elevation Degrees Radius Tenperature Teperature Contairunent .

Reactor Instrumentation '

1B21* PIN 62A Measure RPV Rosatont Pressure CT-G 117'6" 46.54 111'8" 165 F 420 F Pressure Transmitter Model 1154 1B21*P1W62B Rosanont Pressure CT-G 117'6" 197.06 c U 109'10" 165 F 420 F.

Transmitter Model 1154 -

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