ML20091F811

Forwards Responses to SER Confirmatory Issue 71 (Humphrey Concerns) Action Plans 5,6,8 & 21 & Revised Responses to Action Plans 2 & 3

ML20091F811
Person / Time
Site:	Clinton
Issue date:	05/25/1984
From:	Herborn D ILLINOIS POWER CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
0982-L, 982-L, U-0714, U-714, NUDOCS 8406040024
Download: ML20091F811 (34)

Text

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U- 0714 0982-L P23-84 05 -25 )-L

'ILLINDIS POWER 00MPANY IP CLINTON POWER STATION. P.o. BOX 678. CLINToN. ILLINOIS 61727 May 25, 1984 Docket No. 50-461 Director of Nuclear Reactor Regulation Attention:

Mr. A. Schwencer, Chief f.icensing Branch No. 2 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Subj ect: Clinton Power Station Unit 1 SER Confirmatory Issue No. 71 Humphrey Concerns

Dear Mr. Schwencer:

Illinois Power Company letter dated June 17, 1983 (refer U-0644) addressed some of the John Humphrey concerns as applicable to the Clinton Power Station (CPS). Enclosed are CPS responses on some additional Humphrey issues for NRC Staff review. Included are Action Plans 75, 6, 8, 21 and revised responses to Action Plans #2 and 3.

We believe that these responses will resolve the particular concern involved.

If there are any questions regarding this material, piease contact me or J. H. Shepard at (217) 424-6785.

Sincerely yours, l%

Daniel I. Herborn Director - Nuclear Licensing and Configuration Nuclear Station Engineering Attachments

-GEW/ lam.

GEW15/M2 G. A.- Harrison, NRC Clinton Licensing Project Manager cc:. L. C. Ruth, NRC CSB NRC Resident 0ftice Illinois Department'of. Nuclear Safety

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e e-Action Plan 2 (Revised) 1.3 Additional submerged structure loads may be applied to submerged structures near local encroachments.

1.4 Piping impact loads may be revised as a result of higher pool swell velocity.

Response

A new SOLAV01 analysis was performed for Clinton in response to a design change to the encroachment of the CPS suppression pool.

The design change consisted of increasing the 5.5 foot encroachments in the suppression pool to 8.5 feet.

The encroachment was increased by replacing the. existing grating with steel plate (see response to Action Plan 3).

The SOLAV01 analysis was reperformed using FSAR pressure histories.

The loads on the' submerged structures.in encroached regions of the suppression pool during pool swell have been eval-uated and compared to identical structures and locations using GESSAR II design loads. -The GESSAR II design loads bound all the encroached submerged structures except for the hydrogen compressor sparger which has.a calculated load of 718 lb/ft.

The structure has sufficient margin in the design to withstand the. pool swell load.

The effect on the Clinton boundary loads have been. reanalyzed for the design change to the CPS encroachment.

The analysis shows that CPS-vent air clearing boundary loads under the1 encroachment do not: exceed the design base loads.

The SOLAV01 analysis results show that pool swell in the-encroached regions of the pool will result in froth.and-water im3act on pipes above1the suppression pool.

The.

piping above the encroached region of the pool was identi-'

fled by a review of~the design drawings.

Five piping' worst -

'subsy' stems were identified in that-review' to be the case, based on:an assessment of pipes'having significant horizontal runs or are not presently. shielded from the-pool swell loads.

These subsystems were evaluated for the pool swell loads and results. reveal that the piping;is adequately designed for the froth / water impact.

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't-Action Plan-3 (Revised) 1.5 Impact loads on th'e HCU floor may be imparted and the HCU modules may fail which could prevent successful scram if:the bubble' breakthrough height is raised appreciably by local encroachments.

Response

A new SOLAV01 analysis was' performed in response.to a design change to the' encroachment of the CPS suppression pool.

The encroachment was increased by replacing the existing grating'with 1%" steel plate, as shown in Figures 3-1 and 3-2.

The plate extension has the effect of diverting the water toward the outer portion of the containment, which prevents water slug impact on the HCU floor.

Loads for various structural members of the HCU floor over the equipment and personnel hatches were calculated using FSAR pressure histories.

Figures 3-1 and 3-2 show the-plate modification which extends three feet radially beyond the equipment hatch and personnel 1 hatch, respectively.

SOLAV01 predicts the worst-case pool swell to occur at the midpoint of the circumferential cross section of the encroachment that is the furthest from the clean pool.

GE's containment response model was run for Clinton's new pool geometry using FSAR input' assumptions to determine.the drywell and wetwell pressure time histories (see Figure 3-7).

The small decrease in,open pool area has'a negligible'effect on the bulk pressure response.

The initial bubble pressure under.the modeled encroach-ment is equal to the bubble pressure-determined for.

.the SOLAV01 case that assumes the-encroachment covers a 360 arc.

This bubble' pressure is used until coale-scence occurs circumferential1y. -The'3600 encroached' bubble pressure. is - ramped down t'o a new equilibrium pressure in-the' time that it takes for an acoustic ~ wave.

to-make two round trips :between the encroached bubble and the' clean case bubble using an' acoustic speed of 1100-fft/sec.

The new' equilibrium'pressureLwgs taken to be the bubble pressure under a theoreticali360 average encroach-

. ment case such that the. total surface area of theLencroach-ments.is maintained.- -The. average encroachment. was t calculat'ed

-to be a 4.4-foot 360 encroachmentras seen.in Figure 3-3.

tat the timerthat the clean _ pool experiences breakthrough (the time at which.the water slug thinsEto 2.-5 feet)'the.

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bubble pressure is ramped down to.the wetwell airspace pressure and remains-there for the duration of the transient.

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Figure 3-4 shows the resultant SOLAV01 mesh for the 5.5 foot encroachment plus 3-foot extension case.

Figure 3-5 shows the resultant bubble pressure time history.

The analysis indicates that liquid impact.does not occur on the concrete portion o~f the HCU floor and steam tunnel.

Figure-3-6 shows how the bubble and pool surfaces grow.

3 The pool swell velocity results generated by SOLAV01 were used.to calculate impact loads on the radial and circum-ferential HCU floor beams using the equation:

2I P max = 7zz-where P max = peak pressure (psi) 2 i

I = impulse per unit area (lbf-sec/ft )

r = impulse duration (sec)

The Mark II method was used to determine-the values for I and1 with the exception of the radial beams.. The duration of1the impact load for these beams.was found by calculating the " sweep' time.

The " sweep" time is defined as the difference in time when the beam is.first impacted and when the last11mpact occurs.

' Drag-loads were-calculated by using the peak impact

. velocity and:the drag coefficient, C

=2.0, in Darcy's D

equation.

The durations of the drag _ loads were assumed to-be equal to the-time it takes the impactingJsurfacesto' decelerate withfgravity to zero..

Grating doesinot experience an~ impact-load (referenceil).

The' drag ~1oad. experienced by the grating.above the-HCU floor beams is bounded by the.designEgrating drag: loads.

Since there is no encroachment'beneath the main steam.

- tunnel and since Figure 3-8 (Clinton FSAR Base Case Pool Simulation).shows breakthrough at'14.5 feet above the.

initial. pool 1 surface,-the' original-GESSAR'II impact. loads still apply, i

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Tlie HCU floor' beams were analyzed for the developed water impact and drag loads.

'A dynamic analysis _showed that the. loads due to water slug impact are bounded by the froth impact design loads.

Resultant. stresses in the radial beams were: calculated to be 15% of the allowable.

Resultant stresses in the. concrete portion of.the HCU

-floor were calculated to be 22% of the allowable.

In conclusion, the loads as the result of pool _ swell around the extended encroachment are bounded by design basis loads.

References:

GESSAR II, Appendix 3B.10.1, GE Report No. 22A7007, Rev. O, 1982 4

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CLI?iTO.'i FS AR BASE CASE POOL SIP.ULATIOri 3-11

e Action Plan 5 2.1 The annular regions between the safety relief valve lines and the drywell wall penetration sleeves may produce condensation oscillation (CO) frequencies near the drywell and containment

~

wall structural resonance frequencies.

2.2 The potential CO and chugging loads produced through the annular area between the SRVDL and sleeve may apply unaccounted-for loads to the SRVDL.

Since the SRVDL is unsupported from the quencher to the inside of the drywell wall, this may result in failure of the line.

2.3 The potential CO and chugging loads-produced through the annular area between the SRVDL and sleeve may apply unaccounted-for loads to the penetration sleeve.

The loads may also be at or near the natural frequency of the sleeve.

Response

The program for. resolution to close this issue at Clinton is as follows:

5.1 The existing condensation data will be reviewed to verify that no significant frequency shifts occurred.

The data will also be reviewed to confirm that the amplitudes were not closely related to acoustic effects.

5.2-The driving conditions for CO at.the SRVDL-exit will be calculated.

Based on these calcula.

tions, existing test data will be used to estimate the frequency and bounding pressure amplitude of CO at the SRVDL annulus exit.

5.3 A wide difference between the CO frequency i

and structural resonances will lue demonstrated.

The margin between the new loads and existing loads will be quantified.

l 5.4 Provide a detailed description of all hydrodynamic i

and thermal loads that are imposed on the SRVDL' and the SRVDL sleeve during LOCA'blowdowns'.

l 5.5

' Assure that thermal loads created by steam flow

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through-the annulus.have been accounted for in the design.

t 5-1

s. :

5.6 State the external pressure loads which the portion of the SRVDL enclosed by the sleeve can withstand.

5.7 Calculate the maximum lateral loads which could be applied to the sleeve by phenomena analogous to the Mark I and Mark II downcomer lateral loads.

Items 5.1 and 5.2 have been completed.

Results were submitted in letter from L. F. Dale, MP&L, to H. R. Denton, NRC, Reference #AECM-82/574, dated December 3, 1982.

These results are applicable to Clinton.

Item 5.3, a sleeve C0 pressure time history was constructed for Clinton.

This Clinton specific pressure time history assumed the hydraulic diameter of the sleeve annulus was the appropriate parameter for scaling this load from the main vent to load definition.

The Containment Issues Review Panel (CIRP) contended that.for scaling the CO load the appropriate parameter should have been the penetration sleeve diameter.

The Clinton specific analysis considers the more severe load magnitude and a frequency range of 5.5 to 56 Hz.

The SRVDL sleeve CO load described induces additional stresses in all of the submerged structures in the Clinton suppression pool.

The additional stresses induced by the consideration of SRVDL sleeve CO are within the capability of these submerged structures.

In response to.5.4 a detailed description of the hydro-dynamic and thermal loads included in the design basis of the SRVDL piping and the SRVDL sleeve during LOCA blowdown is given below.

SRVDL Piping a.

Hydrodynamic Loads 1)

Dynamic response due to SRV (single valve,.all valves and ADS actuation 2)

Horizontal Vent ChuggingCondensation Oscillation 3)

Drywell Negative Pressure.

4)

Drag Loads due to Quencher Air Clearing 5)

Steam Hammer due to Fast Valve Opening / Closing 6)

Main Vent Air Clearing 7)

Impact,. Drag, and Fallback Loads'due to Pool Swell 5-2

..e 8)

SRVDL Sleeve Water Jet Load 9)

SRVDL Sleeve Annuli Chugging / Condensation Oscillation

10) SRVDL Sleeve Lateral Loads b.

Thermal Loads Thermal loads on piping based upon the maximum steam temperature in the MSRV line.

-SRVDL Sleeve a.

Hydrodynamic Loads 1)

Dynamic response due to SRV (single valve, all valves), ADS Actuation 2)

Horizontal Vent Chugging / Condensation Oscillation 3)

Drag' Loads due to Quencher Air Clearing 4)

Seismic Pool Slosh 5)

Vent Air Clearing 6)

Impact, Drag, and Fallback Loads due to Pool Swell 7)

SRVDL Sleeve Annuli Chugging / Condensation Oscillation 8)

SRVDL Sleeve Lateral Loads b.

Thermal Design Thermal stresses based on steam flow through the annulus or accident condition have been accounted for.

-Item 5.5, external drag loads due to the sleeve CO have been generated for the DBA condition. Evaluation of this new sleeve CO drag loads and the thermal loads created by steam. flow has been performed.

Results showed that both the SRVDL and the penetration ~ sleeve have sufficient margin in the design to accomplish the new loads.

External. drag loads due to sleeve CO were' assessed for the non-MSRV structures in the suppression. pool by reviewing the submerged piping stress report..

Results showed sufficient margin to accommodate this new load.

5-3 i

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Item 5.6, the maximum allowable external pressure load which the safety relief valve discharge lines (SRVDL) can withstand in the region enclosed by the drywell wall penetration sleeve is 500 psi (per ASME Code Section III, ND 3133.8).

The maximum external pressure load these pipes may be subject to is the lateral load described in Item 5.7.

The maximum lateral load on an SRVDL is conservatively calculated to be 217 psi.

In response to 5.7 the maximum lateral load which would be applied to the Clinton SRVDL s and sleeves based upon General Electric's response to the CIRP Question 5.7.1 is 28 Kips.

The resultant loading is defined to be:

F=28000 sin (fhhy) lbf; 0 < t 4.003 see Results of assessments which applied this load to the SRVDL as a uniformly distributed force over 1 to 4 feet from the vent end, show sufficient margin in the SRVDL design to accommodate this additional load.

The SRVDL sleeve can also accommodate this load when similarly applied.

e 4

5-4 I

I-4.

Action P an 6 l

3.1 The design.of the STRIDE plant did not consider vent clearing, condensation oscillation and chugging loads which might be produced by the actuation of the RHR heat exchanger relief valves.

3.3 Discharge from the RHR relief valves may produce bubble discharge or other submerged structure loads on equipment in the suppression pool.

.3. 7 The concerns related to the RHR heat exchanger relief valve discharge. lines should also be addressed for all relief lines that exhaust into the pool.

Response

The following items have been evaluated to address the above issues:

6.1 The vent clearing loads associated with actuation of the RHR relief valves will be calculated.

The water jet loads will also be calculated.

The dynamic loads associated with relief valve operation will be recalculated to evaluate relief valve discharge line design.

The following information will be submitted for all. relief valves which. discharge to the suppression pool.

6.2 Isometric drawings and P&ID s showing line and. vacuum breaker location will be provided.

This information will include the following:

The geometry (diameter, routing, height above the suppression pool, etc. ) of

'the pipe line from immediately downstream of the relief.

valve up to the line exit.

The maximum and minimumt expected submergence of the discharge line exit below the pool surface will.be included...Also, any lines equipped with load mitigating devices (e.g., spargers,.

quenchers) will be noted.

6.3 The~ range of flow rates and character of fluid (i.e.,

air,. water, steam) which is discharged through the line and the plant conditions (e.g., pool temperatures) when discharges occur will be defined.

~6.4 The sizing and performance characteristics (including nake, model, size, opening' characteristics and' flow characteristics).of any-vacuum breakers provided for relief valve-discharge-lines will be noted.

i i

4 6-1 o

6.5 The potential for oscillatory operation of the relief valves in any given discharge line will be discussed.

6.6 The potential for failure of any relief valve to rescat following initial or subsequent opening will be evaluated.

6.7 The location of all components and piping in the vicinity of the discharge line exit and the design bases will be provided.

Item 6.1 The RHR/SRV air clearing loadshave been calculated based upon failure of the pressure control valve (PCV) during either a steam condensing mode (SCM) start-up or a normal steady SCM of operation.

The air clearing loads are conservatively based upon the maximum RHR/SRV flow rate, a maximum water reflood height of 12.95 ft. and Clinton unique vacuum breaker and discharge line characteristics.

These subsequent actuation air clearing loads on the CPS suppression pool boundary have been generated in a manner consistent with the main steam SRV boundary load definition.

The maximum predicted RHR/SRV bubble pressure on the suppression pool boundary (containment wall) was calculated to be-54.9 psid.

The effect of this load has been assessed and found to be within the design basis.

The effect of a RHR/SRV subsequent actuation air clearing load on the RHR relief line's supports has been assessed.

The resulting stresses are within the design basis for these All RHR/SRV air clearing loads act symmetrically structures.

on the RHR relief line, therefore uself loading was not i

considered.

Water jet loads resulting from the actuation of the RHR/SRV

-do not impact any submerged structure in the Clinton suppression pool and are therefore were not considered.

The Mark II' lateral load on 24-inch downcomers of 65 Kips, which has a non-exceedance probability of 10-5 (see NUREG-0808), has been scaled to account for. lateral loads on the. smaller RHR safety relief valve lines.

The-resulting definition for the lateral load on the RHR heat exchanger relief line used by GE is:

4 F = 32500 sin ('O 003 ) lb 0 st40.003 sec f

~This load was uniformly distributed along the final 1 to 4

[

feet of :the RHR relief line.

The effect of this load has been assessed and found to be within the design basis.

I r

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. m -

4 Items 6.2, 6.3, and 6.4 7

I

- Lines-discharging into or taking suction from the CPS

- suppression. pool are described in Table 6.1.

The flow rates and character'of the fluid (air, steam, water, etc.) which is discharged through.these. lines and the plant conditions (fluid discharge temperature) when discharging occurs are described.

The characteristic of vacuum breaker used on the CPS discharge line are also described in Table 6.2.

Isometric 1

?

drawings and P&ID s showing line and vacuum breaker location

-are listed.in Table 6.3.

Item 6.5

_i The RHR heat-exchanger relief valves, E12F055A and B, could ex7erience oscillatory action due to undefined cyclic behavior of the steam pressure reducing valves E12F051A and B, which are air operated solenoid. valves that fail close.

The time for these pressure reducing valves to reach full open is 16 seconds,' thus any postulated oscillation of the relief valves would be slow.

Item 6.6 In this scenario, it is postulated that the RHR/SRV fails-open due to a mechanical failure during steady SCM operation.

The PCV will open and try to maintain the RHR pressure at i;

200 psig.

Assuming substantial-steam condensation in the-RHR, the PCV will not be able to maintain'the RHR pressure at.200 psig.

The RHR pressure will drop to a new steady-state value such that the. steam flow into the RHR through

. the~PCV is equal to the sum of the steam condensation rate and the steam flow through the failed open SRV.

The flow rate through the failed open RHR/SRV is below the flow conditions at the 500 psig setpoint.

t 1

Item 6.7 All submerged structures in the CPS suppression pool were assessed for theLeffects of the RHR/SRV air clearing loads.

2 Only nine:non-MSRV lines and supports.were found-to be subject to RHR/SRV air. clearing loads which.are more severe-than the MSRV air clearing loads to which they were designed.

Results indicate that there is no need for design changes.

based upon present load combinations even when the RHR/SRV subsequent actuation air clearing load is incorporated.

a l

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P TA8LE 6.12

^t: ~

. ECC3 RELIEF / VALVE LINE DISCHARGES TO, SUPPRESSION POOL - DESIGN CONDITIONS -

,8

=

..J>.

p o

System'.

. Set.

Operating

. Line-Valve

- Line,' Sire-Pressure Size, Model Pool Fluid

' Mode & R/V De'eription No.

~

' Capacity (psig)

& Make Submergence

'Chara.

~ Inlet Temp.

Drawing -

Function d

- RCIC ~

1E51F090' _ 1RI24C2'

'69 gpm

'1478 Dresser-726'-11" water 170er:

M35-1079,.

Peturn to RCIC$

3/4-1975-3 sht. 2 Tank (3-1-1-2)-

XFA50-NC

.3007 Size:

3/4x1(in.)

x 1RI0 8812"*

• Steam h us r

723'-2-1/B

steam 0

ar LPCS' 1E21F018-1LP21s4" 164.1.gpm.

554 Dresser 726*-11' water Accident M05-1073 LPCS Pump, 1/2-1970 Conditions Disc. R/V:

7

-2 ( 3-1 2 )-

3 XFA19-Nc3007 Size:1S*x2'

't -

1E21F031-

.1LP2184*

30 gpm 100 Dresser 726'-11" water Sys. Standby M05-1073 LPCS Jockey Pump 1970 Duty 200*F Suc. R/V

-2(3-1-1-2)

XFA31-NC3007' Size:1*x1g * '

-RHR 1E12F025A 1RH41CA1 "*

65.8 gym 477' Dresser 726'-11" water LPCI M05-1075, RHR Pump A

.1970

- 2 ( 3-1-1-2 )-

'170*F sht. 1 Dis. - R/V.-

XFA32-NC3007 -

Size:1S*xt*

1E12F0258 1RH41581S*

I 66.4 gpm-484 Dresser-1-'

726'-11' water LPCI M05-1075, RHR Pump B 1970 170*r sht. 2 Dis. R/V

-2 (3-1-1-2).

XFA32-NC3007 Size:1S*x2*-

1E12F025C- ' 1RH41CC1 * '

66.4 gpm 484 Dresser 726'-11' water LPCI M05-1075, RHR Purrp C 1970 9

170*F sht. 3 Dis. R/V

-2 ( 3-1-1-2 )-

XFA32-NC3007

-Size:1S*x1" I

6-4 --

m 8

e 9

w m..--

y T,

R TABLE 6.1 (Cont'd) t

[]

e ECCS RELIEF / VALVE LINE DISCHARGE TO SUPPRESSION POOL - DESIGN CONDITIONS System Set Line.

Operating

. Description.

Valve.

Line, size Pressure Size; Model Pool Fluid Mode & R/V No '

Capacity (psig)

's Make i

Submergence Chara.

Inlet Tertp.

Drawing Function 1E12F017A 1RH17CA1'*

43 gpm 200 Dresser-1

• 726'-11*

water Sys. Standby-M05-1075, RHR Jockey Pump

- RHR

- N. '

1970 Duty 90*F Sht. 1

.A Suc. R/V

-2(3-1-1-2N XFA3 2-NC30 01-Size:1g*x1" 1E12F0178 1RH178Bl\\*

43 gpm-200 Dresser 726'-11*

water Sys. Standby -

M05-1075, RMR Jockey Pump '

1970 Duty 90'F.

Sht. 2 B Suc. R/V

- 2 ( 3-1-1-2)-

XFA 32-NC3007

, Size:1g*x2" RHR' 1E12F055A' 1RH30CA12*

'5.6x105 500 Crosby 726'-11" Steam Steam condensing M05-1075, RHR H.Xch. A lbm/hr.

'DS-C-64339 480'F Sht. 4 R/V Size:12*x8' t

I 5

1E12F0558 : IRE 30CB12

• 5x6x10 500 Crosby 726'-11' Steam Steam Condensing M05-1075, PJ1R H.Xch. - B 8

lbm/hr DS-C-64339 480'r Sht. 4 R/V Size:12*x8*,

RHR 1E12F101-1RH17CC1 30 gpm.

100

-Dresser 726*-11*

water 200*F M05-1075,-

RHR Pump'C Suct 1970

'Sht. 3

-2 ( 3-1-1 XFA31-NC3007 Size:1h*x1'.

RHR 1E12F005 1RH12C1\\'*

40.5 gpm 200 Dresser-1-'

726'-11*

water Shutdown Co611ng M05-1075, RRR Shatdown ' Suc.

1970 358'F Sht. 1 R/V Disc.

-2 ( 3-1-1-2)-

XFA 32-NC3007 Size:1 "x1" RHR 1E12F036..

1RH2886* '

374.4 gpm 75

. Dresser 726'-11*

water.

Steam condensing M05-1075, Condensate to

~

1910L 140*F Sht. 4 RCIC Pump Suction

-1 (1 3 - 2 )-

XNC3007 Size:6*x4' R;(R 1E12F030 1RH56Bl\\"

'.42.7 gym 197-Dresser 726'-11' water 200*F M05-1075, Flush to Radwaste 1970

-2 ( 3-1-1 Sht. 2 XFA3 2-NC3007 31te:1h*x2"'

RHR None 1RH39C14" 726'-11*

M05-1075, 6-5 Sht. 3 t

/

s

UT

~

TABLE 6.1' (Cont'd) -

a>

ECCS RELIEF / VALVE LINE DISCHARCES TO SUPPRESSION POOL - DESIGN CONDITIONS 4

h.'

N System Set Operating Line

- Valve s

De^cription' No.

' Line, Size Pressure Size, Model-Pool Fluid Mode & R/V Capacity (psig)'

E Make Submergence Chara.

Inlet Temp.

Drawing Function

^

- HPCS 1E22F014

.1HP18C12*

15 gpm 100 Dresse r-3/4-726'.-11*

water.

Sys. Standby M05-1074, HPCS Jockey Pump' 1975 D, (

Duty 90*F.

Sht. 1 '

Suc. R/V-

-3 (1-1-2) -

XFA4 9-NC3007 Site s 3/4 *x1*

HPCS 1E22F039-1HP18C12 66 gpa 1560 D re s s e r-3/4-726'-11" M05-1974,.

1975 Sht. 1

-3(3-1-1-2)-

XFA50-NC3007 Site s 3/4 *s t' HPCS 1E22F035 1HP18C12*I 66 gpa 1560 Dresser-3 4 '

726*-11'

' water Accident M05-1074, HPCS Pump Disc.

1970 Conditions Sh t.

1-R/V

-2 ( 3-1-1-2 3-170*F XFA55-NC 3007

' Size:3/4*x1*

~

HG None 1HG05CB6**

N/A N/A-N/A 723'-11" air / steam N/A.

M05-1063 H2 Sparger

.9249' A3 34 psid M06-1063

'Div II.

=

HG None 1HG05CA6**

N/A N/A N/A 723'-11" air / steam N/A M06-1063 H2 Sparger

- 969* AE.

>4 psid -

M05-1063

.Div I SF -

None

'1SF02A12"'

'N/A N/A N/A 726'-11*-

N/A N/A M05-1060 Suppression Pool

}

Clean-up & Transf.

SF "None 1SF01F12' N/A N/A N/A 720'-0*

N/A N/A M05-1060 Suppression Pool 966* At Clean-up & Transf.

f f

Discharge Line..

• • Discharge Line with Sparger' l

1 6-6

O TABLE 6.2 VACUUM BREAKER DATA 7

RHR DISCHARGE LINES VACUUM BREAKER RELIEF VALVES:

1E12F103A&B, 1E12F104A&B MANUFACTURER:

GPE CONTROLS SIZE:

2" VACUUM RELIEF VALVE, 600# FLANGE W/0PERATOR 2

DISC AREA:

3.14 IN 2

FLOW AREA:

2.96 IN 2

A/{g=0.029ft FLOW COEFFICIENT - FULLY OPEN:

SET PRESSURE:

0.2 PSID MINIMUM OPENING PRESSURE RCIC DISCHARGE LINE VACUUM BREAKER RELIEF VALVES':

1E51F079, 1E51F081 MANUFACTURER:

GPE CONTROLS SIZE:

2" VACUUM RELIEF VALVE, 600# FLANGE'W/0PERATOR DISC AREA:

3.14 IN FLOW AREA:

2.96 IN

~

2 FLOW COEFFICIENT FULLY OPEN:

A g = 0.029ft SET PRESSURE:

0.2 PSID MINIMUM OPENING PRESSURE e

e 6-7

~

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TABLE 6.3 r e-Jl M05-1060 Sh. 1 Rev. K I

'd

'M05-1063 Sh. 1 Rev. F

M06-1063-Sh. 1 Rev. S M06-1063 Sh. 3 Rev. R M05-1073 Sh. 1 Rev. M e

'M05-1074 Sh. 1 Rev. K

,,y M05-1075.i Sh. 1 Rev. L M05-1075 Sh. 2 Rev. L M05-1075 Sh. 3 Rev. K M05--1075 Sh.-4 Rev. J M06-1075 Sh. '4 Rev. V M06-1075 Sh. 10 Rev. AA M06-1075 Sh. 19 Rev. Y

,a M06-1075 Sh. 20 Rev. V M06-1075' Sh. 23 Rev. Z ut M07-1075 Sh. 4 Rev..M 7.

jc M05-1079 Sh. 1 Rev. J M05-1079 Sh. 2 Re" M06-1079 Sh. 3 I

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H l-4.

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,b Action Plan 8 3.4 The RHR heat exchanger relief valve discharge lines are provided with vacuum breakers to prevent negative pressure in the lines when discharging steam is condensed in the pool.

If the valves experience repeated actuation, the vacuum breaker sizing may not be adequate to prevent drawing slugs of water back through the discharge piping.

These slugs of water 3

may apply impact loads to the relief valve or be discharged back into the pool at the next relief valve actuation and apply impact loads to submerged structures.

3.5 The RHR relief valves must be capable of correctly functioning following an upper pool dump which may increase the suppression pool level as much as five feet creating higher back pressures on the relief valves.

' Response The following items have been evaluated to address the above issues:

8.1 A failure mode analysis on the pressure controller to establish all possible failure modes will be performed.

8.2-The system design will be reviewed to determine if-subsequent valve operation is feasible.

8.3 Based on the results of Item 2, the appropriate. loads will be determined.

This will be the water jet and air bubble load created by a first actuation of the relief valve and either a second " pop" load' based-on subsequent-actuation or condensation oscillation loads based on continuous venting.

8.4 The vacuua breaker performance will be quantified!as applicable.

This will include a calculation bhowing the' maximum elevation to which' water can beidrawn into the RHR relief valve discharge line.

8.5 Analyses demonstrating that the. heat exchangers are-capable of withstanding an' overpressure transient will-be completed.

RHR relief valves will be. demonstrated to be capable of functioning following an upper pool dump.

J8-1

.E 1

. t a

' Item'8.1 Possible failure scenarios for the RHR leading to steam flow through the RHR/SRV discharge line are described below.

Steam discharge through the RHR/SRV discharge line can only occur during the steam condensing mode (SCM).

In this mode the RHR heat exchanger is used as a condenser to absorb the decay heat from the BWR during hot standby.

The steam condensing mode may also be used for heat rejection in the post-LOCA period.

A schematic of the RHR in_SCM is shown in Figure 8.1.

The steam flow into the RHR heat exchanger is controlled ~by a pressure control valve '(PCV) that is set to maintain a desired pressure in the RHR. heat. exchanger.

The Clinton Power Station RHR system design does not have non-condensible bleed lines running between-the RHR. heat exchangers and-the 1

reliefLdischarge lines.

This fact makes the Clinton RHR system design different from both Perry and Grand Gulf designs.

The only way that steam flow ~into the Clinton RHR relief discharge line can occur.is through-the safety relief valves (SRV) that are provided to prevent over-pressurization of the 1GHL heat exchangers.

.The various scenarios leading to steam flow through-the discharge line are' discussed below.

Summary The worst water / air clearing loads are expected for Scenario 3'or 7 where the PCV fails open.

Thefexpected steam mass flux through the discharge pipetcovers a wide range from less than-0.5Llbm/sec./sq, ft.fto 198 lbm/sec./sq. ft. Land

~

backflow from the RHR heat exchanger line.' Significant-reflood ofLthe discharge-line is' generally expected during conditions where steam mass flux is below 6 lbm/sec./sq. ft.

Reflood;is' expected in these same. scenarios and isJaddressed

-in the response to' Action Plan 8.2'and 8.4.

Scenario 1 - Normal-SCM Start-up During. normal'SCH start-up there will.be:no. steam mass flow through the' discharge:line into the suppression pool ~.

. Scenario 2'- SRV Failure'd' ring SCM Start-up u

,During the-SCM-start-up it-is-postulated that the.SRV fails openidueftola mechanical 1 failure.

The PCV!will'open'to.

-maintain'~ the ' pressure. in the:RHR heat exchanger at - the-50 '

psig" set pressure.

Thefsuddentopening of the;SRV EwillJcausa

. the water ;and air ~to Eclear from the? discharge. line. : Moderate

' water *and airiclearingqio,adstarelexpected.

cs i s

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i '.

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T8-2D 4

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.a

.. :;; y After theLinitia1' transient caused-by the failed open SRV, equilibrium is rapidly established in the RHR system with the-input steam flow through the-PCV being balanced by the

-outflow through the_ fully open SRV.

Note that no steam condensation occurs in'the RHR heat exchanger because the tube sheet is covered with water during start-up.

The resulting steam mass; flux through the. discharge line is expected to be between 8'and 16 lbm/sec./sq. ft. and rigorous chugging is expected at the exit of the discharge line.

Scenario.3 - PCV Failure During SCM Start-up-In this scenario it is postulated that a mechanical failure of the PCV (see Figure 8.1) occurs and it pops open as soon-

~

as the steam block valve from reactor is opened.

The RHR heat exchanger will pressurize rapidly to'the SRV set point.

At this point,-the SRV will open and discharge steam'to the suppression pool;through the discharge line.

Again during the SCM start-up, no condensation occurs in the 10HL heat exchanger; therefore, all the steam ' flow through the failed-open PCV must flow out through the-SRV' discharge line.

Sonic condensation is expected at the discharge line exit.

The maximum flow through.the RHR/SRV at these' conditions is only slightly greater than that through the failed-open PCV.

Therefore, the SRV.will cycle rapidly,La1 subsequent

. failure of the SRV must be considered.

Failure of the'SRV will only'cause the pressure in the RHR heat exchanger 1to drop a little below the-set point.for the SRV.

This is due to the RHR/SRV failing in'the-open position ~and slowly i

relieving the system pressure until equilibrium flow through both the PCV and SRV is achieved.

Scenario 4 - PCV and SRV Failure:During SCM Start-up The final scenario 1that can be postulated during SCM start-up I

is the one where.there is a simultaneous ~ failure of both the PCV and~the SRV-Such' double failure exceeds the single failure criteria. ~In anyfcase, the waterLand air-clearing loads as well as the condensation loads.for this scenario are-

' bounded by-.the worst-caseiloads.

x

~ Scenario 5; Normal Steady-State SCM. '

4 f

'This is'the same as:" Scenario l'

.. Normal}SCM. Start-up.""

Clinton'sLdesign~does notrallow foria bleed' steam flow to the RHR/SRV1 discharge 11neh 4

f i

s.

8-3 1

I

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fF f ;,

.L

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-Scenario 6 SRV Failure During Steady SCM LIn-this scenario it is postulated that the SRV fails open due to a mechanical failure during steady SCM operation.

The PCV will open and try to maintain the RHR heat exchanger

. pressure at 200 psig.

Assuming substantial steam condensa-tioniin the RHR heat exchanger, the PCV will not be able to maintain the RHR heat exchanger pressure at 200 psig The RHR' heat exchanger pressure will drop to a new steady-state value such that the steam flow into the RHR system through the PCV is equal to the sum of the steam condensation rate and the steam flow through the failed-open SRV.

The flow rate through the failed-open RHR/SRV is well below the flow conditions at the 500 psig-set point.

Scenario 7 - PCV Failure During Steady SCM When the PCV fails open,.the RHR system pressure will rise.

The increase in the RHR system pressure has the following consequences.. First, the condensation rate in the RHR will increase (primarily due to thel increased temperature difference between the steam and the tube surface).

This will cause the water. level in the 101R heat exchanger to rise which in turn will-cause'the level control valve to open as it attempts to keep the level in the RHR' heat exchanger at the_ set point.

However, this level control valve must also keep the pressure to the RCIC pump' suction below 45 psig.

Therefore, the level control valve will move to a position where it is able to maintain both.the level in the RHR heat exchanger at the set point and maintain RCIC suction pressure below.45-psig.

If this is.notipossible, the level control valve will maintain RCIC suction at or below 45 psig in which case the~1evel in the RHR heat exchanger will increase.

It may not/be possible to know'whether the leve1' control i

valve will~be.able to' maintain RHR heat' exchanger level

-following a' failed-open PCV.

.Therefore, both of the above discussed posribilities were examined.

The'first case-considered lis where the level' control valve is.ableito

. maintain the RHR heat; exchanger level at the" set point..

At the' time _the:PCV failsiopen,' the condensation' rate is.

~ he normal 1 condensation rate for the steady SCM.

TheLfailed-t i

open PCV--willipass<more flowithan can'befcondensed by the

~RHR' heat exchanger. 'Therefore,fthe RHR: system _ pressure lwillEincrease.~,At some: point ini time the:RHR_ system pressure'.

~

,will'reachithe.setopoint for.the SRV'. The-netiflow-through=

the'SRV will bentheEdifference~between the flow through f

-the' failed-open PCVyand1the2 condensation rate.

Since-the:

iSRV has.a! higher ~ flow capability:than the PCV, thisLimplies:

that'the^SRV will cycle..

~

g W

[g g;

The second case considered is where the level control valve is unable to control the water level in the RHR heat exchanger.

This condition results in the RHR heat exchanger water level rising and hence reduces the tube sheet area exposed to steam.

It is estimated that the 3 to 4 ft. of exposed tube sheet during normal SCM cperation will be covered between 1 and 5 minutes depending on the condensation rate assumed in the RHR heat exchanger.

Once the tube sheet is completely covered the entire steam flow through the PCV is discharged via the SRV into the suppression pool at a high mass flux.

Therefore,-in this scenario, the steam mass flux discharged into the pool can vary from a low value (if the RHR heat exchanger condensation rate is high) to a high value (corresponding to the PCV flow) if the tube sheet is covered.

Scenario 8 - SRV Leaking During Steady SCM Steam leakage through the SRV when in the SCM results in a steam flow which gradually pressurizes the discharge line.

The water and air normally in the line are forced out.

While the time required to pressurize and clear the discharge line is dependent on the' leakage rate through the SRV, the air and water clearing loads that could be generated by this scenario are bounded by the worst-case loads.

After the water and air have been cleared out of the discharge line, the leaking steam will start condensing in the suppres-sion pool.

Both condensation oscillation loads are expected to result depending on the steam leakage rate through the RHR/SRV and the steam condensation rate in the RHR relief line.

Scenario 9 - PCV and SRV Failure During Steady SCM The final scenario that can be postulated during steady SCM operation is the one where there is a simultaneous failure of both the PCV and the SRV.

Such a double failure exceeds the single failure criteria.

In any case, the water and air clearing loads as well as the condensation loads for this scenario are bounded by the worst-case loads.

8-5

. Items'8.2'and 8.4

~

The-RHR heat exchanger relief valve discharge lines at Clinton mayl experience.some reflooding due'to the possibility of subsequent.or cyclic actuations of the RHR/SRVs.

(The RHR/SRV was sized larger than the upstream PCV).

Reflood of the RHR system SRV discharge'line following the plant

-normal firstractuation of the RHR/SRV was calculated using the.reflood prediction code RVRIZ02.

The maximum amount of reflood.for Clinton's RHR systgm occurs when the suppression

. pool temperature is low - ( ~ - 77 F). -The reflood~ height pre-dicted by RVRIZO2.is 12.95-ft. above the submerged end of the~RHR/SRV discharge line.

Since the vacuum breakers are located more than 15.33 ft. above the end of the RHR/SRV-discharge line, reflood to the vacuum breakers is not' expected after.SIOT actuation for normal plant design conditions.

Examination of reflood conditions based on scenarios involving an inadvertent upper. pool dump, followed by a.RHR system failure,;resulting in actuation of the RHR. safety relief valve, have not been considered.

Such a double failure-exceeds the single failure criteria.

Item 8.3 The subsequent actuation-RHR/SRV loads described in Action Plans'6.and 8, were based upon a'reflood' height-in the-RHR/SRV discharge'line of 12'.'95 ft.

Air bubble loads based upon a first actuation of.the'RHR/SRV.are smaller in magnitude'than the RHR/SRV subsequent actuation air-clearing loads.

Since both~of these loads-have~approximately'the.same frequency, only the_RHR/SRV subsequent. actuation air-clearing loads on submerged structures'and-the suppression pool boundary were analyzed (see Action _ Plan 6).

Water jet loads resulting from actuation of. the RHR/SRV do not impact any submerged structure in the Clinton-

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suppression' pool and'are therefore:were not considered.-

l-Item 8.5

-Inadvertent initiation of an upper' pool: dump.for Clinton-

.would. require multiple, non-related single; active ~ failures in plant = equipment or' remote manual opening of'one of the poolLdump valves plus a'singlefactive failure in plant equip-ment ' (see CPS-FSAR Section 6'. 2. 7. 3. 3).

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Simultaneousisignals1 indicating a low-low water level:(LLWL)

"in the suppression ' pool and a loss-of-coolant _. accident. (LOCA)?

are r,equire'd for'an. automatic upper. pool dump.

Since an upperypool: dump Ecauses' the ' suppression' pool water level to

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increase two" feet and!the LLWL isltwo feet below the sup.

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pression pool, normal /high water level (HWL),J the ; effect. of:

-an' automatic upper pool. dump'is7 simply to restore:a normal /

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high'waterElevel in the suppression-pool.

Back7pressuresJin.

.the dischargeHline'resulting from;RHR/SRV actuation'foll' wing.

o fan automaticEupper pool? dump!are no-worsecthan:those' occurring E :

with ::the -. suppression; pooli at; HWLi

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Examination of scenarios involving an inadvertant pool dump, followed by a RHR system failure, resulting in actuation of the RHR safety relief valve, have not been considered.

Such a double failure exceeds the single' failure criteria.

A detailed discussion of the RHR heat exchanger peak pressure and overpressure allowables is not warranted.

The maximum normal operating condition for the RHR heat exchanger in the SCM is 200 psig.

The design basis for the RHR heat exchanger and the set point of the RHR/SRV are both 500 psig.

Both shell and tube sides of the RHR heat exchanger have been hydrostatically tested to 750 psig (per ASME Section III requirements).

This is adequate design margin in the RHR heat exchanger's construction.

8-7

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. Action Plan 21 5.5' Equipment may be-exposed to local conditions which exceed environmental qualification envelope as a result of direct drywell-to-containment bypass leakage.

Response

An assessment was made to determine which equipment is located near any.drywell penetration.

The only equipment located near any drywell penetration is instrument panel 1H22-P0ll located on elevation 778'0" in area 1 of the containment.

A 3.5" 0 sleeve (conduit) designated for. lighting / communications is located approximately 4 feet from the nearest instrument on this panel.

The construction of this penetration will be such that any leakage flow-through the 5-foot thick concrete wall will be prevented from direct impingement on panel 1H22-P011.

Any leakage would then rise as it entered the containment due to buoyangy.

The qualification temperature for panel 1H22-P011 is 265 F, which is conservative enough to account for any local temperature increase due to bypass leakage.

Thus, instruments on panel lH22-P011 will not be affected by this direct drywell-to-containment bypass leakage.

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Figure 8.1.

Schematic of Clinton R!!R !! cat Exchanger-

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8-8