ML19317G700

Operating Methods to Eliminate Any Potential for Unacceptable High Boric Acid Concentrations During Long-Term Cooling

ML19317G700
Person / Time
Site:	Rancho Seco
Issue date:	04/21/1975
From:	SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:
References
NUDOCS 8003260831
Download: ML19317G700 (35)

Text

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.nw wn1 THE AT ! ACHED FILES ARE OFFICI AL RECORDS OF THE OFFICE OF REGUL ATION. THEY H AVE BEEN CH ARGED TO YOU FOR A LIMITED TIME PERIOD ANS MUST BE RETURNED TO THE CENTR AL RECORDS STATION 008. ANY P AGE (S)

REMOVED POR REPRODUCTION MUST BE RETURNED TO ITS/THEIR ORIGIN AL ORDER.

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MARY J NKS. CHIEF I

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ATTACHMENT 1-

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Revised h/21/75 e

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OPERATING !!ETHODS TO ELIMINATE ANY PO*ENTIAL FOR UNACCEPTABLE HIGH BORIC ACID CONCENTRATIOUS DURING LOUC TERM COOLING p

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General The method of operation to be used in long term cooling to eliminate any potential for unacceptably high boric acid concentrations in the core region is listed below.

1. ~ If both Lov Pressure Injection (LPI) strings are operable, try to establish suction from the reactor vessel outlet pipe through the decay heat (DH) drop This will force the LPI string flow to flow through 11ne'vith one LPI string.

the core.

2.

If step one is not successful, open the DH drop line to the LPI string used in step one to establish gravity draining frcm the hot leg.to the reactor building energency su=p.

This vill pull injection flow through the core at a rate equal to the~ drain flow rate.

3 If step two is not successful, open the aux 111ary spray to the pressurizer.

This vill route dilute injection to the area above the core.

The flow path is through the auxiliary spray line into the pressurizer, out of the pressurizer through the surge line into the hot leg and then into the reactor vessel.

The flow paths for these steps and any necessary modifications are shown on Figure 1.

Valve numbers shown en Figure 1 are aribtrary numbers for identification purposes and do not correspond to any actual numbering system.

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For step one, the flow path is from the hot leg t'hrough valves V12, V13. V5A (or V5B), V9A (or V93), V10A (or V103), V6A (or V6B), V8A (or V83), and into the reactor ve.ssel through the core flood tank nozzle.

l The flow path for step two is from the hot leg down through the DH drop line (valves V12. V13 and V5A or V5B) into the sump-BWST header and backwards through the sump outlet.line (valve VLA or V5B) and into the sump. Scme means.must be provided to determine whether or not flov exists in the DH drop line. A temperature sensor is to be added to.the DH drop line to detect the presence of flow for step two.

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DE drop line is located in the auxiliary building with a normal temperature of less I

than 100 F.

If flow exists in step two, the temperature.at the sensor vill increase.

l The increase could'be to a temperature as high as 212 F if the LOCA is a cold les i

break.

. For step three, an HPI pump would-be placed in operation taking stiction from an' cperating LPI' string.through the " piggy back" cross connect (valve V7A or V7B).

The flow path to the hot les vill be through the auxiliary pressurizer spray line criginating frcn the HPI line which is through valve V15A, the block orifice, and V17 into the pressurizer and out the surge line into the hot leg.

Changes are required to make.this a ;.rorkable flow path as there are manually operated valves inside the reactor building which must be opened and closed during the long term cooling period to establish this flow path.

Change:s required are shown on Figure 1

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'and are:.(1) add an electric motor operator (EMO) to valv'e V17, (2) add an EMO to the stop check valve located downstream of VISA.or add an EMO stop valve (V30 on

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Figure 1) in the HPI line.

Valve V30 musti remain open during normal operation to ma'intain the HPI flow path.

Valve V30 must be closed for step three to prevent the flow from diverting to.the HPI line. Valve V17 must remain closed during normal operatiod to prevent diversion of HPI flow to the pressurizer.

Valves V17 and V30 vill be placed in their' nor=al operating positions and then their respective breakers will be locked open and tagged. The flow rate for this path to the hot leg is con-trolled and limited to LO GPM by the block orifice upstream of valve V17 II. Single Failure Analysis The three st'eps are necessary because of single failure criteria. Operations must-Le designed for a single failure in either the short ters or long. ter= cooling period but not a single failure in the short ters and then another single failure

, in the long tern period.

Since the operator may not be able to determine the location of the break, step one is attempted first (if both LPI strings are operable) to determine if the normal DH removal path can be established.

It can be established if the break location is high

,enough in elevation so that the DH suction no::le on the hot leg is sufficiently flooded to prevent gas or steam entrainment at the LPI pu=p flow rate.

Even if there is no single failure during the attempt, success is not ensured because of possibility

.of gas or steam entrairenent in the DH suction nossle.

If step one fails because LPI pump flow is erratic or loses pri=e, then step t.vo is attempted. A te=perature sensor in the DH drop line vill indicate success.or failure.

Step two could fail if one of the,two valves (V12 or V13) fails to open.

If step two fails due to single failure,

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then step three is perfor=ed. The above was for a single failure in the long term.

The single failure could occur in the short term with the single failure being suci that only one LPI string is operable. Step one then cannot be atte=pted because pri=e c.ould be lost on the only LPI pu p operating.

So, Step.two would then be performed.

III. Equirnent Qualification All valves located within the reactor building, that must be operated in any of the three steps, are electric motor operated and located outside of the secondary shield

.vall.

All of these valve EMO's are qualified for the LOCA environment and all EMO's to be added vill be qualified Ef0's.

If power is not available to any of the EM0's requir@

to implement any of the three steps, electrical jumper cables vill be used to connect

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power to the EMO controller.

IV. Operating Procedures for Long Term Cooling Operating procedures for long teen cooling wi11 be modified to include the procedures described in detail below following completion of system changes described above.

Th'e ECCS systems vill be placed in one of the fo$ loving three operating codes within 40 days after the accident.

Injection flov to the RC syste=s should be maintained throu6h two paths while attempting to place the systems in one of the three operating modes. The' two injection flow paths can be either the two LP injection lines. or one LP injection line combined with one EFI string (LPI pump acting as booster pu=p for KPI pump).

Mode 1 - Attemet to Establish Suction fran Hot Leg with One LPI String a.

This mode vill only be attempted if both LPI ' trings are operable.

If successful, s

it is indicative that the RC system is filled to above the. hot leg elevation.

Assume LPI string A to be used for the attempt.

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Open DH drop line EMO valves V12 and V13.

c.

Ensure that cross. connect valves between LPI strings A and B are closed (DD valves V11A and V113).

" 4.

Place LPI string B in " piggy back" mode with one HPI string to ensure injection flow through two paths. HPI D'.0 control valves V15C and V15D used to control EPI flow to 500 GPM and LEI Dio control valve V6B used to control LPI pump flov to 3000,GPM.

LPI pu=p flov is the sum of LPI'line B flow rate and the HPI string flow rate.

Shut off the LPI pu=p in string A and the building spray pu=p connected to the e.

same suction line.

f.

Close.LPI string A EMO control valve V6A.

Close sump outlet EMO valve V4A.

Open manual valve VSA in the DH drop line.

' g.

Start LPI pump in string A and clowly increase flow using EMO control valve V6A. Observe pump flow indication and pu=p noise for sy=ptoms of cavitation and entrainment of vapor or gas. LPI pump in string A is now taking suction from the hot les only.

h. 'The HPI pump taking suction fron LPI string;B may now be shut off.

LPI string A is now taking suction frem the hot leg and pu= ping to the reactor vessel and LPI string B is,taking suction from the RB sump and pu= ping to.the reactor vessel.

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An additional step may be taken, when convenient, to determine if the break location is high enough in elevation to cperate only one LPI string with the suction being frca the hot leg.

Slowly decrease the flow, rate in'LPI string 3 and then shut off the LPI pu=p in string B; continuously observe LPI string A indicated flow rate for erratic behavior.

Coolant from the su=p is not being i

pumped to the reactor vessel nov; i.e., not'providing an overflow out the break.

If suction to LPI pump A is not lost, it is indicative that:

(1) the RC syste=

is filled,to above the hot leg elevation, (2) the break in the RC system is above 4'

this elevation, and (3) the LPI string A injection line is intact.

LPI string B may now be placed back'in operation (taking suction frca sump) or operated periodically to make up for volume contraction as LPI string A reduces the reactor coolant te=perature.

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Mode 2 - Onen the DH Dron Line to the RV Su=2 If !! ode 1 is not successful, =aintain injection flov to reactor vessel through a.

two injection flow paths by any of the following:.

(1) Orie LPI pump operating with LPI discharge cross connect open (EMO valves V11A and V113) and the flow selit between the two injection lines by throttling EMO valves V8A and'V8B.

(2) One LPI string in " piggy back"'vith one HPI string.

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LPIstrin6Aissh'utdownfromtheunsuccess5ulMode1atte=pt. Valves V12, V13 and V5A are open.

Close valve V6A (LPI control valve).

Close sump outlet E*O valve VhA. The temperature measurement in the DH drop line vill be used to determine whether the drop'line is draining b'? gravity to the sump'or not, because it is possible that a valve in the flow path is not actually open.

The indicated temperature should change if gravity draining exists. Note the DH drop line indicated temperature and then open su=p outlet E!D valve VhA.

A change or a fluctuation in the indicated temperature is an indication of flow.

If Mode 1 was not attenpted because both LPI strings were not operable, then the initial temperature indication vill be lo r (auxiliary building ambient temperature) and gravity draining frca the hot leg vill significantly increase the indicated temperature.

If Mode 1 was atte=pted and not successful, but coolant from the hot leg reached the temperature sensor, then the' initial temperature indication could be high when the gravity drain is attempted.

If this has occurred and if when gravity draining is attempted, the indicated temperature does not change, then the following should be done.

(1) Lineup a flow path from the operating LPI string (String B) through the cross connect into LPI String A, backvards in String A, through the recirculation line around LPI Pu=p A and buckwards through the DH drop line.to establish a different indicated temperature in the drop line.

Decay heat drop line' valves V12, V12 and V5A and su=p outlet valve VhA are still open.

(2)

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If the cross connect (D40 valves V11A & B)'is not open between the two LPI lines, open it.

Close LP injection EMO valve.V8A if this injection line is not being used for injection to the reactor vessel.

(3) Close sump outlet EMO valve VhA. This has nov established a back-flow path through the DH drop at a flow rate of approximately 70 gpm.

(4) When the cool discharge fluid from the DH cooler establishes a new indicated temperature in the DH drop line, open sump outlet DD valve V4A to re-establish the gravity drain flow path frcm the hot leg to the

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sump. A change in indicated DH drop line temperature confirms the exis-tence of gravity draining.

c.-

Maintain injection flow to reactor vessel.through two injection flow paths per

,. Item a. above.

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Mode 3 - Quen Auxiliary Soray Line to Pressurizer a.

This operating mode vill be used if Mode 2 is not successful.

b.

• Close main pressurizer spray line DO valve V1 or V2 or both.

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c.

Line,up an HPI pump to pump through HPI String A taking suction from an operating LPI string through a " piggy back" cross connect (EMO valve VTA or V73).

d.

Close HPI EMO control valve V15A. Position HPI EMO control valve V153 as neessary to control HPI pump flow rate and start the HPI pump.

c.

Unlock and close the breakers for EMO valves V17 and V30.

Close EMO valve V30 and open EMO valve V17 Open HPI EMO control' valve V15A.. Auxiliary spray flow rate indi'cated by the HPI flow measurement upstream of valve V15A.

V.

Procedures to be Effected Prenntly The three operr. ting = odes, described in Section [V above, for long term cooling cannot be effected promptly, in entirety.

Mode 2, gravity draining of the hot leg to the sump, cannot be implemented until the temperature =casurement in the DH drop line or another means of flow detection is installed.

Mode 3, auxiliary spray to the hot leg, tannot be implemented until EM0's are added to valves located inside the reactor building.

Procedures whic,h vill be impleme + e4 now are:

. G.

If both LPI strings are operable, atte=pt to establish suction from hot leg th-ough DH drop line with one LPI string per Mode 1 of Section IV,~ above.

r-b.

If Mode 1 is not successful, establish reverse' flow through the DH drop line into

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the hot 1eg using the cross connect between the LPI straings and the recirculation line a.ound the LPI pu=p per item b of Mode 2, in Section IV, above.

This flow P th E

will produce apuroximately 70 gra of flow into.the hot leg..

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LONC TEI'Jt C001,ING - BOI:ON C0!! CENTRATION ANALYSIS 1

- _IlfrRODUCTION I.

s This section describes the 'rcactor system circulation and boron concentration condicions during post-LOCA long term cooling.

Large and small breaks of reactor inlet and ' outlet pipes are considered and the large break of u reactor vessel inlet pipe is shown to be the limiting condition.

The analysis demonstrates that natural circulation within the reactor vessel, where the flow path is downecmcr-core-upper head-vent valves-downcomer, pro-v' ides adequate circulation to prevent rapid increases in solute concentrations, including the limiting case.

The resulting slow concentration buildup indicates that a time period in excess of 30 days is available for alignment and operation of' alternate flow paths.

The recommended procedure is to establish flow through the decay Seat drop line within one day after the postulated LOCA (Operating Modes 1 and 2 of Section IV in Attachment 1).

This procedure will limit con-i.?ntration buildup to a factor of two (2) or less.

In the event the decay heat drop line is not available, the reccmmended pro-cedure is alignment and operation of the auxiliary pressurizer spray syster$

(Operating Mode 3 of Section IV in Attachment 1).

The auxiliary pressurizer t

. spray will act as hot leg injection; first as a dilutant for core wa:er and then, reversing the direction of core flow, and providing long term sensible heat removal. The concentiation buildup race decreases as auxiliary pressurizer i

spray becomes effective and the concentration gradually decreases as scesibac heat removal proceeds.

The recommended minimum auxiliary spray capacity is 40

~ spm. This auxiliary spray rate, if required, is expected to limit concentration buildup to C/Co = 11.

II.

SLMtARY OF REST.'LTS The recommended operating procedures to minimize boron concentration follouing a LOCA are, in order of preference:

3 a.

Always maintain a minimum of 3000 GMt LPI injection into the downcomer.

This provides for a natural circulation flow path within the reactor vcucci

.and the maximum concentration buildup is C/Co=1.19 for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after a L'OCA.

(Co is initial concentration - 2200 ppm boron solution).

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Within 24 hrurc -

.cr the LOCA, align ' decay heat

'cp line in a low flow mode which provides a minimen core flow

• of 500 gpm.

This.is call'cd a forced circulation mode,and if successful will provide a maxi-mum concentration ratio of 1.3 'throughout the long term cooling period' as shown in Fige 5.

In addition; if this operating mLde is successful and operation procccds to the normal dceny heat system flow rate, the forced core flow.is 3000

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gym minimum resulting in even lower concentration ratios (maximum value

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of 1.19) as shown in Figure 5.

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c.

In the event that the decay heat drop line is not operational (Single Failure), the au::111ary pressurizer spray flow is aligned to provide 40 gpm minimum flow vithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> af ter the LOCA. This mode is called hot leg injection and limits the concentration ratio to 11.0 at 60 days as shown in Figure 5.

If larger reverse flow rates are available, the maximum concentration ratio will be less than 11.

For example, an injection rata of 140 gpm will limit the concentration ratio to 1.9 at 7 days as shown in Figure 5.

III. DISCUSSION OF ANALYSIS III.1 Reactor Inlet - Large Break

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The reactor vessel internal natural circulation flow paths are shown l

in Figure 1.

In this circulation mode, driving head for the core flow is pro-vided by the downcomer fluid.

The downcomer head is sufficient to premote

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significant core flow and to provide adeq'uate pressure differential to open the v.(

vent valves.

The core flow rate'as a function of time is shown in Figure 2.

This flow rate from the core and through the vent valves is assumed to mix with the injection flow (3000 gpm) and exit from the vessel through the inlet break.

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For concentration calculations, however, the concentration entering the core is conservatively assumed to be equal to that leaving 'the core at a given time step.

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(In offect, nn baran to assumed to 1 cave tha. veasci thrcuch the break'.)

The resulting concentration ratio of boron as a function of time.is shown in Figurc 3.

The resultant natural circulation flow is such that very low quality secam is produced which produces relatively low concentrating rates. The rate of

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' concentration is such that alignment of an alternate flos path is not required for a time period in excess of one month.

However, in or'dcr to provide measura51e assurance that baron concen-tration is minimized, alignment of the decay heat drop line is recommended within 'one day af ter the postulated LOCA.

The flow paths in the reactor vessc1 in.this flow mode, called " forced circulation", is shown in Figure 4.

The 11miting. core flow in this " forced circulation" mode, assuding no density gradi-eut in the core is approximately 118 lb/see which is more than adequate to pro-vide decay heat removal without evapor'ation at one day.-

Figure 5 shows the bcron s oncentration change and peak value following alignment of the decay heat drop line af ter one day of natural circulation operation.

In the event that the decay heat drop line is not operational (failure of isolation valve to open), the alternate system to promote low boron concen-tration and to dilute the boron concentration is alignment of the auxiliary pressurizer spray.

The flow paths for this mode of operation (defined as " hot leg injection") are shown in Figure 6.

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Bot leg injection has little effect on circulation and concentration.

until the steaming rate, assuming evaporation only from the core, is equal. to or less than the hot icg injection rate.

As the injection rate approaches the

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steaming rate the hot leg injection acts to reduce the rate of core baron con-l 1

centration'by adding non-concentrated water. inventory.

As the decay heat de-creases with eime; the hot leg injection becomes adequate to remove decay heat by sensible heat removal.

The core flow direction reverses, and concentration

.of boron in the core becomes dilute with time.

The concentration with time for

" hot leg injection" are shown in Figure 5, for an injection rate of 40 gpm start-ing one day after a LOCA.

Figure 7 shows the model used for calculating the concentration af ter

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the decay heat letdown line is opened or af ter the pressurizer spray injection

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is initiated.

The concentration, C, is given, by 4

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, Hans Soi.ote Mass Solvent W C ft C = Mcci + I" ti in inde ti W Cdt out I

g H

or inde-h* W

+

W C

C/C,=

out C_ de EQ. 1 in o

Mc C,

M, C,

Where Ci is the concentration at t1 ti is time of vent valve opening or spray initiation Co is the reference concentration Equation 1 is used to calculate the concentration ratio after the natural circulation phase of the transient is teminated.

The important assumptions used for this part of the transient are:

(1)

Constant mixing mass, Mc = 30000 LBM.

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(2) 40 gpm flow rate from pressurizer sprays.

(3)

Constant LPI injection rate and concentration.

(4)

No density gradients in calculation of forced circulation.

(5) 1000 BTU /Lmi needed to produce steam.

(6)

Maximum flow out break for letdown line case.

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(7)

K-factors based on full flow values.

Sunnsr'y:

Reactor Inlet - Large Break The results of the calculations are shovn in Figure 5.

Tliey shou that the concentration ratio limit for the forced circulation modo is 1.19 at one day; the concentration ratio limit for the hot leg injection case is 11.0 at 60 days.

The solubility curves show that a concentration ratio of 30:1 is needed before precipitation will occur.

Thus, the proposed methods for con-trolling concentration buildup in the long term cooling phase of a LOCA at c more than adequate.

This is particularly true when the conservatisms inherent in the analysin are considered. These conservati::ms include:.

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(1)

N3 dilutic'n of injecticn !! 0 is censidered.

2 (2)

. Absorption of boric acid by concrete is neg1ceted.

(3)

Volatility of boric acid was ncalected.

I' III.2' Pump Suction - Larce Ercak

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For large breaks po: ulated at or in the pump suction line, the flow paths are as shown on Figure 8.

In this case the leak fluid must pass through ti a RC pump which is some 3-1/2 f t above the conterline of the RC pump.

This condition provides increased downcomer driving head for core flow chich results in more core flow and a lower outlet quality and boron concentrction when operating with LPI injection " Natural Circulation Mode.". In this case, the core flow versus time will be equal to or greater than that shown in Figure 3.

Operations in the forced circulation r. ode will produce flow patterns equivalent to that shown in Figure 9, with a near constant minimum flow rate of approximately 118 lb/sec.

This flow rate is more than adequate to provide decay heat removal without evaporation after one day.

Switch over to this mode will provide a concentration ratio equal to or less than that shown in Figure S.

In tSc event the decay heat drop line is not operational, the alternate system, i.e. pressurizer spray, dilutes the boron concentration as described in Section III.1 above.

The hot leg injection flow paths are shown in Figure 10, and the concentration ratio versus time is equal to or less than that shown in Figure 5.

III.3 Reactor Outlet - Larne Break In the case of a postulated large break, the flow paths are as shown in Figure 11.

Any parallel alignment such as opening tiic decay heat drop line, 4[

or hot leg injection, will produce little or not effcet.

This case corresponds to the forced circulation cold leg break with the decay heat drop line open, "except that all injection water flows through the core.

The min'imum core flow with one LPI pump operating is expected to be 3000 gpm (416 lb/sec) which will prevent boiling and concentration within 1-1/2 hours following a LOCA.

The resulting concentration ratio, then will be sig'nificantly less than that shown

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in Figurc 5.

III.4 Reactor Outlet - Top of ISO nend - Large Ercak In the case of a postulated large brea:c at the top of the 180 Bend, reactor outIci, the overall flow paths are as shown in Figure 12.

With one i

LPI injection pump assumed operating, thi injection flow will split approximately (5)

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30/50 hetween tha c.Jo and accam generatsra until t.. steam generator ecored

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heat in rcr:c.ved (approximately one day).

During this period'the flow paths within the vensc1 are approximately those of forced circulation.

The cor-

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respondina core flow rates are equal to or greater than (approximately 200 lb/

see) those shown in Figure 2, because of increased driving head. Af ter steam generator stored heat has been removed, the flow paths within the vecsci arc also those of forced circulation, where the stcan generator fluid acts as an

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extended downcomer, forcing all injection flow through the core.

'1he minimum y

core flow in this condition is 416 lb/sec.

Af ter one day with the decay heat drop line opened, the flow paths become those shown in Figure 11 with no change in core flow or concentrating effcet.

If the decay heat drop line is not operational, and the alternate auxiliary pressuri:cr spray system is used, the flow paths remain as forced

' circulation.

Core flov and concentrating effects do not change, since the auxiliary spray' flow is swept up the hot leg pipe along with the reactor out-let flow.

III.5 small Breaks III.S.1 - General Cencrally, small breaks are categorized' as those with break areas less than 0.5 ft To avoid excessive. concentrations of borie acid, the operator would take the same actions as those specified for large breaks.

For very c=all breaks where the system depressurization is slow and the system pressure re-maining at pressures over the design pressure of the decay heat removal system, the operator must wait until the pressure f alls below this point or take action to depressurize the system by using normal ~ cooldown procedures.

b Prior to taking any action, the system is being depressurized by losing.

, energy out of the break and the cooling provided by the high pressure injection

' system.

The pressure will remain up until the. loss of energy is greater than that being added from the core and that being released from the reactor coolant system metal.

The core decay heat is by far the predominate contributor of heat during a slow depressurization. IIowever, the reactor coolant system will not experience an indefinite time of pressures remaining at hii;h icvels for 2

breaks even as small as that equivalent to a 1 inch diameter break (0.0054 54 f t ),

For this 1 inch break, the pressure has been calculated to be Icss than 400 psia j

in 2 hourn and decreasing.

At this pressure, the flow from one HPI pump delivers more than twice that being lost out.the break.

The injection flow from onc UPI 4

(6) 4 I

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.,'., p...'..i.'.'

e pu;p 10 greater the.

the leak flow even when.the pt.,,sure in 1200 psia.,'. Thin -

will force natural circulation throughout the system and. prevent concentration of boric acid.

If both IIPI pumps were operating, deprescurization should occur I '

faster initially but the pressure would tend to stabill:e or even increase as the syst'em again became filled with water.

At this point, the operator could shut a pusp off and go into a " normal" cooldown mode.

For a break four times larger (2" I.D.), the system pressure would be R

below 400 psia within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 300 psia within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> if no operator action were taken.

Even for this size break, the injection flow from 2 IIPI pumps is greater than the leak flow when the system pressure is 400 psia.' This would result tu the RCS eventually refilling and could occur before the borated water storage tank empties.

Prior to the system refilling, the high pressure injection flow will generate sufficient driving head in the reactor vessel downcomer annulus and steam generators' to cause natural circulation through the core and the internals vent valves.

This by itself would' prevent excessive buildup of boric acid concentrations.

After the reactor coolant system has depressurized to allow LPI system operation, the various flow paths and concentration effects are described in the following sections (III.5.2 and III.S.3).

~

111.5.2 - Small Breaks - Cold Leg 7

Assuming a small cold leg break equal to the.LPI injection flow (3000 gpm), the flow patterns are the same as those shown in Figure 1 for injecticn flow (i.e., the natural circulation mode).

Switching to the decay heat drop line wi1L produce flow patterns similar to that of Figure 4, and in the event hot leg injection is required, flow patterns will be produced similar to those of Figure 6.

The corresponding concentration changes will be equal to or 1 css than those of Figure 5; Breaks smaller than the injection ratie will permit the water level to rise within the reactor coolant system, thereby providing additional driving head for the natural circulation path ed. thin the vessel, and reducing the con-centration rate because less evaporation occurs.

111.5.3 Small Breaks - Ilot Leg Assuming a hot 1cc break with flow rate equivalent to the injection flow rate, the ' flow. patterns will be similar to those of rigure 11.

nc hot icg breaks will pernit the injection flow to pass through the core (417 Ln/sec) and remove decay 'l$eut without cynporation uithin one hour af ter the break and con-(

centration 'is expected to tc minate af ter this time.

(7) t

e

..,.. ~ -.m.-

r.

Not 1cc bec

3. uma11tr than tha In.)cctica rate will permit "the watsr...

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i-

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7 FIGURE 5'.

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FIGURE 6 FLOW' PATHS-REACTOR INLET-LARGE BREAK

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. " HOT LEG INJECTION" 6

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g FIGURE 7 MODEL USED FOR CALCULATING CONCENTRATION AFTER NATURAL CIRCULATION PHASE W

s j i W

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• i FIGURE 8 FLOiv PATHS-PUi.iP SUCTION-LARGE BREAK

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.3 FIGURE 11

. FLOW PATHS - REACTOR OUTLET - LARGE BREAK

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FIGURE 12

~

HOT LEG BREAK TOP OF 180* BEND L'

4

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ATTACHMENT 3 D.5

. i.. LOSS OF' REALTOR COOLANT / REACTOR COOLANT SYSTEM PRESSURE

}

10 PURPOSE To prov'ide emergency procedures to be followed in the event of loss

.of reactor coolant and/or reactor coolant system pressure.

4

2.0 DESCRIPTION

This procedure is divided into three cases:

Case Description 1.

Small leak within capability of the makeup pump to maintain R.C. system pressure and pressurizer level 1

[%120 gpm, which is equivalent to 4 inches per minute in the makeup tank].

2.

Medium leak (such as a' Letdown Line or O'"SG Tube failure) wihtin capability, of the high pressure y

injection sys tem to maintain R.C. system pressure

-and pressurizer level.

)

3.

' Large rupture in excess of high pressure injection system. Requires evaluation for core flood line 1

break.

3.0 SYMPTOMS

.1 Pressurizer level and/or reactor coolant (RC) syst'em pressure de-creasing without associated decrease in coolant average temperature.

.2 Reactor trip, turbine trip and SFAS initiated.

Reactor building radiation levql, temperature, and/or pressure

.3 increasing.

1 i

.4 Reactor building (R.B.) accumulator tank level increasing.

{

.5

. Radiation monitor Alarm (s).

]

.6' Makeup (MU) tank Icvel decreasing.

~~ ]

D.5-1 Rev. 1

-1 l

- ' ':w z

t

.. H_

3.0 SYMPTOMS (Continued) y

.7 Possible annunciators:

~-

.1 RC Loop A Pressure Hi-Lo.

.2 RC Loop B Pressure Hi-Lo.

... 3

. RC Loop B Pressure Lo-Lo.

.4 R.B. Pressure Hi-Lo.

.5 hV Tank LVL Hi-Lo.

.6

,,PRZR LVL Hi-Lo.

.7 Radiation Monitor Alarms in R.B.

.S Immediate low level alarm on one core flood (C.F.) tank, 1

but not both, with one C.F. tank dropping level rapidly 2

(C.F. line break).

NOTE:

Coolant leak symptoms can be caused by a malfunction of the makeup system

,)

or a steam line rupture, as well as a loss of coolant.

The operator should assume the cause of the symptoms des-cribed above as a reactor coolant leak or rupture until the cause can be es-tablished.

^4.0 AUTOMATIC ACTIONS

.1 Reactor / Turbine Trip at 1900 psig coolant pressure or 4 psig building pressure.

'.2 SFAS initiation (High Pressure Injection (HPI), Low Pressure In-jection (LPI), R.B. Emergency Cooling, and R.B. Isolation) at 1600

'psig coolant pressure or 4 psig' building pressure.

.3 R.B.- spray at 30 psig building pressure (plus a 5 minute time delay).

.4 Pressurizer heaters cutoff at 40 inches.

]

~

D.5-2 Rev. 1 9

g

(',,.

~

~

5'.0 OPERATOR ACTIONS s

)

NOTE:

~

The following Sections 5.1, 5.2 and 5.3 contain Operator Actions for Cases 1, 2 and 3.

5.1 CASE 1 - SMALL. LEAK

.1~

IMMEDIATE OPERATOR ACTION

~

.1 Close the letdown isolation and R.C. pump seal return Valves.

.2 Reduce unit load as rapidly as possible in preparation for a normal shutdown.

.3 If the pressurizer icvel reaches <160 inches and/or makeup tank level reaches 18" manually initiate high y

pressure injection (SFAS Channels 1A and 1B] and trip the reacto-; then complete Case 2 Actions.

.2 SUBSEQUENT OPERATOR ACTION

.1 Notify Shift Supervisor, dispatcher and plant personnel.

.2 Maintain MU tank level by opening BWST outlet valve to the 1

operating MU pump suction, as required.

.3 Commence normal shutdown and cooldown per plant chut-down procedure B.4, if required by Tech Specs, Section 3.1.6.

.4 When plant conditions allow, isolate an"/or repair leak.

(-

Monitor gas and particulate activity and radiation levels to determine when safe entry in the contain-ment building can be made.

t-

)

D.'5-3 Rev. 1 l'

e

.x 7

e n~

x-520'

~ Operator Actions (Continued)

)

i.

5.2 ' CASE 2 - MEDIUM LEAK

.1.

DCfEDIATE OPERATOR ACTION

.1 Trip reactor -and initiat'e high pressure injection [SFAS Channels 1A and 1B].

S-

.2 ' Maintain pressurizer level on scale by varying number of HPI pumps.

y

.3 If RC pressure and/or pressurizer level continue to de-crease then complete CASE 3 Actions.

.2 SUBSEQUENT OPERATOR ACTION

.1 Notify Shif t Supervisor, dispatcher and plant personnel.

~

Verify SFAS Channel 1A and 1B equipment is operating.(Blue au

.2'

~

1

.3 Limit HPI pump flow between 500 and 40 gpm to prevent runout and deadhead..

.4 Perform Emergency Procedure D.3 for reactor trip.

.5 Establish 1 RCP running in each loop.

}

.6 Cooldown the RCS per OP B.4 as closely as possible.

Do not isolate core flood tanks or bypass SEAS.

'. 7 On BUST Lo-Lo level, shift HPI pumps suction from BUST I

to DH pump discharge and shif t. DH pump suction to R.B. sump (see OP A.8, Section 4.2),

.8 M:onitor reactor building for hydrogen.

Initiate c

hydrogen purge when hydrogen concentration reaches 3.5%.

Verify hydrogen purge blowers are operable.

.9 Monitor gas and particulate activity and radiation levels to determine when it is safe to send personnel into the reactor building to locate, isolate and/or

. repair the leak..

I s

1 D. 5-4 Rev. li

~

't.

'4' f

^ =-.

u

.... c-:.... c..; -

.. c..-

, a r.,, -

c

.s

5.0'

- Operator Actions (Continued)

)

.5.3. CASE 3 - LARGE RUPTURE

.1 1 IMMEDIATE OPERATOR ACTION

.1

.. Verify reactor tripped at 1900 psig','RCS pressure.

.2 Verify initiation of SFAS Channels.1 and 2 at 1600' l(

psig, and equipment operation.

'etermine if rupture is core flood line break by ob-

. 3.

D serving CF tank level and LPI flow.' -

NOTE:

\\

.-A'CF line break is evident, if one CF tank blows down immediately, but not both, and there is LPI flow to the effected CF nozzle and 0 LPI

.g flow, with RCS pressure greater than 240 psig, to the other loop.

For a CF line break, RCS pressure will re-main greater than 600 psig for approx-imately 2.5 minutes.-

)l

'.4 Verify injection from core flood tanks at 600 psig.

.5 SFAS Channels 3 and 4 actuated at 30'psig building pressure and spray flow is initiated subsequent to the 5 minute time delay.

.6 Deleted.

~

l

.2 SUBSEQUENT OPERATOR ACTION t

.1 Notify Shif t Supervisor, dispatcher a"nd plant personnel.

.2 Trip R.C. pumps.

.3 If a CF line break is suspected, vee 5.fy uneffected LPI pump is running and proper flow path from EWST to uneffected CF nozzle is established'.; then, close effected loop SFAS injection valve and stop the effected loop LPI pump.

NOTE:

If CF line break RCS pressure will remain greater than 240 psig'for approximately 7 minutes; 1.e.,

No LPI flow should exist in uneffected

'o) loop with RCS pressure >240 psig.

D.5-5 Rev. 1 l

]

r

> ' s.

~'

5.0~-

Operator Actions (Continued)

'5.3 CASE 3 - LARGE RUPTURE (Continued)

.4 If a CF line break is suspected and the uneffected LPI loop pump is not operating, establish LPI flow to the uneffected loop through crors connect valves, HV-26046 and HV-26047.

L.

.5 Limit HPI flow to 500 gpm per pump.

.6-Limit LPI flow to 3750 cpm per pump.

.7

' When the LPI system is injecting water in the core stop the auxiliary feedwater flow to prevent flooding the steam generators. HPI pumps may be stopped if 1 DH loop is injecting >l500 gpm.

.8 When the BWST reaches its Lo-Lo alarm point, shift in-jection and spray pumps suction to reactor building emergency sump (see OP A.8, Section 4.2) within 4 minutes.

.9 Monitor gas and particulate activity and radiation levels to determine if penetration areas and emergency 1

pump rooms are safe for personnel entry.

)

.10 Sample periodically the R.B. sump recirculation water for pH and boron,; maintain pH at 9.3 e:

NOTE:

One spray additive tank should provide a ph of 9.3.

The-second tank is avail-able for pH adjustments.

.11 As soon as prceticabic within 30 days establish dilu-tion flow to the reactor vessel to prevent boron pre-cipitation by the following method:

.1 If both HPI loops are operating attempt to establish recirculation flow through the core with one LPI loop as follows:

.1 Open the decay heat (DH) suction line valves from the reae. tor vessel (HV-20001 and HV-20002).

.2 Verit'y LPI loop cross connect valves are closed.

i 1

.3 Establish one HPI loop flow to the reactor t

taking suction from one LPI pump discharge -

per OP A.8, Section 4.2.

Control LPI loop total flow to 3000 gpm.

D.5-6' Rey, 1

v.

qu

.u r: 4..

1., _

t c.'.'

5.0.

. Operator. Actions (Continued)

~

-m

.)

5.3'

. CASE 3 - LARGE RUPTURE (Continued)

.4 Stop the LPI pump in the other loop and the R.B. spray pump connected to the same suc-tion line.

~

.5 Close the idle LPI loop flow control valve (SFV-26039/SFV-26040).

Close the PdB. sump outlet valve to the idle 'LPI string and open the manual suction valve to the idle LPI-pump (DHS-001'or DHS-002).

NOTE:

, 3

- If. radiation levels are excessive, shielding and/or reach rods may be

' required to open the manual valves.

.6 Start the idle LPI pump and slowly increase

_ flow with the flow control valve (SFV-26039 or SFV-26040).

Observe loop flow for indi-cation of pump cavitation.

fli

.7 If flow is confirmed, the operating EPI loop

.may-be terminated.

If the LPI pump cavitates, s

then attempt method

".2" below.

~

I' NOTE:'

j

~

Any minimum detectable flow is acceptable if verified by flow indication.

.2 If core recirculation method above was not successful, establish reverse flow through the DH suction line into the 36" RC hot leg and in-to the reactor vessel as follows:

.1 Establish 1 LPI loop injecting into the reactor vessel with 1 HPI loop operating, taking suction from the operating LPI pump discharge (see OP A.8, Section 4.2).

NOTE:-

This provides additional reliability, i.e., maintains 2 operating flow

.i

, ~

paths to the reactor.

~

D.5-7 Rev. 1 5

't 4

0 4

9

.=

m, -....

-m, m.

..,.., -, - /

-,_;v c.,

~

=

=m.-

~

,-Ff

• 6;,

=

~

- r.,, ~

+

t

,, s. e

, 5.0.

Operator Actions (Continued)

~

-(q 5.3' CASE 3 - LARGE RUPTURE (Continued)

.2 Close-the idle LPI loop valve to the reactor vessel (SFV-16005/26006) and its valve from the R.B. sump (HV-26106/26105), and stop the associated R.B. spray pump, if operating.

.3 Open HV-20001, HV20002 and the idle loop manual suction valve from the reactor (DES-001/DHS-002).

NOTE:

1 If radiation levels are excessive, shielding and/or reach rods may be required to open the manual valves.

. 4_

Open the LPI loop cross connect valves HV-26046 and HV-26047.

When opened, flow should be established from the operating DH pump discharge through the cross connect, through the. idle DH pump mini flow line,,

backwards through the idle pump suction line, and into the RCS 36" pipe to the' reactor vessel.

.12 Establish makeup water to the spray ponds from the Folsom South Canal or the site reservoir or the cire.

water canal.

If makeup is unavailable maintain the spray pond outlet temperature between 84 and 94*F by cycling NTN-041 (042) spray pond interlock valve as required (intermittent operation will reduce drif t losses, iaitiate spray at 94*F and terminate spray at 84'F).

i.

D.5-8 Rev. 1 d .}}