ML17309A667

Assessment of FPL Relief Request, Technical Evaluation Rept

ML17309A667
Person / Time
Site:	Saint Lucie
Issue date:	06/08/1988
From:	Greenstreet W OAK RIDGE NATIONAL LABORATORY
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ML17223B370	List: ML17309A667
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ENCLOSURE 2 Technical Evaluation Report Assessment of Florida Power And Light Relief Request Oak Ridge National Laboratory W. L. Greenstreet June 8, 1988

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ASSESSMENT OF FLORIDA POWER AND LIGHT RELIEF REQUEST

~Summar We do not agree that pumps can be meaningfully tested without measuring flow rate. Flow rates must be known to ensure acceptable pump performance and to detect degr adation. Without measuring flow in the low flow regime (especially in the region of miniflow for the pumps in question), it is not possible to determine what the flow rate is. It can even be zero!

The argument presented by Florida Power &, Light Company (FP&L) relative to the way in which pumps degrade is not technically supportable. The pumps under consideration tend to degrade by exhibiting signif icant performance degradation at relatively high flow rates, rather than uniformly, as indi-cated in FP&L's Fig. 1 of Ref. 1. Hence, the argument that pump degr ada-tion would result in a change in Delta P under miniflow conditions is also technically unsupportable, since substantial degradation in pump perform-ance can occur at high flow rates with no observable change in the low-flow end of the curve. (For an example of such degradation, see LER 87-003 for the Shearon Harris plant.)

Inability to detect degradation of the minimum flow path without measuring flow is recognized by FP&L. This inability in itself points out the impor-tance of having flow instr umentation in that .,path; most miniflow recirc paths for pumps, including those in the low pr essur e safety i nj ection (LPSI), high pressure safety injection (HPSI) and auxiliary feedwater (AFW) systems at St. Lucie Unit 2, incorporate an orifice and a check valve in series. It is important that these paths be unimpeded to prevent pump damage. For this reason, flow through miniflow lines should be periodi-cally monitored to demonstrate that proper pump protection is provided.

Because of these concerns, both flow rate measurement and the inservice (ISI) testing program at St. Lucie Unit 2 were addressed. The examinations conducted were based on system P&IDs, FSAR information, and relief request correspondence, as well as per sonal experience and judgment.

It was concluded that, in addition to the need for flow measuring devices, there are a number of valves not now included i n the IS I program that should be added. It must be emphasized that both pumps and flow paths should be subjected to regular examinations. In addition, the adequacies of the miniflow rates beir.g used need re-examination in light of current knowledge.

It is recommended that both miniflow and full flow testing of pumps be carried out. Miniflow testing is to be conducted quarterly for HPSI and monthly for AFW pumps. The HPSI and AFW pumps are to be full flow tested during refueling and cold shutdown outages, respectively. Full flow test-ing at quarterly intervals is recommended for LPSI and containment spray (CS) pumps. Boric acid (BA) makeup pumps are to be tested quarterly using existing level instrumentation. Diesel oil transf er (DOT) pump tests are to be performed quarterly using a selected path in which flow can be measured. Details associated with these recommendations are given in the following section.

Pum and S stem Test Re uirements HPSI It is agreed that quarterly full flow testing is not feasible, and could not be accomplished without major piping modifications. While Mode 5 (cold shutdown) testing at full flow can be done (taking some precau-tions) without, violating Tech Specs, it is not a recommended practice.

It is agreed that full flow testing should be conducted in Mode 6 (re-fueling).

Note that the HPSI miniflow line check valves are not included in the St. Lucie ISI program. The miniflow lines provide a critical function in St. Lucie's HPSI system, since it is a relatively low head system, and the Reactor Coolant System may remain above HPSI pump shutoff head for substantial periods following certain design basis accidents. For this reason, check valves V3102 and V3103 should be included in the ISI program (for forward flow delivery demonstration).

Since the pumps would be operating on the flat (high-head) portion of their curves when operating in recirculation conditions, pump delta p monitoring would not provide indication of flow. The only way to verify adequate flow and proper operation of the check valves is to measure re-circulation flow. The current revision of the Safety Injection Flow Diagram (2998-G-078, Rev. 2) indicates surface mounted flow elements (presumably ultrasonic,flowmeters), with low flow alarms, installed in the suction piping of both HPSI pumps (FE-03-3 and FE-03-4) as well as in the pump recirculation lines (FE-03-3-1 and FE-03"4" 1). These in-struments could be used to perform this periodic recirculation flow monitoring function.

Recommended actions:

a. Quarterly testing of each HPSI pump, using the installed suction and/or minimum flow line surface mounted flow elements.

b. Mode 6 full flow testing of each HPSI pump (which is not only needed to demonstrate pump capability, but forward flow stroking of various check valves as well).

c. Addition of check valves V3102 and V3103 to the ISI program.

LPSI It does not appear impractical to test LPSI on a quarterly basis. The LPSI pumps can be (and should be) tested at full flow through line 6-CS-500. Note that this is a nonnuclear safety class line (Quality Group D). This line currently does not have flow instrumentation. If flow instrumentation were added to this line, both the LPSI and containment spray pumps could be individually tested with the single flow element.

The path would allow testing in normal operation. Note that a similar full-flow recirculation line is used at other plants for quarterly full flow testing of similar pumps.

0 As in the case of HPSI, the minimun flow lines are critical to pump pro-tection. The current revision of the Safety I+ection Flow Diagram (2998-G-078, Rev. 2) indicates flow elements, with low flow alarms, in f

the minimum flow lines or the LPSI pumps (FE-03-1-1 and FE-03-2-1) .

These instruments could be used to perform this periodic recirculation flow monitoring function.

It should be noted that the minimun flow provided for the LPSI pumps is 100 gpm per .pump. For the same model pump (and used in the same

.service) at another plant, Ingersoll"Rand specified 500 gpm minimum flow for long duration, but allowed as little as 335 gpm for very limited periods.

Also note that the miniflow line check valves V3104 and V3105 are not included in St. Lucie's ISI program. The discussion included in the HP SI sect i on r el ati ve to the impor tance of mini flow check val ves i n providing pump protection following certain design basis accident events applies here as well.

Recommended actions:

a. Ins tal1ati on of a flow element in line 6-CS"500 for ful1 flow testing.

b. Testing each LPSI pump quarterly at full flow.

c. Simultaneous with each full flow test under b, moni tor flow through the miniflow flow path (to demonstrate pump protection and check valve stroking).

d. Further review of the design adequacy of the minimum flow line.

(Although not specifically ISI related).

e. Addition of check valves V3105 and V3104 to the ISI program.

AFW In general, the FPKL line of reasoning relative to pump testing is sup" portable. However, as in the cases of HPSI and LPSI, the miniflow lines must provide adequate recirculation flow for pump protection. The AFW discharge isolation valves (MV-09-09, -10, -11, and -12) open in response to an Auxiliary Feedwater Actuation Signal, but will still act as level control valves and cycle open/closed on low/high SG level.

While closed, the miniflow lines must provide adequate flow for pump protection.

The miniflow line check valves are not currently included in the St.

Lucie ISI program, and flow instrumentation for these lines does not exist. In order to provide periodic verification of adequate flow and proper operation of the miniflow check valves, a flow instrument should be installed in the common miniflow line.

An alternative, from the standpoint of the check valves, would be periodic disassembly and inspection. Note that while this would be

roughly equivalent from the standpoint of the check valves, it would not detect other potential problems, such as a mispositioned manual valve or degraded flow restricting orifice.

Another observation which is pertinent to the turbine driven AFW pump relates to the turbine steam supply check valves.

According to the St. Lucie ISI program, these valves (V-8130 and V"8163) are tested quarterly. Since the turbine is run in recirc only on a quarterly basis, i t is doubtf ul that these valves are fully opened quarterly. The required forward flow would be verified by periodically running the pump at full flow (to which St. Lucie has committed), so that is not a significant concern. It would appear that a relief request to identify the fact that the valves are only partially stroked open on a quarterly basis, but fully opened in conjunction with full flow testing of the pump, would be prudent.

A concern relative to the steam supply check valves which is significant is the fact that they cannot be reverse flow closure tested. For St.

Lucie, prevention of reverse flow is necessary for mitigation of such accidents as steamline and f eedline break. Without reverse flow closure, the closing of main steam and main feed isolation valves, as well as AFW discharge isolation valves to the faulted SG would still not isolate the break flow, since steam from the intact SG would continue to be dumped out of the break. This would increase the positive reactivity insertion of cooldown associated with a steam line break as well as in-cr ease the heat-up and pressurization of containment. It would also be a likely source of confusion for operators in that both SGs would appear to be faulted. Finally, turbine driven pump performance would be sub-stantially degraded.

Recommended actions:

a. Installation of a flow element in the common miniflow line.

b. Performance of monthly tests in recirc (NRC requires monthly, versus quarterly, tests for AFW pumps).

c. Full flow testing at each cold shutdown (Mode 5). Note that the tur bine driven pump would have to be tested in Mode 3 or 4 (hot standby or hot shutdown).

d. Addition of check valves V9303, V9304, and V9305 to the ISI program.,

Include verification of reverse flow closure (can probably best be performed by periodic disassembly and inspection) for AFW turbine steam supply valves V-8130 and V-8163 in the ISI program testing.

Boric Acid (BA) Makeu It would appear, contrary to FP8L contentions, that there are practical flow paths available for pump testing. There also appear to be a number

of inconsistencies in the pump/valve testing, as well as omission from the ISI program of some valves which are vital to pump delivery. Dis-cussions of the apparent inconsistencies and omissions pertinent to pump performance are given below.

Pum Testing St. Lucie states that BA Tank volume is insufficient for using level in-strumentation to monitor flow. This does not appear to be the case.

BA tank volume is 9975 gallons (each), per Table 9.3-6 of the FSAR.

Per Tech Spec 3.1.2.8, approximately 6100"6500 gallons are required in one tank to meet required operability. Thus, over 3000 gallons of excess capacity are available for addition/depletion during testing.

The system design is such that the BA pumps can pump from one tank to the other. By starting, for example, with the 2A tank at 8000 gallons and 2B at 6500 gallons, 1500 gallons could be transferred from the 2A tank to the 2B tank by the 2A pump. At least two alternative flow paths are available. Either existing tank level instrumentation or test in-strumentation could be used to determine volume change/unit time. Even at pump design flow (142 gpm), over 10 minutes transfer time would be available under the above scenario.

Recirculation Valves V2650 and V2651 These valves are shown as normally open valves which close on a Safety Irgection Actuation Signal (SIAS). These valves (and their lines) are large enough to allow fairly rapid mixing of the BA tanks during hatch-ing or to prevent stratification. These valves are not included in the ISI program, yet their closure is necessary in order to assure suf-ficient flow delivery from the BA pumps to the suction of the charging pum ps, Check Valves V2443 and V2444; FCV 2210Y The check valves are listed as being tested quarterly. However, the logical boric acid flowpath which would be used for partial forward flow demonstration would be through FCV 2210Y. This will blend the acid with make up water and preclude i+ection of concentrated boric acid into the charging flow path. (Check valve V2175, which is included in the 1>s.

of valves tested quarterly is also in this flowpath.) Yet there is a re-lief request for FCV 2210Y to only test at Cold Shutdown. While quarterly partial flow testing of the check valves could be performed, for instance, by blending and delivering flow to the RWT, this would in-volve opening FCV 2210Y. Thus, it is not clear how check valves V2443.

and V2444 are tested since St. Lucie doesn't want to open FCV 2210Y.

(In contrast, the r ationale for not testing FCV 2210Y would appear to preclude forward flow testing V2443 and V2444, if the logic were ex-tended.)

As for FCV 2210Y, which closes on a SIAS, full stroke testing could be readily performed without concern of overboration by closing valve

V2645. While this would temporarily disable the VCT auto makeup func-tion (which is not a Tech Spec required function and is infrequently in use), it would allow testing to be conducted on FCV 2210Y in accordance with code while having a minimal or no impact on operation.

It is interesting to consider that FP8L notes that failure of FCV 2210Y in the open position could result in injection of concentrated boric acid into the RCS which "could place the plant in an unsafe mode of operation." Since a safety injection does exactly the same thing, only at a higher rate, and through a different path, one might conclude from this logic that a safety injection (and reactor shutdown) is "unsafe."

Also, since this particular valve must close on a SIAS, failur e to close is precisely the kind of problem that needs to be detected.

Check Valve V2526 This valve must open to allow flow from the BA pumps (as well as the gravity flow path) to reach the charging pump suction.

This valve is not included in the ISI program.

It should be noted that the complexity of the BA system piping along with the above noted inconsistencies and omissions (as well as numerous others which are not noted since they do not have a direct bearing on the pumps) make it extremely difficult to discern exactly what ISI test-ing is being conducted in the BA system. This could only be determined by a review of testing procedures.

Recommended actions:

a. Testing of each BA pump quarterly, using xisting or test level instrumentation on the BA tanks to determine flow by transferring bor ic acid from one tank to the other.

b. A more thorough review of ISI testing in this system. (This would require test procedure review and direct discussions with St.

Lucie personnel.)

Containment S ra As noted in the LPSI section, these pumps, as well as the LPSI pumps could be individually tested at full flow by the addition of the single flow element recommended to be installed in line 6-CS-500 (see LPSI sec-tion).

Recommended actions:

Quarterly, full flow testing through the full flow path discussed under LPSI.

Diesel Fuel Oil Transfer (DOT)

Testing of the DOT pump, and the determination of flow, does not appear impractical. Various flow paths are available, including transfer to

f day tanks, or transfer from one storage tank to the other, whereby existing level instrumentation could be used to determine flow rate (if, as FP8L has argued, the level instrumentation is not accurate enough to meet code requirements, either a relief request on instrument accuracy or use of test instruments would be appropriate). There are a numb r of other possible means of measuring pump flow rate which would not require system modification, including:

a. Use of ultrasonic flowmeter

b. Use of the "Truck Fill (Without Pump) Connection" to pump oil from a truck or other source to the storage tank using the DOT pump.

Flow measurement could be made by observing the volume transferred in a specified time period.

C~ Use of the "Truck Fill (With Pump) Connection" to pump oil from the storage tank to a temporary receiver. Flow measurement could be made by observing the volume transferred in a specified time period.

There are some features in the St. Lucie design that make the monitoring of DOT pump flow essential:

a) The "fixed resistance" path for the DOT pumps is not, in reality, a fixed resistance path, since it incorporates an active component (Relief Valve 2I-SR17221 (1A) for the A pump 2I-SR17222 (1B) for the B pump].

b) There is no permanently installed pump suction pressure instrumen-tation. It is assumed that St. Lucie determines suction pressure for pump performance testing by use of storage tank level instru-mentation. In general, this would be acceptable (although it would contradict FP8L's contention that storage tank instrumenta-tion does not satisf y code accuracy requirements, and theref ore cannot be used, as a partial justification for not measuring flow). However, for the DOT pumps, suction strainers are shown to be ins tailed in the suction pi pi ng. DOT pump s trai ners have clogged at operating plants, rendering the pumps inoperable (see Ginna LER 87-001. Note that one of the corrective actions imple-mented by Ginna was to include flow and pressure measurements in their monthly tests of the diesels). Thus, using tank level or even temporary instr umentation in the suction line to monitor pressure upstream of the suction strainer (there are no isolable connections downstream of the strainer) does not necessarily give a true indication of ~um suction pressure. Further, a partially clogged suction strainer could allow the pump to operate in recir-culation conditions with no apparent degradation, but prevent the pump from d livering required flow to the day tanks (and/or damage the pump due to lack of required suction pressure).

It should be noted that there are no DOT system valves in the ISI solenoid program. There are two Class 3 check valves and two Class 3 valves per pump.

In addition, it was noted that the oil storage tank capacity, per FSAR Table 9.5-1 is 40,000 gallons. This is also the Tech Spec r equired volume. Unless there is an error in the FSAR, it would appear that there is no margin between tank capacity and required inventory, thereby re-sulting in an LCO each time a DOT pump is used to tr ansfer fuel.

Recommended actions:

a. Performance of a quarterly test of each DOT pump through a selected path in which flow is measured (multiple potential paths available).

b. Inclusion of check valves and solenoid valves between the DOT pumps and the day tanks in the ISI program.

c. Require monitoring of suction pressure downstream of the suction strainer.

Recommendations for inservice testing of the six types of pumps are sum-marized in Table 1.

General Comments If existing instrumentation is not accurate enough to meet code requirements, a relief request on the existing instrumentation ac-curacy (or use of test gauges), would be the appropriate avenue (as opposed to a relief request on testing altogether).

2. Where the addition of flow elements is recommended, it is not in-tended that an entire safety grade loop be added. Examples of satisfactory devices would be:

a. An in-line flow orifice with flange taps, tap isolation valves, and pipe caps. This, in conjunction with a delta p test gauge, could be used as a flow meter. (Would require hookup of test gauge and manual cor r elation of delta p to flow).

b. Use of a surf ace mounted ultrasonic flowmeter. If required code accuracy cannot be met, a relief request on instr umenta-tion accuracy should be acceptable. Note that if ultrasonic flowmeters are installed in locations that are suitable for other flowmeters (adequate straight pipe section without turbu-lence inducing fittings), they can be reasonably accurate, and if lef t in a fixed position, very repeatable. Since ISI programs are, in gener al, primarily concerned with detecting degradation, repeatability is the parameter of most concern.

30 If the length of time a pump must be run would result in too much fluid transfer through the preferred or instrumented flow path, a relief request which allows, for example, running five minutes in r ecirc and then switching to the desired valve lineup for monitor-ing flow and pressure conditions would be reasonable. Flow stability could be achieved and measurements documented in 30 seconds (or less) if necessary. A total relief from testing just

because of a time- volume problem appears nei ther necessary nor j ustif iable.

There are numerous valves (check valves) which cannot be properly tested unless pumps are properly tested. The review of valves to be tested in the St. Lucie ISI program was focused on only those valves which have a direct impact upon pump performance.

Based upon observations made as a part of this review, a full, de-tailed review of St. Lucie's pump and valve program appears war-ranted.

It was noted that the prints provided by FPE L 'indicated the presence of suction strainers for all pumps reviewed. If this is in fact true, and the strainers were not removed after pre-operational testing, monitoring of pressure drop across the strainers or monitoring suction pressure downstream of the strainers before and during the pump run is critical, particularly for systems which are likely to have solids in the stream.

It is probable that some strainers are still in use, such as for the diesel fuel oil pump strainer, but that some others, such as the LPSI pump strainer s, were removed following preoperational test.

Table 1. Current and Recommended Pump Inservice Testing CURRENT TESTING RECOMMENDED TESTING (as deduced from references)

QUARTERLY MODE 5 or 6 QUARTERLY MODE 5 or 6 HPSI Hiniflow recirculation Injection flowpath Monitor flow, suction Same as Current.

flowpath used. Flow used. Pump flow, pressure and developed not monitored. Pump suction pr essure head in miniflow re-suction pressure and and developed head circulation flowpath.

developed head moni- monitored. (Full Use installed flow tored. flow, Mode 6) instrumentation.

LPSI . Hiniflow recirculation Shutdown cooling Monitor flow through Same as Current flowpath used. Flow flowpath used. miniflow recirculation not monitored. Pump Pump flow, suction flowpath and full suction pressure and pressure and flow recirculation developed head moni- developed head flowpath (through line tored. monitored. (Full 6-CS-500), along with flow, Mode 5) suction pressure and developed head. Use installed flow instru-mentation for normal recirculation flowpath.

Add new flow instru-ment to line .6-CS-500 for full flow monitoring.

AFW Miniflow recirculation Saf ety r el ated Monitor flow, suction Same's current.

flowpath used. Flow flowpath to SGs pressure and developed not monitored. Pump used. Pump flow, head in recirculation suction pressure and suction pressure flowpath. Mill require developed head moni- and developed new instrumentation.

tored head monitored. (Honthly in this case.)

(Full flow, Hode 5)

PUHP CURRENT TESTING RECOMMENDED TESTING (as deduced from references)

QUARTERLY HODE 5 or 6 QUARTERLY MODE 5 or 6 BORIC Hi. ni flow recirculation Flow moni tored using Monitor flow by trans- Same as current.

ACID flowpath used. Flow "existing flow-rate ferring boric acid from provided that the not monitored. Pump meters" ( could be one tank to the other current testing suction pressure2 and flow to BA blender and observing level delivers flow through developed head moni- or charging pump change. Also monitor the emergency boration tored. discharge flow). pump suction pressure flowpath and monitors Suction pressure and developed head. flow by use of charg-and developed head ing pump discharge monitored. flow meter.

CON- Minimum flow recir- No specific addi- Monitor flow through No specific additional TAIN- culation flowpath tional testing. full flow recircula- testing.

MENT used. Flow not tion flowpath ( tbr ough SPRAY monitored. Pump line 6-CS-500), along suc'tion pressure and with suction pressure developed head moni- and developed head.

tored. Add new flow instrument to line 6-CS-500 for full flow monitoring.

DIESEL Minimum flow re- No specific addi- Honitor full flow No specific additional FUEL ci r culat i on flow- tional testing. through one of several testing.

OIL path (which includes alternative flowpaths a relief valve) used. (see discussion).

Flow not monitored. Monitor suction pres-Pump suction pressure sure and developed head.

and developed head monitored.

FOOTNOTES

1. Only one flow test is intended, with both the full recirculation flowpath (6-CS-500) and the recirculation flowpath monitored.

2. The boric acid pumps are not provided with a suction pressure gauge. It is assumed that suction pr essure is mor.'tored by conversion of boric acid tank level indication.

3. While the St. Lucie plan indicates that pump suction pressure is monitored, it does not appear that it can be monitored by any, means other than by use of storage tank level. While this would generally be acceptable, the fact that suction strainers are indicated between the source tank and the pump suction make use of tank level an invalid indication of pump suction pressure. The presence of strainers also makes periodic full flow monitoring more critical.

References:

l. Letter, C. 0. Woody to USNRC, July 31, 1987, "Relief from Parts of ASME Section XI"

2. Letter, C. 0. Woody to Mr. Ashok C. Thadani (NRC), October 13, 1986, "Relief from Parts of ASME Section XI"

3. Letter, C. 0. Woody to USNRC, January 28, 1988, "Request for Additional Information, ASME Code Relief Requests for Various Safety-Related Pumps"

4. Letter, W. F. Conway to USNRC, May 12, 1988, "2nd Request for Additional Information, ASME Code Relief Requests for Various Safety-Related Pumps"

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