ML20235L852

Responds to NRC Bulletin 88-004, Potential Safety-Related Pump Loss. Pump Mfgs Could Not Provide Sufficient Flow Info.Util Calculated Eight Pump Simultaneous Miniflow,As Provided for in Item 3 of Bulletin

ML20235L852
Person / Time
Site:	Fort Calhoun
Issue date:	02/10/1989
From:	Morris K OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-004, IEB-88-4, LIC-89-046, LIC-89-46, NUDOCS 8902280006
Download: ML20235L852 (12)

Text

- _ _

_f.____ - - - - - . _ _ . - - =..___ _ _. _ _ _ _ __

Omaha Public Power District 1623 Harney Omaha, Nebraska 68102 22-47 402/536 4000 February 10, 1989 LIC-89-046 U. S. Nuclear Regulatory Cnmmission Attn: Document Control Desk Mail Station P1-137 Washington, DC 20555

References:

1. Docket No. 50-285

2. NRC Bulletin 88-04 " Potential Safety-Related Pump loss" dated May 5, 1988

3. Letter from OPPD (K. J. Morris) to NRC (Document Control Desk) dated July 8, 1988 (LIC-88-579)

4. Letter from OPPD (K. J. Morris) to NRC (Document Control Desk) dated November 4, 1988 (LIC-88-929)

5. Licensee Event Report 50-285/88-032 dated December 1, 1988 (LIC-88-1060)

Gentlemen:

SUBJECT:

Response to NRC Bulletin 88-04 Enclosed is Omaha Public Power District's (0 PPD) final resolution to reference

2. Reference 4, stated that additional time was required to obtain the pump manufacturers confirmation of the adequacy of the miniflow recirculation lines. The pump manufacturers could not provide sufficient flow information.

Therefore, OPPD calculated the eight (8) pump simultaneous miniflow, as provided for in Item 3 of the Bulletin, to determine the maximum achievable flow in the comon recirculation header. This information was comoared to the original manufacturer-recommended minimum flow rates. In evaluating the results, a design deficiency was identified and reported in reference 5. A modification has been installed, and testing has been conducted to resolve the concerns which were identified. This submittal supersedes reference 4.

Pursuant to the provisions of Section 182a of the Atomic Energy Act of 1954, as amended, this response is submitted under oath and affirmation.

39022s0006 s90210 PDR ADOCK OSiOOLF V DG N

O Q{l

/

455124 Employmen h lal Opportunity i

m. ,

'4 U.'SiNuclearRegulatoryCommission LIC-89-046-

'Page 2-The. submittal'date of February 10, 1989, was discussed between Mr. P. D.

Milano, NRC Project Manager, and members of my staff. If you should have any

. questions, please do not hesitate to call.

~

Sincerely, w )) q [h k p K.Division J. MorfisManager Nuclear Operations

" Attachment KJM/sa c: LeBoeuf, Lamb, Leiby & MacRae R. D. Martin, NRC Regional Administrator P. D. Milano, NRC Project Manager.

P. H. Harrell, NRC Senior Resident Inspector

)-

3

. . UNITED STATES OF AMERICA 1

. NUCLEAR. REGULATORY COMISSION- J In the Matter of.

Omaha:Public Power District- Docket No. 50-285 (Fort.Calhoun Station UnitNo.1)

. q.

AFFIDAVIT W. G... Gates;.being duly' sworn, hereby deposes and says that he is the-Manager-Fort Calhoun: Station of the.0maha Public Power District; that as such he is.ddlyl authorized to sign and file ^with the Nuclear Regulatory Commission .i the attached information-concerning the updated response-to NRC Bulletin 88-04;'

-that'he is familiar with.the content thereof; and that the matters. set forth-

,, therein are;true and correct to the best of his knowledge, information, and belief,- l y ' y gg .

W. G.: Gates-Manager-Fort Calhoun Station STATE OF NEBRASKA ss COUNTY OF DOUGLAS Subscribed and sworn.to before me, a Notary Public in and for.the State of Nebraska.on this _//fa day of February, 1989.

Y Aebvw g.netar,eue>4c Cl4[RAL NOTARY State of htrasta :

J.T. GLEASON -

h Wy ComIL IJS hly 2ft 1910 l

l

g - - - - -

? ,.

. 1

. x 4

.. ,U. S. Nuclear Regulatory. Commission LIC/89-046 y

S ATTACHMENT

,' Response to NRC Bulletin 88-04 BORIC ACID PUMPS CH-4A/B Item 1. Determine if piping configuration precludes pump-to-pump interaction durbg miniflow operation. )

)

Ea' ch b' oric acid pump ha's two individual recirculation 1ines. which route.to a boric acid storage. tank. (Boric acid pump CH-4A's lines route back to boric l acid tank CH-11A, and boric acid. pump CH-4B's lines route back to boric acid  ;

tank CH-llB.) 0ne. recirculation line (2-inch dia.) is routed through an i air-operated, isolation valve.and is used for recirculating tank contents during normal plant operation and purap surveillance testing. The 2-inch line is .j capable of passing nearly full pump flow; the normal boric acid injection flowpath is through a 3-inch line. The other recirculation line (1/2-inch dia.)-is considered to be the minimum recirculation line and is routed through a normally open manual needle valve.

The complete separation of recirculation lines precludec the possibility of pump-to-pump _ interaction during simultaneous miniflow c,peration.

The 'l/2-inch minimum recirculation line provides 'a continuous bypass flow for-

each pump to its respective boric acid tank during all modes of boric acid pump operation. Both the two inch and the one-half inch lines are used during Boric.

Acid Pump operation and test.

Item 2. If Item I is applicable, evaluate the system for flow division.

This item _is not applicable to the CH-4A/B boric acid pumps, since pump-to-pump interaction is not possible during. simultaneous miniflow operation. No further

. action is deemed necessary. j Item 3. Evaluate the adequacy of the miniflow recirculation lines. l

'A Safety Injection Actuation Signal (SIAS) will start boric acid pumps CH-4A/8. The' SIAS also closes the air-operated valves on the pumps' 2-inch recirculation lines and opens valve HCV-268 to align CH-4A/B discharge to feed

. the suction of the charging pumps. The th-ee charging pumps are also started ,

on an SIAS. Thus, in a situation involving S'AS actuation, the boric acid '

pumps are not aligned in a minimum recirculation flow configuration.

Periodic surveillance testing of these pump ; is performed using the 2-inch ,

recirculation line flowpath, not the 1/2-inch line. The-pumps are not operated '

.in a minimum recirculation mode during testing. l 1

U. S. Nuclear Regulatory Commission LIC-89-046 BORIC ACID PUMPS CH-4A/B C$atinued The CH-dA/B pumps could operate in the miniflow mode during certain event scenarios (e.g., failure of HCV-268 to open on SIAS, or loss of instrument air during pump operation). ' Assuming the miniflow lines are not adequate, the worst-case scenario would be the loss of the boric acid pumps due to inadequate pump flow. The function of the boric acid pumps are to feed concentrated boric acid to the charging pumps for injection into the reactor coolant system.

Huwever, there is a redundant capability for feeding toric acid to the charging pumps. The boric acid gravity feed flowpath runs directly from each boric acid tank to a common header which ties into the charging pump suction header. The gravity feed flowpath is also automatically aligned on an SIAS (refer to USAR Section 9.2.5). SIAS-repositioned valves on the gravity feed flowpath are periodically in-service tested to verify operability.

Since the boric acid pumps are operated in near full-flow recirculation mode during normal plant operation and during pump testing, it is concluded that further evaluation of the adequacy of the 1/2-inch line is not necessary. No further ad ion is deemed necessary.

Item 4. Provide written response which summarizes problems, identifies corrective actions, provides schedule for implementation of corrective actions, and provides justification for continued operation.

The respons.e to Bulletin 88-04 for pumps CH-4A/4B can be considered complete, since no pump-to-pump interaction can occur and no operating or test procedures operate the puns using only the minimum recirculation line.

/

l 2

U. S. Nuclear Regulatory Commission i LIC 89-046 SAFETY INJECTION (SI) and CONTAINMENT SPRAY (CS' OUMPS SI-1A/B (LPSI). SI-2A/B/C (HPSI). SI-3A/B/C (CS)

Item 1. Determine if piping configuration precludes pump-to-pump interaction

! during miniflow operation.

Each safet' injection and containment spray pump has its own individual miniflow reurculation orifice, and the minimum recirculation lines tie tog 1ther (downstream of the orifices) into a common header prior to discharge into the Safety Injection and Refueling Water Tank (see Figure 1).

Prior to a modification (MR-FC-88-110, see page 9) which was installed during the 1988 refueling outage, all eight pumps would start upon receipt of a Safety Injection Actuation Signal (SIAS). An SIAS can be initiated by either a Pressurizer Pressure Low Signal (PPLS) or a Containment Pressure High Signal (CPHS). The PPLS setpoint is 1600 psia, which is above the HPSI shutoff head.

Thus, at the moment PPLS initiates the SIAS, reactor coolant system pressure precludes safety injection flow and the HPSI and LPSI pumps will initially be in a simultaneous miniflow mode. In a large break LOCA scenario, the HPSI and LPSI pumps would be in the miniflow mode for a very short time due to large, rapid Reactor Coolant System (RCS) depressurization. In a small break LOCA scenario, the pumps could operate in the miniflow mode for an extended time.

Prier to modification, the containment spray pumps would have operated in the miniflow mode after SIAS initiation until a Containment Spray Actuation Signal (CSAS) was received. A CSAS is initiated upon receipt of both a PPLS and CPHS. The CSAS opens the spray header isolation valves to containment, thus allowing full flow from the spray pumps and allowing them to leave the miniflow mode. In a large break LOCA scenario, the CS pumps would have been in the miniflow mode for a very short time due to large, rapid RCS depressurization and containment pressurization. Other scenarios (e.g. steam generator tube rupture, LOCA outside containment, etc.) could generate an SIAS but not a CSAS. In these scenarios, the CS pumps, prior to modification, could have operated in the miniflow mode for an extended time. The common miniflow header for the HPSI, LPSI, and CS pumps does not entirely preclude pump-to-pump .

interaction during simultaneous miniflow operation. l Item 2. If Item 1 is applicable, evaluate the system for flow division. l The original manufacturer-recommended minimum flow rates and the calculated flow rates for the eight-pump simultaneous miniflow mode are as follows:

Original Calculated Mfg. Spec. Flowrate SI-1A LPSI Pump 200 gpm 107 gpm SI-18 LPSI Pump 200 gpm 105 gpm SI-2A HPSI Pump 35 gpm 32 gpm l SI-28 HPSI Pump 35 gpm 32 gpm SI-2C HPSI Pump 35 gpm 32 gpm SI-3A CS Pump 200 gpm 118 gpm SI-38 CS Pump 200 gpm 115 gpm SI-3C CS Pumo 200 aom 114 ocm TOTAL 1105 gpm 655 gpm 3

"'- u. S. Nuclear Regulatory Commissi6n 1.10.89 046 F1GURE 1 Safety injection and Containment Spray Pumps Minimum Recirculation Arrangement s.fety. Injection 6" # and t u 3 '

storage Tank X -

1 C$'PumD 3 51-3C h

o x WP ,cssi. u,.o 6 4

' 8 -

u x WI# cs ,..,

~

C 5'-"

=

.. M._ M '"

a t t.,5! ,u.,

g s,.1a x

w!9

=

t,si ,u T S1-1B <u x m F' e,s1 e.

L, si a i

X '& l C ses! Pumo A s1-?C x

WM s

, esi e...

v.n .-

4  ;

i

. V. S. Nuclear Regulatory Commission LIC:89-046 SAFETY INJECTION (SI) and CONTAINMENT SPRAY (CS) PUMPS SI-1A/B (LPSI). SI-2A/B/C (HPSI). SI-3A/B/C (CS) continued The HPSI pump manufacturer (Sulzer-Bingham) has confirmed that the originally specified 35 gpm minimum flow is adequate for minimum recirculation runs of less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The LPSI/CS pump manufacturer (Ingersoll-Rand) has not confirmed prop?r minimum flow requirements. Calculations indicate the HPSI, LPSI, and CS pumps would not have been able to achieve their original manufacturer specified minimum flow rates while operating in the simultaneous miniflow mode.

This discrepancy between the recommended flow and the calculated flow was reported in Licensee Event Report 50-285/88-032. (Reference 5)

Item 3. Evaluate the adequacy of the miniflow recirculation lines.

The vast majority of operating hours for the HPSI and CS pumps have been in the individual miniflow mode during quarterly surveillance testing. Although the LPSI pumps are used for shutdown cooling, a significant amount of their total operating hours has also been in the individual miniflow mode during quarterly surveillance testing.

In order to assess the adequacy of the miniflow recirculation lines for the purposes of periodic individual pump testing, the safety injection and containment spray pumps were evaluated. This evaluation was accomplished through measurement of pump performance at design flow conditions. Special Procedure SP-SI/CS-2 was performed in November, 1988, which recorded pump flow / head performance for each of the eight pumps at design flow (or near design flow) conditions. The data from this procedure, when compared to the manufacturers' pump curves, showed no discernible degradation for any of the eight pumps over the long term from using the miniflow line for quarterly individual pump testing. (Past maintenance records show that only minor maintenance has been performed on these pumps since 1973.) The plant surveillance testing program will be reviewed, prior to the next refueling outage, for the possible addition of a test similar to SP-SI/CS-2 to be performed at regular intervals.

Calculations were performed to determine the flow rates through the HPSI and LPSI pumps while the five of them were operating in a simultaneous miniflow mode. It was found that the HPSI pumps could achieve approximately 33 gpm each, and the LPSI pumps could achieve approximately 150 gpm each.

Special Procedure SP-SI/CS-3 was performed in November,1988 to observe the behavior of the HPSI and LPSI pumps while all five pumps were running in a simultaneous miniflow mode for 30 minutes. This is the pump configuration after modification. Thirty minutes was chosen as the time required before operator actions could be taken to shutdown pumps. The running of the pumps was witnessed by a pump consultant, along with representatives from Sulzer-Bingham (HPSI pump manufacturer) and Ingersoll-Rand (LPSI pump manufacturer). 1perating parameters of the pumps were closely observed during the run. By the time the last set of data was obtained and the pumps were shut down, the pumps had run in the simultaneous miniflow mode for 45 minutes.

5

. .- l

. U. S. Nuclear Regulatory Commission LIC'-89-046 {

SAFETY INJECTION (SI) and CONTAINMENT SPRAY (CS) PUMPS i SI-1A/B (LPSI). SI-2A/8/C (HPSI). SI-3A/B/C (CS) continued None of the pumps showed any signs of abnormal operation, and the data obtained did not differ significantly from past surveillance test data (which used the individual miniflow mode) for the pumps. The successful completion of SP-SI/CS-3 demonstrated the HPSI and i. PSI pumps can operate in a simultaneous miniflow mode for at least 45 minutes. The stable operation of the pumps in  ;

this along with the acceptable data suggests the pumps could have run longer than 45 minutes without difficulty.

Manufacturer confirmation of pump minimum recirculation requirements is not necessary since, as provided for in Item 3 of the Bulletin, actual system tests have proven that the present minimum flow rates are adequate.

Item 4. Provide written response which summarizes problems, identifies corrective actions, provides schedule for implementation of corrective actions, and provides justification for continued operation.

The pump performance data from SP-SI/CS-2 shows that the safety injection and containment spray pumps are capable of delivering their design flow at the ,!

required pressure. This demonstrates that past testing of the pumps using the miniflow lines has not caused pump degradation over the long term. Continued use of this test mode is therefore acceptable.

The existing common miniflow line cannot accommodate the 1105 gpm (based on original design manufacturers-recommended minimum flow rates) total miniflow from all eight pumps running simultaneously. However, the successful  ;

performance of SP-SI/CS-3 demonstrates that five pumps, the two LPSI and three HPSI pumps, can operate in the simultaneous miniflow mode for at least 45 minutes.

Plant accident analyses, Emergency Operating Procedures (E0P's), and Abnormal Operating Procedures (A0P's) have been reviewed. It has been verified that for each accident scenario in Section 14 of the USAR, at least one of three conditions will be met: )

(1) The accident does not involve SIAS initiation.

(2) Normal progression of the accident allows the safety injection pumps  ;

to inject into the reactor coolant system in less than 30 minutes, thus removing them from the miniflow mode.

(3) The existing Emergency Operating Procedures and Abnormal Operating Procedures contain instructions which allow and direct operators to shut down non-injecting safety injection pumps. The placement of these instructions in the overall step sequences of the procedures provide a higS confidence level that this operator action will be j taken within 30 minutes of SIAS actuation, thus removing them from the j miniflow mode.

6 i

1

. U. . S. Nuclear Regulatory Commission LIC'89-046 i SAFETY INJECTION (SI) and CONTAINMENT SPRAY (CS) PUMPS SI-1A/8 (LPS!). SI-2A/B/C (HPSI). SI-3A/B/C (CS) continued

)- Although the E0P's and A0P's have been found to be adequate, they will be reviewed further. The purpose of this review will be to develop possible procedural enhancements to increase operator awareness and monitoring of j simultaneous miniflow operation of the safety injection pumps. The procedural  !

enhancements will be made in accordance with the schedule presented in the  ;

Safety Enhancement Program transmitted on December 9, 1988 (0 PPD letter l LIC-88-1094).

Modification MR-FC-88-110, SI-3A/B/C Start Signal Logic Change, has been installed. This modification removed the three SI-3A/B/C containment spray pumps from the SIAS start signal logic which starts the SI-1A/B lov nressure and SI-2A/B/C high pressure safety injection pumps. The CSAS signal which l opens the spray header containment isolation valves will also be used to start l the SI-3A/B/C pumps. Thus, the spray pumps will not operate in a simultaneous miniflow mode when they receive a start signal. The Fort Calhoun Station CS start logic is consistent with other Combustion Engineering plants and therefore is not unique. Operators have completed training on the modification ,

to the CS start logic.

The response to Bulletin 88-04 for the safety injection and containment spray pumps can be considered complete. Modification MR-FC-88-110 which modified the CS pump start logic was installed during the 1988 Refueling Outage and the testing conducted resolves the concerns associated with Bulletin 88-04, thus no justification for continued operation is necessary.

7

\

e

. U. S. Nuclear Regulatory Commission  !

LIC'-89-046 AUXILIARY FEEDWATER (AFW) PUMPS FW-6. FW-10 Item 1 - Determine if piping configuration precludes pump-to-pump interaction during miniflow operation. .

1 Each auxiliary feedwater pump has its own independent miniflow recirculation line to the emergency feedwater storage tank. Since there are two separate lines, there is no possibility of pump-to-pump interaction during simultaneous miniflow operation of FW-6 and FW-10. No further action is required concerning the AFW pumps.

Item 2 - If Item 1 is applicable, evaluate the system for flow division.

This item is not applicable to the FW-6 and FW-10 auxiliary feedwater pumps, since no pump-to-pump interaction is possible. No further action is required Item 3 - Evaluate the adequacy of the miniflow recirculation lines.

The adequecy of the sizing of the FW-10 miniflow recirculation line has been confirmed with the pump manufacturer.

Based on past operating and testing experience with FW-10, together with the manufacturer's confirmation of proper miniflow line capacity, it is concluded that the present.miniflow recirculation design for FW-10 is adequate to preclude pump damage.

No further action is required for FW-10.

A response from the FW-6 motor-driven auxiliary feedwater pump manufacturer has been received. The manufacturer states that the actual miniflow flowrate (as '

measured during surveillance testing) is below the sizing of the manufacturer supplied bypass orifice. The manufacturer recommended investigation of the discrepancy between the design miniflow orifice capacity and the actual I miniflow flowrate measured during surveillance testing. However, the '

manufacturer goes on to state:

"Our review and evaluation of the operating characteristics of this pump, the operating circumstances, piping arrangements, and P&ID's discussed in the telecons and the minimal mechanical difficulties encountered since initial start-up; indicate that the minimum recirculation flow system appears to be adequate as long as present operating parameters and conditions are followed."

8

.. .f

. V. 'S. Nuclear Regulatory Commission LIC'-89-046 AUXILIARY FEEDWATER (AFW) PUMPS FW-6. FW-13 Item 4 - Provide written response which summarizes problems, identifies corrective actions,: provides schedule for implementation of corrective actions, and provides justification for continued operation Although there is a discrepancy between the actual measured miniflow flowrate and the bypass line capacity, the manufacturer believes that the present system does not affect pump operability, and therefore does not present a safety concern.

The response to Bulletin 88-04 for pumps FW-6 and FW-10 can be considered complete, since no pump-to-pump interaction can occur, and the existing miniflow. system has been confirmed as adequate by the manufacturer. No corrective actions are deemed necessary to preclude pump damage. OPPD will research the miniflow discrepancy on FW-6 described above by the completion of the 1990 refueling outage.

9 I

_- . _ __--__ - ____-_ _ _ _