05000423/LER-1997-003-01, :on 970113,potential for Recirculation Spray Sys Piping Failure Occurred Due to RSS Pump Stopping & Restarting During Accident Conditions.Performed Evaluation of RSS Water Column Separation Issue

:on 970113,potential for Recirculation Spray Sys Piping Failure Occurred Due to RSS Pump Stopping & Restarting During Accident Conditions.Performed Evaluation of RSS Water Column Separation Issue

ML20134P599
Person / Time
Site:	Millstone
Issue date:	02/11/1997
From:	Peschel J NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20134P578	List: 05000423/LER-1997-003, Forwards LER 97-003-00 Which Documents Condition That Was Determined at Mnps,Unit 3 on 970113,per 10CFR50.73(a)(2)(ii) (B).List of Commitments,Encl 05000423/LER-1997-003-01, :on 970113,potential for Recirculation Spray Sys Piping Failure Occurred Due to RSS Pump Stopping & Restarting During Accident Conditions.Performed Evaluation of RSS Water Column Separation Issue
References
LER-97-003-01, LER-97-3-1, NUDOCS 9702260042
Download: ML20134P599 (3)

LER-1997-003, on 970113,potential for Recirculation Spray Sys Piping Failure Occurred Due to RSS Pump Stopping & Restarting During Accident Conditions.Performed Evaluation of RSS Water Column Separation Issue

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
4231997003R01 - NRC Website

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e NRC FORM 366 U.s. NUCLEAR REGULATORY COMMisslON APPROVED BY OMB NO. 3160-0104 EXPIRES 04/30/98 H 95) l woe'Tio*""o'Yc'v"o"'*le!Jsl s'oWs"'"neI*oin"o^"iU8E 11's"'?o^"Lo'u"?tt "^"at.?o 'E'oJS=ta i!?a'o ^ 82 n

LICENSEE EVENT REPORT (LER)

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(See reverse for required number of digits / characters for each block) l FACIUTY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Millstone Nuclear Power Station Unit 3 05000423 1 of 3 i

TITLE 14) l Potential For Recirculation Spray System (RSS) Piping Failure Due To RSS Pump Stopping And Restarting l

During Accident Conditions f

EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVislON MONTH DAY YEAR FAclLITY NAME DOCKET NUMBER NUMBER j

l 01 13 97 97 003 00 02 11 97 I

CPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11)

DE W 5

20.22o1(b) 2o.2203(aH2Hv) 50.73(aH2)(i)

So.73(a)(2Hviii) i POWER 20.2203(a)(1) 20.2203(a)(3)(i)

X so.73(=>{2)iii)

So.73(aH2Hxi LEVEL (10) 000 20.2203(aH2Hi) 20.2203(a)(3Hii) 50.73(a>{2)(iii) 73.71 20.2203(a)(2)(ii) 2o.22o3(a)(4)

So.73(a)(2Hiv)

OTHER 20.2203(aH2Hiii) 50.36(c)(1) 50.73(a)(2)(v)

Specify in Abstract below or en NRC Form 366A 20.22o3(aH2Hiv)

So.36(cH2)

So.73(aH2Hvii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (include Area Codel l

J.M. Peschel, MP3 Nuclear Licensing Manager (860)437-5840

)

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPRDS l

SUPPLEY s f AL REPORT EXPECTED (14)

ExPECTEL MONTH DAY YEAR SUBWSSN

[ NO YEs (if yes, complete EXPECTED sUBMisslON DATE).

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On January 13,1997, an engineering evaluation determined the Recirculation Spray System (RSS) heat exchangers and piping may be susceptible to water column separation, and subsequ'snt water hammer, if the RSS pumps are restarted during design basis accident conditions. This condition h'as been determined to be outside the design basis and the RSS was declared inoperable. NRC notification of this event was made pursuant to 10CFR50.72(b)(1)(ii)(B), on January 13,1997. The Unit was in Mode 5 and in an extended shutdown. The cause of this event is design deficiency due to inadequate RSS design scope which did not incorporate and analyze the system susceptibility to waterhammer and its effects.

An evaluation of the RSS water column separation issue will be performed to determine if transient piping and equipment loads are acceptable or require design modification.

{

i 9702260042 970211 PDR ADOCK 05000423 l

S PDR NRC FORM 366 (4-95) l

.U.s. NUCLEAR REGULATORY COMMISSION (495)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION l

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

I YEAR SEQUENTIAL REVistoN I

Millstone Nuclear Power Station Unit 3 05000423 NUMBER NUMBER 2 of 3 97 003 00 l

i l

TEXT (11more space is required, use additional copies of NRC Form 366A) (17) r I.

Description of Event

l On January 13,1997 with the Unit in Mode 5, it was determined that water column separation and subsequent l

witerhammer may occur in the Recirculation Spray System (RSS) in response to:

l RSS pump starting, with subsequent manual stopping and restarting in accordance with the Emergency Operating e

Procedures (EOPs) for a design basis accident, and I

RSS pump automatic starting and subsequent loss of power to the RSS pumps (single failure), followed by o

equipment recovery leading to pump restart.

Evznt discovery occurred during a review for Generic Letter (GL) 96-06," Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions". Event notification was made on January 13,1997, pursuant to requirements of 10CFR50.72(b)(1)(ii)(B), as a condition that is outside the design basis of the plant.

Present RSS design ensures the pumps could operate with initially empty piping downstream of the pumps. However, j

th) effects upon the RSS from a partially filled system or a water column separation condition and the subsequent i

l waterhammer when the pumps are restarted were not considered. This waterhammer could occur because the RSS 1

piping is subject to partial draindown if the RSS pumps are stopped, thereby making the RSS piping susceptible to water column separation.

Emergency operating procedures allow the RSS pumps to be manually stopped and then restarted, as required to maintain containment pressure and to control radiation levels during Design Basis Accident (DBA) conditions.

R pressurization of the containment may occur after the RSS pumps are manually stopped. As such, the RSS was

]

dIclared inoperable due to the potential for RSS system failure if the RSS pumps are started and stopped following a d: sign basis event. This condition has been determined to be reportable, pursuant to 10CFR50.73(a)(2)(ii)(B), as a condition that was outside the design basis of the plant.

ll.

Cause of Event

Th3 cause of this condition was a design deficiency which resulted in inadequate initial RSS System design scope in that it did not incorporate and analyze for susceptibility of waterhammer conditions and the effect on the RSS system.

111. Analysis of Event Thsre were no adverse safety consequences from this condition, in that the Unit has not experienced an event r: quiring the actuation of the RSS. However, waterhammer in a train of the RSS could damage the involved RSS train's pressure boundary and may potentially result in secondary damage to the redundant RSS train. This damage I

could create a containment radiation release pathway, which would necessitate use of the RSS containment isolation valves. These valves may also be adversely affected by the waterhammer and resulting consequences, potentially inhibiting the ability of the valves to terminate or minimize a release pathway.

I In addition, a harsh environment could be created in the Emergency Safety Features Building, which would be beyond ths Unit design basis. This could occur if elevated temperature water from the containment sump flooded the building cs a result of RSS System pressure boundary damage within the building.

NRC FcRM 366A U.S. NUCLEAR RECULAToRY CoMMisslON (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVislON Millstone Nuclear Power Station Unit 3 05000423 NUMBER NUMBER 3 of 3 97 003 00 TEXT (11more space is required. use additional copies of NRC Form 366A) t17)

IV. Corrective Action

Th3 following actions will be taken in response to this event:

1. An evaluation of the RSS water column separation issue will be performed to determine if transient piping and equipment loads are acceptable or require design modification.

V.

Additional Information

None

Similar Events

LER 96-006-00:

• Plant Shutdown Reauired by Technical Soecification. for Auxiliary Feedwater Containment Isolation Valves Declared inoperable" This LER reported an original plant design deficiency with Auxiliary Feedwater containment isolation valves where the valves would not remain closed against the containment peak design pressure. This event was similar with respect to the cause of the event being design deficiency. However, the corrective action for this event would not have revealed the concem with water column separation and resultant waterhammer due to operation of the RSS pumps.

LER 96-007-00:

" Containment Recirculation Sorav. Quench Sorav. and Safety Iniection Systems Outside Desian Basis Due to Desian Errors" This LER reported that the Unit had operated in a condition that was outside the design basis due to inadequate design of the RSS spray piping and supports for thermal loads due to accident temperatures. This could have resulted in stresses above the design allowable stresses for

• Faulted" conditions. This event was similar in that due to a design deficiency, the potential existed that the RSS may not have been able to fulfill its required safety function. However, the corrective action for this event considered the effects of temperature and would not have revealed the concem with water column separation and resultant waterhammer due to operation of the RSS pumps.

Manufacturer Data Ells System Codes Containment Spray System - BE Ells Eauipment Codes Piping - PSX l4