ML20056C224: Difference between revisions

From kanterella
Jump to navigation Jump to search
(StriderTol Bot insert)
 
(StriderTol Bot change)
 
Line 1: Line 1:
{{Adams
#REDIRECT [[05000271/LER-1993-005]]
| number = ML20056C224
| issue date = 05/05/1993
| title = LER 93-005-00:on 930406,determined That CRD Scram Times Greater than TS Limits & Plant Shut Down Due to Unrelated Minor Leak in Feedwater Sys.Root Cause Will Be Submitted in Suppl Ler.Valves Rebuilt W/New components.W/930505 Ltr
| author name = Wanczyk R
| author affiliation = VERMONT YANKEE NUCLEAR POWER CORP.
| addressee name =
| addressee affiliation = NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
| docket = 05000271
| license number =
| contact person =
| document report number = LER-93-005, LER-93-5, NUDOCS 9305110308
| document type = LICENSEE EVENT REPORT (SEE ALSO AO,RO), TEXT-SAFETY REPORT
| page count = 5
}}
 
=Text=
{{#Wiki_filter:--
7-VdRMONT YANKEE NUCLEAR POWER CORPORATION Q.
            .fk7        P.O. Box 157, Governor Hunt Road l    )      Vernon, Vermont 05354-0157
      \          fj      (802) 257-7711 May 5, 1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555
 
==REFERENCE:==
Operating License DPR-28 Docket No. 50-271 Reportable Occurrence No. LER 93-05 Dear Sirst As defined by 10 CFR 50.73, we are reporting the attached Reportable Occurrence as LER 93-05 very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION edae Robert J anczyk Plant Manager ec:  Regional Administrator USNRC Region I 475 Allendale Road King of Prussia, PA 19406 100071                                                                                ,
9305110308 930505 PDR      ADOCK 0300 2 1 f.j f/)l  l S
 
_ _ _ - -                            .- -          . - . - - .- _ ~ _                        , _- _ ~
s                                                                                                                                                                L
      .      NRC fers 366 U.S. NUCLEAR REGULATORY CO* !$$10N                                                  APPROVED OMS No. 3150-0104                                      f (6-89)                                                                                                            EXPIKES 4/30/92                                  [
ESTIMATED BURDE3 PER RESPONSE TO COMPLY WITH THIS                                j INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD ComENTS REGARDlWG BURDEN ESTIMATE TO THE RECORDS AND                            !
REFORTS MANAGEMENT BRANCH (P.350), U.S. NUCLEAR REGULATORY                      i COMMISSION, WASHINGTON DC 20555, AND TO THE PAPERWORK                            !
REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND                          [
BLDGET, WASHINGTON, DC 20603.                                                    i FACILITY WAME (1)                                                                                DOCKET NO. (2)                                                    I PAGE (3)
VERMONT YANKEE NUCLEAR POWER STATION 0l5l0l0l0l2l7l1                            0    1      0F    0    4 f
TITLE (4) CONTROL ROD DRIVE SCRAM TIMES GREATER THAh THAT REQUIRED BY TECHNICAL $PECIFICATIONS DUE TO SCRAM SOLENDID PILOT VALVE COMPONENTS f
                                                                                                                                                                                )
i EVENT DATE (5)                        LER NUMBER (6)                              REPORT DATE (7)              OTHER FACILITIES INVOLVED (8)                  !
'                                                                                                                                                                                I MONTH            DAY      YEAR    YEAR          SEC #                  REV #    MONTH      DAY      YEAR            FACILITY NAMES              DOCKET Wo. ($)
* 0 5 0 0 0 0      4    0      6    9    3  9    3  -
0          0    5    -
0  0    0      5  0    5  9          3                              0 5 0 0 0
{
OPERATING                        THIS REPORT t$ SUBMITTED PURSUANT TO RE0'M1S OF 10 CFR i: CHECK ONE OR MORE (11)                                                      (
MODE (9)                                                                                                                                                                i N        20.402(b)                            20.405(c)                        50.73(a)(2)(Iv)                            73.71(b)        f i
d l      PcWER                                20.405(a)(1)(1)                      50.36(c)(1)                      50.73(a)(2)(v)                              73.71(c)        i LEVEL (10) l6l0      20.405(a)(1)(ti)                    50.36(c)(2)                      50.73(a)(2)(vil)                            OTHER:
l
                                                                                                                                                                                }
          ..................                  20.405(a)(1)(iii)                X  50.73(a)(2)(i)                    50.73(a)(2)(viii)(A)
{
          ..................                  20.405(a)(1)(iv)                X  50.73(a)(2)(ll)                  50.73(a)(2)(vill)(s)                                        i
          ..................                  20.405(a)(1)(v)                      50.73(a)(2)(lli)                50.73(a)(2)(x) 5 LICENSEE CONTACT FOR THIS LER (12) i NAME                                                                                                                                          TELEPHONE NO.
l AREA
:                                                                                                                                                  CODE ROBERT J. WANCZYK, PLANT MANAGER 8l0l2 2l5l7l-l7l7l1l1 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)                                                                      !
CAUSE      SYST          COMPONENT            MFR                REPORTABLE        CAUSE  SYST          COMPONENT                MFR        REPORTABLE TO NPRDS  ....                                                                  TO NPRDS    .... l B
AlA            lFl5lV Al4l9l9                                Y    .... NA l            l        l  l        l  l  l l
          "a F                        l          l    II          IIi                                        "a i            i          ll              II                          :
SUPPLEMENTAL REPORT EXPECTED (14)                                        EXPECTED                                            M0  DAY YR  -l SUBMISSION                                                          ;
DATE (15)                                                          ;
X      YES (If yes, conplete EXPECTED SUBMIS$10N DATE)                            No 0l7 1l5 9l3 l      ABSTRACT (Limit to 1400 spaces, i.e., approx. fifteen single-space typewritten lines) (16)                                                                                I On 4/6/93, following Control Rod Drive scram time testing, it was concluded that the core average scram time and the                                          <
b      scram times of seven (7) of the 2X2 control rod arrays at notch forty-six (46) were n0t in compliance with Technical Specifications (TS) Section 3.3.C. On 4/6/93, the plant was shutdown due to an unrelated minor leak in the Feedwater :                                                    ;
(
System. Subsequent follow-up investigation into past scram time testing revealed that on 10/15/92, initial scram times for one                                            l of the 2X2 arrays, at notch forty-six (46), would not have been in compliance with TS if the *as found" scram time data were                                              j used instead of the *as left* scram time data.                                                                                                                            '
The apparent cause of the slow scram times is attributable to component parts of the Scram Solenoid Pilot Valves.                                              l The apparent cause for the failure to comply with TS on 10/15/92 is the use of *as left* data instead of *as found" data. The root cause analyses for these events are in progress and will be addressed in a supplemental LER.
Following the 4/6/93 shutdown, immediate corrective actions were to rebuild the Scram Solenoid Pilot Valves to address the slow scram times, and to no longer allow the use of repeated scrams to determine TS compliance. Other corrective actions included forming a task team to investigate the slow scram times, and a task team to investigate possible programmatic issues associated with the everit.
CRC Torin 366 (6-89)                                                                                                                                                                -1
                                                                                                                                                                                .I
                                                                                                                                                                                    \
 
r
              .      CRC Fcre 366A U.S. NUCLEAR REGULATORY CapetIS$10N                                APPROVED OMS No. 3150-0104                        ,
(6-89)                                                                                EMPIRES 4/30/92 ESTIM TED BURDEN PER RESPONSE TO COMPLY UITH THis INFORM TION COLLECTION REQUEST: 50.0 HRS. FORWARD
                      ,        LICENSEE EVENT REPORT (LER)                            COMMENTS REGARDING BURDEN ESTIETE TO THE RECORDS AND              [
TEXT CONTINUATION                                    REPORTS MNAGEMENT SRANCH (P-350), U.S. NUCLEAR REGULAt0RY        !
COMNISSION, WASHINGTON DC 20555, AND TO THE PAPERWORK            {
REDUCTION PROJECT (3160-0104), OFFICE oF MWAGEMENT AND            j BLOGET, WASHINGTON, DC 20603.                                    .
i FACILITY NAME (1)                                    DOCKET No (2)                LER NUMBER (6)                PAGE (3)
YEAR          SEQ #        REV #                          f i
9    3          0          0              of VERMONT YANKEE NUCLEAR POWER CoRPORAT]DN                                            0      5          0 0l2          0l4 0l5l0l0l0l2l7l1                                                                l TEXT (if more space is required, use additional NRC Form 366A) (17)                                                                      I i
DESCRIPTION l
i On 4/6/93, following Control Rod Drive (El:S = AA) scram time testing, it was concluded that the core average      !
scram time and the scram times of seven (7) of the 2X2 control rod arrays, at notch forty-six (46) (*as found"), were not in            ;
compliance with TS Section 3.3.C scram time limits. During the course of the 4/6/93 testing, certain control rods were                  2 immediately retested and all scram times met the TS requirements. The NRC subsequently granted an Enforcement Discretion                l for 48 hours, beginning at 2200 hours on 4/6/93, to preclude a plant shutdown as required by TS. The 48 hour Enforcement                ;
,              Discretion was based on the fact that a new analysis had concluded that a scram time of 0.5 seconds, at notch forty-six (46),            [
still enveloped the worst case transient which is a turbine trip without bypass valves. On 4/6/93 at 2233 hours, a plant                !
shutdown was initiated due to a minor leak in the Feedwater System. Subseouent follow-up investigation into past scram time              l testing revealed that on 10/15/92 initial scram time (*as found" data) for one of the 2X2 arrays, at notch forty-six (46), was          ;
not in compliance with TS. The plant did not shutdown as required by TS Section 3.3.F. The control rods in the 2X2 array had          .;
been immediately retested and subsequent scram times ("as left* data ) were within the applicable TS Limits. In the past,                !
Vermont Yankee's practice has been to allow scram time retest data (*as left* data) to determine compliance with TS. The                l practice of using reteEt data to determine TS compliance has been discontinued.                                                          j Following the determination of the slow scram times, a multi-discipline Task Force was formed of plant individuals from Reactor Engineering, instrument & Control, Mechanical Maintenance, Operations, a lead systems engineer for Control Rod Drive            ,
Systems from the General Electric Co., as well as a representative from the Automatic Switch Co. to investigate the slow                ,
scram times and determine the root cause and subsequent necessary repairs. This included a sub-task force to acquire physical            ;
data from the Scram Solenoid Pilot Valve components. A second Task Force was also formed of Yankee Nuclear Service                      ?
Division personnel to investigate any programmatic issues associated with the event.
                                                                                                                                                        ?
CAUSE OF EVENT
{
i The apparent cause of the slow scram times is attributable to the Scram Solenoid Pilot Valves. Further investigation          j into the component parts of the solenoid is ongoing to determine +.he root cause for the slow scram times. The sub-task force            ;
4 team assigned to acquire the physical data could not determine the root cause based on the scram solenoid pilot valve                    !
components with test equipment at their disposal. Subsequently, the used component parts were sent to General Electric for            j further testing. The root cause will be addressed in a supplemental LER.
                                                                                                                                                      'l The investigation into the root cause for using *as left* data instead of *as found" data and compliance with TS is            j ongoing and will also be addressed in a supplemental LER.                                                                                i 1
ANALYSIS OF EVENT
                                                                                                                                                      -{
The design basis of the Reactivity Control System is to provide sufficient nuclear reactivity control devices (control .      l rods) to control the excess reactivity in the core and to provide for adjustment of the control rods to permit power generation.        !
The safety function of the Reactivity Contro! System, that applies to this event, is to provide sufficient rapid insertion of control    ;
rods so that no fuel damage results from any abnormal operating transient.                                                              !
The limiting design transient for this event is a turbine trip without bypass valves.' This event was analyzed by the ,
Yankee Nuclear Services Transient Analysis Group using times that exceeded the TS limits. Although the scram times on -              1 4/6/93 were not initially in compliance with TS, (core averaoe notch 46 time was 0.369 seconds (TS limit of 0.358 seconds)              !
and seven of the sixty-eight 2X2 arrays were in the range of 0.380 to 0.418 seconds (TS limit of 0.379 seconds)), the                    !
conclusion of the analysis is that no present cycle operating limits would be affected if the notch 46 scram time was 0.5                i seconds or less. Additionally, the scram time on 10/15/92 for the one 2X2 array that was not in compliance with TS was                  ?
0.391 seconds, however, this scram time is also enveloped by the conclusion of the analysis.                                            E i
i NRC Form 366 (6-89)
 
1
  . NRC.Ftra 366A U.S. NUCLEAR REGULATORY C0mlSSloN                                    APPROVED OMS No. 3150-0104                    l (6-89)                                                                                  EXPIRES 4/30/92                          j ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS            !
INFORMATION COLLECT 10W REouEST: 50.0 HRS. FORWARD            l 11CENSEE EVENT REPORT (LER)                                ComENTS REGARD!bG BURDEN ESTIMATE TO THE RECORDS AND          l TEXT CONTINUATION                                      REPORTS MANAGEMENT BRANCH (P-350), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON DC 20555, AND TO THE PAPERWORK        l REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND      !
BUoGET, WASHINGTON, DC 20603.                                ;
FACILITY KAME (1)                                        DOCKET No (2)              LER NtMBER (6)                  PAGE (3)      l YFAR          SEQ #          REV #
                                                                                                                                          )
VERMONT YANKEE WuCLEAR POWER CORPORATION                                  9    3          0                0 0                0 0l3          0l4 0l5l0l0j0l2l7l1                        5    -
OF TEXT (if more space is required, use additional NRC Form 366A) (17)
The 4/6/93 testing was conducted when the plant was at approximately 60% power. During the evaluation of the scram times the plant was held less than 75% power. The above analysis took into account the operating limits at 100%
power.
As the scram times were enveloped by the analyzed times of 0.5 seconds, no safety consequences would have resulted from the as-found scram insertion times for any operational transients.                                                    l Prior to startup, all Scram Solenoid Pilot Valves were rebuilt and the control rods were subsequently retested with scram times within the TS scram time limits.
At no time was there any threat to the health and safety of the public.
CORRECTIVE ACTIONS Immediate Corrective Actions
: 1.      Following the 4/6/93 testing, the data was evaluated to assess the safety significance of the event and discussions were initiated with the NRC concerning Enforcement Discretion.
Intermediate Corrective Actions
: 1.      Following the plant shutdown for the minor leak in the feedwater system, the immediate actions were as follows:
: a.      Two tasks teams were formed, one to evaluate the slow scram times, and one to investigate possible programmatic issues associated with failure to comply with TS. A sub-task team was also formed to specifically investigate the physical condition of the Scram Solenoid Pilot Valve components to determine the root cause and review previous test data.
: b.        All 178 Scram Solenoid Pilot Valves were rebuilt with new component parts prior to plant startup.
: 2.      Cold hydrostatic tests of all 89 control rods were performed to ensure full compliance with TS.
: 3.      Following plant startup, single rod scram testing was performed on 100% of the rods. Using *as found" data, the results were within TS lamits.
4      The removed component parts of several of the Scram Solenoid Pilot Velves were sent to General Electric for further analysis to identify the root cause for the slow scram times.
5,      A memo was issued from the Plant Manager requiring all departments involved in TS surveillances to evaluate their current assessment practice to ensure margins to limits are monitored and maintained.
: 6.      An interim change to the Control Rod Scram Testing and Data Reduction procedure was made prior to startup to ensure compliance with TS.
NRC Forn 366 (6 89)
 
WRC Form 366A U.S. NUCLEAR REGULA70RY CopMISSION                              APPROVED OMS NO. 3150-0104 (6-89)                                                                            EXPIRES 6/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THis INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER)                            COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND TEXT CONTlWUATION                                  REPORTS MANAGEMENT BRANCH (P-350), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.
FACILITY NAME (1)                                    DOCKET No (2)            LER NUMBER (6)                  PAGE (3)
YEAR          SEQ #          REV #
or UERMoNT YANKEE NUCLEAR POWER CORPORATION                              9    3 -
0  0  5        0  0 0l4          0l4 0l5l0l0l0l2l7l1 TEXT (If more space is required, use additional NRC Form 366A) (17) a Lona Term Corrective Actions
: 1.      Vermont Yankee will develop an enhanced trending program for scram times and develop indicators to provide predictive maintenance.
: 2.      Prior to the next rod pattern exchange, which is expected to occur in June 1993, the Control Rod Scram Testing and Data Reduction Procedure will be revised to ensure management expectations are met.
: 3.      During the next rod pattern exchange scheduled for June, 50% of the control rod drives will be tested to gather further data associated with Control Rod Drive performance.
: 4.      Corrective Action Reports (CAR's) will be generated in accordance with Vermont Yankee's Corrective Action Program. This willinclude an assessment of any potential changes or enhancements to TS.
The scheduled date for completing the Corrective Action reports is 7/15/93.
: 5.      A Nuclear Network entry will be made summarizing this event.
ADDITIONAL INFORMATION No similar events have been reported to the Commission in the last five years.
The Scram Solenoid Pilot Valves that were rebuilt are ASCO Model HVA 90-405-2A (EliS=FSV) r t
I WRC Form 366                                                                                                                  r (6-89)
A}}

Latest revision as of 02:02, 15 March 2020

Redirect to:

Retrieved from "https://kanterella.com/w/index.php?title=ML20056C224&oldid=2595102"