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| number = ML20236P011
| number = ML20236P011
| issue date = 07/10/1998
| issue date = 07/10/1998
| title = Insp Repts 50-282/98-10 & 50-306/98-10 on 980605-12. Violations Noted.Major Areas inspected:on-site Insp Into Circumstances Surrounding Unit 1 Rt Due to Dropped CR & Actions Taken for Recovery to Safe Shutdown on 980605
| title = Insp Repts 50-282/98-10 & 50-306/98-10 on 980605-12. Violations Noted.Major Areas inspected:on-site Insp Into Circumstances Surrounding Unit 1 RT Due to Dropped CR & Actions Taken for Recovery to Safe Shutdown on 980605
| author name =  
| author name =  
| author affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
| author affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
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                                                                                  U.S. NUCLEAR REGULATORY COMMISSION
. _ _
                                                                                                  REGIONlli                                                         .
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_ _ _ - -
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U.S. NUCLEAR REGULATORY COMMISSION
REGIONlli
.
Docket Nos:
50-282;50-306
,
,
                                                                        Docket Nos:         50-282;50-306
License Nos:
                                                                        License Nos:        DPR-42; DPR-60
DPR-42; DPR-60
                                                                                                                                                                      1
1
                                                                        Report Nos:         50-282/98010(DRS); 50-306/98010(DRS)
Report Nos:
                                                                        Licensee:           Northem States Power Company
50-282/98010(DRS); 50-306/98010(DRS)
                                                                        Facility:           Prairie Island Nuclear Generating Plant
Licensee:
                                                                        Location:           1717 Wakonade Drive East                                                 ,
Northem States Power Company
                                                                                            Welch, MN 55089                                                           l
Facility:
                                                                                                                                                                      1
Prairie Island Nuclear Generating Plant
                                                                                                                                                                      i
Location:
                                                                        Dates:             June 5 through 12,1998
1717 Wakonade Drive East
                                                                        Inspectors:         M. Bielby, Reactor Engineer / Team Leader
,
                                                                                            S. Ray, Senior Resident inspector, Prairie Island
Welch, MN 55089
                                                                                            R. Winter, Reactor Engineer
l
                                                                        ~ Approved by:       M. Leach, Chief, Operator Licensing Branch                               ;
i
                                                                                            Division of Reactor Safety
Dates:
                                                                                                                                                                        '
June 5 through 12,1998
                                                                                                                                                                      !
Inspectors:
                                                                                                                                                                      :
M. Bielby, Reactor Engineer / Team Leader
                                                                                                                                                                      1
S. Ray, Senior Resident inspector, Prairie Island
                                                                                                                                                                      i
R. Winter, Reactor Engineer
~ Approved by:
M. Leach, Chief, Operator Licensing Branch
Division of Reactor Safety
'
1
i
!
!
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I
                                                                                        ~
~
        9907160111 990710
9907160111 990710
        PDR                             ADOCK 05000282
PDR
!.     G                                                                   PDR                                                                                       l.
ADOCK 05000282
  .
!.
G
PDR
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I
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                ______                                       _             - _____.                           . - - . .-
______
    .
_
  ,
- _____.
                                                      EXECUTIVE SUMMARY
. - - .
                                    Prairie Island Nuclear Generating Station, Unit 1 and Unit 2
.-
                                      NRC Inspection Reports 50-282/98010; 50-306/98010
.
        This special inspection report covers a period of on-site inspection into the circumstances
,
        surrounding the Unit i reactor trip due to a dropped control rod and the actions taken for the
EXECUTIVE SUMMARY
        recovery to safe shutdown conditions on June 5,1998. The conduct of operations of the Prairie
Prairie Island Nuclear Generating Station, Unit 1 and Unit 2
        Island staff for this event generally was good during the initial stages of the event; however, the
NRC Inspection Reports 50-282/98010; 50-306/98010
        inspectors noted some equipment problems, and weaknesses in procedures, communications,
This special inspection report covers a period of on-site inspection into the circumstances
        training, and performance.
surrounding the Unit i reactor trip due to a dropped control rod and the actions taken for the
        Ooerations
recovery to safe shutdown conditions on June 5,1998. The conduct of operations of the Prairie
        .
Island staff for this event generally was good during the initial stages of the event; however, the
                      The operator's initial response and actions taken based on indications for the dropped
inspectors noted some equipment problems, and weaknesses in procedures, communications,
                        rod event were good; however, subsequent operator actions to stabilize the plant and
training, and performance.
                      dissipate decay heat were not completely effective as evidenced by the inadvertent rise
Ooerations
                        in Tave and lifting of the steam generator (SG) #1 A safety valve. (Sections 01.1 and
The operator's initial response and actions taken based on indications for the dropped
                      04.1)
.
      .
rod event were good; however, subsequent operator actions to stabilize the plant and
                      The operators lacked adequate procedural guidance for stabilizing the plant and
dissipate decay heat were not completely effective as evidenced by the inadvertent rise
                      dissipating decay heat by dumping steam using the SG power operated relief valves
in Tave and lifting of the steam generator (SG) #1 A safety valve. (Sections 01.1 and
                      (PORVs) during a hot shutdown condition with main steam isolation valves (MSIVs)
04.1)
                      closed. A violation of 10 CFR Part 50, Appendix B, Criterion V was issued. (Sections
The operators lacked adequate procedural guidance for stabilizing the plant and
                      O3.1 and 04.1)
.
      .
dissipating decay heat by dumping steam using the SG power operated relief valves
                      During subsequent actions to stabilize the plant, a lack of three part communication, a
(PORVs) during a hot shutdown condition with main steam isolation valves (MSIVs)
                      lack of consistent plant oversight, and unfamiliarity of SG PORV response contributed to
closed. A violation of 10 CFR Part 50, Appendix B, Criterion V was issued. (Sections
                      failure to adequately remove decay heat. (Section 04.1)
O3.1 and 04.1)
      .
During subsequent actions to stabilize the plant, a lack of three part communication, a
                      Operator training and practical experience at maintaining the plant in a hot shutdown
.
                      condition with the MSIVs closed and using SG PORVs for decay heat dissipation was
lack of consistent plant oversight, and unfamiliarity of SG PORV response contributed to
                      limited. (Sections 04.1 and 05.1)
failure to adequately remove decay heat. (Section 04.1)
      .
Operator training and practical experience at maintaining the plant in a hot shutdown
                      The simulator SG PORV fidelity was dissimilar to the plant and the licensee wrote a non-
.
                      conformance report. (Section O5.1)
condition with the MSIVs closed and using SG PORVs for decay heat dissipation was
                                                                2
limited. (Sections 04.1 and 05.1)
..           ___           -
The simulator SG PORV fidelity was dissimilar to the plant and the licensee wrote a non-
.
conformance report. (Section O5.1)
2
..
___
-


                      ___     ._ .__         _                 _ _ _ _ . __     _ _ _ _ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _
___
  .
._
                                                                                                                          :
.__
                                                                                                                          l
_
                                                  Report Detalls
_ _ _ _ . __
                                                                                                                          '
_ _ _ _ _ _ _ _ _ _ _
    Brief Narrative of the Rod Droo Event                                                                                 l
._
_ _ _ _ _ _ _
.
:
'
Report Detalls
Brief Narrative of the Rod Droo Event
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l
    The Unit i reactor was operating at 100% power on June 5,1998, and experienced an
The Unit i reactor was operating at 100% power on June 5,1998, and experienced an
    unexpected automatic trip. The operators verified all control rods fully inserted and identified
unexpected automatic trip. The operators verified all control rods fully inserted and identified
    that the first out indication was a negative flux-rate trip. The control room received reports of
that the first out indication was a negative flux-rate trip. The control room received reports of
    steam release in the turbine building (TB) that was later identified as an unexpected relief valve
steam release in the turbine building (TB) that was later identified as an unexpected relief valve
    lift on the 15A feedwater heater (FWH). One of the two operating main feedwater pumps
lift on the 15A feedwater heater (FWH). One of the two operating main feedwater pumps
    (MFPs) tripped, as expected, and operators tripped the remaining MFP to minimize secondary
(MFPs) tripped, as expected, and operators tripped the remaining MFP to minimize secondary
    inventory loss. This action reseated the lifted FWH relief valve. The operators used the                             3
inventory loss. This action reseated the lifted FWH relief valve. The operators used the
    atmospheric steam dumps to initially remove decay heat. Operators closed the MSIVs as a                               l
3
    result of excessive reactor coolant system (RCS) cooldown and in response to the report of
atmospheric steam dumps to initially remove decay heat. Operators closed the MSIVs as a
    steam in the TB. Both the #11 turbine driven auxiliary feedwater (TDAFW) and #12 motor
result of excessive reactor coolant system (RCS) cooldown and in response to the report of
    driven auxiliary feedwater (MDAFW) pumps automatically started and remained in service to
steam in the TB. Both the #11 turbine driven auxiliary feedwater (TDAFW) and #12 motor
    supply auxiliary feedwater (AFW) to both SGs. One control room operator was dedicated to
driven auxiliary feedwater (MDAFW) pumps automatically started and remained in service to
    maintain both SG water levels 35% - 37% as indicated on narrow range (NR) meters.                                     l
supply auxiliary feedwater (AFW) to both SGs. One control room operator was dedicated to
    Approximately two hours after efforts to stabilize the plant, one of the five SG "A" main steam
maintain both SG water levels 35% - 37% as indicated on narrow range (NR) meters.
    safety valves (#1 A) unexpectedly lifted and reseated. The resulting swell caused indicated NR
Approximately two hours after efforts to stabilize the plant, one of the five SG "A" main steam
    level in SG "A" to increase to 50%, and SG "B" to 45%, respectively. The licensee later
safety valves (#1 A) unexpectedly lifted and reseated. The resulting swell caused indicated NR
    identified that the operator had placed both SG PORVs in the manual mode just prior to the
level in SG "A" to increase to 50%, and SG "B" to 45%, respectively. The licensee later
    unexpected SG main steam safety valve lift.
identified that the operator had placed both SG PORVs in the manual mode just prior to the
                                                  l. Operations
unexpected SG main steam safety valve lift.
    01       Conduct of Operations
l. Operations
    O1.1 Seouence of Events
01
      a.     Insoection Scoce (71707. 93702)
Conduct of Operations
            The inspectors formulated a sequence of events based on the following information:
O1.1 Seouence of Events
              interviews conducted with the licensee's management, operations and engineering staff;
a.
              review of operator logs, parameter recorders, process computer and Emergency
Insoection Scoce (71707. 93702)
              Response Computer System (ERCS) information; and observation of control room
The inspectors formulated a sequence of events based on the following information:
l             panels,
interviews conducted with the licensee's management, operations and engineering staff;
      b.     Observations and Findinos
review of operator logs, parameter recorders, process computer and Emergency
            The following information describes the sequence of events (Central Daylight Time)
Response Computer System (ERCS) information; and observation of control room
i            commencing with the automatic reactor trip of Unit 1 from 100% power as reconstructed
l
l             by the NRC inspection team:
panels,
                                                        3
b.
Observations and Findinos
The following information describes the sequence of events (Central Daylight Time)
commencing with the automatic reactor trip of Unit 1 from 100% power as reconstructed
i
l
by the NRC inspection team:
3
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                                                          ___     .
___
    *
.
                                                                                                          \
\\
  d'                                                                                                     i
*
        Fridav. June 5.1998
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                                                                                                          1
i
        06:58 pm     Unit 1 received an automatic reactor trip, operators identified the first out     i
Fridav. June 5.1998
                      annunciator as the negative flux rate trip. Operators entered 1E-0, * Reactor Trip
06:58 pm
                      Or Safety injection," Revision 17. Operators verified all control rods fully       ,
Unit 1 received an automatic reactor trip, operators identified the first out
                      inserted, one of two operating MFPs (#11) received automatic trip, #11 TDAFW       l
i
                      and #12 MDAFW pumps started automatically with discharge flow at 550 gpm.
annunciator as the negative flux rate trip. Operators entered 1E-0, * Reactor Trip
,                     Average RCS temperature (Tave) dropped from 559 to 539 'F, and SG levels
Or Safety injection," Revision 17. Operators verified all control rods fully
i                     dropped from 45% to 0% NR.
,
        07:01 -
inserted, one of two operating MFPs (#11) received automatic trip, #11 TDAFW
l       07:04 pm     Tave continued to drop to 538 'F, control room received Zone 15 TB fire alarm
and #12 MDAFW pumps started automatically with discharge flow at 550 gpm.
                      and report of steam release in the TB. Operators completed Ugcedure 1E-0 and
,
                      entered 1ES-0.1, Reactor Trip Recovery, Revision 13. AFW tiow was throttled to
Average RCS temperature (Tave) dropped from 559 to 539 'F, and SG levels
i
dropped from 45% to 0% NR.
07:01 -
l
07:04 pm
Tave continued to drop to 538 'F, control room received Zone 15 TB fire alarm
and report of steam release in the TB. Operators completed Ugcedure 1E-0 and
entered 1ES-0.1, Reactor Trip Recovery, Revision 13. AFW tiow was throttled to
l
l
200 gpm to limit cooldown, MSIVs closed to limit cooldown and stop steam
'
'
                      200 gpm to limit cooldown, MSIVs closed to limit cooldown and stop steam
release.
                      release.
07:07 -
        07:07 -
. 07:15 pm
      . 07:15 pm     Operators received report that steam was due to the lift of the 15A FWH tube
Operators received report that steam was due to the lift of the 15A FWH tube
                      side relief. Operators stopped the running #12 MFP and condensate pump to
side relief. Operators stopped the running #12 MFP and condensate pump to
                      minimize secondary inventory loss and reduce 15A FWH tube side pressure.
minimize secondary inventory loss and reduce 15A FWH tube side pressure.
                      The lifted 15A FWH relief closed, Tave increased to 547 'F, and continued to
The lifted 15A FWH relief closed, Tave increased to 547 'F, and continued to
                      rise.
rise.
        07:17 pm     AFW flow was increased to 270 gpm.                                                 i
07:17 pm
                                                                                                          i
AFW flow was increased to 270 gpm.
        07:19 pm     Tave at 555 *F, SG steam pressure at 1050 psig (SG PORV setpoint) and both
i
                      PORVs automatically opened.
i
        07:45 pm     SG levels at 10% and continued to rise.
07:19 pm
        07:53 pm       12 SG PORV setpoint dialed down in automatic to open valve more and reduce       ;
Tave at 555 *F, SG steam pressure at 1050 psig (SG PORV setpoint) and both
                      pressure. However, opening 12 SG PORV caused 11 SG PORV to close and
PORVs automatically opened.
                      cycle.
07:45 pm
        08:08 pm     SG level approached normal band of 33 +/- 5%; however, AFW flow throttled to       l
SG levels at 10% and continued to rise.
                      60 gpm and caused SG level to decrease from 30% to 25% over the next four
07:53 pm
                      - minutes.
12 SG PORV setpoint dialed down in automatic to open valve more and reduce
        08:10 pm       11 SG PORV setpoint dialed down in automatic, caused valve to open more and       I
;
                                                                                                          '
pressure. However, opening 12 SG PORV caused 11 SG PORV to close and
                      reduce pressure.
cycle.
        08:12 -
08:08 pm
        08:24 pm     AFW flow increased to 200 gpm in several steps, SG levels at 25% and started
SG level approached normal band of 33 +/- 5%; however, AFW flow throttled to
                      to increase again.
60 gpm and caused SG level to decrease from 30% to 25% over the next four
                                                                                                          l
- minutes.
                                                        4
08:10 pm
11 SG PORV setpoint dialed down in automatic, caused valve to open more and
'
reduce pressure.
08:12 -
08:24 pm
AFW flow increased to 200 gpm in several steps, SG levels at 25% and started
to increase again.
4


                                                                            _ _ _ _ _____ _ _           ____
_ _ _ _
    :
_____ _ _
  ,
____
      08:45-
:
      09:04 pm       SG levels approached normal band of 33 +/- 5%, AFW flow throttled down to 50
,
                    gpm in several steps. SG levels continued to rise slowly from 33% to 36%.
08:45-
                      During this period it appeared that the operator decreased the SG PORV
09:04 pm
                    automatic setpoints in an attempt to open the PORVs more and reduce SG
SG levels approached normal band of 33 +/- 5%, AFW flow throttled down to 50
                      pressure. On the average, SG PORVs swung open and closed 10-15% while
gpm in several steps. SG levels continued to rise slowly from 33% to 36%.
                    the controller output changed 30-40%. SG levels shrank and swelled
During this period it appeared that the operator decreased the SG PORV
                      approximately +/- 2% while the overall level slowly increased toward the
automatic setpoints in an attempt to open the PORVs more and reduce SG
                    administrative procedurallimit of 38%.
pressure. On the average, SG PORVs swung open and closed 10-15% while
      NOTE:         At 09:03 pm both SG PORV setpoints appeared to have been increased while in
the controller output changed 30-40%. SG levels shrank and swelled
                    automatic which closed the valves more and reduced the level swells. However,             l
approximately +/- 2% while the overall level slowly increased toward the
                      the decay heat removal was decreased which caused Tave to start increasing
administrative procedurallimit of 38%.
                    from 552 *F.
NOTE:
      09:07 pm       Both SG PORVs placed in manual with "11" at approximately 22% demand, and
At 09:03 pm both SG PORV setpoints appeared to have been increased while in
                    "12" at 28%. The manual SG PORV demand was considerably less than when                   !
automatic which closed the valves more and reduced the level swells. However,
                      in automatic which closed the valves more and caused Tave to increase rapidly
l
                    from 553 *F.
the decay heat removal was decreased which caused Tave to start increasing
      09:12 pm       Tave at 557 'F, SG steam 9. essure at 1070 psig and one (#1 A) of five main               i
from 552 *F.
                      steam safety valves on "A" SG lifted and reseated which swelled the "A" SG level         '
09:07 pm
                    from 37% to 50%, and the "B" SG level to 45%.
Both SG PORVs placed in manual with "11" at approximately 22% demand, and
                                                                                                              i
"12" at 28%. The manual SG PORV demand was considerably less than when
      09:16 pm       Tave bottomed out at 547 'F due to the SG safety valve lifting and reciosing, and         !
!
                    then started to rise again.
in automatic which closed the valves more and caused Tave to increase rapidly
                                                                                                              l
from 553 *F.
                                                                                                              '
09:12 pm
      09:24 pm       Tave at 555 *F, both SG PORVs retumed to automatic mode and rapidly opened
Tave at 557 'F, SG steam 9. essure at 1070 psig and one (#1 A) of five main
                      and closed when SG steam pressure was greater than the PORV setpoint (1050
i
                      psig).12 SG level briefly swelled from 38% to 45%.
steam safety valves on "A" SG lifted and reseated which swelled the "A" SG level
      09:25 -
'
      11:00 pm       Plant stabilized and slowly brought to normal hot shutdown conditions. Plant
from 37% to 50%, and the "B" SG level to 45%.
                      staff investigating failure of 86G relay to lockout generator output breakers, lack
i
                      of procedural guidance in 1ES-0.1 to bypass a recently installed backup synch
09:16 pm
                      check relay to allow reclosing the generator output breakers, cause of the
Tave bottomed out at 547 'F due to the SG safety valve lifting and reciosing, and
j                     automatic reactor trip, and unexpected lifting of the 15A FWH relief valve.
!
      c.     Conclusions
then started to rise again.
              The operators' initial response and actions taken based on indications for the dropped
l
              rod event were good; however, subsequent operator actions to stabilize the plant and
'
              dissipate decay heat were not completely effective as evidenced by the inadvertent rise
09:24 pm
              in Tave and lifting of the SG #1 A safety valve.
Tave at 555 *F, both SG PORVs retumed to automatic mode and rapidly opened
                                                          5
and closed when SG steam pressure was greater than the PORV setpoint (1050
psig).12 SG level briefly swelled from 38% to 45%.
09:25 -
11:00 pm
Plant stabilized and slowly brought to normal hot shutdown conditions. Plant
staff investigating failure of 86G relay to lockout generator output breakers, lack
of procedural guidance in 1ES-0.1 to bypass a recently installed backup synch
check relay to allow reclosing the generator output breakers, cause of the
j
automatic reactor trip, and unexpected lifting of the 15A FWH relief valve.
c.
Conclusions
The operators' initial response and actions taken based on indications for the dropped
rod event were good; however, subsequent operator actions to stabilize the plant and
dissipate decay heat were not completely effective as evidenced by the inadvertent rise
in Tave and lifting of the SG #1 A safety valve.
5


  - _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ - _ _ , _ _ _ _ _ _ _ _ _                                               _   _                               ._.     ._     _ _
- _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ - _ _ , _ _ _ _ _ _ _ _ _
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._.
                                                                                                                                                                          l
._
_
_
i
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^
l
I
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                                                                                                                                                                          I
l
l                                                                                                                                                                        1
1
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                                                                                                                                                                          l
03
                                                                    03    Operations Procedures and Documentation
Operations Procedures and Documentation
                                                                    O3.1 Lack of Guidance for Dumoina Steam Usino SG PORVs
O3.1 Lack of Guidance for Dumoina Steam Usino SG PORVs
1
1
                                                                    a.   Insoection Scoce (71707. 93702)
a.
                                                                          The inspectors performed the following to determine the adequacy of guidance for
Insoection Scoce (71707. 93702)
                                                                          dumping steam using SG PORVs: reviewed 1ES-0.1, * Reactor Trip Recovery," Revision
The inspectors performed the following to determine the adequacy of guidance for
                                                                          13; interviewed licensed operators and managernent personnel; reviewed parameter
dumping steam using SG PORVs: reviewed 1ES-0.1, * Reactor Trip Recovery," Revision
                                                                          recorders, process computer and ERCS information.
13; interviewed licensed operators and managernent personnel; reviewed parameter
                                                                    b.   Observations and Findings
recorders, process computer and ERCS information.
                                                                          The Unit 1 EOP,1ES-0.1, Step 5 (bullet under " Response Not Obtained" column)
b.
                                                                          directed the operator to " Dump steam with SG PORVs," but did not provide any further
Observations and Findings
                                                                          guidance or reference that described how to perform the evolution. During the plant
The Unit 1 EOP,1ES-0.1, Step 5 (bullet under " Response Not Obtained" column)
                                                                          stabilization phase of the reactor trip recovery, the operator was required to maintain SG
directed the operator to " Dump steam with SG PORVs," but did not provide any further
                                                                          levels 28 - 38%. The operator initially left both SG PORVs in the normal automatic
guidance or reference that described how to perform the evolution. During the plant
                                                                          configuration and was very slowly adjusting the controller pot down from the normal
stabilization phase of the reactor trip recovery, the operator was required to maintain SG
levels 28 - 38%. The operator initially left both SG PORVs in the normal automatic
configuration and was very slowly adjusting the controller pot down from the normal
.
.
                                                                          operating setpoint of 75% (1050 psig) to the no Ioad setpoint of 71.5% (1005 psig). The
operating setpoint of 75% (1050 psig) to the no Ioad setpoint of 71.5% (1005 psig). The
l                                                                         PORVs' responsiveness resulted in erratic SG level swings. In lieu of procedural
l
                                                                          guidance and with the PORV auto setpoint at approximately 74.2% (1040 psig), the lead
PORVs' responsiveness resulted in erratic SG level swings. In lieu of procedural
                                                                          reactor operator (LRO) placed both SG PORV controllers in manual to reduce the erratic
guidance and with the PORV auto setpoint at approximately 74.2% (1040 psig), the lead
                                                                          SG ievel swings and attempted to maintain SG level ! ass than the 38% administrative
reactor operator (LRO) placed both SG PORV controllers in manual to reduce the erratic
                                                                          limit by controlling AFW flow. However, the operdor failed to open the PORVs
SG ievel swings and attempted to maintain SG level ! ass than the 38% administrative
                                                                          sufficiently and the dissipation of decay heat was inadequate. As a result, Tave
limit by controlling AFW flow. However, the operdor failed to open the PORVs
                                                                          continued to increase which caused the SG pressure to increase to the 1 A SG safety
sufficiently and the dissipation of decay heat was inadequate. As a result, Tave
                                                                          valve setpoint of 1075 psig and it cycled open and close. The lack of adequate
continued to increase which caused the SG pressure to increase to the 1 A SG safety
                                                                          procedural guidance for dumping steam using SG PORVs was considered a violation of
valve setpoint of 1075 psig and it cycled open and close. The lack of adequate
                                                                          10 CFR Part 50, Appendix B, Criterion V," Instructions, Procedures, and Drawings,"(50-
procedural guidance for dumping steam using SG PORVs was considered a violation of
                                                                          282/98010-01(DRS)); (50-306/98010-01(DRS)).
10 CFR Part 50, Appendix B, Criterion V," Instructions, Procedures, and Drawings,"(50-
                                                                          Subsequent to the event, the licensee revised both unit EOPs,1ES-0.1 and 2ES-0.1, to
282/98010-01(DRS)); (50-306/98010-01(DRS)).
                                                                          direct reduction of the SG PORVs auto setpoint to 71.5% (1005 psig)if MSIVs are
Subsequent to the event, the licensee revised both unit EOPs,1ES-0.1 and 2ES-0.1, to
                                                                          closed. Additionally, the same procedures were changed to direct the operator to stop
direct reduction of the SG PORVs auto setpoint to 71.5% (1005 psig)if MSIVs are
                                                                          feed flow to a SG if level reaches 40%, vice 50%.
closed. Additionally, the same procedures were changed to direct the operator to stop
                                                                    c.   Conclusions
feed flow to a SG if level reaches 40%, vice 50%.
                                                                                                                                                                          ,
c.
                                                                          The operators lacked adequate procedural guidance for stabilizing the plant and                 !
Conclusions
                                                                                                                                                                          I
,
                                                                          dissipating decay heat by dumping steam using the SG PORVs during a hot shutdown
The operators lacked adequate procedural guidance for stabilizing the plant and
                                                                          condition with MSIVs closed. A violation of 10 CFR Part 50, Appendix B, Criterion V
I
                                                                          was issued.                                                                                     i
dissipating decay heat by dumping steam using the SG PORVs during a hot shutdown
                                                                                                                                                                          l
condition with MSIVs closed. A violation of 10 CFR Part 50, Appendix B, Criterion V
                                                                                                                                                                          1
was issued.
                                                                                                                                                                          .
i
                                                                                                                                                                          l
.
                                                                                                                                                                          i
l
                                                                                                                    6
6
                                                                                                                                                                          !
i
                                                                                                                                                                          '
'
                                                                                                                                                                    _
_


- _ - _ _ - _ - - - _ - _ _ _ - - _ _ _ _ _ _ - - - _ _ _ _ _ _ _ - _ _ _ _ _ _ _ . - _ _ .
- _ - _ _ - _ - - - _ - _ _ _ - - _ _ _ _ _ _ - - - _ _ _ _ _ _ _ - _ _ _ _ _ _ _ . - _ _ .
                            :
:
        -
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                                            04                   Operator Knowledge and Performance
04
                                            04.1 -Coerator Resoonse to Rod Droo Event
Operator Knowledge and Performance
                                                a.               Insoection Scone (71707. 93702)
04.1 -Coerator Resoonse to Rod Droo Event
                                                                The inspectors reviewed operator performance based on their initial response to the
a.
                                                                  reactor trip and mode change to hot shutdown conditions. The inspectors based their
Insoection Scone (71707. 93702)
                                                                findings on the following: Interviews conducted with operations and engineering staff;
The inspectors reviewed operator performance based on their initial response to the
                                                                  review of operator logs, parameter recorders, process computer and ERCS information;
reactor trip and mode change to hot shutdown conditions. The inspectors based their
                                                                  review of alarm response, emergency, abnormal, and normal operating procedures.
findings on the following: Interviews conducted with operations and engineering staff;
                                                b.               Observations and Findinas
review of operator logs, parameter recorders, process computer and ERCS information;
                                                                The Unit 1 control room operators' initial response to the rod drop event was good. The
review of alarm response, emergency, abnormal, and normal operating procedures.
                                                                  shift manager (SM) assumed the role of shift technical advisor (STA), the Unit 1 shift
b.
                                                                  supervisor (SS) assumed the role of emergency operating procedure (EOP) reader, the
Observations and Findinas
                                                                  Unit 1 LRO took control of the secondary plant, and the other Unit i reactor operator
The Unit 1 control room operators' initial response to the rod drop event was good. The
                                                                  (RO) took control of the primary plant. The crew correctly identified that an automatic   ,
shift manager (SM) assumed the role of shift technical advisor (STA), the Unit 1 shift
                                                                  reactor trip had occurred and promptly entered EOP 1E-0, * Reactor Trip Or Safety         l
supervisor (SS) assumed the role of emergency operating procedure (EOP) reader, the
                                                                  Injection," Revision 17. After completing the specified procedural actions, the crew     '
Unit 1 LRO took control of the secondary plant, and the other Unit i reactor operator
                                                                  correctly transitioned to 1ES-0.1, " Reactor Trip Recovery," Revision 13. The LRO
(RO) took control of the primary plant. The crew correctly identified that an automatic
                                                                  appropriately throttled AFW flow to limit cooldown. A TB fire alarm was received, and
,
                                                                  after investigating, field operators identified an unexpected steam release in the TB.   ,
reactor trip had occurred and promptly entered EOP 1E-0, * Reactor Trip Or Safety
                                                                                                                                                            '
l
                                                                  Concurrently, control room personnel identified an excessive primary cooldown based
Injection," Revision 17. After completing the specified procedural actions, the crew
                                                                  on a Tave decrease to 538 'F. The control room operators responded to the excessive      j'
'
                                                                  primary cooldown and closed the MSIVs and bypass valves. The single operating MFP
correctly transitioned to 1ES-0.1, " Reactor Trip Recovery," Revision 13. The LRO
                                                                  and condensate pump were stopped to minimize secondary inventory loss. Further
appropriately throttled AFW flow to limit cooldown. A TB fire alarm was received, and
                                                                  reports from the TB clarified the steam release had come from an unexpected lifted tube  ;
after investigating, field operators identified an unexpected steam release in the TB.
                                                                  side relief on the 15A FWH that reseated after tripping the MFP As a result of those      !
,
,
Concurrently, control room personnel identified an excessive primary cooldown based
'
on a Tave decrease to 538 'F. The control room operators responded to the excessive
j
primary cooldown and closed the MSIVs and bypass valves. The single operating MFP
'
'
                                                                  actions, Tave increased to 547 'F and continued to slowly rise. The operators attempte.,d !
and condensate pump were stopped to minimize secondary inventory loss. Further
                                                                  to stabilize the plant in a hot shutdown condition with the MSIVs closed and maintain the
reports from the TB clarified the steam release had come from an unexpected lifted tube
                                                                  following parameters as specified by 1ES-0.1: pressurizer (PRZR) pressure between
;
                                                                  2220 and 2250 psig; PRZR level between 19 and 23%; SG NR level between 30 and
side relief on the 15A FWH that reseated after tripping the MFP As a result of those
                                                                  36%; and RCS Tave between 545 and 549 'F.
!
actions, Tave increased to 547 'F and continued to slowly rise. The operators attempte.,d
!
,
'
to stabilize the plant in a hot shutdown condition with the MSIVs closed and maintain the
following parameters as specified by 1ES-0.1: pressurizer (PRZR) pressure between
2220 and 2250 psig; PRZR level between 19 and 23%; SG NR level between 30 and
36%; and RCS Tave between 545 and 549 'F.
l
l
                                                                  The crew was directed to maintain a plant condition that had not been practiced during
The crew was directed to maintain a plant condition that had not been practiced during
                                                                  simulator training. The crew had used PORVs for post accident cooldown in several
simulator training. The crew had used PORVs for post accident cooldown in several
                                                                  simulator scenarios; however, they had not maintained a hot shutdown condition with
simulator scenarios; however, they had not maintained a hot shutdown condition with
                                                                  the MSIVs closed and using SG PORVs for decay heat removal. Additionally, they
the MSIVs closed and using SG PORVs for decay heat removal. Additionally, they
                                                                  determined the plant was stabilized and transitioned from 1ES-0.1, " Reactor Trip
determined the plant was stabilized and transitioned from 1ES-0.1, " Reactor Trip
                                                                  Recovery," to 1C1.3, " Unit 1 Shutdown," Revision 40. However, even though plant
Recovery," to 1C1.3, " Unit 1 Shutdown," Revision 40. However, even though plant
                                                                  parameters were not changing rapidly, the SG levels continued to trend toward the
parameters were not changing rapidly, the SG levels continued to trend toward the
                                                                  administrative and design limits, and Tave was actually 552 'F vice the required
administrative and design limits, and Tave was actually 552 'F vice the required
                                                                  545 - 549 'F.
545 - 549 'F.
l
l
                                                                                                              7
7
1
1


    *
*
                                                                                                1
1
  ,
,
      The STA/SM and SS determined the plant was stable because they had transitioned to
The STA/SM and SS determined the plant was stable because they had transitioned to
      the shutdown procedure. Consequently they relaxed their continued oversight of the
the shutdown procedure. Consequently they relaxed their continued oversight of the
      plant status and became focused on their administrative duties. The STA observed that
plant status and became focused on their administrative duties. The STA observed that
      no critical safety functions had been entered and resumed the SM duties of notifications.
no critical safety functions had been entered and resumed the SM duties of notifications.
      Likewise, the SS focused his attention on followup of equipment problems with the FWH
Likewise, the SS focused his attention on followup of equipment problems with the FWH
      relief valve and generator output breaker relays, procedure problem with the backup
relief valve and generator output breaker relays, procedure problem with the backup
      bypass for the synch check relay, restoring the fire alarms, diagnosing the cause of the
bypass for the synch check relay, restoring the fire alarms, diagnosing the cause of the
      reactor trip, and completing logs.
reactor trip, and completing logs.
      The lack of adequate procedural guidance was a contributor to the subsequent poor
The lack of adequate procedural guidance was a contributor to the subsequent poor
      operator performance. The LRO was required to maintain SG levels 33+/-5%, and had
operator performance. The LRO was required to maintain SG levels 33+/-5%, and had
      been periodically throttling AFW flow. The LRO was also directed to dump steam with
been periodically throttling AFW flow. The LRO was also directed to dump steam with
      SG PORVs in accordance with 1ES-0.1, but was not provided with any further guidance
SG PORVs in accordance with 1ES-0.1, but was not provided with any further guidance
      that described how to perform the evolution. The LRO initially left both SG PORVs in
that described how to perform the evolution. The LRO initially left both SG PORVs in
      the normal automatic configuration and very slowly started to adjust the controller pot
the normal automatic configuration and very slowly started to adjust the controller pot
      down from the normal operating setpoint of 75% (1050 psig) to the no load setpoint of
down from the normal operating setpoint of 75% (1050 psig) to the no load setpoint of
      71.5% (1005 psig).
71.5% (1005 psig).
      The erratic response of the SG PORVs was unexpected. The LRO had very slowly
The erratic response of the SG PORVs was unexpected. The LRO had very slowly
      decreased the SG PORV setpoint to 74.2% (1040 psig). However, the PORV operation
decreased the SG PORV setpoint to 74.2% (1040 psig). However, the PORV operation
      was very responsive and wesed erratic SG level swings which was unexpected to the
was very responsive and wesed erratic SG level swings which was unexpected to the
      LRO. The PORVs opened every 5 - 10 seconds and caused SG level swell and shrink
LRO. The PORVs opened every 5 - 10 seconds and caused SG level swell and shrink
      of about 2%.
of about 2%.
      An instance of poor communications and lack of communications contributed to the
An instance of poor communications and lack of communications contributed to the
      indicated SG level exceeding the design limit, inadequate dissipation of decay heat, and
indicated SG level exceeding the design limit, inadequate dissipation of decay heat, and
      lifting of the main steam safety valve. The LRO tried to maintain both SG levels within
lifting of the main steam safety valve. The LRO tried to maintain both SG levels within
      the procedurallimits. The automatic response of the PORVs and erratic SG level
the procedurallimits. The automatic response of the PORVs and erratic SG level
      swings were unexpected. The LRO stated he made a verbal announcement that he
swings were unexpected. The LRO stated he made a verbal announcement that he
      was placing the SG PORVs in manual; however, no acknowledgment was made by any
was placing the SG PORVs in manual; however, no acknowledgment was made by any
      of the other control room operators. As such the communications were not in
of the other control room operators. As such the communications were not in
      accordance with Section Work Instruction (SWI) O-24, " Operation Section
accordance with Section Work Instruction (SWI) O-24, " Operation Section
      Communications," Revision 4. When one SG level approached the 38% limit the LRO
Communications," Revision 4. When one SG level approached the 38% limit the LRO
      placed both SG PORVs in manual with each PORV approximately 50% open. The
placed both SG PORVs in manual with each PORV approximately 50% open. The
      operator decreased AFW flow to maintain SG levelless than the 38% limit. The PORVs
operator decreased AFW flow to maintain SG levelless than the 38% limit. The PORVs
      were insufficiently opened to dissipate the decay heat and Tave continued to increase
were insufficiently opened to dissipate the decay heat and Tave continued to increase
      which caused the SG pressure to increase to the 1 A SG safety valve setpoint of 1075
which caused the SG pressure to increase to the 1 A SG safety valve setpoint of 1075
      psig, and it cycled open and close. The cycling of the safety valve resulted in a large
psig, and it cycled open and close. The cycling of the safety valve resulted in a large
      SG swell to 45-50% which alerted the SS. The LRO informed the SS that both SG
SG swell to 45-50% which alerted the SS. The LRO informed the SS that both SG
      PORVs were in manual. The SS checked safety valve tailpipe temperatures and
PORVs were in manual. The SS checked safety valve tailpipe temperatures and
      determined the 1A safety on 11 SG had cycled. Teve decreased to a minimum of 547 *F
determined the 1A safety on 11 SG had cycled. Teve decreased to a minimum of 547 *F
      due to the open safety valve. The LRO returned the SG PORV control to automatic
due to the open safety valve. The LRO returned the SG PORV control to automatic
      within about 12 minutes at which time the PORVs briefly cycled because steam
within about 12 minutes at which time the PORVs briefly cycled because steam
l     pressure was greater than 1050 psig. The plant was stabilized and in hot shutdown
l
l     conditions within about another 30 minutes.
pressure was greater than 1050 psig. The plant was stabilized and in hot shutdown
                                                8
l
conditions within about another 30 minutes.
8
l
l


                                                                  _.             - - _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _
_.
- - _ _ _ _ _ _ _ _ _ _ _ _ -
_ _ _ _ _ _ _
-
-
  c.   Conclusions
c.
        During subsequent actions to stabilize the plant a lack of three part communication, lack
Conclusions
        of consistent plant oversight, and unfamiliarity of SG PORV response contributed to
During subsequent actions to stabilize the plant a lack of three part communication, lack
        failure to adequately remove decay heat.
of consistent plant oversight, and unfamiliarity of SG PORV response contributed to
  05   Operator Training and Qualification
failure to adequately remove decay heat.
  05.1 SG Level / SG PORV / Hot Shutdown With MSIVs Closed                                                                   i
05
  a.   Insoection Scoce (71707. 93702)
Operator Training and Qualification
        The inspectors interviewed training and operations staff and management, and
05.1 SG Level / SG PORV / Hot Shutdown With MSIVs Closed
        observed a scenario run under hot shutdown conditions with MSIVs closed.
i
  b.   Observations and Findinos
a.
        The inspectors requested the training staff to run a scenario under hot shutdown
Insoection Scoce (71707. 93702)
        conditions with MSIVs closed to observe operation of the SG PORVs and resulting SG
The inspectors interviewed training and operations staff and management, and
        level shrink and swell. The inspectors observed that the simulator SG PORV response
observed a scenario run under hot shutdown conditions with MSIVs closed.
        was much smoother and resulted in no erratic SG shrink and swell when compared to
b.
        the recorder traces for SG level and PORV position taken during the plant event. The
Observations and Findinos
        licensee identified the plant SG PORV gain was set at "20", and the integral at "0", but
The inspectors requested the training staff to run a scenario under hot shutdown
        was not sure if the simulator modeling corresponded to the plant. The licensee stated it                             l
conditions with MSIVs closed to observe operation of the SG PORVs and resulting SG
        noimally reviewed all plant modifications and work packages to determine applicability
level shrink and swell. The inspectors observed that the simulator SG PORV response
        to potential simulator hardware or software changes. The licensee wrote a
was much smoother and resulted in no erratic SG shrink and swell when compared to
        non-conformance report to verify the plant SG PORV operation and to determine
the recorder traces for SG level and PORV position taken during the plant event. The
        the simulator SG PORV fidelity to actual plant operation and to investigate how the
licensee identified the plant SG PORV gain was set at "20", and the integral at "0", but
        simulator modeled SG level and AFW flow.
was not sure if the simulator modeling corresponded to the plant. The licensee stated it
        During the post event interviews, several operators identified they had been directed to
l
        maintain a plant condition that they had little training and practical experience
noimally reviewed all plant modifications and work packages to determine applicability
        performing. Operators had used PORVs for post accident cooldown in several simulator
to potential simulator hardware or software changes. The licensee wrote a
        scenarios; however, they had not maintained a hot sheldown condition with the MSIVs
non-conformance report to verify the plant SG PORV operation and to determine
        closed and using SG PORVs for decay heat dissipation. The training staff verified that
the simulator SG PORV fidelity to actual plant operation and to investigate how the
        little time had been spent in dynamic scenarios under hot shutdown conditions, but
simulator modeled SG level and AFW flow.
        stated that training would be set up for the next requal training cycle (mid July,1998) to                           <
During the post event interviews, several operators identified they had been directed to
        discuss the rod drop event and maintenance of hot shutdown conditions in detail;
maintain a plant condition that they had little training and practical experience
        emphasize the importance of the SG PORVs to safety; discuss the conflict of SG level,
performing. Operators had used PORVs for post accident cooldown in several simulator
        AFW flow, and maintaining RCS temperature; discuss new operational guidelines;                                       l
scenarios; however, they had not maintained a hot sheldown condition with the MSIVs
        discuss the expectation for use of three part communications and plant oversight; and
closed and using SG PORVs for decay heat dissipation. The training staff verified that
        run a similar dynamic scenario event on the simulator. The licensee stated that an
little time had been spent in dynamic scenarios under hot shutdown conditions, but
        e-mail would be sent to all operators describing the event, equipment, procedural and
stated that training would be set up for the next requal training cycle (mid July,1998) to
        operator performance weaknesses identified during the event, and Just-in-Time training
<
        would be scheduled.
discuss the rod drop event and maintenance of hot shutdown conditions in detail;
                                                  9
emphasize the importance of the SG PORVs to safety; discuss the conflict of SG level,
AFW flow, and maintaining RCS temperature; discuss new operational guidelines;
l
discuss the expectation for use of three part communications and plant oversight; and
run a similar dynamic scenario event on the simulator. The licensee stated that an
e-mail would be sent to all operators describing the event, equipment, procedural and
operator performance weaknesses identified during the event, and Just-in-Time training
would be scheduled.
9


      - _ - _ _ - _ - _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ .                                                                 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _
- _ - _ _ - _ - _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ .
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _
'
'
    ,
,
f                                                           c.     Conclusions
f
                                                                    Operator training and practical experience at maintaining the plant in a hot shutdown
c.
l                                                                   condition with the MSIVs closed and using SG PORVs for decay heat dissipation was
Conclusions
'
Operator training and practical experience at maintaining the plant in a hot shutdown
                                                                    limited. The simulator SG PORV fidelity was dissimilar to the plant.
l
                                                                                                      lit. Engineering
condition with the MSIVs closed and using SG PORVs for decay heat dissipation was
                                                    E1             Conduct of Engineering
'
;                                                                     e
limited. The simulator SG PORV fidelity was dissimilar to the plant.
lit. Engineering
E1
Conduct of Engineering
;
e
'
E1.1 - Root Cause of Rod Droo (G7)
i
L
a.
Insoection Scone (71707. 93702)
'
'
                                                    E1.1 - Root Cause of Rod Droo (G7)
l
                                                                                                                                                                                                    i
On June 5,1998, the plant experienced a negative rate reactor trip as the result of a
L                                                          a.      Insoection Scone (71707. 93702)                          '
dropped control rod (G7). The inspectors assessed the licensee's investigation team
l                                                                  On June 5,1998, the plant experienced a negative rate reactor trip as the result of a
j
                                                                    dropped control rod (G7). The inspectors assessed the licensee's investigation team
review of the root cause for the dropped control rod.
j                                                                   review of the root cause for the dropped control rod.
I:
I:                                                                                                                                                                                                 .
.
L                                                           b.   ~ Observations and Findinas
L
                                                                                                                                                                                                    ]
b.
                                                                  . The licensee's initial root cause identification of the control rod drop was inconclusive.                                       !
~ Observations and Findinas
                                                                    The licensee identified the stationary gripper coil fuse had blown on control rod #G-7
]
                                                                    due to a ground in the wiring somewhere between the edge of the reactor cavity and the                                           !
. The licensee's initial root cause identification of the control rod drop was inconclusive.
                                                                    reactor head. The affected control rod cable and four other potentially' degraded control                                     -!
The licensee identified the stationary gripper coil fuse had blown on control rod #G-7
due to a ground in the wiring somewhere between the edge of the reactor cavity and the
reactor head. The affected control rod cable and four other potentially' degraded control
-!
.
.
                                                                    rod cables were replaced. Two of the cables exhibited lower than expected cable                                                 i
rod cables were replaced. Two of the cables exhibited lower than expected cable
                                                                    resistance readings, and the other two cables were located in the center, higher                                                 1
i
l-                                                                 temperature, region of the reactor. The licensee added a moisture barrier tape,                                                 I
resistance readings, and the other two cables were located in the center, higher
                                                                                                                                                                                                    '
1
;                              .                                   meggered and pin to pin resistance checked connectors, replaced all fuses with a new
l-
                          ''
temperature, region of the reactor. The licensee added a moisture barrier tape,
;.                                                                  model on all 29 rods, and scheduled rod timing checks.
;
                                                                    The failed cable was shipped to the vendor for analysis. The preliminary report
''
                                                                    identified that a black carbonized material in the connector had created an arc between
model on all 29 rods, and scheduled rod timing checks.
,~                                                                  the conductors when a meggering voltage was applied. Further chemical analysis was
'
.
meggered and pin to pin resistance checked connectors, replaced all fuses with a new
;.
The failed cable was shipped to the vendor for analysis. The preliminary report
identified that a black carbonized material in the connector had created an arc between
the conductors when a meggering voltage was applied. Further chemical analysis was
,~
scheduled to identify the source of the material and the root cause determination was
!
!
                                                                    scheduled to identify the source of the material and the root cause determination was
inconclusive as to whether the failure mode was based on a manufacturing flaw or if the
                                                                    inconclusive as to whether the failure mode was based on a manufacturing flaw or if the                                         !
condition developed over time due to environmental effects such as moisture intrusion.
                                                                    condition developed over time due to environmental effects such as moisture intrusion.                                           !
!
!
At the end of this report period, the licensee's investigation team had not yet issued the
'
'
                                                                    At the end of this report period, the licensee's investigation team had not yet issued the
final report of their findings.
                                                                    final report of their findings.
l
                                                                                                                                                                                                    l
c.
                                                            c.     Conclusions
Conclusions
  .
.
                                                                  'On June 5,1998, the plant experienced a negative rate reactor trip as the result of a
'On June 5,1998, the plant experienced a negative rate reactor trip as the result of a
                                                                    dropped control rod (G7). The licensee assigned a root causs investigation team;
dropped control rod (G7). The licensee assigned a root causs investigation team;
                                                                    however, a final report haa not been issued.
however, a final report haa not been issued.
                                                              ,p
,p
                                                                                                              10
10


                                                                                                        _       _ _ _
_
                                                                                                                .
.
          -
_ _ _
                                                                                                                        i
i
      s.
-
    s
s.
s
l
E1.2 Root Cause of 15A PNH Tube Side Relief Lift
: a.
Insoection Scone (71707. 93702)
i:
On June 5,1998, the plant experienced an automatic reactor trip that resulted in an
unexpected lift of the 15A FWH tube side relief valve. The inspectors assessed the
licensee's investigation team review of the root cause for the unexpected event,
b.
Observations and Findinas
The licensee's initial root cause identification of the FWH tube side relief lift after the
reactor trip was inconclusive. The licensee wrote a non-conformance report and
_
identified that the relief lifted at the expected pressure setpoint. The licensee verified
;
that all FWH system components mechanically worked as designed. However, the
system engineer identified the condensate pump and MFP pressure was higher than
indicated on the characteristic pump pressure curves. The system engineer identified
the impellers had been modified which could have resulted in the pump curve
inaccuracy and inappropriate relief valve setpoint. The system engineer further
i
,
l
identified that a design change may be required for changing the FWH relief setpoint
'
based on the new pump curves. At the end of this report period, the licensee's
. investigation team had not yet issued the final report of their findings.
l
c.
Conclusions
l
l
            E1.2 Root Cause of 15A PNH Tube Side Relief Lift
On June 5,1998, the plant experienced an automatic reactor trip that resulted in an
            : a.  Insoection Scone (71707. 93702)
unexpected lift of the 15A FWH tube side relief valve. The licensee assigned a root
  i:
                    On June 5,1998, the plant experienced an automatic reactor trip that resulted in an
                    unexpected lift of the 15A FWH tube side relief valve. The inspectors assessed the
                    licensee's investigation team review of the root cause for the unexpected event,
              b.  Observations and Findinas
                    The licensee's initial root cause identification of the FWH tube side relief lift after the
                    reactor trip was inconclusive. The licensee wrote a non-conformance report and
                                                            _
                    identified that the relief lifted at the expected pressure setpoint. The licensee verified          ;
                    that all FWH system components mechanically worked as designed. However, the
                    system engineer identified the condensate pump and MFP pressure was higher than
                    indicated on the characteristic pump pressure curves. The system engineer identified
                    the impellers had been modified which could have resulted in the pump curve
i                  inaccuracy and inappropriate relief valve setpoint. The system engineer further                    ,
                                                                                                                        '
l
l
                    identified that a design change may be required for changing the FWH relief setpoint
cause investigation team; however, a final report had not been issued.
                    based on the new pump curves. At the end of this report period, the licensee's
V. Management Meetings
                  . investigation team had not yet issued the final report of their findings.
X1
l              c.  Conclusions
Exit Meeting Summary
l                  On June 5,1998, the plant experienced an automatic reactor trip that resulted in an
                    unexpected lift of the 15A FWH tube side relief valve. The licensee assigned a root
l                  cause investigation team; however, a final report had not been issued.
                                                    V. Management Meetings
l
l
        4
4
            X1    Exit Meeting Summary
n
n
            The inspectors presented the inspection results to members of licensee management at the
The inspectors presented the inspection results to members of licensee management at the
            conclusion of the inspection on June 12,1998. The licensee acknowledged the findings
conclusion of the inspection on June 12,1998. The licensee acknowledged the findings
            presented. The inspectors asked the licensee whether any materials examined during the
presented. The inspectors asked the licensee whether any materials examined during the
            inspection should be considered proprietary. No proprietary information was identified.
inspection should be considered proprietary. No proprietary information was identified.
                                                                                                                        j
j
                                                                11
11
p
p


                                        _ - _ _ _ _ _ - _ . - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ - .
_ - _ _ _ _ _ - _ . - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ - .
    :
:
  .
.
                                PARTIAL LIST OF PERSONS CONTACTED                                           l
PARTIAL LIST OF PERSONS CONTACTED
      Licensee
l
      K.- Albrecht, General Superintendent Engineering, Electrical / Instrumentation & Controls
Licensee
      T. Amundson, General Superintendent Engineering, Mechanical
K.- Albrecht, General Superintendent Engineering, Electrical / Instrumentation & Controls
      T. Breene, Superintendent Nuclear Engineering
T. Amundson, General Superintendent Engineering, Mechanical
      J. Hill, Manager Quality Services
T. Breene, Superintendent Nuclear Engineering
      M. Ladd, Training Process Manager
J. Hill, Manager Quality Services
      G. Lenertz, General Superintendent Plant Maintenance
M. Ladd, Training Process Manager
      R. Lindsey, General Superintendent Safety Assessment
G. Lenertz, General Superintendent Plant Maintenance
      T. Silverberg, General Superintendent Plant Operations
R. Lindsey, General Superintendent Safety Assessment
      J. Sorensen, Plant Manager
T. Silverberg, General Superintendent Plant Operations
                                                                                                            l
J. Sorensen, Plant Manager
                                                                                                            1
l
                                                                                                            l
i
                                                                                                            !
1
                                                                                                            i
1
                                                                                                            1
1
                                                                                                            1
                                                                                                            l
                                                                                                            !
                                                                                                            1
                                                                                                            I
l
l
1
1
l
l
'
'
                                                                                                          12
12
                                                                                                            ;


(::
(::
\-
\\-
:   ,
:
                                    INSPECTION PRCCEDURES USE3
,
        IP 71707:   Plant Operations
INSPECTION PRCCEDURES USE3
        IP 93702:   Response to Events
IP 71707:
                              ITEMS OPENED, CLOSED, AND DISCUSSED
Plant Operations
        Opened
IP 93702:
        50-282/98010-01
Response to Events
        50-306/98010-01     VIO   Inadequate procedure for dumping steam with steam generator l
ITEMS OPENED, CLOSED, AND DISCUSSED
                                    poweroperated relief valves.                               i
Opened
50-282/98010-01
50-306/98010-01
VIO
Inadequate procedure for dumping steam with steam generator
poweroperated relief valves.
i
i
        Closed
Closed
I       None.
I
None.
!
l
Discussed
!
None.
!
!
l        Discussed
!
!
        None.
*'
                                                                                                !
>
!    *'
1
                                                                                                !
>                                                                                              1
:
:
!
!
Line 586: Line 727:
l
l
!
!
                                                    13
13
                                .
.


    _ _ _ _ _ _ _ _ _ _ - _ _ _ _ -             - _ _ _ .
_ _ _ _ _ _ _ _ _ _ - _ _ _ _ -
  .
- _ _ _ .
                                                            LIST OF ACRONYMS USED
.
l                                   AFW   Auxiliary Feedwater
LIST OF ACRONYMS USED
l                                  AWI  Administrative Work Instruction
l
l                                  CFR  Code of Federal Regulations
AFW
l                                  DRP  Division of Reactor Projects
Auxiliary Feedwater
l                                  DRS  Division of Reactor Safety
l                                  EOP  Emergency Operating Procedure
l
l
AWI
Administrative Work Instruction
l
CFR
Code of Federal Regulations
l
DRP
Division of Reactor Projects
l
DRS
Division of Reactor Safety
l
EOP
Emergency Operating Procedure
l
ERCS
Emergency Response Computer System
'
'
                                    ERCS  Emergency Response Computer System
*F
                                    *F   Degrees Fahrenheit
Degrees Fahrenheit
                                    FWH   Feedwater Heater
FWH
Feedwater Heater
gpm
Gallons Per Minute
,
,
                                    gpm  Gallons Per Minute
IP
Inspection Procedure
'
'
                                    IP    Inspection Procedure
LER
                                    LER  Licensee Event Report
Licensee Event Report
                                    LRO   Lead Reactor Operator
LRO
                                    MDAFW Motor Driven Auxiliary Feedwater                           I
Lead Reactor Operator
MDAFW
Motor Driven Auxiliary Feedwater
I
MFP
Main Feedwater Pump
,
,
                                    MFP  Main Feedwater Pump
l
l                                  MSIV Main Steam isolation Valve
MSIV
                                    NR   Narrow Range
Main Steam isolation Valve
                                    NRC   Nuclear Regulatory Commission
NR
                                    NSP   Northern States Power Company
Narrow Range
                                    PORV Power Operated Relief Valves                               I
NRC
                                    PRZR Pressurizer                                               l
Nuclear Regulatory Commission
NSP
Northern States Power Company
PORV
Power Operated Relief Valves
I
PRZR
Pressurizer
l
psig
Pounds Per Square Inch-Gauge
l
,
,
                                    psig  Pounds Per Square Inch-Gauge                              l
l
l                                  RCS   Reactor Coolant System                                     !
RCS
                                    RO   Reactor Operator
Reactor Coolant System
                                    SG   Steam Generator                                           l
!
                                    SM   Shift Manager                                             j
RO
                                    SS   Shift Supervisor
Reactor Operator
                                    STA   Shift Technical Advisor
SG
                                    SWI   Section Work Instruction
Steam Generator
                                    TB   Turbine Building
l
                                    TDAFW Turbine Driven Auxiliary Feedwater
SM
                                    Tavg Average Reactor Coolant System Temperature                 l
Shift Manager
                                    VIO   Violation
j
SS
Shift Supervisor
STA
Shift Technical Advisor
SWI
Section Work Instruction
TB
Turbine Building
TDAFW
Turbine Driven Auxiliary Feedwater
Tavg
Average Reactor Coolant System Temperature
l
VIO
Violation
l
l
l
l
,
,
                                                                          14
14
1
1
                                                                                    ______________a
______________a


            . _ _ _ _ _ _ _ _ . - _ .   _ - _ - _ - _ - _ _ - - _ _ _
. _ _ _ _ _ _ _ _ .
                                                                                                _ _ _ - _ _ _ - _ _ _ _ -
- _ .
  -
_ - _ - _ - _ - _ _ - - _ _ _
                                                                    LIST OF DOCUMENTS REVIEWED
_ _ _ - _ _ _ - _ _ _ _ -
    Procedure #                       Revision #                         Ijilg
-
    EOP 1E-0                           Revision 17                         Reactor Trip Or Safety injection
LIST OF DOCUMENTS REVIEWED
    1 ES-0.1                           Rev 13                             Reactor Trip Recovery
Procedure #
    1C1.3                             Rev 40                             Unit 1 Shutdown
Revision #
    SWI O-24                           Rev 4                               Operation Section Communications
Ijilg
    5AWI 3.1.2                         Rev 8                               Shift Manager Program
EOP 1E-0
    SWI 0-10                           Rev 30                             Operation Manual Usage
Revision 17
    2ES-0.1                           Rev 12                             Reactor Trip Recovery
Reactor Trip Or Safety injection
                                                                                                                          1
1 ES-0.1
                                                                                                                          !
Rev 13
                                                                                                                          >
Reactor Trip Recovery
                                                                                    15
1C1.3
Rev 40
Unit 1 Shutdown
SWI O-24
Rev 4
Operation Section Communications
5AWI 3.1.2
Rev 8
Shift Manager Program
SWI 0-10
Rev 30
Operation Manual Usage
2ES-0.1
Rev 12
Reactor Trip Recovery
1
!
>
15
l
l
1
1
}}
}}

Latest revision as of 22:35, 22 May 2025

Insp Repts 50-282/98-10 & 50-306/98-10 on 980605-12. Violations Noted.Major Areas inspected:on-site Insp Into Circumstances Surrounding Unit 1 RT Due to Dropped CR & Actions Taken for Recovery to Safe Shutdown on 980605
ML20236P011
Person / Time
Site: Prairie Island  
Issue date: 07/10/1998
From:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20236N992 List:
References
50-282-98-10, 50-306-98-10, NUDOCS 9807160111
Download: ML20236P011 (15)


See also: IR 05000282/1998010

Text

- _ _ _ _ - _ _ _ _ _ - _ _ - _ _ _ _ _ _ - _ _ _ _ _ _ _ _ . _

_

__ . _ _ _

. _ _

_

_ _ _ - -

_ _ _ _ _ _ _ .

)

r

U.S. NUCLEAR REGULATORY COMMISSION

REGIONlli

.

Docket Nos:

50-282;50-306

,

License Nos:

DPR-42; DPR-60

1

Report Nos:

50-282/98010(DRS); 50-306/98010(DRS)

Licensee:

Northem States Power Company

Facility:

Prairie Island Nuclear Generating Plant

Location:

1717 Wakonade Drive East

,

Welch, MN 55089

l

i

Dates:

June 5 through 12,1998

Inspectors:

M. Bielby, Reactor Engineer / Team Leader

S. Ray, Senior Resident inspector, Prairie Island

R. Winter, Reactor Engineer

~ Approved by:

M. Leach, Chief, Operator Licensing Branch

Division of Reactor Safety

'

1

i

!

l

r

I

~

9907160111 990710

PDR

ADOCK 05000282

!.

G

PDR

.

.

I

t

______

_

- _____.

. - - .

.-

.

,

EXECUTIVE SUMMARY

Prairie Island Nuclear Generating Station, Unit 1 and Unit 2

NRC Inspection Reports 50-282/98010; 50-306/98010

This special inspection report covers a period of on-site inspection into the circumstances

surrounding the Unit i reactor trip due to a dropped control rod and the actions taken for the

recovery to safe shutdown conditions on June 5,1998. The conduct of operations of the Prairie

Island staff for this event generally was good during the initial stages of the event; however, the

inspectors noted some equipment problems, and weaknesses in procedures, communications,

training, and performance.

Ooerations

The operator's initial response and actions taken based on indications for the dropped

.

rod event were good; however, subsequent operator actions to stabilize the plant and

dissipate decay heat were not completely effective as evidenced by the inadvertent rise

in Tave and lifting of the steam generator (SG) #1 A safety valve. (Sections 01.1 and

04.1)

The operators lacked adequate procedural guidance for stabilizing the plant and

.

dissipating decay heat by dumping steam using the SG power operated relief valves

(PORVs) during a hot shutdown condition with main steam isolation valves (MSIVs)

closed. A violation of 10 CFR Part 50, Appendix B, Criterion V was issued. (Sections

O3.1 and 04.1)

During subsequent actions to stabilize the plant, a lack of three part communication, a

.

lack of consistent plant oversight, and unfamiliarity of SG PORV response contributed to

failure to adequately remove decay heat. (Section 04.1)

Operator training and practical experience at maintaining the plant in a hot shutdown

.

condition with the MSIVs closed and using SG PORVs for decay heat dissipation was

limited. (Sections 04.1 and 05.1)

The simulator SG PORV fidelity was dissimilar to the plant and the licensee wrote a non-

.

conformance report. (Section O5.1)

2

..

___

-

___

._

.__

_

_ _ _ _ . __

_ _ _ _ _ _ _ _ _ _ _

._

_ _ _ _ _ _ _

.

'

Report Detalls

Brief Narrative of the Rod Droo Event

l

The Unit i reactor was operating at 100% power on June 5,1998, and experienced an

unexpected automatic trip. The operators verified all control rods fully inserted and identified

that the first out indication was a negative flux-rate trip. The control room received reports of

steam release in the turbine building (TB) that was later identified as an unexpected relief valve

lift on the 15A feedwater heater (FWH). One of the two operating main feedwater pumps

(MFPs) tripped, as expected, and operators tripped the remaining MFP to minimize secondary

inventory loss. This action reseated the lifted FWH relief valve. The operators used the

3

atmospheric steam dumps to initially remove decay heat. Operators closed the MSIVs as a

result of excessive reactor coolant system (RCS) cooldown and in response to the report of

steam in the TB. Both the #11 turbine driven auxiliary feedwater (TDAFW) and #12 motor

driven auxiliary feedwater (MDAFW) pumps automatically started and remained in service to

supply auxiliary feedwater (AFW) to both SGs. One control room operator was dedicated to

maintain both SG water levels 35% - 37% as indicated on narrow range (NR) meters.

Approximately two hours after efforts to stabilize the plant, one of the five SG "A" main steam

safety valves (#1 A) unexpectedly lifted and reseated. The resulting swell caused indicated NR

level in SG "A" to increase to 50%, and SG "B" to 45%, respectively. The licensee later

identified that the operator had placed both SG PORVs in the manual mode just prior to the

unexpected SG main steam safety valve lift.

l. Operations

01

Conduct of Operations

O1.1 Seouence of Events

a.

Insoection Scoce (71707. 93702)

The inspectors formulated a sequence of events based on the following information:

interviews conducted with the licensee's management, operations and engineering staff;

review of operator logs, parameter recorders, process computer and Emergency

Response Computer System (ERCS) information; and observation of control room

l

panels,

b.

Observations and Findinos

The following information describes the sequence of events (Central Daylight Time)

commencing with the automatic reactor trip of Unit 1 from 100% power as reconstructed

i

l

by the NRC inspection team:

3

l

l

___

.

\\

d'

i

Fridav. June 5.1998

06:58 pm

Unit 1 received an automatic reactor trip, operators identified the first out

i

annunciator as the negative flux rate trip. Operators entered 1E-0, * Reactor Trip

Or Safety injection," Revision 17. Operators verified all control rods fully

,

inserted, one of two operating MFPs (#11) received automatic trip, #11 TDAFW

and #12 MDAFW pumps started automatically with discharge flow at 550 gpm.

,

Average RCS temperature (Tave) dropped from 559 to 539 'F, and SG levels

i

dropped from 45% to 0% NR.

07:01 -

l

07:04 pm

Tave continued to drop to 538 'F, control room received Zone 15 TB fire alarm

and report of steam release in the TB. Operators completed Ugcedure 1E-0 and

entered 1ES-0.1, Reactor Trip Recovery, Revision 13. AFW tiow was throttled to

l

200 gpm to limit cooldown, MSIVs closed to limit cooldown and stop steam

'

release.

07:07 -

. 07:15 pm

Operators received report that steam was due to the lift of the 15A FWH tube

side relief. Operators stopped the running #12 MFP and condensate pump to

minimize secondary inventory loss and reduce 15A FWH tube side pressure.

The lifted 15A FWH relief closed, Tave increased to 547 'F, and continued to

rise.

07:17 pm

AFW flow was increased to 270 gpm.

i

i

07:19 pm

Tave at 555 *F, SG steam pressure at 1050 psig (SG PORV setpoint) and both

PORVs automatically opened.

07:45 pm

SG levels at 10% and continued to rise.

07:53 pm

12 SG PORV setpoint dialed down in automatic to open valve more and reduce

pressure. However, opening 12 SG PORV caused 11 SG PORV to close and

cycle.

08:08 pm

SG level approached normal band of 33 +/- 5%; however, AFW flow throttled to

60 gpm and caused SG level to decrease from 30% to 25% over the next four

- minutes.

08:10 pm

11 SG PORV setpoint dialed down in automatic, caused valve to open more and

'

reduce pressure.

08:12 -

08:24 pm

AFW flow increased to 200 gpm in several steps, SG levels at 25% and started

to increase again.

4

_ _ _ _

_____ _ _

____

,

08:45-

09:04 pm

SG levels approached normal band of 33 +/- 5%, AFW flow throttled down to 50

gpm in several steps. SG levels continued to rise slowly from 33% to 36%.

During this period it appeared that the operator decreased the SG PORV

automatic setpoints in an attempt to open the PORVs more and reduce SG

pressure. On the average, SG PORVs swung open and closed 10-15% while

the controller output changed 30-40%. SG levels shrank and swelled

approximately +/- 2% while the overall level slowly increased toward the

administrative procedurallimit of 38%.

NOTE:

At 09:03 pm both SG PORV setpoints appeared to have been increased while in

automatic which closed the valves more and reduced the level swells. However,

l

the decay heat removal was decreased which caused Tave to start increasing

from 552 *F.

09:07 pm

Both SG PORVs placed in manual with "11" at approximately 22% demand, and

"12" at 28%. The manual SG PORV demand was considerably less than when

!

in automatic which closed the valves more and caused Tave to increase rapidly

from 553 *F.

09:12 pm

Tave at 557 'F, SG steam 9. essure at 1070 psig and one (#1 A) of five main

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steam safety valves on "A" SG lifted and reseated which swelled the "A" SG level

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from 37% to 50%, and the "B" SG level to 45%.

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09:16 pm

Tave bottomed out at 547 'F due to the SG safety valve lifting and reciosing, and

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then started to rise again.

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09:24 pm

Tave at 555 *F, both SG PORVs retumed to automatic mode and rapidly opened

and closed when SG steam pressure was greater than the PORV setpoint (1050

psig).12 SG level briefly swelled from 38% to 45%.

09:25 -

11:00 pm

Plant stabilized and slowly brought to normal hot shutdown conditions. Plant

staff investigating failure of 86G relay to lockout generator output breakers, lack

of procedural guidance in 1ES-0.1 to bypass a recently installed backup synch

check relay to allow reclosing the generator output breakers, cause of the

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automatic reactor trip, and unexpected lifting of the 15A FWH relief valve.

c.

Conclusions

The operators' initial response and actions taken based on indications for the dropped

rod event were good; however, subsequent operator actions to stabilize the plant and

dissipate decay heat were not completely effective as evidenced by the inadvertent rise

in Tave and lifting of the SG #1 A safety valve.

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03

Operations Procedures and Documentation

O3.1 Lack of Guidance for Dumoina Steam Usino SG PORVs

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a.

Insoection Scoce (71707. 93702)

The inspectors performed the following to determine the adequacy of guidance for

dumping steam using SG PORVs: reviewed 1ES-0.1, * Reactor Trip Recovery," Revision

13; interviewed licensed operators and managernent personnel; reviewed parameter

recorders, process computer and ERCS information.

b.

Observations and Findings

The Unit 1 EOP,1ES-0.1, Step 5 (bullet under " Response Not Obtained" column)

directed the operator to " Dump steam with SG PORVs," but did not provide any further

guidance or reference that described how to perform the evolution. During the plant

stabilization phase of the reactor trip recovery, the operator was required to maintain SG

levels 28 - 38%. The operator initially left both SG PORVs in the normal automatic

configuration and was very slowly adjusting the controller pot down from the normal

.

operating setpoint of 75% (1050 psig) to the no Ioad setpoint of 71.5% (1005 psig). The

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PORVs' responsiveness resulted in erratic SG level swings. In lieu of procedural

guidance and with the PORV auto setpoint at approximately 74.2% (1040 psig), the lead

reactor operator (LRO) placed both SG PORV controllers in manual to reduce the erratic

SG ievel swings and attempted to maintain SG level ! ass than the 38% administrative

limit by controlling AFW flow. However, the operdor failed to open the PORVs

sufficiently and the dissipation of decay heat was inadequate. As a result, Tave

continued to increase which caused the SG pressure to increase to the 1 A SG safety

valve setpoint of 1075 psig and it cycled open and close. The lack of adequate

procedural guidance for dumping steam using SG PORVs was considered a violation of

10 CFR Part 50, Appendix B, Criterion V," Instructions, Procedures, and Drawings,"(50-

282/98010-01(DRS)); (50-306/98010-01(DRS)).

Subsequent to the event, the licensee revised both unit EOPs,1ES-0.1 and 2ES-0.1, to

direct reduction of the SG PORVs auto setpoint to 71.5% (1005 psig)if MSIVs are

closed. Additionally, the same procedures were changed to direct the operator to stop

feed flow to a SG if level reaches 40%, vice 50%.

c.

Conclusions

,

The operators lacked adequate procedural guidance for stabilizing the plant and

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dissipating decay heat by dumping steam using the SG PORVs during a hot shutdown

condition with MSIVs closed. A violation of 10 CFR Part 50, Appendix B, Criterion V

was issued.

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04

Operator Knowledge and Performance

04.1 -Coerator Resoonse to Rod Droo Event

a.

Insoection Scone (71707. 93702)

The inspectors reviewed operator performance based on their initial response to the

reactor trip and mode change to hot shutdown conditions. The inspectors based their

findings on the following: Interviews conducted with operations and engineering staff;

review of operator logs, parameter recorders, process computer and ERCS information;

review of alarm response, emergency, abnormal, and normal operating procedures.

b.

Observations and Findinas

The Unit 1 control room operators' initial response to the rod drop event was good. The

shift manager (SM) assumed the role of shift technical advisor (STA), the Unit 1 shift

supervisor (SS) assumed the role of emergency operating procedure (EOP) reader, the

Unit 1 LRO took control of the secondary plant, and the other Unit i reactor operator

(RO) took control of the primary plant. The crew correctly identified that an automatic

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reactor trip had occurred and promptly entered EOP 1E-0, * Reactor Trip Or Safety

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Injection," Revision 17. After completing the specified procedural actions, the crew

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correctly transitioned to 1ES-0.1, " Reactor Trip Recovery," Revision 13. The LRO

appropriately throttled AFW flow to limit cooldown. A TB fire alarm was received, and

after investigating, field operators identified an unexpected steam release in the TB.

,

Concurrently, control room personnel identified an excessive primary cooldown based

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on a Tave decrease to 538 'F. The control room operators responded to the excessive

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primary cooldown and closed the MSIVs and bypass valves. The single operating MFP

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and condensate pump were stopped to minimize secondary inventory loss. Further

reports from the TB clarified the steam release had come from an unexpected lifted tube

side relief on the 15A FWH that reseated after tripping the MFP As a result of those

!

actions, Tave increased to 547 'F and continued to slowly rise. The operators attempte.,d

!

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to stabilize the plant in a hot shutdown condition with the MSIVs closed and maintain the

following parameters as specified by 1ES-0.1: pressurizer (PRZR) pressure between

2220 and 2250 psig; PRZR level between 19 and 23%; SG NR level between 30 and

36%; and RCS Tave between 545 and 549 'F.

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The crew was directed to maintain a plant condition that had not been practiced during

simulator training. The crew had used PORVs for post accident cooldown in several

simulator scenarios; however, they had not maintained a hot shutdown condition with

the MSIVs closed and using SG PORVs for decay heat removal. Additionally, they

determined the plant was stabilized and transitioned from 1ES-0.1, " Reactor Trip

Recovery," to 1C1.3, " Unit 1 Shutdown," Revision 40. However, even though plant

parameters were not changing rapidly, the SG levels continued to trend toward the

administrative and design limits, and Tave was actually 552 'F vice the required

545 - 549 'F.

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The STA/SM and SS determined the plant was stable because they had transitioned to

the shutdown procedure. Consequently they relaxed their continued oversight of the

plant status and became focused on their administrative duties. The STA observed that

no critical safety functions had been entered and resumed the SM duties of notifications.

Likewise, the SS focused his attention on followup of equipment problems with the FWH

relief valve and generator output breaker relays, procedure problem with the backup

bypass for the synch check relay, restoring the fire alarms, diagnosing the cause of the

reactor trip, and completing logs.

The lack of adequate procedural guidance was a contributor to the subsequent poor

operator performance. The LRO was required to maintain SG levels 33+/-5%, and had

been periodically throttling AFW flow. The LRO was also directed to dump steam with

SG PORVs in accordance with 1ES-0.1, but was not provided with any further guidance

that described how to perform the evolution. The LRO initially left both SG PORVs in

the normal automatic configuration and very slowly started to adjust the controller pot

down from the normal operating setpoint of 75% (1050 psig) to the no load setpoint of

71.5% (1005 psig).

The erratic response of the SG PORVs was unexpected. The LRO had very slowly

decreased the SG PORV setpoint to 74.2% (1040 psig). However, the PORV operation

was very responsive and wesed erratic SG level swings which was unexpected to the

LRO. The PORVs opened every 5 - 10 seconds and caused SG level swell and shrink

of about 2%.

An instance of poor communications and lack of communications contributed to the

indicated SG level exceeding the design limit, inadequate dissipation of decay heat, and

lifting of the main steam safety valve. The LRO tried to maintain both SG levels within

the procedurallimits. The automatic response of the PORVs and erratic SG level

swings were unexpected. The LRO stated he made a verbal announcement that he

was placing the SG PORVs in manual; however, no acknowledgment was made by any

of the other control room operators. As such the communications were not in

accordance with Section Work Instruction (SWI) O-24, " Operation Section

Communications," Revision 4. When one SG level approached the 38% limit the LRO

placed both SG PORVs in manual with each PORV approximately 50% open. The

operator decreased AFW flow to maintain SG levelless than the 38% limit. The PORVs

were insufficiently opened to dissipate the decay heat and Tave continued to increase

which caused the SG pressure to increase to the 1 A SG safety valve setpoint of 1075

psig, and it cycled open and close. The cycling of the safety valve resulted in a large

SG swell to 45-50% which alerted the SS. The LRO informed the SS that both SG

PORVs were in manual. The SS checked safety valve tailpipe temperatures and

determined the 1A safety on 11 SG had cycled. Teve decreased to a minimum of 547 *F

due to the open safety valve. The LRO returned the SG PORV control to automatic

within about 12 minutes at which time the PORVs briefly cycled because steam

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pressure was greater than 1050 psig. The plant was stabilized and in hot shutdown

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conditions within about another 30 minutes.

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c.

Conclusions

During subsequent actions to stabilize the plant a lack of three part communication, lack

of consistent plant oversight, and unfamiliarity of SG PORV response contributed to

failure to adequately remove decay heat.

05

Operator Training and Qualification

05.1 SG Level / SG PORV / Hot Shutdown With MSIVs Closed

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a.

Insoection Scoce (71707. 93702)

The inspectors interviewed training and operations staff and management, and

observed a scenario run under hot shutdown conditions with MSIVs closed.

b.

Observations and Findinos

The inspectors requested the training staff to run a scenario under hot shutdown

conditions with MSIVs closed to observe operation of the SG PORVs and resulting SG

level shrink and swell. The inspectors observed that the simulator SG PORV response

was much smoother and resulted in no erratic SG shrink and swell when compared to

the recorder traces for SG level and PORV position taken during the plant event. The

licensee identified the plant SG PORV gain was set at "20", and the integral at "0", but

was not sure if the simulator modeling corresponded to the plant. The licensee stated it

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noimally reviewed all plant modifications and work packages to determine applicability

to potential simulator hardware or software changes. The licensee wrote a

non-conformance report to verify the plant SG PORV operation and to determine

the simulator SG PORV fidelity to actual plant operation and to investigate how the

simulator modeled SG level and AFW flow.

During the post event interviews, several operators identified they had been directed to

maintain a plant condition that they had little training and practical experience

performing. Operators had used PORVs for post accident cooldown in several simulator

scenarios; however, they had not maintained a hot sheldown condition with the MSIVs

closed and using SG PORVs for decay heat dissipation. The training staff verified that

little time had been spent in dynamic scenarios under hot shutdown conditions, but

stated that training would be set up for the next requal training cycle (mid July,1998) to

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discuss the rod drop event and maintenance of hot shutdown conditions in detail;

emphasize the importance of the SG PORVs to safety; discuss the conflict of SG level,

AFW flow, and maintaining RCS temperature; discuss new operational guidelines;

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discuss the expectation for use of three part communications and plant oversight; and

run a similar dynamic scenario event on the simulator. The licensee stated that an

e-mail would be sent to all operators describing the event, equipment, procedural and

operator performance weaknesses identified during the event, and Just-in-Time training

would be scheduled.

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c.

Conclusions

Operator training and practical experience at maintaining the plant in a hot shutdown

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condition with the MSIVs closed and using SG PORVs for decay heat dissipation was

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limited. The simulator SG PORV fidelity was dissimilar to the plant.

lit. Engineering

E1

Conduct of Engineering

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E1.1 - Root Cause of Rod Droo (G7)

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a.

Insoection Scone (71707. 93702)

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On June 5,1998, the plant experienced a negative rate reactor trip as the result of a

dropped control rod (G7). The inspectors assessed the licensee's investigation team

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review of the root cause for the dropped control rod.

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b.

~ Observations and Findinas

]

. The licensee's initial root cause identification of the control rod drop was inconclusive.

The licensee identified the stationary gripper coil fuse had blown on control rod #G-7

due to a ground in the wiring somewhere between the edge of the reactor cavity and the

reactor head. The affected control rod cable and four other potentially' degraded control

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rod cables were replaced. Two of the cables exhibited lower than expected cable

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resistance readings, and the other two cables were located in the center, higher

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temperature, region of the reactor. The licensee added a moisture barrier tape,

model on all 29 rods, and scheduled rod timing checks.

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meggered and pin to pin resistance checked connectors, replaced all fuses with a new

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The failed cable was shipped to the vendor for analysis. The preliminary report

identified that a black carbonized material in the connector had created an arc between

the conductors when a meggering voltage was applied. Further chemical analysis was

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scheduled to identify the source of the material and the root cause determination was

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inconclusive as to whether the failure mode was based on a manufacturing flaw or if the

condition developed over time due to environmental effects such as moisture intrusion.

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At the end of this report period, the licensee's investigation team had not yet issued the

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final report of their findings.

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c.

Conclusions

.

'On June 5,1998, the plant experienced a negative rate reactor trip as the result of a

dropped control rod (G7). The licensee assigned a root causs investigation team;

however, a final report haa not been issued.

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E1.2 Root Cause of 15A PNH Tube Side Relief Lift

a.

Insoection Scone (71707. 93702)

i:

On June 5,1998, the plant experienced an automatic reactor trip that resulted in an

unexpected lift of the 15A FWH tube side relief valve. The inspectors assessed the

licensee's investigation team review of the root cause for the unexpected event,

b.

Observations and Findinas

The licensee's initial root cause identification of the FWH tube side relief lift after the

reactor trip was inconclusive. The licensee wrote a non-conformance report and

_

identified that the relief lifted at the expected pressure setpoint. The licensee verified

that all FWH system components mechanically worked as designed. However, the

system engineer identified the condensate pump and MFP pressure was higher than

indicated on the characteristic pump pressure curves. The system engineer identified

the impellers had been modified which could have resulted in the pump curve

inaccuracy and inappropriate relief valve setpoint. The system engineer further

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identified that a design change may be required for changing the FWH relief setpoint

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based on the new pump curves. At the end of this report period, the licensee's

. investigation team had not yet issued the final report of their findings.

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c.

Conclusions

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On June 5,1998, the plant experienced an automatic reactor trip that resulted in an

unexpected lift of the 15A FWH tube side relief valve. The licensee assigned a root

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cause investigation team; however, a final report had not been issued.

V. Management Meetings

X1

Exit Meeting Summary

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The inspectors presented the inspection results to members of licensee management at the

conclusion of the inspection on June 12,1998. The licensee acknowledged the findings

presented. The inspectors asked the licensee whether any materials examined during the

inspection should be considered proprietary. No proprietary information was identified.

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PARTIAL LIST OF PERSONS CONTACTED

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Licensee

K.- Albrecht, General Superintendent Engineering, Electrical / Instrumentation & Controls

T. Amundson, General Superintendent Engineering, Mechanical

T. Breene, Superintendent Nuclear Engineering

J. Hill, Manager Quality Services

M. Ladd, Training Process Manager

G. Lenertz, General Superintendent Plant Maintenance

R. Lindsey, General Superintendent Safety Assessment

T. Silverberg, General Superintendent Plant Operations

J. Sorensen, Plant Manager

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INSPECTION PRCCEDURES USE3

IP 71707:

Plant Operations

IP 93702:

Response to Events

ITEMS OPENED, CLOSED, AND DISCUSSED

Opened

50-282/98010-01

50-306/98010-01

VIO

Inadequate procedure for dumping steam with steam generator

poweroperated relief valves.

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Closed

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None.

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Discussed

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None.

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LIST OF ACRONYMS USED

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AFW

Auxiliary Feedwater

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AWI

Administrative Work Instruction

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CFR

Code of Federal Regulations

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DRP

Division of Reactor Projects

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DRS

Division of Reactor Safety

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EOP

Emergency Operating Procedure

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ERCS

Emergency Response Computer System

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  • F

Degrees Fahrenheit

FWH

Feedwater Heater

gpm

Gallons Per Minute

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IP

Inspection Procedure

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LER

Licensee Event Report

LRO

Lead Reactor Operator

MDAFW

Motor Driven Auxiliary Feedwater

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MFP

Main Feedwater Pump

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MSIV

Main Steam isolation Valve

NR

Narrow Range

NRC

Nuclear Regulatory Commission

NSP

Northern States Power Company

PORV

Power Operated Relief Valves

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PRZR

Pressurizer

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psig

Pounds Per Square Inch-Gauge

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RCS

Reactor Coolant System

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RO

Reactor Operator

SG

Steam Generator

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SM

Shift Manager

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SS

Shift Supervisor

STA

Shift Technical Advisor

SWI

Section Work Instruction

TB

Turbine Building

TDAFW

Turbine Driven Auxiliary Feedwater

Tavg

Average Reactor Coolant System Temperature

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VIO

Violation

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LIST OF DOCUMENTS REVIEWED

Procedure #

Revision #

Ijilg

EOP 1E-0

Revision 17

Reactor Trip Or Safety injection

1 ES-0.1

Rev 13

Reactor Trip Recovery

1C1.3

Rev 40

Unit 1 Shutdown

SWI O-24

Rev 4

Operation Section Communications

5AWI 3.1.2

Rev 8

Shift Manager Program

SWI 0-10

Rev 30

Operation Manual Usage

2ES-0.1

Rev 12

Reactor Trip Recovery

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