05000261/LER-1981-001, Updated LER 81-001/01T-1:on 810109,turbine Runback & Automatic Rod Withdrawal Block Protection Defeated W/Power Range Channel N41 Being Out of Svc.Caused by Improper Rod Drop Analysis.Administrative Controls Revised: Difference between revisions

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| Mode =  
| Mode =  
| Docket = 05000261
| Docket = 05000261
| LER year = 2081
| LER year = 1981
| LER number = 1
| LER number = 1
| LER revision =  
| LER revision = 0
| Event date =  
| Event date =  
| Report date =  
| Report date =  
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=text=
=text=
{{#Wiki_filter:NRC FORM* 366             " UPDATE REPORT - PREVIOUS REPORT DATE 1/23/81"                                                         u.S. NUCLEAR REGULATORY COMMISSION (7-77 F LICENSEE EVENT REPORT 0
{{#Wiki_filter:NRC FORM 366
COUROL BLOC %: l 1
" UPDATE REPORT - PREVIOUS REPORT DATE 1/23/81" u.S. NUCLEAR REGULATORY COMMISSION (7-77 F LICENSEE EVENT REPORT 0
l     l       l   l    l lh 6
COUROL BLOC %: l l
(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) lo lil8 lS       l CLICENSEE l H lB         lR l 2 l@l 0l 0l -l 0lLICENSE 14      15 0] 0l     0l 0l -l 0 l 0l@l NUMBER                  25 4 l 1l 26 1l 1l 1l@l 57 CAT LICENSE TYPE JO l
l l
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lo lil lS l C l H lB lR l 2 l@l 0l 0l -l 0l 0] 0l 0l 0l -l 0 l 0l@l 4 l 1l 1l 1l 1l@l l
74      75      REPORT DATE 7       8                     60           61               DOCK ET NUMBER EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h l o l 2 l l0n January 9,1981, with the unit at 100% power, it was determined that operation with l g o ,3,     lthe RPI System input to the turbine runback and auto rod withdrawal defeated and power l
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  , o g , , [ range channel N41 input out of service is contrary to the assumptions in the safety                                                                               l
8 9 LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE JO 57 CAT 58 CON'T loIil
  , o g g analysis prepared during the fuel reload safety evaluation.                                                                     Still the probability of l l
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g lnot sensing a dropped rod is small since three of the power range detectors were                                                                                           l l o l , l [ ope rab le . 'Ihis occurrence is reportable pursuant to Technical Specifications                                                                                   l oig          .9.2.a(6).               No adverse consequences resulted from the above condition.                                                                           l 80 C DE                   CODE       SUBC E                     COMPONENT CODE                 SUBC DE         S     ODE
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8 60 61 DOCK ET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h l o l 2 l l0n January 9,1981, with the unit at 100% power, it was determined that operation with l g o,3, lthe RPI System input to the turbine runback and auto rod withdrawal defeated and power l
7       8                       9           10             11             12             13                           18           19             20 SE QUE NTI AL                     OCCURRENCE           REPORT                   REVISION LER RO _E                                                 R EPoR T NO.                           CODE                 TYPE                       No.
, o g,, [ range channel N41 input out of service is contrary to the assumptions in the safety l
                @yg   a
, o g g analysis prepared during the fuel reload safety evaluation.
_ 21 8l 1l YE[---j l VENT 22           23 AR          l0l0l1l 24             26 y
Still the probability of l l
27 l0l1l 28       29 l Tl 30 b31 l1l 32 TAKEN AC ON                   oN PLANT             VT                       HOURS 22         SB IT D         FOR S 8.         SUPPLt R         MANUF TURER I33Glgl34 Gl g                 {J5 Zj g             [36Zj@           l 0l 0l 0l 3/
g lnot sensing a dropped rod is small since three of the power range detectors were l
l 40
l o l, l [ ope rab le. 'Ihis occurrence is reportable pursuant to Technical Specifications l
[}jg 41
.9.2.a(6).
[_qg lNjg lWl1l2l0lg 42               43           44           47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i o      lA review of the H.                         B. Robinson Unit 2 FSAR and Fuel Reload Safety Evaluation                                                               l
No adverse consequences resulted from the above condition.
      , ,      g identified           that the rod drop analysis assumes both turblae runback and auto rod                                                                       l
l oig 80 C DE CODE SUBC E COMPONENT CODE SUBC DE S
    ,,y,,gwithdrawal block.                                 A new analysis of this event concluded that operation without                                                           l
ODE [oJ5]
    ,,,3,       g these protective systems is not adverse to safety. Administrative controls, which                                                                                 l were implemented f ollowing this event , will be revised to delete the 70% power I
lI l E l@ d@ y@ l Il Nl S l Tl Rl U l@ y@ ]@
m l restriction.
7 8
    ;      8 9                                                                                                                                                                 80 ST     S           % POWE R                         OTHER STATUS                 Dis O RY                             DISCOVERY DESCRIPTION OBSERVATION i s lEl@ l1l0l0l@l '                '          "
9 10 11 12 13 18 19 20 SE QUE NTI AL OCCURRENCE REPORT REVISION
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AETiviTY CO0 TENT RELE ASED OF RELE ASE                         AMOUNT OF ACTIVITY                                                       LOCATION OF RELEASE i 6      [Z_j @ [Zj g l                                     N/A                       l           l                             N/A                                       l 7     8 9                 10           tt                                             44           45                                                                   80 PERSONNEL EXPOSURES NUMBER               TYPE           CI SCRIP TION i i l0l0l0l@lZl@l"  ''
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40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h lA review of the H.
B. Robinson Unit 2 FSAR and Fuel Reload Safety Evaluation l
i o identified that the rod drop analysis assumes both turblae runback and auto rod l
g
,,y,,gwithdrawal block.
A new analysis of this event concluded that operation without l
,,,3, g these protective systems is not adverse to safety. Administrative controls, which l
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I 8 9 80 ST S
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R 9 10 68 69 80 5 NAME OF PHEPARER PHONE:


6                                 SUPPLEMENTAL INFORMATION FOR LICENSEE EVENT UPDATE REPORT 81-001, REVISION 1 I. Cause Description and Analysis, On January 7,1981, the Power Range Channel N41 was taken out of service.
6 SUPPLEMENTAL INFORMATION FOR LICENSEE EVENT UPDATE REPORT 81-001, REVISION 1 I.
Previous to this, the Rod Position Indication System (RPI) input to the turbine runback system and auto rod withdrawal circuit had been defeated due to spurious rod drop indications in an effort to prevent unnecessary thermal cycles to Reactor Coolant System (RCS) components. On January 9, 1981, it was determined, by a review of the H. B. Robinson, Unit No. 2 FSAR and Fuel Reload Safety Evaluation, that both of these documents assume that turbine runback and auto rod withdrawal defeat occur follow-ing a control rod drop. These systems are actuated by any one RPI bottom signal or a rapid flux decrease on any one power range channel.
Cause Description and Analysis, On January 7,1981, the Power Range Channel N41 was taken out of service.
By having N41 inoperable, a few rods located in the core region nearest N41 might not be detected by the other three power range detectors if they were to drop. Based on this review, therefore, the event was identified as reportabic pursuant to Technical Specification 6.9.2.a.6.
Previous to this, the Rod Position Indication System (RPI) input to the turbine runback system and auto rod withdrawal circuit had been defeated due to spurious rod drop indications in an effort to prevent unnecessary thermal cycles to Reactor Coolant System (RCS) components. On January 9, 1981, it was determined, by a review of the H. B. Robinson, Unit No. 2 FSAR and Fuel Reload Safety Evaluation, that both of these documents assume that turbine runback and auto rod withdrawal defeat occur follow-ing a control rod drop.
These systems are actuated by any one RPI bottom signal or a rapid flux decrease on any one power range channel.
By having N41 inoperable, a few rods located in the core region nearest N41 might not be detected by the other three power range detectors if they were to drop.
Based on this review, therefore, the event was identified as reportabic pursuant to Technical Specification 6.9.2.a.6.
Since an RCCA drop event did not occur during this time, no adverse consequences resulted from the above situation.
Since an RCCA drop event did not occur during this time, no adverse consequences resulted from the above situation.
II. Corrective Action All atfected systems were immediately returned to service when it was determined that having both inputs to the turbine runback and auto rod withdrawal systems defeated may be contrary to the FSAR and fuel reload safety analysis.
II.
III. Correct ive Action To Prevent Recurrence A review of this issue has been completed, and an analysis has been i
 
performed by the fuel supplier. On the basis of this analysis, it has been concluded that even without the turbine runback and automatic rod withdrawal block protection systems, H. B. Robinson, Unit No. 2 will have acceptable thermal margin with respect to a dropped rod transient.
==Corrective Action==
All atfected systems were immediately returned to service when it was determined that having both inputs to the turbine runback and auto rod withdrawal systems defeated may be contrary to the FSAR and fuel reload
 
==safety analysis==
III. Correct ive Action To Prevent Recurrence A review of this issue has been completed, and an analysis has been performed by the fuel supplier.
On the basis of this analysis, it has i
been concluded that even without the turbine runback and automatic rod withdrawal block protection systems, H. B. Robinson, Unit No. 2 will have acceptable thermal margin with respect to a dropped rod transient.
The results of this analysis also envelope the current reduced temper-nture and power operation.
The results of this analysis also envelope the current reduced temper-nture and power operation.
Following this event, administrative controis were implemented to ensure that both turbine runback and auto rod withdrawal block initiating circuits are not defeated at power levels greater than 70%. Based on the analysis described above, the administrative controls governing the RPI and power range nuclear instrumentation inputs to be the tudi tne runback and automatic rod withdrawal block circuits will be revised to delete the requirement to reduce power to 70%. In general, this action will     be taken when instrument problems in the rod position indication system cause false rod bottom signals leading to needless turbine 1.nbacks, or when a power range NIS channel fails or is taken out of service for maintenance and/or testing. The intent of the remaining controls will be to minimize the time these inputs are blocked. Normal operation will continue to be with the runback initiating circuits in place. No further action is considered necessary.
Following this event, administrative controis were implemented to ensure that both turbine runback and auto rod withdrawal block initiating circuits are not defeated at power levels greater than 70%.
Based on the analysis described above, the administrative controls governing the RPI and power range nuclear instrumentation inputs to be the tudi tne runback and automatic rod withdrawal block circuits will be revised to delete the requirement to reduce power to 70%.
In general, this action will be taken when instrument problems in the rod position indication system cause false rod bottom signals leading to needless turbine 1.nbacks, or when a power range NIS channel fails or is taken out of service for maintenance and/or testing.
The intent of the remaining controls will be to minimize the time these inputs are blocked. Normal operation will continue to be with the runback initiating circuits in place. No further action is considered necessary.
}}
}}


{{LER-Nav}}
{{LER-Nav}}

Latest revision as of 12:45, 16 December 2024

Updated LER 81-001/01T-1:on 810109,turbine Runback & Automatic Rod Withdrawal Block Protection Defeated W/Power Range Channel N41 Being Out of Svc.Caused by Improper Rod Drop Analysis.Administrative Controls Revised
ML20066K959
Person / Time
Site: Robinson 
Issue date: 11/17/1982
From: Cox H
CAROLINA POWER & LIGHT CO.
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20066K946 List:
References
LER-81-001-01T, LER-81-1-1T, NUDOCS 8211290703
Download: ML20066K959 (2)
v • d • e


LER-1981-001, Updated LER 81-001/01T-1:on 810109,turbine Runback & Automatic Rod Withdrawal Block Protection Defeated W/Power Range Channel N41 Being Out of Svc.Caused by Improper Rod Drop Analysis.Administrative Controls Revised
Event date:
Report date:
2611981001R00 - NRC Website
v • d • e

text

NRC FORM 366

" UPDATE REPORT - PREVIOUS REPORT DATE 1/23/81" u.S. NUCLEAR REGULATORY COMMISSION (7-77 F LICENSEE EVENT REPORT 0

COUROL BLOC %: l l

l l

l l lh (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1 6

lo lil lS l C l H lB lR l 2 l@l 0l 0l -l 0l 0] 0l 0l 0l -l 0 l 0l@l 4 l 1l 1l 1l 1l@l l

lg 7

8 9 LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE JO 57 CAT 58 CON'T loIil

"$R$ l I-@l 0l 5l 0l 0l 0l 2l 6l Igl 0l 1l 0l 9l 8l IQl1l 1l1l 7 l 8 l 2 l@

S 7

8 60 61 DOCK ET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h l o l 2 l l0n January 9,1981, with the unit at 100% power, it was determined that operation with l g o,3, lthe RPI System input to the turbine runback and auto rod withdrawal defeated and power l

, o g,, [ range channel N41 input out of service is contrary to the assumptions in the safety l

, o g g analysis prepared during the fuel reload safety evaluation.

Still the probability of l l

g lnot sensing a dropped rod is small since three of the power range detectors were l

l o l, l [ ope rab le. 'Ihis occurrence is reportable pursuant to Technical Specifications l

.9.2.a(6).

No adverse consequences resulted from the above condition.

l oig 80 C DE CODE SUBC E COMPONENT CODE SUBC DE S

ODE [oJ5]

lI l E l@ d@ y@ l Il Nl S l Tl Rl U l@ y@ ]@

7 8

9 10 11 12 13 18 19 20 SE QUE NTI AL OCCURRENCE REPORT REVISION

_E l VENT YE AR

[---j l0l0l1l y

l0l1l l Tl b

l1l R EPoR T NO.

CODE TYPE No.

LER RO

@yg 8l 1l a

_ 21 22 23 24 26 27 28 29 30 31 32 TAKEN AC ON oN PLANT VT HOURS 22 SB IT D FOR S 8.

SUPPLt R MANUF TURER I Glgl34 Gl g

{ Zj g [36Zj@

l 0l 0l 0l l

[}jg

[_qg lNjg lWl1l2l0lg 33 J5 3/

40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h lA review of the H.

B. Robinson Unit 2 FSAR and Fuel Reload Safety Evaluation l

i o identified that the rod drop analysis assumes both turblae runback and auto rod l

g

,,y,,gwithdrawal block.

A new analysis of this event concluded that operation without l

,,,3, g these protective systems is not adverse to safety. Administrative controls, which l

were implemented f ollowing this event, will be revised to delete the 70% power m l restriction.

I 8 9 80 ST S

% POWE R OTHER STATUS Dis O RY DISCOVERY DESCRIPTION lEl@ l1l0l0l@l N/A l

g gl OBSERVATION l

i s AETiviTY CO0 TENT RELE ASED OF RELE ASE AMOUNT OF ACTIVITY LOCATION OF RELEASE [Z_j @ [Zj g l N/A l

l N/A l

i 6 7

8 9 10 tt 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE CI SCRIP TION l0l0l0l@lZl@l N/A l

i i PE nSONNE t imuLS OtSCniPriON@

NuveER l0l0l0l@l N/A l

i H 7

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issue @oEERiPTiON@

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6 SUPPLEMENTAL INFORMATION FOR LICENSEE EVENT UPDATE REPORT 81-001, REVISION 1 I.

Cause Description and Analysis, On January 7,1981, the Power Range Channel N41 was taken out of service.

Previous to this, the Rod Position Indication System (RPI) input to the turbine runback system and auto rod withdrawal circuit had been defeated due to spurious rod drop indications in an effort to prevent unnecessary thermal cycles to Reactor Coolant System (RCS) components. On January 9, 1981, it was determined, by a review of the H. B. Robinson, Unit No. 2 FSAR and Fuel Reload Safety Evaluation, that both of these documents assume that turbine runback and auto rod withdrawal defeat occur follow-ing a control rod drop.

These systems are actuated by any one RPI bottom signal or a rapid flux decrease on any one power range channel.

By having N41 inoperable, a few rods located in the core region nearest N41 might not be detected by the other three power range detectors if they were to drop.

Based on this review, therefore, the event was identified as reportabic pursuant to Technical Specification 6.9.2.a.6.

Since an RCCA drop event did not occur during this time, no adverse consequences resulted from the above situation.

II.

Corrective Action

All atfected systems were immediately returned to service when it was determined that having both inputs to the turbine runback and auto rod withdrawal systems defeated may be contrary to the FSAR and fuel reload

safety analysis

III. Correct ive Action To Prevent Recurrence A review of this issue has been completed, and an analysis has been performed by the fuel supplier.

On the basis of this analysis, it has i

been concluded that even without the turbine runback and automatic rod withdrawal block protection systems, H. B. Robinson, Unit No. 2 will have acceptable thermal margin with respect to a dropped rod transient.

The results of this analysis also envelope the current reduced temper-nture and power operation.

Following this event, administrative controis were implemented to ensure that both turbine runback and auto rod withdrawal block initiating circuits are not defeated at power levels greater than 70%.

Based on the analysis described above, the administrative controls governing the RPI and power range nuclear instrumentation inputs to be the tudi tne runback and automatic rod withdrawal block circuits will be revised to delete the requirement to reduce power to 70%.

In general, this action will be taken when instrument problems in the rod position indication system cause false rod bottom signals leading to needless turbine 1.nbacks, or when a power range NIS channel fails or is taken out of service for maintenance and/or testing.

The intent of the remaining controls will be to minimize the time these inputs are blocked. Normal operation will continue to be with the runback initiating circuits in place. No further action is considered necessary.

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