View source for 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

{{Adams
| number = ML20066K959
| issue date = 11/17/1982
| title = 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
| author name = Cox H
| author affiliation = CAROLINA POWER &amp; LIGHT CO.
| addressee name = 
| addressee affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION II)
| docket = 05000261
| license number = 
| contact person = 
| document report number = LER-81-001-01T, LER-81-1-1T, NUDOCS 8211290703
| package number = ML20066K946
| document type = LICENSEE EVENT REPORT (SEE ALSO AO RO), TEXT-SAFETY REPORT
| page count = 2
}}
{{LER
| Title = 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
| Plant = 
| Reporting criterion = 
| Power level = 
| Mode = 
| Docket = 05000261
| LER year = 2081
| LER number = 1
| LER revision = 
| Event date = 
| Report date = 
| ENS = 
| abstract = 
}}

=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
COUROL BLOC %: l 1
l      l       l    l    l lh 6
(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
58 lg 7           9                      CODE CON'T loIil              "$R$ l I-@l 0l 5l 0l 0l 0l 2l 6l Igl690l 1lEVENT S
68 0lDATE 9l 8l IQl1l 1l1l 7 l 8 l 2 80l@
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
   , 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 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
[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 LER RO _E                                                 R EPoR T NO.                           CODE                 TYPE                       No.
                @yg    a
_ 21 8l 1l YE[---j l VENT 22            23 AR          l0l0l1l 24              26 y
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/
l 40
[}jg 41
[_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
       , ,      g identified            that the rod drop analysis assumes both turblae runback and auto rod                                                                        l
    ,,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 I
m l restriction.
    ;      8 9                                                                                                                                                                  80 ST      S           % POWE R                          OTHER STATUS                 Dis O RY                             DISCOVERY DESCRIPTION OBSERVATION i s lEl@ l1l0l0l@l '                 '          "
N/A                  l     g gl l
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"   ''
N/A l
PE nSONNE t imuLS NuveER               OtSCniPriON@
7 i H 8 9 l0l0l0l@l        11      12 N/A 80 l
LOSS OF OH DAMAGE TO F ACILITY TYPE      DE SC RIP TION i 9 U @]'                                                                               N/A                                                                            l
    '      " 9                                                                                                                                                                  8
                             '                                            8211290700 821117                                                                    NRC USE ONLY PDR ADOCK 05000261                                                                                          ,
7 2 o R 9 issue @oEERiPTiON@
l 10 S                                  PDR                                   l 68 69 lllllllllllll{
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.
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 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.
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.
}}

{{LER-Nav}}