ML23251A018
| ML23251A018 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/2023 |
| From: | NRC/OCIO |
| To: | - No Known Affiliation |
| Shared Package | |
| ML23251A034 | List: |
| References | |
| FOIA-2023-000163 | |
| Download: ML23251A018 (1) | |
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!" NUCLE AR REGUL.ATORY COMMISSION
{ 'f wasmO 10N, D. C. 20666 JM 0 61992
% ,.... f HEHORANDUM FOR: Thomas E. Hurley, Director, NRR Thomas T. Hartin, Regional Administrator RI Edward L. Jordan, Director, AE00 < r .
Eric S. Bu.kjord, Director, RES fROM: James H. Tay1or Executive Director for Ope.ations
SUBJECT:
staff ACT10NS RESULTING FROM THE INVESilGATION Of THE AUGUST 13, 1991, INCIDENT AT NINE HILE POINT UNIT 2 (HUREG1455)
An advance copy of the subject resort was transmitted to you by memorandum dated October 11, 1991, from the line Hile Point Ili team leader, Jack Rosenthal. The report documents the team's efforts in identifying the circur.stences and causes of the August 13, 1991 incident, together with f t:.dtngs and conclusions which form the bases for followup ar.tions.
The purpose of this memorandum is to identify and assign responsibility for generic and plant specific actions resulting from the investigation of the Nine Mile Point incident as documented in NUREG 1455. In this regard, you are requested to review the enclosure which specifies staff actions resulting from the investigation of the Nine Mile Point incident. You are requested to determine the actions necessary to resolve each of the issues in your area of responsibility and, where appropriate, identify additional staff actions or revisions as our review and understanding of this event are refined.
Although not identified as a specific problem during the Nine Mlle Point Unit 2 event, the 11T identified a vulnerability of electronic components to ground faults and electromagnetic emissions generated by a transformer f ault.
I have not indicated any staff actions in the enclosure for this vulnerability '
because of staff actions already underway. The Office of Nuclear Reactor Regulation previously identified to the Office of Regulatory Research the need to develop a regulatory guide that add.-esses acceptar.ce criteria for electromagnetic interference, surge withstand capability, and radio frequency iaterf ererae in digital systems.
I intend to monitor the resciution of each action item. Within 30 days of the date of this memorandum, pleace provide a written summary of the plans, schedule, status, and point of contact for each item within your area of responsibility listed in the enclosure, in addition, I request that you prepare a written status report on the disposition of your items (and anticipated actions for uncompleted items) within six months.
The resolution of the plant specific actions is to be documented in a single report and each generic action item will be individually tracked via the [00's work item tracking system (WITS). Overall lead responsibility for the preparation of the staff's single report on plant specific actions rests with f/ Toll 300 % M r N
ff' Enclosure
Hultiple Addressees 2-Region 1. Other offices involved in plant specific actions are to coordinate their efforts with Region 1. The Director, AE00, will prepare a closcout report which identifies the resolution or disposition of each 111 finding and conclusion. Thus, the Director, AE0D, shocid also be kept informed as to the resolution or disposition of each action item assigned, in accordance with the revised NRC Hanual Chapter 0513, 'Incide,it Investigation Program,' the resolution of each 111 finding and conclusion is subject to independent assessment as to its adequacy and completeness and further action may be taken I at a later date. Where a significant policy question may be involved in the '
resolution of an action item, it is requested that I be notified so that the need for review by the Comission may be evaluated. Additionally, you should determine whether any corrective action deemed necessary or appropriate will ,
result in plant specific or generic backfitting and, if so, ensure that the procedures in NRC Hanual Chapter 0514 and the CRGR Charter are followed.
The enclosure is based on the Nine Mile Point !!T's findings and conclusions ,
contained in NUREG-1155. Accordingly, it does not include all licensee actions, or cover all NRC staff activities associated with normal event follow up such as facility inspections or possible enforcement actions. These items are expected to be defined and implemented in a routine manner.
/
AT H xecutive Director for Operations
Enclosure:
Staff Actions Resulting from the August 13, 1991, Event at Nine Mile Point.
Unit 2 cc w/ enclosure:
J. Sntezek, OEDO H. Thompson, OEDO J. Blaha, OEDO R. Lobel, DEDO C. Kammerer,-GPA J. fouchard, GPA R. Hauber, GPA S. Ebneter, RIl A. Davis, Rlli R. Martin, RIV J. Martin, RV R. fr. ley, ACRS
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STAFF ACTIONS RESULTING FROM THE INVESTIGATION OF THE AUGUST 13, 1991, INCIDENT AT HINE HILE POINT 1 UNIT 2 (
REFERENCE:
- 1. Issue: Adequacy of Uninterruptible Power Supply Installations ,
(
Reference:
Sections 1, 3.2, 4.3.4, 4.3.5, 4.3.6, and 8.4)
At Nine Mile Point 2 the nonsafety related UPS that were lost obtaind control logic power from an ac maintenance power source within the plant but external to the UPS itself and hence, subject to the electrical perturbation due to the fault of the main transformer. The preferred source would be internal to the UPS or a stable de source not susceptible to similar electrical perturbations. All five UPS were identical and hence, all subject to the same design problem. A similar arrangement may exist in other installations, including safety related installations, at other plants where an UPS or discrete inverter is used to power instrumentation and control loads.
At Nine Mlle Point 2, the nonsafety related UPS that were lost contained internal batteries that could have maintained logic functions when the -
logic power ac input was lost. However, the batteries had not been replaced for several years and were, therefore, dead when called upon to function. Testing and periodic re31acement of the control logic power supply batteries was not part of tie preventative maintenance program. In addition, the technical manual was not clear on the purpose of the batteries. The manual indicated that the batteries needed periodic replacement every 4 years. However, this time was too long given internal environmental temperatures. A comprehensive consolidated list of maintenance requirements was not provided. A similar lack of maintenance or maintenance weaknesses may exist with other UPS installations, including safety related installations, at other facilities.
ACTION RESPONSIBL1 0FFLCL GAJEQR1
and nonsafety-related UPS with regard to similar vulnera-bilities. Specifically include consideration of the normal source of logic power, other dependencies external to the UPS, and the potential use of the Exide-UPSs that failed at NMP 2 in safety related applications, i
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ACTION f1}PQM101E OfflCE .(MfLOM
- b. Evaluate the actions taken by Region 1/ Pl ant-the licensee at NMP 2 to address NRR Specific design and maintenance issues for the UPS.
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- 2. Issue: Adequacy of instrumentation and Emergency Operating Procedure !
Integration
Reference:
Sections 1, 3.3, 4.5, 5.3, 5.4. 5.5, I 5.6,8.2and(8.5) :
At Nine Mile Point 2 loss of the control rod position indication required !
operators to enter their procedures for ATWS. This complicated the recovery actions by imposing additions) tasks and constraining operator actions with regard to level and pressure. In addition, loss of front panel neutron monitoring indication and other display unnecessarily-compounded the operators' tasks. for Nine Nile Point 2, other DWR's, and >
some PWR's rod position indication is powered from a single source, typically a nonsafety related instrument bus. (Note: BWP,6 have dual control rod reed switches), failure of that bus may cause a reactor scram due to loss of BOP instrumentation and control. Under such circumstances, operators are challenged by a transient with loss of rod position and front panel neutron flux indications. This may place an undue burden and reliance on the plant operators to sort through misleading indicators during a high stress and confusing event.
A minimum complement of instrumentation to safely shut down a plant has been previously provided within the normal licensing process and following IE Bulletin 79-27. Subsequent actions such as the detailed control room design reviews" and development of symptom based f4Ps should have provided a reasonable degree of integration of procedures, potentially ambiguous
' indication, human factors considerations, and operator workload. However, when the integrated )icture is reviewed in response to this event, there l appears to be undue )urden and reliance on operators for loss of some '
! instrument buses. The !!T was not able to provide specific bases to
! generalize the concern to other events and other plants. However, NRC staff reviews in these areas have not been fully integrated. Thus, there l
l is concern that the problem may be a broad one, i
RESPONSIBLE OFFICE C ATf GQ,R,1 ACTION a.- Audit EPGs for instrumentation NRR LWR associated with manual operator Generic actions for the following four l (4) critical safety functions:
'l. Reactor Pressure Vessel (RPV)
Control - Level and Pressure
- 2. Primary Containment Contro)
- 3. Secondary Containment Control
- 4. ftadioactivity Release Control 2-E
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ACTION- RSPONSIBLEOff.10.1 CA1EGORY q
( b.LReviewthelossofpower NRR LWR vulnerability of.these Geneiit instruments.
, c. Evaluate the need for alternate NRR BWR RPl or providing safety grade Generic power..
- 3. Issue: Adequacy of Emergency Operating Procedures and Associated-Training (
Reference:
Sections 1, 3.3, 5.3, 5.4, 5.5, 5.6, 8.2,
'O.7 and 8.8) ,
Generally, the emergency o>erating procedures (EOPs)-and associated training were helpful to tTe operators in' coping with the event. However, some shortwomings were noted by the !!T. .The E0Ps are_ based on the +
assumption that control of key parameters, such as reacter power,-
pressure, and level, are of equal importance and are to be addressed with equal priority.1 They are taught- that actions to control one parameter affect other paremeters.. At Nine Mile Point, operators were directed to restore reactor water level using the reactor core isolation cooling system (RCIC) which in conjunct %n with unisolated plant steam loads caused a significant pressure: reduction. They were also directed to
- stabilize pressure until they determined that-the plant would remain
-shutdown. They had no direction as to which parameter took priority and had not received training in hcw to control decreasing pressure while increasing level simultaneously.
The procedures provide a useful roadmap, but by design contain few
-directed actions, or equipment oriented anticipatory. actions. The Nine Mile Point post-scram procedure was_not integrated and complementary to the E0Ps.- ;
-During the event, the' operators'had to cope with a reactor-trip with loss
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of annunciators,'as well.as other instrumentation and control issues.
- Theyihad not been trained.on loss of. all annunciators alone, nor in
. conjunction with a plant scram. Loss of annunciator training had been pl anned.: Lossiof an instrument bus can cause'a plant: scram due to loss of BOP instrumentation and control, and loss of many. annunciators.
RESPONSIBLE OffI,(E CATEGORY-6.QJ1QH .
- a. Ev'aluate the. need to review the NRR LWR adequacy of BWR EPGs with Generic respect to:1 prioritization'of control of critical safety.
functions and the adequacy of guidance _on_ stabilizing a
- decreasing reactor pressure.
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RESPONSIBLE __Of fICE CATLGQR1 EJ1QN
.b. Evaluate the need to. review the NRR- 'n adequacy of training programs - Gwr .:
'and associated emergency procedures with' respect to training for. loss of annunciators combined with a scram or other combinations of t events, .
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- 4. . Issue:. Adequacy of regulatory guidance regarding nonsafety-related
- i; equipment'and-instrumentation raquired for-accidents.
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Reference:
Sections 1, 7.1 and 8.11)
- The-!!T team concluded that.the NRC has not presented;a clear position to the
- regulated-industry concerning control of equipment configuration and treatment ,
of-important nonsafety-related equipment'such as the UPS that were lost at Nine Mlle Point.-- The maintenance monitoring rule, and its planned implementing regulatory guides may-be expected to clarify this issue with!
respect lto basic maintenance practices. Other practices, such as contrni of-L drawings and technical' manuals might-not ta covered.
MSPONSIBLE OFTLC1 CATEGORY MI[QM _
- t. . Evaluate the need to provide RES -LWR additional regulatory guidance Generic thatLconveys the staff ' -
expectationstregarding _.
L maintenance on important-
" - nonsafety-related equipment.
- 5. Issue: Shift Coping.(
References:
Sections 1, 3.3, 5.5 and 8.2)
.During the first fifteen minutes of the event at Nine Mile Point Unit 2, theLoperating crew was exceptionally busy executing their' emergency E'A operating. procedures, emergency planning procedures,-and coping with V losser of-communications, annunciators, and.information systems such as u the_ plant computer and SPDs. They also had to determine what '
n instromentation and controls,-and associated equipment was operable and p -what was tlost, and_ had to verify. indication = in the control room using local' indicators. :While all these aspects needed attention, the assistant station shift supervisor, normally the second'in command in the control room,. assumed the duties of. the shift -technical advisor.
This put h
l additional burden on the station shift supervisor. . 0ther plants-have l ' .similar control room organizations and have experienced similar problems during events.
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ACTIO!(_ RESPONSIBLE OFFICE CATEGORY
- a. Evaluate the need to review the NRR LWR adequacy of control room Generic staffing during simultaneous implementation of E0Ps- and ERPs by noraal shift crew.
- b. Incorporate into the ongotg NRR LWR review of STA implementatier. Generic consideration for the integration of the STA function into the shift crew during command changes.
- c. Evaluate the actions being taken Region I Pl ant-by the licensee at Nine Mile Specific Point to address shift coping issue 2.
- 6. Issue: Condensate Booster Pump Injections at BWR 5 design plants
(
Reference:
Sections 1, 3.4, 5.3, 5.6 and 8.10) u At Nine Mile Point 2, while attempting to restore reactor water level to normal, reactor pressure decreased and an inadvertent condensate booster l pump injection occurred. Anticipatory action to close valves in the flow l path or trip the running condensate booster were not taken. Inadvertent l
condensate booster-pump injection following plant scram has occurred at L Nine Mile Poir.t Unit 2 on two other occasions.
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! Also industry operating experience indicates that BWR 5 design reactors are.more susceptible than other BWR designs to uncontrolled booster pump injectio s. BWR 6 design reactors have booster pump trips on high reactor vessel 1 tel, and the RCIC design in applicable older reactors is less effective in reducing reactor vessel pressure, resulting in fewer condensate booster pump injections.
ACTION RESPONSIBLE OFFIG1 CATEGORY L a. Consider the need for actions by Region I/ Plant-the licensee at NMP-2 to address NRR Specific
" condensatt k oster pump injections including I
consideration of the need for automated booster pump trip, L anticipatory procedural I
guidance, and mass and heat l -- balance calculations.
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- 7. Issue: Adequacy of Plant Specific Operating and Recov.ary Procedures
(
References:
Sections 1, 3.3, 3.4, 3.5, 3.6, 5.3, 5.6, 8.8 and 8.9)
At Nine Mile Point, the scram procedure did not complement the emergency o>erating procedures for ATWS conditions. For example, it did not support t1e operators by specifying the priority (immediate) actions to be used in conjunction with E0Ps for all scrams, in addition, operators were unnecessarily challenged by a lack of certain recovery procedures.
Operators relied on experience based knowledge to restore power to UPS loads because no procedure had been written for recovery from a loss of UPS. Operators closed feedwater pump suction valves prior to restarting a condensate booster pump in accordance with the normal startup procedure because there was no other guidance.
ACTION RESPONCIBLE OFFICE CATEGORY
- a. Evaluate licensee corrective Region i Pl ant-actions with respect to the Specific procedures discussed above.
Include consideration of the need for the scram procedure to segregate and make a distinction between immediate actions and supplemental actior.s in accordance with ANSI /ANS-3.2, 1982 as discussed in Section 5.6.1 of the IIT report.
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