ML20032E803
| ML20032E803 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/09/1981 |
| From: | Hukill H METROPOLITAN EDISON CO. |
| To: | Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| REF-SSINS-6820 IEB-79-27, L1L-310, LIL-310, NUDOCS 8111230293 | |
| Download: ML20032E803 (9) | |
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Metropolitan Edison Company Post Office Box 480 II Middletown, Pennsylvania 17057 Writer's Direct Dial Number Novanber 9,1981 LlL 310 g
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MI Office of Inspection and Enforcement D
Attn:
R. C. Haynes, Director 6;
NOW 0 BW I Region I
-3 U. S. Nuclear Regulatory Commission Nd7 '
631 Park Avenue f
9 King of Prussia, PA 19406 as
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Response to IE Bulletin 79-27 As a result of the events at Oconee (November 10, 1979) and Crystal River (February 26, 1980), the NRC issued IE Bulletin 79-27 and a letter of March 6, 1980 requesting information.
In response Met Ed sent the following letters:
Feb ruary 29, 1980 (TLL 102)
March 13, 1980 (TLL 114)
March 17, 1980 (TLL 117)
May 29, 1980 (TLL 245)
June 30, 1980 (TLL 309)
TMI-1 Restart Report Supplement 1 Part 1 Question 38 TMI-l Restart Report Supplement 1 Part 3 Question 12 Discussion before the TMI-l ACRS Subcommittee November 29, 1981 and June 25, 1981 Subsequently a loss of power study was performed for the ICS/NNI system at TMI-1.
The conclusion of that analysis was that certain failures would lead to the loss of instrumentation required to bring the plant to safe shutdown.
The attachments to this letter discuss our solutions by way of modifications, changes to procedures and operator training and respond to NRC questions related to IE Bulletin 79-27.
Verification by testing is complete, and these tests are under review. We will inform you of the significant results of this review.
Sincerely.
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kill 8111230293 811109 Director, TMI-1 HDH:LWH:vjf PDR ADOCK 05000289 i
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Metropohtan Edison Company is a Member of the General Pubbc Utit:es System
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NRC Questions of IE Bulletin 79-27 and Other Additional Questions item 1.
Actions which wi!! allow the operator to cope with various combinations of loss of instrumentation and control functions. This includes changes in (A) equipment and control systems to give clear indications of functions which are lost or unreliable;. B) procedures and training-to assure positive and safe
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manual response by the operator in the event that competent instruments are.
unavailable.
4 Resoonse:
Detailed actions for operators in the csse of NNI/ICS power failures resulte'd in revisions to Emergency Procedures discussed in our letter dated May 29, 1980 (TLL 245).
See attachtrent 1, item E for further details.
Item:
2.
Determ i nat ion of the ef f ects of various combinations of loss of instrumentation and control functions by design review analysis anc. verification by test.
Response
The loss of power study identified areas to be corrected.as shown in attachment 1,
itea B & C.
In August, 1981 verification tests were conducted which are still under review.
item:
1 i
3.
Correction of electrical deficiencies which may allow the power operated relief valve and pressurizer spray valve to open on non-nuclear instrumentation j
power failures, such as, the event which occurred at Crystal River, Unit 3 on February 26, 1980, i
Response
See response to item 6 (2) and (3) of our letter of March 17, 1980 (TLL 117) and the information provided in the cover letter.
Item:
4.
Subm'it to the NRC a written response to l&E Bulletin 79-27.
l Resconse:
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The initial response to IE Bulletin 79-27 was submitied by Met-Ed on February i
-29, 1980 (TLL 102) which made prev ious reference to the TMI-1 Restart Report Amendment 11 Supplement 1 Part 2 Question IS.
Additional items not responded in the initial letter are answered below:
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Question A. Review the class-1-E buses supplying power to safety and non-l safety' related instrument, tion and control systems which could af fect the ability to achieve a cold shutdown condition using existing procedures or proceduc es developed under item 2 below.
For each bus:
1) identify and review the alarm and/or 'ndication provided in the control room to alert the operator to the loss of j
power to the bus.
2) identify the instrument and control. system loads con-l nected to the bus and evaluate the effects of loss of l
power to these loads including the ability to achieve a cold shutdown condition.
3) describe any proposed cesign modifications resulting from thase reviews and evaluations, and your proposed schedule for implementing those modifications.
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Answer A.
See Attachment item D for details.
i Question B. Prepare emergency procedures or review existing ones that will be used by control room operators, including procedures required to achieve a cold shutdown condition, upon loss'of power to each class 1-E and nor.-class 1-E bus supplying power to safety and non-safety related instrument and control systems. The emer-4 i
gency procedures should include:
1) the diagnostics / alarms / indicators / symptom resulting from the review and evaluation conducted per item 1 above.
2) the use of alternate indication and/or control cir-cuits which may be power from other non-class 1-E or class 1-E instrumentation and control buses.
3) methods for restoring power to the bus.
I Describe any proposed design modification or administrative controls to be implemented resulting from these procedures, and your proposed schedu le f or implementing the changes.
Answer B:
See Attachment 1, item E for details.
Questions C.,Re-review IE Circular No. 79-02, Failure of 120 Volt Vital AC Power Supplies, dated January 11, 1979, to include both class J
1-E and non-class 1-E safety related power supply inverters.
Based on a review of operating experience and your re-review i
of IE Circular No. 79-02, describe any proposed design modi-fications or administrative controls -h3 be implemented as a
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result of the re-review.
Answer C: See Attachment 1, item D 4.
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SUMMARY
Loss of NNI/ICS Power A.
Overview Tbe f oi Iowing is a summary of the design review, verification tests, changes in
- controls, additional instrumentation, controls and alarms, and new operating procedures to be implemented at TMI-1 based on our review of the consequences of loss of power to the NNI/lCS.
B.
Design Review The design revlew was perf ormed which indicated that for losses of some power feeds to the NNf/ICS, inadequate instrumentationLexisted for-power range operation or post-trip decay heat removal using normal methods.. Control system action could nave produced underfeeding when critical, overcooling af ter trip, and reactor coolant system depressurization. Furthermore, the occurrences of 3
these power losses were not unambiguously indicated to control room operators.
The design review recommended actions in the areas of plant modifications and procedures with the intent of:
c 1.
reducing probability cf loss of power, 2.
enabling operators to recognize loss of power,.
f 3.
enabiing decay heat removal using normal methods,
l providing gutdance to operators for dealing with loss of power.
C.
Verification Tests Veri f ication tests perf ormed at TMI-1 confirmed the conclusions of the design review.
The results of the testing will be provided at a later date.
D.
Control and Instrument Changes and Additions i
Plant modifications performed as a result of this study included:
I 1.
Changes to prevent overcooling 3.
Atmospheric dump valve control shifts to manual on loss of
" Hand" power. Manual control from the control room is in-dependent of NNi/ICS power. (See TLL 671, January 21, 1981.)
b.
Atmospheric dump valves fall closed on loss of signal.
c.
Turbine bypass valves fait closed on loss of " Hand" power.
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2.
Changes to prevent depressurization a.
Pressurizer spray valves f all closed on loss of signal.
b.
Alternate cor.', ol of reactor coolant system makeup flow independent of NNI/lCS.
3.
Instrumentation added to permit post-trip decay heat removal via steam generators. These instruments are independent of NNI/ICS.
a.
Steam generator pressure A & B b.
Steam generator level A & B c.
Emergency feedwater flow A & B d.
Reactor coolant system pressure e.
Pressurizer level f.
Makeup tank level g.
Cold leg temperature A & B h.
Hot leg temperature A & B.
4 Indication and control added to aid in determining power supply status anc recuce probability of loss of power.
a.
Control room annunciators to indicate:
i.
loss of power to ATA bus which feeds NN!/lCS 11.
loss of any subfeed to NNI/ICS.
b.
Power supply status lights in control room indicate status of key power feeds to control s and instrumentation. Loss of power on any of these f eeds causes a loss of NNI/lCS power alarm.
c.
A remote manual bus transf er actuated from the control room to provide backup to the automatic bus transfer supplying ATA.
Figures 1 and 2 summarize the before and af ter NNI/ICS power distribution.
The results of these changes are to:
1.
Provide operators unambiguous indication of loss of power to key instrumentation and control circuits.
2.
Pl ace control systems in conditions which prevent undesirable plant
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response on loss of power.
3.
Insure adequate instrumentation and control to permit decay heat removal using normal methods (secondary plant with main or emer-gency feedwater supplying steam generators and using turbine
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bypass or atmospheric dump valves).-
These modifications have been incorporated into the control room in conjunction with the human factors engineering review. Alarm and indication locations and label ing have been.specif ied to insure prominence when operator attention is required. These modifications will be complete.before plant restart.
E.
Operator Procedures and Training Operator actions required to achieve stable plant conditions are dependent on which power supplies are lost. When any of the NNI/lCS _ feeds _ are deenergized an alar m on the main annuciator-panel energizes.
Power supply monitor lights below the annuciator indicate the status of 6 key power feeds. Loss of 4 of the 6 power feeds.have a minor impact on the plant in that operation at power may continue. For tness situations folIowup operator action is required to transfer individual instrument power supplies or supply alternate cooling'to equipment.
- Loss of either "rland" or " Auto" power prevents operation at power and requires opera tor actions to control f eedwater f low, makeup f low, and turbine bypass or -
atmospheric camp val ves.
If' main feedwater is not available or cannot be acequately controlled, emergency feedwater will be initiated and controlled from the control room independent cf tne NNI/ICS.
Procedura! changes are being prepared to provide guidance to operators under these conditions of NNI/lCS power loss which ref lect the plant modif ications made as a result of the design review.
Procedure revisions and operator training on modifications and procedures wil l be completed before restart of TMI-1.
t F.
Summary A design review of the consequences of loss of power to NNI/lCS indicated that for some failure nrimary feed-and-bleed would be required to maintain core coolng. P lant modi f ications which wi ll be in place at the time of TMl-1 restart enable the use of steam generators to provide core cooling foi lowing loss of power to NNI/lCS.
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