ML19290F202
| ML19290F202 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/13/1980 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| TLL-114, NUDOCS 8003180302 | |
| Download: ML19290F202 (7) | |
Text
.4
,T Metropolitan Edison Company Post Office Box 480 g
Middletown, Pennsylvania 17057 717 944-4041 Wnter's Direct Dial Number March 13,1980 TLL 114 Office of Nuclear Reactor Regulation Attn:
Mr. Harold R. Denton, Director U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
Three Mile Island Nuclear Station, Unit I (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Response to NRC Letter Concerning the February 26, 1980 Incident at Crystal River Unit No. 3 Enclosed please find the responsas to items 1 thru 5 of your letter of March 6, 1980 to all operating B & W reactor licensees concerning the February 26, 1980 incident at Crystal River. These responses are preliminary in nature and may be revised as a result of follow on activities related to items 6 and 7 of your letter. The responses to items 6 and 7 will be submitted in a later letter in accordance with your schedule.
Sincerely, s
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J. G. Herbein Vice President Nuclear Operations JGH:CFM: hah Attachment cc:
J. T. Collins 89\\
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8003180309 ve:reccaan E23:n Cemean s a veer, e ce~ry = c c z tes s ne-
METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER AND LIGHT COMPANY AND PENNSYLVANIA ELECTRIC COMPANY THREE MILE ISLAND NUCLEAR STATION, UNIT I Operating License No. DPR-50 Docket No. 50-289 This letter is submitted in support of the Nuclear Regulatory Commission request concerning the Februarf 26, 1980 incident which occurred at the Crystal River Unit No. 3 Nuclear Station. The responses to the first five items of the NRC's letter of March 6, 1980 are attached. Further, all statements contained in this report have been reviewed and all such statements made and matters set forth therein are true and correct to the best of my knowledge, information and belief.
METROPOLITAN EDISON COMPANY s
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Vice President Sworn and subscribed to me this 13 th day of March, 1980.
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9 TLL-114 ITEM 1.
Summarize power upset events on NNI/ICS that have previously occurred at your plant.
RESPONSE
1.
Discussions with plant operating and maintenance personnel indicate that some minor power upsets have previously occurred. These upsets have involved small partial power losses during maintenance. The ef fects were insignificant and therefore no documentation was generated. No event has occurred which has had a significant impact upon plant ope ra tion.
ITEM 2.
Specifically review the Crystal River event and address your plant's susceptibility to it in general.
RESPONSE
2.
TMI-1 utilizes a 721 series ICS/NNI system unlike Crys tal River's, therefore the specific failures that occurred at Crystal River are not applicable to TMI-1.
Figure 1 represents the power distribution for the TMI-1 ICS/NNI.
Power enters the ICS/NNI from a battery powered inverter (normal supply) or from a 120 VAC regulated bus via an automatic transfer switch (See figure 2).
There are also o separate power feeds within the ICS/NNI:
(1) " HEX" power and " HEY" power - these sources are distributed to various field sensors or transmitters. Loss of either of these sources will res ult in a partial loss of indication for certain plant parameters.
(2) " Auto" power - this source supplies signal conditioning and display powe r fo r a po rt ion of the instrumentation and all of the control fe eds. Failure of this feed would resulp in a plant transient but the PORV and spray valve would remain closed In addition, the ability to assume manual control of some ICS control valves would be maintained.
(3) " Hand" cover - this source supplies a portion of the display instrumen-tation as well as control power for the ICS controlled valves.
Failur e of this supply would result in a loss of manual and automatic control of the ICS controlled valves except Emergency Feedwater. The ICS controlled main feedwater valves would also fail in the mid position and a plant trip would occur.
1 This is true for any ICS/NNI power failure.
TLL-114 (4) "Emercencv Feedwater" oower - this source supplies centrol power for the EFW control valves (EFV 30 A/B). Failure of this supply would cause no plant transient and manual control of the EFW control valves would be available in the control roco from a separate manual control station but automatic control would be lost (modification in progress prior to re star t).
(5) " Fan oower" - this source supplies power to cooling f ans only.
To verify and clarify the plant response to various failures a failure analysis is planned as discussed below.
Response Plan for ICS/NNI Failure Analvsis A detailed f ailure analysis has been initiated. Whereas previous analyses have concentrated on single input / output failures, this analysis will consider internal and external power supplies to the ICS/NNI, including identificaton of significant ins trument losses and single failure modes.
The situation identified in IE Bulletin 79-27 will also be addressed. The intent of this phase of the analysis is to show which combination of components are af fected by power supply failures and what form the failure takes, 4..e., do indicato rs f ail in an identifiable mode and do actuated devic es fail open/ closed or as is.
The results of this study will then be used to perform a plant response analysis and to evaluate the ef fect of operator performance. Included in this phase will be a comparison to Crystal River 3 and an evaluation of potential countermanding signals. The results of this ef fort will be used to determine if modifications are necessary to provide impr oved indication, to further identify for evaluation actuation signals that would challenge the saf ety systems, and to minimize counter =anding signals.
Using the data derived frem these studies, a practical test will be developed which will simulate various power supply failures to validate the results of the analytic ef fort and to disclose potentially unforeseen system interaction.
Changes to equipment will be determined by the results of both the analytic and the practical evaluations. The results will also be f actored into revised operator procedures and training. Scheduled completion of the total study ef fort is September 30,1980.
In light of current shutdown status of TMI-l this schedule is consistent with restart activities.
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TLL-114 ITEM 3.
Set forth the info rmation presented by your representative (s) in the meeting on March 4, 1980.
RESPONSE
3.
The information presented at the subject meeting was essentially preliminary responses to Items 1, 2, 4 and 5.
Written responses to those questions are included here.
ITEM 4.
Address information available to the operator following various NNI/ICS power upset events, including a discussion of:
how the operator determines which information is reliable what information is needed to bring the plant to cold shutdown
RESPONSE
4.
TMI-1 differs from CR-3 in two respects:
a)
ICS and NNI power are not separate b)
AC, not DC, power is supplied to the modules The AC power is supplied from a single bus (ATA) wh ic'- receives power through an automatic transfer switch from either a vital supply or a regulated supply. This bus feeds the ICS/NNI subsystems through six major distribution breakers. Potential power upsets that involve partial or total loss of power are addressed as discussed in response to Item 2.
ITEM 5.
Address the feasibility of performing a test to verif y reliable information tha t remains following various NNI/ICS power upsets.
RESPONSE
5.
The current status of TMI-l allows some testing flexibility. Current plans call for a study of failure modes that will culminate in appropriate testing and resuls analysis (See response to item 2).