ML20129F455
| ML20129F455 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/26/1985 |
| From: | Butcher E Office of Nuclear Reactor Regulation |
| To: | Randazza J Maine Yankee |
| References | |
| NUDOCS 8507170342 | |
| Download: ML20129F455 (10) | |
Text
,}
~
June 26, 1985 DISTRIBUTION:
Docket No. 50-309
Local POR Gray File s
ORB #3 Rdg s
Mr. J. B. Randazza HThompson n
Executive Vicy President 0 ELD Maine Yankee Atomic Fower Company EJordan 83 Edi. son Drive BGrimes
' Augusta, Maine 04336 JPartlow PSears
Dear Mr. Randazza:
SUBJECT:
1 INADEQUATE CORE COOLING INSTRUMENTATION SYSTEM FOR MAINE YANKEE ATOMIC POWER STATION We have reviewed your submittals dated March 8 and March 25, 1985 in response to the NRC Evaluation and Request for Additional Information dated November 14, 1984. We find that your response is not complete and further clarification is required. The additional information requirad is related to the functional redundancy of the Primary Inventory Trending System (PITS), inventory trending with pumps-on, level indications to be integrated into procedures, the plant specific analysis demonstrating the acceptability of the PITS, and the reverse indication caused by pumps-on dynamic head. The enclosure to this letter consists of our evaluation of the additional information provided-in your above referenced letters. Our concerns and requests for additional information are contained in
'the attachment to the enclosure.
We request that you provide us your schedule for completing this licensing
. z action' including your responses to our concerns and requests for additional information within 30 days of your receipt of this letter.
The information pequested in this letter affects fewer than 10 respondents; therefore OMB clearance is not required under P.L.96-511.
Sin _cerely,
^
t s
s Edward J. Butcher, Acting Chief Operating Reactors Branch #3 Division of Licensing
Enclosure:
"~
As stated cc w/ enclosure See next page omO U
- n ORB #3:DL ORB #3:DL 0)1M}4. [
P. eutzer PSears:dd _
6/a/85 FJButcher 6
/85 6/v/85 8507170342 850626 PDR ADOCK 05000309 P
,PDR
E EVALUATION OF ADDITIONAL INFORMATION PROVIDED ON UNADEQUATECORECOOLINGINSTRUMENTATION(ICCI) SYSTEM FOR MAINE YANKEE ATOMIC POWER PLANT In response to the NRC Evaluation and Request for Additional Infomation dated November 14, 1984, Maine Yankee Atomic Power Company (MYAPCo) has provided the submittals dated March 8, and March 25, 1985. The staff in conjunction with its contractor. Oak Ridge National Laboratory (ORNL) has reviewed the MYAPCo submittals. A sumary of our review and evaluation follows.
1 Measurement Errors in the Primary Inventory Trend System An analysis 6f measurement errors for the Primary Inventory Trending System (PITS) has been provided. Maine Yankee accuracy calculations are based on the vendor's published test results for the particular type of transmitter used in the PIT System. In these calculations, the Root-Sum-Square (RSS) method is used to combine the accident condition effects on the transmitters' accuracies. The total system inaccuracies include the environmental and radiation effects on the transmitters, the reference leg heatup, the effects of flashing of dissolved gases, and the recorder accuracy. Expected uncertainties are indicated in the following tables:
Transmitter Error Band in Percent of Span Transmitter Nomal/SGTR SLB LOCA PT3001 11.0
- 7.0
- 10.0 PT3002
- 1.0
- 8.0 111.0 PT3003 11.0 9.0 113.0 Total System Inaccuracies in Percent of Span Transmitter Nomal/SGTR SLB LOCA PT3001
- 1.1
-7.0, + 11.0
- 10.0, + 16.0 PT3002 11.1
-8.0, + 12.0
-11.0, + 16.0-PT3003 11.1
-9.0, + 13.0
-13.0, + 19.0 4
ll 6e.
l Based on an ahalysis performed at ORNL to establish a criterion for acceptable uncertainty oY level measurement for a postulated maximum sized break that falls in the small break category (0.1 sq. ft), the uncertainty claimed for the generic Westinghouse system of 26% was found to be acceptable on the basis of certain assu:nptions about operator confidence and time available for response. For a large uncertainty of 115%, however, there is a greater probability of inappro-priate operator action." With a positive uncertainty, the actual water level could be well down into the core with the inventory system still indicating that the core was covered. The increasing temperatures indicated by the core exit thermocouples would still give the operator warning of an approach to inadequate core cooling. With the maximum negative uncertainty, however, the inventory system would indicattLmuch less water in the core than actually existed. By the time the indic5tions of the core exit thermocouples begin to increase, the operator might be misled into far more drastic actions than necessary, such as depressurization and activation of low pressure injection. This action could produce an over cooling transient and severely stress the reactor. In addition, from the standpoint of measurement system credibility, too large an uncertainty figure would have a definite negative impact. In our opinion, the 16% uncertainty allowed for the generic Westinghouse RVLIS is probably adequate. A large un-certainty, however, might lead the operators to ignore the inventory measurement.
From an engineering standpoint, an uncertainty of 16% is attainable; therefore, we will require the MYAPCo to justify its large uncertainty (MYAPCo analysis shows potential errors as high as 19%) on the basis of procedure action items and plant specific operator response or to propose system modifications to improve the accuracy to an uncertainty of 16%. The staff concern is also described in the Attachment to this evaluation.
/
Pumps-on Indication of Voiding The PITS is designed to trend mass inventory in the reactor vessel during circumstances similar to those which occurred at TMI, i.e., gradual loss of RCS pressure and very low RCS circulation rates. During the early phase of such an accident, the reactor coolant pumps are running and the operator monitors the i
._ m
RCS margin to. saturation. The Emergency Operating Procedures will require the operator lo stop all reactor coolant pumps before the margin to saturation is lost.
NUREG-0737 II.F.2 Clarification Item (4) states that the indication of ICC must be unambiguous in that it should have the following properties:
a.
It must indicate the existence of inadequate core cooling caused by various phenomena (i.e., high-void fraction-pumped flowaswellasstagnantboil-off);and b.
It must not erroneously indicate ICC because of the presence of -an' unrelated phenomenon.
Based on our review, MYAPCo does not have an indication of system voiding with-RCS pumps on. Therefore, we will require the justification from the licensee to address this concern, which is also described in the Attachment to this evaluation.
Display Locations The drawings provided of the control board vertical section and bench board indicate the layout of the PITS recorder and the controls and indications of reactor coolant pumps operation. The PITS recorder is located in the lower left corner of the vertical section with the reactor coolant pump controls and status indication located on the right hand section of the bench board approximately 8 feet from the recorder.
Ability to Withstand LOCA Environment i
The PIT transmitters have been tested for use in the Maine Yankee Containment in post-LOCA and main steam line break conditions. Additionally, two of the trans-mitters, which are located in the instrument sump, are submerged in post-LOCA 3
o e -
l i
conditions. This model transmitter has been submergence tested by the manufacturer 1 Maine Yankee's qualification document, QDR5436-038-0138-2, documents the qualifications of the PITS transmitters for the post-LOCA and
~
steam line break conditions. During the 1985 refueling outage, the cables extending to the PITS transmitters, although qualified for post-accident conditions, will be protected such that they do not become wetted in the submerged condition. Based on our reviev, we find this response to be satisfactory.
Comon Mode Failure The only location,in_which all three d/p transmitters are susceptible to a
~
comon failufe'is in the compartment below the pressurizer, where a single high-energy line break could damage the reference lines to all three trans-mitters. To eliminate this potential common failure, during the 1985 refuel-ing outage the reference line for the 3003 transmitter (reactor vessel top to the bottom of the hot leg) will be re-routed from a separate reactor vessel head penetration through an area which is separated from the reference lines servicing the other transmitters. The PITS is of interest to the operator after margin to saturation is lost and the reactor coolant pumps are stopped.
It provides the operator with secondary infonnation which is not required to directly support automatic or required manual action. Conversely, a mal-function of the PIT system will not prevent the operator from initiating a required action.
r l
Based on our review, we find this response to be satisfactory. However, the staff concern of the functional redundancy in terms of the single failure criterion stated in NUREG-0737, Appendix B is described in the Attachment to this evaluation.
4
l Dissolved Gases in the Impulse Lines i
The license.e has evaluated the effect from the flashing of dissolved gases and j
concludes that it will have a negligible effect on the operation of the PITS.
The results of the evaluation showed that the vertical displacements could create a deviation in the PITS output of approximately 2% for transmitters 3001 and 3003 and approximately 1% for transmitter 3002. Based on our review, we find this response to be satisfactory.
Overrange of Pressure Transmitters s
The effects of.Jong term overranging of the PITS transmitters provide a maximum zero shift of t1% of the upper range limit for a 2,000 psi overpressure for transmitter PT3003 and 13% of the upper range for transmitter PT3001. PT3002 is not overranged during normal operation. The maximum amount of overpressure of'PT3001 and PT3003 during normal operation is approximately 20 psi, which amounts to a zero shift of less than one inch of water on PT3003, and less than 0.05 psi for PT3001. Based on our review, we find that this response is not clear in terms of the downscale overrange of PT3002. The concern is described in the Attachment to this evaluation.
Conformance to NUREG-0737 Design Requirements i
MYAPCo was asked to show schematically the final ICC Instrumenation System
(
and identify any deviation from II.F.2 Attachment 1, and the Appaidix B to l
NUREG-0737 design requirements other than the CET backup display. The l
schedule and the plan for upgrading the backup core exit thermocouple system l
and CET Inputs to the SP94 and PITS or justification of any deviations from the design requirements were also requested.
Two schematics were provided showing the PITS and the balance of the ICC system.
Isolation between safety class and non-safety class hardware is not shown by the block diagrams although the response indicates that isolation has been l
l 5
C>
4 provided. Currently there are eighteen qualified CETs, of which eight CETs, 2 per quadra5t, are used for the backup display. This does not meet NUREG-0737. Item II.F.2 requirements of 16 qualified CETs. Therefore, justification of thc deviation is required. This concern is also described in the Attachment to this evaluation.
Status of ICCI System MYPACo was asked to describe the operational status of the final ICC System, and identify any as-built deviations of the system from previous design descriptions. MYAPCo respanded that the ICCI system was installed during the cycle 6/7 refuelfpg outage. The system has undergone operational testing since that time and will be available for use following receipt of NRC approval of Maine Yankee's ICC analysis. With the exception of the changes mentioned elsewhere in this response, to the best of the licensee's knowledge there are no additional deviations to the design description provided with its letter dated April 29, 1983. We have found that the response will be satisfactory pending the staff's review of the licensee's plant specific analysis, which will be available in August 1985.
Conclusions In summary, we will require additional information with respect to the functional redundancy of the PITS, inventory trending with pumps-on, level indications to be integrated into procedures, the plant specific analysis demonstrating the acceptability of the PITS, and the reverse indication caused by pumps-on dynamic head. Our concerns enumerated in the Attachment to this evaluation should be addressed in order that the staff can complete its review.
6 I
i X
ATTACHMENT 1
REQUEST FOR ADDITIONAL INFORMATION ON
)
INADEQUATE CORE COOLING INSTRUMENTATION FOR MAINE YANKEE ATOMIC POWER PLANT 1.
Do the transmitters that provide functional redundancy by virtue of their overlapping ranges have independent IE power supplies and other features qualifying them as redundant? Note: All three dp transmitters are displayed on a single three pen recorder - so that displays, as least, are not redundant. 'Are any modifications to be proposed to meet the single failure requirement?
_ 3. = = --.
2.
Will the !z transmitter (-57.7' to +57.7') show voiding with pumps on?
~
If not, why is inventory trending with pumps-on not provided?
3.
How are level indications integrated into procedures? In particular, what interpretation guidelines are given the operators for various circumstances where indications may be misleading? (See 5th paragraph, page 5, of April 29, 1983 submittal,MN-83-83.)
4.
What is the status of the " Plant Specific Analysis" demonstrating the acceptability of the PITS during various accident scenarios as promised in response to Item 9 of Enclosure 2, MN-83-83 (scheduled for submittal in August 1985)?
5.
The DCRDR is said to be completed. What are the findings and recommendations with regard to ICC displays and interpretations? Our observations are that pump status and level indication are at opposite ends of the panel.
6.
According to our interpretation of the error analysis, level indications can be as much as 10 ft. to 22 ft. in error during a small LOCA. Explain why this is not a problem for the operator in judging core covery/uncovery.
?
l
'i C
7.
In a submittal MN-83-83 the range of PT-3002 was given as zero to 64.5 ft.
How doef the reverse indication caused by pumps-on dynamic head provide use-ful irtfomation with this range? It is not clear that the response to NRC concern No. 7 in the March 8, 1985 submittal MN-85-47, considers the downscale overrange of PT3002.
8.
Provide the justification for the large uncertainty of the PITS level measurement on the basis of procedure action items and plant specific operator response or propose system modifications to improve the accuracy to an uncertainty of t6%. Also provide the schedule for completion of the modifications.
~'
9.
Clarify that there.are eighteen qualified CETs, of which eight CETs are used for the backup display and provide the justification why eight qualified CETs instead of sixteen CETs are used for the backup display since there are eighteen qualified CETs available. Please provide plans and the schedule for upgrading to meet requirements of NUREG-0737. Item II.F.2.
- 10. There is no indication in the submittal that the displays for the subcooling margin monitroing instrumentation are qualified accordilig to the requirements of II.F.2.
Please provide plans and schedule for installing qualified redundant trains of SMM.
l l
2 l
,' !.6 Mr. J. B. Randazza Maine Yankee Atomic Power Company Maine Yankee Atomic Power Station Charles E. Monty, President Mr. P. L. Anderson, Project Manager Maine Yankee Atomic Power Company Yankee Atomic Electric Company 83 Edison Drive 1671 Worchester Road Augusta, Maine 04336 Framingham, Massachusetts 07101 Mr. Charles B. Brinkman Mr. G. D. Whittier Manager - Washington Nuclear Licensing Section Head Operations Maine Yankee Atomic Power Company Combustion Engineering, Inc.
83 Edison Drive 7910 Woodmont Avenue Augusta, Maine 04336 Bethesda, Maryland 20814 John A. Ritsher, Esquire Ropes & Gray 225 Franklin Street-Boston, MassachUsetn 02110 State Planning Officer Executive Department 189 State Street Augusta, Maine 04330 Mr. John H. Garrity, Plant Manager Maine Yankee Atomic Power Company P. O. Box 408 Wiscasset, Maine 04578 Regional Administrator USNRC, Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 First Selectman of Wiscasset Municipal Building U.S. Route 1 Wiscasset. Maine 04578 Mr. Cornelius F. Holden Resident Inspector c/o U.S. Nuclear Regulatory Commission P. O. Box E Wiscasset, Maine 04578 r
_ - - _. _ _ _