ML20205J288

Forwards Primary Inventory Trend Sys Design/Operational Analysis, Per NUREG-0737,Item II.F.2.Rept Provides Analysis Necessary to Demonstrate Adequacy of Sys

ML20205J288
Person / Time
Site:	Maine Yankee
Issue date:	01/27/1986
From:	Whittier G Maine Yankee
To:	Thadani A Office of Nuclear Reactor Regulation
Shared Package
ML20205J290	List: ML20205J288 ML20205J300
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.2, TASK-TM 6768L-FWS, GDW-86-11, MN-86-04, MN-86-4, TAC-45145, NUDOCS 8601300147
Download: ML20205J288 (2)

Text

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MAIRE HARHEE ATOMICPOWERCOMPARUe ,uaug,ay,TeQl, (207) 623-3521 e

January 27, 1986 MN-86-04 GDW-86-ll Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of Licensing

References:

(a) License No. OPR-36 (Docket No. 50-309)

(b) MYAPCO Letter to USPC dated April 29, 1983 - Inadequate Core Cooling Instrumentation System (Generic Letter No.

82-28) (MN-83-83)

(c) USNRC Letter to MYAPCo dated November 14, 1984 - Inadequate Core Cooling Instrumentation (ICCI) System (d) MYAPCo Letter to USmC dated March 8,1985 - Inadequate Core Cooling Instrumentation (ICCI) System (m-85-47)

(e) USNRC Letter to MYAPCo dated June 26, 1985 - Inadequate Core Cooling Instrumentation System for Maine Yankee Atomic Power Station

( f) MYAPCo Letter to USmC dated August 7,1985 - Schedule for Submitting Additional Information on Inadequate Core Cooling (MN-85-145)

(g) MYAPCo Letter to USmC dated September 6,1985 - Answers to Questions Concerning Inadequate Core Cooling Instrumentation (MN-85-159)

Subject:

Plant Specific Analysis of Maine Yankee Primary Inventory Trend System o-685- Gentlemen:

38' oo Enclosed is Maine Yankee's analysis of our Primary Inventory Trend System fo (PITS) submitted in accordance with the requirements of NUREG-0737, Item II.F.2. Briefly the report provides the design / operational analysis g

eu necessary to demonstrate the adequacy of the Maine Yankee PITS. The results oO of this analysis indicate that the PITS readings are representative of the actual coolant liquid inventory in the primary system, o5 The Primary Inventory Trend System consists of three differential pressure

"' (dp) transmitters connected across three locations within the Reactor Coolant System (RCS). The dp measurements can be used to assess trends in the mass inventory within the primary system during a small break accident such as experienced at TMI, Unit 2. The mass inventory trend system, the saturation i

[ 3 monitor, and ente exit thermocouples, provide the operator information i d concerning the progress of an accident and recovery. 3 (

6768L-FWS. 400'. D

M AINE Y ANKEE ATOMIC POWER COMPANY United States Nuclear Regulatory Commission Page Two Attention: Mr. Ashok Thadani, Director MN-86-04 The objective of this analysis was to demonstrate that.each of the PITS transmitters will adequately trend the change' of mass inventory within their respective regions of the primary system. This was done for two different break scenarios: . A cold leg break and a stuck open PORV. These scenarios were chosen so~that the PITS response could be assessed against breaks which are characteristically different. The response of the PITS ' transmitters was predicted by calculating a time history of varying pressure differences across each of the transmitters for the two scenarios. The output of each transmitter was converted to an inferred mass inventory within the region of measurement. The validity of the PITS response was assessed by comparing the trend of the inferred mass inventory against the trend of calculated inventory of the primary system.

t For a small break TMI-type scenario, this analysis showed that with the Reactor Coolant Pumps (RCPs) off, each PITS transmitter provides a representative trend in mass inventory within its region of measurement.

Fractional pressure drops which occur during the small break transients have negligible effect on the dp measurements.

Corrections for system errors caused by ra'diation, density variations, voiding in sensing lines due to flashing of dissolved gases were not factored into the analytical output. These uncertainties however, are accounted for by use of a caution band on the PITS Control Room display. The caution band provides a conservative means of warning the operator of an approach to possible core uncovery. The trend information and other primary instrumentation assist the operator in assessing the status of core cooling and accident recovery.

Chart paper with the caution band shaded has been ordered and will be installed as soon as it is on site. Similarly, graduated scales for the three channels with scale markings only in the active range of each channel are being made up and will soon be installed. The PITS will be fully operational when the operators have completed training on our new emergency operating procedures.

The only open items remaining on ICCI are our previously noted commitments, Reference (g), to change the power supply to one of the 4 transmitters and provide PITS input to the SPDS. Both of these changes will be made during the Cycle 9/10 refueling outage.

If you have any questions, do not hesitate to call.

Very truly yours, MAItE YAtKEE ATOMIC POWER COM'ANY -

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&LW S4/A G. D. Whittier, Manager Nuclear Engineering & Licensing GDW/bjp cc: Dr. Thomas E. Murley Mr. Cornelius F. Holden 6768L-FWS