3F0888-21, Responds to NRC Bulletin 88-008 Re Thermal Stresses in Piping Connected to Rcs.Testing & Analysis Performed on Dual Function HPI Nozzle to Be More than Sufficient to Qualify HPI Only Nozzles for Any Minor Valve Leakage

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Responds to NRC Bulletin 88-008 Re Thermal Stresses in Piping Connected to Rcs.Testing & Analysis Performed on Dual Function HPI Nozzle to Be More than Sufficient to Qualify HPI Only Nozzles for Any Minor Valve Leakage
ML20153G508
Person / Time
Site: Crystal River Duke Energy icon.png
Issue date: 08/30/1988
From: Widell R
FLORIDA POWER CORP.
To:
NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
3F0888-21, 3F888-21, IEB-88-008, IEB-88-8, NUDOCS 8809080185
Download: ML20153G508 (3)


Text

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coneonatnow August 30, 1988 3F0888-21 U. S. Nuclear Regulatory Commission l Attention Document Control Desk i Washington, D. C. 20555

Subject:

Crystal River Unit 3 Docket No. 50-302 Operating Licensing No. DPR-72 Response To NRC Bulletin 88-08:

Thermal Stresses In Piping Connected To RCS Dear Sir Florida Power Corporation (FPC) is submitting the following info *1aation as its response to Bulletin 88-08 and its two supplements.

In January 1982, Crystal River Unit 3 (CR-3) had a failure in its normal makeup nozzle. The Emergency Core Cooling System (ECCS) piping failure at Farley 2, and the Make-Up/ High Pressure Injection (MU/HPI) line failure at Crystal River Unit 3 were both brought on by high cycle thermal fatigue. Similarity between the two failures would appear to end at this point, owing to the dissimilar nozzle arrangement. Farley's arrangement features an elbow while CR3 utilizes a straight run protected by a thermal sleeve. The solution l path taken by FPC and the B&W Owners Group parallels the action items I

outlined in Bulletin 88-08. FPC letter dated April 30, 1982 (3F0482-

34) docuacnts the failure mechanism and actions taken to repair the safe-end region components.

Following the failure of the MU/HPI nozzle safe end welds at CR-3, a natallurgical examinat. ion concluded that a degraded or inadequate contact expansion of the associated thermal sleeve was the principle, contributing factor in the safe-end weld thermal fatigue failure.

Flow induced vibration caused a loose thernal sleeve to rotate, allowing circulation of primary coolant between the thermal sleeve and nozzle body. The thermal sleeves on the other three nozzles were intact, undamaged and properly rolled. Nondestructive testing (radiography, dye penetrant, ultrasonic) of these nozzles did not reveal any flaws induced by thermal fatigue.

$ 0 30 NU ,

GENERAL OFFICE: 3201 TNrtpfourth Strut South

  • P.O. Sca 14042
  • St. Petersburg, Rorida 33733 * (813) 866 5151 A Florida Progress Company

y August 30, 1988 3F0888-21 Page 2 Once the failure mechanism was understood, the nozzle assemblies were

! modified. The thermal sleeve in the MU/HPI nozzle was replaced with a

~l slightly longer sleeve (+1.5"). The added length was necessary to facilitate installation. The check valve just upstream of each nozzle

! was relocated five inches further upstream, and all thermal sleeves

were rerolled to improve and expand nozzle contact. Following the i repair effort, a finite element analysis qualified the revised j configuration for service based on the original design code (USAS i B31.7, June 1968).

Actual operating data was collected on the MU/HPI nozzle assembly i' using thermocouples, strain gages, and accelerometers. Data was collected across the full spectrum of expected flow conditions, from full emergency flow down to a minimum of 1.5gpm. Throughout testing,

, the temperature profiles at each cross sectional plane did not

indicate the presence of hot spots or flow stratification. Static and 1 dynamic strains measured at the safe end to HPI piping interface were j well below allowable limits. Since the flow characteristics and

, temperature distribution downstream of the modified nozzle is acceptable at a flow rate of only 1.5gpa, FPC is confident that a lesser flow rate, such as that resulting from upstream valve leakage,

, will not compromise the integrity of the assembly.

The nozzles are now part of an augmented inservice inspection plan.

]'

Nondestructive testing (radiography) is used to confirm nozzle and thermal sleeve integrity during selected refueling outages. The radiography was last performed during Refuel V (1985).

1 i FPC considers the testing and analysis performed on the dual function 1 MU/HPI nozzle as part of our 1982 repair program to be more than

{ sufficient to qualify the HPI "only" nozzles for any minor valve j leakage. The redesign, testing, analysis and surveillance of the nozzles parallels the actions requested in Bulletin 88-08 This

, letter completes the action requested by Action Item 1 and Reporting Requirement 1.

Sincerely,

(

i Rolf C. Widell, Director Nuclear Operations Site Support RCW/JWT/cdc xc Regh .nistrator, Megion II S e r, .

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STATE OF FIDRIDA COUNTY OF PINELIAS Rolf C. Widell states that he is the Director, Nuclear Operations Site support for Florida Power Corporation; that he is authorized on the part of said company to sign and file with the Nuclear Regulatory Commission the information attached heretor and that all such statements made and matters set forth therein are true and correct to the best of his knowledge, information, and belief.

i Rolf C. Widell, Director Nuclear Operations Site Support Subscribed and sworn to before me, a Notary Public in and for the State and County above named, this 30th day of August, 1988.

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Notary,Public 1

Notary Public, State of Florida at Large, I l

tm r.nu not u num My Commission Expires: " emm, ne o tr,ng

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