ML20211Q975

Rev 1 to SAR for Pressurizer Defueling Sys

ML20211Q975
Person / Time
Site:	Three Mile Island
Issue date:	11/21/1986
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20211Q973	List: ML20211Q967 ML20211Q975 ML20211Q994 ML20265B453
References
4710-3255-86, 4710-3255-86-00, 4710-3255-86-0007-R1, 4710-3255-86-7-R1, NUDOCS 8612220208
Download: ML20211Q975 (11)

Text

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SA 4710-3255-86-0007 Rev. 1 Page 2 of 11 SAFETY ANALYSIS REPORT FOR THE PRESSURIZER DEFUELING SYSTEM PURPOSE AND SCOPE The purpose of this safety analysis is to demonstrate that the addition of the Pressurizer Defueling System, for removing fuel debris, will not result in any harmful effects to the reactor coolant system inventory or undue risk to the health and safety of the public.

The scope of this safety analysis includes only those new components such as the submersible pump, flexible hose, nozzles, instrumentation, piping, and valves. It does not include existing components such as the Defueling Water Cleanup System (DHCS).

BACKGROUND Due to the effects of the THI-2 accident on March 28, 1979, fuel and/or core debris have been located throughout the Nuclear Steam Supply System (NSSS),

which includes the pressurizer. Several investigations were performed to determine the quantity of fuel debris in the pressurizer. The first investigation was performed using spectrometry measurements taken under the lower head of the pressurizer adjacent to the surge line elbow. The results of this first investigation indicated that 100 to 200 grams of uranium were deposited in the eastward section of the pressurizer surge line 09528 PC

SA 4710-3255-86-0007 Rev. 1 Page 3 of 11 (Reference 1). A second investigation was performed using a sodium iodide scintillation spectrometer assembled under the pressurizer to detect fuel related photon events. The results indicated that 11 to 25 KG of uranium were deposited on the bottom of the pressurizer (Reference 2). The third investigation was performed using a video camera and by collecting samples.

Observations with the video camera concluded that a maximum of 12 liters of finely divided debris exists within the pressurizer. However, based on the sample of sediments taken from the inside of the pressurizer, the total fuel quantity was determined to be 910 grams (Reference 3). Reference 4 suggests that additional samples be taken to resolve the differences between estimates obtained from video observations and sample analysis.

SYSTEM DESCRIPTION The recommended method of defueling the pressurizer is to vacuum the debris out of the pressurizer using a submersible pump. This method is preferred over a method using an external pump because of the long suction height of l1 approximately 40 feet. Other methods of defueling the pressurizer were considered but were determined to be uneconomical or inefficient.

The Pressurizer Defueling System will remove fuel debris from the pressurizer by pumping water out of the pressurizer. This water is expected to contain mostly fuel fines with maximum particle size of 1/4" (this is limited by the pump). In order to ensure an adequate transport velocity for this debris, a flow rate of 100 GPM will be delivered by the pump into a discharge hose of 2 inch diameter. The flow will be directed to a knock-out canister where l j, 09528 PC

SA 4710-3255-86-0007 Rev. 1 Page 4 of 11 those particles exceeding 800 microns will be retained (Reference 8). The 1 water is then directed to the DHCS filters where the remaining fuel fines are collected. The water is then routed from DHCS back into the pressurizer via an agitation supply line. This line is equipped with a nozzle which promotes agitation of the water inside the pressurizer, thus suspending fuel fines, l

which increases the efficiency of the vacuuming process. Appropriate valving and instrumentation will be used to monitor and control the flow.

Attachment I serves as the basis for this system description. 1

SYSTEM COMPONENTS f

e PUMP The pump is a submersible centrifugal type, capable of handling solids up to 1/4" in size. The junction chamber (where the electric cable

. Interfaces with the terminal connections) has separate water sealing and strain relief functions. This junction chamber is sealed off from the motor, preventing burn out should moisture enter the junction chamber.

Terminal board connections can be changed to suit service voltage requirements. The motor windings are rated at 310*F and the motor is r

sealed and runs in air. The pump has an integral cooling system that allows the unit to pump continuously with the motor above liquid level.

The impeller is constructed of abrasion-resistant steel.

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SA 4710-3255-86-0007 Rev. 1 Page 5 of 11

• AGITATION N0ZZLES These nozzles are two-piece cast type with an interaal removable vane and are made of 300 series stainless steel.

• HOSE This is a rubber hose of braided construction. The working pressure of the hose is 300 psi, which is well above the maximum working pressure the submersible pump can deliver (approximately 195 psi). Normal system operating pressure is 140 psig. The hose is supplied in 100 foot lengths, which will minimize the number of connections. The hose is capable of operating in a radiation environment of 1.8 x 100 rads, and is also capable of handling suspended solids. The hose is color coded to avoid misconnection or confusion with other hoses.

• SUPPORTING ACCESSORIES l

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Piping, pipe fittings, pipe flanges, and valves are stainless stee' l These components are also rated for the maximum system pressure and conform to the American National Standards Institute (ANSI) code.

Instrumentation such as flow and pressure indicators will not be restricted due to suspended particles. Existing long handled tools will l

l be used as required and are not covered by this report.

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SA 4710-3255-86-0007 Rev. 1 Page 6 of 11

• DEFUELING WATER CLEANUP SYSTEM (DWCS)

This is an existing system witn its own safety analysis. The tie-in locations into DHCS will be addressed by the appropriate engineering change authorization.

BORON DILUTION During operation of the Pressurizer Defueling System, water from the reactor vessel will mix with water contained in the pressurizer via the DWC system and I

agitation sapply line. This will result in a more uniform boron concentration between the two vessels. Reference 7, Section 3.1.1.2 gives limiting conditions for boron concentration, that the Pressurizer Defueling System will not violate. In addition, since the Pressurizer Defueling System is a closed loop system, no other water sources are introduced as possible boron dilution paths.

RADIOLOGICAL CONTROLS No direct radioactive release paths to the environment exist for this system. l1 l

Any spillage of contaminated water from the Pressurizer Defueling System will l1

! result in a local contamination problem. To preclude any significant radioactive releases during pressurizer defueling, the operating procedures associated with processing reactor vessel water shall include requirements to l

ensure isolation of the system should a line break occur.

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SA 4710-3255-86-0007 Rev. 1 Page 7 of 11 The following table provides an estimate of the man-hours and man-rem associated with the installation, operation and removal of the Pressurizer Defueling System. These estimates are based upon current man-hour projections:

LOCATION ACTIVITY MAN-HOURS (mR/Hr) y MAN-REM R.B. Floor at Installation 6 100 mrem .6 Elev. 348'-3" Operation 1 .1

.6 Removal 6 "A" D-Ring at Installation 1 80 mrem .08 Elev. 367'-4" Operation 0 0 Removal 1 .08 Pressurizer Installation 2 50 mrem .1 Hissle Shield at Operation 5 .25 '

Elev. 370'-4" Removal 2 .1 Pressurizer Installation 5 600 mrem 3.0 Platform at Operation 5 3.0 Elev. 355'-3" Removal 5 3.0 TOTAL 10.91 There is a 12 Rem source present in the proximity of the grating platform at elevation 349'-9" south of the Pressurizer Vessel. This source must be adequately shielded prior to commencing the defueling activities.

The total man-rem attributable to the installation, operation, and removal of the Pressurizer Defueling System, as a whole, is expected to be between 10 and 17.2 man-rem. The estimate is based upon a total estimate of 11 man-rem increased by 20% for RadCon [

coverage and allowing i 30% due to uncertainties.

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SA 4710-3255-36-0007 Rev. 1 Page _8_ of 'll Personnel protection for airborne and other potential contamination generated by the installation, use, and/or removal of the Pressurizer Defueling System will be addressed in the appropriate plant procedures.

LINE BREAK Hose and piping will be hydrostatically pressure tested prior to use to ensure against any potential line break or failure. In the unlikely event of a hose rupture or line rupture upstream or downstream of the submersible pump the system will trip the pump on IIF low level and alarm at the control panel located on the pressurizer missile shield. The pump will trip on IIF low level because it will be electrically irterlocked with the reactor vessel cleanup pump which would trip on IIF low level (Reference 5). This event could deliver approximately 500 to 1000 gallons of reactor vessel water to the 1 area of the break.

Siphoning of reactor vessel water from the pressurizer through the agitation supply line is prevented by the placement of a check valve in close proximity to the pressurizer. This check valve will prevent water from flowing out of the pressurizer should a hose brea occur inside the pressurizer. A hose break in the submersible pump discharge line is of no concern with respect to 1

siphoning, since all unsubmerged piping and hose outside of the pressurizer is at or above the Reactor Vessel water level 0952B PC

-. . )

SA 4710-3255-86-0007 Rev. 1 Page 9 of 11 10CFR50.59 EVALUATION The Pressurizer Defueling System does not increase the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated in a safety analysis report. The system failures such as boron dilution, radiological impact, and line break have been addressed in previous sections of this document. In addition, operation of the Pressurizer Defueling System will be performed under strict administrative procedural control to further ensure safe operation. The procedures used for operation of the Pressurizer Defueling System will be reviewed and approved prior to use in accordance with Reference 7, Section ( j, 6.8.1.

The Pressurizer Defueling System is essentially a 11guld radwaste system utilized to transport radioactive material from the pressurizer into a knockout and OHCS filter canisters. As such, the possibility of an accident or malfunction is of the same type as previously evaluated for other liquid radwaste systems.

Operation of the Pressurizer Defueling System does not result in a reduction in the margin of safety as defined in the bases for the technical specifications. Liquid effluents will not be released to the environment directly from the Pressurizer Defueling System operation.

Based on the above, the installation and operation of the Pressurizer Defueling System does not present an unreviewed safety question as defined in 10CFR50.59 (Reference 6). l1 0952B PC

SA 4710-3255-Of-0007 Rev. 1 Page 10 of 11 CONCLUSION Based on the foregoing discussion, it can be concluded that the addition of the Pressurizer Defueling System will not violate reactor coolant system technical specifications, or affect boron concentration. Additionally, it does not adversely affect the Defueling Water Cleanup System or increase the consequences of a hose or line break. Therefore, utilizing the Pressurizer Defueling System presents no undue risk to the health and safety of the public.

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SA 4710-3255-86-0007 Rev. 1 Page 11 of ,_1_1_

REFERENCES

1. THI-2 Technical Planning Bulletin TPB-85-9 Rev. O, Dated 03/27/85, "An Estimate of Fuel Debris in the Pressurizer Surge Line."

2. TMI-2 Technical Planning Bulletin TPB-85-10a Rev. O, Dated 03/28/85, "An Estimate of Fuel in the Pressurizer Bottom."

3. THI-2 Technical Bulletin TB-86-02 Rev. O, Dated 01/13/86, " Physical / j Radiological Inspection and Sampling of the Pressurizer."

4. THI-2 Technical Bulletin TB-86-13 Rev. O, Dated 02/27/86, " Gamma Analysis of Pressurizer Sample."

5. TER 3525-015-15737-2-G03-106 Rev. 9, "THI-2 Division Technical Evaluation l1.

Report for Defueling Water Cleanup System."

6. Code of Federal Regulations Title 10 (Energy) Part 50 Paragraph 50.59, i Revised as of January 1, 1985.

7. Three Miie ?.siand Nuclear Station Unit 2 Operating License Nunber DPR-73 l 1.

with the Reconry Technical Specification.

8. TER 3527-016-15737-2-G03-114 Rev. 1, "THI-2 Division Technical Evauation y Report for Defueling Canisters."

ATTACHMENT

1. DC 3255-86-0004 Rev. O, "THI-2 Design Criteria for Pressurizer Defueling System."

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