ML20238C623

Rev 4 to SAR for Pressurizer Defueling Sys

ML20238C623
Person / Time
Site:	Three Mile Island
Issue date:	08/21/1987
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20238C619	List: ML20238C618 ML20238C623 ML20238C639
References
4710-3255-86, 4710-3255-86-00, 4710-3255-86-0007-R4, 4710-3255-86-7-R4, NUDOCS 8709100256
Download: ML20238C623 (12)

Text

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FulNu2Ioar SAFETY ANALYSIS sA # 4710-3255-86-0007 Rev. a 4 Page 1 of 12 TITLE SAFETY ANALYSIS REPORT FOR THE PRESSURIZER DEFUELING SYSTEM l

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,- ,. SA 4710-3255-86-0007 Rev. _4_

4 Page 1 of 12 SAFETY ANALYSIS REPORT _

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PRESSURIZER DEFUELING SYSTEM J

PURPOSE AND SCOPE 1

The purpose of.this safety analysis is to demonstrate that the addition of the )

j Pressurizer Defueling System, for removing fuel debris, will not result in any

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harmful effects to the reactor coolant system inventory or undue risk to the health and safety of the public. _

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

.i Cleanup-System (DHCS).

BACKGROUND Due to the effects of the TMI-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 sect.on of the pressurizer serge line 0952B PC

SA 4710-3255-86-0007 Rev. 4 Page 3 of 12 (Reference 1). A second investigation was performed using a sodium lodide 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 deteonined 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 approximately 40 feet. Other methods of defueling the pressurizer were considered but were determined to be uneconomical or inefficient.

The Pressurizer Defueling System utillzes a portion of the DHC System to provide a flow path back to the reactor vessel. Inherent in the design of the DHC System, is the capability to use filter canisters and/or knockout canisters as part of the process stream to filter and remove fuel debris.

Although this debris separation capability exists, and may be used if 09528 PC

SA 4710-3255-86-0007 Rev. 4 Page 4 of 12 defueling conditions warrant, present baseline plans are to bypass the DHCS filter canisters and route the process stream through a knock-out canister and a DHCS type filter canister in series (both the knockout and filter canisters are independent of DHCS). The process stream is then directed to the reactor i vessel via one of the DWCS return lines. 4 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 l 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 those particles exceeding 800 microns will be retained (Reference 8). The water is then directed to a DHCS type filter canister (in series with the knockout canister with both being independent of DHCS) and back to the reactor vessel via one of the DHCS return lines. 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, which increases the efficiency of the vacuJming process. Appropriate valving and instrumentation will be used to monitor and control the flow. Attachment I serves as the basis for this system description.

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." SA.4710-3255-86-0007 Rev. 4 Page 1 of 12 SYSTEM COMPONENTS

• - PUMP '!

The pump is a submersible centrifugal type, capable of handling solids up to 1/4" in size. The junction chamber (where ti t 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 motsture 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 ,

i 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.

• AGITATION N0ZZLES These nozzles are two-piece cast type with an internal 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 09528 PC

SA 4710-325S-86-0007 Rev. 1 Page 6 of 12 operating pressure is 140 psig. .The hose is supplied in 100 foot '

lengths, whl.ch.will minimize the number of connections. The hose is capable of operating in a radiation environment of 1.8 x 106 rads, and is also capable of handling suspended solids. The hose is color coded to avoid disconnection or confusion with other hoses.

. *- SUPPORTING ACCESSORIES Piping, pipe fittings, pipe flanges, and valves are stainless steel.

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

• DEFUELING WATER CLEANUP SYSTEM (DHCS)

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

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BORON DILUTION I l

i 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 1 l:

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SA.4710-3255-86-0007 Rby, 4 Pade T of 12 agitation supply 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 scurces are introduced as possible bcron dilution paths.

• RADIOLOGICAL CONTROLS No direct radioactive release paths to the environment e ist for this system.

Any spillage of contaminated water from the Pressurizer Defueling System will 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 ensure' isolation of the system should a line break occur.

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. Theseestimatesarebased'dponcurrentman-hourprojections:

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LOCATION- ~ ACTIVITY MAN-HOURS' (mR/Hr) Y MAN-REM l

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R.B. Floor at Installation ~49 50 mrem 2.45

" Elevs 348'-3" Operation 9 .45 g _ ,

Removal 4 .2 V- "A"'D-Ring at Installation. 10 50 mrem .5 Elev. 367'-4"- Operation 0 0 y Removal 1 .05 , i M Pressurizer Installation 22 50 mrem 1.1 Missile Shield. Operation 133 6.65 at Elev. 370'-4" Removal 4 .2 Pressurizer Installation 15 1000 mrem 15.0' Platform at . Operation 35 35.0 Elev. 349'-9" Removal 1 1.0 7

TOTAL _ 62.6

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The total man-rem attributable to the installation, operation, and removal of s,

the Presw izer Defueling System, as a whole, is expected to be approximately 62.6 man-rom. The estimate includes coverage by Health Physics.

This man-rem estimate is considered the maximum dose for this job for the followipg reasons: '

l.) For this man-rem estimate it is conservatively assumed that during system checkout and operation a worker is continuously positioned at the pressurizer tranway. The Pressurizer Defueling System is controlled from a station on the pressurizer missile shield, but l

l- manipulation of the agitation nozzle is performed from the manway l

location. It is considered likely that the agitation nozzle will ti 4

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. ..> SA 4710-3255-86-0007 Rev. 4 Page 9 of 12 not need to be continuously manned and that only a fraction of the estimated time for operations at the manway will be expected.

2.) The dose rate at the manway location is conservatively estimated to be I rem /hr. Worker position as well as portable shielding will be used when practical te reduce the operator's dose rate..

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.

The routing of hoses and the location of valves for the Pressurizer Defueling System will be such that dose rates to personnel performing tasks unrelated to pressurizer defueling will be minimized.

LINE BREAK Hose and piping will be hydrostatically pressure tested prior to use :o 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 local control panel. The pump will trip on IIF low level because it will be electrically interlocked with the IIF water level monitoring instrumentation (Reference 5). This event could deliver approximately 500 to 1000 gallons of reactor vessel water to the area of the break.

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v SA 4710-3255-86-0007 Rev. 4 i Page 10 of .,12, I Siphoning of reactor vesset water from the pressurizer thrcugh the a.gitation

,; supply line is prevented by tne placerunt of a check valve in close proximity i \p . -

l to the pressurizer. This check valve will provent water from flowing out of g,

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' the pressurizer should a hose break occur inside the prer.surizer. A hose {

break in the submersible pump discharge line is of no conct.rn with resacet to 1

$ siphoning, since all unsubmerged piping end hose outside of the pressurizer is j J

at or above the Reactor Vessel water Irev el. j

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, "i . 10CFRSO.59 EVALUATION '

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s 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 ana(ysis report. The system failures such as boron dilution, radiological b. pact, 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 op9 ration. The procedures used for operation of the Pressurizer Defioling System will be reviewed and approved prior to use in accordance_with Reference 7, Section 6.8.1.

.1 4 The Pressurizer Defueling System is essentially a?l! quid radwaste syst6m utilized to.. transport. radioactive matertal from the pressurizer into a

. knockout canister and into a DHCS type filter canister, with effluent returned to the reactor vessel. As such,/the poystbility of an accident or malfunction

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is of the same type as previously evalJated for other 11guld radwaste systems. l

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,- SA 4710-3255-86-0007 Rev. 4 Page- 11 of 12 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 te the environment directly from , 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).

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.

REFERENCES l

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."

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

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. . .,- SA 4710-3255-86-0007 Rev. 4

• o' Page 12 of 12 L 3. THI-2 Technical Bulletin TB-86-02 Rev. O, Dated 01'/13/86, " Physical /

Radiological Inspection and Sampling of the Pressurizer."

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4. TMI-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. 10. "THI-2 Division Technical Evaluation Report for Defueling Water Cleanup System."

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

7. Three Mlle Island Nuclear Station Unit 2 Operating License Number DPR-73 with the Recovery Technical Specification.

8. TER 3527-016-15737-2-G03-II4 Rev. 3, "THI-2 Division Technical Evauation Report for Defueling Canisters."

ATTACHMENT

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

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