ML20235Z792

Rev 3 to SAR for Pressurizer Defueling Sys

ML20235Z792
Person / Time
Site:	Three Mile Island
Issue date:	07/10/1987
From:	Digiacomo L, Gallagher R, Potts W GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20235Z778	List: ML20235Z776 ML20235Z792 ML20236A013 ML20266J638
References
4710-3255-86, 4710-3255-86-00, 4710-3255-86-0007-R3, 4710-3255-86-7-R3, NUDOCS 8707270405
Download: ML20235Z792 (12)

Text

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SAFETY ANALYSIS sa # 4710-3255-86-0007

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of 12 TITLE SAFETY ANALYSIS REPORT FOR THE i i

PRESSURIZER DEFUELING SYSTEM _

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SA '4710-3255-86-0007 Rev. 3 Page 2 of 12 SAFETY ANALYSIS REPORT FOR THE l PR' DSS'JRIZER DEFUELING SYSTEM PURPOSE /ND 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 TMI-2 accident on March 28, 1979, fuel and/or core debris have been located throughout the Nuclear Steam Supply System (hSSS),

which includes the pressurt7er. 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 1

of this first inver.tiga' ton indicated that 100 to 200 grams of uranium were deposited in the eastward section of the pressurizer surge line 09528 PC t

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SA 4710-3255-86-0007 Rev. 3

.. Page 3 of 12 (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 f deposited on the bottom of the pressurizer (Reference 2). The third

. ' investigation was performed using a video camera and by collecting samples. l j

Observations with the video camera concluded that a maximum of 12 liters of finely divided debris exists within the pressurizer. However, based on the i i

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 approximately 40 feet. Other. methods of defueling the pressurizer were considered but were determined to be uneconomical or inefficient.

I The Pressurizer Defueling System utilizes a portion of the DWC System to provide a flow path back to the reactor vessel. Inherent in the design of the DWC System,-is the capability to use filter canisters and/or knockout -

canitters as part'of'the process stream to filter and' remove fuel debris.

Although this debris separation capability exists, and may be used if l defueling conditions warrant, pr_esent baseline plans are to bypass the filter canisters and return the process stream directly to the reactor vessel, i 09528.PC i

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SA 4710-3255-86-0007 Rev. 3

, Page 4 .of 12-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 those_ particles exceeding.800 microns'will be retained (Reference 8). The

water II then directed ~to either the DWCS filters.or directly to the reactor vessel 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, which increases the efficiency of the vacuuming process. Appropriate valving and instrumentation will be used to monitor and control the flow. Attachment 1 serves as the basis for this system description.

SYSTEM COMPONENTS -

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• 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 4 09528 PC  ;

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SA 4710-3255-86-0007- Rev. 3

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-sealed and runs in air. The pump has an_ int lgral cooling system that allows the unit to pump continuously with the motor above-11guld level.

The impeller is constructed or abrasion-resistant steel.

• AGITATION N0ZZLES  !

These nozzles are two-oiece 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 i 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'106 rads, and is also capable of handling suspended solids. The hose is color coded to l avoid disconnection or confusion with other hoses.

SUPPORTING ACCESSORIES l

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.

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SA 4710-3255-86-0007 Rev. 3 Page 6 of 12 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. i i

1 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.

BORON DILUTION During operation of the Pressurizer Defueling System, water from the reactor vessel will mix with water contained in the pressurinr via the DWC system and 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 j 1

loop system, no other water sources are introduced as possible boron dilution i

paths.

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l RADIOLOGICAL CONTR01.5 t l

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No direct radioactive release paths to the environment exist for this system.

Any spillage of contaminated water from the Pressurizer Defueling System will result in a local contamination problem. To preclude any significant 0952B PC

SA 4710-3255-86-0007 Rev. 3 Page 7 of _12 radioactive releases during pressurizer defueling, the operating procedures l

associated with processing reactor vessel water shall include requirements to 1

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. These estimates are based upon current man-hour projections:

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l LOCATION ACTIVITY MAN-HOURS (mR/Hr) Y MAN-REM R.B. Floor at Installation 49 50 mrem 2.45 Elev. 348'-3" Operation 9 .45 Removal 4 .2 "A" D-Ring at Installation 10 50 mrem .5 Elev. 367'-4" Operation 0 0 Removal 1 .05 Pressurizer Installation 22 50 mrem 1.1 l Missile Shield Operation 133 6.65 l 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 TOTAL 62.6 The total man-rem attributable to the installation, operation, and removal of the Pressurizer Defueling System, as a whole, is expected to be approximately 62.6 man-rem. The estimate includes coverage by Health Physics.  ;

This man-rem estitaate is considered the maximum dose for this job for the following reasons:

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SA 4710-3255-86-0007 Rev. 3 Page 8 of 12 1.) For this man-rem es'timate it:is-conservatively assumed that during system checkout and operation a worker is continuously positioned at the pressurizer manway. The Pr_essurizer Defueling System is controlled from a- station on the pressurizer missile shield, but manipulation of the agitation nozzle is performed from the manway

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location. It is considered likely.that the agitation nozzle will not need to be continuously manned and that only a fraction of the estimated time for operations at the manway will be expected.

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2.) The dose rate at the manway location is conservatively estimated to be 1 rem /hr. Worker position as well as portable shielding will be

-used when practical to reduce the operator's. dose rate. j Personnel protection for airborne and other potential contamination generated 3 by the installation, use, and/or removal of the Pressurizer Defueling System-vill 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.

l.INE BREAK l

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 l l

i 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 0952B PC ,

SA 4710-3255-86-0007 Rev. 3 ,

Page 9 of 12 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.

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. Thh check valve will prevent water from flowing out of the pressurizer should a nose break occur inside the pressurizer. A hose break in the submersible pump discharge line is of no concern with respect to siphoning, since all unsubmerged piping and hose outside of the pressurizer is at or above the Reactor Vessel water level, i

I 10CFR50.59 EVALUATION i

i The Pressurizer Defueling System does not increase the probability of  !

j 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, l

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 6.8.1.

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I SA 4710-3255-86-0007 Rev. 3 )

Page 10 of 12 I The Pressurizer Defueling System is essentially a liquid radwaste system utilized to transport radioactive. material from the pressurizer into a I l

knockout canister and into DHCS filter canisters or the reactor vessel. As ld l such, the possibility of an accident or malfunction is of the serie type as

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i 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).

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 i 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. 3 Page 11_ of 12 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."

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2. THI-2 Technical Planning Bulletin TPB-8.%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 /

Radiological Inspection and Sampling of the Pressurizer."  !

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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.10, "TMI-2 Division Technical ld )

Evaluation Report for Defueling Water Cleanup System."

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6. Code of Federal Regulations Title 10 (Energy) Part 50 Paragraph 50.59,

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Revised as of January 1, 1985.

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

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TER 3527-016-15737-2-G03-il4 Rev. 3, "TMI-2 Division Technical Evauation lg Report for Defueling Canisters."

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SA 4710-3255-86-0007 Rev. 3 Page 12 of 12 AJTACHMENT I l

1. DC 3255-86-0004 Rev. 1, "TMI-2 Design Criteria for Pressurizer Defueling ld I i

System." l l

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