HL-1298, Documents Acceptability of Util Current PASS Ventilation Design

Documents Acceptability of Util Current PASS Ventilation Design

ML20058A759
Person / Time
Site:	Hatch
Issue date:	10/18/1990
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.3, TASK-TM HL-1298, NUDOCS 9010290152
Download: ML20058A759 (5)

Text

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, Gearo a Pwir Company l

333 Piedrnont Avenue

', Atlanta. Georgia 30308 T& phone 404 520 3195 Ma4ng Mdress 40 Inverness Centor Park way Post Of6co nox 1295 Birrningtwn, Alat>ama 3S201 Telephone 205 868 5581 t% sout%rn vitene sustem

w. c: Hairston, Ill HL-1298 sen4or vee erosidera 001144 Nuclear Operaboos October 18, 1990 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.

20555 PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366 L

OPERATING LICENSES DPR-57, NPF-5 PASS ROOM VENTILATION Gentlemen:

At the request of the NRC staff, Georgia Power Company (GPC) hereby provides.this, letter documenting the acceptability of our current post i

accident sampling system (PASS) ventilation design.

This letter also serves to clarify information provided to the NRC on the PASS by letter dated January 26, 1984, in light of a very unlikely. scenario identified by GPC personnel.

This scenario is described briefly below and detailed in the Enclosure.-

The Unit 2 standby gas treatment system (SGTS) normally provides filtered ventilation for the PASS room (which serves both units at' Plant Hatch) as: indicated in the January 26, 1964 letter.

However, Hatch Unit 1 is i

operated during time periods when Unit 2 secondary containment is not established, such as -during a Unit 2 refueling outage.

In an extremely

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unlikely event where an accident occurred in Unit I without Unit 2' secondary containment. integrity and a_ leak or break also occurred in the PASS when the I

system was initiated.-for sampling, the release would only be filtered by the normal nonsafety-related reactor building 9entilation system.

This scenario was discussed with NRC personnel on August 2, 1990 and it wastagreed that-the existing PASS ventilation design is adequate and a design change. is not required due to the low-probability of the scenario occurring l

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and the fact the NUREG-0737, Item II.B.3 does not require safety-grade exhaust filtering. The staff requested that GPC update its 1984 submittal to reflect the existing design. The staff. also requested we consider actions to' further reducetthe probability of the scenario occurring and' decide if the.

LFSAR:'should be updated to reflect ' the as-built design.

The enclosure

discusses these items and the PASS ventilation design in detail.

Please contact this office if you have questions.

Sincerely, jn2XnsMAL g.j&TP -

4 PDC W. G. Hairston, III.

GKM/1d

Enclosure:

(See next page.)

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Geoigialbwer U.S. Nuclear Regulatory Commission October 18, 1990 Page Two

Enclosure:

' Post Accident Sampling System (PASS) Room Ventilation c:

Georaia Power Company Mr. H. L. Sumner, General Manager - Nuclear Plant Mr. J. D. Heidt, Manager Engineering and Licensing - Hatch GO-NORMS U.S. Nuclear Reaulatory Commission. Washinaton. D.C.

Mr. F. Rinaldi, Acting Licensing Project Manager - Hatch U.S. Nuclear Reaulatory Commission. Reaion A-Mr. S. D. Ebneter, Regional Administrator Mr. L. D. Wert, Senior Resident Inspector - Hatch (1. g 001144 4

i ENCLOSURE PLANT HATCH - UNITS 1, 2 NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 POST ACCIDENT SAMPLING SYSTEM (PASS) ROOM VENTILATION NUREG-0737, (Reference 1), reouires that "... ventilation exhaust from the sampling station should be filtered with charcoal adsorbers and HEPA i

filters."

As stated in Reference 2, the Hatch PASS room is located in the Hot Machine Shop adjacent to the Unit 2 Reactor Building and is provided with ventilation by the Standby Gas Treatment System (SGTS).

The SGTS contains both charcoal adsorbers and HEPA filters.

The NRC evaluation, Reference 3, concluded that PASS meets the requirements of NUREG-0737.

The PASS room is designed and constructed as an extension of the Unit 2 Reactor Building secondary containment.

A 16' pipe provides the ventilation flow path between the Reactor Building and the PASS room, thereby providing an extension of the Unit 2 secondary containment and a drawdown path for the Unit 2-SGTS.

No drawdown path to Unit 1 SGTS is provided.

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Hatch Unit 1 is operated during time periods when Unit 2 secondary containment is not established, such as during a Unit 2 refueling outage, in an extremely unlikely event where an accident occurred in Unit I without Unit 2 secondary containment integrity,.and a leak or break also occurred in the PASS when the system was initiated for sampling, the release would only be filtered by the normal reactor building ventilation system.

This system is non-safety related, but = has both charcoal and HEPA filters and generally keeps the reactor building at slightly negative pressure.

The normal reactor building violation filtering system and its ability to maintain -the reactor building at a negative pressure is not routinely tested as with--the safety-related SGTS.

The chance of an unfiltered ground level release through a sample line has been estimated at about 10-8 to 10-9 per year for the above scenario -far below ' commonly _ quoted-safety goals of about 10-6/yr.

Georgia ' Power

Company, therefore, believes the existing PASS room ventilation design is adequate.

Additionally, the Unit 2 SGTS/ secondary containment or the normal reactor building ventilation system do provide filtered PASS room exhaust.

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Discussions with NRC personnel have also indicated they agree with our-conclusions.

Per the staff's request, this letter serves to clarify our Reference. 2 submittal and -respond to three

' discussions.

questions raised during.the R

_ Question 1:

Can GPC assure the integrity of the PASS-sample lines?

Response

The_ PASS sample lines are not considered safety-related and l

are not included in our ASME Section XI inservice inspection (ISI) program.

Even if the lines were considered safety-001144 HL-1298 E-1

'e' ENCLOSURE (Continued)

PASS ROOM VENTILATION related, their small diameter would exclude them from Section XI surface and volumetric exams. The sample lines were constructed to ASME Class 1 and 2 requirements up to and including the outboard isolation valves and ANSI B31.1 outboard of the Class 2 piping, The B31.1 line which provides reactor coolant samples was designed for approximately 900 psi, which is much higher than that expected in the primary

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system following a core damage accident. Also, during routine PASS operation with the reactor at power, the reactor coolant sample line would see higher pressure than that expected several hours after an accident. The 831.1 line which provides containment atmosphere samples is designed for 125 psi or approximately twice the containralit design pressure.

This sample line is also periodically operated, although not at pressures higher than would be expected following an accident.

As indicated in our Reference 2 submittal, the design of the PASS limits potential leakage from the sample lines. The PASS room is located as close to the sample sources as possible while still maintaining the room-in an area of low background radiation.

Sample lines are constructed of the smallest practical tubing (3/8 inch diameter) to minimize the volume of fluid being removed from containment.

Potential reactor coolant loss-from-a ruptured sample line is limited by an excess flow check valve in the jet pump flow-sensing instrument line.- Both reactor coolant and drywell atmosphere sample lines are provided with redundant, environmentally qualified, remotely operated containment isolation valves which close on a containment isolation signal.- The excess flow check valves and containment isolation valves are tested for leakage every. refueling outage.

Question 2:

Is it possible to include direction somewhere to restore Unit 2 secondary containment to the extent practical prior to taking a post-accident sample?

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Response

GPC will modify its procedure governing post-accident sampling

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to require closing of major Unit 2 reactor building doors, hatches, etc. prior to taking'a sample. Note that this does not re-establish Unit 2. secondary containmant integrity; l

however, it would tend to increase the effectiveness of the SGTS and/or-normal ventilation for this extremely unlikely event.-

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ENCLOSURE (Continued)

PASS ROOM VENTILATION Question 3.

Does the FSAR need updating to reflect the as-built design 7

Response

Georgia Power Company has reviewed Unit 2 FSAR subsection 7.6.11, " Post-Accident Sampling System" and Unit I subsection 7.20 (which references the Unit 2 subsection). The FSAR does not discuss the PASS room ventilation ir sufficient detail to warrant a change to the FSAR text.

REFERENCES:

1.

NUREG-0737, ' Item II.B.3 Post Accident Sampling Capability, Clarification ll.b.

2.

GPC to NRC letter NED 84-038 dated January 26, 1984, "NUREG 07;? Item II.B.3, Post Accident Sampling Capability".

3.

NRC to GPC letter dated September 21, 1984, " Resolution of NUREG-0737, Item II.B.3... Hatch Units 1 and 2".

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i 001144 HL-1298 E-3