ML12058A069

Response to Requests for Additional Information Associated with Adoption of the Alternative Source Term (AST) Methodology

ML12058A069
Person / Time
Site:	Prairie Island
Issue date:	02/24/2012
From:	Schimmel M A Xcel Energy, Northern States Power Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-12-013
Download: ML12058A069 (25)

Text

@ Xcel EnergyB FEB 2 4 2012 L-PI-12-013 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 Response to Requests for Additional Information (RAI) Associated with Adoption of the Alternative Source Term (AST) Methodolonv (TAC Nos. ME2609 and ME2610) In a letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27, 2009 (Agencywide Documents and Management System (ADAMS)

Accession No. ML093160583), the Northern States Power Company, a Minnesota corporation doing business as Xcel Energy (hereafter "NSPM"), requested an amendment to the Technical Specifications (TS) for Prairie Island Nuclear Generating Plant (PINGP).

The proposed amendment requested adoption of the Alternative Source Term (AST) methodology, in addition to TS changes supported by AST design basis accident radiological consequence analyses. Recently, the NRC staff conducted several conference calls with NSPM staff to discuss the technical details of NSPMJs main steam line break atmospheric dispersion model, which was submitted in the subject AST application.

To complete their review, the NRC staff requested additional information by electronic mail dated November 2, 201 1 (ADAMS Accession No. MLI 131 10094). Enclosure 1 to this letter provides the NSPM response to questions 2 and 4 of the November 2, 201 1 request for additional information. Enclosure 2 provides a proposed markup to the TS and Enclosure 3 provides a description and justification of the TS changes. Enclosure 4 provides a proposed markup of the TS Bases for your information. Final TS Bases changes will be implemented pursuant to TS 5.5.12, "Technical Specifications (TS) Bases Control Program," at the time the amendment is implemented. Enclosure 5 provides a draft markup of the Updated Safety Analysis Report (USAR) for your information.

NSPM submits this supplement in accordance with the provisions of 10 CFR 50.90. The supplemental information provided in this letter does not impact the conclusions of the Determination of No Significant Hazards Consideration and Environmental Assessment presented in the October 27, 2009 submittal, supplemented by letters dated April 29,201 0 (ADAMS Accession No.

ML101200083), May 25,201 0 (ADAMS 171 7 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone:

651.388.1 121 Document Control Desk Page 2 Accession No. ML101460064), June 23,2010 (ADAMS Accession No. ML101760017), August 12,201 0 (ADAMS Accession No. ML102300295), December 17,201 0 (ADAMS Accession No. ML103510322), June 22, 201 1 (ADAMS Accession No. MLI 11740145), July 11,201 1 (ADAMS Accession No. MLI 119301 57), August 9,201 1 (ADAMS Accession No. MLI 12220098), December 8, 201 1 (ADAMS Accession No.

ML113430091), and February 13,2012. In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this License Amendment Request (LAR) supplement by transmitting a copy of this letter to the designated State Official. If there are any questions or if additional information is needed, please contact Glenn Adams at (612) 330-6777.

Summaw of Commitments This letter contains two new commitments:

Commitment

1. Implement a plant modification that will either block the 121 Laundry Fan exhaust flow path permanently or will otherwise remove the 121 Laundry Fan exhaust path as a potential source of post-accident radioactive release through the Auxiliary Building Ventilation Due Date Within 90 days after completion of the outage in which the Unit 2 Replacement Steam Generators are installed.

Exhaust stack. 2. Implement an administrative control to require I declare under penalty of perjury that the foregoing is true and correct. Within 90 days after ~uxiliar~ Building Special Ventilation Zone boundary integrity during movement of heavy loads over an open reactor vessel containing irradiated fuel assemblies when the containment atmosphere is open to the outside (as described in USAR 12.2.12).

Mark A. Schimmel Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota completion of the outage in which the Unit 2 Replacement Steam Generators are installed.

Enclosures (5) cc: Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota Alternative Source Term - Response to RAls NSPM ENCLOSURE 1 In a letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27, 2009 (Agencywide Documents and Management System (ADAMS) Accession No.

ML093160583), the Northern States Power Company, a Minnesota corporation doing business as Xcel Energy (hereafter "NSPM"), requested an amendment to the Technical Specifications (TS) for Prairie Island Nuclear Generating Plant (PINGP). The proposed amendment requested adoption of the Alternative Source Term (AST) methodology, in addition to TS changes supported by AST design basis accident radiological consequence analyses. Recently, the NRC staff conducted several conference calls with NSPM staff to discuss the technical details of NSPM1s main steam line break atmospheric dispersion model, which was submitted in the subject AST application.

To complete their review, the NRC staff provided a request for additional information (RAI) by electronic mail dated November 2,201 1 (ADAMS Accession No.

MLI 131 10094). For clarity, the NRC RAI information is provided below in italics font and the NSPM response is provided in plain font.

Background:

Following a conference call with the NRC staff on September 22, 201 1, the licensee provided the following information concerning the design criteria for the Common Area of the Auxiliary Building (CAA B): Updated Safety Analysis Report (USAR), Table 12.2-1, Page 1 indicates that the Common Area of fhe Auxiliary Building is a Design Class Ill* structure (i.e., above the concrete part of the structure). The CAAB is referred to as Xuxiliary Building (Except Class I or I*)" in the Table. This is a Design Class Ill* structure. USAR Table 12.2-4 indicates that Class Ill* structures are designed for Dead

+ Live + Wind or Snow normal operating loads and Dead + Live + Uniform Building Code Zone I (earthquake) Loads.

USAR Section 12.2.1.3.1 defines snow loading as 50 Ibs per sq-ft and the design wind speed as 100 mph.

USAR Section 12.2.1.4.

Id describes the load combinations for Class Ill* structures. These structures are designed for the greater of the above load combinations, where the Uniform Building Code Zone I earthquake loads are 0.05g. Although the CAAB is a corrugated steel building, it is structurally sound with fairly rigorous design criteria. RAI 2: The NRC staff's understanding is that the common area of the auxiliary building (CAAB) is from elevation 755' to 809' and between columns 7 to 1 I and J to Q (from USAR Figure 1.1-8 and Figure 1.1-16). The CAAB has metal siding between elevations 775' and 809'. There are no ventilation systems directly supplying fresh air to or providing exhaust from this area. Under normal operation the CAAB pressure is maintained Page 1 of 6 Alternative Source Term - Response to RAls NSPM negative relative to atmosphere through indirect connection to one of the two unit's auxiliary building exhaust systems.

Below elevation 775: the CAAB walls are concrete construction or have adjacent unit specific auxiliary building spaces. Please verify if the NRC staff's understanding is correct or provide information needed to correct the staff's understanding.

NSPM Response:

The Staff's understanding is correct as stated in RAI 2 with the following exceptions: The paragraph describes that "under normal operation the CAAB pressure is maintained negative relative to atmosphere through indirect connection to one of the two unit's auxiliary building exhaust systems." This is not correct. There is no connection between the CAAB atmosphere and the auxiliary building exhaust system that would significantly reduce CAAB pressure below atmosphere. Under normal operation the CAAB pressure is atmospheric. The paragraph describes that "thereareno ventilationsystemsdirectlysupplying fresh air to orproviding exhaust from this area". In fact, there are ventilation systems that could (under certain conditions) exhaust air from the CAAB.

o Under normal operating conditions, a low-capacity fan draws from laundry dryers and tank vents (located in the CAAB) and exhausts into the Auxiliary Building Normal Ventilation System (ABNVS) downstream of Unit 2 exhaust fan. o Also, by an indirect and improbable means, it can be postulated that the ABNVS could draw air from the CAAB if boundary integrity is not established for the Auxiliary Building Special Ventilation Zone (ABSVZ) during extraordinary plant shutdown conditions.

Both of these exhaust paths are described later in the reply to RAI 4, in context of potential accident release paths. The paragraph also describes the CAAB boundary as 755' to 809' elevations; however, with elimination of Spent Fuel Pool Special Ventilation System (SFPSVS) boundary requirements (TS 3.7.1 3), the CAAB may be expanded to include the Spent Fuel Pool (SFP) Enclosure. Thus, the CAAB is open from the ground elevation 695' to the roof elevation 809' on the south end of the building between approximately Columns Q to P.3 bordering the spent fuel pool enclosure. The CAAB boundary then extends north along the top of the spent fuel pool enclosure, down the north wall of the Spent Fuel Pool Enclosure to the roof of the filter room at approximately M.3. The boundary then extends north along the filter room roof (el.

755') and down the north wall of the filter room to elevation 735'. There is an open stairwell and other openings around ventilation ductwork that allow communication between elevation 755' and elevation 735' in this area, such that the Laundry and Dressing Area communicates with the CAAB. There is no direct communication with rooms below these areas.

Page 2 of 6 Alternative Source Term - Response to RAls NSPM RAI 4: Please discuss releases from the Auxiliary Building Exhaust stacks (USAR Fig.

10.3-6). The auxiliary building exhaust stacks are identified on USA R Figure 10.3-6 at approximate coordinates A-9 and A-10. These exhaust stacks are not identified as a potential release point in Table 3.1-2, "Release Points and Receptor LocationsJ', of the LAR. These exhaust stacks are not discussed in LAR section 3.1.3. Discussion of the auxiliary building exhaust stacks was not identified in any other section of the LAR, however, such discussion may have been missed by the reviewer. The discussion should indicate why the auxiliary building exhaust stacks are not considered a release point. If the justification is the exhaust fans are tripped on a safety related signal at the onset of an accident (e.g., emergency diesel load sequencing), verify the fans are shut down on an accident with no loss of offsite power. If potential releases are enveloped by a more conservative release-receptor combination, please indicate so. NSPM Response:

No post-accident radiological releases from the Auxiliary Building Exhaust stacks are considered in the radiological consequence analysis because control systems ensure that (1) the normal large-capacity exhaust fans are tripped off (removing the primary driving mechanism), (2) the associated discharge dampers are isolated (providing positive isolation to prevent the passive migration of gases from the exhaust system), and (3) actuation of the special ventilation system draws a negative pressure on the ABNVS. These control functions are described more fully below, along with the special features that prevent the unique Unit 2 exhaust stack from becoming a limiting release source during radiological accidents.

At the initiation of radiological events that affect the Auxiliary Building, the ventilation system control circuit is designed to automatically actuate the Auxiliary Building Special Ventilation System (ABSVS) and isolate the ABNVS to prevent radiological release from the Auxiliary Building Exhaust Stacks. System logic circuitry ensures that these systems are actuated in the above manner whether or not offsite power is available.

Thus, the analysis does not rely on a loss of offsite power to ensure that ABNVS exhaust fans are secured. Both trains of ABSVS are actuated by either a Safety Injection (SI) signal in either unit or a High Radiation signal (in the Auxiliary Building Ventilation Exhaust ductwork).

Actuation of either Train A or Train B ABSVS fan will secure the ABNVS make-up fans and the general exhaust air fans, in addition to closing the make-up dampers and major exhaust dampers. Thus, the fans are shutdown and the flow path isolated automatically as part of the response to an accident that generates an SI signal or a High Radiation Signal. Thus, the ABNVS is automatically isolated for these events.

Page 3 of 6 Alternative Source Term - Response to RAls NSPM As described in the response to RAI 2, two possible paths have been identified where radioactivity could bypass the isolation of the ABNVS and be released to the ABNVS exhaust stack. e Under normal operating conditions, a low-capacity fan draws from laundry dryers and tank vents (located in the CAAB) and exhausts into the ABNVS downstream of Unit 2 exhaust fan.

e Also, by an indirect and improbable means, a scenario could be postulated that the ABNVS could draw air from the CAAB if boundary integrity is not established for the Auxiliary Building Special Ventilation Zone (ABSVZ) during extraordinary plant shutdown conditions. Each of these potential paths is discussed below. ABNVS Exhaust throuqh 121 Laundrv Drver Exhaust Fan For a Fuel Handling Accident (FHA), Heavy Load Drop (HLD), or Main Steam Line Break (MSLB) accident, the radionuclides released into the CAAB could migrate to a small ventilation exhaust path that originates at the laundry dryers and the Chemical and Volume Control System (CVCS) Monitor Tank vents (in the CAAB). Ventilation ductwork for this exhaust path penetrates the CAAB / Auxiliary Building boundary and exhausts through the Unit 2 Auxiliary Building Normal Ventilation (ABNV) Stack through the 121 Laundry and Monitor Tank Room fan. For simplicity, the 121 Laundry and Monitor Tank Room Fan will be referred to as the 121 Laundry Fan in this response. The exhaust from the 121 Laundry Fan is directed into the Unit 2 ABNVS exhaust line downstream of the isolation damper and is released through the Unit 2 ABNV Stack.

Thus, if the 121 Laundry Fan were running, it could provide a potential path to the environment. The 121 Laundry Fan draws air from the Laundry Dryers and the three CVCS Monitor Tanks (small exhaust from the atmosphere above the liquid inside the three tanks) on the 735' elevation of the CAAB at a low volumetric flowrate (less than 2000 cfm). Activity released from a FHA, HLD, or MSLB event would need to traverse through a relatively tortuous path to be released through the 121 Laundry Fan.

In order to reach this area of the 735' elevation, the activity needs to first reach the 755' elevation of the CAAB and go down through three relatively small openings (one stairwell and two openings provided for ductwork traverse). Notwithstanding the likelihood that dilution in the auxiliary building would significantly mitigate a radioactive release via the 121 Laundry Fan, this specific release path is not recognized and has not been analyzed in the current licensing basis. Therefore, the issue is being addressed in NSPM's corrective action program (CAP). NSPM commits to implement a plant modification that will either block the subject flow path permanently Page 4 of 6 Alternative Source Term - Response to RAls NSPM or will otherwise remove the 121 Laundry Fan exhaust path as a potential source of post-accident radioactive release through the Auxiliary Building Normal Ventilation Exhaust stack.

Conclusion As described above, the flow paths for the radioactivity from a FHA, HLD or MSLB to reach the 121 Laundry Fan are relatively tortuous and would be diluted prior to reaching the release point.

However, rather than crediting this dilution, or analyzing the ABNVS stack as a release point, NSPM has committed to install a modification that precludes a release that might be otherwise propagated by the operation of the 121 Laundry Fan.

By precluding this release path, the modification will preserve the integrity of the ABSVS zone and the AST analyses that assume the CAAB as the limiting release point. ABNVS Exhaust When ABSVZ Integritv Is Not Established In response to the RAI question, NSPM staff re-examined the radiological accidents and the possible operating conditions of the ABNVS to identify any other potential for accident release from the auxiliary building normal exhaust stacks. The only additional vulnerability stemmed from having a common ABSVS shared between the two units, in conjunction with a common Technical Specification for that system. This vulnerability is discussed below. Normally, with either unit in Modes 1-4, TS 3.7.12 would ensure the integrity of the ABSVZ prior to the accident and thereby ensure that the radiological release from a FHA and a HLD' would not escape from the CAAB into the ABSVZ. With respect to the proposed AST LAR, this ABSVZ integrity ensures the CAAB is the limiting release point for a FHA and a HLD. However, TS 3.7.12 is inadequate for the proposed amendment in that it does not ensure ABSVZ integrity for the unlikely event that neither PlNGP unit is operating in Modes 1-4. For example, if Unit 1 experienced a Mode 6 FHA when Unit 2 was in Mode 5 (or 6) with the ABSVZ compromised, the radioactive plume could be drawn from containment or the SFP into the CAAB, through the compromised ABSVZ boundary, and into the ABNVS exhaust. This path would compromise the assumption that the CAAB was the limiting release path for the FHA. To remedy this condition and restore the viability of the proposed radiological analysis that assumes the CAAB is the limiting release point, NSPM proposes a revised TS 3.7.12 to extend the ABSVZ operability statement to include the fuel handling operations that are precursors to the FHA. Thus, TS 3.7.12 will be revised to require that the ABSVS be OPERABLE during movement of irradiated fuel assemblies.

' The HLD of concern is a non-design basis event described in USAR Section 12.2.12 involving a HLD over the reactor with the containment atmosphere open to the outside. This event evokes a

-/-day minimum wait after subcriticality, and assumes a release from the CAAB. Page 5 of 6 Alternative Source Term - Response to RAls NSPM In this manner, it can be assured that the radioactive release from the FHA will be enveloped by the CAAB until released from the point assumed in the analysis. The revised TS markup is attached as Enclosure 2 to this letter. Also, for the HLD event in containment (a non-design basis event described in USAR 12.2.12), the current set of administrative restrictions does not ensure ABSVZ operability during movement of heavy loads over an open reactor vessel containing irradiated fuel assemblies (when the containment is open to atmosphere). Without ABSVZ integrity, the plume from this non-design basis event could migrate from the containment, through the compromised ABSVZ boundary, and into the ABNVS exhaust. This path would compromise the assumption that the CAAB was the limiting release path for this particular HLD event. To remedy this condition and restore the viability of the proposed radiological analysis that assumes the CAAB is the limiting release point, NSPM commits to a revised administrative restriction to require ABSVZ operability during heavy load handling operations that are a precursor to this specific HLD event. Thus, NSPM commits to implement an administrative control to require Auxiliary Building Special Ventilation Zone boundary integrity during movement of heavy loads over an open reactor vessel containing irradiated fuel assemblies when the containment atmosphere is open to the outside (as described in USAR 12.2.12). In this manner, it can be assured that the radioactive release from the HLD will be enveloped by the CAAB until released from the point assumed in the analysis.

For information, the revised USAR markup is attached as Enclosure 4 to this letter. The effect of this condition on the current radiological analysis of FHA and HLD has been identified in the NSPM CAP. Note that the aforementioned condition is not applicable to the MSLB because a logical precursor to the MSLB is the operation of the accident unit in an operating Mode 1-4, which would invoke TS 3.7.12. Conclusion As described above, TS 3.7.12 and USAR 12.2.12 do not ensure that the ABSVZ integrity will be established prior to a FHA and HLD respectively.

However, the proposed TS and USAR revisions will extend the ABSVZ operability statement to include fuel handling operations that are precursors to the FHA, and the heavy load handling operations that are precursors to the HLD. In this manner, it can be assured that the radioactive release from the FHA and HLD will be enveloped by the CAAB until released from the point assumed in the analysis.

By precluding this release path, the TS and USAR revisions will preserve the integrity of the ABSVZ and the AST analyses that assume the CAAB as the limiting release point.

Page 6 of 6 Enclosure 2 Alternative Source Term - Response to RAls Technical Specification Pages (Markup) 3 pages follow NSPM

, PLANT SYSTEMS '3 7 3.7.12 Auxilinly Builcling Special Ventilation System (ABSVS) LCO 3.7.12 Two ABSVS trains shall be CIPERABLB

---

*-----------------------

NOTE ---------------------------------------

Tile ABSVS boundary inay be opelied under nrlministrntive cont~~ol.

APPLICABILITY:

':MODES 1, 2, 3, and A. One ABSVS train itieyerahle.

ACTIONS COh,IPLE.TI ON TIME CONDITION A, 1 Restore ABSVS train to OPERABLE status. Prairie Islatld Units I iliicl 2 REQUIRED ACTION 7 rlrlys 13. Two ABSLTS traills inoperable clue to inoprrablr ABSVS boundary ie~ b8lt"1P3F5 1, L4% 111 4. -- U~lit 1 - Ain~ndlne111 No. -G; 3.7.12-1 LJilit 2 - Amenrlmcnt No. Jr4JL B. I Restore ARSVS botailclary to OPERABLE status. 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> ABSVS 3.7.12 (I'. 1CE;q~irrd A~tiallnllcl associated Cotl~pl~tio~l not 111et ial RglrSDE ?a . 2, j, -- ----A 01, *, -- -- ACTIONS (coatinilerl)

(2.1 BeinRIIODE3.

AND - 2 Be in h,IOK)E 5. 6 haws 36 hour4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />'s CORtlPLETION TIME CONDITION SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY REQUIRED ACTION Ysnirie Island U~lits I nncl 2 SR 3.7.12.1 Olzet.ntr each ABSVS t~nia for 2 15 nrinutes witla the t~e;itet's opeiv<iting.

31 clays ABSVS 3.7.12 SR 3.7.12.2 Pen'.iilm~

iaquilrd ABSVS filter testing ill nccosdnnce with the Ventilation Filter Testing Program (VFTP). SR 3.7.12.3 Verify each ABSVS trnin can produce I? negtrtive pressure within Ak ~~liiltites after' initiation.

SR 3.7.12.4 Verify each ABSVS trnin nctilntes oil an ~ctiial or simi~li~ted actuation signal. In ~ccard:\!lre with the VFTP LJnit 1 - Amelldment Nn. Unit 2 - Amenrlment No. Alternative Source Term - Response to RAls NSPM ENCLOSURE 3 Evaluation of the Proposed TS Changes PROPOSED CHANGES Brief descriptions of the associated proposed TS changes are provided below along with discussions of the justification for each change. The specific wording changes to the TS are provided in Enclosure 2.

TS 3.7.12, "Auxiliary Building Special Ventilation Svstem (ABSVS)" APPLICABILITY: The APPLICABILITY is expanded to include movement of irradiated fuel assemblies. Justification: Whereas the APPLICABILITY was previously limited to MODES 1-4, the proposed change would ensure ABSVS operability for all times that irradiated fuel is being moved (regardless of either unit's operating MODE). This change will ensure that the supporting ventilation boundaries are established during fuel movement to ensure that any release from a fuel handling accident (FHA) will be confined to the areas assumed in the radiological analyses.

CONDITION B: Consistent with the expansion of the APPLICABILITY to include movement of irradiated fuel, CONDITION B is revised to apply only during MODES 1, 2, 3, or 4. Justification: This change retains the original intent of the CONDITION, which originally applied these ACTIONS and COMPLETION TIMES only to MODES 1, 2, 3, or 4. A new CONDITION D has been created to specifically address the two-train ABSVS inoperability during movement of irradiated fuel assemblies.

CONDITION C: Consistent with the expansion of the APPLICABILITY to include movement of irradiated fuel, CONDITION C is revised to apply only during MODES 1, 2, 3, or 4. Justification: This change retains the original intent of the CONDITION, which originally applied these ACTIONS and COMPLETION TIMES only to MODES 1, 2, 3, or 4. A new CONDITION D has been created to specifically provide ACTIONS and COMPLETION TIMES during movement of irradiated fuel assemblies.

CONDITION D: The proposed change would add a new CONDITION to describe the REQUIRED ACTION and COMPLETION TIME for ABSVS inoperability during movement of irradiated fuel.

Page 1 of 2 Enclosure 3 Alternative Source Term - Response to RAls NSPM Justification: Whereas CONDITION A allows irradiated fuel movement for 7 days with one ABSVS train inoperable, the REQUIRED ACTIONS and COMPLETION TIMES of CONDITION D require immediate suspension of fuel movement when the ABSV boundary is inoperable. In this CONDITION, the ABSVS boundary would not perform the isolation function required by the radiological analyses, so the prudent action is to suspend without delay the activity that would be the initiating event for a fuel handling accident. This REQUIRED ACTION and COMPLETION TIME is consistent with a similar TS (3.7.10). In summary, these changes are acceptable because they conservatively expand the APPLICABILITY of ABSVS operability to include movement of irradiated fuel assemblies; a potential accident initiator that had not been considered previously.

The proposed CONDITIONS, REQUIRED ACTIONS, and COMPLETION TIMES are consistent with similar Technical Specifications.

Page 2 of 2 Enclosure 4 Alternative Source Term - Response to RAls NSPM TS Bases Pages (Markup) For Information Only Note that this markup includes the draft changes provided in the license amendment request dated October 27, 2009 8 pages follow ABSVS B 3.7.12 I3 3.7 PLANT SYSTEMS I3 3.7.12 Auxiliary Btillrliilg Sl>ecial Ventilation Systein (ABSVS) BASES BAC'I<GRQLhTl The ABSVS is a standky wntilation system, coil~~llor~

to the two units, thnt is designed to collect anrl filter air from the Auxiliary Building S1xcial Ventilation (ABSV) tlounclary followitl~

a loss of coolant accirle~~t (LUC'A). Tl~e ABSV bounclary contnins those areas within the auxiliary building which have thc. potential for coilecting significant containme nt leakage that coufcl bypass the sltielrl builrling ancl leakage from systems which coulrl ~rcirculatc.

primary conlnnt durifig LOC"A mitigatiuii.

The ABSVS col~sists of two il~deprildrtit and trdunclt~nt trains. Ear11 train coilsists of a I~ater, ;i prefilter, a high efficiency particulate air THEPA) filter, an acticra~erl charcoal ndsorkcr section for removal of gaseous activity (principally indines), and n fan. LIuctwsl.k, danlpers, and instl,umentation stlscr form past of the system. Tlie systenl initiates filter~cl ventilation of the ABSV boullclary following

~~ceipt of a safety iiljecfioll (SI) signal, high rudiation signal or manual initiation.

The radiation signal is tloi utrcl ited iii tlre LJSAR for accidetit mit igatiutl.

Prairie Islailcl Units 1 ancl 2 LJnit 1 - Revision -&& B 3.7.12- 1 IJtiit 2 - Revision 4+y ABSVS B 3.7.12 BASES EACI<GROITFJT)

Tile exhaust fro111 the nuin cantlenses nirqjector is cliti.ctec1 to the (continued)

ABSVS for filtering prior to ex11;iustirlg from the plnnt via tile shield builrling stack to mitigate steallm generator tubc leakage, i%irlle~l the ABSVS actuates, tile nonnal nonsafeguards supply and extlaust rlnmpers close automatically, nncl thc Auxiliary Buifiiing Normal Ventilatioa Systenm supply and eshatlst fans trip. Thc prefilters lanloc.e ally large parlicles in the air, and with the heatel~s, seduce tile level of entrained water rlroplets present, to p~vvent excessive Ionding of the HEPA filters nucl charcoal adsarbess.

The heatcrs alp rlesig~led to dry incoming air at iOO?l-) sntu~.ation by inweasing the tetmlj~eraf~ire of the air ~ntering tl~e chnrcoal becl. The air is the11 clry enouph tn sitppo~-t the char~uoal adsorber ioiliile removal efficiency requireinents.

TIP ABSVS would typically only be used fur post accirlent atn~rrspheric clemlul~ ftunclions, Tlw ABSVS and ABSV boundary are discussed in tip LJSAR tRcfercnces

1.2 arlcl

3). APPLICABLE The clesigrl basis of the ABSVS is rstnblished by the large blank SAFETY LOC'A. The potelltin1 leakage yatlls fro111 the containment to the ANALYSES auxiliary building are disct~ssed in Referrnce

1. The system evaluntion assumes n passive hi1nr.e of the ECC'S outside containtnent, such ils an RHR l~umy seal failure, cluring the recirci~lation morle (Ref. 4). In such a case, the system limits rndioactive release to within the 10 CFR -- [Lo7 (Ref. 5) Iiinits. Tire aaalysis uf the effects nnil consequenws of n Inrge bs~nk LOCA is p~setlterl is) References 3 n1lc14. The ABSVS also actr~ntes following n small break LOCA, in tilose sascs iv11cre the ECCS goes into the secirculntiotm mode of long tenn cooling, to clenn up releases of smaller leaks, such as fro111 valve stet11 packing. Prairie Islanil Units 1 and 2 Utmit 1 - Revisioll Utllt 2 - Revision -?--USA 1 ,r~l 'TWEI io~~c31~tc~t amd R dumdan~ 1rai11t; 01 kk ARSVS arc ~tjuilrd 10 tv O&3EE~2fS1,[4 1c-t ~nsarc ih:~t 34 &:as! CIIIC is availai~lc, assulriiisg

~hak a singk hiiilu~2 dis~ii311;"~

kh: c~lkizr train.

ABSVS B 3.7.12 BASES L(30 An ABSVS tt*ain is considereel OPERABLEwlleil its nssocinterl: (co~lt ii~i~eii)

a. Fnn is OPERABLE;

b. HEPA filter nnd c11nrcoal aclsorbers are capnbl~ of passing their clesig~l flow n~lcl performing their Siltsation functions;

c. Heater, cluctwosk, nncl dnn~pers are OPERABLE a~td air circulation crul Lw maintai~lrd; nncl d. Instsunlentatict~l n~ld c~lltrols nl~ OPERABLE.

The ABSV t~at~ndary is OPERABLE if both of the followin~g canelitions call he 111~1: a. Ol~wGings it1 t he ARSV bounclt~ry are under ilirect ndministrat ive cunt1.01 t~nd can be redtrced to less than 10 square feet within 6-+3 miilu tes Sollawillg ml ncciilent

nnil b. Dampers rz~~d nctuntinn circuits that isolate tile Auxiliary Builcling Nor~nal Ventilation System following an accident are CIPERABLE or can be martunlly isolated witIlillk2 minutes following an oucident.

The WO is tlaodified by 11 Note allowing the ABSV houticlary to be oj~ned unclcr ndministr:ltive controls.

As cliscussecl above, oyeaitlgs must be closecl to less tllan 10 scjunw ket witllin - minulrs following an accident.

APPLIC14131LITY In MOLIES 1, 2, 3, and 4 for either unit, tllc" ABSVS is required 10 be OPERARLE.

Prniric Islni~rl 1-Jnits I nncl 2 ARSVS B 3.7.12 BASES (conlinued)

ACTIONS ?trith one ABSVS train inoperable, actiotl must be taketi to iestore OPERABLE status within 7 days. Dirring this time, tile reillainiug OPERAI3LE train is adequate to pwfosin the ABSVS functiotr.

The 7 day Camplet ion Ti nre is rippso~~riate becnusr the ABSVS risk contribution is sutistantialfy less than that for the EC'CS (72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Clonrplction Time j. The 7 clay Co~lryletioll Titm is basrcl 011 il~e low probability of rr DRA occurring during this time periocl, and ability of thc reinaiaing train to provide the requirecl capability.

Coacurrent Saililse of two ABSVS hins wuulil result in the loss of fitnctioanl caj~ability; tllei~fore, LC0 3.0-3 nrust br ente~ecl im~lrecliately.

a11 inoperable ABSV baundnry, actiol~ ~uust br taken to i~stole OPERABLE status withi11 24 houi*s. Tllr 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Con~ylerion Tinre is lrnso~labfr hnsed on tlre lo\+! prohnbility of n DBA ooct~rring duriag this time yeriorl, arlcl i11e availability of the ABSVS to provide a Silterrd relensr (albrit with putrnt ial for some unfiltesecl leakage j. If the ABSV bounrlniy cannot be ~stolrd to OPERABLE status within the associatecl Cotnyletion Time, tlre zl~lit nus st tic placrcl in n MCIDE in which the LC0 clues not apply. Prairie Island Units I nrlcl 2 ABSVS B 3.7.12 RASES AC'TIONS C. 1 and (3.2 (continued) 1' at1 ABSVS train cannot be ~storeci to OPERABLE status or the ABSV boundary cnllilot Izr restored to OPERABLE statits within tlao :tssocinted Conlplrtion Tiulc, tile unit njttst br placed in n MODE in which thc LCO does not nplsly. To acllievc this status, the unit tnust be placed in at least M(=IT)E 3 within 6 Ilours, anrl in MODE S witl~i~l 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. TIE allnweri Co1ily1etiol-i Times are sensunable, baser1 on opwatisg esyeiiencr, to sench thc rrquirecl unit co~lriitioils from fill1 power conclit io~ls in nn orrlrrly manner nltd without cilalle~lginlg unit sy strnls. SLRVEILLANCE S R 3.7.1 2.1 IiEQIOREh,ENB This SR verifies that ear11 ABSVS t~aiu can b~ manually stwtccl and the rtssnciateil filter heater energizrs.

Standby systenls slroufrl Ire cllrckerl periurlically to ensure that thcy fitnction proper1 y. As the envirc7nrneat atlcl no1.111al cq~r rating raruiitiuns an this syste~n a18 11ot srvere, testitlg each train once u inonth provides at1 adeq\~atr check 1711 this systcm. Each ABSVS, tnnin must br opel.atrrl 2 IS minutes yrr illontl~ wit11 the t~rnters I ABSVS B 3.7.12 BASES SURVEILLANCE SR 3.7.1 2.1 (continuecl)

REic..lrlRElvENTs energized, Tlte 31 clay Flaquency is baser1 011 the kmw 11 reliability of eqrlip~lle~lt ancl tile two train redunclnncy avnilnble This SR verifies that 111e recjui~~cl ABSVS testing is performed in accorcln~lce with the Ver~tilrttio~l Filter Testing Program (VFTP). TIE VFTP inclucles testing HEPA filter performance, charcoal aclsnrL.rs cfficiency, minimum sy stem flow rate, nncl the phy sicnl prol~rties of t1= activatecl chnrcc~al (geilertal ust. nilel following sl3wific oyrsations).

Spcific test F~ec~iiencies ancl nclrlitio~~al infomat ion ma eliscussed in detail in t11~ VFTP. This SR verifies proper ftinctiuaiag of tlte ABSVS by verifying t11c integrity of the ABSV bounclary and the ability of t1x ABSVS to maintaii~

n negative pi,irssiit.r

\vit11 ~rsprct 10 potentially i.~~lcn~lta~l~it~nted adjacent arras. During the l~ost acciclcnt morle of operation, the ABSVS is desig~lecl to maintain ti slight aegative plassi1t.e within the AQSV bounclnry with respect to the uontainnlent arltl shielcl builcling. Each ABSVS trail) is starled fiun~ tile co~~trol room n11d the followi~~g nre verified:

a. Associateel Auxiliary Building Normal Ve~ltilntiotl Systetn fans trip ntlcl claml)ers close; and b. A mrasurahle nrgntive prrssurr is drawn withiu tile ABSV boi111dat.y willlin ,Irb minutes after inilialion, with a I0 scjt~al'tz foot opellillg willz ille ABSV bo1111da1-y.

Prairie Isfanrl 1Jnits I nncl 2 ABSVS B 3.7.13 BASES SLJRLrEILLANCE SR 3.7.1 2.11 Ccontinueill REQLJIRER,m The 92 clap Ftaquency is bnseil on the lil~owtl selittbilitp of equiylnent and t1~ two train redundiuicy available.

The ABSVS initiates on a safety i~!jection signal, high rficliation sign" or mt~ilual actt~atiotl, This SR verifies that each ABSVS train starts mil q~erntes on an actual or simiilatt3il safety ir!jection actuation signal or on manual ini tintion. The 24 month Frequency is consistent wit11 iadustly reliability exyrsience for. si~l~ilar equipment. The 24 1nont11 Flaquencp is acceptable since this systenl usually pilsses the Surveillnncr when yrrforlllecl.

REFERENCES I. USAR. Apyenilis G. 2. LJSAR, Section 10.3. 3, USAR, Section 14, 4. USAR,Sectiotl6.7.

5. 10CaFRM&Mi;Ei.i-17~

Prairie Islaild Units I ancl 2 Enclosure 5 Alternative Source Term - Response to RAls USAR Page (Markup) For Information Only I page follows NSPM PRAlREE ISLAND UPDA TED SAFETY ANAL YSCS REPORT USAR Section 12 Revisioti 31 Pncre 12.2.1 2-6 c. A load drop analysis was completed for lifting the Reactor Vessel Head over irradiated fwl in a11 open vessel. Tlie botto~ti of tlie reactor vessel heacl sliall not be lifted higher than an elevation of 756.5 feet (Reference 56). Tlie residual heat piping is protected from lieavy loacl clrop hazards by structural ttiembers of overlieacf floor levels; tlierefore, heavy loads tiiay be moved over tlie reactor caol~int piimp vaults without atiniinistrative control. Safe shutclown equipment is that equipment reclilireci for continuecl clecay heat removal ancl for maintaining tke plant shirtclo\~n.

The steam generators andlor residi~al heat ret-rioval systems are recli~irecl per TS 3:l. Since no single loacl can be carried over both steam generators, the ai~xilia~y feedwater, main feeelwater ancf steam piping in containt~ient are considered part of tlie safe load path. With the reactor coolant systena tempet-atul-e tlljove Rilocle 5, Cold SIintdt:)~vn, the Containment Building polar crane will not be usecf for riiovirig Ioacls ~itlioi~t specific written grocedures.

During heavy loacl lifts over the open fueled reactor vessel, at least one isolation valve will be closecl in each line penetrating tlie containment which provicies a direct path from the containttient atmosphere to tlie outside, except as ctescl-ibed below. hlovement of tlie reactor vessel heacl and i~lsper internals over the open fileled reactor after the fuel has beers si~f~cl'itical in excess of seven days is perniissible witti containment atmosphere open to the outside with tlie following restrictions (Reference 6'1 ): a. Tlie bottom of the upper internals sli~lll not be lifteci liigher than an elevation of 735'-6". 11. Administrative controls shall lje in place to provicle containment closure witliin 'I hour of a clroplled load. g C:ranes were pur-chasecl from Whiting Corporation of specification against which these cl-anes wei-e purchased s #TO. However, tile cranes were cliralifieci against EOSl 30.2-1 967. A review verifiecl the cranes substantially Specification

1. 7U. . c. Adtiiinistrative cantrols shall be in place to ensure Auxiliary Bi~ilding Special Ventilation Zotie laoirndary integrity.