ML20141L968
| ML20141L968 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 05/28/1997 |
| From: | Dennis Morey SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML19317C318 | List: |
| References | |
| 50-348-97-201, 50-364-97-201, NUDOCS 9706030268 | |
| Download: ML20141L968 (13) | |
Text
Dave r4:rsy Siuthrn Nucl:ar Vice President Oper: ting Carnpany fadey Project R0. Box 1295 Birmingham, Alabama 35201 Tel 205.992.5131 I
SOUTHERN )
May 28, 1997 CQMM Ener:y to Serve YearWorld*
Docket Nos.: 50-348 50-3M j U.S. Nuclear Regulatory Commission i ATTN: Document Control Desk l Washington, DC 20555 j Joseph M. Farley Nuclear Plant Design Basis for Tornado-Generated Missiles Ladies and Gentlemen:
During the design inspection of the Farley Nuclear Plant from January 27 through March ,
14,1997, an issue arose as to the design basis for tornado-generated missiles. This issue !
was identified as Unresolved Item 50-348; 50-364/97-201-09 in the NRC Inspection I Report, dated May 13,1997. The report stated that this issue would be further reviewed I by the NRC to determine if the tornado missile protection in the Farley design and j licensing bases included missile spectra other than horizontal missiles. It is our l understanding that the Plant System Branch, NRR will be conducting this review. 1 In order to assist the NRC in its effort, Southern Nuclear Operating Company (SNC) has I reviewed the Farley design and contemporaneous supporting or related materials pertaining to tornado-generated missiles. This review involved the assemblage of design /)
and licensing documentation and rationale dating back to the early 1970's, which, as -
expected, are not as voluminous as the record for a plant of newer vintage.
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Nevertheless, it is clear from our review that the Farley design addressed only spectra for l horizontal missiles, and the NRC concluded that the design was acceptable and in ,
compliance with applicable requirements. Our review supports this conclusion. To ;
require Farley to reevaluate or modify its design and licensing bases as a result of an interpretation of NRC requirements that is different from this previously approved NRC 'j position would not bejustified. i l 0)*4,%g63LA1
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SNC has prepared the Enclosure for your consideration relative to this issue. In addition, j Table 1, Timeline of Events and Table 2, List of Attachments are provided for your :
information. Should you have further questions, please contact David Jones of my staff at ;
- 205.992.5984. I Respectfully submitted,'
kt Dave Morey i
JMG: tormis. doc l l
Enclosure f
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cc: Mr. L. A. Reyes, Region II Administrator Mr. J. I Zinunerman, NRR Project Manager Mr. T. M. Ross, Plant Sr. Reside t Inspector Mr. L. B. Marsh, NRR - Chief, Plant Systems Branch l i
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ENCLOSURE Design Basis for Tornado-Generated Missiles Joseph M. Farley Nuclear Plant
Design B: sis for Torn:do-G:ncr:t:d Missiles Joseph M. Farley Nuclear Plant Enclosure 4
- Hackground The Nuclear Regulatory Commission (NRC), Office of Nuclear Reactor Regulation (NRR), performed a design inspection of the Farley Nuclear Plant Units 1 and 2 (Farley) from January 27 through March 14, 1997. According to the NRC Inspection Repon,
'The purpose of the inspection was to evaluate selected systems regarding their capability to perform safety functions in accordance with their design and licensing bases, and consistency of the as-built configuration and system operations with the final safety analysis report."
Resulting from that audit was NRC Inspection Report Nos. 50-348/97-201 and 50-
- 364/97-201, dated May 13, 1997. One of the issues raised in the report is Unresolved Item 50-348; 50-364/97-201-09, ' Tornado Missile Spectra"(Attachment 1). The specific question asked by the NRR inspection team was: '{W]hether the plant's design bases distinguished between horizontal and vertical /non-horizontal tornado missiles." The report stated that this issue would be further reviewed by the NRC, specifically NRR, 'to determine if the tornado missile protection in the Farley design and licensing bases included missile spectra other than horizontal missiles."
Southern Nuclear Operating Company (SNC) has prepared this position paper for consideration relative to this review. It is anticipated that this discussion will assist the NRR staffin the determination of its position relative to Unresolved Item 50-348; 50-364/97-201-09 Summary Farley was designed to meet the then proposed General Design Criteria (GDC) in 10 CFR 50, Appendix A. Like other plants of similar vintage, Farley's missile design basis protects its structures, systems and components (SSC) against certain tornado-generated missiles which were determined to be bounding cases. These bounding missiles and the criteria for determining that these missiles were bounding, were specifically questioned, evaluated and approved by the NRC during the original licensing review. Farley received its Safety Evaluation Report in May 1975 -- prior to the original version of the NRC's Standard Review Plan, which was issued in November 1975. The NRC found that these bounding assumptions provide reasonable assurance that the safety function of seismic SSCs at Farley will not be impaired by missiles and that Farley's approach to tornado missile protection complies with GDC 2 and 4. These remain the bounding missile cases for Farley. An NRC imposed reevaluation or modification of the Farley design or licensing basis to account for spectra other than horizontal missiles would be a backfit under 10 CFR 50.109.
SNC's review of other similar vintage plants indicates that these plants also did not, and were not required to, design for spectra other than horizontal missiles. The totality of
X D;siga B sis f r Tcrn:d> Generated Missiles Joseph M. Farley Nuclear Plant Enclosure these licensing bases and Farley's own licensing basis indicate that, for plants licensed at the time Farley was licensed, a design basis that only addressed spectra for horizontal missiles was in full compliance with the GDC. SNC does not believe that any new safety information exists that would warrant changing this approach to tornado missile protection.
The Approved Design Basis for Farley Alabama Power Company (APC), as owner, submitted the original construction permit application, including the preliminary safety analysis report (PSAR), for Farley Nuclear Plant on October 10,1969 for Unit I and on June 26,1970 for Unit 2. The NRC issued the construction permit on August 16,1972. APC submitted the original operating license application, including the final safety analysis report (FSAR) on August 29, 1973. On May 2,1975, the NRC issued NUREG-75/034, ' Safety Evaluation Report for Joseph M.
Farley Nuclear Plant Units 1 and 2"(SER).
Farley was designed to meet the then proposed 10 CFR 50, Appendix A ' General Design Criteria for Nuclear Power Plants"(GDC), originally published in the Federal Register on February 20,1971 (36 FR 3256). Of particular interest here is GDC 2 -
' Design Bases for Protection Against Natural Phenomena,"and GDC 4 ' Environmental and Dynamic Effects Design Bases." During the PSAR review stage and prior to the final mie publication of the GDC in the FederalRegister, APC was specifically asked by the Atomic Energy Commission (AEC) how tornado-generated missiles were addressed at the Farley Nuclear Plant. Tne AEC question was:
' Provide a discussion of the tornado design bases established for safety-significant systems and components, and structures other than the containment. Include a list of all items designed against tornado effects and describe the methods of design that will be employed."
APC responded to the question from the AEC and incorporated this response into the PSAR in Amendment 6 in October 1970 (Attachment 2'). As amended, Section 5.1.2.5(c) of the PSAR clearly identified the bounding design basis missiles as:
- 1. A 12-foot Icag piece ofwood 8 inches in diameter traveling end-on at a speed of 300 mph over the full height of the structure.
- 2. A 4,000-pound passenger auto, with a contact area of 20 ft 2, carried at a speed of 50 mph not more than 25 feet above ground l
- 3. A 3-inch diameter pipe 10 feet long traveling end-on at 100 mph over the full height of the structure.
- Attachment 2 includes the original NRC question, the stated answer, and the PSAR section revised by Amendment 6, dated 10/14DO.
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X D:siga B: sis f:r Ternid:-Generated Missiles Joseph M. Farley Nuclear Plant Enclosure The Bechtel Power Corporation (Bechtel) B-TOP-3, ' Design Criteria for Nuclear Power Plants Against Tornadoes," issued March 12,1970 (Attachment 3), and the Bechtel Civil and Structural Design Criteria for Farley Nuclear Plant, Rev. 2, May 25,1971 (CSDC),
first issued on January 16,1970 (Attachment 4) were referenced to determine the missile characteristics of the Farley Nuclear Plant design basis missiles. The B-TOP-3 report established a set of tornado design criteria for nuclear power plants, and identified a set of three bounding tornado-generated missiles virtually identical to the three design basis missiles selected by Farley.
According to the B-TOP-3 report, as incorporated into the Farley PSAR and later the FSAR, this set of tornado design criteria, which includes the tornado wind force, pressure differential, and tornado missile impingement, must be construed in concert and, when taken together, constitute the design basis for tornado missile protection. The Farley FSAR specifically provides that these three parameters are, 'hpplied concurrently in combinations producing the most critical conditions." With respect to the tornado wind force, Section 2.1 of the B-TOP-3 report describes the tornado wind force as: 'The wind force on the building shall be considered as a uniform static load and calculated on the basis of a 300 mph horizontal wind applied over the full height of the projected area." The B-TOP-3 report, as well as the Farley PSAR and FSAR, expressly exclude the effects of gust factors and variation of wind velocity with height. This characterization of the tornado wind describes a horizontal force applied across the full surface of the side of a building or structure. Therefore, by definition, the tornado wind force does not bear down on the roof or top surface (s) of a structure, rather it strikes horizontally against the side surface (s) of any obstacle in its path. The design basis tornado-generated missiles set in motion and propelled by the tornado wind and, as such, travel in the same horizontal direction as the wind force which drives them.
The fact that two of the bounding missile cases for Farley are described as ' traveling end on"and all are assumed not to tumble, establishes that the design basis missiles do not rotate in flight -- but rather travel and impact head-long into the structure. The fact that the automobile bounding missile case is described as being carried and impacting ' hot more than 25 feet above ground" clearly demonstrates a horizontal approach, parallel to the ground, and side-wall impact. This case provides the context in which all three missiles are to be constmed. In this context, the synonymous language 'ttriking at any elevation on the structure"or 'bver the full height of the structure,"used interchangeably in the license documents to describe the other two bounding missile cases, signify a horizontal missile strike impacting at any elevation along the side surface (s) of the structure. To support this view, the tornado missile discussion in Section 5 of the B-TOP-3 report explains that the automobile case was limited to a 25 foot horizontal elevation because the tornado wind force could not sustain lift of the heavy-weight object at any higher elevations of forward propulsion. In the lighter-weight missile cases, lift can be sustained at higher elevations of forward propulsion. The Figures included in Section 5 of the B-TOP-3 report demonstrate a horizontal missile approach and side wallimpact.
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Design B: sis f:r Ternido-Gen:r ted Missil:s ,
Joseph M. Farley Nuclear Plant !
Enclosure I
Although originally written for Point Beach, the methodology applied in the B-TOP-3 report was later incorporated in the generic report BC-TOP-3A, Rev 3, ' Tornado &
Extreme Wind Design Criteria for Nuclear Power Plants" and endorsed by the NRC on October 4,1974 (Attachment 5). Bechtel CSDC written for Farley was also consistent with the B-TOP-3. Section 4.2.2 of the CSDC identified the same set of bounding l
' tornado driven" missiles as those described in Farley's PSAR, (and later the FSAR). l Similar to B-TOP-3, the CSDC described the tornado wind force as follows: ' Lateral l force on the containment will be assumed as the force caused by a tornado funnel having a j peripheral tangential velocity of 300 mph and a forward progression .,f 60 mph." The phrase ' lateral force" again corroborates the characterization of a horizontal, side-impacting tornado wind force. This language was incorporated in the PSAR at Section 5.1.2.5 and later the FSAR at Section 3.2.2.1.
This issue was again reviewed by the AEC on March 6,1974. While reviewing the FSAR submittal, the Auxiliary and Power Conversion System Branch specifically asked about Farley's design basis for tornado missiles - Question APC-1. In 3 5(c) of this question, the AEC specifically asked Farley Nuclear Plant to supply information related to 6 specific l missiles (Attachment 6). In response to that question, APC stated, 'The tornado-generated missiles considered in the design of the safety-related structures of Farley Units 1 and 2 are given in FSAR Section 3.3.2.l(c) and are the same as those previously )
included in PSAR Section 5.1.2.5, ' Tornado Loads.' . Upon completion of the AEC review and favorable action by the ACRS, the PSAR section became the basis for Farley Nuclear Plant's tornado rnissile protection criteria for all safety-related structures, systems, and components."
The AEC, and subsequently the NRC, reviewed this information and, in Section 3.5,
' Missile Protection", of the May 1975 SER for Farley (NUREG 75/034), specifically approved APC's missile design basis and the criteria for determining that design basis.
This SER section concluded:
'We have reviewed the applicant's criteria for protection from postulated missiles caused by tornadoes or failure of components inside containment.
We have concluded that use of these design criteria provides reasonable assurance that the structural integrity and safety function of seismic Category I structures and components will not be impaired by potential missiles and that the use of these criteria is an acceptable basis for satisfying General Design Criteria Nos. 2 and 4 of 10 CFR 50."
(Attachment 7)
It is clear then, that the NRC specifically reviewed and approved, from both a safety and compliance perspective, Farley's existing tornado missile design basis, which assumes only horizontal missiles. The NRC did not require spectra other than horizontal missiles to be 4
Desiga B: sis for Tcrned:-Generated Missiles Joseph M. Farley Nuclear Plant Enclosure separately evaluated for' compliance with the GDC. SNC is not aware' of, nor has the NRC identified, any new safety information that would necessitate a change to the approved licensing basis.
It is also important to note that Farley was designed and received its SER before the NRC Standard Review Plan was issued in November 1975 (Attachment 8). Thus, having been issued after the NRC staffs review and approval of the Farley design, the SRP was not and is not applicable to Farley. At the time of the FSAR review, the only official regulatory guidance available to the industry was Regulatory Guide 1.76, ' Design Basis Tornado for Nuclear Power Plants,"Rev. O, April 1974. This Reg. Guide established the parameters of the design basis tornado, but did not address tornado-generated missiles.
Parameters / missile spectra of the design basis tornado missile were developed on a case-by-case basis, drawing from industry practice and documentation. Such industry documents and the design criteria contained therein, were approved and accepted by the NRC.
Desien for Snectra Other Than Horizontal Missiles was Not Reauired for Compliance with GDC 2 and 4 In the early 197U's there was documentation between the industry and with the AEC on this issue. Southern Services, Inc. (SSI) served as the Architect / Engineer (A/E) firm along with Bechtel on the Farley Nuclear Plant. Additionally, during the same period, this partnered group of SSI/Bechtel was serving in the same capacity as the Architect / Engineer on the Hatch Nuclear Plant for Alabama Power Company's sister utility, Georgia Power Company. (SNC is now the operator of the Hatch Nuclear Plant as well as Farley.)
Bechtel was also involved as the A/E of many other nuclear facilities under construction during this time period.
As early as March 5,1970, the issue of tornado missiles and their direction was a subject of discussion in the industry. Relative to the design for the Hatch Nuclear Plant, Bechtel conference notes dated March 16,1970 of the March 5,1970 meeting between SSI and Bechtel (Attachment 9) states that the 'inajor portion of the day was devoted to M. A.
Suarez's explanation of tornado missile analysis." During the meeting, a concern was voiced as to whether roofs should be designed to withstand missiles. The meeting notes stated that SSI would request further information from Bechtel on this issue. On March 17, 1970, in a letter to Bechtel, SSI requested a ' recommendation as to what, if any, missile design criteria should be applied to the roofs of the Emergency Diesel Generator Building and the Control Room."On April 27,1970, Bechtel responded to this request and stated,'No particular missile criteria need be applied to the roofs of the Emergency Diesel Generator Building and the Control Room (attached Sheet #3)." The attached i sheet #3 was a Bechtel position written by Dr. M. A. Suarez that stated the following: I i
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l Design Hrsis f:r Tcrntd:-Genercted Missiles Joseph M. Farley Nuclear Plant Enclosure Missiles on Roofs After reviewing the literature on the subject, I have arrived at the conclusion that they are either impossible or of minor importance.
The 300 mph assumed for the wooden plank demands that its trajectory follow that of the wind that causes it. This is somewhat inclined upward ;
and never, absolutely never, inclined downward.
When because ofits translational velocity the tornado passes over a roof, a suction is created by the wind as it passes. Tornadoes are famous for cleaning roofs of debris (sometimes including the roof).
It is my conclusion that roofs do not have to be designed for tornado missiles as such. At worst, some falling debris long after the tornado has passed, but these are not tornado missiles.
Signed: M A. Suare: I In addition to B-TOP-3 and BC-TOP-3A as discussed earlier, Bechtel submitted BC-TOP-9A, .Rev. 2 dated September 1974, ' Design of Structures for Missile Impact" ,
(Attachment 10) to the AEC. The AEC reviewed this document and concluded that,'the '
design criteria and procedures described by this report are acceptable to the Regulatory staff." In November 1974, the AEC Stmetural Engineering Branch, wrote in their summary of the report, 'The formulae which can be used to predict the penetration resulting from impact are included in the report. The penetration and perforation formulae assume that the missile stiikes the target normal to the .mrface, and the axis of the missile is assumed parallel to the line offlight. These assumptions result in a conservative estimate oflocal damage to the target" (Emphasis added).
The above descriptive language of BC-TOP-9A further supports the characterization of l
Farley's design basis missiles as horizontal approach, side-impacting missiles. The language "the axis of the missile is assumed parallel to the line of flight" is consistent with the PSAR and FSAR description " traveling end on" and the assumption that "the missiles do not tumble." All references reveal that the missiles are assumed not to rotate, but rather travel and impact head-long. The language "the missile strikes the target normal to the surface" demonstrates a perpendicular or ninety (90) degree missile impact with the
- surface of the structure. This characterization clearly rules out any missile spectra other i than horizontal or vertical. As discussed above, vertical missiles are likewise excluded by
! the characteristics of the bounding missile cases and the horizontal wind force which drives them.
Several nuclear facilities designed in the early 1970's used an approach similar to that as discussed above. This approach is reflected in Farley's licensing basis in the missile descriptions. These particular descriptions of the missile flight combined with the l,
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Design B: sis fzr Tcrnido-G:nersted Missiles Joseph M. Farley Nuclear Plant Enclosure 1
guidance given in B-TOP-3, BC-TOP-3A, BC-TOP-9A and the Farley SER (NUREG- l 75/034) indicate that only missiles traveling in the horizontal direction are part of Farley's j design and licensing bases. j 1
i Backfit / Conclusion Farley's licensing basis and the NRC's approval of that licensing basis are clear from the above analysis and licensing documentation. Farley's design basis, as approved by the NRC, is based on bounding missile cases driven by a defined horizontal tornado wind force. Farley was not required to design for and protect against spectra other than horizontal tornado missiles.
Farley documented its approach to this issue in both its PSAR and FSAR, and this issue was specifically evaluated and approved by the NRC on at least two occasions during the licensing of the plant. The limited guidance in the 1975 SRP on spectra other than horizontal missiles is not applicable to Farley because Farley was licensed before the SRP was issued and because Farley has an approved approach to compliance that does not i include spectra other than horizontal tornado-generated missiles. Where the NRC accepts !
a licensee's design as adequate, the NRC may not thereafler require the modification of ,
that design unless the NRC determines that it will result in a substantial increase in the i overall protection of public health and safet l justified in view of the increased SNC's protection."y and thatofthe preliminaty assessment costs the effects of the modi to reanalyze this aspect of Farley's design basis and modify the plant indicates that the cost impact would range in the millions of dollars. !
Further, SNC believes that its approved approach to this issue, which does not include l spectra other than horizontal tornado missiles, is acceptable from a safety perspective and is in full compliance with applicable regulatory requirements such that no additional action is needed on this matter. Postulation of a spectra other than horizontal missile is not
! required by applicable regulations nor Farley's licensing basis, nor does it fall within the l
compliance exception to the backfitting tule.' SNC does not believe that any new safety
- information exists that would necessitate a change in Farley's licensing basis.
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q 10 CFR 50.109(a); NRC NUREG-1409, "Backfitting Guidelines", dated June 1990; Appendix D -
Manual Chapter 0514. "NRC Program for Management of Plant Specific Backfitting on Nuclear Power Plants," dated August 26,1988, at pp. 4-5.
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- NRC NUREG-1409, Section 3, at p.12 (new technical positions or evolving technical positions that result in changes to previously approved positions are a backfit that is not within the compliance exception to the backfitting rule).
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D: sign B sis far Ternado-Generated Missiles i
~ Joseph M. Farley Nuclear Plant )
l Enclosure 1 l
-Table 1 Timeline of Events :
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l :10-10-69 APC Submitted PSAR for Unit 1 ofFarley to NRC 3
- i. 03-12-70 Bechth! Issued B-TOP-3, " Design Criteria for Nuclear Power Plants l 1- Against Tornadoes" ;
03-16-70 Bechtel Conference notes issued for March 5,1970 meeting with M. A. i Suarez about tornado missile analysis.
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03-17-70 SCS Letter to Bechtel requesting a recommendation as to what, if I any, missile design criteria should be applied to the roofs of the :
Diesel Generator Building and Control Room '
04-27-70 Bechtel Responded to SCS that no particular missile criteria need be i applied to the D/G or Control Room roofs i 06-26-70 APC Submitted PSAR for Unit 2 ofFarley to NRC .
10-14-70 APC Response to AEC Question 5.36 with identification of design ,
' basis missiles ;
02-20-71 NRC Published 10 CFR 50 Appendix A, General Design Criterion ,
(GDC) in the FederalRegister 08-16-72 NRC Issued Construction Permit for Farley j 08-29-73 APC Subinitted original FSAR to NRC 03-06-74 APC Response to Auxiliary and Power Conversion System Branch Question APC-1 reconfirming the design basis missiles
. identified in AEC Question 5.36 04-01-74 NRC lssued Reg. Guide 1.76, Rev. O, " Design Basis Tornado for Nuclear Power Plants" 08-01-74 Bechtel Issued BC-TOP-3A, Rev. 3, " Tornado and Extreme Wind Design Criteria for Nuclear Power Plants" 09-01-74 .Bechtel Issued BC-TOP-9A, Rev. 2, " Topical Report - Design of Structures for Missile Impact" '
10-04-74 NRC Reviewed and endorsed BC-TOP-3 A, Rev. 3, " Tornado and Extreme Wind Design Criteria for Nuclear Power Plants" L
05-02-75 NRC Issued NUREG-75/034, " Safety Evaluation Report for Joseph M. Farley Nuclear Plant, Units 1 and 2" Il-24-75 NRC lssued NUREG -75/087, Standard Review Plan, Section I
! 3.5.1.4, " Missiles Generated by Natural Phenomena," Rev. 0 02-17-97 NRC A&E Inspection at Farley, asked Question # Q046 about Farley design basis tornado missile spectra 05-13-97 NRC Issued Inspection Report 50-348; 364/ 97-201 with Unresolved i Item 97-201-09 l
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D: sign B: sis ftr Ternid -Gener ted Missil:s Joseph M. Farley Nuclear Plant Enclosure Table 2 List of Attachments !
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- 1. Unresolved Item 50-348; 50-364/97-201-09, " Tornado Missile Spectra"
- 2. AEC Question 5.36 on Farley PSAR regarding tornado-generated missiles &
Farley's response i
- 3. B-TOP-3," Design Criteria for Nuclear Power Plants Against Tornadoes" l (March 12,1970)
- 4. Bechtel - Civil and Stmetural Design Criteria, Joseph M. Farley Nuclear Plant, Unit 1 & 2, Rev. 2 (May 1971) ,
- 5. BC-TOP-3 A, Rev. 3, " Tornado and Extreme Wind Design Criteria for Nuclear Power Plants"(August 1974)
- 6. Auxiliary and Power Conversion System Branch Question APC-1 & FNP l response - March 6,1974 i
- 7. - NUREG-75/034, " Safety Evaluation Report for Joseph M. Farley Nuclear Plant, Units I and 2" (May 1975)
- 8. Standard Review Plan, Section 3.5.1.4, " Missiles Generated by Natural Phenomena," Rev. 0 (November 24,1975) i
- 9. Bechtel conference notes, dated March 16,1970, of the March 5,1970 i meeting between SSI and Bechtel j 1
- 10. BC-TOP-9A, Rev. 2, " Topical Report - Design of Structures for Missile Impact" (September 1974) i l
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t Design B: sis for Tern d:-Generzted Missiles Joseph M. Farley Nuclear Plant
. Enclosure ,
1 ATTACHMENT 1
i
, /,, % Drsign Basis for Tomado-Genrrited Missiles ;
/ %*,, UNITED STATES Jostph M. Farlay Nucisst Pl nt S Enclosure - Attachment 1 i E I NUCLEAR REGULATORY COMMISSION page1of 9 l
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WASHINGTON. D.C. 30055 4001 May 13, 1997
- Southern Nuclear Operating Company, Inc.
i ATTN: Mr. D.N. Morey Vice President Farley Project P.O. Box 1295 Birmingham, AL 35201-1295 -
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SUBJECT:
DESIGN INSPECTION OF JOSEPH N. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 ;
l (NRC INSPECTION REPORT NOS. 50-348/97-201 and 50-364/97-201) 4
Dear Mr. Morey:
- From January 21 through March 14, 1997,.the staff of the U.S. Nuclear l Regulatory Cosmission (NRC), Office of Nuclear Reactor Regulation (NRR),
i performed a design inspection of the Unit I auxiliary feedwater (AFW) system, l the Unit 2 component m ling water (CCW) system, and their support systems at i the Joseph M. Farley % clear Plant. The purpose of the inspection was to
- evaluate the selected systems regarding their capability to perfom safety i functions required by their design bases, adherence to their design and i licensing bases, and consistency of the as-built configuration and system j operations with the final safety analysis report (FSAR).
l The enclosed report discusses the results of this inspection. Overall, the i inspection team detemined that the selected systems are capable of performing i their intended safety functions and have adequate design margins. Your staff j has implemented appropriate measures to resolve the immediate concerns identified by the team, and the team did not have any unresolved operability concerns.
Although we consider the safety system self-assessments performed by your staff to be a positive initiative, the assessments did not identify and correct many of the issues raised by the team. The Farley design and licensing bases have been adequately implemented in all but a few instances.
The system design documents adequately support the design, except as identified la the inspection report. Your engineering staff demonstrated adequate knesledge of the systems evaluated and provided excellent support to the inspectien team.
The team had concerns with inadequate tornado missile protection of the turbine-driven AFW (TDAFW) pump vent stack and the exposed piping connections, level transmitter, electrical conduits and cables of the condensate storage tank (CST). The as-built plant configuration for these did not conform to the
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O Drsign Bisis for Tornado-Generated Missiles Jossph M. Fartsy Nuclsar Plant Enclosure. Attachment 1 Page 2 of 9 Mr. D. N. Morey Farley design and licensing bases. In addition, the exhaust silencers for the diesel generators (including the station blackout diesels) were not protected against vertical and other non-horizontal missiles. The NRR staff will review this issue assocTated with the diesel generators to determine whether the tornado missile protection in the Farley Unit I and 2 design and licensing bases included missile spectra other than horizontal missiles.
Evaluations of plant modifications, conducted in accordance with 10 CFR 50.59, were generally adequate. However, the team identified certain examples of j inadequate safety evaluations. For example, the 10 CFR 50.59 evaluation for i
an FSAR change deleting the requirement for tornado missile protection for i several CST piping connections did not identify a potential unreviewed safety i question. Your staff evaluated this issue, notified the NRC in accordance i with 10 CFR 50.72, on February 27, 19g7, and implemented interim corrective
! actions to maintain the operability of the system until the issue can be
{ resolved.
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{ The team identified testing and survetilance deficiencies. For example, the i
TDAFW pump discharge check valves were not tested in the reverse direction.
The corrective action for a notics of violation for a similar issue did not j thoroughly address the check valve testing deficiency.
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The team noted design control issues for calculations, as well as
! nonconservative assumptions and inputs in calculations. In addition, the team l identified discrepancies between the FSAR and other docusesits, such as
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I procedures, functional system descriptions (FSDs), calculations, and drawings.
l Please provide a schedule, within 60 days, detailing your plans to complete
- the corrective actions for the open items listed in Appendix A to the enclosed l report. This schedule will enable the NRC staff to plan for the reinspection i
and closecut of these items.
As with all NRC inspections, we expect that you will evaluate the l applicability of the results and specific findings of this inspection to other j systems and components throughout the plant.
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1 Drsign Basis for Tornado-Gtn:rcted Missiles i Jos:ph M. Farl:y Nucl:Cr PI:nt ,
Enclosure Attachment 1 1 Paga 3 of 9 Mr. D. N. Morey In accordance with 10 CFR 2.790(a), a copy of this letter and the enclosure will be placed in the NRC Public Document Room. Any enforcement action resulting from this inspection will be handled by NRC Region 11 via separate correspondence. Should you have any questions concerning the enclosed inspection report, plea:;e contact the project manager, Mr. J. I. Zinnerman, at (301) 415-2426, or the inspection team leader, Mr. R.K. Mathew, at (301) 415-2963.
Sincerely, Robert M. Gallo, Chief Special Inspection Branch Division of Inspection and Support Programs i Office of Nuclear Reactor Regulation !
Docket Nos.: 50-348 and 50-364
Enclosure:
Inspection Report 50-348/97-201 and 50-364/97-201 cc: see next page i i
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- DIsign Basis for Tomado-G;nzrcted Missiles i Joseph M. Farby Nucl3rr Plint Enclosure - Attachment 1 Page 4 of 9 U.S. NUCLEAR REGULATORY Com 1SSION
- j. Report Nos.: 50-348/97-201 and 50-364/97-201 1
! Licensee: Southern Nuclear Operating Company, Inc.
i' Facility: Farley Nuclear Plant, Units 1 and 2 j Location: 7388 North State Highway 95 i Columbia, AL 36319 i
Dates: January 27 - March 14. 1997 Inspectors: R. K. Mathew, Team Leader, Special Inspection Branch j, C. J. Baron, Stone & Webster Engineering Corporation i P. Bionick, Stone & Webster Engineering Corporation l R. B. Bradbury, Stone & Webster Engineering Corporation D. Schuler, Stone & Webster Engineering Corporation Approved by: Robert M. Gallo, Chief l Special Inspection Branch Division of Inspection and Support Programs ,
Office of Nuclear Reactor Regulation l
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1 l D: sign Basis for Tomado-Grnzrated Missiles
! Joseph M. Farlay Nuctxr Ptnt Enclosure . Attachment i f Page 5 of 9 l TABLE OF CONTENTS l
j EXECUTIVE SLSOMRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . i El Conduct of Engineering ....................... 1 l
! El.1 Inspection Objectives and Methodology . . . . . . . . . . . . . . . 1
! El.2 Auxiliary Feedwater System .................... 1
! E1.2.1 System Description and Safety Functions . . . . . . . . . . 1
- E1.2.2 Mechanical Design Review ................. 2 j E1.2.2.1 Condensate Storage Tank . . . . . . . . . . . . . . . 2 i E1.2.2.2 AFW System Performance ............... 7
- E1.2.2.3 AFW System Valve Operation ............. 8 1 E1.2.2.4 AFW System Testing ................. 9
! E1.2.2.5 AFW System Modifications .............. 12 l E1.2.3 Electrical Design Review ................. 13
- E1.2.3.1 Turbine-Driven AFW (TDAFW) Uninterruptable Power l System (UPS) ..................... 13 j E1.2.3.2 AFW Electrical Loads ................ 15 ,
E1.2.3.3 Electrical AFW Modifications ............ 16 i
! E1.2.4 Instrumentation & Controls (I&C) Design Review . . . . . . 17 l E1.2.4.1 Condensate Storage Tank . . . . . . . . . . . . . . . 17
! E1.2.4.2 Instrument Loop Uncertainty Calculations ...... 18 i E1.2.4.3 Instrument Setpoint Uncertainty Program . . . . . . . 19
- E1.2.4.4 Modifications and Othet Reviews . . . . . . . . . . . 19 j E1.2.5 System Interface ..................... 21 i
E1.2.5.1 Service Water (SW) System . . . . . . . . . . . . . . 21 E1.2.5.2 Instrument Air (IA) System ............. 21 E1.2.5.3 Main Steam (MS) System ............... 22 E1.2.6 System Walkdown ..................... 23 E1.2.7 FSAR, FSD and Other Reviews . . . . . . . . . . . . . . . . 26 El.3 Component Cooling Water (CCW) System ............... 28 E1.3.1 System Description and Safety Functions . . . . . . . . . . 28 E1.3.2 Mechanical Design Review ................. 29 E1.3.2.1 CCW System Performance ............... 29 E1.3.2.2 ,CCW Surge Tank ................... 32 E1.3.2.3 CCW System Containment Isolation .......... 33 EI.3.2.4 CCW System Testing ................. 34 El.3.2.5 CCW System Modifications .............. 36 Et.3.2.6 Other Related CCW System Review . . . . . . . . . . . 39 E1.3.3 Electrical Design Review ................. 40 E1.3.3.1 CCW Electrical Loads ................ 40 ,
E1.3.3.2 CCW Swing Pump Operation .............. 41 1 42 1 E1.3.3.3 Electrical Modifications ..............
43 E1.3.4 Instrumentation & Controls (I&C) Design Review ......
El.3.4.1 CCW Surge Tank Level Setpoint . . . . . . . . . . . . 43 E1.3.4.2 Instrument Loop Uncertainty calculations ...... 43 E1.3.4.3 Setpoint Indexes and Other Reviews .... . . . .. 44
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i D: sign Basis for Tcrnado-G:n rated Mi I Joseph M. Fari:y Nucinr Plant' . '
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Enclosure . Attachment 1 I E1.3.5 System Interface Design Review *
............ 45 E1.3.5.1 Service Water (SW) System . . . . . . . . . . . . . . .. 45 E1.3.5.2 Instrument Air (IA) System ............. 45 E1.3.5.3 Auxiliary Buildin 46 E1.3.5 System Walkdown . . . .g Ventilation (ABV) System . . . . .
........... 46 E1.3.7 FSAR and FSD Review . . . . . . . . . . . .. ... .. .. ... .... 47
- E1.4 Other Related Electrical Systems Review . . . . . . . . . . . . . . 48 E1.4.1 AC System . . . . . . . . . . . . . . . . . . . . . . . . . 48 E1.4.2 125 Vuc Battery Systems . . . . . . . . . . . . . . . . . 49 E1.4.3 Modifications . . . . . . . . . . . . . . . . . . . . . 52 E1.4.4 System Walkdown . . . . . . . . . . . . . . . . . .
. . 53 i E1.4.5 FSAR and FSO Review . . . . . . . . . . . . . . . . . . . 54 j
4 E1.5 Control of Calculations . . . . . . . . . . . . . . . . . . . . . . 56 XI Exit Meeting Summary ....................... .
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i APPENDIX A - DPEN ITEMS. . . . . . . . . . . . . . . . . . . . . . . . . . A-1 APPENDIX B - EXIT MEETING ATTENDEES. . . . . . . . . . . . . . . . . . . . B-1 APPENDIX C - LIST OF ACRONYMS USED . .*. . . . . . . . . . . . . . . . . . C-1 APPENDIX D - LIST OF DOCUMENTS REVIEWED. . . . . . . . . . . . . . . . . . D-1 i I 4
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! Dssign Basis for Tornado-Gantrated Missiles 1 i Joseph M. Fcrisy Nuclesr Plate Enclosure - Attachment 1
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Page 7 of 9 i EXECUTIVE SumARY i
e From January 27 through March 14, 1997, the staff of the U.S. Nuclear i Regulatory Commission (NRC), Office of Nuclear Reactor Regulation (NRR),
i Special Inspection Branch, conducted a design inspection at Units 1 and 2 of j the Joseph M. Farley Nuclear Plant. Specifically, this inspection included visits to the licensee's engineering offices and the plant site on February 3-i 7, February 17-28, and March 10-14, 1997. The inspection team consisted of a i team leader from the NRR and four engineers from the Stone & Webster Engineering Corporation.
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! As the fucus of this design inspection,- the team selected the Unit I auxiliary l feedwater (AFW) system, the Unit 2 component cooling water i their support systems, because of the importance of these sy(CCW) stems in system, and
{ mitigating accidents at Farley. The purpose of the inspection was to evaluate i the capability of the selected systems to perform safety functions required by I their design bases, as well as the adherence of the systems to their respective design and licensing bases, and the consistency of the as-built !
I configuration and system operations with the final safety analysis report j
. (FSAR). To achieve this purpose, the team followed the engineering design and i
! configuration control section of Inspection Procedure 93801. The team also selected and reviewed relevant portions of the FSAR, design-basis documents, i
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Technical Specifications (TS), drawings, calculations, modification packages, procedures, .and other plant-related documentation. ;
Overall, the inspection team detemined that the selected systems are capable of performing their intended safety functions and have adequate design ;
margins. The interaction and communication between the plant, home office ;
engineering, and engineering contractors were well managed. Moreover, the l engineering staff exhibited adequate knowledge of the systems evaluated and d
provided excellent support to the inspection team. The team also found that I the Farley design and licensing bases have been adequately implemented in all
! but a few instances, and the quality of calculations and design changes was
! generally good. Although we consider the safety system self-assessments for :
j AFW and CCW systems perforised by the licensee to be a positive initiative, the '
4 assessments did not identify and correct many of the issues raised by the I team. In addition, the system design documents reviewed by the team l adequately supported the design, with the exception of the items discussed in the following paragraphs.
i The licensee's evaluations of plant modifications, conducted in accordance l with 10 CFR 59.59, were generally adequate. However, one 10 CFR 50.59 safety evaluation performed as a result of a licensee self-initiated safety system
- assessment associated with an FSAR change deleting the requirement for tornado j missile protection for several condensate storage tank (CST) piping i connections failed to identify the existence of a potential unreviewed safety 2 question. As a result of the team's questions, the licensee reported this
{ issue, in accordance with 10 CFR 50.72, on February 27, 1997, and implemented i interim corrective actions to maintain the operability of the system until the j issue can be resolved. In a similar instance, the 10 CFR 50.59 evaluations for a c lance test procedure and FSAR revision did not identify that a l
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- DIsign Basis for Tornado-Gznzrated Missiles '
Joseph M. Farlsy Nucint Plant '
Enclosure - Attachment 1
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Page 8 of 9
! technical specifications change was required as a result of changes to an j Auxiliary Building battery profile and associated battery voltage j requirements.
i The team also observed inadequate tornado missile protection of the turbine-
] driven AFW (TDAEW) pump vent stack and the CST level transmitters, and their i
i associated electrical conduits and cables. The as-built plant configuration did not conform to the design and licensing bases requirements concerning tornado missile protection. In addition, the exhaust silencers for the diesel j
generators (including the station blackout diesels) were only protected i
against horizontal tornado missiles, although the equipment is also i
susceptible to vertical and other non-horizontal missiles. The NRR staff will review this issue associated with the diesel generators to determine whether
! the tornado missile protection in the Farley Unit 1 and 2 design and licensing j bases included missile spectra other than horizontal missiles.
1 The TDAFW pump discharge check valves were not tested in the reverse i 4
direction, and the surveillance test procedure acceptance criterion for
- forward flow testing of certain AFW check valves was incorrect. In addition, i
the corrective action for a notice of violation for a similar issue did not i thoroughly address the check valve reverse flow testing deficiency. Another !
l testing issue included the lack of a service test for the Class IE TDAFW l battery.
. The team identified certain design control weaknesses for calculations.
Superseded calculations were not always identified on the calculation index, and design-basis calculations were not always updated when design conditions changed. The licensee implemented controls for new calculations that would prevent such occurrences in the future. However, no action was taken to correct deficiencies with existing calculations.
The team's other concerns included : the design-basis differential pressures for several motor-operated containment isolat' on valves were incorrect; the fluid temperatures used in the CCW piping stress analyses did not use the maximum operating temperature; the setpoint calculation for the CST low-level alares did not consider drift and deadband errors; process and documentation discrepancies in the modification to coat portions of the CCW heat exchangers with epoxy and stabilize / plug tubes, as well as the lack of specific documentation demonstrating the adequacy of a fire protection seal; and the installed configurations of the TDAFW battery rack and the CST level transmitter more not in accordance with design requirements.
The team identified discrepancies between the FSAR and other documents, such as functional system descriptions (FSDs), procedures, calculations, and drawings. In some cases, the licensee had not updated the FSAR or performed safety evaluations to assess the possibility of unreviewed safety questions.
The licensee's corrective measures effectively resolved the immediate concerns identified by the team, and the team did not have any unresolved operability concerns.
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I l Drsign Basis for Tornado-G:ntrated Missi6es ' !
Joseph M. Fedzy Nuclstr Plint >
i Enclosure - Attachment 1 i Page 9 of 9 j The licensee prepared a draft safety evaluation, which reflected the use of ,
one EAFW pump to shutdown the plant in the event that the vent stack was !
i damaged. The licensee stated that this approach could result in a potential
! USQ, requiring prior NRC approval. ,
I j An analysis will be prepared to evaluate the effects of the applicable tornado i missiles striking the exposed vent stack. This analysis would determine if l j the TDAFW pump would remain operable after the event. If this analysis shows I j that the TDAFW pump would remain operable, a safety evaluation will be !
i prepared to revise the FSAR. l 1
- If neither of the above items are favorable, then appropriate modifications to
! the vent stack would be implemented to prevent missile damage.
l The licensee issued ABN-97-0-1043 to address this item.
1 1 2. Diesel Generator Exhaust Silencers
! The team also observed that the safety-related emergency diesel generators and I l the station blackout diesel generator exhaust silencers for both units were l
! installed outside, on the roof of the diesel generator building. This equipment appeared to be protected from horizontal tornado-generated missiles by the building walls. However, the equipment was susceptible to vertical ;
j missiles and other non-horizontal missiles. j i l 1 FSAR Section 3.5.4 states that Category I equipment and piping outside l j containment are either housed in Category I structures or buried underground. )
- FSAR Table 3.2-1 addresses the tornado missile protection of the emergency i i diesel generators. FSAR Table 3.2-1 did not address the exhaust silencers associated with the generators. FSAR Section 3.5.2.1 discusses the types of missiles considered for missile protection. However, the missile spectra were not clearly defined. The team asked if the plant's design bases distinguished between horizontal and vertical /non-horizontal tornado missiles, and if the current design was consistent with the design bases.
l The licensee stated that, although the FSAR did not distinguish between horizontal and vertical /non-horizontal missiles, a horizontal missile was evident as the design basis for the plant. However, the licensee could not provide any documentation clearly supporting their statement. This issue will be further reviewed by the NRC to determine if the tornado missile protection in the Farley design and licensing bases included missile spectra other than horizontal missiles. This issue was identified as Unresolved Item 50-348; 1 50-364/97-201-09. The licensee issued REA 97-140g to address this ites.
- 3. AFW Flan Control Valves l During a Unit 1 AFW system walkdown on February 6,1997, the team observed that one of the safety-related, air-operated AFW flow control valves (HV-32278) had been tagged with a Deficiency Report (DR) 547310 indicating that screws were missing. The team observed that the missing screws were required to hold a solenoid valve to a bracket on the valve actuator. The solenoid valve was temporarily attached to the actuator with tie wrap. The 24
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Desig2 B: sis for Tcrn:d -Genercted Missi>les Jos:ph M. Ferley Nuclear Plant Enclosure ATTACHMENT 2 1
i Il D: sign B: sis for Tornado-gin: rated Missiles Joseph M. FartIy Nucl:ar PL:nt ,
Enclosure - Attachment 2 i Page ' of 4 l Question 5.36: Provide a discussion of the tornado design bases established for safety-significant systems and
. components, and structures other than the containment. )
Include a list of all items designed against tornado 6 effects and describe the methods of design that will be employed.
i Response: Response incorporated by Amendment 6 in PSAR, Section 5.1.2.5.
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'~. As,end. 6 - 10/14/70 5.36-1
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DIsign BIsis for Tornado-Gintrated Missi6 e J seph M. Fairy Nucizr Pla it 5*1 2*5 I2rnado iceds, Enclosure - Attachment 2-Page 2 of 4 l The contairusent, auxiliary building, diesel generator building and service water intake structure at the storage pond will be designed to withstand 6 tornado loadings and will provide protection against tornado missiles for
- class 1 systems and components within these structures.
The design pressure drop due to a tornado will be assumed to be 3 psi in 3 i
seconds. This is 100 perces.c greater than the maximum pressure ever reliably
'j measured, which is quite conservative.
i l Because of the complexity of the airflow in a tornado, it has not been possible j to calculate the velocity or trajectory of missiles that would truly represent l tornado conditions. It is assumed that objects of low cross-sectional density, such as boards, metal siding and similar items, may be picked up and carried
- ~ at the maximum wind velocity of 300 mph. A discussion of the probability of tornado occurrences is presented in Section 2.
! The structure will be analyzed for tornado loading not coincident with the
} LOCA or earthquake. The following basis will be assumed and all three loading
- conditions applied stealtaneously:
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i (a) Differential pressure will be applied as a 3 psi positive
! (bursting) pressure occurring in three seconds; f
l (b) Lateral force on the containment will be assumed as the
] force caused by a tornado funnel having a peripheral i tangential velocity of 300 mph and a forward progression i of 60 mph. The applicable portions of wind design methods described in ASCE Paper No. 3269 will be used, particularly j for shape factors. The provisions for gust factors and variation of wind velocity with height will not apply.
The average tornado design dynamic wind pressure is 230 i psf based on an average wind velocity of 300 mph. The j dynamic wind pressure is calculated from the following equr. tion:
2 q = 0.002558 V where, 9 = pressure in psf
. V = wind speed in aph ,
i a (c) .A tornado driven missile equivalent to a 12 foot long piece of wood 8 inches in diameter traveling end-on at a speed of 300 mph over the full height of the structure,
- or a 4000 pound passenger auto, with a contact area of 20 ft2, carried at a speed of 50 mph not more than 25 feet above ground, or a 3 inch diameter (ID) pipe 10 feet long traveling end-on at 100 mph over the full height of the structure.
Structures protecting Class 1 equipment which may be exposed to tornado missiles will be of sufficient thickness to prevent missile e ! The depth 5-3 3 - 10/14/70
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DIsign B: sis for Tornado-GEnersted Missiles Joseph M. Ferhy Nuclair Pl:nt ;
Enclosure - Attschment 2 Page 3 o ' 4 4
to which a given tornado missile will penetra* a con-l crete wall may be calculated by use of the modified
{ Petry formula as presented in Nov Docks P-51. This a formula is given in Section 5.1.4.11 of the PSAR. Where
}' required by analysis, the inside surfaces of structures 6 j will be covered with metal deck to contain any spalled i pieces of concrete which may result due to missile j impact.
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! Except for local crushing at the missile impact area, the allowable stresses j ,
to resist the effects of tornadoes will be 90 percent of the yield of the i reinforcing steel and 85 percent of, the ultimate strength of the concrete.
!' Selection of these values is based on the following considerations and on j the presentation submitted on the Iowa Electric Light and Power Company's j Duane Arnold Unit 1, Docket 50-331.
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,- Tornado design criteria requires that either Ultimate strength Design (USD) methods be used in accordance with ACI 318 63, Part IV or that Working
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- Strength Design (WSD) methods be .used with the above allowable stresses.
l The philosophy of assigning load factors to tornadoes is similar to the 1 1
! philosophy behind a 1.0 load factor for the design basis earthquake.
t The conservatius the USD procedures is discussed by A. Mattock, L. Kriz, l and E. Hognestad
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- The conservaties of using WSD with f,=9fy and fe=.85fc can be established by ,
comparing the moment capacity of a given* bean using both USD and WSD methods. ;
l Nomenclature used in the following equations is given in ACI 318-63 Code. l l
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!- Musd = Ct Musd
$ A, fy d (1- )=Ct As fs d(1- ) (2)
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- Let l Is=C,y f, = Ce fe W
g (f. As 1.7bd h)=C C s(1-fbd f' I 1
qfj) (4)
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! $ = .9; C, = .9; C, = .85 l t. As fv j 1.7bd f6 1-2&& '9Y (5)
{ 3 bd .85 f' i
5-3a Amend. 6 .-,
I i Drsign Basis for Tomado-GIntrated Missiles Joseph M. Ftrisy Nucloir Pl:nt i Finally leetins Enclosure - Atta< hment 2 Paile 4 of 4 f
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- 9= (6) i GF C i
! C 1 .59e g = 1 .71 9 (7) i Wus Cg is greater than 1 and equation (1) becomes Nsd > Nsd (8)
I hus a design using WSD with allowable stress steel f = .9 f y
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6 concrete f, = .85 fe l
i i is more conservative than USD design, which is an acceptable design pro-j cedure.
i I 5.1.2.5.1 Blowout Panels t .
j he use of blowout panels is not presently being contemplated in the design l
of the Farley Plant. We river intake structure and service water struc-
- ture will be permanently vented. Considering this permanent venting, an j analysis will be made to determine the pressure differentials resulting from
- an idealized Hoecker pressure profile. he diesel generator building and ;
. auxiliary buildings will be designed to withstand the' full pressure differ-
) ential without any venting. However, if the requirements for blowout panels l l . becomes evident, the tornado analysis described in Section 3.1.1 of Appendix j 5A will be used.
t Se force on a well or slab due to the tornado pressure differential will j
! be computed as.the pressure differential multiplied by the gross area of j the wall or slab. Se area occupied by vents will not be deducted from the gross area. We capscity to resist this force will be calculated using the !'
net structural area, that is, the gross area minus the area of openings.
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5.1.2.6 Operatina Thermal Load ;
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1 The temperature gradient through the contairment wall during normal operation i is shown in Figure 5-6. For the normal opecatir:g condition a low mean winter i temperature of 20 F will be assumed to exist at the outside face of the con-
) crete, and an operating ambient temperature of 120 F at the inside face.
1 Thermal loads due to transient wall temperatures over a prolonged shut-I down will also be considered in the design and will be combined with other ,
! loads according to equations (d) of Section 5.1.4.5. l
! Amend. 6 - 10/14. %
- 5-3b 2 Amend. 5 - 9/14/70 l
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l Design Brsis for Torn do-Gener:ted Missiles Jos:ph M. Fcriey Nuclear Plant
. Enclosure l
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