05000443/LER-1992-013, :on 920827,determined That Six Plant Doors Did Not Have Tornado Design to Withstand Differential Pressure, Per Updated Fsar.Caused by Failure to Include Doors in United Engineers & Constructors Spec.Updated FSAR Revised
| ML20127L470 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/18/1992 |
| From: | Peschel J NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | |
| Shared Package | |
| ML20127L467 | List:
|
| References | |
| LER-92-013, LER-92-13, NUDOCS 9211240284 | |
| Download: ML20127L470 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) |
| 4431992013R00 - NRC Website | |
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..n.n,-,,~,............-.-...-..,o.1 t)n August 27, 1992 North Atlantic I!ncrgy krvice Co poration (North Atlantic) determined that a reportable condition exists involving the tornado design of rix plant doors.
The affected doors are not designed to withstand the differential pressure of the design basis tornado as defined in the Updated Final Safety Analysis Iteport (UFSAlt). Ilowever, they are either designed to withstand the differential pressure of the Scabrook Station site specifi.
tornado, or the affected safety related plant ecluipment has been evaluated for the associated depressuritation effects.
UFSAll section 2.3.1.2.b.2 states that all scismic Category I structures at the Scabrook site, with the exception of the refueling water tank, spray additive tank enclosure and the cooling tower, are designed to withstand the design basis tornado as described in llegulatory Guide
- 1. 7 f>. One of the characteristics of the llegulatory Guide design basis tornado is a pressure drop of 3.0 pounds per square inch (psid). The six plant doors which are not designed to withstand the 3.0 paid differential pressure include two doors in the !!mergency I cedwater l'umphouse, and one door each in the Primary Auxiliary llullding,1:esidual llcat itemoval Vault, Fuel Storage fluilding, and Main Steam and Feedwater Pipecha te. North Atlantic has evaluated these six doors u61ng the site specific lornado data. This evaluation determined that the: door: are either designed to withitand the differential pressure of the Scabrook Station site specific tornado, or the affected safety related plant equipment has been evaluated for the associated depressuri/ation effects, in addition, North Atlantic verified that each of the plant spaces associated with these doors is protected from tornado missile strikes.
This condition is outside the plant design biais as documented in the UFSAlt and is being reported putsuant to 10 CFit 50.73(a)(2)(li)(II).
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w e - nn 11 A CKGit OU N D On August 27, 1992 North Atlantic Energy Service Corporation (North Atlantic) determined that a reportable condition exists involving the tornado design of six plant doors. The af fected doors are not designed to withstand the differential pressure of the design basis tornado as Jefined in the Updated Final Safety Analysis Report (UFSAR). Ilowever, they are either designed to withstand the differential pressure of the Seabrook Station site specific tornado, or the affected safety related plant equipment has been evaluated for the associated depressurization effects.
- Design liases for Protection Against Natural Phenomena
- of Appendix A to 10 CFR 50 requires, in part, that structures, systems, and components be dee,igned to withstand the effects of natural phenomena such as tornados without losing the capability to perform their safety function Regulatory Guide 1.117, ' Tornado Design Classification", provides guidance for identifying the structures, systems, and components that should he protected from the design basis tornado. Regulatory Guide 1.76, ' Design liasis Tornado for Nuclear Power Plants", describes the acceptable design basis tornados for each of three regions wishin the contiguous United Statet,.
t gulatory Guide 1.76 locates Seabrook Station in Tornado Intensity Region I.
The keCulatory Guide 1.76 value for differential pressure of the design basis tornado in Tornado Intensity Region I is 3.0 psid. This value, and the other parameters which define the design basis tornado in Regulatory Guide 1.76, are specified in UPSAR section 2.3.1.2.b.2.
Regulatory Guide 1.76 also allows the use of a site specific tornado in place of the design basis tornado described in Regulatory Guide 1.76, Table 1, provided a comprehensive analysts is performed to justify the use of less conservative design basis tornado characteristics.
UFSAR section 2.3.1.2,b.2 states that all seismic Category I structures at the Seabrook site, with the exception of the refueling water tank, spray additive tank enclosure and the cooling tower, are designed to withstand the design basis tornado as described in Regulatory Guide 1.76.
liowever, six doors were not designed to withstand the differential pressure of the Regulatory Guide 1.76 design basis tornado. These doors are in structures described in Regulatory Guide 1.117 for which tornado protection should be provided. The doors are located in the Emergency Feedwater Pumphouse (two doors), the Primary Auxiliary 13uilding roof, the Residual lleat Removal Vault, the Fuel Storage lluilding, and the Main Steam and Feedwater Pipechase.
North Atlantic performed an evaluation of the site specific meteorological conditions. This evaluation determined that the differential pressure experienced during the site specific tornado is leis than 1.5 psid.
Ilowever, this site specific tornado data has not been documented as the design basis tornado via inclusion in the UI'SAR.
North Atlantic has evaluated the six doors specified above and verified that the doors are designed to withstand a differential pressure of 1.5 psid, or the affected safety related plant equipment has been evaluated for the depressurization effects of the site specific tornado.
This evaluation also verified -that adequate protection against, irnado missile strikes exists I
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SAFl!TY CONSPOURNCES There are.no adverse safety consequences associated with this condition. North Atlantic has evaluated the six doors which are not designed to withstand a diffuentia! pressure of 3.0 psid and determined that they are fully capable of withstanding the cifects of a site specific tornado or the affected safety related plant equipment has been evaluated for the associated depressuiiration effects.
The use of site specific tornado characteristics is allowed by Regulatory Gt ide 1.76.
In addition, each on the plant spaces associated with a door which is not designed to withstand a differential pressure of 1,5 psid was evaluated to ensure that protection from tornado missiles exists.
ROOT CAlgli There are two issues surrounding this condition which must be addressed. lThe first is the reason the six doors were not included on the UE&C door speelfication as tornado barrier doors. The second is why, when it was discovered that the doors were not designed to meet the differential pressure value stated in the UFSAR, the condition was not reported to the NRC and why the UFSAR data was not updated to reflect the site specific tornado data.
4 1.
Doors not included in the UI!&C Sorcificatiqp_.
The responsibility for plant barriers during and immediately following the construction of the plant was divided among several engineering groups. This included providing tornado barrier information on numerous drawings. It was only when North Atlantic was consolidating this information into a single design basis document that the six doors were identified as tornado barriers which had not been included in the UEAC door specification.
A contributing factor is the fact that five of the six doors were not on exterior perimeter walls, making them unlikely tornado barriers, llowever, when plant walkdowns were performed and plant barrier draiwings consolidated as part of developing the Design Basis Document for Plant Harriers, the fact that these doors would be exposed' to the differential pressure conditions imposed by a tornado became evident.
The comprehensive review of plant barriers indicates that this
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condition is isolated to these six door:
2.
Condition not renorted and UFS AR not undatei The North Atlantic personnel that identified the nonconforming condition properly evaluated the condition and determined, based on a preliminary review, that the plant was able to withstand a site specific tornado. Ilowever, these personnel did not
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recognire that this condition was reportable and did not recognize the need to update the UFSAlt. In the final analysis, the failure to repost the nonconforming condition and to update the UPSAll resulted from a failure to implement the North Atlantic corrective action process, COltitliCTIVE ACTIONS 1mmeditite Actioni 1.
North Atlantic reported this condition via a one hour verbal notifleution purtuant to i
10 CFit 50.72(b)(ii)(ll) on August 27, 1992.
S hor t Te r m Actiwni 1.
North Atlantic followed up the one hour notification with a 1.icensee Event lleport (IElt 92-013 00) on September 25, 1992 pursuant to 10 CFit 50.72(a)(2)(ii)(II).
2 l'lant llatriers i. ave been consolidated into a single design basis document. Included in this document is a list of the barrier drawings which clearly identify' the battiers which must maintain their integrity against air, water, pressure, weather, fire, or a combination thereof. Itesponsibility for the these barriers has been clearly assigned.
3.
North Atlantic completed a comprehensive reevaluation of plant design features relative to tornado design criteria. This reevaluation verified that tornado design criteria are met by the existing plant design with the exception of the six doors.
These doors have been verified to be capable of withstanding the worst case site specific tornado or the affected plant areas are capable of withstanding the corresponding depressurization.
4.
North Atlantic confirmed the tornado barrier envelope by a thorough inspection of the existing plant barrier drawings with subsequent confirmation by plant walkdowns.
5.
North Atlantic has revlSed the UFSAit to include the site speelfic tornado data.
lene Term Actions 1.
In order to standardire design requirementr, North Atlantle will implement a design change for the two doors (EF 400 and P-900) of at least !.5 psid.
This design change is expected to be implemented by May 51, 1993.
2.
Independent of the above events, North Atlantic has been developing a new procedure which will enhance the corrective action process at Seabrook Station with the intent of consolidating deficiency reporting methods and standardizing the problem evaluation and resolution process. This procedure, which will address sequences of eventa such at those described in Enclosure (1); is expected to be implemented by J une 30,1993.
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This is the first event of this type at Seabrook Station.
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