ML20137S045
| ML20137S045 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/07/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20137S001 | List: |
| References | |
| NUDOCS 8602130560 | |
| Download: ML20137S045 (4) | |
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SAFETY EVALUATION REPORT FORT ST. VRAIN - CONFIRMATORf ACTION 3 ENVIRONMENTAL QUALIFICATION FOR HIGH ENERGY LINE BREAKS. SCHEDULE EXTENSION We have reviewed the licensee's submittal of December 10, 1985 regarding environmental qualification of equipment for postulated high energy line breaks in support of a schedule extension Attachment 1. Confimatory Action 3 as follows:
Confimatory Action 3:
" Provide high energy line break temperature profiles for accidents from l
reactor power levels up to 35 percent demonstrating access to plant areas where operators are required to take the necessary manual actions by specified times. Identify all assumptions made regarding operator response times to the high energy line break. Credit will be taken only for qualified systems. An evaluation will be made for the need for SLRDIS for 35 percent power operation."
4 In response, in this portion of the submittal, the licensee analyzed a total of
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six high energy line breaks. The licensee has determined that the break locations resulting in the most severe environments are in the hot reheat line in the turbine building and the reactor building. The licensee analyzed three cases in each building - a full offset line break, a medium line break, and a small line break. The pertinent results for these breaks are shown in Table 1.
l There are two major limits of concern for qualification of equipment to harsh environments: 1)themaximumtemperature,and(2)thetemperatureatsometime (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />) after the break. The licensee has utilized an analytical model (CONTEMPT-G) to generate time / temperature profiles for the above pipe breaks.
The licensee has stipulated that the resulting maximum temperatures will cause reactor protection, control, and power systems to fail since none are qualified for harsh environments. However, the licensee assumes that existing plant protective and control systems act as designed for up to 20 seconds after pipe break, and have therefore performed their safety function pri6r to failure. We find this hypothesis acceptable in view of the langth of time requiredtoattainthemaximumambienttemperatures(aminimumofapproximately 8602130560 060207 PDR ADOCK 05000267 P
=
. 18 minutes). Any protective, control, or power circuits in the area of the postulated pipe breaks would see lower temperatures than the maximum shown and therefore, the circuits cited should be available for an operational time of 20 seconds. We conclude that the licensee has-identified appropriate time / temp-erature profiles for the postulated line breaks, and electrical equipment of
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concern will operate properly prior to failure. We further conclude that the maximum and 12-hour ambient temperatures detemined by the licensee are appropriate.
i In addition, we have reviewed the line break results in order to confirm the maximum temperatures assumed by the licensee in response to Confirmatory Action 12 related to the requirement that operators enter buildings 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> after a line break. The licensee notes that ambient temperatures of 180*F or less exist at four hours and 135'F or less after 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> when considering the entrance of operators into the areas of concern. By observation of the data, we see maximum temperatures of 180*F at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and a maximum temperature of140* Fat 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> (inHRH-15). Extrapolating the results of HRH-15 from 140'F at 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> would result in a temperature reduction to 135'F in the 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> period thereafter to 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />. Therefore, we conclude that the licensee's assumed maximum 4-hour and 15-hour temperatures are appropriate.
We have also reviewed the licensees assumed initial operator actions to assure a safe shutdown following the postulated line breaks. For line breaks HRH-9 and -10 the licensee assumes that the auxiliary boiler is manually tripped at 11 minutes and is ramped to zero flow in 1/2 hour together with manual trip of the electric boiler. feed pumps at 12 minutes after break initiation.
For line breaks HRH-13 and -14, the licensee assumes manual scram of the reactor at 11 minutes after break initiation followed by manual trip of the auxiliary boiler (with 30 minute ramp to zero flow thereafter) and electric boiler feed pumps at 14 minutes. For line breaks HRH-15 and -16, the licensee assumes manual scram of the reactor at 1-hour, followed by manual trip of the auxiliary boiler and electric boiler feed pumps at 64 minutes. We conclude that the above proposed limited operator actions and times for these actirms are masonable.
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In conclusion, we find the following to be acceptable with regard to Confimatory Action 3:
(1) The protective, control, and power circuitry will operate satisfactorily in t'he first 2 seconds after a hot reheat line bre' k.
a (2) The indicated time / temperature profiles and maximum 4-hour and 15-hour temperatures of 180*F and 135'F respectively are appropriate.
(3) The limited manual operator actions and operation times are reasonable.
We therefore consider that Confirmatory Action 3 has been satisfactorily resolved.
Reviewer:
N. Wagner i
G O
o O
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TABLE 1 Data From Fort St. Vrain Hot Reheat (HRH) Line Break Analyses HRH HRH HRH HRH HRH HRH Break Analysis No.
9 10 13' 14 15 16 Break Location TB RB TB RB RB Break Type F0 F0 MB MB SB SB
.~
Maximum Ambient 240 265 245 275 220 240 Temperature *F*
Time To Attain 20 20 18 18
, 70 70 Ma.:imum Temperature Minutes
- Ambient Temperature 165 160 165 155 180 180 at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, 'F Ambient Temperature 113 121 128 118 140 126 at 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. *F Reactor Scram / Time Auto /
Auto /
Manual /
Manual /
Manual /
Manual /
10 see 10 sec 11 min.
11 min.
I hour 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Notes:
TB - Turbine Building RB - Reactor Building F0 - Full Offset MB - Medium Break SB - Small Break
- Estimated From Graph