ML20137S107
| ML20137S107 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/07/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20137S001 | List: |
| References | |
| NUDOCS 8602130574 | |
| Download: ML20137S107 (3) | |
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s SAFETY EVALUATION REPORT EQUIPMENT QUALIFICATION (EQ) EXTENSION OF THE NOVEMBER 30, 1985 DEADLINE FOR THE I
j FORT ST. VRAIN NUCLEAR l
GENERATING STATION l -:
The following evaluations concern Confirmatory Actions 9 and 12.
CONFIRMATORY ACTION 9:
Document the extent of PCRV damage expected during a liner cooldown from 35 percent power following a high energy line break.
The licensee has documented the damage expected to the PCRV on the basis of four possible scenarios.
In the worst of these scenarios, top head cover plagesfailandaportionoftheconcreteisexposedtotemp(ORNL).
eratures above-l 400 F.
These results have been reviewed by our contractor ORNL's l
l models and calculations predict similar results for PCRV damage. Although there are differences between these calculations, the staff concludes that these are minor, and the licensee's documentation of the extent of PCRV damage is acceptable. The consequences of this damage were found to be acceptable in Confirmatory Action 2.
l CONFIRMATORY ACTION 12:
If Fort St. Vrain operators will be required to take manual actions in environments whose temperatures exceed normal power plant operating temperatures to respond to high energy line breaks from 35 percent power, provide the NRC with information on the ability of operators to work in these higher temperature environments and the need for operators to utilize cool suits.
The licensee has calculated the temperatures in the plant following a high energy line break accident. The licensee has demonstrated, in ressonse to ConfirmatoryAction3,thatthetempgraturesinthereactorortur)ine buildingswillfglitolessthan180Fwithin4hoursaftertheaccidentand to less than 135 F within 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> after the accident.
Furthermore, the licensee has demonstrated, in Confirmatory Action 1, that initiation of the liner cooling system as late as 29.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the accident is acceptable in that, with the reactor pressurized, virtually no fuel damage will occur.
If access to the reactor building is possible at earlier times, Jhe liner cooling system can be started earlier. Potentially, the reactor can also be depressurized; however this is not a safe shutdown requirement at 35 percent power. Thus, for the purpose of evaluating Confirmatory Action 12, the staff only considered the requirement to have the liner cooling system operating at 29.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the accident.
0602130574 060207 ADOCKODOOgPj7 PDH e
Thelicenseestatesthatthgoperato5swillbeabletoaccessareaswith ambient temperatures of 135 F to 180 F with ecol suits (ice vests) and Scott air packs. The staff has chosen not to review operator access in this temperature range, because such access is not necessary to justify safe operation at 35 percent of full power.
After15hourg,thetemperatureintheareawhereaccessisrequiredwillbe less than 135 F.
Documented test data exist for the exposure of persons to heatstressconditionginthistemperaturerange(Reference 1). These tests were conducted at 131 F under laboratory conditions. The subjects walked on a treadmill to simulate the effects of exertion in a work situation. Their clothing for these tests included radiation protection garments, which significantly added to their heat stress load.
Data reported for these subjects showed that they were capable of working for 48 + 6 minutes without any cooling aids. With short frozen water garments, simitar to the cool suits proposed by the licensee, the same subjects could work for periods of 103 + 22 minutes. The criteria for determining acceptable work times were baseil on body temperature, heart rate, and the subjects' own perceptions of their general condition.
In order to restart the liner cooling system, the Fort St. Vrain operators wilfhavetoperformmanualactionsinapotentiallyhightemperature(upto 135 F) environment. The manual actions necessary to restart the liner cooling system are listed in Table 2. Attachment 4. of the licensee's submittal dated December 10, 1985.
The most severe scenario occurs when the high temperatures exist in the reactor building, where 11 actions must be taken to start one loop of the liner cooling system. There are an additional 7 optional actions that may be taken as part of this procedure. The licensee has conducted actual walkdowns of these actions with two-man teams of operators using Scott air packs.
Realistic post-accident conditions were simulated by having the plant lighting off and the operators using portable lighting. Under these conditions, establishing operation of the liner cooling system took 148 minutes.
Since the air packs must be changed about every 30 minutes, multiple entries by the operators would be required to complete the required operations.
Furthennore, the licensee has stated, in a submittal dated January 15, 1986, that the operators would work as trained two-man crews under these circumstances, to assure operator safety. This would enable one operator to provide portable lighting and other necessary assistance while the second operator takes the required actions. At least one additional trained crew would be available for relief and to perform actions in parallel, if necessary.
Since the crews would work for a maximum of only about 30 consecutive minutes before their air packs would be exhausted, they would never be exposed to the severe environment for an unacceptable duration. At approximately 30-minute intervals the operators would be relieved by a new crew, or would change to fresh air packs and ice vests, as needed to continue the liner cooling system restart procedure. Ac'ditional trained backup personnel would be available to supplement the operating crews to assure completion of the procedures within the time constraints, i
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If necessary, there will be adequate time to wait for further.cooldown before entering the high-temperature environment since initiation of the liner cooling system can be delayed until 29.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> with acceptable results.
Thus, the staff concludes that the licensee has provided sufficient information to demonstrate that the operators can work in the high temperature environments following a postulated high-energy break accident.
This information forms the basis for acceptability of initiating operator action at 15 or more hours after the accident for restarting the liner cooling system. This information also demonstrates that the cool suits to be used will aid the operators in performing these required tasks, by extending the time in which they can be safely exposed to the high-temperature environment.
Thus, the staff finds that Confirmatory Action 12 has been satisfied acceptably.
Reference:
1..
" Personal Cooling in Nuclear Power Stations," EPRI-NP-2868, March 1983. Electric Power Research Institute, Palo Alto, CA.
Reviewer:
K. Heitner Note:
ORNL Report is Enclosure 7 I
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