ML19257C439
| ML19257C439 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/16/1980 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Atomic Safety and Licensing Board Panel |
| Shared Package | |
| ML19257C422 | List: |
| References | |
| NUDOCS 8001290128 | |
| Download: ML19257C439 (15) | |
Text
e January 16, 1980 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
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SACRAMENTO MUNICIPAL UTILITY DISTRICT
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Docket No. 50-312
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(Rancho Seco Nuclear Generating Station) )
LICENSEE'S ANSWERS TO CALIFORNIA ENERGY COMMISSION REQUESTS FOR ADMISSIONS TO SACRAMENTO MUNICIPAL UTILITY DISTRICT 1.
REQUEST:
That Rancho Seco and the Three Mile Island Unit-2 facility ("TMI-2") are both Babcock and Wilcox reactors of the same basic design.
ANSWER:
Licensee admits that the Rancho Seco and TMI-2 facilities include reactors designed by Babcock and Wilcox, and th:t the reactors themselves (i.e.,
fuel, moderator and controls) are of the same basic design.
2.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the capacity of the feedwater side of the steam generators, despite the modifications made to Rancho Seco after the TMI-2 accident.
ANSWER:
Admitted.
3.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the elevation of the steam generators relative to the reactor vessel, despite the modifications made to Rancho Seco after the TMI-2 accident.
ANSWER:
Admitted.
h 832 327
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4.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the capacity of the pressurizer, despite the modifications made to Rancho Seco after the TMI-2 accident.
ANSWER:
Admitted.
5.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical witn respect to the design of the pressure operated relief valve, despite the modifications made to Rancho Seco after the TMI-2 accident.
ANSWER:
Admitted.
Licensee further states, however, that as a result of modifications made to Rancho Seco after the TMI-2 accident the setpoint for the power operated relief valve has been changed so that reactor trip on high primary system pres-sure occurs before the power operated relief valve is actuated.
6.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the emergency core cooling system, despite the modifications to Rancho Seco after the TMI-2 accident.
Ay,WER:
Licensee can neither truthfully admit nor deny the request.
The emergency core cooling systems for Rancho Seco and TMI-2 were designed by different architect / engineers.
Con-sequently, it is likely that tra systems are not identical.
Because Licensee has not performed a detailed comparison of these systems, it cannot truthfully state whether or not they are "substantially identical".
7.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the auxiliary feedwater system, despite the modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
Denied.
1832 528
8.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the primary cooling system, despite modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
Licensee can neither truthfully admit nor deny the request.
There are many aspects of the primary cooling system --
such as pumps, motors and instrumentation -- for which Licensee has not performed a detailed comparison between Rancho Seco and TMI-2.
Therefore, Licensee cannot truthfully state whether or not they are "substantially identical".
9.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the secondary feedwater system, despite the modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
Licensee can neither truthfully admit nor deny this request.
The secondary feedwater systems for Rancho Seco and TMI-2 were designed by different architect / engineers.
Conse-quently, it is likely that the systems are not identical.
Because Licensee has not performed a detailed comparison of these systems it cannot truthfully state whether or not they are "substantially identical".
10.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the capacity of the reactor coolan-drain tanks, despite the modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
- Denied, 11.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the in'.egrated control system, despite the modificatiens to Rancho Seco after the TMI-2 accident.
ANSWER:
Licensee can neither truthfully admit nor deny this request.
The power supply portion of the integrated co,ntrol i832 329 systems for Rancho Seco and TMI-2 was designed by different architect / engineers.
Consequently, that portion of the systems is not likely to be identical.
Because Licensee has not performed a detailed comparison of that and other portions of these systems, it cannot truthfully state whether or not they are "substantially identical".
12.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the nuclear steam supply system, despite the modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
Licensee can neither truthfully admit nor deny this request.
The nuclear steam supply system is a large and complex system containing many other systems such as the primary cooling system and integrated control system.
For the same reasons stated in the answers to Requests 8 and 11, Licensee cannot truthfully state whether or not they are "substantially identical".
13.
REQUEST:
That Rancho Seco and TMI-2 are substantially identical with respect to the design of the containment structure, despite the modifications to Rancho Seco after the TMI-2 accident.
ANSWER:
Licensee can neither truthfully admit nor deny this request.
The containment structures for Rancho Seco and TMI-2 were designed by different architect / engineers.
Seismic design requirements for the two structures are different and, conse-quently, it is likely that the structures are not identical.
Because Licensee has not performed a detailed comparison.of these structures, it cannot truthfully state whether or not they are "substantially identical".
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14. REQUEST: That neither Rancho Seco nor TMI-2 provide direct indication of reactor coolant inventory apart from pressurizer inventory. ANSWER: Licensee admits that pressurizer level provides the most direct indication of reactor coolant inventory under subcooled conditions with no non-condensible gases.
- Pressure, however, also provides indication of the point at which inventory is insufficient to maintain subcooling.
15. REQUEST: That Rancho Seco has no method of venting gases from the primary system aside from the pressure operated relief valve located in the pressurizer. ANSWER: Denied. 16. REQUEST: That Rancho Seco has no on-site hydrogen recombiner. ANSWER: Admitted. 17. REQUEST: That had Rancho Seco on March 28, 1979, experienced the same system failures and operator responses as TMI-2 experienced on that date, it would have experienced an accident similar to that of TMI-2. ANSWER: Denied. 18. REQUEST: That the failure of the pressure operated relief valve to close was a significant contributing factor to the accident at TMI-2. ?l 3;iER: Denied. 19. REQUEST: That the small capacity of the pressurizer was a contributing factor to the accident at TMI-2. ANSWER: Denied. 1832 331
20. REQUEST: That the elevation of the steam generator relative to the reactor vessel was a significant contributing factor to the accident at TMI-2. ANSWER: Denied. 21. REQUEST: That voiding in the primary system resulted in an inability to achieve natural circulation at TMI-2 and was a significant contributing factor to the accident at TMI-2. ANSWER: Denied. 22. REQUEST: That the small capacity of the feedwater side of the steam generator was a significant contributing factor to the accident at TMI-2. ANSWER: Denied. 23. REQUEST: That the lack of direct indication of reactor coolant inventory apart from pressurizer inventory was a significant contributing factor to the accident at TMI-2. ANSWER: Denied. 24. REQUEST: That the ability to vent gases from high points in the primary system would have facilitated natural circulation cooling at TMI-2 and thereby may have helped mitigate the accident. ANSWER: Denied. 25. REQUEST: That the failure of the operators at TMI-2 to maintain operation of the high pressure injection system in the early stages of the accident was a significant contributing factor to the accident at TMI-2. ANSWER: Admitted. See: IE Bulletin 79-05A; NUREG-0560 at 4.4.2; Finding A.4, Report of the President's Commission on the Accident at Tnree Mile Island. 1832 332 ' 26. REQUEST: That the failure of the operators at TMI-2 to maintain operation of the primary coolant pumps in the early stages of the accident was a significant contributing factor to the accident at TMI-2. ANSWER: Admitted. See: IE Bulletin 79-05A; NUREG-0560 at 4.4.2. Licensee further states that at the time the reactor coolant pumps were tripped at TMI-2 the primary system was in a significantly degraded condition (high void f raction). Trip-ping of the pumps under these circumstances significantly contributed to the accident. 27. REQUEST. That the inability of the reactor coolant drain tanks
- o contain all the coolant vented through the pressure operated relief valve exacerbated the accident at TMI-2 and led to offsite releases of radioactivity.
ANSWER: Denied. 28. JEQUEST: That the failure of operators at TMI-2 to recognize or appreciate the significance of indications that coolant was being discharged to the reactor coolant drain tanks was a significant contributing factor to the accident at TMI-2. ANSWER: Denied. 29. REQUEST: That the inability of the operators at TMI-2 to achieve core cooling by using the decay heat removal system exacerbated the TMI-2 accident. ANSWER: Denied. 30. REQUEST: That the lack of sufficient radiation monitoring equipment at TMI-2 and knowledge of plant systems and areas likely to contain radioactivity limited the ability of operators to respond to the accident. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee does not have adequate knowledge of the radiation monitoring equipment at TMI-2 and of the operators' i832 533 knowledge of plant systems in areas likely to contain radio-activity to truthfully state whether or not they limited the ability of operators to respond to the accident. ~ 31. REQUEST: That the lack of a hydrogen recombiner at TMI-2 may have resulted in a significant buildup of hydrogen leading to an explosion sufficient to exceed the containment design. ANSWER: Denied. I 32. REQUEST: That a second pressure operated relief valve on the pressurizer may have aided operators at TMI-2 in responding to the accident. ANSWER: Denied. 33. REQUEST: That Rancho Seco is operated with leakage through the pressure operated relief valve and/or through safety valves. ANSWER: Admitted. Licensee further states, however, that Rancho Seco has operated successfully with this leakage, and that the leakage has always been within allowable licensed limits. 34. REQUEST: That the failure of the operators at TMI-2 to recog-nize and understand the degraded condition of the reactor and the primary system was a significant contributing factor to the accident at TMI-2. ANSWER: Licensee admits that the operators' failure to recognize the degraded conditions of low pressure and high temperature in the reactor coolant system and the failure to take action to restore these parameters to normal levels was a significant contributing factor to the accident at TMI-2. ~. I832 534 35. REQUEST: That procedures instituted at Rancho Seco since TMI-2 direct operators to rely upon natural circulation cooling for at least 20 minutes following a feedwater transient which activates the HPI. ANSWER: Denied. 36. REQUEST: That natural circulation cooling is unreliable once significant voiding occurs in the primary system. ANSWER: Admitted. Licensee further states, however, that for non-LOCA situations natural circulation cooling can be restored if it has been degraded by vcid formation. 37. REQUEST: That forced circulation cooling is unreliaole once significant voiding or loss of pressure occurs in the primary system. ANSWER: Denied. 38. REQUEST: That forced circulation ccoling is unavailable at Rancho Seco where there is a loss of off-site power together with a turbine trip. ANSWER: Denied. 39. REQUEST: That a significant number of operators at Rancho Seco exhibited an insufficient understanding of natural circulation cooling when first tested by the NRC in relation to SMUD's compliance with the NRC's May 7 shutdown order. ANSWER: Licensee can neither truthfully hdmit nor deny this request. Quantitative data on the number of operators the NRC initially felt were adequately retrained following the TMI-2 accident were not made available to SMUD by the NRC. Licensee further states that the NRC staff report, " Evaluation of Licen-see's Compliance with the NRC order dated May 7, 1979", dated June 27, 1979, states that there was a deficiency in understand-ing " verification of natural circulation" rather than an i832 335 insufficient understanding of " natural circulation cooling." 40. REQUEST: That where both forced and natural circulation cool-ing are unavailable because of voiding in the primary system, there is no means of reasonably assuring adequate core cooling for extended time periods at Rancho Seco. ANSWER: Denied. 41. REQUEST: That where both forced and natural circulation cool-ing are unavailable, there is no means to place the reactor core in a cold shutdown without using the decay heat removal system. ANSWER: Admitted. 42. REQUEST: That where both forced and natural circulation cooling are unavailable because of voiding in the primary system, the only means of core cooling for extended time periods is to rely upon boiling and venting from the reactor Core. ANSWER: Denied. 43. REQUEST: That boiling and venting in the primary system may lead to core damage if used for extended time periods. ANSWER: Denied. 44. REQUEST: That boiling and venting cooling has never been relied upon to assure adequate core cooling in pressurized water reactors. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any such reliance. 45. REQUEST: That boiling and venting cooling was not considered as a reliable method of assuring adequate core cooling during the licensing of Rancho Seco. ANSWER: Licensee can neither truthfully admit nor deny this 1832 336.
request. Licensee did not consider this method of core cooling as either reliable or unreliable and has no knowledge of considerations by others during the licensing of Rancho Seco. 46. REQUEST: That boil'.ng and venting cooling in pressurized water reactors is an untested theory that has not been scientifica1)/ demonstrated. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any testing or demonstration of boiling or venting cooling in pressurized water reactors. 47. REQUEST: That boiling and venting cooling has never been successfully achieved in a pressurized water reactor like Rancho Seco. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any attempt to achieve boiling and venting cooling in a pressurized water reactor like Rancho Seco. 48. REQUEST: That natural condensation cooling may be unreliable where significant amounts of non-condensible gases are present in the primary system. ANSWER: Admitted. 49. REQUEST: That natural condensation cooling has never been relied upon to assure adequate core cooling in pressurized water reactors. ANSWER. Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any such reliance. 50. REQUEST: That natural condensation cooling was not considered ' [r7' If]
daring the licensing of Ranche Seco as a method of core cooling. ANSWER: Denied. 51. REQUEST: That natural condensation cooling in pred;urized water reactors is an untested theory,that has not yet been scientifically demonstrated. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any tescing or demonstration of natural condensation cooling in pressurized water reactors. 52. REQUEST: That natural condensation cooling has never been successfully achieved in a pressurized water reactor like Rancho Seco. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee is not aware, however, of any attempt to achieve natural condensation cooling in a pressurized water reactor like Rancho Seco. 53. REQUEST: That the high pressure injection system ca;.not maintain reactor coolant inventory if certain size small breaks occur and the reactor coolant pumps are operating. ANSWER: Denied. 54. REQUEST: That procedures now in effect at Rancho Seco direct operators to manually raise inventory on the feedwater side of the steam generator in the event of a feedwater transient. A:ISWER: Denied. )h 55. REQUEST. That without the action described in requested admission number 54 above, natural condensation cooling cannot be achieved at Rancho Seco. ANSWER: Licensee can neither truthfully admit nor deny this request. Licensee has not analyzed the steam generator level whicn might be required to achieve natural condensation cooling at Rancho Seco. 56. REQUEST: That procedures now in effect at Rancho Seco direct operators to maintain operation of the high pressure injection system in the case of a small break LOCA. ANSWER: Admitted. Licensee further states, however, that these procedures direct operators to maintain operation of high pressure injaction until 50 degrees subcooling is achieved. 57. REQUEST: That procedures now in effect at Rancho Seco allow operators to cease operation of the high pressure injection system after twenty minutes in the event of a feedwater tran-sient accompanied by a 50-degree F. margin above saturation. ANSWER: Denied. 58. REQUEST: That the Rancho Seco high pressure injection system will automatically be activated during many feedwater tran-sients not accompanied by a small break LOCA. ANSWER: Denied. 59. REQUEST: That if operators at Rancho Seco mistakenly shut off the high pressure injection system for any significant period of time during a small break LOCA, voiding would occur in the primary system. ANSWER: Admitted. Licensee states that shutting off high pressure injection during a small break LOCA would cause additional voiding over that which might otherwise occur. 18.,s5L s S- (1 f 60. REQUEST: That as a result of procedures now in effect at Rancho Seco, tne high pressure injection system will operate more often than was anticipated when Rancho Seco was licensed. ANSWER: Admitted. Licensee further states, however, that the increased operation of the high pressure injection system over that anticipated when Rancho Seco was licensed is not a result of automatic initiation conditions nor a result of procedure changes since the Three Mile Island accident. These procedures are the result of kncwledge gained about plant behavior early in the operating life of Rancho Seco. 61. REQUEST: That as a result of modifications to Rancho Seco resulting from the NRC's May 7 order, the facility will experience a significantly greater number of reactor trips than was anticipated when Rancho Seco was licensed. ANSWER: Licensee can neither truthfully admit nor deny this request. The addition of a reactor trip on turbine trip will result in an increased number of reactor trips; however, it is not possible to quantify the additional number of reactor trips since one cannot determine the number of turbine trips that will occur in the future, or how many of those would have resulted in a reactor trip without the modification. 62. REQUEST:- That operators at Rancho Seco have no direct indica-tion of all'possible small break LOCA's and must deduce some of them from indications of resulting events such as loss of pressure or inventory in the primary system. ANSWER: Admitted. 63. REQUEST: Tnat Rancho Seco has no overpressurization protection system (such as controlled, filtered venting f rom containment) that would micigate the consequences of containment failure. 1832 .540 ANSWER: Admitted. Licensee further states that it understands the purpose of over-pressurization protection systems to be to prevent containment failure and not to mitigate the consequences of an already failed containment. 64. REQUEST: That the design of the Rancho Seco control room is such that operators must sometimes control the facility based upon indications not located within a functionally useful distance of the rela ted controls without the assistance of a second operator. ANSWER: Denied. 65. REQUEST: That Rancho Seco has never used natural circulation core cooling. ANSWER: Admitted. Licensee states, however, that natural circulation core cooling has been demonstrated at facilities with substantially identical elevations of the steam generators relative to the reactor vessel. Respectfully submitted, pohn J(/Mattimoe Assistant General Manager and Chief Engineer Sacramento Municipal Utility District Sworn to and subscribed before me this day of January, 1980 Notary Public h 0FFICIAL SEAL l p PATRICIA K. GEISLER l NOTARY PUBLIC CAUFCRNIA 3 FRINCIP AL OFFICE IN sAcawtNto couNiv l My Commission Expr-s teovember 22.1983 l ................................e , }}