Text

Discusses Similarities & Differences in Design Between Chernobyl & Nuclear Power Plants Licensed to Operate in Us, Including BWRs Such as Perry Plant,In Response to to Senator J Glenn
	ML20212M592
Person / Time
Site:	Perry
Issue date:	08/22/1986
From:	Harold Denton; Office of Nuclear Reactor Regulation
To:	Michael Gibson; AFFILIATION NOT ASSIGNED
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ML20212M594	List: ML20212M592; ML20212M606;
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	NUDOCS 8608260407
	Download: ML20212M592 (7)
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Cestsiel:4Hes- PDR AUG 2 2 W HDenton/RVollmer PPAS R9ernero Mossburg (2024)

RWHouston Brandenburg (2024)'

BSheron EDO R/F

'Ms. Mary Gibson FMiraglia RHouston R/F 2817 Hampshire Rd. oc4 Cleveland Heights, Ohio 44118 sc e/

i

Dear Ms. Gibson:

i Your letter dated July 24, 1986 to Senator John Glenn has been referred to me for response.

f We are aware of and studying both similarities and differences in design

between Chernobyl and nuclear power plants licensed to operate in the i -the United States, including boiling water reactors of which Perry is one

{ example. Although we do not yet have a full explanation of the Chernobyl accident from the Soviets, information available to us at this time indicates i

that Chernobyl did not have a full containment system surrounding'the reactor

core itself although it appears to have been designed to withstand piping failures in some parts of the plant and did employ a pool of water directly below the reactor. Following the international meeting in Vienna, Austria

during the week of August 25, 1986 at which we expect to learn more details

of the Chernobyl accident and the design and operating features of this plant, l we will be preparing a complete report on the accident and a subsequent report l addressing implications for licensing and regulations in the United States.

! With respect to the Mark III containment design as at Perry, its configuration

, and design basis are such that it meets the Commission's requirements and with

! substantial safety margin with respect to its ability to withstand internal

pressure from a very large pipe break in the primary system. By pass leakage

refers to potential pathways for. escape of airborne material including steam, without passing through the suppression pool. The safety concern for excessive by pass of the suppression pool is that the pool also acts as a filter, to

> remove significant quantities of radioactive material that might be present

! under certain accident conditions, and by pass could allow a more direct pathway to the atmosphere.

I

! As to the matter of hydrogen releases, the Perry plant, like all the Mark III j designs, employs a hydrogen control system with igniters that can be activated i at low hydrogen concentrations to assure burning of the hydrogen well below l

levels that would produce a detonation.

You refer in your letter to the accident at Chernobyl occurring "during a

. shutdown procedure," and that " air was allowed into the plant during the

- shutdown procedure in order to save time -- ." Our present information is

-that the operating personnel at Chernobyl were attempting to conduct a unique test with the reactor at relatively low power and that this test had nothing to do with routine shutdown procedures. In addition we have no information t that would indicate that Chernobyl operating personnel allowed air into any M .

part of the plant where it would not normally be present. Your statement that "American plants consistently use this same procedure for the same reasons" [1 4)/ y[4

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appears to be a reference to the practice authorized by the NRC of deinerting Mark I and Mark II containments beginning 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months prior to reaching cold shutdown in preparation for a plant outage where personnel access to con-tainment is required. A similar 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period is permitted on plant restart before full compliance with the relevant Technical Specifications on the inert atmosphere is required. These periods of deinerting and reinerting represent only a very small fraction of the operating time and are judged not to represent a significant risk.

Your letter also referred to an article in " Nucleus" regarding the Davis-Besse plant which has a Babcock and Wilcox reactor. You indicated that according to the article, the Davis-Besse plant is still under operation without safety modifications in place as specified by the NRC after the Three Mile Island (TMI) partial meltdown in 1979. Following the Three Mile Island Unit 2 accident, the NRC issued post-TMI requirements for all licensees of operating plants and applicants for operating licenses and holders of construction permits. The Toledo Edison Company, the licensee for the Davis-Besse plant, has completed 86% of thest pest-TMI requirements and is scheduled to complete the remainder by the end of 1987.

Your letter also refers to the event that occurred at the Davis-Besse plant in June 1985. The NRC's Incident Investigative Team concluded that the root cause of this event was "the licensee's lack of attention to detail in the care of plant equipment". The Davis-Besse plant has been shutdown since this event and it will not restart until the NRC is satisfied that the necessary work has been completed.

The NRC is concerned that even though the utilities that have B&W plants have made a significant number of improvements in their plants since the TMI accident, the number and complexity of events in the B&W plants has not decreased as expected. As a result, the NRC staff has initiated a reassessment of the B&W plants. This activity will include an assessment of the thermal-hydraulic design, instrumentation, control and power supplies along with a review of operating experience and operator training and response. The NRC believes that the B&W reactors can safely continue to operate while the NRC reassesses the B&W plant design requirements.

Finally you indicate a concern for the safe operation of plants under conditions of drought. Each operating license has conditions on the availability of an adequate supply of water to assure the ability to safely shutdown and maintain the plant in a safe shutdown condition. A severe drought may, however, limit some plants' ability to continue operation at full power.

Sincerely, Original Signed By:

o R.((nton, Director Office of Nuclear Reactor Regulation cc: Senator John Glenn

See Previous Concurrence bbR/BWR* bbR/bSR0* bR/BWR* bD bR OFC R PWRL B*

f

! NAME RWHouston BSheron FMiraglia RBernero R/ol'lmer HRDenton DATE 8/ 19 /86 8/ /86 8/ 20 /86 8/ 20 /86 8/ /86 8/ /86

appears to be a reference to the practice authorized by,the NRC of deinerting Mark I and Mark II containments beginning 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months prior to reaching cold shutdown in preparation for a plant outage where personnel access to con-tainment is required. A similar 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period is permitted on plant restart before full compliance with the relevant Technical Specifications on the inert atmosphere is required. These periods of deinerting and reinerting represent only a very small fraction of the operating time and are judged not to represent a significant risk.

Your letter also referred to an article in " Nucleus" regarding the Davis-Besse plant which has a Babcock and Wilcox reactor. You indicated that according to the article, the Davis-Besse plant is still under operation without safety modifications in place as specified by the NRC after the Three Mile Island (TMI) partial meltdown in 1979. Following the Three Mile Island Unit 2 accident, the NRC issued post-TMI requirements for all licensees of operating plants and applicants for operating licenses and holders of construction permits. The Toledo Edison Company, the licensee for the Davis-Besse plant, has completed almost all of these post-TMI requirements.

Your letter also refers to the event that occurred at the Davis-Besse plant in June 1985. The NRC's Incident Investigative Team concluded that the root cause of this event was "the licensee's lack of attention to detail in the care of plant equipment". The Davis-Besse plant has been shutdown since this event and it will not restart until the NRC is satisfied that the necessary work has been completed.

The NRC is concerned that even though the utilities that have B&W plants have made a significant number of improvements in their plants since the TMI 1 accident, the number and complexity of events in the B&W plants has not i decreased as expected. As a result, the NRC staff has initiated a reassessment of the B&W plants. This activity wi,11 include an assessment of the thermal-hydraulic design, instrumentation, control and power supplies along with a review of operating experience and operator training and response. The NRC believes that the B&W reactors can safely continue to operate while the NRC reassesses the B&W plant design requirements.

Finally you indicate a concern for the safe operation of plants under conditions of drought. Each operating license has conditions on the availability of an ade'quate supply of water to assure the ability to safely shutdown and maintaip'the plant in a safe shutdown condition. A severe drought may, however, limit some plants' ability to continue operation at full power.

,/ Sincerely, l

/

, Harold R. Denton, Director

/ Office of Nuclear Reactor Regulation.

cc: Senator John Glenn No

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555

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Ms. Mary Gibson 2817 Hampshire Rd.

Cleveland Heights, Ohio 44118

Dear Ms. Gibson:

A Your letter dated July 24, 1986 to Senator John Glenn has been referred to me for response.

We at the NRC are very much aware of both similarities and differences in design between Chernobyl and nuclear power plants licensed to operate in the United States, particularly boiling water reactors of which Perry is one example. Although we do not yet have a full explanation of the Chernobyl accident from the Soviets, information available to us at this t;me indicates that Chernobyl did not have a full containment system surrounding the reactor core itself although it appears to have been designed to withstand piping failures in some parts of the plant and did employ a W4555Fpool of water directly below the reactor. Following the international meeting in Vienna, Austria during the week of August 25, 1986 at which we expect to learn more details of-the Chernobyl accident, we will be preparing a complete report on the accident and a subsequent report addressing implications for licensing and regulations in the United States.

With respect to the Mark III containment design as at Perry, its configuration and design basis are such that it meets the Commission's requirements and with substantial safety margin with respect to its ability to withstand internal pressure from a very large pipe break in the primary system. By pass leakage refers to potential pathways for escape of airborne material including steam, without passing through the suppression pool. The safety concern for excessive by pass of the suppression pool is that the latter also acts as a filter to remove significant quantities of radioactive material that might be present under certain accident conditions, thereby allowing a more direct pathway to the atmosphere.

As to the matter of hydrogen releases, the Perry plant3 11ke all the Mark III )(

designs, employs a hydrogen control system with igniters that can be activated at low hydrogen concentrations to assure burning of the hydrogen well below levels that would produce a detonation.

- You refer in your letter to the accident at Chernobyl occurring "during a shutdown procedure," and that " air was allowed into the plant during the

, shutdown procedure in order to save time -- ." Our present information is i that the operating personnel at Chernobyl were attempting to conduct a unique test with the reactor at relatively low power and that this test had nothing i to do with routine shutdown procedures. In addition we have no information that would indicate that Chernobyl operating personnel allowed air into any part of the plant where it would not normally be present. Your statement that "American plants consistently use this same procedure for the same reasons" l

{

o i .-

[s pt #

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f< bY%g kF -(

appears to be a reference to the practice authorized by the C of deinerting h / d)

Mark I and Mark II containments beginning 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months prior reaching cold p, y shutdown in preparation for a plant outage where person 1 access to con-tainment is required. A similar 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period is p itted on plant restart {p before full compliance with the relevant Technical ecifications on the inert atmosphere is required. These periods of deinert' g and reinerting represent only a very small fraction of the operating tim and are judged not to represent a significant risk.

Your letter also referred to an article in ' ucleus" eegarding the Davis-Besse plant which has a Babcock and Wilco reactor. You indicated that according to the article, the Davis-Bess plant is still under operation without safety modifications in place a specified by the NRC after the Three Mile Island (TMI) partial meltd n in 1979. Following the Three Mile Island Unit 2 accident, the NRC issu post-TMI requirements for all licensees of operating plants and applicants or operating licenses and holders of construction permits. The Toledo dison Company, the licensee for the Davis-Besse plant, has completed almostfall of these post-TMI requirements.

iour letter also refers to the event that occurred at the Davis-Besse plant in June 1985. The NRC's Incident Investigative Team concluded that the root cause of this event was "the licensee's lack of attention to detail in the care of plant equipment". The Davis-Besse plant has been shutdown since this event and it will not restart until the NRC is satisfied that the necessary work has been completed. gg g j g /(* g g4 [

The NRC is concerned t even though the utilities that have B&W plants have made a signif nt number of improvements in their plants since the TMI accident, the --M =d complexity of events in the B&W plants has not decreased as expected. As a result, the NRC staff has initiated a reassessment of the B&W plants. This activity will include an assessment of the thermal-hydraulic design, instrumentation, control and power supplies along with a review of operating experience and operator training and response. The NRC believes that the B&W reactors can safely continue to operate while the NRC reassesses the B&W plant design requirements.

Finally you indicate a concern for the safe operation of plants under conditions of drought. Each operating license has conditions on the availability of an adequate supply of water to assure the ability to safely shutdown and maintain the plant in a safe shutdown condition. A severe [D drought may, however, limit some plants' ability to continue operation at full power.

gh p

Sincerely, f

Harold R. Denton, Director Office of Nuclear Reactor Regulation f' cc: Senator John Glenn 7 gO

appears to be a reference to the practice authorized by the NRC of deinerting Mark I and Mark II containments beginning 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months prior to reaching cold shutdown in p~ ration for a plant outage where personnel access to con-tainment is ree ed. A similar 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months period is permitted on plant restart before full cc- .ance with the relevant Technical Specifications on the inert atmosphere is quired. These periods of deinerting and reinerting represent only a very small fraction of the operating time and are judged not to represent a significant risk.

Your letter also referred to an article in " Nucleus" regarding the Davis-Besse plant which has a Babcock and Wilcox reactor. You indicated that according to the article, the Davis-Besse plant is still under operation without safety modifications in place as specified by the NRC after the Three Mile Island (TMI) partial meltdown in 1979. Following the Three Mile Island Unit 2 accident, the NRC issued post-TMI requirements for all licensees of operating pisnts and applicants for operating licenses and holders of construction permits. The Toledo Edison Company, the licensee for the Davis-Besse piant, has completed almost all of these post-TMI requirements.

Your letter also refers to the event that occurred at the Davis-Besse plant in June 1985. The NRC's Incident Investigative Team concluded that the root cause of this esent was "the licensee's lack of attention to detail in the care of plant equipment". The Davis-Besse plant has been shutdown since this event and it will not restart until the NRC is satisfied that the necessary work has been completed.

The NRC is concerned that even though the utilities that have B&W plants have made a significant number of improvements in their plants since the TMI accident, the number and complexity of events in the B&W plants has not decreased as expected. As a result, the NRC staff has initiated a reassessment of the B&W plants. This activity will include an assessment of the thermal-hydraulic design, instrumentation, control and power supplies along with a review of operating experience and operator training and response. The NRC believes that the B&W reactors can safely continue to operate while the NRC reassesses the B&W plant design requirements.

Finally you indicate a concern for the safe operation of plants under conditions of drought. Each operating license has conditions on the availability of an adequate supply of water to assure the ability to safely shutdown and maintain the plant in a safe shutdown condition. A severe drought may, however, limit some plants' ability to continue operation at full power.

Sincerely, fHaroldR.Denton, Director jp Office of Nuclear Reactor Regulation cc: Senator John Glenn .

t

Ws4 ------------------------------------------------

0FC DDIR/BWR DDI DSR0 DIR/PWRL-B DIR/BWR DDIR/NRR DIR/NRR i

NAME RWHouston BSlQrph FMiraglia RBernero RVollmer HRDenton DATE 8/ /86 8/ /86 8/ /86 8/ /86 8/ /86 8/ /86

ML20212M592

Text

Dear Ms. Gibson:

Dear Ms. Gibson:

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