March 15th, 2011 – NUREG-0651- Torus (Suppression Chamber) Portion of the Mark I Containment

Author: No Comments Share:

From: Stevens, Gary
Sent: Tuesday, March 15, 2011 3:32 PM
To: Csontos, Aladar
Subject: The Torus (Suppression Chamber) Portion of the Mark I Containment
Attachments: image002.png; image006.png

Al:

Provided below is general description of the torus of a Mark I containment for an un-named BWR-4 plant.

Gary L. Stevens
Senior Materials Engineer
NRC/RES/DE/CIB
[email protected]
301-251-7569

Suppression Chamber (Torus)

  • The suppression chamber is in the general form of a torus and is constructed of 16 mitered cylindrical shell segments as shown in Figure 1.
  • The mitered cylinders which make up the torus have an inside diameter of 30′-8″, with a shell plate thickness of 1″.
  • The radius from the centerline of the drywell to the center of the torus at a section taken midway between the mitered joints is 56′-4″.
  • The suppression chamber shell is reinforced at each mitered joint and at the midpoint of each mitered cylinder by T-shaped ring beams.
  • The centerline of the ring beam at the mitered joint is offset 3-1/2″ in a plane parallel to the plane of the mitered joint.
  • The flange and cover plates of the mitered joint ring beams are rolled to a constant inside radius.
  • The mitered joint ring beam web depth varies around the circumference of the suppression chamber.
  • The mid-cylinder ring beams are of constant depth.
  • The components of the suppress ion chamber are shown in Figure 2.

Figure 1: PLAN VIEW OF CONTAINMENT

From: Stevens, Gary
Sent: Tuesday, March 15, 2011 2:40 PM
To: Csontos, Aladar
Subject: Mark I Containment
Attachments: NUREG-0661 Supplement 1 (SER for Mark I Containment Program).pdf; NUREG-0661 (SER for Mark I Containment Program).pdf

Al:

In response to your request, here is background on the BWR Mark I containment structure, which is the containment design for 5 of the 6 BWR units at the Fukushima-Daiichi site in Japan (Unit 1 = BWR-3 with Mark I, Units 2 – 5 = BWR-4 with Mark I, Unit 6 = BWR-5 with Mark II).

Please note that this was a very complex and significant issue, and I have only grazed the surface in this summary.

In the early to mid-1 970s, during testing for an Advanced Boiling Water Reactor (ABWR) containment system design (Mark III), suppression pool hydrodynamic loads were identified which had not been considered in the original design of the Mark I containment system.

To address this issue, a Mark I Owners Group was formed and the assessment was divided into a short-term and long-term program.

The results of the NRC staffs review of the Mark I Containment Short Term Program are described in NUREG-0408 (I have requested this report from the Library as it is not available electronically). NUREG-0661 and NUREG-0661 Supplement 1 (both attached) describe the results of the NRC staffs review of the generic Mark I Containment Long Term Program (LTP).

The LTP was conducted to provide a generic basis to define suppression pool hydrodynamic loads and the related structural acceptance criteria, such that a comprehensive reassessment of each Mark I containment system would be performed.

A series of experimental and analytical programs were conducted by the Mark I Owners Group to provide the necessary bases for the generic load definition and structural assessment techniques.

The generic methods proposed by the Mark I Owners Group, as modified by the NRC staffs requirements, will be used to perform plant-unique analyses, which will identify the plant modifications, if any, that will be needed to restore the originally intended margin of safety in the Mark I containment designs.

Note that all U.S. Mark I plants performed plant unique analyses, which are documented in Plant Unique Analysis Reports (PUARs) specific to each plant. Most of these analyses led to plant-specific modifications that were made to the Mark I containment structure at each plant.

This was the subject of significant litigation and settlement between several of the U.S. utilities and GE during the 1980s.

I have some other supporting reports, if needed.

Let me know if you need anything else.

Gary L. Stevens
Senior Materials Engineer
NRC/RES/DE/CIB
[email protected]
301-251-7569

NUREG-0651 was originally issued in July 1980 with four open items which have now been resolved. The four open items consisted of the downcomer oscillation load definition and the confirmatory analyses and test programs which were intended to iustify the adequacy of the load specification. The confirmatory efforts concern the assessment of compressible flow effects in the scaled pool swell tests and the confirmation of condensation oscillation load magnitude and global symmetry.

The staff has reviewed the improved downcomer condensation oscillation load definition provided by the Mark I Owners’ Group and find it acceptable. The staff has also reviewed the confirmatory experimental and analytical programs conducted by the Mark I Owners’ Group and have concluded that the adequacy of the various load specifications have been justified.

This Supplement No. 1 to NUREG-0661 therefore serves as the staff’s final resolution of Unresolved Safety Issue A-7.

ABSTRACT

When the NRC staff published “Safety Evaluation Report, Mark I Containment Long-Term Program” (NUREG-0661) in July 1980, four areas were identified
where the technical issues had not been fully resolved.

These were:
(1) specification for condensation oscillation loads acting on the downcomers,
(2) adequacy of the data base for specifying torus wall pressures during condensation oscillations,
(3) possibility of asymmetric torus loading during condensation oscillations, and
(4) effect of fluid compressibility in the vent system on pool swell loads.

The first item, downcomer condensation oscillation loads, lacked an acceptable load definition. The remaining three items had acceptable specifications; however, NRC requested additional confirmatory information to justify the adequacy of the load specifications.

This supplement addresses the resolution of the four issues listed above. In response to NRC concerns expressed in NUREG-0661, the Mark I Owners Group
conducted additional experimental and analytical studies.

The experimental studies consisted basically of two additional condensation oscillation tests in the Full-Scale Test Facility (Norco, California). The staff has reviewed these efforts and has concluded that all technical issues connected with the generic Mark I Long-Term Program have been resolved.

INTRODUCTION AND SUMMARY

The suppression pool hydrodynamic loads associated with a postulated loss-of-coolant accident (LOCA) were first identified during large-scale testing of an advanced design pressure-suppression containment (Mark III).

These additional loads, which had not explicitly been included in the original Mark I containment design, result from the dynamic effects of drywell air and steam being rapidly forced into the suppression pool (torus).

Because these hydrodynamic loads had not been considered in the original design of the Mark I containment, a detailed reevaluation of the Mark I containment system was required.

The historical development of the bases for the original Mark I design as well as a summary of the two-part overall program (i.e., Short-Term and Long-Term Programs) used to resolve these issues is in Section 1 of NUREG-0661, “The Safety Evaluation Report Mark I Long-Term Program” (SER) (Ref. 1).

Reference 2 describes the staff’s evaluation of the Short-Term Program (STP) used to verify that licensed Mark I facilities could continue to operate safely while the Long-Term Program (LTP) was being conducted.

The objectives of the LTP were to establish design-basis (conservative) loads that are appropriate for the anticipated life of each Mark I boiling water
reactor (BWR) facility (40 years) and to restore the originally intended design-safety margins for each Mark I containment system.

The principal thrust of the LTP has been the development of generic methods for the definition of suppression pool hydrodynamic loadings and the associated structural assessment techniques for the Mark I configuration. The generic aspects of the Mark I Owners Group LTP were completed with the submittal of “Mark I Containment Program Load Definition Report” (Ref. 3), hereafter referred to as LDR, and “Mark I Containment Program Structural Acceptance Guide” (Ref. 4), hereafter referred to as the PUAAG, as well as supporting reports on the LTP experimental and analytical tasks.

The Mark I containment LTP SER (Ref. 1) presented the staff’s review of the generic suppression pool hydrodynamic load definition and structural assessment techniques proposed in the reports cited above.

On the basis of the review of the experimental and analytical programs conducted by the Mark I Owners Group, the staff has concluded that, with one exception, the proposed suppression pool hydrodynamic load definition procedures, as modified by the NRC Acceptance Criteria in Appendix A of Reference 1, will provide a conservative estimate of these loading conditions.

The exception is the lack of an acceptable specification for the downcomer condensation oscillation loads. In addition, the staff requested confirmatory programs to justify the adequacy of the load specifications in the following three areas:

(1) adequacy of the data base for specifying torus wall pressures during condensation oscillations,
(2) possibility of asymmetric torus loading during condensation oscillations, and
(3) effect of fluid compressibility in the vent system on pool-swell loads.

This report supplements the Mark I SER (NUREG-0661) by addressing the outstanding issues relating to the Mark I containment LTP, namely the downcomer condensation oscillation load definition and the confirmatory analyses and test programs that are intended to justify the adequacy of the load specifications.

A discussion of these issues can be found in Reference 1, as shown in Table 1.

Also shown in Table . are the sections of this report where the supplemental reviews of these items are discussed.

Based on the above reviews, the staff has concluded that the improved load definition submitted by the Mark I Owners Group for downcomer condensation
oscillation loads is acceptable.

In addition, the staff has concluded that the load specification associated with the confirmatory experimental and analytical programs has been justified. Thus, the staff has concluded that the outstanding issues relating to the Mark I containment LTP have been resolved.

Previous Article

COMMUNITY MANAGEMENT OF LOW DOSE RADIOLOGICAL EVENTS

Next Article

March 15th, 2011 – Significant corrosion of the Oyster Creek torus in 1980s

Leave a Reply